ABSTRACTThe immune response toNeisseria gonorrhoeaeis poorly understood, but its extensive antigenic variability and resistance to complement are thought to allow it to evade destruction by the host’s immune defenses. We propose thatN. gonorrhoeaealso avoids inducing protective immune responses in the first place. We previously found thatN. gonorrhoeaeinduces interleukin-17 (IL-17)-dependent innate responses in mice and suppresses Th1/Th2-dependent adaptive responses in murine cellsin vitrothrough the induction of transforming growth factor β (TGF-β). In this study using a murine model of vaginal gonococcal infection, mice treated with anti-TGF-β antibody during primary infection showed accelerated clearance ofN. gonorrhoeae, with incipient development of Th1 and Th2 responses and diminished Th17 responses in genital tract tissue. Upon secondary reinfection, mice that had been treated with anti-TGF-β during primary infection showed anamnestic recall of both Th1 and Th2 responses, with the development of antigonococcal antibodies in sera and secretions, and enhanced resistance to reinfection. In mouse knockout strains defective in Th1 or Th2 responses, accelerated clearance of primary infection due to anti-TGF-β treatment was dependent on Th1 activity but not Th2 activity, whereas resistance to secondary infection resulting from anti-TGF-β treatment during primary infection was due to both Th1- and Th2-dependent memory responses. We propose thatN. gonorrhoeaeproactively elicits Th17-driven innate responses that it can resist and concomitantly suppresses Th1/Th2-driven specific adaptive immunity that would protect the host. Blockade of TGF-β reverses this pattern of host immune responsiveness and facilitates the emergence of protective antigonococcal immunity.IMPORTANCEPathogen-host interactions during infectious disease are conventionally thought of as two-way reactions, that of the host against the pathogen and vice versa, with the outcome dependent on which one ultimately prevails. We propose thatNeisseria gonorrhoeae, a pathogen that has become extremely well adapted to its exclusive human host, proactively directs the manner in which the host responds in ways that are beneficial to its own survival but detrimental to the host. Gonorrhea is a widely prevalent sexually transmitted infection, and naturally occurring gonococcal strains are becoming resistant to most available antibiotics, yet no effective vaccine has been developed. These new insights into the immune response toN. gonorrhoeaeshould lead to novel therapeutic strategies and facilitate new approaches to vaccine development.
Competition for Antigen between Th1 and Th2 Responses Determines the Timing of the Immune Response Switch during Mycobaterium avium Subspecies paratuberulosis Infection in Ruminants