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E. coli stcains isolated from patients with urinary tcact infecrions (UTn very often possess mannose"sensitive (MS) and mannose-resistant (MR) adherence facmrs (fimbriae). According to their receptor specificity the mannose-resistant adhesins can be divided inm several types, P, S, M and X. We have cloned rhe determinants of rhree groups of UTI E. coli adhesins, MS, p and S, and prepared specific aorisera against the fimbriae antigens. 189 hernagglutination (HA+) -positive stcains, 96 fecal isolates and 93 strains isoJated from UTI . have been tesred with rhese specific antisera and further characterized by receptor specific : HA, HA parteras and further of rhe "common 0 serogroups" 01, 02, 04, 06, 07, 08, 018, ' 025, 075, most prevalenr in UTI, and hemolysin production. · 68 (73 %) of the UTI srrains a.nd 50 (52%) of the fecal isolates showed P-receptor specificiry; 16 (17%) of the uropathogenic bacteria and 33 (34%) of the fecal strains exhibited S, M or X-fimbriae antigens. 24% of rhe P-hemagglutinating (P+) strains reacted wirb P (F8)-specific antiserum. In contrast, more than three quaner of the s+-srrains were agglutinated by S-specific antiserum. HA-pattern VJ and 018 amigen were found to be associared with P-fimbriae strains, wbereas HA-pattern V and VII and the 0 anrigens 02 (M-type), 06 and 018 (5-type) occurred most frequently in p- -strains. A high percentage of P-fimbriated strains showed mannose-sensitive hemagglurination and hemolysin production.
Role of alpha-Hemolysin for the in vitro Phagocytosis and intracellular killing of Escherichia coli
(1989)
The_role of a-hemolysin for the elimination of Eschericbia coli by phagocyres in vitro was investigated using sets of isogenic strains which included wild-type a -hemolyric srrains, derived strains with a reduced production of a-hemolysin and derived nonhemolytic strains. Phagocyrosis and intracellular killing of the bacteria by human blood granulocytes or monocytes were measured using growth inhibition rechniques. a-hemolytic strains were phagocytosed and killed ro a Jesser extent than isogenic strains with a reduced production of o:hemoJysin and isogenic nonhemolytic strains. The results obrained with granulocyres were similar to rhose obtained with monocyres although the elimination of bacteria by monocytes was less than that by granulocytes. These resulcs strongJy suggest that production of ahemolysin is a means by which E. coli counteracrs the activity of phagocytes by injuring these cells with the toxin.
Isolation and characterization of coliphage Omega18A specific for Escherichia coli O18ac strains
(1987)
The bactedophage Q18A, specific for Escherichia coli 018ac srrains, was isolated frorn sewage. The results of host range and conjugation experiments showed that the sensitivity of bacteria to the phage is associated with rhe presence of 018ac antigens. With sorne of rhe 018 strains rhe phage Q18A produces clear Iysis on bacterial lawns only when applied at a high multiplicity and moreover the phage does not multiply. With rhe help of the phage Ql8A, E. coli 0 18ac strains could be divided inro rwo serologically clistinct subgroups called 018A and 018A1• E. coli strains belanging to the sugroup 0 ISAare sensitive to phage Q t8A wheteas bacteria of subgroup A1 are resistanr.
The sexual phase of Plasmodium falciparum begins with the differentiation of intraerythrocytic sexual stages, termed gametocytes, in the human host. Mature gametocytes circulate in the peripheral blood and are taken up by the mosquito during the blood meal. These stages are essential for the spread of the malaria disease and form gametes in the mosquito midgut within minutes. A highly conserved family of six secreted proteins has been identified in Plasmodium falciparum. They comprise multiple adhesive domains and are termed PfCCp1 through PfCCp5, and PfFNPA. It was revealed in this work that PfCCp multi-domain adhesion proteins form protein complexes in gametocytes and on the surface of newly emerged macrogametes by adhesion domain-mediated binding. Co-Immunoprecipitation assays with activated gametocyte lysates show interactions between PfCCp proteins and indicate surface association via Pfs230 and Pfs25. Pfs230 is connected with the plasma membrane of the parasite by its interaction partner Pfs48/45. This protein is linked to the plasma membrane by a GPI anchor and presumably retains the multi-protein complex on the surface of newly emerged macrogametes in the mosquito midgut. A WD40 domain containing protein was identified to be part of this protein complex. It might serve as platform for the assembly of the multi protein complex or mediate the interplay among proteins, as suggested from known functions of the WD40 domain repeats. During egress from the host erythrocyte, the emerging gametes become vulnerable to factors of the human complement, which is taken up with the blood meal. In this thesis it was found that the complement system is active for about one hour post feeding. Macrogametes defend against complement-mediated lysis by co-opting the human complement regulators Factor H and FHL-1 from the blood-meal. These serum proteins bind via its SCR domains 5-7 to the surface of macrogametes. Once bound, they trigger complement inactivation of the alternative pathway, which prevents induction of complement lysis on the surface of the malaria parasite. Antibodies against Factor H are able to impair the sexual development in vitro and are able to block transmission to the mosquito. Interaction studies on endogenous proteins and immobilized recombinant proteins revealed the PfGAP50 protein as binding partner of Factor H and FHL-1. This protein was hitherto described as a glideosome-associated protein in invasive parasite stages, but has not yet been characterized in gametes. First localization studies indicate a relocation of PfGAP50 from the inner membrane complex to the surface of macrogametes. Malaria still persists as one of the deadliest infectious diseases worldwide. Investigations on the essential transmissive stages, gametocytes and gametes of Plasmodium falciparum, stood in the background of research for a long time. This work deciphered details on protein interactions on the surface of the malaria parasite and provides first information about coactions between the parasite and the human complement in the mosquito midgut.
While beneficial sponge-microbe associations have received much attention in recent years, less effort has been undertaken to investigate the interactions of sponges with potentially pathogenic microorganisms. Thus, the aim of this study was to examine two selected Caribbean disease conditions, termed “Sponge Orange Band” and “Sponge White Patch”, via ecological and molecular methods. Sponge Orange Band (SOB) disease affects the prominent Caribbean barrel sponge Xestospongia muta that is counted among the high-microbial-abundance (HMA) sponges, whereas Sponge White Patch (SWP) disease affects the abundant rope sponge Amphimedon compressa that belongs to the low-microbial-abundance (LMA) sponges. I have documented for both Caribbean sponge diseases a disease progression going along with massive tissue destruction as well as loss of the characteristic microbial signatures. Even though new bacteria were shown to colonize the bleached areas, the infection trials revealed in both cases no indication for the involvement of a microbial pathogen as an etiologic agent of disease leaving us still in the dark about the cause of Sponge Orange Band as well as Sponge White Patch disease.
The probiotic Escherichia coli strain Nissle 1917 (EcN) is one of the few probiotics licensed as a medication in several countries. Best documented is its effectiveness in keeping patients suffering from ulcerative colitis (UC) in remission. This might be due to its ability to induce the production of human beta defensin 2 (HBD2) in a flagellin-dependent way in intestinal epithelial cells. In contrast to ulcerative colitis, for Crohn´s disease (CD) convincing evidence is lacking that EcN might be clinically effective, most likely due to the genetically based inability of sufficient defensin production in CD patients. As a first step in the development of an alternative approach for the treatment of CD patients, EcN strains were constructed which were able to produce human alpha-defensin 5 (HD5) or beta-defensin 2 (HBD2). For that purpose codon-optimized defensin genes encoding either the proform with the signal sequence or the mature form of human alpha defensin 5 (HD5) or the gene encoding HBD2 with or without the signal sequence were cloned in an expression vector plasmid under the control of the T7 promoter. Synthesis of the encoded defensins was shown by Western blots after induction of expression and lysis of the recombinant EcN strains. Recombinant mature HBD2 with an N-terminal His-tag could be purified by Ni-column chromatography and showed antimicrobial activity against E. coli, Salmonella enterica serovar Typhimurium and Listeria monocytogenes. In a second approach, that part of the HBD2-gene which encodes mature HBD2 was fused with yebF gene. The resulting fusion protein YebFMHBD2 was secreted from the encoding EcN mutant strain after induction of expression. Presence of YebFMHBD2 in the medium was not the result of leakage from the bacterial cells, as demonstrated in the spent culture supernatant by Western blots specific for ß-galactosidase and maltose-binding protein. The dialyzed and concentrated culture supernatant inhibited the growth of E. coli, Salmonella enterica serovar Typhimurium and Listeria monocytogenes in radial diffusion assays as well as in liquid coculture. This demonstrates EcN to be a suitable probiotic E. coli strain for the production of certain defensins.
Malaria and HIV are among the most important global health problems of our time and together are responsible for approximately 3 million deaths annually. These two diseases overlap in many regions of the world including sub-Saharan Africa, Southeast Asia and South America, leading to a higher risk of co-infection. In this study, we generated and characterized hybrid molecules to target P. falciparum and HIV simultaneously for a potential HIV/malaria combination therapy. Hybrid molecules were synthesized by covalent fusion between azidothymidine (AZT) and dihydroartemisinin (DHA), tetraoxane or chloroquine (CQ); and a small library was generated and tested for antiviral and antimalarial activity. Our data suggest that dihyate is the most potent molecule in vitro, with antiplasmodial activity comparable to that of DHA (IC50 = 26 nM, SI > 3000), a moderate activity against HIV (IC50 = 2.9 µM; SI > 35) and safe to HeLa cells at concentrations used in the assay (CC50 > 100 µM). Pharmacokinetic studies further revealed that dihyate is metabolically unstable and is cleaved following an O-dealkylation once in contact with cytochrome P450 enzymes. The later further explains the uneffectiveness of dihyate against the CQ-sensitive P. berghei N strain in mice when administered by oral route at 20 mg/kg. Here, we report on a first approach to develop antimalarial/anti-HIV hybrid molecules and future optimization efforts will aim at producing second generation hybrid molecules to improve activity against HIV as well as compound bioavailability. With the emergence of resistant parasites against all the counterpart drugs of artemisinin derivatives used in artemisinin based combination therapies (ACTs), the introduction of antibiotics in the treatment of malaria has renewed interest on the identification of antibiotics with potent antimalarial properties. In this study we also investigated the antiplasmodial potential of thiostrepton and derivatives, synthesized using combinations of tail truncation, oxidation, and addition of lipophilic thiols to the terminal dehydroamino acid. We showed that derivatives SS231 and SS234 exhibit a better antiplasmodial activity (IC50 = 1 µM SI > 59 and SI > 77 respectively) than thiostrepton (IC50 = 8.95 µM, SI = 1.7). The antiplasmodial activity of these derivatives was observed at concentrations which are not hemolytic and non-toxic to human cell lines. Thiostrepton and derivatives appeared to exhibit transmission blocking properties when administered at their IC50 or IC90 concentrations and our data also showed that they attenuate proteasome activity of Plasmodium, which resulted in an accumulation of ubiquitinated proteins after incubation with their IC80 concentrations. Our results indicate that the parasite’s proteasome could be an attractive target for therapeutic intervention. In this regard, thiostrepton derivatives are promising candidates by dually acting on two independent targets, the proteasome and the apicoplast, with the capacity to eliminate both intraerythrocytic asexual and transmission stages of the parasite. To further support our findings, we evaluated the activity of a new class of antimalarial and proteasome inhibitors namely peptidyl sulfonyl fluorides on gametocyte maturation and analogues AJ34 and AJ38 were able to completely suppress gametocytogenesis at IC50 concentrations (0.23 µM and 0.17 µM respectively) suggesting a strong transmission blocking potential. The proteasome, a major proteolytic complex, responsible for the degradation and re-cycling of non-functional proteins has been studied only indirectly in P. falciparum. In addition, an apparent proteasome-like protein with similarity to bacterial ClpQ/hslV threonine-peptidases was predicted in the parasite. Antibodies were generated against the proteasome subunits alpha type 5 (α5-SU), beta type 5 (β5-SU) and pfhslV in mice and we showed that the proteasome is expressed in both sexual and asexual blood stages of P. falciparum, where they localize in the nucleus and in the cytoplasm. However, expression of PfhslV was only observed in trophozoites and shizonts. The trafficking of the studied proteasome subunits was further investigated by generating parasites expressing GFP tagged proteins. The expression of α5-SU-GFP in transgenic parasite appeared to localize abundantly in the cytoplasm of all blood stages, and no additional information was obtained from this parasite line. In conclusion, our data highlight two new tools towards combination therapy. Hybrid molecules represent promising tools for the cure of co-infected individuals, while very potent antibiotics with a wide scope of activities could be useful in ACTs by eliminating resistant parasites and limiting transmission of both, resistances and disease.
The pathogenic yeast Candida albicans can develop resistance to the widely used antifungal agent fluconazole, which inhibits ergosterol biosynthesis, by the overexpression of genes encoding multidrug efflux pumps or ergosterol biosynthesis enzymes. Zinc cluster transcription factors play a central role in the transcriptional regulation of drug resistance. Mrr1 regulates the expression of the major facilitator MDR1, Tac1 controls the expression of the ABC transporters CDR1 and CDR2, and Upc2 regulates ergosterol biosynthesis (ERG) genes. Gain-of-function mutations in these transcription factors result in constitutive overexpression of their target genes and are responsible for fluconazole resistance in many clinical C. albicans isolates. The transcription factor Ndt80 contributes to the drug-induced upregulation of CDR1 and ERG genes and also binds to the MDR1 and CDR2 promoters, suggesting that it is an important component of all major transcriptional mechanisms of fluconazole resistance. However, we found that Ndt80 is not required for the induction of MDR1 and CDR2 expression by inducing chemicals. CDR2 was even partially derepressed in ndt80D mutants, indicating that Ndt80 is a repressor of CDR2 expression. Hyperactive forms of Mrr1, Tac1, and Upc2 promoted overexpression of MDR1, CDR1/CDR2, and ERG11, respectively, with the same efficiency in the presence and absence of Ndt80. Mrr1- and Tac1-mediated fluconazole resistance was even slightly enhanced in ndt80D mutants compared to wild-type cells. These results demonstrate that Ndt80 is dispensable for the constitutive overexpression of Mrr1, Tac1, and Upc2 target genes and the increased fluconazole resistance of strains that have acquired activating mutations in these transcription factors.
A Candidate Approach Implicates the Secreted Salmonella Effector Protein SpvB in P-Body Disassembly
(2011)
P-bodies are dynamic aggregates of RNA and proteins involved in several post-transcriptional regulation processes. Pbodies have been shown to play important roles in regulating viral infection, whereas their interplay with bacterial pathogens, specifically intracellular bacteria that extensively manipulate host cell pathways, remains unknown. Here, we report that Salmonella infection induces P-body disassembly in a cell type-specific manner, and independently of previously characterized pathways such as inhibition of host cell RNA synthesis or microRNA-mediated gene silencing. We show that the Salmonella-induced P-body disassembly depends on the activation of the SPI-2 encoded type 3 secretion system, and that the secreted effector protein SpvB plays a major role in this process. P-body disruption is also induced by the related pathogen, Shigella flexneri, arguing that this might be a new mechanism by which intracellular bacterial pathogens subvert host cell function.
Background: In principle, the elimination of malignancies by oncolytic virotherapy could proceed by different mechanisms - e.g. tumor cell specific oncolysis, destruction of the tumor vasculature or an anti-tumoral immunological response. In this study, we analyzed the contribution of these factors to elucidate the responsible mechanism for regression of human breast tumor xenografts upon colonization with an attenuated vaccinia virus (VACV). Methods: Breast tumor xenografts were analyzed 6 weeks post VACV infection (p.i.; regression phase) by immunohistochemistry and mouse-specific expression arrays. Viral-mediated oncolysis was determined by tumor growth analysis combined with microscopic studies of intratumoral virus distribution. The tumor vasculature was morphologically characterized by diameter and density measurements and vessel functionality was analyzed by lectin perfusion and extravasation studies. Immunological aspects of viral-mediated tumor regression were studied in either immune-deficient mouse strains (T-, B-, NK-cell-deficient) or upon cyclophosphamide-induced immunosuppression (MHCII+-cell depletion) in nude mice. Results: Late stage VACV-infected breast tumors showed extensive necrosis, which was highly specific to cancer cells. The tumor vasculature in infected tumor areas remained functional and the endothelial cells were not infected. However, viral colonization triggers hyperpermeability and dilatation of the tumor vessels, which resembled the activated endothelium in wounded tissue. Moreover, we demonstrated an increased expression of genes involved in leukocyte-endothelial cell interaction in VACV-infected tumors, which orchestrate perivascular inflammatory cell infiltration. The immunohistochemical analysis of infected tumors displayed intense infiltration of MHCII-positive cells and colocalization of tumor vessels with MHCII+/CD31+ vascular leukocytes. However, GI-101A tumor growth analysis upon VACV-infection in either immunosuppressed nude mice (MHCII+-cell depleted) or in immune-deficient mouse strains (T-, B-, NK-cell-deficient) revealed that neither MHCII-positive immune cells nor T-, B-, or NK cells contributed significantly to VACV-mediated tumor regression. In contrast, tumors of immunosuppressed mice showed enhanced viral spreading and tumor necrosis. Conclusions: Taken together, these results indicate that VACV-mediated oncolysis is the primary mechanism of tumor shrinkage in the late regression phase. Neither the destruction of the tumor vasculature nor the massive VACV-mediated intratumoral inflammation was a prerequisite for tumor regression. We propose that approaches to enhance viral replication and spread within the tumor microenvironment should improve therapeutical outcome.
Bacteria lose or gain genetic material and through selection, new variants become fixed in the population. Here we provide the first, genome-wide example of a single bacterial strain’s evolution in different deliberately colonized patients and the surprising insight that hosts appear to personalize their microflora. By first obtaining the complete genome sequence of the prototype asymptomatic bacteriuria strain E. coli 83972 and then resequencing its descendants after therapeutic bladder colonization of different patients, we identified 34 mutations, which affected metabolic and virulence-related genes. Further transcriptome and proteome analysis proved that these genome changes altered bacterial gene expression resulting in unique adaptation patterns in each patient. Our results provide evidence that, in addition to stochastic events, adaptive bacterial evolution is driven by individual host environments. Ongoing loss of gene function supports the hypothesis that evolution towards commensalism rather than virulence is favored during asymptomatic bladder colonization.
In leishmaniasis, macrophages are known to play a central role as modulators of the specific immune activity. In this article, Heidrun Moll presents evidence for the critical involvement of another component of the skin immune system, the epidermal Langerhans cell. She proposes that Langerhans cells take up parasites in the skin and transport them to the draining lymph node for presentation to T cells and initiation of the specific immune response.
The expression of T-cell-associated serine proteinase 1 (MTSP-1) in vivo during Leishmania major infection was analyzed in genetically resistant C57BL/6 mice and in genetically susceptible BALB/c mice. Using a monoclonal antibody as well as an RNA probe specific for MTSP-1 to stain tissue sections, we found T cells expressing MTSP-1 in skin lesions and spleens of mice of both strains. In skin lesions, MTSP-1-positive T cells could be detected as early as 3 days after infection. Most importantly, the frequency of T cells expressing MTSP-1 was significantly higher in susceptible BALB/c mice than in resistant C57BL/6 mice. These findings suggest that MTSP-1 is associated with disease-promoting T cells and that it may be an effector molecule involved in the pathogenesis of cutaneous leishmaniasis.
We have assessed the role of tumour necrosis factor-a (TNF) during cutaneous leishmaniasis and demonstrated that significant levels of TNF were released by spleen cells from infected mice after in cirro restimulation with Leishmania major promastigotes. Spleen cells from both genetically resistant and genetically susceptible mice were equally capable of producing TNF. After challenge with bacterial endotoxin, TNF activity could also be demonstrated in the serum of L. mujor-infected mice and the titres correlated with the course of cutaneous disease in susceptible and resistant mice. TNF did not exert a direct leishmanicidal effect in uitro. Furthermore, our study indicated that macrophages are the source of L. major-induced TNF activity and that its elicitation is dependent on the presence of T cells. These findings suggest that TNF acts in concert with other cytokines produced during L. major infection and that its role depends on the composition of T cell subsets and cytokines present.
Escherichia coli isolates of serotype 06: K5 are the most common causative agents of cystitis and pyelonephritis in adults. To answer the question, as to whether strains of this particular serotype represent one special clonal group, out of a collection of 34 serotype 06: K5 isolates [Zingler et al. ( 1990) Zentralbl. Bakteriol Mikrobiol Hyg [A] 274:372-381] 15 strains were selected andanalyzed in detail. The flagellar (H) antigen and the outer membrane protein (OMP) pattern were determined. Furtherserum resistance properties and the genetic presence and expression of other virulence factors, including hemolysin, aerobactin, P fimbriae, S/F1C fimbriae and type 1 fimbriae was evaluated. In~laddition the Xbalmacrorestriction pattern of ten representative isolates was elaborated and the fimbrial (F) antigentype ofthe P fimbriae was determined, to obtain the complete 0: K: H: F pattern. These analyses could clearly show that the 06: K5 isolates do not represent one clonal group. The Xbal-macrorestriction profiles were heterogeneaus and marked differences in the hybridization patterns, using virulenceassociated gene probes in Southern hybridization of long-range-separated genomic DNA, were observed among the strains. However, some of strains showed similarities in the genomic profiles, arguing for clonal groupings among the 06: K5 isolates. lnterstingly the strains grouped tagether exhibited the same fimbrial F typethat many indicate a coincidence of this phenotypic trait with clonality.
S fimbrial adbesins (Sfa), which are able to recognize sialic acid-containing receptors on eukaryotic cells, are produced by Escherichia coli strains causing urinary tract infections or newbom meningitis. We recently described tbe cloning and molecular cbaracterization of a determinant, termed sftJI, from the chromosome of an E. coli urinary tract infection strain. Herewe present data conceming a S fimbria-specific gene duster, designated sfall, of an E. coli newbom meningitis strain. Like tbe Sfal complex, Sfall consists of tbe major subunit protein SfaA (16 kDa) and the minor subunit proteins SfaG (17 kDa), SfaS (15 kDa), and SfaH (29 kDa). The genes encoding tbe subunit proteins of Sfall were identified and sequenced. Their protein sequences were calculated from the DNA sequences and compared with tbose of the Sfal complex subunits. Altbough the sequences ofthe two major SfaA subunits ditf'ered markedly, tbe sequences ofthe minor subunits sbowed only a few amino acid exchanges (SfaG, SfaH) or were completely identical (SfaS). The introduction of a site-specific mutation into the gene sfaSII and subsequent analysis of an SfaS-negative clone indicated that sfaSII codes for the sialic acid-specific adhesin of tbe meninigitis isolate. These data were confirmed by tbe isolation and characterization of tbe SfaSII protein and the determination of its N-terminal amino acid sequence. The identity between the sialic acid-specific adhesins of Sfal and Sfall revealed that difl'erences between the two Sfa complexes with respect to tbeir capacities to agglutinate erythrocytes must result from sequence alterations of subunit proteins other tban SfaS.
The sfa determinant codes for S fimbrial adhesins which constitute adherence factors of pathogenic Escherichia coli strains. Wehave recently shown that the sfa determinant is transcribed from three prömoters, pA, pB, and pC. In comparison with the promoters pB and pC, promoter pA, which is located in front of the structural gene sfaA, showed very weak activity. Herewe have determined the exact positions ofthe mRNA start points by primer extension studies. We have also shown that mRNAs of 500, 700 and 1400 bases can be detected using oligonucleotide probes specific for the genes sfaB, sfaC and sfaA. SfaB and SfaC arepositive regulators infiuencing fimbriation and the production of the S-specific adhesin which is encoded by the gene sfaS Iocated in the distal half of the determinant. In addition, it is demonstrated that SfaB and SfaC interfere with the regulatory effect of the histone-like protein H-NS, encoded by a locus termed drdX or osmZ. In a drdx+ strain the regulators are necessary for transcription of the sfa determinant. In contrast, sfa expression is activator-independent in a drdx- strain. In this latter genetic background, a substantial fraction of the sfa transcripts is initiated from promoter pA. On the basis of these data we discuss a model for the regulation of this adhesin-specific determinant.
S-fimbriae mediated adhesin of Escherichia coli to human buccal epithelial cells is age independent
(1992)
S-fimbriated Escherichia coli, which cause sepsis and meningitis in the newbom, bind to sialic acid-containing glycoprotein structures on the surface of human buccal epithelial cells. The dependence of · this binding on host age was examined. S-fimbriated · E. coli adhered in comparable numbers to cells in newborns, infants, children and adults (23.0 ± 8.6; 23.1 ± 11.5; 24.7 ± 7.9; 28.9 ± 8.8). Thus, the increased susceptibility of neonates to infections caused by S-fimbriated E. coli cannot be explained by enhanced · adhesion to epithelial cells
A hospital warm water system was monitored for the prcsence and distribution of lcgionellac. Subtyping of ten scletled Legionella pneumophiltl isolates. originating from four different sites in the system by using serogroup spccific antisera in an indircct immunofluorcscence tcst, rcvcalcd that nine of the tcn isolatcs belonged to scrogroup 6, while the remaining one was serogroup I 0. Two monoclonal antibodics (mAbs) spccific for a subgroup of serogroup 6 strains were further used for characterization. None of the strains reactcd with these mAbs. Genome analysis by elaborating Not I profiles using the pulscd field gel electrophoresis (PFGE) technique revealed that nearly all serogroup 6 isolates dcrived from different sites, including a new building connected hy a ring pipe. wcrc identical according to restriction fragment pattems. The patterns were distinguishable from those of the two L. pnewnophi/a serogroup 6 rcfcrencc strains, and ftom that of thc L. pneumophila scrogroup 10 isolate. These data arguc for a relatively homogeneaus L. pneunwpltila serogroup 6 population in the entire watcr system.
Thirtccn StttJ1hylococcus dw·eus and s: <'pid<'l'· midis strains ohtaincd from nnsc and hand nf twn cmployccs and onc paticnt uf a mcdical ward as weil as two S. hemol.\"licus strains wcrc analyscd according to thcir rcstrktion fmgmcnt lcngth pattcrns ( RFLP) hy pulscd-ficld gcl clcctrophorcsis (PFGE) using thc rcslriction cnzymcs SmaJ and s.. .· tll. Spccics idcntification nf thc isolatcs was pcrformcd hy a systcm which includcs :!O hiochcmical rc"ctions. Furthcrmorc. thc antillintic resistancc pattcrns of thc stmins wcrc dctcrmincd. Whilc scvcral isolatcs cxhihitcd idcnticaf antihiotic susccptihilitics and hiochcmical prnfilcs. diffcrences in thc RFLP wcrc ohtaincd. ln thrcc cascs, S. epidermülis strains colonizing thc skin showcd an idcntical rcstriction profilc as isollltcs from thc mucous mcmhrancs of thc samc pcrson. Wc C(mcludcd that thc analysis of staphylococcal strains hy PFGE is an important cpidcmiolngical tnnl with high discrimination power.
We investigated the ability of meconium, feces from human milk-fed (HMF) newborns, and feces from formula-fed (FF) newborns to inhibit adhesion of S-fimbriated E. coli to human buccal epithelial cells. S-fimbriae are a common property of E.·coli strains causing sepsis and meningitis in neonates. Meconium had the highest content of neuraminic acid and the strongest inhibitory effect on bacterial adhesion. HMF also exerted high inhibitory activity while FF was markedly less active: To achieve inhibitory effects comparable to HMF a sixfold amount of FF was required. Glycoproteins from excretions were separated by gel chromatography. Fractions obtained were analyzed for adhesion-inhibiting activity. In all excretions analyzed, the mucin-containing fraction could be identified as the major inhibitory component. Inhibition was probably mediated by specific interaction of this fraction with S-fimbriae, as shown by binding of isolated fimbriae on Western blots after electrophoretic separation of glycoproteins. In conclusion, our data support the view that the mucin-containing fraction from meconium and human milk exerts antibacterial functions by preventing adhesin-mediated binding of pathogenic bacteria to mucosal epithelia. Key Words: S-fimbriated E. coli-Inhibition of adhesion-Meconium- Feces of human milk-fed newborns-Feces of formula-fed newborns-Mucins.
A total of 36 Escherichia coli urinary tract isolates (UTI) of serotype 06, with different combinations of capsule ( K) and flagellin ( H) antigens, were analysed according to the outer membrane pattern (OMP), serum resistance properties, mannose-resistant hemagglutination using various types of erythrocytes, and also for the genetic presence and the expression of Pfimbriae. S fimbriae/F1 C fimbriae, Type 1 fimbriae, aerobactin and hemolysin. Twenty selected strains were further analysed by pulsed field gel electrophoresis (PFGE), elaborating genomic profilas by Xba I cleavage and subsequent Southern hybridization to virulence-associated DNA probes. lt could be shown that 06 UTI isolates represent a highly heterogeneaus group of strains according to the occurrence and combination of these traits. Relatedness an the genetic and the phenotypic Ievei was found for some of the strains exhibiting the same 0: K: H: F serotype. DNA Iang-range mapping further indicated some interesting features, according to the copy number and the genomic linkage of virulence genes.
We investigated the presence of factors in human milkthat inhibit Invasion of pathogenic bacteria. The efl'ect of human milk fat globule membrane (HMFGM) components on adhesion of cloned S-fimbriated Escherichia coli to human buccal epithelial cells was analyzed. S fimbriae are a common feature of E. coli strains causing sepsis and meningitis in newborns and are bound to epithelia via sialyl-(a-2-3)galactoside structures. Human milk fat globules (HMFG) could be agglutinated by the above-mentioned bacteria. Agglutination could be inhibited by fetuin, human glycophorin, and a 1-acid glycoprotein. In addition, pretreatment of HMFG with Jlibrio cholerae neuraminidase markedly reduced bacterium-induced agglutinations, indicating the involvement of neuraminic acid-containing glycoproteins. In contrast, Iipid droplets of infant formula or artificiallipid emulsions (Intralipid) could not be agglutinated. HMFG were present in stools of breast-fed neonates as shown by indirect immunofluorescence staining with a monoclonal antibody directed against carbohydrate residues present on HMFGM. These HMFG could be agglutinated by bacteria. HMFG inhibited E. coli adhesion to buccal epithelial cells. To further characterize relevant E. coli binding structures, HMFGM components w~re separated by gel chromatography. The mucin fraction showed the most pronounced inhibitory efrect on adhesion of S-fimbriated E. coli to human buccal epithelial cells. Our data soggest that HMFG inhibit bacterial adhesion in the entire intestine and thereby may provide protection against bacterial infection.
Mip protein of Legionella pneumophila exhibits peptidyl-prolyl cis-trans-isomerase (PPIase) activity
(1992)
Legfonells pneumoph/la is an intracellular paraslte which ts able to survtve and multipJy in human monocytes and alveolar macrophages. The Mtp (macrophage lnfectiv1ty potentlator) protein has been shown to be an essential virulente factor. A search of translated nuclelt .acld data ba.ses has shown that the Mip proteJn from strain Wadsworth possesses reglons homologaus to those found in the FK.506-bindfng proteins (FKBPs) of several different eukaryotlc organisms. FKBPs are abte to bind to the fmmunosuppressant macrollde FK506 and possess peptidyf .. prolyl cisltrans Isomerase (PPiase) activlty. The gene coding for the Mlp proteln was cloned from the ehromo. some of L. pneumophila straln Philadelph·a I and sequenced. II was synthesl%ed in Escherichla coll ·K- 12 and alter purlfication it exhibited PPiase activity catalyslng the slow clsltrans lsomerization of prolyl peptlde bonds. ln ollgopeptides. Mip ls inhibi~ted by FK506 and fully reslstant to cyclosporln A, as was also found for the recently characterlzed FKBP-type PPiases of eukaryotes. However, the N-terminal extenslon of Mip and/or the substltutrons of the vari· ab1e amlno acrds ln the C-termlnal FKBP core Iead to variatlons,. when compared with eukaryotlc FKBPs, Jn substrate specfflclty wlth the Oligopeptide substrates of' type Suc-Aia-Xaa-Pro-Phe·4·nitroanUide. Never· theless, the Legionella Mip factor represents a bacte· rial gene product whtch shares some characteristics normally found in eukaryotic proteins. ln view of the activity of PPiases in protein-folding reactlonsf such prokaryotic FKBP analogues may represent a new class of bacterial. pathogenicity factors.
The protein PpiA (19 kD) cloned from a genomic library of Legionella pneumophila, Philadelphia 1, represents a peptido-glycan associated outer membrane protein in recombinant E. coli K-12 and L. pneumophila. lt exhibits distinct sequence homology to Iipoproteins of Haemophilus influenzae and E. coli. A ppiA specific DNA probe generated by PCR was used in Southern hybridizations of chromosomal DNA of Legionella strains and other Gram-negative pathogens. Under conditions of high stringency, hybridization could only be observed in L. pneumophila isolates, but alt other Legionella strains tested displayed hybridization under lower stringency. No signals appeared after hybridization of chromosomal DNA from a variety of other bacteria. Using anti-PpiA monospecific polyclonal antibodies in Western blots, it was demonstrated that PpiA related proteins of nearly the same size are found in all L. pneumophila isolates and in a variety of, but not alt, the Legionella species analysed here.
Legionel/a pneumophila, the causative agent of Legionnaires' disease, was analysed by electron microscopy for production of surface structures. Crystalline surface (S-) layers and fimbriae were not detected, but monotrichous flagellation was seen. Polyclonal antibodies specific for the 47 kDa ftagellin subunit of L. pneumophila Philadelphia I were used in Western blots to confirm the presence of flagella subunits in various L. pneumophila strains tested, but the antiserumalso reacted with flagellin subunits of L. micdlulei, L. hackelia (serogroup (SG) l and SG21 and L./ongbetichae (SG2). Flagellation of Legionellae was shown to be temperature regulated. When the growth temperature of virulent and avirulent variants of strain L. pneumophila Philadelphia I was shifted from 30 oc to either 37 or 41 oc, a decrease in the percentage offtagellated bacteria within the populationwas observed.
The legiolysin gene (lly) cloned from Legionella pneumophila Philadelphia 1 confers the phenotypes of hemolysis and browning of the culture medium. An internal Uy-specific DNA probe was used in Southern hybridizations for the detection of Uy-specific DNA in the genomes of legioneUae and other gram-negative pathogenic bacteria. Under conditi9ns of high stringency, tlie Uy DNA probe specifically reacted with DNA fragments fr9m L. pneumophiüz isolates; by reducing stringency, hybridization was also observed for all other Legionella strains tested. No hybridization occurred with DNAs isolated from bact~ria of other genera. The Uy genewas mapped by pulsed-field gel electrophoresis to the respective genomic Notl fragments of Legionelltz isolates. By using antilegiolysin monospecific polyclonal antibodies in Western blots (immunoblots), Lly proteins could be detected only in L. pneumophila isolates.
A total of 127 extraintestinal Escherichia coli strains of the capsule serotypes Kl, KS, and KlOO from human and animal sources were analyzed for DNA sequences specific for the genes for various adhesins (P fimbriae fpap] and P-related sequences fprs], S fimbriae [s/a)/FlC fimbriae [foc], and type I fimbriae lfim]), aerobactin (aer), and hemolysin (hly). The expression of corresponding virulence factors was also tested. Twenty-four selected strains were analyzed by long-range DNA mapping to evaluate their genetic relationships. DNA sequences for the adhesins were often found in strains not expressing them, while strains with hemolysin and aerobactin genes usually did express them. Different isolates of the same serotype orten expressed different virulence patterns. The use of virulence-associated gene probes for Southern hybridization with genomic DNA fragments separated by pulsed-field gel electrophoresis revealed that a highly heterogeneous restriction fragment length and hybridization pattern existed even within strains of the same serotype. Long-range DNA mapping is therefore useful for the evaluation of genetic relatedness among individual isolates and facilitates the performance of .precise molecular epidemiology.
A genomic library of Legionello pneumophihz, the causative agent of Legionnaires disease in humans, was constructed in Escherichill coli K-12, and the recombinant clones were screened by immuno-colony blots with im antiserum raised against heat-killed L. pneumophilo. Twenty-three clones coding for a LegioneUa-specific protein of 19 kDa were isolated. The 19-kDa protein, which represents an outer membrane protein, was found tobe associated with the peptidoglycan layer bothin L. pneumophilo andin the recombinant E. coli clones. This was shown by electrophoresis and Western immunoblot analysis of bacterial cell membrane fractions witb a monospecific polyclonal 19-kDa protein-specific antiserum. Tbe protein was termed peptidoglycan-associated protein of L. pneumophilo (Ppl). The corresponding genetic determinant, ppl, was subcloned on a 1.8-kb Clol fragment. DNA sequence studies revealed that two open reading frames, pplA and pplB, coding for putative proteins of 18~9 and 16.8 kDa, respectively, were located on the Clol fragment. Exonuclease 111 digestion studies confirmed tbat pplA is the gene coding for the peptidoglycan.;.associated 19-kDa protein of L. pneumophilo. The amino acid sequence of PpiA exhibits a high degree of homology to the sequences of the Pal Iipoproteins of E. coli K-12 and liaemophilus injluenvze.
A total of 16 Escherichia coli 06 strains isolated from cases of extraintestinal infections were analysed for the genetic presence and phenotypic expression of fimbrial adhesins ( P, S/FIC, type I), aerobactin and hemolysin. ln addition restriction fragment length polymorphisms (RFLPs) of Xbal-cleaved genomic DNA of seven selected strains, separated by orthogonal field alternation gel electrophoresis {OFAGE) were determined and virulence-associated DNA probes were used for Southern hybridization studies of the Xbal-cleaved genomic DNAs. The virulence characteristics and hybridization patterns obtained differed between the various isolates. ln three isolates hemolysin genes and P fimbrial determinants were located on the same Xbal fragments. Furthermore, multiple copies of FIC determinants (foc) could be detected in two strains. Our data show that the new technique of pulse field electrophoresis tagether with Southern hybridization represents a powerful tool for the genetic analysis of pathogenic bacteria.
The uropathogenic Escherichia coli wiJd..:type strain 536 produces S-fimbriae, P-related fimbriae and type I fimbriae. Using immuno-colony dot and ELISA techniques, variants were detected showing an increased degree of S-fimbrial production. It was demonstrated by itrtmunofluorescence microscopy that in noimal (wild-type) and hyperS- fimbriated E. coli populaiions non-fimbriated cells also · exist, and that the percentage of Sfinibrlated and non-fimbriated bacteria was roughly identica1 in either population. Hyper-Sfimbriated variants could be stably maintained. The transition from wild-type to hyper-S-fimbriation, which occurs spontaneously, is markedly higher than vice versa. Southern blot analysis of the S fimbrial adhesin (sfa) determinants of normal and hyper-fimbriated strains revealed no marked difference in the gene structure.
Legionella pneumophila, the causative agent of Legionnaires' disease is able to live and multiply within macrophages as weil as within protozoan organisms. Legionella strains inhibit phagosome-lysosome fusion and phagosome acidification. By using two different cell culture systems, one derived from human macrophages and the other from human.embryo lung fibro:blastic cells, it is demonstrated that Legionella strains lose their virulence following cultivation in the laboratory. In order to study the mechanisms involved in intracellular survival of Legionella a genomic library of strain Legionella pneumophila Philadelphia I was established in Escherichia coli K-12. By cosmid cloning technique we were able to clone five putative virulence factors, two of which exhibit hemolytic activities and three of which represent membrane-associated proteins of 19, 26 and 60 kilodalton. One of the hemolytic proteins, termed legiolysin, represents a new toxin which specifically lyses human erythrocytes. The other hemolysin exhibits proteolytic properties in addition and is cytolytic for Vero and CHO cells. Further sturlies will be necessary to determine the exact role of the cloned proteins in the pathogenesis of Legionella. Zusammenfassung: Intrazelluläres Überleben
Ten Legionella pneumophUa strains isolated from dift'erent sources were analyzed according to their restriction fragment patterils obtained by cle~vage of gen.omic DNA With Notl and Sftl and separation by pulsed field electrophoresis. Three L. pneumophila isolate~ from a nosocomial outbreak in Lü~k (Germany) and three other L. prreumophilll stralns independently isolated from a water tap located in the care unit where tbe patients were bospitalized 'xhibited identical restricti9n fragment profiles. Therefore, we concluded that these environment81 spee~ens were the source of the Legionnatres dlsease. Anotber two isolates from patients and two strains from the environment, all unrelated to the outJlreak described, sbowed different cleavage patterns.
The S fimbrial adhesin (sfa) determinant of E. co/i comprises nine genes situated on a stretch of 7.9 kilobases (kb) DNA. Here the nucleotide sequence of the genes sfa B and sfaC situated proximal to the main structural gene sfaA is described. Sfa-LacZ fusions show that the two genes are transcribed in opposite directions. The isolation of mutants in the proximal region of the sfa gene cluster, the construction of sfa-phoA gene fusions and subsequent transcomplementation sturlies indicated that the genes sfaB and sfaC play a role in regulation of the sfa determinant. ln addition the nucleotide sequence of the genes sfa D, sfa E and sfa F situated between the genes sfaA and sfaG responsible for S subunit proteins, were determined. lt is suggested that these genes are involved in transport and assembly of fimbrial subunits. Thus the entire genetic organization of the sfa determinant is presented and compared with the gene clusters coding for P fimbriae (pap), F1 C fimbriae (foc) and type I fimbriae ( fim). The evolutionary relationship of fimbrial adhesin determinants is discussed.
Genome analysis of Legionella spp. by orthogonal field alternation gel electrophoresis (OFAGE)
(1990)
Various Legionella isolates from different sources and origins were analysed by orthogonal field alternation gel electrophoresis of Not I cleaved genomic DNA. The genome of L pneumophila Philadelphia I, the original isolate of the epidemics in 1976, exhibits only five Not I fragments. Two virulent derivatives. derived from L pneumophila Philadelphia I. which were obtained by prolonged passage on artificial cuhure media, did not differ from their isogenic virulent strain according the Not I fragment pattern. By summing the lengths of the Notl fragments, the genome size of L. pneumophila Philadelphia I was calculated as approximately 3.9 Mb. Environmental L pneumophila strains exhibited different Not I pattems, as did Legionella strains not belongi'ng to the species pneumophila. The usefulness of DNA long range mapping of Legionella ssp. with Notl for epidemiology and evaluation of their evolutionary rela· tionships is discussed.
Escherichia coU K-12 strains producing S-fimbrial adhesins, FlC fimbriae, and mutagenized fimbriae were tested in a binding assay with a renal tubular cell line. S-fimbrial adhesins and FlC fimbriae mediated bindlog to tubular cells. The SfaA, SfaG, and SfaS subunits of S fimbriae contributed to attachment. Site-specific mutations in the sfaS gene reduced binding. The Inhibitionprofile of FlC fimbriae resembled that of S fimbriae.
We investigated the roJe of Escherichia coU expressing mannose-resistant hemagglutination and adhesins with regard to the induction of leukotrienes from a suspension of human lymphocytes, monocytes, and basophils (LMBs) compared with human polymorphonuclear granulocytes (PMNs). Genetically cloned E. coli strains expressing various types of mannose-resistant hemagglutination (MRH+) were phagocytosed to a higher degree by monocytes than the nonadherent E. coli strain. The various strains dUfered in their capacity to induce a chemiluminescence response, which showed the same pattern for LMBs and PMNs. Stimulation of LMBs with bacteria alone, unlike granulocytes, did not activate the cells for the release of leukotrienes. However, preincubation of LMBs with bacteria decreased subsequent leukotriene formation when the cells were stimulated with calcium ionophore. The inhibitory eft'ect was dependent on the concentration of bacteria used for preincubation as weil as on the preincubation temperature. The various bacterial strains dift'ered in inhibitory potency for mediator release. Preincubation of LMBs with zymosan, opsonized zymosan, the bacterfal peptide FMLP, and peptidoglycan bad no inhibitory eft'ect or even increased subsequent IeukotrieDe formation. Opsonized bacteria were far less inhibitory than nonopsonized bacteria. In contrast to human LMBs, preincubation of human PMNs with mannose-resistant bacteria led to increased leukotriene 84 generation and reduced w-oxidation of leukotriene 84 • Our data soggest that phagocytes (neutrophils, monocytes) respond in a different way for leukotriene formation after Interaction with mannose-resistant E. coli.
S fimbrial adhesins (Sfa) enable pathogenic Escherichia coli strains to bind to sialic acid-containing eucaryotic receptor molecules. In order to determine the inftuence of culture conditions on the expression of the sfa determinant in a wild-type strain, we fused the gene lacZ, coding for the enzyme ß-galactosidase, to the sfaA gene, responsible for the major protein subunit of S fimbriae. By using a plasmid which carries an R6K origin, the sfaA-Iac hybrid construct was site-specifically integrated into the chromosome of the uropathogenic E. coli strain S36WT. The expression of lacZ, which was under the control of the sfa wild-type promoters, was now equivalent to the sfa expression of strain S36WT. With the help of this particular wild-type construct, it was demonstrated that the sfa determinant is better expressed on solid media than in liquid broth. The growth rate bad a strong inftuence on Sfa expression under aerobic but not under anaerobic conditions. Production of Sfa was further regulated by catabolite repression, osmolarity, and temperature.
The gene coding for the sialic acid-specific adhesin SfaS produced by the S fimbrial adhesin (sfa) determinant of Escherichia coli has been modified by oligonucleotide-directed, site-specific mutagenesis. Lysine 116, arginine 118, and Iysine 122 were replaced by threonine, serine, and threonine, respectively. The mutagenized gene dusters were able to produce S fimbrial adhesin complexes consisting of the S-specific subunit proteins including the adhesin SfaS. The mutant clones were further characterized by hemagglutination and by enzyme-linked immunoassay tests with antifimbria- and anti-adhesin-specific monoclonal antibodies, one of which is able to block S-specific binding (Moch et al., Proc. Natl. Acad. Sei. USA 84:3462-3466, 1987). The lysine-122 mutantclone was indistinguishable from the wild-type clone in these assays. Replacement of Iysine 116 and ai'ginine 118, however, abolished hemagglutination and resulted in clones which showed a weak (Iysine 116) or a negative (arginine 118) reaction with the antiadhesin-specific antibody Al. We therefore suggest that Iysine 116 and arginine 118 have an inßuence on binding of SfaS to the sialic acid residue of the receptor molecule. Substitution of arginine 118 by serine also had a negative efl"ect on the amount of SfaS adhesin proteins isolated from the S fimbrial adhesin complex.
Tbe genetic organization of tbe foc gene duster bas been studied; six genes involved in tbe biogenesis of Fl C fimbriae were identifi.ed.focA encodes tbe major fimbrial subunit, focC encodes a product tbat is indispensable for fimbria formation,focG andjocH encode minor ftmbrial subunits, andfocl encodes a protein wbicb sbows similarities to the subunit protein FocA. Apart from tbe FocA major subunits, purified FlC fimbriae contain at least two minor subunits, FocG and FocH. Minor proteins of similar size were observed in purified S fimbriae. Remarkably, some mutations in tbe foc gene duster result in an altered 6mbrial morpbology, i.e., rigid stubs or long, curly ftmbriae.
The S flmbrial adhesln (Sfa) enables Esch richla colito attach to slalfc acld-containing receptor molecules of eukaryotJc cells. As prevlously reported, the genetlc determinant coding for the Sfa of an E. co/1 06 strain was cloned, the gene codlng for the major fimbrfal subunit was ldentlfled and sequenced and th.e S speclflc adhesin was detected. Here we present evidence that ln addltlon to the major subunit proteln SfaA three other minor subunit proteins, SfaG (17 kD), SfaS (14kD) and SfaH (31 kD) can be isolated from the S..speclfic flmbrial adhesln complex. The genes coding for these minor subunits were ldenblied, mutagenlzed separately and sequenced. Using haemagglutlnatton tests. electron-microscopy and quantitative ELISA assays with monoclonal anti-SfaA and anti-SfaS antlbodles the functlons of the minor subunlts were determined. lt was determlned that SfaS ls ldentlcal to the S-specific adhesln; whlch also plays a role ln deterrninatlon of the degree of fimbri· ation ofthe cell. The mlnor subunit SfaH also had some Jnfluence on the Ievei of fimbrlation of the cell. while StaG ls necessary for full expression of S·specific binding. lt was further shown that the amino-terminal proteln sequence of the isolated SfaS profein was identJcal to the proteln sequence calculated from the DNA sequence of the sfaS gene locus.
Genetically cloned E. co/i strains expressing cloned virulence factors were studied with regard to their capability to induce inflammatory mediator release from various target cells. Among the strains were E. co/i strains with mannose-resistant haemagglutination (MRH +) and mannose-resistant adhesins, e.g. E. coli 536/21 pANN 80 I /4, E. coli 536/21 pANN 921 and E. coli 536/21 pANN 801-1. In comparison, E. coli 536/21, E. coli 536/21 pGB 30 int and E. coli Kl2, without and with mannosesensitive haemagglutination (MSH±), and adhesins were studied. The properties of the various strains for human PMN with regard to adherence and phagocytosis, chemiluminescence, 5-lipoxygenase activation of arachidonic acid, leukotriene formation, granular enzyme release and release of histamine from rat mast cells were analysed. It is evident that the various 'biochemical processes of cell activation are dissociated events. The highest chemiluminescence response is obtained with strains expressing MSH+, P-M RH+ or S-M RH+; the presence of S-adhesins suppressed the response. Highest leukotriene formation is obtained with E. coli 536/21 pANN 801-4, while E. coli with MSH was inactive. The concomitant presence of haemolysin secretion enhanced mediator release significantly. Our data suggest a potent role for mannose-resistant haemagglutination (MRH), adhesins and haemolysin as virulence factors in inducing the release of inflammatory mediators.
The avirulent Salmonella typhimurium F885 was transformed with a plasmid carrying the cloned S fimbriae genes of a uropathogenic Escherichia coli. The resulting transformant (F885-1) produced efficiently E. coli S fimbriae and was used for live oral vaccination of rats. For comparison rats were immunized subcutaneously with isolated S fimbriae. Both routes of vaccination resulted in a significant lgG antibody response to S fimbriae. In addition live oral vaccination induced a serum lgA response against S fimbriae. After transurethral infection of rats with a S fimbriae producing E. coli a 10-fold reduction of bacterial counts in the kidney was observed in rats orally vaccinated with F885-1 as compared to unvaccinated controls. This study suggests that the avirulent Salmonella F885 may be used as a fimbrial antigen carrier for oral vaccination against renal infections.
DNA hybridization experiments demonstrated that the gene clusters encoding the F8 fimbriae (fei) as well as the type I fimbriae (pi/) exist in a single copy on the chromosome of E. coli 018:K5 strain 2980. In conjugation experiments with appropriate donors, the chromosomal site of these gene clusters was determined. The pil genes were mapped close to the gene clusters thr and Jeu controlling the biosynthesis of threonine and leucine, respectively. The fei genes were found to be located close to the galactose operon (gal) between the position 17 and 21 of the E. coli chromosomallinkage map.
We analyzed an Escherichia coli strain which harbours a chromosomal mutation that blocks the hemolysin excretion. Compartmentation studies showed that hemolysin accumulates in the cytoplasm and not in the periplasm. The mutation did not affect the SDS-PAGE protein pattern of the outer membrane, although some alterations were apparent in the periplasmic protein pattern. The mutant strain, E. coli Hsb-1 also failed to export a cloned fimbrial adhesin. The mutation maps in the min. 3.5 of the E. coli genetic map.
The Escherichia coli blood culture isolate BK658 (07S:K1:H7) expresses F1A and F1B fimbriae as weil as a third fimbrial type which reacts with anti-S-fimbrial antiserum but fails to show S-specific binding properlies (i.e., agglutination of bovine erythrocytes). To characterize these fimbriae, we cloned the respective genetic determinant in E. coli K-12. The resulting recombinant clone HB101(pMMP658-6) expresses fimbriae of 1.2-p.m length and a diameter of approximately 7 nm. The determinant codes for the fimbrillin subunit, a protein of 17 kUodaltons in size, and for at least five other proteins of 87, 31, 23, 14.3, and 13.8 kUodaltons. By restriction analysis and by DNA-DNA hybridization, it could be shown that the cloned fimbrial determinant of strain BK658 exhibits a high degree of sequence homology to the gene clusters coding for S fimbrial adhesins (sfa) and F1C fimbriae (/oc). By using the Western blot (immunoblot) technique and a quantitative enzyme-linked immunosorbent assay, it could be further demonstrated that the cloned fimbriae of BK658, S fimbriae, and FlC fimbriae share cross-reactive epitopes as weil as antigenic determinants specific for each fimbrial type. No antigenic cross-reactivity with F1C fimbriae could be detected. The results indicate a genetical and serological relatedness of the cloned fimbriae toS fimbriae and F1C fimbriae. Therefore, this new type of fimbriae is preliminarily termed SIF1C-related fimbriae (Sfr).
Fimbrial 8dhesins en8ble b8cteria to 8ttach t9 eucaryotic ceU~. The genetic determin8nts for S fimbrial 8dhesins (sja) an.d for FlC ("pseudotype I") fimbri8e ifoc) were compared. Sfa and FlC represent functionally distinct 8dbesins in tbeir receptor specificities. Nevertheless, 8 high degree of bomology between both determin8nts was found on the basis of DNA-DNA hybridizations. Characteristic difl'erences in the restriCtion maps of tbe corresponding gene clusters, bowever, were visible in regions coding for the fimbrial subunits and for the S-specific 8dhesin. While a plasmid carrying the geneiic deternlinant for FlC fimbri8e was 8ble to complement transposon-induced sfa mutants, 8 plasmid carrying tbe genetic determin8nt for 8 tbird 8dht$in type, termed P fimbriae, was un8ble to do so. Proximal sfa-specific sequences carrying the S fimbrial st'"uctural gene were fused to sequences representing tbe di$tal part of the foc gene cluster to form 8 hybrid cluster, and tbe foc proxim~ region coding for tbe structural protein was Iigated to sfa distal sequences to form 8 second hybrid. Botb hybrid clones produced intact fimbriae. Anti-FlC monoclonal8ntibodies (MAbs) only recognized clones which produced FlC fimbriae, and an ~ti-S 8dhesin MAb marked clones whicb expressed the S adhesin. Bowever, one of four other anti-S fimbri8e-specific MAbs reacted witb both fimbrial structures, S and FlC, indicating 8 common epitope on both antigens. The results presented bere ~upport tbe view th8t sfa and foc determinants code for fimbri8e tb8t 8re simil8r in several aspects, wbile the P fimbri8e are members of 8 more distantly rel8ted group.
Binding sites in the rat brain for Escherichia coli S fimbriae associated with neontal meningitis
(1988)
Escherichia coli strains that cause sepsis and meningitis in neonatal infants carry S fimbriae that bind to sialyl galactoside units of cell surface glycoproteins. To investigate the possible role of S fimbriae in determining the tissue tropism of neonatal menlngitis, we have studied the preselice of binding sites for S fimbriae in different tissues of the neonatal rat which is susceptible to meningitis caused by S-fimbriated E. coli. Purified S fimbriae were incubated on cryostat sections of different rat oipns and their bindina was assessed by indirect immunofluorescence. In the bnin of the neonatal rat, S fimbriae specifically bound to the luminal surfaces of the vascular endothelium and of the epithelium lining the choroid plexuses and bnin ventricles. The · bindlog W.s completely inhibited by the trisaccharide NeuAca2-3Ga)ßl-4Gic, a receptor analogue of S fimbriae, and by a preceding neuraminidase treatment of the sections. A recombinant E. coli strain expressina S fimbriae adhered in large numbers to the same tissue sites in the neonatal brain sections as did the purified fimbriae, · whereas the nonfimbriated host strahi and a recombiiuuit strain expresslog P fi.mbriae did not adhere to brain tissues. The results soggest that adhesion of S-fimbriated bacteria to the binding sites observed in the neonatai bnin has a pathogenetic roJe durlog bacterial Invasion from cii'culation into the cerebrospinal fluid.
DNA probes specific for different regions of the S-fimbrial adhesin (sja) determinant were constructed and hybridized with DNA sequences coding for P (F8 and F13), mannose-sensitive hemagglutinating type 1 (FlA), and FlC fimbriae. While the sfa and F1C DNA determinants exhibited homology along their entire lengths, the P-fimbrial and type 1-fimbrial determinants exhibited homology to regions of the sfa duster responsible for the control of transcription and, to a minor extent, to regions coding for proteins involved in biogenesis and/or adhesion of the fimbriae and for the N-terminal part of the fimbrillin subunit.
Nucleotide sequence of the sfaA gene coding for the S fimbrial protein subunit of Escherichia coli
(1987)
The sfaA gene of the uropathogenic Escherichia coli 06 strain 536, which is responsible for the determination of the S fimbrial protein subunit, was sequenced. The structural gene codes for a polypeptide of 180 amino acids including a 24-residue N-terminal signal sequence. A size of 15.95 kDa was calculated for the processed SfaA protein. The nucleotide and deduced amino acid sequences show significant homology to those of the F1C fimbria and, to a lesser extent, of the mannose- sensitive hemagglutinating fimbria (FimA, PilA). Only week homology toP fimbriae subunits (F72 , Pap) was found.
We investigated the role of bacterial mannose-resistant fimbriation of S fimbriae (Firn), mannose-resistant hemagglutination (S-Mrh), and hemolysin (Hiy) production by an Escherichitl coli parent and genetically cloned strains as regards (i) their eß'ect on histamine release from rat mast ceUs and (ii) generation of the chemiluminescence response, leukotriene, and enzyme release from human polymorphonuclear granulocytes. These mediators are involved in the induction of inftammatory disease processes and Iead, e.g., to the enhancement of vascular permeability, chemotaxis, aggregation of granulocytes (leukotriene 8 4), lysosomal enzyme release, and smooth-muscle contraction (leukotrienes C4, D4, and E4). The content of azurophilic and specific granules in polymorphonuclear granulocytes consists of highly reactive enzymes which amplify inflammatory reactions. Washed bacteria (E. coli 764 my:t:, E. coli 21085 Hly:t:, E. coli 536 Hly:t: Firn:~: Mrh:t:), as weil as their culture supernatants, were analyzed at various times during their growth cycle. No differences exist between parent and cloned or mutant strains with respect to their outer . membrane proteins and lipopolysaccharide pattern. Washed bacteria [E. coli 764 and 21085(pANN202-312)] which produced hemolysin, unlike my- strains, induced high Ievels of histamine release from rat mast ceUs and led to a significant chemiluminescence response and enzyme and leukotriene release from human polymorphonuclear granulocytes. Bacterial culture supernatants from Hly+ and secreting strains showed similar results with the exception of E. coli 21085(pANN202-312), which is a hemolysin-producing bot not a secretory strain. Our data soggest a potent role for hernolysin as a stimulus for noncytotoxic mediator release from various cells. Furthermore, we showed that the presence of Firn and S Mrh potentiales mediator release. The simultaneous presence of Mrh and Firn [E. coli 535/2l(pANN801-4)] increased mediator release compared with Mrh+ Firn- strains [E. coli 536/21(pANN801-1)]. E. coli 536/21 (Msh- Mrh- Firn- Hly-) did not induce mediator release. Escherichia coli alpha-hemolysin is a protein that causes in vitro Iysis of erythrocytes from several species of animals (6, 12, 1~18, 23). Hemolysin-producing E. coli strains occur only infrequently in the normal fecal ftora of humans but are often isolated from patients with extraintestinal infections such as urinary tract infections, bacteremia, and septicemia (13, 22, 25, 36-38, 46-48). The high percentage of Hly+ E. coli strains among isolates from patients with urinary tract infections suggested that hemolysin contributes to the virulence of E. coli strains. The role of hemolysin as a virulence factor has been recently demonstrated by using various animal models and cell cultures. Alpha-hemolysin is one of the very few proteins produced by members of the family Enterobacteriaceae that is released extracellulary. The genetic control of alpha-hemolysin production, transport, and release from cells is complex (24, 26, 30). At least four genes located on the bacterial chromosome or on ]arge transmissible plasmids are required to elicit a cell-free hemolytic phenotype. Bobach and Snyder (6) suggested that the existence of alpha-hemolysin complexed with lipopolysaccharide may have important implications in the understanding of its biological effects. In addition to hemolysin production, a variety of factors, e.g., fimbriae, expression of specific hemagglutination, and • Corresponding author. 886 0 and K antigens, may contribute to the vi
Escherichia coli 536 (06:K15:H31), which was isolated from a case of urinary tract infection, determines high nephropathogenicity in a rat pyelonephritis system as measured by renal bacterial counts 7 days after infection. The loss of S fimbrial adhesin formation (Sfa-) (mannose-resistant hemagglutination [Mrh-] and fimbria production [Fim-]), serum resistance (Sre-), and hemolysin production (Hly-) in the mutaßt 536-21 led to a dramatic reduction of bacterial counts from almost tOS to only 40 cells per g of kidney. The reintroduction of the cloned S fimbrial adhesin determinant (sfa) increases the virulence of the avirulent mutant strain by a factor of 20; almost the same eß'ect was observed after restoration of serum resistance by Integration of an sja+ recombinant cosmid into the chromosome. Additional reintroduction of the my+ phenotype by Iransformation of two hly determinants increased the virulence of the strains. Demolysin production determined increased renal elimination of leukocytes and erythrocytes. Thus all three determinants investigated, S fimbriae, serum resistance, and hemolysin, contribute to the multifactorial phenomenon of E. coli nephropathogenicity.
Recently we have described the molecular cloning of the genetic determinant coding for the S-fimbrial adhesin (Sfa), a sialic acid-recognizing pilus frequently found among extraintestinal Eschenchili coli isolates. Fimbriae from the resulting Sfa + E. coli K-12 clone were isolated, and an Sfa-specific antiserum was prepared. Western blots indicate that S fimbriae isolated from different uropathogenic and meningitis-associated E. coli strains, including 083:Kl isolates, were serologically related. The Sfa-specific antibodies did not cross-react with P fimbriae, but did cross-react with FlC fimbriae. Furthermore the sja+ recombinant DNAs and some cloned s/a-flanking regions were used as probes in Southem experiments. Chromosomal DNAs isolated from 018:Kl and 083:Kl meningitis strains with and without S fimbriae and from uropathogenic 06:K + strains were hybridized against these sfa-specific probes. Only one copy of the sfa determinant was identified on the chromosome of these strains. No sfa-specific sequences were observed on the chromosome of E. coli K-12 strains and an 07:Kl isolate. With the exception of small alterations in the sfa-coding region the genetic determinants for S fimbriae were identical in uropathogenic 06:K + and meningitis 018:Kl and 083:Kl strains. The sfa determinant was also detected on the chromosome of Kl isolates with an Sfa-negative phenotype, and specific cross-hybridization signals were visible after blotting against FlC-specific DNA. In addition homology among the different strains was observed in the sfa-flanking regions.
The virulence of the uropathogenic E. coli strain 536 (06: K 1 5: H31) which produces the S-fimbrial adhesin (Sfa•), is serum-resistant (Sre+) and hemolytic (Hiy+) and its derivatives were assessed in five different animal models. Cloned hemolysin (h/y) determinants from the Chromosomes of 06,018 and 075 E. colistrains and from the plasmid pHiy152 were introduced into the spontaneaus Sfa-, Sre-, Hly- mutant 536-21 and its Sfa+, Sre+, Hly- variant 536-31. As already demonstrated for the 536-21 strains {lnfect. Immun. 42: 57-63) the 018-hly determinant but not the plasmid-encoded hly determinant of pHiy 1 52 transformed into 536-31 contribute to lethality in a mouse peritonitis modal. Similar results were obtained with both Hlyhost strains and their Hly+ transformants in a chicken embryo test and in a mouse nephropathogenicity assay in which the renal bacterial counts were measured 1 5 min to 8 hours after i.v. infection. S-fimbriae and serum resistance had only a marginal influence in these three in vivo systems. ln centrast all three factors, S-fimbriae, serum resistance and hemolysin, were necessary for full virulence in a respiratory mouse infection assay. ln a subcutaneously-induced sepsis model in the mouse restoration of S-fimbriae and serum resistance and separately chromosomally-encoded hemolysis increased virulence to a Ievel comparable to that of the parental 536 strain.
Purified S fimbriae and an Escherichia coli strain carrying the recombinant plasmid pANN801-4 that encodes S fimbriae were tested for adhesion to frozen sections of human kidney. The fimbrlae and the bacteria bound to the same tissue domains, and in both cases the binding was specifically inhibited by the receptor analog of S fimbria, sialyl(a2-3)1actose. S fimbriae bound specifically to the epithelial elements in the kidneys; to the epithelial cells of proximal and distal tubules as weil as of the collecting ducts and to the visceral and parietal glomerular epithelium. In addition, they bound to the vascular endothelium of glomerull and of the renal Interstitium. No blnding to connective tissue elements was observed. The results suggest that the biological functlon of S fimbriae is to mediate the adheslon of E. coli to human epithelial and vascular endothellal ceUs.
The hemolytic, uropathogenic Escherichia coli 536 (06:K15:H31) contains two inserts in its chromosome (insert I and insert II), both of which carried hly genes, were rather unstable, and were deleted spontaneously with a frequen~y of 10-3 to 10-4• These inserts were not found in the chromosome of two nonhemolytic E. coli strains, whereas the chromosomal ~equences adjacent to these inserts appeared tobe again homologous in the uropathogenic and two other E. coü strains. Insert I was 75 kilobases in size and was ftanked at both ends by 16 base pairs (bp) (TTCGACTCCTGTGATC) which were arranged in direct orientation. For insert I it was demonstrated that deletion occurred by recombination between the two 16-bp ftanking sequences, since mutants lacking this insert still carried a single copy of the 16-bp sequence in the chromosome. 8oth inserts contained a functional hemolysin determinant. However, the loss of the inserts not only atfected the hemolytic phenotype bot led to a considerable reduction in serum resistance and the loss of mannose-resistant hemagglutination, caused by the presence of S-type funbriae (sja). lt is shown that the Sfa-negative phenotype is due to a block in transcription of the sfa genes. Mutants of strain 536 which lacked both inserts were entirely avirulent when tested in several animal model systems.
The genetic determinant coding for the Pspecific F8 fimbriae was cloned from · the chromosome of the Escherichia coli wild-type strain 2980 (018: K5: H5: FlC, F8). The F8 determinant was further subcloned into the Pstl site of pBR322 and a restriction map was established. In a Southern hybridization experiment identity between the chromosomally encoded F8 determinant of 2980 and its cloned Counterpart was demonstrated. The cloned F8 fimbriäe and those of the wild type strain consist of a protein subunit of nearly 20 kDa. F8 fimbriated strains were agglutinated by an F8 polyclonal antiserum, caused mannose-resistant hemagglutination and attached to human uroepi thellal cells. The cloned F8 determinant was weil expressed in a variety of host strains.
Characterization of a monoclonal antibody against the fimbrial F8 antigen of Escherichia coli
(1986)
A monoclonal lgG 1 antibody against F8 fimbriae was obtained with the hybridoma technique using spieen cells from C3H/f rnice immunised with a fimbrial preparation of Escherichia coli 2980 (018ac: K5: H-: FIC, F8) and Sp 2/0 Ag8 myeloma cells. The hybrid cells were cloned twice by lirniting dilution and grown in tissue culture. The monoclonal antibody was purified from culture supernatants on Protein A Sepharose. lt reacted with F8 fimbriae in colony blot, enzyme-linked immunosorbent assay (ELISA) and immunoblot after electrotransfer from sodium dodecyl sulphate-polyacrylarnide gel electrophoresis (SOS-PAGE) of fimbrial preparations. The antibody bound to and agglutinated F8-fimbriated bacteria.
The haemolysin (hly) determinant of the plasmid pHly152 contains an IS2 element at 469 bp upstream of the hlyC gene. The sequence at the other (right-hand) end (RS) also shows multiple hybridization with the plasmid pHly152 and the chromosome of some Escherichia coli strains but the nucleotide sequence of this region does not reveal the typical properties of an IS element. Similar arrangements in the regions flanking the hly determinant are also found on various Hly plasmids from uropathogenic E. coli strains. Chromosomal hly determinants Iack both flanking sequences (IS2 and RS) in the immediate vicinity of the hly genes. The sequences immediately upstream of the hlyC gene have been determined from several chromosomal hly determinants and compared with the corresponding sequence of the hly determinant of the plasmid pHly152. We show that these sequences, which contain one promoter (left promoter, phlyL) in all hly determinants tested, vary considerably although common sequence elements can still be identified. In contrast, only relatively few nucleotide exchanges have been detected in the adjacent structural hlyC genes. The A + T content of the 200 bp sequence upstream of hlyC is very high (72 mol% A + T) but even the structural hly genes show a considerably higher A + T content (about 60 mol%) than the E. coli chromosome on average (50 mol% A+T) suggesting that the hly determinant may not have originated in E. coli.
We investigated the role of bacterial adherence and hemolysin production from Escherichia coli parent and genetically cloned strains as to their eft'ects on bistaJidne release from rat mast cells and leukotriene generation from human polymorphonuclear granulocytes. These mediators were involved in the induction of inftammatory disease processes and led, for example, to enhancement of vascular permeability, chemotaxis (leukotriene 84 [LTB4]), chemoaggregation, lysosomal enzyme release, and smooth muscle contraction, (LTC4, LTD4 , and LTE4). Washed bacteria (E. coli K-12 Ms+ my=; E. coli 536 Ms+ MR= my=) as weil as their culture supematants were analyzed. Washed E. coli K-12 (Hiy+), unlike Hly- strains, induced high amounts of histamine release from rat mast cells and chemotactic activity from human polymorphonuclear granulocytes. Significant leukotriene releasewas obtained with washed E. coli K-12 my+ strains and their bacterial culture supematants. Leukotriene induction was dependent on the amount of hemolysin activity present in the supematant. However, additional soluble factors should also be considered. The presence of hemolysin appeared to aceeierate and enhance the rate of phagocytosis of bacteria by neutrophUs. When E. coli 536 (MS+ MR= Hly=) strains were analyzed, the simultaneous presence of MR+ pili and hemolysin production led to an increase in histamine release as compared with MR- my+ strains. The genetically cloned MR+ my+ E. coli 536 strain induced higher amounts of IeukotrieDes as compared with the wUd-type strain. Our data soggest a potent role for adhesins and hemolysin as virulence factors in inducing the release of inftammatory mediators.
The Qropathogenic Escherichia coli strain 536 (06:K15:H31) exhibits a mannose-resistant hemagglutination phenotype (Mrh) with bovine erythrocytes and delayed Mrh with human and guinea pig erythrocytes. Neuraminidase treatment of the erythrocytes abolishes mannose resistant hemagglutination, which is typical for X fimbriae. E. coli strain 536 synthesizes two different fimbriae (Fim phenotype) prQtein subunits, 16.5 and 22 kilodaltons in size. In addition the strain shows mannose-sensitive hemagglutination and common type I (Fl) fimbriae. The cosmid clone E. coli K-12(pANN801) and another nine independently isolated Mrh+ cosmid clones derived from a cosmid gene bank of strain 536 express the 16.5-kilodalton protein band, bot not the 22-kilodalton protein, indicating an association of the Mrh+ property with the "16.5-kilodalton fimbriae." All cosmid clones were fimbriated, and they reacted with antiserum produced against Mrh+ fimbriae of the E. coli strain HB101(pANN801) and lacked mannose-sensitive hemagglutination (Fl) funbriae. From the Mrh fim cosmid DNA pANN801, several subclones coding for hemagglutination and X fimbriae were constructed. Subclones that express both hemagglutination and fimbriae and subclones that only code for the hemagglutination antigen were isolated; subclones that only produce fimbriae were not detected. By transposon Tn5 mutagenesis we demonstrated that about 6.5 kilobases of DNA is required for the Mrh+ Fim+ phenotype, and the 1.5- to 2-kilobase DNA region coding for the structural proteiil of the fimbriae has been mapped adjacent to the region responsible for the Mrh+ phenotype. Two different regions can thus be distinguished in the adhesion determinant, one coding for hemagglutination and the other coding for fimbria formation. Transformation of plasmid DNA from these subclones into a Mrh- Fim- mutant of E. coli 536 and into a galE (rough) strain of Salmonella typhimurium yielded transformants that expressed both hemagglutination and fimbria production.
Potential virulence, as defined by combined Ievels of adhesion to urinary epithelial cells, serum resistance, and mouse toxicity, was assessed for Escherichia coli strains causing symptomatic and asymptomatic urinary tract infections in relation to the carriage of hemolysin and other suspected virulence determinants. Hemolysin production (Hly), associated with certain 0 (04, 06, 018, and 075), K (5), and hemagglutination (VI and VII) antigenic types but not colicin V production (Cva), was evident in 83 and 60% ofisolates in groups possessing high potential virulence andin only 11 and 6% of those with low virulence. Strains of particular 0-types were not more virulent per se, but among the serotypes, specific combinations of virulence factors appeared decisive, e.g., 018 HAVI B/D/G Hly+ K5+t- and 018 HAIIIIIVBN Hly- Cva +t- Kl +t- strains were, respectively, of high and low potential virulence. Isolates with high potential virulence were found to a similar extent in symptomatic and asymptomatic infections.
After intraperitoneal injection of mice with Escherichia coli strains isolated from patients with urinary tract infections, the mortality due to hemolytic (Hly+) and nonhemolytic (Hiy-) isolates was 77 and 40%, respectively. Deletion of the chromosomal hemolysin (h/y) determinant in an E. co/i 06:K15:H31 urinary tract infection strain led to a significant reduction in toxicity for mice, and its reintroduction on a recombinant plasmid partially restored the original toxicity. Although introduction of the cloned plasmid pHiy152-encoded hly determinant into the Hly- E. coli 06 mutant strain increased toxicity by only a marginal degree, transformation with the cloned chromosomal hly determinants from two E. coli strains of serotypes 018ac:K5:H- and 075:K95:H? resulted in markedly greater toxicity, even exceeding that of the original Hly+ E. coli 06 wild-type strain.
Evidence for T cell recognition in mice of a purified lipophosphoglycan from Leishmania major
(1989)
We have previously reported that a Leishmania major lipophosphoglycan (LPG), given with killed Corynebacterium parvum as an adjuvant, can vaccinate mice against cutaneous leishmaniasis. In order to analyze whetber T cells are able to recognize this important parasite antigen, we have studied both humoral and cellular immune responses to L. major LPG that bad been isolated from promastigotes by sequential solvent extraction and bydrophobic chromatography. The data sbow that immunization of mice with highly purified LPG induced an increase in frequency of L. major-reactive T cells and the production of immunoglobulin G antibodies to LPG. Furthermore, genetically resistant mice infected with L. major were able to develop a specific delayed-type hypersensitivity response in the ear to L. major LPG. These findings strongly suggest that T cells can recognize and respond to glycolipid antigens, in this case a bost-protective Leishmania LPG, even though such antigens appear not to be potent T-cell stimulators in mice.
In this study we report that cloned Thy-l +, L3T4-, Lyt-l-, Lyt-2+, H-Y-specific and H-2Db-restricted cytotoxic T ce11 lines (CTLL) when indueed by lectin or antigen secrete a soluble mediator(s) (SF) that inhibits proliferation and generation of cytotoxic lymphocytes (CTL) in mixed lymphocyte cultures (MLC). The biological activity was separable by gel filtration and appeared as a broad peak in the moleeular mass range between 10000 and 50000 kDa. It was found that the suppressive activity released by CTLL neither strictly correlates with their cytotoxic potential nor with their ability to produce immune interferon or Iymphotoxin. SF was shown to elicitits activity in an antigen-nonspeeific manner in that it suppressed the maturation of T lymphocytes responding to both, the appropriate H-Y antigen as weH as to unrelated H_2d alloantigens or to the hapten 2,4,6-trinitrophenyl (TNP). The effect of SF on CTL responses was most pronounced in early phases of primary or secondary MLC. When analyzed for its inhibitory activity on precursor ceHs in populations selected for either Lyt-2- or L3T4- lymphocytes, it was found that SF interfered with the maturation of both subsets. The inhibition of CTL responses elicited by SF could not be reversed by the addition of exogenous interleukin 2. The findtng that SF also inhi. bited the proliferation of some but not a11 antigen-dependent cloned T ceHs with helper or eytc'toxic potential provides evidence that the faetor also may regulate effector lymphl)cytes. In addition, the results support the assumption that SF exerts its effect direetly on the responder rather than the stimulator population, and demonstrate that the development of CTL from their preeursor eeHs is contro11ed at least in part by the eytotoxic effeetor cells themselves via a soluble factor(s) that interferes with distinct stages of T ce11 maturation. These findings again emphasize the expression of multiple functions by CTL and indieate their possible role du ring the course of an immune response by their capability to eliminate target cells and to secrete a soluble product(s) that mediates feedback contro!.
We have previously shown that during an infection with Leishmania major, susceptible BALB/c mice, as opposed to mice of a resistant strain (C57BLl6), are primed by lipopolysaccharide for the production of high levels of tumor necrosis factor-\(\alpha\) (TNF-\(\alpha\)) which is known to be a potent maerophage M\(\Phi\) stimulator in other parasitic diseases. In the present study we investigated whether TNF-\(\alpha\) activates M\(\Phi\) for killing of L. major parasites. In the absence of interferon-y (IFN-\(\gamma\)) or lipopolysaccharide, TNF-\(\alpha\) (0.025-25000 U/ml) failed to activate peritoneal exudate M\(\Phi\) from BALB/c mice for killling of L. major amastigotes. In the presence of suboptimal doses of IFN-\(\gamma\) (5 or 10 Vlml), however, TNF-\(\alpha\) mediated a rapid elimination of intracellular parasites, which was highly significant compared to IFN-\(\gamma\) alone. Tbe combination of TNF with interleukin 4, in contrast, was inactive in this respect and allowed survival of intracellular parasites. From these data we conelude that the presence of IFN-\(\gamma\) is crucial for TNF-\(\alpha\)-mediated killing of L. major parasites by M\(\Phi\). Disease progression in susceptible mice therefore seems to be a consequence of a deficiency of IFN-\(\gamma\) and a predominance of interleukin 4 rather than the result of an excess amount of TNF-\(\alpha\).
The saprophytic filamentous fungus Aspergillus fumigatus has been gaining importance as an opportunistic human pathogen over the past decades. Advances in modern medicine have created a growing group of patients susceptible to infection with A. fumigatus, often contracting potentially deadly invasive aspergillosis. The virulence of this pathogen appears to be a multifactorial trait, a combination of physiological characteristics that enables the fungus to infect immunocompromised humans. This work concentrates on the nitrogen metabolism of A. fumigatus, which is essential for meeting the nutritional needs inside the human host. Using DNA microarrays, the transcriptional response during growth on three different secondary nitrogen sources was examined, which revealed the metabolic versatility of A. fumigatus, especially when challenged with proteins as the sole source of nitrogen. In-depth transcriptional profiling of the eight-member oligopeptide transporter (OPT) gene family underlined the importance of oligopeptide transport for growth on complex nitrogen sources like BSA or collagen. Heterologous expression of the opt genes in Saccharomyces cerevisiae showed their functionality as oligopeptide transporters, and characterized their substrate specificity. Using a Cre/loxP based genetic tool, a complete deletion of all opt genes in A. fumigatus was achieved. The resultant strain exhibited diminished growth on medium where the oligopeptide GPGG was the sole nitrogen source, but did not show any other in vitro phenotype. The opt deletion strain was not attenuated in virulence in a murine model of pulmonary aspergillosis, suggesting that the OPT gene family is not necessary for successful infection. The connection of oligopeptide transport and extracellular proteolytic activity was investigated by deleting the genes encoding Dpp4 and Dpp5, two dipeptidyl peptidases, or PrtT, the transcriptional regulator of major secreted proteases, in the complete opt deletion background. In contrast to the deletion of dpp4 and dpp5, which did not result in any additional phenotype, the absence of prtT led to a drastic growth defect on porcine lung agar. This suggests a synergistic action of extracellular proteolytic digest of proteins and transport of oligopeptide degradation products into the cell. Finally, this work established the bacterial β-Rec/six site-specific recombination system as a novel genetic tool for targeted gene deletion in A. fumigatus.
Malaria still persists as one of the deadliest infectious disease in addition to AIDS and tuberculosis. lt is a leading cause of high mortality and morbidity rates in the developing world despite of groundbreaking research on global eradication of the disease initiated by WHO, about half a century ago. Lack of a commercially available vaccine and rapid spread of drug resistance have hampered the attempts of extinguishing malaria, which still leads to an annual death toll of about one million people. Resistance to anti-malarial compounds thus renders search for new target proteins imperative. The kinome of the human malaria parasite Plasmodium falciparum comprises representatives of most eukaryotic protein kinase groups, including kinases which regulate proliferation and differentiation processes. Several reports till date have suggested involvement of parasite kinases in the human host and as well as in the mosquito vector. Kinases essential for life cycle stages of the parasite represent promising targets for anti-malarial compounds thus, provoking characterization of additional malarial kinases. Despite extensive research on most plasmodial enzymes, very little information is available regarding the four identified members of the cyclin dependent kinase like kinase (CLK) family. Thus, the present thesis dealt with the functional characterization of four members of the PfCLK kinase family of the parasite denoted as PfCLK-1/Lammer, PfCLK-2, PfCLK-3 and PfCLK-4 with a special focus on the first two kinases. Additionally, one Ca2+/Calmodulin dependent putative kinase-related protein, PfPKRP, presumed to be involved in sexual stage development of the parasite, was investigated for its expression in the life cycle of the parasite. In other eukaryotes, CLK kinases regulate mRNA splicing through phosphorylation of Serine/Arginine-rich proteins. Transcription analysis revealed abundance of PfCLK kinase genes throughout the asexual blood stages and in gametocytes. By reverse genetics approach it was demonstrated that all four kinases are essential for completion of the asexual replication cycle of P. falciparum. PfCLK 1/Lammer possesses two nuclear localization signals and PfCLK-2 possesses one of these signals upstream of the C-terminal catalytic domains. Protein level expression and sub-cellular localization of the two kinases was determined by generation of antiserum directed against the kinase domains of the respective kinase. Indirect immunofluorescence, Western blot and electron microscopy data confirm that the kinases are primarily localized in the parasite nucleus, and in vitro assays show that both enzymes are associated with phosphorylation activity. Finally, mass spectrometric analysis of co immunoprecipitated proteins shows interactions of the two PfCLK kinases with proteins, which have putative nuclease, phosphatase or helicase functions. PfPKRP on the other hand is predominantly expressed during gametocyte differentiation as identified from transcriptional analysis. Antiserum directed against the catalytic domain of PfPKRP detected the protein expression profile in both asexual and gametocyte parasite lysates. Via immunofluorescence assay, the kinase was localized in the parasite cytoplasm in a punctuated manner, mostly in the gametocyte stages. Reverse genetics resulted in the generation of PfPKRP gene-disruptant parasites, thus demonstrating that unlike CLK kinases, PfPKRP is dispensable for asexual parasite survival and hence might have crucial role in sexual development of the parasite. On one hand, characterization of PfCLK kinases exemplified the kinases involved in parasite replication cycle. Successful gene-disruption and protein expression of PfPKRP kinase on the other hand, demonstrated a role of the kinase in sexual stage development of the parasite. Both kinase families therefore, represent potential candidates for anti-plasmodial compounds.
Shigellosis, or bacillary dysentery, is a rectocolitis caused by the gram-negative, enteroinvasive bacteria of the genus Shigella. Shigellosis still remains a major public health burden with an estimated 80 million cases of bloody diarrhoea and 700.000 deaths per year, primarily in children under the age of 5. Shigella disrupts, invades, and causes inflammatory destruction of the colonic epithelium in humans through virulence effectors secreted by the type III secretion apparatus (TTSA). In contrast to the Shigella-induced manipulation of the host innate immune response, the impact of Shigella on the adaptive immunity has been poorly studied thus far. In order to understand why the naturally induced protective humoral response requires several infections to be primed and is of short duration, the work presented here investigates if Shigella is able to directly interact with T cells. Indeed, it has been shown that Shigella was able to invade and proliferate inside T cells. Furthermore, Shigella was able to inhibit T cell migration through a TTSA effector. Moreover, the Shigella effector IpgD, a phosphoinositide 4-phosphatase that specifically dephosphorylates phosphatidylinositol-(4,5)-bisphosphate (PIP2) into phosphatidylinositol-(5)-monophosphate (PI(5)P), was identified as the effector responsible for the observed inhibition. It could be demonstrated that IpgD was responsible for a reduction of intracellular PIP2 levels in T cells. Further experiments showed a reduced level of phosphorylated ezrin, radixin and moesin (ERM) proteins in infected, as well as with IpgD transfected, T cells. The ERM protein family plays an imported role in signal transduction and motility and their activity is closely related to the binding of PIP2. Therefore, the low level of PIP2 leads to a dephosphorylation of the ERM proteins which inhibits T cells response to chemokine stimulation. Indeed, IpgD transfected T cells show a reduced ability to re-localise the ERM proteins upon chemokine stimulation. Targeting T cell motility, via TTSA effectors, could explain the low level of specific T cell priming during Shigella infection. This is the first report of Shigella induced manipulation of T cell function and on the inhibition of T cell migration by a bacterial effector.
Avian pathogenic Escherichia coli (APEC) represent a subset of the so-called extraintestinal pathogenic Escherichia coli (ExPEC) pathotype that can cause various extraintestinal infections in humans and animals. APEC are the causative agent of localized colibacillosis or systemic infection in poultry. In this latter case, the syndrome starts as an infection of the upper respiratory tract and develops into a systemic infection. Generally, ExPEC are characterized by a broad variety of virulence-associated factors that may contribute to pathogenesis. Major virulence factors, however, that clearly define this pathotype, have not been identified. Instead, virulence-associated genes of ExPEC and thus also of APEC could be used in a mix-and-match-fashion. Both pathotypes could not be clearly distinguished by molecular epidemiology, and this suggested a hypothetical zoonotic risk caused by APEC. Accordingly, the main scientific question of this study was to characterize common traits as well as differences of APEC and human ExPEC variants that could either support the possible zoonotic risk posed by these pathogenic E. coli strains or indicate factors involved in host specificity. Comparative genomic analysis of selected APEC and human ExPEC isolates of the same serotype indicated that these variants could not be clearly distinguished on the basis of (i) general phenotypes, (ii) phylogeny, (iii) the presence of typical ExPEC virulence genes, and (iv) the presence of pathoadaptive mutations. Allelic variations in genes coding for adhesins such as MatB and CsgA or their regulators MatA and CsgD have been observed, but further studies are required to analyze their impact on pathogenicity. On this background, the second part of this thesis focused on the analysis of differences between human ExPEC and APEC isolates at the gene expression level. The analysis of gene expression of APEC and human ExPEC under growth conditions that mimick their hosts should answer the question whether these bacterial variants may express factors required for their host-specificity. The transcriptomes of APEC strain BEN374 and human ExPEC isolate IHE3034 were compared to decipher whether there was a specific or common behavior of APEC and human ExPEC, in response to the different body temperatures of man (37°C) or poultry (41°C). Only a few genes were induced at 41 °C in each strain relative to growth at 37 °C. The group of down-regulated genes in both strains was markedly bigger and mainly included motility and chemotaxis genes. The results obtained from the transcriptome, genomic as well as phenotypic comparison of human ExPEC and APEC, supports the idea of a potential zoonotic risk of APEC and certain human ExPEC variants. In the third part of the thesis, the focus was set on the characterization of Mat fimbriae, and their potential role during ExPEC infection. Comparison of the mat gene cluster in K-12 strain MG1655 and O18:K1 isolate IHE3034 led to the discovery of differences in (i) DNA sequence, (ii) the presence of transcriptional start and transcription factor binding sites as well as (iii) the structure of the matA upstream region that account for the different regulation of Mat fimbriae expression in these strains. A negative role of the H-NS protein on Mat fimbriae expression was also proven at 20 °C and 37 °C by real-time PCR. A major role of this fimbrial adhesin was demonstrated for biofilm formation, but a significant role of Mat fimbriae for APEC in vivo virulence could not yet be determined. Interestingly, the absence of either a functional matA gene or that of the structural genes matBCDEF independently resulted in upregulation of motility in E. coli strains MG1655 and IHE3034 by a so far unknown mechanism. In conclusion, the results of this thesis indicate a considerable overlap between human and animal ExPEC strains in terms of genome content and phenotypes. It becomes more and more apparent that the presence of a common set of virulence-associated genes among ExPEC strains as well as similar virulence gene expression patterns and phylogenetic backgrounds indicate a significant zoonotic risk of avian-derived E. coli isolates. In addition, new virulence factors identified in human ExPEC may also play a role in the pathogenesis of avian ExPEC.
A novel technique for independent and simultaneous labeling of two antigens expressed on individual cells (referred to as mixed labeling) is presented. The staining procedure combined three-step (streptavidin-biotin) immunogold-silver staining with three-step immunoenzymatic labeling. To ensure both high specificity and high sensitivity, particular emphasis was placed on designing a protocol that avoids immunological crossreactivity between the antibody reagents and overlapping of the final color products. Two examples for usage of this mixed labeling technique are described: lymphocyte subpopulations were identified in inflammatory lesions of human skin and infected host cells were characterized in the skin of mice infected with the obligatory intracellular parasite Leishmania major, a cause of human cutaneous leishmaniasis.
Asymptomatische Bakteriurie (ABU) stellt eine bakterielle Infektion der Harnblase über einen langen Zeitraum dar, die häufig von Escherichia coli hervorgerufen wird, ohne dass typische Symptome einer Harnwegsinfektion auftreten. Um die Charakteristika von ABU E. coli Isolaten genauer zu untersuchen, wurden die Geno- und Phänotypen von 11 ABU-Isolaten verglichen. Außerdem wurden in mehreren aufeinanderfolgenden in vivo-Reisolaten des Modell-ABU Stammes 83972 die Veränderungen im Transkriptom, Proteom und Genom während einer langfristigen Persistenz in der menschlichen Blase charakterisiert. Schließlich wurde der Effekt des menschlichen Wirtes auf die bakterielle Adaptation durch einen Vergleich von in vitro- mit in vivo-kultivierten Stämmen abgeschätzt. ABU-Isolate stellt eine heterogene Gruppe von Organismen dar. Diese können den vier phylogenetischen Hauptgruppen von E. coli sowie unterschiedlichen klonalen Gruppen zugeordnet werden. Dementsprechend unterscheiden sie sich erheblich bezüglich der Zusammensetzung des Genomes, der Genomgröße und auch der Ausstattung mit UPEC-typischen Virulenz-assoziierten Genen. Multi-Lokus-Sequenz-Typisierung legt nahe, dass bestimmte ABU Stämme sich durch Genomreduktion aus UPEC Stämmen entwickelt haben, die eine Harnwegsinfektion mit charakteristischen Symptomen auslösen konnten. Folglich erlaubt die hohe Genomplastizität von E. coli keine generalisierte Betrachtung einzelner Isolate eines Klons. Genomreduktion über Punktmutationen, Genom-Reorganisation und Deletionen resultierte in der Inaktivierung einiger Gene, die für einige UPEC Virulenz-Faktoren kodieren. Dies stützt die Vorstellung, dass eine verminderte bakterielle Aktivierung der Entzündung der Wirtsschleimhaut den Lebensstil von ABU (bei diesen E. coli-)Isolaten fördert. Genregulation und genetische Diversität sind Strategien, die es Bakterien ermöglichen unter sich fortlaufend ändernden Bedingungen zu leben bzw. zu überleben. Um die anpassungsbedingten Veränderungen bei einem langfristigen Wachstum in der Blase zu untersuchen, wurden aufeinanderfolgende Reisolate, denen eine langfristige in vivo-Kolonisierung im menschlichen Wirt beziehungsweise eine in vitro-Kultivierung vorausgegangen ist, im Hinblick auf Veränderungen Genexpression und Genomorganisation analysiert. In diesem Zusammenhang konnte gezeigt werden, dass E. coli in der Lage ist, seine metabolischen Netzwerke verschiedenen Wachstumsbedingungen anzupassen und individuelle bakterielle Kolonisierungsstrategien entwickeln kann. Transkriptom- und Proteom-Analysen zeigten verschiedene metabolische Strategien zur Nährstoffbeschaffung und Energieproduktion bei untersuchten in vivo-Reisolaten vom Stamm 83972, die es ihnen ermöglichen, den Wirt zu kolonisieren. Das Zurückgreifen auf D-Serin, Deoxy- und Ribonucleoside sowie die bidirektionale Umwandlung zwischen Pentose und Glucuronat waren hoch-regulierte Stoffwechselwege, die die in vivo-Reisolate mit zusätzlicher Energie für ein effizientes Wachstum in der Blase versorgen. Zudem wurden in dieser Studie die Netzwerke für eine Reaktion auf Abwehrmechanismen des Wirtes erforscht: Erstmals wurde hier die Rolle der Klasse-III-Alkoholdehydrogenase AdhC, bekannt durch ihre Bedeutung bei der Entgiftung von Stickstoffmonoxid, bei der Wirtsantwort während einer asymptomatischen Bakteriurie gezeigt. Aufeinanderfolgende in vivo- und in vitro-Reisolate vom Stamm 83972 wurden ebenfalls bezüglich ihrer Genomstruktur analysiert. Einige Veränderungen in der Genomstruktur der aufeinanderfolgenden Reisolate, die von einer humanen Kolonisierungsstudie stammen, implizieren die Bedeutung einer Interaktion der Bakterien mit dem Wirt bei der Mikroevolution der Bakterien. Dagegen war die Genomstruktur von Reisolaten eines langfristigen in vitro-Kultivierungsexperiments, bei dem sich der Stamm 83972 ohne Wirtskontakt vermehrt hat, nicht von Veränderungen betroffen. Das legt nahe, dass die Immunantwort eine Genomplastizität fördert und somit eine treibende Kraft für den ABU Lebensstil und die Evolution im Harnwegstrakt ist.
Murine epidermal Langerhans cells (LC) have been demonstrated to stimulate a vigorous T cell response to Leishmania major, a cause of human cutaneous leishmaniasis. It was therefore of interest to analyze whether LC can take up viable parasites. Epidermal cells were obtained from mouse ear skin for incubation with L. major and subsequent detection of intracellular parasites by cytochemistry. Freshly isolated LC, but not cultured LC, phagocytosed L. major and the uptake was inhibited by antibodies to the complement receptor type 3. Electron microscopic studies revealed the presence of viable amastigotes within Le. Moreover, with double-Iabeling techniques, L. major-containing LC could also be detected in infected skin. The results demonstrate that LC can internalize L. major. Since the number of organisms per infected LC remained consistently low, the prime task of LC may not be the promotion of parasite spreading but the presentation of L. major antigen to T cells and, thus, the regulation of the cellular immunity during cutaneous leishmaniasis.
Freshly isolated human T lymphocytes were tested for their response to mycobacteria, mycobacteriallysates, 2 dimensional (2D) PAGE separated mycobacteriallysates, leishmania and defined leishmanial antigen preparations. While,o T cells proliferated vigourously in the presence of mycobacteria and mycobacteria derived lysates, a significant stimulation from 2 D gel separated lysates was not detected. In addition '10 T cells failed to respond towards leishmania or leishmanial components. In the ab T cell compartment some donors, presumably according to their state of immunity against mycobacteria, responded to mycobacteria, mycobacterial lysates and 2 D gel separated mycobacterial lysates. Neither freshly isolated '10 T cells nor ab T cells from naive donors did mount a significant immune response against leishmania.
Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) are exploited by human-specific pathogens to anchor themselves to or invade host cells. Interestingly, human granulocytes express a specific isoform, CEACAM3, that can direct efficient, opsonin-independent phagocytosis of CEACAM-binding Neisseria, Moraxella and Haemophilus species. As opsonin-independent phagocytosis of CEACAM-binding Neisseria depends on Src-family protein tyrosine kinase (PTK) phosphorylation of the CEACAM3 cytoplasmic domain, we hypothesized that an SH2-containing protein might be involved in CEACAM3-initiated, phagocytosis-promoting signals. Accordingly, we screened glutathione-S-transferase (GST) fusion proteins containing SH2 domains derived from a panel of signaling and adapter molecules for their ability to associate with CEACAM3. In vitro pull-down assays demonstrated that the SH2 domain of the adapter molecule Nck (GST-Nck SH2), but not other SH2 domains such as the Grb2 SH2 domain, interact with CEACAM3 in a phosphotyrosine-dependent manner. Either deletion of the cytoplasmic tail of CEACAM3, or point-mutation of a critical arginine residue in the SH2 domain of Nck (GST-NckSH2R308K) that disrupts phosphotyrosine binding, both abolished CEACAM3-Nck-SH2 interaction. Upon infection of human cells with CEACAM-binding Neisseria, full-length Nck comprising an SH2 and three SH3 domains co-localized with tyrosine phosphorylated CEACAM3 and associated bacteria as analyzed by immunofluorescence staining and confocal microscopy. In addition, Nck could be detected in CEACAM3 immunoprecipitates confirming the interaction in vivo. Importantly, overexpression of a GFP-fusion protein of the isolated Nck SH2 domain (GFP-Nck-SH2), but not GFP or GFP-Nck SH2 R308K reduced CEACAM3-mediated phagocytosis of CEACAM-binding Neisseria suggesting that the adaptor molecule Nck plays an important role in CEACAM3-initiated signaling leading to internalization and elimination of human-specific pathogens.
While clear evidence exists for the direct involvement of cytolysins in the pathogenesis of Gram-positive bacteria, the significance of Gram-negative haemolysins remains unclear. This paper presents briefly data indicating a role for haemolysin production in infections caused by Escherichia coli and also experiments which have allowed an analysis of the molecular basis of the haemolysis among pathogenic and non-pathogenic strains of this species.
Streptococcus pneumoniae (pneumococci) are Gram-positive bacteria and commensals of the nasopharyngeal cavity. Besides colonization, pneumococci are responsible for severe local infections such as otitis media, sinusitis and life-threatening invasive diseases, including pneumonia, sepsis and meningitis. The surface of pneumococci is decorated with proteins that are covalently or non-covalently anchored to the cell wall. The most unique group of cell wall associated proteins in pneumococci are the choline-binding proteins (CBPs). PspC, also known as SpsA or CbpA, is a multifunctional choline-binding protein that plays an essential role in pneumococcal pathogenesis by functioning as an adhesin. PspC promotes adherence of pneumococci to mucosal epithelial cells by interacting in a human specific manner with the free secretory component (SC) or to SC as part of the secretory IgA (SIgA) or polymeric immunoglobulin receptor (pIgR). PspC also interacts specifically with the soluble complement Factor H. Apparently, PspC uses two different epitopes for binding the soluble host protein Factor H and SC of pIgR. However, the mechanism by which these independent interactions facilitate pneumococcal infections under physiological and host specific conditions have not yet been completely elucidated. This study aims to explore the impact of the PspC interaction with human pIgR (hpIgR) or complement regulator Factor H on pneumococcal virulence. Here the cellular and molecular basis of PspC-mediated adherence to and invasion of host epithelial and endothelial cells was demonstrated. The genetic approach, specific pharmacological inhibitors and immunoblot analysis demonstrated the complexity of the induced signal transduction pathways during PspC-hpIgR mediated pneumococcal uptake by host cells. Inhibition studies with specific inhibitors of actin cytoskeleton and microtubules demonstrated that the dynamics of host cell cytoskeleton are essential for pneumococcal uptake by mucosal epithelial cells. Moreover, this study reports for the first time that the small GTPase Cdc42 is essential for pneumococcal internalization into epithelial cells via the PspC-hpIgR mechanism. In addition, in infection experiments performed in presence of specific inhibitors of PI3-kinase/Akt and protein tyrosine kinase (PTKs), hpIgR-mediated pneumococcal uptake by host cells was significantly blocked. Amongst PTKs the Src kinase pathway, ERK1/2 and JNK pathways were implicated during pneumococcal ingestion by hpIgR expressing cells. In addition, inhibition experiments performed in the presence of individual inhibitors or with a combination of inhibitors suggested the independent activation of PI3-kinase/Akt and Src kinase pathways during pneumococcal infections of hpIgR expressing cells. By employing specific inhibitors and siRNA in cell culture infection experiments it was further demonstrated that pneumococcal endocytosis by host epithelial cells via the PspC-hpIgR mechanism depends on clathrin and dynamin. PspC recruits also Factor H to the pneumococcal cell surface. Consequently, the impact of pneumococcal cell surface bound Factor H on adherence to host cells and the molecular mechanism facilitating the uptake of Factor H bound pneumococci by epithelial cells was investigated. Flow cytometry and immunoblots revealed that S. pneumoniae has evolved the ability to recruit both purified Factor H as well as Factor H from human plasma or serum. Moreover, it was demonstrated that the recruitment of Factor H is independent of the PspC-subtypes and that capsular polysaccharide (CPS) interferes with its recruitment. Factor H bound to pneumococci significantly increased bacterial attachment to and invasion of host epithelial cells including nasopharyngeal cells (Detroit562), lung epithelial cells (A549), and human brain-derived endothelial cells (HBMEC). Blocking experiments demonstrated that bacteria bound Factor H interacts via the heparin binding sites on Factor H with eukaryotic cell surface glycosaminoglycans and that this interaction promotes pneumococcal adherence to host cells. In addition, inhibition studies with mAbs recognizing specifically different short consensus repeats (SCR) of Factor H suggested that SCR 19-20 of Factor H are essential for the pneumococcal interaction with host epithelial cells via Factor H. In the presence of Factor H, attachment of pneumococci to human polymorphonuclear leukocytes (PMNs) is enhanced. The integrin CD11b/CD18 was identified as the cellular receptor on PMNs. By using pharmacological inhibitors the impact of host cell cytoskeleton and signalling molecules, such as PTKs and PI3-kinase, for Factor H-mediated pneumococcal internalization into eukaryotic cells was shown. Taken together, the results revealed that Factor-H mediated pneumococcal infection requires a concerted role of host epithelial cell surface glycosaminoglycans, integrins and host cell signalling pathways.
During a study of the nutritional requirements of clinical isolates of Escherichia coli, we found that 21 (7.0%) of 301 strains required nicotinamide to grow in minimal medium. The nicotinamide- requiring strains were present in 16 (15.8%) of 101 cultures of urine from young women with acute cystitis, in 5 (5.0%) of 100 stool specimens from healthy adults, and in none of 100 blood samples from adult patients with bacteremia. Most of the strains belonged to serogroup OI8:KI:H7, were hemolytic, possessed type I fimbriae, and exhibited similar patterns of antibiotic susceptibility. Two of the urinary isolates expressed S fimbriae, and all 16 urinary isolates contained the s/aS homologue gene on their chromosomes. One of the stool isolates contained the s/aS gene. The urinary isolates closely resembled a large clone of E. coli that is reportedly associated with neonatal meningitis and sepsis. It may be possible to detect this and related clones by their requirement for nicotinamide and to screen strains for S fimbriae by relatively inexpensive hemagglutination methods, including the use of avian PI antigens to detect mannose- resistant, non-P-fimbriated E. coli; the agglutination of bovine erythrocytes; and the use of bovine mucin to detect sialyl galactosides in S fimbriae.
Over a period of 3 years, Legionella pneumophila serogroup 6 strains were isolated from warm water outlets and dental units in the Dental Faculty and from the Surgery and Internal Medicine Clinics at the University of Dresden, Dresden, Germany. In the bacteriological unit of the above-mentioned facility, L. pneumophila serogroups 3 and 12 were grown frl,)m warm water specimens. The medical facilities are located in separate buildings connected with a ring pipe warm water system. All L. pneumophila serogroup 6 strains isolated from the warm water supply reacted with a serogroup-specific monoclonal antibody, but not with two other monoclonal antibodies which are subgroup specific, reacting with other serogroup 6 strains. The NolI genomic profiles obtained by pulsed-field gel electrophoresis of 25 serogroup 6 strains isolated from the Dental Faculty over a 3-year period, 1 isolate from the Internal Medicine Clinic, and 4 strains from the Surgery Clinic were identical. Furthermore, all these strains hybridized with a 3OO-kb NolI fragment when a legiolysin (lIy)-specific DNA probe was used. The NolI pattern, however, differed from those of six serogroup 6 strains of other origins, one serogroup 12 strain from the bacteriological unit, and another six unrelated strains of serogroups other than serogroup 6. L. pneumophila serogroup 6 strains which can be divided into only two subgroups by the use of monoclonal antibodies are differentiated in at least six Noli cleavage types obtained by pulsed-field electrophoresis.
F 1 C fimbriae allow uropathogenic Escherichia coli to adhere to specific epithelial surfaces. This adhesive property is probably due to the presence of minor fimbrial components in F1C fimbriae. The foe gene cluster encoding F1C fimbriae has been cloned, as described previously. Here we present the nucleotide sequence (2081 bp) coding for the F 1 C minor fimbria I subunits. The structural genes code for polypeptides of 175 (FocF), 166 (FocG), and 300 (FocH) amino acids. The deduced amino acids of the F 1 C minor subunits were compared with the reported sequences of the minor subunits of other types of fimbriae. The data show that the Foc minor subunits are highly homologous to the corresponding Sfa proteins, whereas homology to the minor subunits of type 1 and P fimbriae is much lower.
The \(\alpha\)-Sialyl-\(\beta\) 2-3-Galactosyl-specific adhesin (S adhesin) was isolated from cells of a recombinant Escherichia coli K-12 strain expressing the S-flmbrial adhesin complex. A crude cell extract was partiaUy dissociated into fimbriae and an adhesin-enriched fraction by heating to 7O°C. From the latter, adhesin was purified to apparent homogeneity (by fast protein liquid chromatography, immunoblot, and NaDodSO\(_4\)/PAGE) by differential ammonium sulfate precipitation, dissociation in 8 M guanidine hydrochloride, and high-resolution anion-exchange chromatography in 8 M urea. The purified adhesin formed an aggregate of M\(_r\)\(\approx\)10\(^6\) that was made up of one type of 12-kDa polypeptide (fimbrillin is 16.5 kDa). It had pI value of 4.7 (fimbriae has a pI value of 6). Adhesin and fimbrillin had different amino add compositions. The purified adhesins agglutinated human and bovine erythrocytes with the same speclfkity as the whole bacteria; purified fimbriae were not adhesive. Monoclonal anti-adhesin and anti-fimbriae antibodies were obtained. Monoclonal antiadhesin, but none of the anti-fimbriae, antibodies inhibited the agglutination of erythrocytes. The anti-adhesive antibodies were used in immuno-gold electron microscopy to localize adhesin exclusively on the fimbriae, with a possible preference to their tips.
Results of molecular and pathogenic studies of three different bacterial hemolysins (cytolysins) are presented. These exoproteins derive from the two gram-negative bacteria Escherichia coli and Aeromonas hydrophila and from the gram-positive pathogen Listeria monocytogenes. The hemolysin of E. coli is determined by an 8-kilobase (kb) region that includes four clustered genes (hlyC, hlyA, hlyB, and hlyD). This hemolysin determinant is part either of large transmissible plasmids or of the chromosome. The genes located chromosomally are found predominantly in E. coli strains that can cause pyelonephritis and/or other extraintestinal infections. A detailed analysis of the chromosomal hly determinants of one nephropathogenic E. coli strain revealed the existence of specific, large chromosomal insertions 75 kb and lOO kb in size that carry the hly genes but that also influence the expression of other virulence properties, i.e., adhesion and serum resistance. The direct involvement of E. coli hemolysin in virulence could be demonstrated in several model systems. The genetic determinants for hemolysin (cytolysin) formation in , A. hydrophila (aerolysin) and L. monocytogenes (listeriolysin) are less complex. Both cytolysins seem to be encoded by single genes, although two loci (aerB and aerC) that affect the expression and activity of aerolysin have been identified distal and proximal to the structural gene for aerolysin (aerA). Cytolysin-negative mutants of both bacteria were obtained by site-specific deletion and/or transposon mutagenesis. These mutants show a drastic reduction in the virulence of the respective bacteria.
A new mouse model for systemic infection with Escherichia coli is presented. Whereas in other models 107_108 bacteria have to be injected into an animal to induce toxic effects resulting in death within 24 hours, now, only 103_104 bacteria of an appropriate strain are required to produce a genuine infection characterized by an increase in the bacterial load over several days. The quantitative determination of bacterial counts per liver allows a more sensitive measurement than recording death rates. Furthermore, few animals are required for a definite result in contrast to the LDso determination of other models. The salient point regarding this new model is that conditioning of animals has to be achieved by incorporating the inoculum into agar which is injected subcutaneously. The resulting infection is completely dependent on the E. colicondistrain used. Whereas a hemolytic, uropathogenic strain is so virulent that an overwhelming infection develops within 48 hours after the injection of 103 bacterial cells, a non-hemolytic variant of this strain is completely avirulent, being unable to multiply in spite of the potentiating agar. The hemolytic E. coli strain ATCC 25922 is intermediate in virulence. The bacterial counts per liver increase steadily until death occurs five to seven days after the injection of 104 bacteria. This bacterial infection can be therapeutically influenced by daily treatment with various drugs. Ciprofloxacin, ceftriaxone and co-trimoxazole are able to cure the infection, whereas amoxicillin given orally is only moderately active against this ATCC strain, which is relatively resistant to amoxicillin.
Like all other Salmonella typhimurium strains examined, the smooth variants SF1397 (L T2) and 1366 and also their semi-rough and rough derivatives are non-haemolytic. Nevertheless, two haemolysin (Hly) plasmids of E. coli belonging to the inc groups incFllI,lv (pSU316) and incIz (pHly152) were able to be introduced into these strains by conjugation and stably maintained. A considerable percentage of the Hly+ transconjugants obtained had lost parts of their O-side chains, a result of selection for the better recipient capability of « semi-rough» variants rather than the direct influence of the Hly+ plasmids themselves. In contrast to the incF1lI1V plasmid pSU316, which exhibited higher conjugation rates with rough recipients, the incIz plasmid pHly152 was accepted best by smooth strains. Transformation with cloned E. coli haemolysin (hly) determinant was inefficient ( <10-8) for smooth strains, but 102-103 times higher for rough recipients, and was increased by the use of Salmonella-modified DNA. The transform ants and transconjugants were relatively stable and showed the same haemolytic activity as the E. coli donor strains. The virulence of the Hly+ smooth, semi-rough and rough S. typhimurium strains was tested in two mouse models, and neither the mortality rate nor the ability to multiply within the mouse spleen was influenced by the hly determinants.
The 06 serogroup Escherichia coli strain 536 carries two hemolysin (hly) determinants integrated into the chromosome. The two hly determinants are not completely identical, either functionally or structurally, as demonstrated by spontaneous deletion mutants carrying only one of them and by cloning each of the two determinants separately into cosmid vectors. Each hly determinant is independently deleted at a frequency of 10-4 , leading to variants which exhibit similar levels of internal hemolysin but different amounts of secreted hemolysin. The two hly determinants were also identified in the 04 E. coli strain 519. The three E. coli strains 251, 764, and 768, which belong to the serogroup 018, and the 04 strain 367 harbor a single chromosomal hly determinant, as demonstrated by hybridization with hly-gene-specific probes. However, a hybridization probe derived from a sequence adjacent to the hlyC-proximal end of the plasmid pHlyl52-encoded hly determinant hybridizes with several additional chromosomal bands in hemolytic 018 and 06 E. coli strains and even in E. coli K-12. The size ofthe probe causing the multiple hybridization suggests a 1,500- to 1,800-base pair sequence directly flanking hlyC. Spontaneous hemolysin-negative mutants were isolated from strains 764 and 768, which had lost the entire hly determinant but retained all copies of the hlyC-associated sequence. This sequence is not identical to a previously identified (J. Hacker, S. Knapp, and W. Goebel, J. Bacteriol. 154:1145-1154, 1983) somewhat smaller (about 850 base pairs) sequence flanking the other (hlyBb-proximal) end of the plasmid pHlyl52-encoded hly determinant which, as shown here, exists also in multiple copies in these hemolytic E. coli strains and in at least two copies in E. coli K-12. In contrast to the plasmid-encoded hly determinant which is directly flanked at both ends by these two diJJerent sequences, the chromosomal hly determinants are not immediately flanked by such sequences.
The hemolytic Escherichia coli strain 536 (06) propagates spontaneous hemolysin- negative mutants at relatively high rates (10-3 to 10-4 ). One type of mutant (type I) lacks both secreted (external) and periplasmic (internal) hemolysin activity (HlYex - IHlYin -) and in addition shows no mannose-resistant hemagglutination (Mrh -), whereas the other type (type II) is HlYex -IHIYin + and Mrh +. The genetic determinants for hemolysin production (hly) and for mannose-resistant hemagglutination (mrh) of this strain are located on the chromosome. Hybridization experiments with DNA probes specific for various parts of the hly determinant reveal that mutants of type I have lost the total hly determinant, whereas those of type 11 lack only part of the hlyB that is essential for transport of hemolysin across the outer membrane. Using a probe that contains the end sequence of the plasmid pHly152-encoded hly determinant (adjacent to hlyB), we determined that a related sequence flanks also the hlyB-distal end of the chromosomal hly determinant of E. coli 536. In addition several other similar or even identical sequences are found in the vicinity of the hlyC- and the hlyB-distal ends of both the chromosomal and the plasmid hly determinants.
We have cloned the chromosomal hemolysin determinants from Escherichia coli strains belonging to the four O-serotypes 04, 06, 018, and 075, The hemolysin-producing clones were isolated from gene banks of these strains which were constructed by inserting partial Sau3A fragments of chromosomal DNA into the cosmid pJC74. The hemolytic cosmid clones were relatively stable. The inserts were further sub cloned either as Sail fragments in pACYC184 or as BamHI-SaLI fragments in a recombinant plasmid (pANN202) containing cistron C (hlye) of the plasmid-encoded hemolysin determinant. Detailed restriction maps of each of these determinants were constructed, and it was found that, despite sharing overall homology, the determinants exhibited minor specific differences in their structure, These appeared to be restricted to cistron A (hlyA), which is the structural gene for hemolysin. In the gene banks of two of these hemolytic strains, we could also identify clones which carried the genetic determinants for the mannose-resistant hemagglutination antigens Vb and VIc. Both of these fimbrial antigens were expressed in the E. coli K-12 clones to an extent similar to that observed in the wild-type strains. These recombinant cosmids were rather unstable, and, in the absence of selection, segregated at a high frequency.