Calcium-dependent microneme protein discharge and in vitro egress of Eimeria tenella sporozoites.

Egress is a vital step in the endogenous development of apicomplexan parasites, as it assures the parasites exit from consumed host cells and entry into fresh ones. However, little information has previously been reported on this step of Eimeria spp. In this study, we investigated in vitro egress of Eimeria tenella sporozoites triggered by acetaldehyde. We found that addition of exogenous acetaldehyde induces egress of sporozoites from primary chicken kidney cells (PCKs) and stimulate secretion of E. tenella microneme 2 protein (EtMic 2). Moreover, by using cellular calcium inhibitors, we further proved that these processes were dependent on the intracellular calcium of the parasites. Our findings provide clues to the study of interaction between eimerian parasites and their hosts.