Localization of the Phenotypically Varying P270 Protein on dsRNA Virus-positive and Negative Trichomonas vaginalis Isolates |Biomedgrid

Trichomonas vaginalis is a flagellated protist and causal agent for trichomonosis, the number one, nonviral sexually transmitted infection (STI). The parasites of all naturally-occurring isolates of T. vaginalis synthesize the immunogenic protein called P270, which is encoded by a single copy gene with numerous tandemly-repeated elements encoding the sequence DREGRD detected by the monoclonal antibody (MAb) C20A3. Isolates have been defined based on the absence (Type I) or presence (Type II) of T. vaginalis dsRNA virus (TVV). Type II TVV+ isolate organisms grown in batch culture have previously been shown to undergo phenotypic variation between surface and non-surface (cytoplasmic) expression of P270 using the MAb C20A3 in immune-fluorescence (IF) assays. Type I TVV- trichomonads synthesize lower amounts of P270 that is only found in the cytoplasm. In this study both IF and immunoelectron microscopy (IEM) analysis were performed for the first time to localize P270 on and within both types of trichomonal isolates. IF experiments of Type II TVV+ parasites show whole surface labeling of intact, non-permeabilized organisms and surface and cytoplasmic fluorescence for permeabilized trichomonads. Immunocytochemistry of Type II trichomonads treated with MAb C20A3 presented gold-labeling of P270 throughout the external membrane as well as within peripheral vacuoles. Further, there was no P270 detected within the electron dense hydrogenosome organelles. On the other hand, for Type I TVV- permeabilized organisms, P270 is detected by IF only in the cytoplasm of some parasites, and immunocytochemistry confirmed that no trichomonads had surface P270. These data provide evidence for the first time of compartmentalization and surface localization of P270 among phenotypically varying, Type II TVV+ T. vaginalis compared to the Type I TVV- organisms.