TRICHOMONAS-VAGINALIS HEMOLYSIS - PH REGULATES A CONTACT-INDEPENDENT MECHANISM-BASED ON PORE-FORMING PROTEINS

There is a controversy in literature about involvement of secreted fac tors in the pathogenetic mechanisms of Trichomonas vaginalis, describe d mostly as contact-dependent. We found that the protozoan, under trig gering conditions, is able to release molecules that lead to lysis wit hout direct contact between parasite and target cell as a prerequisite . In this paper we characterize contact-independent cytotoxicity using the red blood cell as a cellular model. Contact-independent haemolysi s is a phenomenon where pH exerts a key role, triggering the secretion of a lytic molecule and regulating its activity. A partial physicoche mical characterization of the haemolytic factor suggests that a protei n of M(r)>30 kDa could be the effector responsible for damage. Further more, the parasite-induced membrane permeabilization, detected by meas uring potassium escape from the target cell, and an effective osmotic protection by carbohydrates allowed us to relate the previously descri bed pore-forming mechanism involved in contact-dependent cytotoxicity with the contact-independent lysis. (C) 1996 Academic Press Limited