Antigen analysis of several pathogenic strains of Trichomonas vaginalis

Analysis of several human strains of Trichomonas vaginalis and one bovine strain of Tritrichomonas foetus was accomplished with standard sodium dodecyl sulfate-gel electrophoresis and fluorography technology. Highly motile, live trichomonads were radiolabeled, and total trichloroacetic acid-precipitated proteins were electrophoresed. Complex protein profiles of the various human strains of T. vaginalis were obtained with proteins ranging in molecular weight from 20,000 to greater than 200,000. The parasite biosynthesis of the Coomassie brilliant blue-stained protein bands was demonstrated by efficient radiolabeling of trichomonads with [35S]methionine or a 3H-amino acid digest before electrophoresis and fluorography. Immunogenic trichomonal proteins were then identified by a radioimmunoprecipitation method. A detergent extract of [35S] methionine-labeled T. vaginalis proteins was mixed with serum from an immunized rabbit or pooled sera from subcutaneously infected mice and soluble antibody-antigen complexes isolated by adsorption to protein A-bearing Staphylococcus aureus. The radiolabeled protein antigens were then identified by gel electrophoresis and fluorography. Immunized rabbit serum and pooled sera from challenged mice contained high-titered antibody which reacted with numerous high- and low-molecular-weight proteins. Individual subcutaneously infected mice were found to possess identical antibody responses to these immunogenic trichomonal proteins. A high degree of serological cross-reactivity among the various trichomonads was demonstrated. No differences in the composition of immunogenic proteins were observed among cultures grown in vitro for various lengths of time under the experimental conditions employed. Finally, electrophoretic analysis of cloned colonies of T. vaginalis organisms revealed no differences in their protein composition. The biological relevance of these observations is discussed.