The purpose of this investigation was to determine the relative roles of the humoral and cell-mediated immune responses in the resolution of chlamydial genital infection of mice and resistance to reinfection. To this end, female BALB/c mice were rendered B cell deficient by treatment with heterologous anti-immunoglobulin M (IgM) serum from birth. Controls were similarly treated with either normal serum or phosphate-buffered saline. Before inclusion in each experiment, aiti-IgM-treated mice were screened for the absence of IgM in serum and for the presence of cell-mediated immune responses. In addition, ppleen cells from anti-IgM-treated mice responded to concanavalin A and phytohemagglutinin but not to lipopolysaccharide. By these criteria, mice were designated B cell deficient. B-cell-deficient mice and controls were inoculated intravaginally with a suspension of mouse pnecvumonitis agent (MoPn), a Chiamydia trachomatis biovar. All B-cell-deficient mice resolved the infection. Additionally, no significant difference was seen in the course of the infection in B-cell-deficient mice when compared with controls. In contrast to control mice, B-cell-deficient mice displayed no detectable antibody responses to MoPn in serum or in genital secretions. However, both B-cell-deficient mice and controls developed delayed-type hypersensitivity and T-cell proliferative responses to MoPn. When challenged 53 days after primary infection, no significant difference was seen in the resistance of B-cell-deficient mice to reinfection when compared with that of the controls. These data indicate that cell-mediated immune mechanisms play an important role in the resolution of and resistance to chlamydial genital infection in this model.

Congenitally athymic nude mice and their heterozygous counterparts were inoculated intravaginally with the chlamydial agent of mouse pneumonitis, a Chlamydia trachomatis biovar. Heterozygous mice resolved their infections in 20 days, whereas nude mice developed chronic infections which lasted at least 265 days and did not resolve within the time course of the experiments. Heterozygous mice produced high levels of antibody in both serum and secretions in contrast to nude mice, which produced very low levels of antibody in serum alone.

~ ~Because partial protection against reinfection is induced by experimental infection in the guinea-pig model of genital chlamydial infection, we sought to induce immunity by immunization. Female guinea-pigs were immunized subcutaneously with the major outer-membrane protein (MOMP) and the 61 kDa cysteine-rich outer-membrane protein (61 kDa) of the agent of guinea-pig inclusion conjunctivitis (GPIC) eluted from SDS-polyacrylamide gels (SDS-MOMP, SDS-61 kDa). Post-immunization sera and secretions contained antibodies to the SDS-purified proteins at high titre as measured by immunoblotting, whereas enzyme immunoassays (EIA) using whole elementary bodies as antigen showed significantly lower titres (P < 0.001). Likewise, blastogenic responses of peripheral mononuclear cells to GPIC elementary bodies were weak. Animals immunized with SDS-MOMP and SDS-61 kDa were fully susceptible to intravaginal challenge, as were control animals immunized with buffer without protein. Another group of animals were immunized with material prepared by extraction of chlamydial outer-membrane complexes with octyl /?-D-glucopyranoside (OGP) and dithiothreitol, which consisted largely of M O M P (OGP-MOMP). In contrast to the SDS-MOMP group, sera and secretions in the OGP-MOMP group showed high titres in EIA, and high titre antibodies to M O M P by immunoblot; however, most animals also had antibodies to 61 kDa, 72 kDa and ca. 84 kDa outer-membrane proteins. OGP-MOMP animals were partially protected against genital challenge as evidenced by low inclusion scores compared to control animals, although duration of infection measured by culture isolation was similar to controls. Immunoblot analysis of sera from immunized animals and from a group of immune animals post-infection was performed using recombinant fusion peptides containing the four variable domains of MOMP. No consistent differences in reaction patterns were observed when sera from protected and non-protected animals were compared. Thus, a highly refined outermembrane preparation is capable of producing partial immunity to genital infection. Further study is required to determine whether the protection is due to M O M P itself or to other outer-membrane proteins found in small amounts in the OGP-MOMP immunogen. The results suggest the possibility that discontinuous M O M P epitopes could play a role in inducing a protective immune response in the guinea-pig model, a concept that requires further evaluation.

Female guinea pigs which had been infected genitafly with the agent of guinea pig inclusion conjunctivitis were chaflenged at various times after infection with fresh inocula to determine the duration of immunity resulting from the primary infection. At 30 days after infection, most guinea pigs were resistant to reinfection, as indicated by the inability to isolate chlamydiae from cervical swabs. However, at 77, 155, and 294 days, all animals became reinfected, although the course of the infection was abbreviated and of lower intensity. When various immune parameters were examined, a decrease in antibodies in both serum (immunoglobulin G ([IgG]) and genital secretions (IgA, IgG) was observed after 30 days. A decrease in antibodies to the major outer membrane protein and an 84K component was noted in serum. In genital secretions, IgA antibodies to all major chlamydial components declined markedly after 30 days. Cell-mediated immunity as measured by proliferation of peripheral blood lymphocytes to guinea pig inclusion conjunctivitis antigen also was at a peak response 30 days after infection and decreased thereafter. Thus, loss of complete immunity could not be associated with a particular immune parameter. When genital secretions were examined 14 days after the challenge infection, IgA antibody levels to the lipopolysaccharide and 61K protein components had increased in intensity, whereas other antibodies were relatively low. In addition, complete immunity to a third infection was not increased in duration when animals had recovered from two previous genital infections.

No abstract