Immunogenic and protective ability of the two developmental forms of Chlamydiae in a mouse model of infertility

To compare the ability of elementary bodies (EB) and reticulate bodies (RB) of the Chlamydia trachomatis mouse pneumonitis (MoPn) biovar to induce a protective immune response, two groups of BALB/c mice were inoculated and boosted twice, with UV-inactivated EB or RB in Freund's adjuvant. Two weeks after the last immunization mice were challenged with C. trachomatis in the ovarian bursa. Vaginal cultures collected for 6 weeks after the intrabursal challenge showed that mice inoculated with EB were significantly protected, while mice inoculated with RB were not. Six weeks after the genital challenge mice were mated. Mice immunized with EB showed significant protection as demonstrated by the number of animals which were fertile and the number of embryos present in the uterine horns. In contrast, no significant protection against infertility was observed in the mice immunized with RB.