Trichomonas vaginalis: Identification of soluble and membrane-associated phospholipase A<inf>1</inf> and A<inf>2</inf> activities with direct and indirect hemolytic effects

A direct hemolytic activity, dependent on phospholipase A (PLA) activity, was located in the particulate subcellular fraction (P30) of Trichomonas vaginalis. We identified soluble direct and indirect hemolytic activities in the spent medium and soluble fraction (S30) of T. vaginalis strain GT-13. Spent medium showed the highest specific indirect hemolytic activity (SIHA) at pH 6.0 (91 indirect hemolytic units [HU]/mg/hr). Spent medium and P30, but not S30, showed direct hemolytic activity. PLA activity was protein dose dependent and time dependent. The highest PLA activity was observed at pH 6.0. All trichomonad preparations showed phospholipase A ₁ (PLA A ₁) and phospholipase A ₂ (PLA A ₂) activities. Indirect and direct hemolytic activity and PLA A ₁ and PLA A ₂ diminished at pH 6.0 and 8.0 with increasing concentrations of Rosenthal's inhibitor. The greatest effect was observed with 80 μM at pH 6.0 on the SIHA of S30 (83% reduction) and the lowest at pH 8.0, also on the SIHA of S30 (26% reduction). In conclusion, T. vaginalis contains particulate and soluble acidic, and alkaline direct and indirect hemolytic activities, which are partially dependent on alkaline or acidic PLA A ₁ and PLA A ₂ enzymes. These could be responsible for the contact-dependent and -independent hemolytic and cytolytic activities of T. vaginalis.