Interferon-γ Responses to Chlamydia trachomatis Vaccine Candidate Proteins in Women With Different Chlamydia Outcomes

Background. Chlamydia trachomatis testing and treatment strategies have not decreased infection rates, justifying need for a chlamydia vaccine. A murine study showed that a vaccine consisting of major outer membrane protein (MOMP) and polymorphic membrane proteins (Pmps) E, F, G, and H elicited protective immunity; studies on human cellular immune responses to Pmps are sparse. Methods. Interferon gamma (IFN-gamma) responses to these 5 proteins were measured by ELISPOT in peripheral blood mononuclear cells from women returning for treatment of a positive chlamydia test. Responses were compared in those with spontaneous chlamydia clearance versus persisting infection at baseline and no reinfection versus reinfection at a 3-month follow-up visit. Results. IFN-gamma response to 1 or more proteins was detected in 39% at baseline and 51.5% at follow-up, most often to PmpE and MOMP. IFN-gamma responses to MOMP were detected less often at follow-up versus baseline in women with reinfection, but were maintained in those without reinfection. Women with spontaneous clearance had a higher magnitude of IFN-gamma response to PmpE and MOMP. Conclusions. IFN-gamma responses to these 5 C. trachomatis vaccine candidate proteins were heterogenous and primarily directed against MOMP and PmpE. Spontaneous chlamydia clearance and absence of reinfection may be clinical correlates of protection.