Trichomonas vaginalis NYH286 phenotypic variation may be coordinated for a repertoire of trichomonad surface immunogens

Trichomonas vaginalis isolate NYH286 was fractionated with immunoglobulin G of sera from patients with trichomoniasis. Subpopulations of trichomonads with phenotypes of either patient serum-immunoglobulin G reactive (PS⁺) or nonreactive (PS^-) were obtained. Flow cytofluorometry of PS⁺ and PS^- subpopulations with a monoclonal antibody called C20A3 which reacts with a high-molecular-weight immunogen of T. vaginalis gave corresponding fluorescent (positive) and nonfluorescent (negative) phenotypes. No relationship was seen between PS⁺ and PS^- phenotypes and binding of soybean agglutinin, wheat germ agglutinin, and concanavalin A, showing that PS^- organisms still possessed carbohydrate moieties on the surfaces based on lectin binding. Phenotypic variation among the PS⁺ and PS^- trichomonads was observed during in vitro growth. A positive-to-negative phenotype shift was also recorded for parasites obtained from lesions of mice subcutaneously infected with PS⁺ trichomonads. The involvement of surface proteins in the differential PS⁺ and PS^- reactions was supported by soluble antigen and whole cell radioimmunoprecipitation assays. Finally, enhanced parasitism and killing of HeLa cells in monolayer cultures were observed for PS^- subpopulations as compared with PS⁺ counterparts. The data support the idea that phenotypic variation for T. vaginalis may be coordinated for a repertoire of trichomonad immunogens and that such membrane dynamics influence expression of virulence determinants for these sexually transmitted disease agents.