Differences in Infectivity and Induction of Infertility: a Comparative Study of Chlamydia Trachomatis Strains in the Murine Model

Chlamydia trachomatis, although commonly asymptomatic in women, can result in chronic sequelae, such as pelvic inflammatory disease, ectopic pregnancy and infertility. However, a clear relationship has not been determined between specific serovars and the ability to lead to upper genital tract infection or infertility. Thus, in order to investigate differences in pathogenicity, C3H/HeN mice were infected in the ovarian bursa with the C. trachomatis strains D (UW-3/Cx), F (N.I.1), F (IC-Cal-3) and E (Bour). Differences both in the amount of vaginal shedding as well as subsequent fertility rates were observed between D (UW-3/Cx) and F (N.I.1) compared to F (IC-Cal-3) and E (Bour). Approximately 50% of the mice infected with the D (UW-3/Cx) and F (N.I.1) strains had vaginal shedding for up to 3-4 weeks after infection and fertility rates of less than 25%. Furthermore, mice inoculated with D (UW-3/Cx) and F (N.I.1) showed infertility even in the absence of medroxy progesterone acetate (MPA) treatment. In contrast, both MPA and non-MPA treated mice infected with F (IC-Cal-3) or E (Bour) did not show vaginal shedding and had fertility rates between 45 and 88%. Mutations in the CT135 open reading frame have been associated with virulence. However, no nucleotide differences were found among the four isolates for CT135. This murine model of infection with C. trachomatis may help with the understanding of disease pathology in humans and ultimately vaccine development.