Objective: To evaluate the roles of Toll-like receptor 2 (TLR2) and TLR4 in immune responses to Chlamydia trachomatis (Ct) genital tract infection in mice.
Methods: The wild type (WT, n=11), TLR2(-/-) (n=14) and TLR4(-/-) (n=11) mice were inoculated intravaginally with 1×10(4) inclusion forming units (IFUs) of live C.muridarum (strain MoPn/Nigg) to establish the models of Ct genital tract infection. The vaginal swabs were taken at the 3rd, 7th, 10th, 17th, 24th, 31st, 38th, 45th day after the infection. Immunofluorescence assay was used to quantify live organisms from each swab. The inflammatory cytokines interleukin-1α (IL-1α), IL-6 and macrophage inflammatory protein 2 (MIP-2) were measured using ELISA. The 70th day post infection, the titers of mouse serum Ct-specific antibody isotypes were determined using an immunofluorescence technique; after the macrophages harvested from peritoneal cavity were infected with MoPn strain for 24 hours, the culture supernatants were examined for the contents of cytokines IL-1α, IL-6 and MIP-2 using ELISA. The harvested splenocytes were stimulated with UV-inactivated chlamydial antigens for 72 hours, and the culture supernatants were measured for the levels of cytokines interferon γ (IFN-γ), IL-17, IL-4 and IL-5 using ELISA.
Results: No significant difference was observed in the number of IFUs from the vaginal swabs at any time points post infection among WT, TLR2(-/-) and TLR4(-/-) mice. All mice displayed similar time course of live organism shedding. Until the 38th day, all mice cleared live organism. Macrophages lacking TLR2 produced significantly decreased amounts of IL-1α, IL-6 and MIP-2 compared with those in WT mice; however, there was no significant difference between WT and TLR4(-/-) mice. The vaginal swab samples from TLR2(-/-) mice also had lower levels of inflammatory cytokines. Splenocytes from the three groups of mice all produced high levels of both IFN-γ and IL-17, and low levels of both IL-4 and IL-5, and no significant difference was found among the three groups. The ratio of serum IgG2a/IgG1 in the three groups of mice was greater than 1, and no significant difference was found among the three groups.
Conclusion: TLR2, rather than TLR4 mediates early immune response following Ct genital tract infection in mice. However, neither TLR4 nor TLR2 is required for adaptive immune responses induced by Ct genital tract infection.