@phdthesis{Krueger2021,
  author    = {Kr{\"u}ger, S{\"o}ren},
  title     = {Unterschiedliche Einfl{\"u}sse von Komplement auf Reaktionen neutrophiler Granulozyten auf die Infektion mit \(Neisseria\) \(meningitidis\)},
  doi       = {10.25972/OPUS-24969},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-249697},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {The gram-negative diplococcus Neisseria meningitidis (Nme) is a frequent human-specific, commensal bacterium of the upper respiratory tract. Under certain conditions especially in infants, meningococci can translocate into the bloodstream and cause invasive meningococcal disease (IMD) manifesting as meningitis or sepsis or a combination of both. IMD is feared for its rapid progression and high fatality rate if it remains untreated. IMD affects up to one million people annually causing substantial morbidity and mortality worldwide. It is well-established that the complement system is an important protective factor in meningococcal disease through opsonization of bacteria with C3b and the lytic activity of the membrane attack complex although the inflammatory C5a/C5aR1 axis can aggravate IMD. The role of neutrophil granulocytes in meningococcal infection is less clear despite their abundant recruitment throughout the course of disease. This study aimed to characterize neutrophil responses to Nme in vitro and the influence of complement on these responses. In infection assays with whole blood and isolated PMNs, effective binding, internalization and killing of Nme by neutrophils was demonstrated. A significant complement-dependence of neutrophil phagocytosis and oxidative burst was observed. The opsonizing and lytic pathway of the complement cascade were found to be most relevant for these responses since blockade of C3 using inhibitor Compstatin Cp20 reduced phagocytosis and oxidative burst significantly more than the blockade of the inflammatory branch with C5aR1-antagonist PMX53. Opsonization with specific antibodies could not replicate the effect of complement activation indicating that engagement of neutrophil complement receptors, particularly complement receptor 3, is involved. Other neutrophil effector functions such as degranulation and IL-8 release were activated in a complement-independent manner implying activation by other inflammatory signals. Considering existing evidence on the overall protective effect of PMNs, further studies investigating the contribution of each neutrophil effector function to infection survival in vivo are required. Ideally, this should be studied in a murine meningitis or sepsis model in the context of complement activation.},
  subject      = {Neisseria meningitidis},
  language  = {en}
}
@phdthesis{Peters2021,
  author    = {Peters, Simon},
  title     = {The impact of sphingolipids on \(Neisseria\) \(meningitidis\) and their role in meningococcal pathogenicity},
  doi       = {10.25972/OPUS-22623},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226233},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {The obligate human pathogen Neisseria meningitidis is a major cause of sepsis and meningitis worldwide. It affects mainly toddlers and infants and is responsible for thousands of deaths each year. In this study, different aspects of the importance of sphingolipids in meningococcal pathogenicity were investigated. In a first step, the acid sphingomyelinase (ASM), which degrades membrane sphingomyelin to ceramide, was studied in the context of meningococcal infection. A requirement for ASM surface activity is its translocation from the lysosomal compartment to the cell surface, a process that is currently poorly understood. This study used various approaches, including classical invasion and adherence assays, flow cytometry, and classical and super resolution immunofluorescence microscopy (dSTORM). The results showed that the live, highly piliated N. meningitidis strain 8013/12 induced calcium-dependent ASM translocation in human brain microvascular endothelial cells (HBMEC). Furthermore, it promoted the formation of ceramide-rich platforms (CRPs). In addition, ASM translocation and CRP formation were observed after treating the cells with pili-enriched fractions derived from the same strain. The importance for N. meningitidis to utilize this pathway was shown by the inhibition of the calcium-dependent ASM translocation, which greatly decreased the number of invasive bacteria. I also investigated the importance of the glycosphingolipids GM1 and Gb3. The results showed that GM1, but not Gb3, plays an important role in the ability of N. meningitidis to invade HBMEC. By combining dSTORM imaging and microbiological approaches, we demonstrated that GM1 accumulated prolifically around bacteria during the infection, and that this interaction seemed essential for meningococcal invasion. Sphingolipids are not only known for their beneficial effect on pathogens. Sphingoid bases, including sphingosine, are known for their antimicrobial activity. In the last part of this study, a novel correlative light and electron microscopy approach was established in the combination with click chemistry to precisely localize azido-functionalized sphingolipids in N. meningitidis. The result showed a distinct concentration-dependent localization in either the outer membrane (low concentration) or accumulated in the cytosol (high concentration). This pattern was confirmed by mass spectrometry on separated membrane fractions. Our data provide a first insight into the underlying mechanism of antimicrobial sphingolipids.},
  subject      = {Neisseria meningitidis},
  language  = {en}
}
@article{PetersFohmannRudeletal.2021,
  author    = {Peters, Simon and Fohmann, Ingo and Rudel, Thomas and Schubert-Unkmeir, Alexandra},
  title     = {A Comprehensive Review on the Interplay between Neisseria spp. and Host Sphingolipid Metabolites},
  series = {Cells},
  volume    = {10},
  journal   = {Cells},
  number    = {11},
  issn      = {2073-4409},
  doi       = {10.3390/cells10113201},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250203},
  year      = {2021},
  abstract  = {Sphingolipids represent a class of structural related lipids involved in membrane biology and various cellular processes including cell growth, apoptosis, inflammation and migration. Over the past decade, sphingolipids have become the focus of intensive studies regarding their involvement in infectious diseases. Pathogens can manipulate the sphingolipid metabolism resulting in cell membrane reorganization and receptor recruitment to facilitate their entry. They may recruit specific host sphingolipid metabolites to establish a favorable niche for intracellular survival and proliferation. In contrast, some sphingolipid metabolites can also act as a first line defense against bacteria based on their antimicrobial activity. In this review, we will focus on the strategies employed by pathogenic Neisseria spp. to modulate the sphingolipid metabolism and hijack the sphingolipid balance in the host to promote cellular colonization, invasion and intracellular survival. Novel techniques and innovative approaches will be highlighted that allow imaging of sphingolipid derivatives in the host cell as well as in the pathogen.},
  language  = {en}
}