Identification of heme- and hemoglobin-binding proteins in Trichomonas vaginalis

Abstract

Trichomonas vaginalis is the cause of human trichomoniasis. Although acquisition of iron by binding to host hemoglobin through distinct receptor(s) has been described in this parasite, no specific hemoglobin-binding site has been reported. Our hypotheses were: (1) hemolytic activity of T. vaginalis isolates correlates with the virulence, and (2) T. vaginalis binds hemoglobin through a specific surface receptor. The in vitro hemolytic activities of four T. vaginalis strains were examined. No correlation between hemolytic activity and virulence in different isolates was found. Using hemoglobin-affinity chromatography, two protein bands of approximately 48 and 63 kDa were detected, the former binds preferentially to heme. Mass spectral analysis indicated that the 48- and 63-kDa proteins had significant homology with the subunits of two T. vaginalis adhesins: AP51 and AP65, respectively. This study confirms the existence of multifunctional proteins in T. vaginalis, which enable the parasite to survive in a constantly changing environment like human vagina.