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Opc- and pilus-dependent interactions of meningococci with human endothelial cells: molecular mechanisms and
M Virji1, K Makepeace, I R Peak
1Department of Paediatrics, University of Oxford, John Radcliffe Hospital, UK. mumtaz.virji@paediatrics.oxford.ac.uk
Abstract:
The interplay between four surface-expressed virulence factors of Neisseria meningitidis (pili, Opc, capsule and lipopolysaccharide (LPS)) in host cell adhesion and invasion was examined using derivatives of a serogroup B strain, MC58, created by mutation (capsule, Opc) and selection of variants. To examine the role of Opc and of additional expression of pili, bacteria lacking the expression of Opa proteins were used. The effects of different LPS structures were examined in variants expressing either sialylated (L3 immunotype) or truncated non-sialylated (L8 immunotype) LPS. Studies showed that (i) pili were essential for meningococcal interactions with host cells in both capsulate and acapsulate bacteria with the sialylated L3 LPS immunotype, (ii) the Opc-mediated invasion of host cells by piliated and non-piliated bacteria was observed only in acapsulate organisms with L8 LPS immunotype, and (iii) expression of pili in Opc-expressing bacteria resulted in increased invasion. Investigations on the mechanisms of cellular invasion indicated that the Opc-mediated invasion was dependent on the presence of serum in the incubation medium and was mediated by serum proteins with arginine-glycine-aspartic acid (RGD) sequence. Cellular invasion in piliated Opc+ phenotype also required bridging molecules containing the RGD recognition sequence and appeared to involve the integrin alpha v beta 3 as a target receptor on endothelial cells. These studies extend the previous observations on variants of a serogroup A strain (C751) and show that Opc mediates cellular invasion in distinct meningococcal strains and provide confirmation of its mechanism of action. This is the first investigation that evaluates, using derivatives of a single strain, the interplay between four meningococcal surface virulence factors in host cell invasion.
Insights
Pili are crucial for Neisseria meningitidis interaction with host cells. The Opc protein mediates invasion, especially in bacteria lacking capsule and with specific lipopolysaccharide (LPS) structures, often involving RGD-containing proteins.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Neisseria meningitidis possesses multiple surface virulence factors, including pili, Opc, capsule, and lipopolysaccharide (LPS).
- Understanding the interplay of these factors is crucial for deciphering meningococcal pathogenesis and host cell interactions.
Purpose of the Study:
- To investigate the combined roles of pili, Opc, capsule, and LPS in Neisseria meningitidis host cell adhesion and invasion.
- To elucidate the mechanisms underlying Opc-mediated and pili-mediated cellular invasion.
Main Methods:
- Utilized isogenic derivatives of a serogroup B strain (MC58) with specific mutations and selected variants.
- Manipulated expression of capsule, Opc, and Opa proteins; varied LPS structures (L3 and L8 immunotypes).
- Investigated bacterial interaction with host cells, focusing on adhesion and invasion mechanisms, including serum protein involvement and specific receptors.
Main Results:
- Pili were essential for host cell interaction across different conditions with L3 LPS.
- Opc-mediated invasion occurred in acapsulate bacteria with L8 LPS, independent of pili.
- Co-expression of pili and Opc enhanced invasion, dependent on serum factors with RGD sequences and potentially integrin alpha v beta 3.
Conclusions:
- Pili and Opc play distinct but sometimes cooperative roles in Neisseria meningitidis invasion.
- LPS structure and capsule presence significantly influence the contribution of pili and Opc to invasion.
- Opc-mediated invasion involves serum proteins and specific host cell receptors, providing insights into meningococcal pathogenesis.