Gonococcal interactions with human polymorphonuclear leukocytes

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Neisseria gonorrhoeae (Gc) is a human-specific bacterial pathogen that causes the sexually transmitted disease gonorrhea. In infected individuals, massive numbers of polymorphonuclear leukocytes (PMNs) are recruited to the site of infection. However, the resulting exudate contains viable organisms that are transmitted to new hosts, indicating that PMN antimicrobial mechanisms are insufficient to clear gonorrheal infections. In vitro, PMNs can kill a percentage of Gc with which they are presented, but the remainder survive and proliferate. PMNs possess a multisubunit NADPH oxidase that generates reactive oxygen species (ROS) with bactericidal activity. However, NADPH oxidase activity is dispensable for PMN killing of Gc, and I have found that this is because Gc have the surprising ability to suppress ROS generation in PMNs. As a result, PMNs are directing their non-oxidative antimicrobial machinery against Gc. I have identified two Gc gene products, ngol 686 and recN, that protect Gc from killing by PMNs. The goals of this proposal are 1) to identify the non-oxidative PMN antimicrobial factors that can kill Gc and 2) to define the mechanisms underlying the increased sensitivity of the ngo1686 and recN mutants to PMN killing. I will identify PMN antimicrobial factors that have in vitro bactericidal activity against Gc and I will determine whether Gc colocalize with these factors during exposure to PMNs. All these studies will be conducted with Gc in combination with purified PMN bactericidal factors, PMN granule extracts, or intact human PMNs isolated from venous blood. I have been studying the interplay of mucosal pathogens with host cells for 12 years. During my postdoctoral fellowship in Dr. H. Steven Seifert's laboratory at Northwestern University, I began to address how Gc evade PMN clearance, a critical but poorly studied aspect of Gc pathogenesis. In the one-year K99 phase of the Pathway to Independence award, I completed initial studies of Gc-PMN interactions that laid the groundwork for the specific aims outlined in this ROO proposal. I will conduct this independent research in the Department of Microbiology at the University of Virginia Health Sciences Center, where I have been appointed a tenure-track Assistant Professor with a start date of October 1, 2008. The research supported by the ROO award will provide the critical foundation for my laboratory's current and future area of focus, exploring the innate immune response to Neisserial infection.