EXPERIMENTALLY-INDUCED INTRAVAGINAL TRITRICHOMONAS-FETUS INFECTION INTHE ESTROGENIZED MOUSE

Studies were initiated to establish and maintain intravaginal Tritrich omonas foetus infections in female BALB/c mice as a model for elucidat ion of parasite and host factors that affect the course of vaginal pro tozoan infections. Results of these studies indicated that T. foetus i nfections could only be established in mice in which estrus was induce d and maintained. Over a period of several weeks, mice induced to estr us by weekly administration of estradiol cypionate exhibited purulent vaginal discharge and perivulvar abscesses. Implantation of silastic t ubing containing 15 mu g of estradiol-17 beta proved effective in indu ction and maintenance of estrus and avoided the animal health problems associated with estradiol cypionate treatment. Results of quantitativ e experiments indicated that the duration of trichomonad infection was influenced by initial colonization of the vagina, i.e., mice with hig h numbers of vaginal trichomonads at 7 days after infection maintained infections longer than did mice with lower numbers of vaginal. parasi tes. Weekly administration of either 2 or 4 mg of methylprednisolone a cetate to estrogenized mice did not extend the duration of T. foetus i nfections, thereby suggesting that the immune response did not limit t he establishment and maintenance of primary vaginal trichomonad infect ions. Study of estrogenized BALB/c nu/nu mice supported these observat ions in that establishment of T. foetus infections was difficult in nu /nu mice and that, in most nu/nu mice (76%), the course of infection w as not lengthened (mean, 1.9 weeks). In contrast, a small number of in fected nu/nu mice (24%) maintained intravaginal trichomonad infections for greater than 20 weeks, which suggested that perhaps the immune re sponse does play a role in elimination of T. foetus infections in mice , Taken together, results of this study suggest that experimental intr avaginal T. foetus infection of estrogenized BALB/c mice provides an a nimal model for examination of parasite-associated and host immune fac tors affecting establishment and maintenance of vaginal trichomonad in fections.