The characterization of cysteine protease 4 and superoxide dismutase 6 in Trichomonas vaginalis

Pathogenesis attributable to infection with Trichomonas vaginalis , the causative agent of Trichomoniasis, is largely unknown although cysteine proteases have been implicated. This paper investigated the role of cysteine protease 4 (CP4) in T. vaginalis through characterization and expression of CP4. T. vaginalis strains showed differential protein and mRNA expression, although it was unclear which CP4 variants (other than TVAG_355480 and TVAG_467970) were recognized by the CP4 antibody for the protein studies. Iron did not regulate expression of TVAG_355480 and TVAG_467970 at the transcriptional but possibly at the post-transcriptional level. Our results also suggested that processing of recombinant TVAG_467970 occurred through cleavage by proteins rather than autocatalytic processing. Finally, endogenous CP4 was localized to vesicles though it was unclear which CP4 variant was recognized and was co-localized with HA-tagged VAMP1/2. Localization of HA-tagged TVAG_467970 proved problematic when co-staining with anti-HA and anti-CP4, so further localization studies need to be optimized. This paper also examined the role of iron superoxide dismutase 6 (TvFeSOD6) in resistance to metronidazole, the current drug used for Trichomoniasis infections. Of the two types of resistance, aerobic resistance may occur due to a high concentration of intracellular oxygen which can outcompete metronidazole for electrons or can re-oxidize reduced metronidazole to its inactive form. We determined that there was differential expression of TvFeSODs in T. vaginalis strains with varying levels of resistance although this may not correlate with the degree of resistance. Our results also showed that an increase in ectopic TvFeSOD6 in MSA1121 led to an augmentation in SOD activity and in resistance under aerobic conditions due to the possible role of TvFeSOD6 in also contributing to a higher intracellular oxygen concentration in MSA1121 (which is already sensitive to oxygen), leading to an increase in resistance