Identification of immunogenic and antibody-binding membrane proteins of pathogenic Trichomonas vaginalis

Characterization of immunogenic Trichomonas vaginalis membrane proteins was accomplished by using extrinsically and intrinsically labeled organisms and a highly sensitive and specific radioimmunoprecipitation procedure. Intact motile trichomonads were compared with detergent extracts as a source of antigen in radioimmunoprecipitation experiments. Approximately 20 proteins accessible to antibody were identified and ranged in molecular weight from 200,000 to 20,000. Localization on the parasite surface of the highly immunogenic membrane proteins was attempted by using, as the indicator system, formaldehyde-fixed protein A-bearing Staphylococcus aureus pretreated with the various antiserum reagents and incubated with live, motile parasites. Also, indirect immunofluorescence with fluorescein isothiocyanate--anti-rabbit immunoglobulin was also employed after incubation of organisms with either control serum or antiserum from immunized rabbits or after treatment of trichomonads with the immunoglobulin G fraction from each respective serum. No immunoglobulin G antibody appeared to be directed at the anterior trichomonal flagella or the posterior axostyle, whereas strong fluorescence was detected throughout the rest of the T. vaginalis surface. The biological significance of these data is discussed.