Gardnerella promotion of N. gonorrhoeae pathogenesis

PROJECT SUMMARY Neisseria gonorrhoeae is the causative agent of the sexually-transmitted infection gonorrhea and causes serious complications in women, including pelvic inflammatory disease, ectopic pregnancy, and tubal-factor infertility. Gonorrhea is more frequent in women who have bacterial vaginosis (BV). BV is the most common gynecological disorder in women of childbearing age and is associated with adverse pregnancy outcomes and enhanced transmission of sexually-transmitted diseases. We hypothesize that Gardnerella promotes N. gonorrhoeae pathogenesis in ways that affect bacterial survival via immune evasion and ability to infect new hosts via lipooligosaccharide (LOS) sialylation. Two Gardnerella virulence factors appear capable of shifting the balance between two mechanisms that impact LOS-dependent infectivity traits of gonococci. First, the cytolytic toxin vaginolysin releases epithelial cell contents in a CD59-dependent manner that promotes LOS sialyation necessary for gonococcal immune evasion through the recruitment of factor H, a negative regulator of complement killing. Second, a sialidase produced by some Gardnerella species can remove sialic acid from gonococcal LOS, a step needed to promote transmission via binding to asialyloglycoprotein receptors on endometrial cells and male urethral cells. These factors may act at different points in disease progression, since vaginolysin is predicted to be produced by certain phase variants early in infection, and sialidase is made by different phase variants at a later stage. Although Gardnerella spp. have not previously been genetically tractable, we developed methods for making targeted, selectable mutations as well as complements in the Gardnerella chromosome. We will use mutants of Gardnerella, N. gonorrhoeae, and human cell lines derived from the cervix, uterus, and the male urethra to determine the mechanisms by which Gardnerella vaginolysin and sialidase promote immune evasion and dissemination of N. gonorrhoeae.