Increased sensitivity of gonococcal pilA mutants to bactericidal activity of normal human serum.

PilA is a pleiotropic transcriptional regulator in Neisseria gonorrhoeae, encoded by an essential gene, pilA. It regulates pilin gene expression and stress response and it is implicated in gonococcal adaptation to external signals. All these phenomena may participate in gonococcal virulence. In this report, I tested the role of PilA in another aspect of gonococcal virulence, resistance to the bactericidal effect of normal human serum. Gonococcal mutants with impaired PilA function were more susceptible to the bactericidal effect of normal human serum than the isogenic wild-type strain. However, the major outer membrane protein and the lipooligosaccharide, targets for complement-mediated killing by the serum, were unchanged in the mutants. I discuss the role of PilA in modulating gonococcal sensitivity and resistance to normal human serum.