Biologjia Online

A secreted cysteine protease (CP) fraction from Trichomonas vaginalis is shown here to induce apoptosis in human vaginal epithelial cells (HVEC) and is analyzed by mass spectrometry. The trichomonad parasite T. vaginalis causes one of the most common non-viral sexually transmitted infection in humans, trichomoniasis. The parasite as well as a secreted cysteine protease (CP) fraction, isolated by affinity chromatography followed by Bio-Gel P-60 column chromatography, are shown to induce HVEC apoptosis, as demonstrated by the Cell Death Detection ELISAPLUS assay and Annexin V-FITC flow cytometry analyses. Initiation of apoptosis is correlated with protease activity since the specific CP inhibitor E-64 inhibits both activities. SDS-PAGE analysis of the CP fraction reveals triplet bands around 30 kDa, and MALDI-TOF MS indicates two closely associated peaks of MW 23.6 kDa and 23.8 kDa. Mass spectral peptide sequencing of the proteolytically digested CPs results in matches to previously reported cDNA clones, CP2, CP3, and CP4 [Mallinson et al. Microbiology 140 (1994) 2725-2735.], as well as another sequence with high homology to CP4 (www.tigr.org). These last two species are the most abundant components of the CP fraction. The present results, suggesting that CP induced programmed cell death may be involved in the pathogenesis of T. vaginalis infection in vivo, may have important implications for therapeutic intervention.