Phenotypic variation and diversity among Trichomonas vaginalis isolates and correlation of phenotype with trichomonal virulence determinants

Abstract

The extent and nature of heterogeneity among representative Trichomonas vaginalis isolates were evaluated by flow cytofluorometry analysis. Monoclonal antibody and monospecific antiserum to an immunodominant trichomonad surface glycoprotein with a molecular weight of 267,000 (267K glycoprotein) were used to evaluate fresh isolates (JHH and RU375) and long-term grown isolates (NYH286, IR78, and JH31A) of T. vaginalis. Isolates NYH286, JH31A, and JHH were made up of heterogeneous staining (positive [pos] phenotype) and nonstaining (negative [neg] phenotype) populations of trichomonads, whereas RU375 and IR78 285 Vol. 53,No. 2

Trichomonas vaginalis phenotypic variation occurs only among trichomonads infected with the double-stranded RNA virus.

“…Isolates that were stable negative phenotype populations did not undergo phenotypic variation (3,4). However, purified subpopulations of positive and negative phenotype trichomonads newly fractionated from the heterogeneous parents were both capable of phenotypic variation upon further in vitro cultivation (3,4).…”

“…More recent studies examining the phenotypes of fresh isolates of T. vaginalis (3, 4) confirmed the presence of only two types of parasite populations. On the basis of mAb reactivity via indirect immunofluorescence, isolates comprised homogeneous, negative phenotype trichomonads or heterogeneous populations containing both positive and negative phenotype trichomonads (3,4). Isolates that were stable negative phenotype populations did not undergo phenotypic variation (3,4).…”

“…On the basis of mAb reactivity via indirect immunofluorescence, isolates comprised homogeneous, negative phenotype trichomonads or heterogeneous populations containing both positive and negative phenotype trichomonads (3,4). Isolates that were stable negative phenotype populations did not undergo phenotypic variation (3,4). However, purified subpopulations of positive and negative phenotype trichomonads newly fractionated from the heterogeneous parents were both capable of phenotypic variation upon further in vitro cultivation (3,4).Another recent and as yet poorly understood observation that may be relevant to the biology of this host-parasite relationship is the presence of a virus-encoded double-stranded ribonucleic acid (dsRNA)' among some but not all isolates of T. vaginalis (5-7) .…”

“…Trichomonas vaginalis is a major sexually transmitted parasite that inhabits primarily the vaginal tract of women. Very little is known about precise virulence factors of the pathogenic human trichomonads, although recent reports (1)(2)(3) indicate that the ability of these parasites to undergo phenotypic variation may be related to expression of certain virulence attributes . For example, parasites that lacked a repertoire of major immunogens on their surface (negative phenotype) displayed enhanced cytadherence and killing of host cells (3).…”

“…Very little is known about precise virulence factors of the pathogenic human trichomonads, although recent reports (1)(2)(3) indicate that the ability of these parasites to undergo phenotypic variation may be related to expression of certain virulence attributes . For example, parasites that lacked a repertoire of major immunogens on their surface (negative phenotype) displayed enhanced cytadherence and killing of host cells (3). On the other hand, trichomonads possessing surface immunogens (positive phenotype) had a diminished ability to cause contact-dependent cytotoxicity of HeLa cells; however, the positive phenotype organisms were still capable of shifting to the negative phenotype (3).…”