Molecular Study Of Tghly-?-induced Egress Of Toxoplasma Gondii From Infected Host Cells

Background: Toxoplasma gondii is an obligate intracellular protozoan parasite which could infect all nucleated cells.It is estimated that one-third population around the world was chronically infected with toxoplasma,and in china this infection rate is about 5% to 20.Thus,toxoplasmosis is an important zoonosis.Treatment and prevention of toxoplasmosis is emerging challenge facing clinical physicians and policy makers.To complete its cellular lysis life cycle in host cells,T.gondii should invade cells,replicate inside cells and egress from infected cells.Egression from infected cells distroyes the integrity of host cell,leading to the devastating lesion of host organs and tissues.From Toxo DB,we find a homologue gene of bacterial hymolysin.We termed it as Tg Hly-? and made a hypothesis that Tg Hly-? could induce egress of T.gondii from infected cells.Objective: to investigate whether Tg Hly-? has positive effect on egress of T.gondii and to unveil the mechanism of Tg Hly-? induced egress.Methods: online softwares were used to analyse the structure of Tg Hly-? protein which was then expressed by using E.coli;exogenous Tg Hly-? protein was used to induce egress of T.gondii and egressed tachyzoites were counted using FACS;the changes of host cell apoptosis related proteins were evaluated by using western blotting.Results: Tg Hly-? is a transmembrane protein and was evolutionarily conserved with hymolysins from plasmodium and bacteria.We expressed this protein successfully and used it to trigger egress of T.gondii.Exogenous Tg Hly-? could induce egress of T.gondii in a parasitic intracellular development-dependent manner.And Tg Hly-?-induced egress depended on availability of intraparasitic calcium and parasitic mobility.Phosphorilation levels of host apoptosis proteins were significant increased in Tg Hly?-induced egress.Egressed parasites had no loss in virulence and growth rate.Conclusions: Exogenous Tg Hly-? could induce egress of T.gondii in a parasitic intracellular development-dependent manner.And Tg Hly-?-induced egress depended on availability of intraparasitic calcium and parasitic mobility.