A new animal model for the study of genital infections caused by Chlamydia trachomatis has been developed. Female mice were successfully infected after intravaginal inoculation with the C. trachomatis agent of mouse pneumonitis. Evidence for infection was obtained by detection of chlamydial inclusions in smears of cervical scrapings treated with Giemsa stain. Chlamydiae were observed in sections of cervical tissues examined by light and electron microscopy as well as by immunofluorescence microscopy. An antibody response to the agent of mouse pneumonitis was also demonstrated in sera after infection. The mouse model of genital infection with the agent of mouse pneumonitis offers an opportunity to investigate many questions related to pathogenesis and immunity associated with C. trachomatis genital infections.
Female guinea pigs infected in the genital tract with the chlamydial agent of guinea pig inclusion conjunctivitis were selectively immunosuppressed by varying regimens of cyclophosphamide (Cy) treatment. Temporary suppression of both humoral and cell-mediated immunity by daily treatment of Cy (25 mg/kg) for 13 days resulted in a prolonged infection, whereas daily treatment for the duration of the experiment totally prevented the development of humoral and cell-mediated responses and produced an intense and prolonged infection which did not resolve. When humoral immunity alone was suppressed by treatment with Cy (250 and 150 mg/kg) at 9-day intervals, the infection again did not resolve. Treatment with 100 mg of Cy per kg at 9-day intervals resulted in an extended infection which resolved concomitantly with the development of antibody to guinea pig inclusion conjunctivitis. These data indicate that humoral immunity is essential for the recovery of female guinea pigs from guinea pig inclusion conjunctivitis genital infection. A marked weight loss was observed which could not be attributed to Cy treatment alone. Edematous and ulcerative changes of the external genitalia were also noted.
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.
Immunity to reinfection in the genital tract of female guinea pigs with the agent of guinea pig inclusion conjunctivitis was found to be dependent upon an intact humoral immune response. Cell-mediated immunity in the absence of humoral immunity had no apparent role in resistance to challenge infection.
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