Immunity to reinfection of the genital tract of marmosets with Chlamydia trachomatis.

Eleven marmosets inoculated intra-vaginally with either of 2 serotypes (D/E and H) of Chlamydia trachomatis developed a self-limited infection which persisted usually for 10-42 days. Animals re-inoculated on one or more occasions were, however, infected generally for a shorter duration, usually 3-7 days. Curtailed infections were observed after re-inoculation with either the same or a different serotype, indicating that immunity was not serotype specific but cross-protective. IgM and/or IgG chlamydial antibody, measured by micro-immunofluorescence, developed in most of the marmosets on primary infection and was not serotype specific. The antibody titres were boosted on re-infection and there was a correlation between pre-existing high antibody titres and infections of short duration. Chlamydial infection of the genital tract was accompanied by acute inflammation which persisted in about half of the immune animals for up to several weeks despite rapid clearance of the organisms. These features of the experimental infection should help to provide a greater understanding of the immunobiology and pathogenesis of chlamydial genital-tract infections of humans.