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Expression of human foamy virus is differentially regulated during development in transgenic mice
(1992)
Tbe human foamy virus (HFV) is a recently characterized member ofthe spumavirus family. Although no diseases have been unequivocally associated with HFV infection, expression of HFV regulatory genes in transgenie mice induces a characteristic aeute neuro degenerative disease and a myopathy. To better eharaeterize the sequenee of events leading to disease, and to gain a better understanding of the underlying pathogenetic meehanisms, we have analyzed in detail the transgene expression pattern during development. Transcription of a construet containing all regulatory elements and aneillary genes of mv was analyzed by in situ hybridization and was shown to occur in two distinct phases. At midgestation, low but widespread expression was first deteeted in eells of extraembryonie tissues. Later, various tissues originating from embryonie mesoderm, neuroeetoderm, and neural erest transeribed the transgene at moderate levels. However, expression deereased dramatically during late gestation and was suppressed shortly after birth. After a latency period of up to 5 weeks, transeription of the transgene resumed in single eelJs distributed irregularly in the central nervous system and in the skeletal museIe. By the age of 8 weeks, an increasing number of eells displayed much higher expression levels than in embryonie Iife and eventually underwent severe degenerative ehanges. These findings demonstrate that HFV transgene expression is differentially regulated in development and that HFV cytotoxicity may be dose-dependent. Such biphasic pattern of expression differs from that of murine retroviruses and may be explained by the specificity of HFV regulatory elements in combination with cellular faetors. Future studies of this model system should, therefore, provide novel insights in the mechanisms controlling retrovirallatency.
Humanfoamy virus (HFV) is a retrovirus encoding structural genes and, like human immunodeficiency virus and human T ceU leukemia virus I, several anciUary reading frames collectively termed the belgenes. We have previously shown that HFV transgenic mice develop an encephalopathy with neuronal loss in hippocampus and cerebral cortex. We have now raised and characterized rabbit antisera to various recombinant portions of gag, pot, env, and bel-I, the viraltransactivator. Immunoreactivity for gag and bel-I was observed in nuclei and processes of hippocampal and cortical neurons before the onset of morphological lesions and correlated with the appearance of HFV mRNA. Astrocyte-derived multinucleated giant ceUs containing HFV proteins were present in the brain oftransgenic mice coexpressingfuU- length HFV genes but not in mice expressing truncated gag and env, suggesting that these genes contain afusogenic domain. Expression of fuU-length structural genes decreased the life expectancy oftransgenic mice, implying an a4Juvant rolefor these proteins in HFV-induced brain damage. (Am] Pathol 1993, 142:1061-1072)
Myeloid-derived suppressor cells (MDSC) represent major regulators of immune responses, which can control T cells via their inducible nitric oxide synthase (iNOS)- and arginase 1 (Arg1)-mediated effector functions. While GM-CSF is well documented to promote MDSC development, little is known about this potential of IL-3, an established growth factor for mast cells. Here, we show that IL-3, similar to GM-CSF, generates monocytic MDSC (M-MDSC) from murine bone marrow (BM) cells after 3 days of in vitro culture. At this time point, predominantly CD11b+ CD49a+ monocytic and CD11b+ CD49a- FcεR I- neutrophilic cells were detectable, while CD11blow/neg FcεR I+ mast cells accumulated only after extended culture periods. Both growth factors were equivalent in generating M-MDSC with respect to phenotype, cell yield and typical surface markers. However, IL-3 generated M-MDSC produced less TNF, IL-1β and IL-10 after activation with LPS + IFN-γ but showed higher Arg1 expression compared to GM-CSF generated M-MDSC. Arg1 was further induced together with iNOS after MDSC activation. Accordingly, an increased Arg1-dependent suppressor activity by the IL-3 generated M-MDSC was observed using respective iNOS and Arg1 inhibitors. Together, these data indicate that M-MDSC can be generated in vitro by IL-3, similar to GM-CSF, but with increased Arg1 expression and Arg1-mediated suppression capacity. This protocol now allows further in vitro studies on the role of IL-3 for MDSC biology.
Quantification of the peripheral nerve myelin glycoprotein PO and antibodies to PO is difficult due to insolubility of PO in physiological solutions. We have overcome this problern by using the water-soluble recombinant form of the extracellular domain of PO (PO-ED) and describe newly developed assays which allow detection and quantitation of PO and antibodies to PO, in serum and cerebraspinal fluid (CSF). These sensitive and specific assays based on the ELISA technique were used to study humoral immune responses to PO during experimental autoimmune ("allergic") neuritis (EAN). In order to establish these tests, monoclonal antiborlies to different epitopes of rodent and human PO-ED were produced. A two-antibody sandwich-ELISA allowing quantitation of PO Oower detection Iimit of 0.5 ngjml or 30 fmoljml) and an antibody-capture ELISA (lower detection Iimit 1 ng specific antibody jml) to detect antiborlies to PO in serum and CSF were developed. EAN was induced in rats by active immunization with bovine myelin or the neuritogenic protein P2 or by adoptive transfer using P2 specific CD4 positive T cells. Serum and CSF were assayed for the presence of PO-ED and antibodies to PO-ED or P2. Antibodies to PO-ED were detected during active myelin-induced EAN, but not during P2-induced or adaptive transfer EAN. The anti-PO-ED antibodies in the CSF showed a correJation with disease activity. In contrast, in the same model antibodies to P2 persisted long after the disease ceased. No soluble PO-Iike fragments could be found in serum or CSF during any of the three types of EAN. We conclude that PO may be a B-eeil epitope in EAN. These findings warrant a screen for antibodies to PO-ED in human immune neuropathies.
Seven monoclonal antibodies were raised against the immunoglobulin-like extracellular domain of PO (POED), the major protein of peripheral nervous system myelin. Mice were immunized with purified recombinant rat PO-ED. After fusion, 7 clones (POI-P07) recognizing either recombinant, rat, mouse, or human PO-ED were selected by ELlS A and were characterized by Western blot, immunohistochemistry, and a competition assay. Antibodies belonged to the IgG or IgM class, and P04-P07, reacted with PO in fresh-frozen and paraffin-embedded sections of human or rat peripheral nerve, but not with myelin proteins of the central nervous system of either species. Epitope specificity of the antibodies was determined by a competition enzyme-linked immunosorbent assay (ELISA) and a direct ELlS A using short synthetic peptides spanning the entire extracellular domain of PO. These assays showed that POl and P02 exhibiting the same reaction pattern in Western blot and immunohistochemistry reacted with different distant epitopes of PO. Furthermore, the monoclonal antibodies P05 and P06 recognized 2 different epitopes in close proximity within the neuritogenic extracellular sequence of PO. This panel of monoclonal antibodies, each binding to a different epitope of the extracellular domain of PO, will be useful for in vitro and in vivo studies designed to explore the role of PO during myelination and in demyelinating diseases of the peripheral nervous system.
Background: Mesenchymal stem cells (MSCs) and their chondrogenic differentiation have been extensively investigated in vitro as MSCs provide an attractive source besides chondrocytes for cartilage repair therapies. Here we established prototype foamyviral vectors (FVV) that are derived from apathogenic parent viruses and are characterized by a broad host range and a favorable integration pattern into the cellular genome. As the inflammatory cytokine interleukin 1 beta (IL1β) is frequently present in diseased joints, the protective effects of FVV expressing the human interleukin 1 receptor antagonist protein (IL1RA) were studied in an established in vitro model (aggregate culture system) of chondrogenesis in the presence of IL1β.
Materials and Methods: We generated different recombinant FVVs encoding enhanced green fluorescent protein (EGFP) or IL1RA and examined their transduction efficiencies and transgene expression profiles using different cell lines and human primary MSCs derived from bone marrow-aspirates. Transgene expression was evaluated by fluorescence microscopy (EGFP), flow cytometry (EGFP), and ELISA (IL1RA). For evaluation of the functionality of the IL1RA transgene to block the inhibitory effects of IL1β on chondrogenesis of primary MSCs and an immortalized MSC cell line (TERT4 cells), the cells were maintained following transduction as aggregate cultures in standard chondrogenic media in the presence or absence of IL1β. After 3 weeks of culture, pellets were harvested and analyzed by histology and immunohistochemistry for chondrogenic phenotypes.
Results: The different FVV efficiently transduced cell lines as well as primary MSCs, thereby reaching high transgene expression levels in 6-well plates with levels of around 100 ng/ml IL1RA. MSC aggregate cultures which were maintained in chondrogenic media without IL1β supplementation revealed a chondrogenic phenotype by means of strong positive staining for collagen type II and matrix proteoglycan (Alcian blue). Addition of IL1β was inhibitory to chondrogenesis in untreated control pellets. In contrast, foamyviral mediated IL1RA expression rescued the chondrogenesis in pellets cultured in the presence of IL1β. Transduced MSC pellets reached thereby very high IL1RA transgene expression levels with a peak of 1087 ng/ml after day 7, followed by a decrease to 194 ng/ml after day 21, while IL1RA concentrations of controls were permanently below 200 pg/ml.
Conclusion: Our results indicate that FVV are capable of efficient gene transfer to MSCs, while reaching IL1RA transgene expression levels, that were able to efficiently block the impacts of IL1β in vitro. FVV merit further investigation as a means to study the potential as a gene transfer tool for MSC based therapies for cartilage repair.
Sphingolipids are essential components of eukaryotic cells. In this review, we want to exemplarily illustrate what is known about the interactions of sphingolipids with various viruses at different steps of their replication cycles. This includes structural interactions during entry at the plasma membrane or endosomal membranes, early interactions leading to sphingolipid-mediated signal transduction, interactions with internal membranes and lipids during replication, and interactions during virus assembly and budding. Targeted interventions in sphingolipid metabolism – as far as they can be tolerated by cells and organisms – may open novel possibilities to support antiviral therapies. Human immunodeficiency virus type 1 (HIV-1) infections have intensively been studied, but for other viral infections, such as influenza A virus (IAV), measles virus (MV), hepatitis C virus (HCV), dengue virus, Ebola virus, and severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), investigations are still in their beginnings. As many inhibitors of sphingolipid metabolism are already in clinical use against other diseases, repurposing studies for applications in some viral infections appear to be a promising approach.
Sphingolipids are major components of cellular membranes, and at steady-state level, their metabolic fluxes are tightly controlled. On challenge by external signals, they undergo rapid turnover, which substantially affects the biophysical properties of membrane lipid and protein compartments and, consequently, signaling and morphodynamics. In T cells, external cues translate into formation of membrane microdomains where proximal signaling platforms essential for metabolic reprograming and cytoskeletal reorganization are organized. This review will focus on sphingomyelinases, which mediate sphingomyelin breakdown and ensuing ceramide release that have been implicated in T-cell viability and function. Acting at the sphingomyelin pool at the extrafacial or cytosolic leaflet of cellular membranes, acid and neutral sphingomyelinases organize ceramide-enriched membrane microdomains that regulate T-cell homeostatic activity and, upon stimulation, compartmentalize receptors, membrane proximal signaling complexes, and cytoskeletal dynamics as essential for initiating T-cell motility and interaction with endothelia and antigen-presenting cells. Prominent examples to be discussed in this review include death receptor family members, integrins, CD3, and CD28 and their associated signalosomes. Progress made with regard to experimental tools has greatly aided our understanding of the role of bioactive sphingolipids in T-cell biology at a molecular level and of targets explored by a model pathogen (measles virus) to specifically interfere with their physiological activity.
In common with most viruses, measles virus (MV) relies on the integrity of the cytoskeleton of its host cells both with regard to efficient replication in these cells, but also retention of their motility which favors viral dissemination. It is, however, the surface interaction of the viral glycoprotein (gp) complex with receptors present on lymphocytes and dendritic cells (DCs), that signals effective initiation of host cell cytoskeletal dynamics. For DCs, these may act to regulate processes as diverse as viral uptake and sorting, but also the ability of these cells to successfully establish and maintain functional immune synapses (IS) with T cells. In T cells, MV signaling causes actin cytoskeletal paralysis associated with a loss of polarization, adhesion and motility, which has been linked to activation of sphingomyelinases and subsequent accumulation of membrane ceramides. MV modulation of both DC and T cell cytoskeletal dynamics may be important for the understanding of MV immunosuppression at the cellular level.
As pattern recognition receptor on dendritic cells (DCs), DC-SIGN binds carbohydrate structures on its pathogen ligands and essentially determines host pathogen interactions because it both skews T cell responses and enhances pathogen uptake for cis infection and/or T cell trans-infection. How these processes are initiated at the plasma membrane level is poorly understood. We now show that DC-SIGN ligation on DCs by antibodies, mannan or measles virus (MV) causes rapid activation of neutral and acid sphingomyelinases followed by accumulation of ceramides in the outer membrane leaflet. SMase activation is important in promoting DC-SIGN signaling, but also for enhancement of MV uptake into DCs. DCSIGN-dependent SMase activation induces efficient, transient recruitment of CD150, which functions both as MV uptake receptor and microbial sensor, from an intracellular Lamp-1+ storage compartment shared with acid sphingomyelinase (ASM) within a few minutes. Subsequently, CD150 is displayed at the cell surface and co-clusters with DC-SIGN. Thus, DCSIGN ligation initiates SMase-dependent formation of ceramide-enriched membrane microdomains which promote vertical segregation of CD150 from intracellular storage compartments along with ASM. Given the ability to promote receptor and signalosome co-segration into (or exclusion from) ceramide enriched microdomains which provide a favorable environment for membrane fusion, DC-SIGN-dependent SMase activation may be of general importance for modes and efficiency of pathogen uptake into DCs, and their routing to specific compartments, but also for modulating T cell responses.
Measles virus (MV) efficiently causes generalized immunosuppression which accounts to a major extent for cases of measles-asscociated severe morbidity and mortality. MV infections alter many functions of antigen presenting cells (APC) (dendritic cells (DCs)) and lymphocytes, yet many molecular targets of the virus remain poorly defined. Cellular interactions and effector functions of DCs and lymphocytes are regulated by surface receptors. Associating with other proteins involved in cell signaling, receptors form part of receptosomes that respond to and transmit external signals through dynamic interctions with the cytoskeleton. Alterations in the composition and metabolism of membrane sphingolipids have a substantial impact on both processes. In this review we focus on the regulation of sphingomyelinase activity and ceramide release in cells exposed to MV and discuss the immunosuppressive role of sphingomyelin breakdown induced by MV.
Background
Regulatory CD4\(^+\)CD25\(^+\)FoxP3\(^+\) T cells (Treg) are a subgroup of T lymphocytes involved in maintaining immune balance. Disturbance of Treg number and impaired suppressive function of Treg correlate with Parkinson’s disease severity. Superagonistic anti-CD28 monoclonal antibodies (CD28SA) activate Treg and cause their expansion to create an anti-inflammatory environment.
Methods
Using the AAV1/2-A53T-α-synuclein Parkinson’s disease mouse model that overexpresses the pathogenic human A53T-α-synuclein (hαSyn) variant in dopaminergic neurons of the substantia nigra, we assessed the neuroprotective and disease-modifying efficacy of a single intraperitoneal dose of CD28SA given at an early disease stage.
Results
CD28SA led to Treg expansion 3 days after delivery in hαSyn Parkinson’s disease mice. At this timepoint, an early pro-inflammation was observed in vehicle-treated hαSyn Parkinson’s disease mice with elevated percentages of CD8\(^+\)CD69\(^+\) T cells in brain and increased levels of interleukin-2 (IL-2) in the cervical lymph nodes and spleen. These immune responses were suppressed in CD28SA-treated hαSyn Parkinson’s disease mice. Early treatment with CD28SA attenuated dopaminergic neurodegeneration in the SN of hαSyn Parkinson’s disease mice accompanied with reduced brain numbers of activated CD4\(^+\), CD8\(^+\) T cells and CD11b\(^+\) microglia observed at the late disease-stage 10 weeks after AAV injection. In contrast, a later treatment 4 weeks after AAV delivery failed to reduce dopaminergic neurodegeneration.
Conclusions
Our data indicate that immune modulation by Treg expansion at a timepoint of overt inflammation is effective for treatment of hαSyn Parkinson’s disease mice and suggest that the concept of early immune therapy could pose a disease-modifying option for Parkinson’s disease patients.
Wiskott–Aldrich syndrome (WAS) is caused by loss-of-function mutations in theWASp gene.
Decreased cellular responses in WASp-deficient cells have been interpreted to mean that
WASp directly regulates these responses in WASp-sufficient cells. Here, we identify an
exception to this concept and show that WASp-deficient dendritic cells have increased
activation of Rac2 that support cross-presentation to CD8þ T cells. Using two different skin
pathology models, WASp-deficient mice show an accumulation of dendritic cells in the skin
and increased expansion of IFNg-producing CD8þ T cells in the draining lymph node and
spleen. Specific deletion of WASp in dendritic cells leads to marked expansion of CD8þ
T cells at the expense of CD4þ T cells. WASp-deficient dendritic cells induce increased
cross-presentation to CD8þ T cells by activating Rac2 that maintains a near neutral pH of
phagosomes. Our data reveals an intricate balance between activation of WASp and Rac2
signalling pathways in dendritic cells.
Several new N-substituted 1,2-benzisothiazol-3(2H)-ones (BITs) were synthesised through a facile synthetic route for testing their anti-dengue protease inhibition. Contrary to the conventional multistep synthesis, we achieved structurally diverse BITs with excellent yields using a two-step, one-pot reaction strategy. All the synthesised compounds were prescreened for drug-like properties using the online Swiss Absorption, Distribution, Metabolism and Elimination (SwissADME) model, indicating their favourable pharmaceutical properties. Thus, the synthesised BITs were tested for inhibitory activity against the recombinant dengue virus serotype-2 (DENV-2) NS2BNS3 protease. Dose–response experiments and computational docking analyses revealed that several BITs bind to the protease in the vicinity of the catalytic triad with IC\(_{50}\) values in the micromolar range. The DENV2 infection assay showed that two BITs, 2-(2-chlorophenyl)benzo[d]isothiazol-3(2H)-one and 2-(2,6-dichlorophenyl)benzo[d]isothiazol-3(2H)-one, could suppress DENV replication and virus infectivity. These results indicate the potential of BITs for developing new anti-dengue therapeutics.
Background: Kerinokeratosis papulosa (KP) is considered an extremely rare genodermatosis presenting usually as waxy papules on the trunk in childhood.
Objective: To describe and analyze the clinical, histological and potential etiopathological aspects of KP.
Methods: The dermatoscopic features of a new case of KP of childhood are investigated. The presence of human papillomavirus (HPV) DNA in lesional skin was studied by polymerase chain reaction. Furthermore, all cases of KP of childhood reported so far were reviewed.
Results: As a diagnostic tool, we describe for the first time a dermatoscopic feature, namely a cribriform pattern of KP, in an 11-year-old boy. In addition, we detected HPV (type 57) in his KP lesions.
Conclusions: Dermatoscopic examination might be a useful tool to distinguish KP from other skin lesions, e.g. common warts. The detection of HPV type 57 might hint to an etiological role of HPV for KP.
Hsp90 inhibition ameliorates CD4\(^{+}\) T cell-mediated acute Graft versus Host disease in mice
(2016)
Introduction:
For many patients with leukemia only allogeneic bone marrow transplantion provides a chance of cure. Co‐transplanted mature donor T cells mediate the desired Graft versus Tumor (GvT) effect required to destroy residual leukemic cells. The donor T cells very often, however, also attack healthy tissue of the patient inducing acute Graft versus Host Disease (aGvHD)—a potentially life‐threatening complication.
Methods:
Therefore, we used the well established C57BL/6 into BALB/c mouse aGvHD model to evaluate whether pharmacological inhibition of heat shock protein 90 (Hsp90) would protect the mice from aGvHD.
Results:
Treatment of the BALB/c recipient mice from day 0 to +2 after allogeneic CD4\(^{+}\) T cell transplantation with the Hsp90 inhibitor 17‐(dimethylaminoethylamino)‐17‐demethoxygeldanamycin (DMAG) partially protected the mice from aGvHD. DMAG treatment was, however, insufficient to prolong overall survival of leukemia‐bearing mice after transplantation of allogeneic CD4\(^{+}\) and CD8\(^{+}\) T cells. Ex vivo analyses and in vitro experiments revealed that DMAG primarily inhibits conventional CD4\(^{+}\) T cells with a relative resistance of CD4\(^{+}\) regulatory and CD8\(^{+}\) T cells toward Hsp90 inhibition.
Conclusions:
Our data, thus, suggest that Hsp90 inhibition might constitute a novel approach to reduce aGvHD in patients without abrogating the desired GvT effect.
Opportunistic infections with the saprophytic yeast Candida albicans are a major cause of morbidity in immunocompromised patients. While the interaction of cells and molecules of innate immunity with C. albicans has been studied to great depth, comparatively little is known about the modulation of adaptive immunity by C. albicans. In particular, direct interaction of proteins secreted by C. albicans with CD4\(^{+}\) T cells has not been studied in detail. In a first screening approach, we identified the pH-regulated antigen 1 (Pra1) as a molecule capable of directly binding to mouse CD4\(^{+}\) T cells in vitro. Binding of Pra1 to the T cell surface was enhanced by extracellular Zn\(^{2+}\) ions which Pra1 is known to scavenge from the host in order to supply the fungus with Zn\(^{2+}\). In vitro stimulation assays using highly purified mouse CD4\(^{+}\) T cells showed that Pra1 increased proliferation of CD4\(^{+}\) T cells in the presence of plate-bound anti-CD3 monoclonal antibody. In contrast, secretion of effector cytokines such as IFNγ and TNF by CD4\(^{+}\) T cells upon anti-CD3/ anti-CD28 mAb as well as cognate antigen stimulation was reduced in the presence of Pra1. By secreting Pra1 C. albicans, thus, directly modulates and partially controls CD4\(^{+}\) T cell responses as shown in our in vitro assays.
Peripheral T cell lymphomas (PTCLs) are associated with a poor prognosis due to often advanced disease at the time of diagnosis and due to a lack of efficient therapeutic options. Therefore, appropriate animal models of PTCL are vital to improve clinical management of this disease. Here, we describe a monoclonal CD8\(^+\) CD4\(^−\) αβ T cell receptor Vβ2\(^+\) CD28\(^+\) T cell lymphoma line, termed T8-28. T8-28 cells were isolated from an un-manipulated adult BALB/c mouse housed under standard pathogen-free conditions. T8-28 cells induced terminal malignancy upon adoptive transfer into syngeneic BALB/c mice. Despite intracellular expression of the cytotoxic T cell differentiation marker granzyme B, T8-28 cells appeared to be defective with respect to cytotoxic activity as read-out in vitro. Among the protocols tested, only addition of interleukin 2 in vitro could partially compensate for the in vivo micro-milieu in promoting growth of the T8-28 lymphoma cells.
Recent evidence indicates that foamy viruses (FVs) are the oldest retroviruses (RVs) that we know and coevolved with their hosts for several hundred million years. This coevolution may have contributed to the non-pathogenicity of FVs, an important factor in development of foamy viral vectors in gene therapy. However, various questions on the molecular evolution of FVs remain still unanswered. The analysis of the spectrum of animal species infected by exogenous FVs or harboring endogenous FV elements in their genome is pivotal. Furthermore, animal studies might reveal important issues, such as the identification of the FV in vivo target cells, which than require a detailed characterization, to resolve the molecular basis of the accuracy with which FVs copy their genome. The issues of the extent of FV viremia and of the nature of the virion genome (RNA vs. DNA) also need to be experimentally addressed.
Background
During reverse transcription, retroviruses duplicate the long terminal repeats (LTRs). These identical LTRs carry both promoter regions and functional polyadenylation sites. To express full-length transcripts, retroviruses have to suppress polyadenylation in the 5′LTR and activate polyadenylation in the 3′LTR. Foamy viruses have a unique LTR structure with respect to the location of the major splice donor (MSD), which is located upstream of the polyadenylation signal.
Results
Here, we describe the mechanisms of foamy viruses regulating polyadenylation. We show that binding of the U1 small nuclear ribonucleoprotein (U1snRNP) to the MSD suppresses polyadenylation at the 5′LTR. In contrast, polyadenylation at the 3′LTR is achieved by adoption of a different RNA structure at the MSD region, which blocks U1snRNP binding and furthers RNA cleavage and subsequent polyadenylation.
Conclusion
Recently, it was shown that U1snRNP is able to suppress the usage of intronic cryptic polyadenylation sites in the cellular genome. Foamy viruses take advantage of this surveillance mechanism to suppress premature polyadenylation at the 5’end of their RNA. At the 3’end, Foamy viruses use a secondary structure to presumably block access of U1snRNP and thereby activate polyadenylation at the end of the genome. Our data reveal a contribution of U1snRNP to cellular polyadenylation site selection and to the regulation of gene expression.
Despite recent therapeutic advances the prognosis of heart failure remains poor. Recent research suggests that heart failure is a heterogeneous syndrome and that many patients have stimulating auto-antibodies directed against the second extracellular loop of the \(β_1\) adrenergic receptor \((β_1EC2)\). In a human-analogous rat model such antibodies cause myocyte damage and heart failure. Here we used this model to test a novel antibody-directed strategy aiming to prevent and/or treat antibody-induced cardiomyopathy. To generate heart failure, we immunised n = 76/114 rats with a fusion protein containing the human β1EC2 (amino-acids 195–225) every 4 weeks; n = 38/114 rats were control-injected with 0.9% NaCl. Intravenous application of a novel cyclic peptide mimicking \(β_1EC2\) (\(β_1EC2-CP\), 1.0 mg/kg every 4 weeks) or administration of the \(β_1-blocker\) bisoprolol (15 mg/kg/day orally) was initiated either 6 weeks (cardiac function still normal, prevention-study, n = 24 (16 treated vs. 8 untreated)) or 8.5 months after the 1st immunisation (onset of cardiomyopathy, therapy-study, n = 52 (40 treated vs. 12 untreated)); n = 8/52 rats from the therapy-study received \(β_1EC2-CP/bisoprolol\) co-treatment. We found that \(β_1EC2-CP\) prevented and (alone or as add-on drug) treated antibody-induced cardiac damage in the rat, and that its efficacy was superior to mono-treatment with bisoprolol, a standard drug in heart failure. While bisoprolol mono-therapy was able to stop disease-progression, \(β_1EC2-CP\) mono-therapy -or as an add-on to bisoprolol- almost fully reversed antibody-induced cardiac damage. The cyclo¬peptide acted both by scavenging free \(anti-β_1EC2-antibodies\) and by targeting \(β_1EC2\)-specific memory B-cells involved in antibody-production. Our model provides the basis for the clinical translation of a novel double-acting therapeutic strategy that scavenges harmful \(anti-β_1EC2-antibodies\) and also selectively depletes memory B-cells involved in the production of such antibodies. Treatment with immuno-modulating cyclopeptides alone or as an add-on to \(β_1\)-blockade represents a promising new therapeutic option in immune-mediated heart failure.
Progressive encephalopathy and myopathy in transgenic mice expressing human foamy virus genes
(1991)
Transgenie mice carrying the bel region of human foamy retrovirus (HFV) under transcriptional control of its own long terminal repeat expressed tbe transgene in their centrat nervous systems and in smootb and striated muscle tissues. The animals developed a progressive degenerative disease of tbe centrat nervous system and of the striated muscle. Because expression of tbe transgene was dosely correlated witb the appearance of structural damage and inflammatory reactions were scanty, the disease is likely to be caused directly by tbe HFV proteins. These unexpected findings call for a reevaluation of tbe patbogenic potential of HFV in humans.
Transforming growth factor \(\beta\) (TGF-\(\beta\)) has a growth-inhibitory effect on numerous different cell types of the immune system, including T lymphocytes. We show in this study that the inhibitory action of TGF-\(\beta\) on T lymphocytes is accompanied by a block of interleukin 2 (IL-2) gene expression which is mediated, at least in part, by inhibition of IL-2 promoter/enhancer activity. The functional analysis of cis-regulatory (protoenhancer) elements of the IL-2 enhancer/promoter region showed that the most TGF-\(\beta\)-responsive element maps to its so-called upstream promoter site. The proto-enhancer activity of the upstream promoter site element is also inhibited by cyclosporin A. The upstream promoter site DNA harbors two noncanonical, closely linked binding sequences for octamer and AP-1-like factors. Both sites are involved in the establishment of IL-2 enhancer activity. Since the activity of genuine octamer sites but not that of AP-1-binding sites is also impaired by TGF-\(\beta\) and cyclosporin A in E14 T lymphoma cells, we conclude that both immunosuppressives interfere with the activity but not the DNA binding of octamer factors in T lymphocytes.
Background: Dendritic cells (DC) can act tolerogenic at a semi-mature stage by induction of protective CD4+ T cell and NKT cell responses. Methodology/Principal Findings: Here we studied the role of the co-inhibitory molecule B7-H1 (PD-L1, CD274) on semimature DC that were generated from bone marrow (BM) cells of B7-H12/2 mice and applied to the model of Experimental Autoimmune Encephalomyelitis (EAE). Injections of B7-H1-deficient DC showed increased EAE protection as compared to wild type (WT)-DC. Injections of B7-H12/2 TNF-DC induced higher release of peptide-specific IL-10 and IL-13 after restimulation in vitro together with elevated serum cytokines IL-4 and IL-13 produced by NKT cells, and reduced IL-17 and IFN-c production in the CNS. Experiments in CD1d2/2 and Ja2812/2 mice as well as with type I and II NKT cell lines indicated that only type II NKT cells but not type I NKT cells (invariant NKT cells) could be stimulated by an endogenous CD1d-ligand on DC and were responsible for the increased serum cytokine production in the absence of B7-H1. Conclusions/Significance: Together, our data indicate that BM-DC express an endogenous CD1d ligand and B7-H1 to ihibit type II but not type I NKT cells. In the absence of B7-H1 on these DC their tolerogenic potential to stimulate tolerogenic CD4+ and NKT cell responses is enhanced.
Intrathecal, Polyspecific Antiviral Immune Response in Oligoclonal Band Negative Multiple Sclerosis
(2012)
Background: Oligoclonal bands (OCB) are detected in the cerebrospinal fluid (CSF) in more than 95% of patients with multiple sclerosis (MS) in the Western hemisphere. Here we evaluated the intrathecal, polyspecific antiviral immune response as a potential diagnostic CSF marker for OCB-negative MS patients.
Methodology/Principal Findings: We tested 46 OCB-negative German patients with paraclinically well defined, definite MS. Sixteen OCB-negative patients with a clear diagnosis of other autoimmune CNS disorders and 37 neurological patients without evidence for autoimmune CNS inflammation served as control groups. Antibodies against measles, rubella, varicella zoster and herpes simplex virus in paired serum and CSF samples were determined by ELISA, and virus-specific immunoglobulin G antibody indices were calculated. An intrathecal antibody synthesis against at least one neurotropic virus was detected in 8 of 26 (31%) patients with relapsing-remitting MS, 8 of 12 (67%) with secondary progressive MS and 5 of 8 (63%) with primary progressive MS, in 3 of 16 (19%) CNS autoimmune and 3 of 37 (8%) non-autoimmune control patients. Antibody synthesis against two or more viruses was found in 11 of 46 (24%) MS patients but in neither of the two control groups. On average, MS patients with a positive antiviral immune response were older and had a longer disease duration than those without.
Conclusion: Determination of the intrathecal, polyspecific antiviral immune response may allow to establish a CSF-supported diagnosis of MS in OCB-negative patients when two or more of the four virus antibody indices are elevated.
Background
Alveolar echinococcosis (AE), caused by the metacestode of the tapeworm Echinococcus multilocularis, is a lethal zoonosis associated with host immunomodulation. T helper cells are instrumental to control the disease in the host. Whereas Th1 cells can restrict parasite proliferation, Th2 immune responses are associated with parasite proliferation. Although the early phase of host colonization by E. multilocularis is dominated by a potentially parasitocidal Th1 immune response, the molecular basis of this response is unknown.
Principal Findings
We describe EmTIP, an E. multilocularis homologue of the human T-cell immunomodulatory protein, TIP. By immunohistochemistry we show EmTIP localization to the intercellular space within parasite larvae. Immunoprecipitation and Western blot experiments revealed the presence of EmTIP in the excretory/secretory (E/S) products of parasite primary cell cultures, representing the early developing metacestode, but not in those of mature metacestode vesicles. Using an in vitro T-cell stimulation assay, we found that primary cell E/S products promoted interferon (IFN)-γ release by murine CD4+ T-cells, whereas metacestode E/S products did not. IFN-γ release by T-cells exposed to parasite products was abrogated by an anti-EmTIP antibody. When recombinantly expressed, EmTIP promoted IFN-γ release by CD4+ T-cells in vitro. After incubation with anti-EmTIP antibody, primary cells showed an impaired ability to proliferate and to form metacestode vesicles in vitro.
Conclusions
We provide for the first time a possible explanation for the early Th1 response observed during E. multilocularis infections. Our data indicate that parasite primary cells release a T-cell immunomodulatory protein, EmTIP, capable of promoting IFN-γ release by CD4+ T-cells, which is probably driving or supporting the onset of the early Th1 response during AE. The impairment of primary cell proliferation and the inhibition of metacestode vesicle formation by anti-EmTIP antibodies suggest that this factor fulfills an important role in early E. multilocularis development within the intermediate host.
Recently, we have shown that C6-ceramides efficiently suppress viral replication by trapping the virus in lysosomes. Here, we use antiviral assays to evaluate a synthetic ceramide derivative α-NH2-ω-N3-C6-ceramide (AKS461) and to confirm the biological activity of C6-ceramides inhibiting SARS-CoV-2. Click-labeling with a fluorophore demonstrated that AKS461 accumulates in lysosomes. Previously, it has been shown that suppression of SARS-CoV-2 replication can be cell-type specific. Thus, AKS461 inhibited SARS-CoV-2 replication in Huh-7, Vero, and Calu-3 cells up to 2.5 orders of magnitude. The results were confirmed by CoronaFISH, indicating that AKS461 acts comparable to the unmodified C6-ceramide. Thus, AKS461 serves as a tool to study ceramide-associated cellular and viral pathways, such as SARS-CoV-2 infections, and it helped to identify lysosomes as the central organelle of C6-ceramides to inhibit viral replication.
In vitro and in vivo infection of rhesus monkey microglial cells by simian immunodeficiency virus
(1993)
The observation that microglial cells in brain tissue are probably a major target for human immunodeficiency virus (HIV) infection has raised interest in the pathogenic role of this cell population for the development of neuro-AIOS. Since it is very difficult to obtain microglia from normal or diseased human brain we studied microglial cells isolated from fresh brain tissue of uninfected and simian immunodeficiency virus (SIV) infected rhesus monkeys (Macacca mulatta) in comparison to peripheral blood macrophages. Besides the characterization of the phenotypes of these two cell populations, we examined the replication of SIV in the cells in addition to the effect of viral infection on the expression of cell surface molecules. We found that microglia and macrophages support replication of the wild-type SIV\(_{mac25}\), strain as well as the infectious clone (SIV\(_239\)). Infectious viruswas produced and a CPE developed. Isolated microglial cells from SIV-infected monkeys were latently infected independent of the presence of neuropathological lesions and produced infectious virus after 20-25 days in culture. In situ hybridization revealed that only a small percentage of isolated microglial cells are productively infected in vivo, yet the majority of these expressed MHC class II molecules. This indicated a state of activation that is acquired in vivo. These findings indicate that microglia are a prime target cell for SIV infection in CNS tissue.
Despite the obvious clinical significance of post-stroke angiogenesis in aged subjects, a detailed transcriptomic analysis of post-stroke angiogenesis has not yet been undertaken in an aged experimental model. In this study, by combining stroke transcriptomics with immunohistochemistry in aged rats and post-stroke patients, we sought to identify an age-specific gene expression pattern that may characterize the angiogenic process after stroke. We found that both young and old infarcted rats initiated vigorous angiogenesis. However, the young rats had a higher vascular density by day 14 post-stroke. “New-for-stroke” genes that were linked to the increased vasculature density in young animals included Angpt2, Angptl2, Angptl4, Cib1, Ccr2, Col4a2, Cxcl1, Lef1, Hhex, Lamc1, Nid2, Pcam1, Plod2, Runx3, Scpep1, S100a4, Tgfbi, and Wnt4, which are required for sprouting angiogenesis, reconstruction of the basal lamina (BL), and the resolution phase. The vast majority of genes involved in sprouting angiogenesis (Angpt2, Angptl4, Cib1, Col8a1, Nrp1, Pcam1, Pttg1ip, Rac2, Runx1, Tnp4, Wnt4); reconstruction of a new BL (Col4a2, Lamc1, Plod2); or tube formation and maturation (Angpt1, Gpc3, Igfbp7, Sparc, Tie2, Tnfsf10), had however, a delayed upregulation in the aged rats. The angiogenic response in aged rats was further diminished by the persistent upregulation of “inflammatory” genes (Cxcl12, Mmp8, Mmp12, Mmp14, Mpeg1, Tnfrsf1a, Tnfrsf1b) and vigorous expression of genes required for the buildup of the fibrotic scar (Cthrc1, Il6ra, Il13ar1, Il18, Mmp2, Rassf4, Tgfb1, Tgfbr2, Timp1). Beyond this barrier, angiogenesis in the aged brains was similar to that in young brains. We also found that the aged human brain is capable of mounting a vigorous angiogenic response after stroke, which most likely reflects the remaining brain plasticity of the aged brain.
Dendritic cells (DCs) can be sub-divided into various subsets that play specialized roles in priming of adaptive immune responses. Atherosclerosis is regarded as a chronic inflammatory disease of the vessel wall and DCs can be found in non-inflamed and diseased arteries. We here performed a systematic analyses of DCs subsets during atherogenesis. Our data indicate that distinct DC subsets can be localized in the vessel wall. In C57BL/6 and low density lipoprotein receptor-deficient (Ldlr−/−) mice, CD11c+ MHCII+ DCs could be discriminated into CD103− CD11b+F4/80+, CD11b+F4/80− and CD11b−F4/80− DCs and CD103+ CD11b−F4/80− DCs. Except for CD103− CD11b− F4/80− DCs, these subsets expanded in high fat diet-fed Ldlr−/− mice. Signal-regulatory protein (Sirp)-α was detected on aortic macrophages, CD11b+ DCs, and partially on CD103− CD11b− F4/80− but not on CD103+ DCs. Notably, in FMS-like tyrosine kinase 3-ligand-deficient (Flt3l−/−) mice, a specific loss of CD103+ DCs but also CD103− CD11b+ F4/80− DCs was evidenced. Aortic CD103+ and CD11b+ F4/80− CD103− DCs may thus belong to conventional rather than monocyte-derived DCs, given their dependence on Flt3L-signalling. CD64, postulated to distinguish macrophages from DCs, could not be detected on DC subsets under physiological conditions, but appeared in a fraction of CD103− CD11b+ F4/80− and CD11b+ F4/80+ cells in atherosclerotic Ldlr−/− mice. The emergence of CD64 expression in atherosclerosis may indicate that CD11b+ F4/80− DCs similar to CD11b+ F4/80+ DCs are at least in part derived from immigrated monocytes during atherosclerotic lesion formation. Our data advance our knowledge about the presence of distinct DC subsets and their accumulation characteristics in atherosclerosis, and may help to assist in future studies aiming at specific DC-based therapeutic strategies for the treatment of chronic vascular inflammation.
By promoting ceramide release at the cytosolic membrane leaflet, the neutral sphingomyelinase 2 (NSM) is capable of organizing receptor and signalosome segregation. Its role in T cell receptor (TCR) signaling remained so far unknown. We now show that TCR-driven NSM activation is dispensable for TCR clustering and initial phosphorylation, but of crucial importance for further signal amplification. In particular, at low doses of TCR stimulatory antibodies, NSM is required for Ca\(^{2+}\) mobilization and T cell proliferation. NSM-deficient T cells lack sustained CD3ζ and ZAP-70 phosphorylation and are unable to polarize and stabilize their microtubular system. We identified PKCζ as the key NSM downstream effector in this second wave of TCR signaling supporting dynamics of microtubule-organizing center (MTOC). Ceramide supplementation rescued PKCζ membrane recruitment and MTOC translocation in NSM-deficient cells. These findings identify the NSM as essential in TCR signaling when dynamic cytoskeletal reorganization promotes continued lateral and vertical supply of TCR signaling components: CD3ζ, Zap70, and PKCζ, and functional immune synapses are organized and stabilized via MTOC polarization.
The activity of neutral sphingomyelinase-2 (NSM2) to catalyze the conversion of sphingomyelin (SM) to ceramide and phosphocholine at the cytosolic leaflet of plasma membrane (PM) is important in T cell receptor (TCR) signaling. We recently identified PKCζ as a major NSM2 downstream effector which regulates microtubular polarization. It remained, however, unclear to what extent NSM2 activity affected overall composition of PM lipids and downstream effector lipids in antigen stimulated T cells. Here, we provide a detailed lipidomics analyses on PM fractions isolated from TCR stimulated wild type and NSM2 deficient (ΔNSM) Jurkat T cells. This revealed that in addition to that of sphingolipids, NSM2 depletion also affected concentrations of many other lipids. In particular, NSM2 ablation resulted in increase of lyso-phosphatidylcholine (LPC) and lyso-phosphatidylethanolamine (LPE) which both govern PM biophysical properties. Crucially, TCR dependent upregulation of the important T cell signaling lipid diacylglycerol (DAG), which is fundamental for activation of conventional and novel PKCs, was abolished in ΔNSM cells. Moreover, NSM2 activity was found to play an important role in PM cholesterol transport to the endoplasmic reticulum (ER) and production of cholesteryl esters (CE) there. Most importantly, CE accumulation was essential to sustain human T cell proliferation. Accordingly, inhibition of CE generating enzymes, the cholesterol acetyltransferases ACAT1/SOAT1 and ACAT2/SOAT2, impaired TCR driven expansion of both CD4\(^+\) and CD8\(^+\) T cells. In summary, our study reveals an important role of NSM2 in regulating T cell functions by its multiple effects on PM lipids and cholesterol homeostasis.
Enterovirus D68 (EV-D68) has been recognised as a worldwide emerging pathogen associated with severe respiratory symptoms since 2009. We here report EV-D68 detection in hospitalised patients with acute respiratory infection admitted to three tertiary hospitals in Germany between January 2013 and December 2014. From a total of 14,838 respiratory samples obtained during the study period, 246 (1.7%) tested enterovirus-positive and, among these, 39 (15.9%) were identified as EV-D68. Infection was observed in children and teenagers (0–19 years; n=31), the majority (n=22) being under five years-old, as well as in adults > 50 years of age (n=8). No significant difference in prevalence was observed between the 2013 and 2014 seasons. Phylogenetic analyses based on viral protein 1 (VP1) sequences showed co-circulation of different EV-D68 lineages in Germany. Sequence data encompassing the entire capsid region of the genome were analysed to gain information on amino acid changes possibly relevant for immunogenicity and revealed mutations in two recently described pleconaril binding sites.
Cotton rats (Sigmodon hispidus) replicate measles virus (MV) after intranasal infection in the respiratory tract and lymphoid tissue. We have cloned the cotton rat signaling lymphocytic activation molecule (CD150, SLAM) in order to investigate its role as a potential receptor for MV. Cotton rat CD150 displays 58% and 78% amino acid homology with human and mouse CD150, respectively. By staining with a newly generated cotton rat CD150 specific monoclonal antibody expression of CD150 was confirmed in cotton rat lymphoid cells and in tissues with a pattern of expression similar to mouse and humans. Previously, binding of MV hemagglutinin has been shown to be dependent on amino acids 60, 61 and 63 in the V region of CD150. The human molecule contains isoleucine, histidine and valine at these positions and binds to MV-H whereas the mouse molecule contains valine, arginine and leucine and does not function as a receptor for MV. In the cotton rat molecule, amino acids 61 and 63 are identical with the mouse molecule and amino acid 60 with the human molecule. After transfection with cotton rat CD150 HEK 293 T cells became susceptible to infection with single cycle VSV pseudotype virus expressing wild type MV glycoproteins and with a MV wildtype virus. After infection, cells expressing cotton rat CD150 replicated virus to lower levels than cells expressing the human molecule and formed smaller plaques. These data might explain why the cotton rat is a semipermissive model for measles virus infection.
The bioactive sphingolipids ceramide and sphingosine-1-phosphate (S1P) are involved in the regulation of cell homeostasis and activity ranging from apoptosis to proliferation. We recently described that the two compounds ceranib-2 (inhibiting acid ceramidase) and SKI-II [inhibiting the sphingosine kinases 1 and − 2 (SphK1/2)] reduce mTORC1 activity and measles virus (MV) replication in human primary peripheral blood lymphocytes (PBL) by about one log step. We now further investigated whether mTORC1 downstream signaling and viral protein expression may be affected by ceranib-2 and/or SKI-II. Western blot analyses showed that in uninfected cells the phosphorylation of the eukaryotic initiation factor 4E (eIF4E) was reduced by both inhibitors. Interestingly, MV infection led to an increase of rpS6 protein levels and phosphorylation of eIF4E. Treatment with both inhibitors reduced the rpS6 protein expression, and in addition, SKI-II reduced rpS6 phosphorylation. The phosphorylation of eIF4E was slightly reduced by both inhibitors. In addition, SKI-II led to reduced levels of IKK in MV-infected cells. Both inhibitors reduced the expression of viral proteins and the titers of newly synthesized MV by approximately one log step. As expected, SKI-II and rapamycin reduced also the virally encoded GFP expression; however, ceranib-2 astonishingly led to increased levels of GFP fluorescence. Our findings suggest that the inhibitors ceranib-2 and SKI-II act via differential mechanisms on MV replication. The observed effects on mTORC1 downstream signaling, predominantly the reduction of rpS6 levels by both inhibitors, may affect the translational capacity of the cells and contribute to the antiviral effect in human primary PBL.
Donor CD4\(^+\)Foxp3\(^+\) regulatory T cells (T reg cells) suppress graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (HCT allo-HCT]). Current clinical study protocols rely on the ex vivo expansion of donor T reg cells and their infusion in high numbers. In this study, we present a novel strategy for inhibiting GvHD that is based on the in vivo expansion of recipient T reg cells before allo-HCT, exploiting the crucial role of tumor necrosis factor receptor 2 (TNFR2) in T reg cell biology. Expanding radiation-resistant host T reg cells in recipient mice using a mouse TNFR2-selective agonist before allo-HCT significantly prolonged survival and reduced GvHD severity in a TNFR2-and T reg cell-dependent manner. The beneficial effects of transplanted T cells against leukemia cells and infectious pathogens remained unaffected. A corresponding human TNFR2-specific agonist expanded human T reg cells in vitro. These observations indicate the potential of our strategy to protect allo-HCT patients from acute GvHD by expanding T reg cells via selective TNFR2 activation in vivo.
Breakdown of sphingomyelin as catalyzed by the activity of sphingomyelinases profoundly affects biophysical properties of cellular membranes which is particularly important with regard to compartmentalization of surface receptors and their signaling relay. As it is activated both upon TCR ligation and co-stimulation in a spatiotemporally controlled manner, the neutral sphingomyelinase (NSM) has proven to be important in T cell activation, where it appears to play a particularly important role in cytoskeletal reorganization and cell polarization. Because these are important parameters in directional T cell migration and motility in tissues, we analyzed the role of the NSM in these processes. Pharmacological inhibition of NSM interfered with early lymph node homing of T cells in vivo indicating that the enzyme impacts on endothelial adhesion, transendothelial migration, sensing of chemokine gradients or, at a cellular level, acquisition of a polarized phenotype. NSM inhibition reduced adhesion of T cells to TNF-α/IFN-γ activated, but not resting endothelial cells, most likely via inhibiting high-affinity LFA-1 clustering. NSM activity proved to be highly important in directional T cell motility in response to SDF1-α, indicating that their ability to sense and translate chemokine gradients might be NSM dependent. In fact, pharmacological or genetic NSM ablation interfered with T cell polarization both at an overall morphological level and redistribution of CXCR4 and pERM proteins on endothelial cells or fibronectin, as well as with F-actin polymerization in response to SDF1-α stimulation, indicating that efficient directional perception and signaling relay depend on NSM activity. Altogether, these data support a central role of the NSM in T cell recruitment and migration both under homeostatic and inflamed conditions by regulating polarized redistribution of receptors and their coupling to the cytoskeleton.
The development of two conventional dendritic cells (DC) subsets (cDC1 and cDC2) and the plasmacytoid DC (pDC) in vivo and in cultures of bone marrow (BM) cells is mediated by the growth factor Flt3L. However, little is known about the factors that direct the development of the individual DC subsets. Here, we describe the selective in vitro generation of murine ESAM\(^{low}\) CD103\(^{-}\) XCR1\(^{-}\) CD172a\(^{+}\) CD11b\(^{+}\) cDC2 from BM by treatment with a combination of Flt3L, LIF, and IL‐10 (collectively named as FL10). FL10 promotes common dendritic cell progenitors (CDP) proliferation in the cultures, similar to Flt3L and CDP sorted and cultured in FL10 generate exclusively cDC2. These cDC2 express the transcription factors Irf4, Klf4, and Notch2, and their growth is reduced using BM from Irf4\(^{-/-}\) mice, but the expression of Batf3 and Tcf4 is low. Functionally they respond to TLR3, TLR4, and TLR9 signals by upregulation of the surface maturation markers MHC II, CD80, CD86, and CD40, while they poorly secrete proinflammatory cytokines. Peptide presentation to TCR transgenic OT‐II cells induced proliferation and IFN‐γ production that was similar to GM‐CSF‐generated BM‐DC and higher than Flt3L‐generated DC. Together, our data support that FL10 culture of BM cells selectively promotes CDP‐derived ESAM\(^{low}\) cDC2 (cDC2B) development and survival in vitro.
Multiple myeloma remains a largely incurable disease of clonally expanding malignant plasma cells. The bone marrow microenvironment harbors treatment-resistant myeloma cells, which eventually lead to disease relapse in patients. In the bone marrow, CD4\(^{+}\)FoxP3\(^{+}\) regulatory T cells (Tregs) are highly abundant amongst CD4\(^{+}\) T cells providing an immune protective niche for different long-living cell populations, e.g., hematopoietic stem cells. Here, we addressed the functional role of Tregs in multiple myeloma dissemination to bone marrow compartments and disease progression. To investigate the immune regulation of multiple myeloma, we utilized syngeneic immunocompetent murine multiple myeloma models in two different genetic backgrounds. Analyzing the spatial immune architecture of multiple myeloma revealed that the bone marrow Tregs accumulated in the vicinity of malignant plasma cells and displayed an activated phenotype. In vivo Treg depletion prevented multiple myeloma dissemination in both models. Importantly, short-term in vivo depletion of Tregs in mice with established multiple myeloma evoked a potent CD8 T cell- and NK cell-mediated immune response resulting in complete and stable remission. Conclusively, this preclinical in-vivo study suggests that Tregs are an attractive target for the treatment of multiple myeloma.
The opportunistic fungal pathogen Aspergillus fumigatus can cause severe infections, particularly in immunocompromised individuals. Upon infection, A. fumigatus faces the powerful and directly acting immune defense of the human host. The mechanisms on how A. fumigatus evades innate immune attack and complement are still poorly understood. Here, we identify A. fumigatus enolase, AfEno1, which was also characterized as fungal allergen, as a surface ligand for human plasma complement regulators. AfEno1 binds factor H, factor-H-like protein 1 (FHL-1), C4b binding protein (C4BP), and plasminogen. Factor H attaches to AfEno1 via two regions, via short conserved repeats (SCRs) 6–7 and 19–20, and FHL-1 contacts AfEno1 via SCRs 6–7. Both regulators when bound to AfEno1 retain cofactor activity and assist in C3b inactivation. Similarly, the classical pathway regulator C4BP binds to AfEno1 and bound to AfEno1; C4BP assists in C4b inactivation. Plasminogen which binds to AfEno1 via lysine residues is accessible for the tissue-type plasminogen activator (tPA), and active plasmin cleaves the chromogenic substrate S2251, degrades fibrinogen, and inactivates C3 and C3b. Plasmin attached to swollen A. fumigatus conidia damages human A549 lung epithelial cells, reduces the cellular metabolic activity, and induces cell retraction, which results in exposure of the extracellular matrix. Thus, A. fumigatus AfEno1 is a moonlighting protein and virulence factor which recruits several human regulators. The attached human regulators allow the fungal pathogen to control complement at the level of C3 and to damage endothelial cell layers and tissue components.
Aspf2 From Aspergillus fumigatus Recruits Human Immune Regulators for Immune Evasion and Cell Damage
(2018)
The opportunistic fungal pathogen Aspergillus fumigatus can cause life-threatening infections, particularly in immunocompromised patients. Most pathogenic microbes control host innate immune responses at the earliest time, already before infiltrating host immune cells arrive at the site of infection. Here, we identify Aspf2 as the first A. fumigatus Factor H-binding protein. Aspf2 recruits several human plasma regulators, Factor H, factor-H-like protein 1 (FHL-1), FHR1, and plasminogen. Factor H contacts Aspf2 via two regions located in SCRs6–7 and SCR20. FHL-1 binds via SCRs6–7, and FHR1 via SCRs3–5. Factor H and FHL-1 attached to Aspf2-maintained cofactor activity and assisted in C3b inactivation. A Δaspf2 knockout strain was generated which bound Factor H with 28% and FHL-1 with 42% lower intensity. In agreement with less immune regulator acquisition, when challenged with complement-active normal human serum, Δaspf2 conidia had substantially more C3b (>57%) deposited on their surface. Consequently, Δaspf2 conidia were more efficiently phagocytosed (>20%) and killed (44%) by human neutrophils as wild-type conidia. Furthermore, Aspf2 recruited human plasminogen and, when activated by tissue-type plasminogen activator, newly generated plasmin cleaved the chromogenic substrate S2251 and degraded fibrinogen. Furthermore, plasmin attached to conidia damaged human lung epithelial cells, induced cell retraction, and caused matrix exposure. Thus, Aspf2 is a central immune evasion protein and plasminogen ligand of A. fumigatus. By blocking host innate immune attack and by disrupting human lung epithelial cell layers, Aspf2 assists in early steps of fungal infection and likely allows tissue penetration.
Neutral sphingomyelinase-2 (NSM2) is a member of a superfamily of enzymes responsible for conversion of sphingomyelin into phosphocholine and ceramide at the cytosolic leaflet of the plasma membrane. Upon specific ablation of NSM2, T cells proved to be hyper-responsive to CD3/CD28 co-stimulation, indicating that the enzyme acts to dampen early overshooting activation of these cells. It remained unclear whether hyper-reactivity of NSM2-deficient T cells is supported by a deregulated metabolic activity in these cells. Here, we demonstrate that ablation of NSM2 activity affects metabolism of the quiescent CD4\(^+\) T cells which accumulate ATP in mitochondria and increase basal glycolytic activity. This supports enhanced production of total ATP and metabolic switch early after TCR/CD28 stimulation. Most interestingly, increased metabolic activity in resting NSM2-deficient T cells does not support sustained response upon stimulation. While elevated under steady-state conditions in NSM2-deficient CD4\(^+\) T cells, the mTORC1 pathway regulating mitochondria size, oxidative phosphorylation, and ATP production is impaired after 24 h of stimulation. Taken together, the absence of NSM2 promotes a hyperactive metabolic state in unstimulated CD4\(^+\) T cells yet fails to support sustained T cell responses upon antigenic stimulation.
Background:
HIV-associated neurocognitive disorder (HAND) remains highly prevalent despite effective anti-retroviral therapy (ART). A number of adjunctive pharmacotherapies for HAND have been studied with disappointing results, but preliminary data suggest that lithium may provide clinical benefit. In addition, the low cost of lithium would facilitate access in low- and middle-income countries which carry the greatest burden of HIV.
Methods:
Our objective was to evaluate the 24-week efficacy and safety of lithium in patients with moderate to severe HAND. Our primary efficacy endpoint was the change in Global Deficit Score (GDS) from baseline to 24 weeks, whereas our secondary endpoint was the change in proton magnetic resonance spectroscopy (1H-MRS) brain metabolite concentrations. We conducted a 24-week randomized placebo-controlled trial of lithium as adjunctive pharmacotherapy. We enrolled participants with moderate to severe HAND, on ART for at least 6 months, with suppressed viral loads and attending public sector primary care clinics in Cape Town, South Africa. We randomized 66 participants to lithium (n = 32) or placebo (n = 34). Lithium or placebo was dosed 12-hourly and titrated to achieve the maintenance target plasma concentration of 0.6 to 1.0 mmol/L. Sham lithium concentrations were generated for participants receiving placebo.
Results:
Totally 61 participants completed the study (lithium arm = 30; placebo arm = 31). Participants at enrolment had a mean age of 40 years and a median CD4+ T-cell count of 500 cells/μL. The median change in GDS between baseline and week 24 for the lithium and placebo arms were –0.57 (95% confidence interval [CI] –0.77, –0.32) and –0.56 (–0.69, –0.34) respectively, with a mean difference of –0.054 (95% CI –0.26, 0.15); P = 0.716. The improvement remained similar when analyzed according to age, severity of impairment, CD4+ count, time on ART, and ART regimen. Standard 1H-MRS metabolite concentrations were similar between the treatment arms. The study drug was well tolerated in both study arms. Six serious adverse events occurred, but none were considered related to the study drug.
Conclusion:
Adjunctive lithium pharmacotherapy in patients on ART with HAND was well tolerated but had no additional benefit on neurocognitive impairment.
Transmission of measles virus (MV) from dendritic to airway epithelial cells is considered as crucial to viral spread late in infection. Therefore, pathways and effectors governing this process are promising targets for intervention. To identify these, we established a 3D respiratory tract model where MV transmission by infected dendritic cells (DCs) relied on the presence of nectin-4 on H358 lung epithelial cells. Access to recipient cells is an important prerequisite for transmission, and we therefore analyzed migration of MV-exposed DC cultures within the model. Surprisingly, enhanced motility toward the epithelial layer was observed for MV-infected DCs as compared to their uninfected siblings. This occurred independently of factors released from H358 cells indicating that MV infection triggered cytoskeletal remodeling associated with DC polarization enforced velocity. Accordingly, the latter was also observed for MV-infected DCs in collagen matrices and was particularly sensitive to ROCK inhibition indicating infected DCs preferentially employed the amoeboid migration mode. This was also implicated by loss of podosomes and reduced filopodial activity both of which were retained in MV-exposed uninfected DCs. Evidently, sphingosine kinase (SphK) and sphingosine-1-phosphate (S1P) as produced in response to virus-infection in DCs contributed to enhanced velocity because this was abrogated upon inhibition of sphingosine kinase activity. These findings indicate that MV infection promotes a push-and-squeeze fast amoeboid migration mode via the SphK/S1P system characterized by loss of filopodia and podosome dissolution. Consequently, this enables rapid trafficking of virus toward epithelial cells during viral exit.
Recently, Tummino et al. reported that 34 compounds, including Chloroquine and Fluoxetine, inhibit SARS-CoV-2 replication by inducing phospholipidosis, although Chloroquine failed to suppress viral replication in Calu-3 cells and patients. In contrast, Fluoxetine represses viral replication in human precision-cut lung slices (PCLS) and Calu-3 cells. Thus, it is unlikely that these compounds have similar mechanisms of action. Here, we analysed a subset of these compounds in the viral replication and phospholipidosis assays using the Calu-3 cells and PCLS as the patient-near system. Trimipramine and Chloroquine induced phospholipidosis but failed to inhibit SARS-CoV-2 replication in Calu-3 cells, which contradicts the reported findings and the proposed mechanism. Fluoxetine, only slightly induced phospholipidosis in Calu-3 cells but reduced viral replication by 2.7 orders of magnitude. Tilorone suppressed viral replication by 1.9 orders of magnitude in Calu-3 cells without causing phospholipidosis. Thus, induction of phospholipidosis is not correlated with the inhibition of SARS-CoV-2, and the compounds act via other mechanisms. However, we show that compounds, such as Amiodarone, Tamoxifen and Tilorone, with antiviral activity on Calu-3 cells, also inhibited viral replication in human PCLS. Our results indicate that antiviral assays against SARS-CoV-2 are cell-line specific. Data from Vero E6 can lead to non-transferable results, underlining the importance of an appropriate cell system for analysing antiviral compounds against SARS-CoV-2. We observed a correlation between the active compounds in Calu-3 cells and PCLS.
Herpes simplex virus 1 (HSV-1) infection and stress responses disrupt transcription termination by RNA Polymerase II (Pol II). In HSV-1 infection, but not upon salt or heat stress, this is accompanied by a dramatic increase in chromatin accessibility downstream of genes. Here, we show that the HSV-1 immediate-early protein ICP22 is both necessary and sufficient to induce downstream open chromatin regions (dOCRs) when transcription termination is disrupted by the viral ICP27 protein. This is accompanied by a marked ICP22-dependent loss of histones downstream of affected genes consistent with impaired histone repositioning in the wake of Pol II. Efficient knock-down of the ICP22-interacting histone chaperone FACT is not sufficient to induce dOCRs in ΔICP22 infection but increases dOCR induction in wild-type HSV-1 infection. Interestingly, this is accompanied by a marked increase in chromatin accessibility within gene bodies. We propose a model in which allosteric changes in Pol II composition downstream of genes and ICP22-mediated interference with FACT activity explain the differential impairment of histone repositioning downstream of genes in the wake of Pol II in HSV-1 infection.
Measles virus is a highly contagious virus causing acute and persistent diseases in man, the receptor of which is still not weil characterized. We have isolated a monoclonal antibody (mAb), designated mAb 119, which specifically inhibits measles virus infection of susceptible celllines in a dosa-dependent manner. This antibody precipitates a protein with an apparent molecular mass of 75 kDa from 1251 surface-labeled cells and its epitope is present on human peripheral blood mononuclear cells, human celllines, and the African green monkey cellline Vero. Affinity chromatography of detergent-solubilized cell membrane proteins over a Sepharose column with covalently bound mAb 119 led to the partial purification of the 75-kOa protein. Preincubation of measles virus with this affinity-purified protein inhibited measles virus infection dose dependently. Aminoacid microseq,uencing of this protein revealed its identity with the human membrane-organizing extension spike protein moesin, a protein intra- and extracellularly associated with the plasma membrane of cells. Subsequently, an antibody raised against purified moesin (mAb 38/87) was also found to specifically inhibit measles virus infection of susceptible cells and confirmed our data obtained with mAb 119. Our data suggest that moesin is acting as a receptor for measles virus.
Thymus-derived natural Foxp3\(^{+}\) CD4\(^{+}\) regulatory T cells (nTregs) play a key role in maintaining immune tolerance and preventing autoimmune disease. Several studies indicate that dendritic cells (DCs) are critically involved in the maintenance and proliferation of nTregs. However, the mechanisms how DCs manage to keep the peripheral pool at constant levels remain poorly understood. Here, we describe that the NF-κB/Rel family transcription factor RelB controls the frequencies of steady-state migratory DCs (ssmDCs) in peripheral lymph nodes and their numbers control peripheral nTreg homeostasis. DC-specific RelB depletion was investigated in CD11c-Cre × RelB\(^{fl/fl}\) mice (RelB\(^{DCko}\)), which showed normal frequencies of resident DCs in lymph nodes and spleen while the subsets of CD103\(^{-}\) Langerin\(^{-}\) dermal DCs (dDCs) and Langerhans cells but not CD103\(^{+}\) Langerin\(^{+}\) dDC of the ssmDCs in skin-draining lymph nodes were increased. Enhanced frequencies and proliferation rates were also observed for nTregs and a small population of CD4\(^{+}\) CD44\(^{high}\) CD25\(^{low}\) memory-like T cells (Tml). Interestingly, only the Tml but not DCs showed an increase in IL-2-producing capacity in lymph nodes of RelB\(^{DCko}\) mice. Blocking of IL-2 in vivo reduced the frequency of nTregs but increased the Tml frequencies, followed by a recovery of nTregs. Taken together, by employing RelB\(^{DCko}\) mice with increased frequencies of ssmDCs our data indicate a critical role for specific ssmDC subsets for the peripheral nTreg and IL-2\(^{+}\) Tml frequencies during homeostasis.