Contribution of the outer membrane protein OmpW in Escherichia coli to complement resistance from binding to factor H

Microb Pathog. 2016 Sep:98:57-62. doi: 10.1016/j.micpath.2016.06.024. Epub 2016 Jun 28.

Abstract

The serum complement system is essential for innate immune defense against invading pathogenic bacteria. Some of the 8-stranded β-barrel outer membrane proteins confer bacterial resistance to the innate host immunity. We have previously demonstrated that OmpW, also an 8-stranded β-barrel protein that was identified a decade ago, protects bacteria against host phagocytosis. In this study, we investigated the complement resistance of OmpW. Our results indicate that the upregulation of OmpW is associated with increased survival when bacteria are exposed to normal human sera (NHS). Mutant bacteria lacking OmpW in NHS exhibited significantly lower survival rates in comparison to wild-type and ompW complemented bacteria. Furthermore, the bacterial survival significantly decreased in NHS that was supplemented with EGTA-Mg(2+) compared to that in NHS supplemented with EDTA. These results suggest that OmpW confer resistance to alternative complement pathway-mediated killing. Moreover, the binding of OmpW to factor H, a major inhibitor of alternative pathway, was found, indicating that OmpW recruitment of factor H is a mechanism for bacterial evasion of complement attack.

Keywords: Alternative pathway; Complement; Factor H; Outer membrane protein OmpW; β-barrel.

MeSH terms

  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism*
  • Blood Bactericidal Activity
  • Complement Factor H / metabolism*
  • Complement Inactivating Agents
  • Escherichia coli / genetics
  • Escherichia coli / immunology*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Gene Knockout Techniques
  • Genetic Complementation Test
  • Humans
  • Immune Evasion
  • Immunologic Factors / metabolism*
  • Microbial Viability
  • Protein Binding

Substances

  • Bacterial Outer Membrane Proteins
  • Complement Inactivating Agents
  • Escherichia coli Proteins
  • Immunologic Factors
  • ompW protein, E coli
  • Complement Factor H