EtSERPIN1 binding with chicken ANXA2 is essential for Eimeria tenella attachment and invasion process.

Serpin protease inhibitors (SERPIN) in protozoa play crucial roles in various biological processes, including the invasion of host cells. However, the precise roles and molecular mechanisms underlying SERPIN-mediated invasion of parasite remain poorly understand. In this study, we provide evidence that surface-expressed Eimeria tenella SERPIN1 (EtSERPIN1) on sporozoites is involved in adhesion and invasion processes. To elucidate the molecular target responsible for mediating EtSERPIN1-induced invasion, we utilized GST pull-down and yeast two-hybrid assays to identify host cell membrane proteins interacting with EtSERPIN1. Our findings revealed an interaction between EtSERPIN1 and a membrane protein called annexin A2 (ANXA2). Furthermore, recombinant GgANXA2 was shown to bind to the sporozoite surface. Pre-treatment with anti-GgANXA2-specific antibody or recombinant GgANXA2 protein significantly inhibited EtSERPIN1 binding to host cells. Pre-incubation with recombinant GgANXA2 also reduced sporozoite infection in both DF-1 cells and chickens. These results suggest that the interaction between EtSERPIN1 and GgANXA2 plays a critical role in both adhesion and invasion processes of E. tenella sporozoites. Finally, we investigated the impact of recombinant GgANXA2 and EtSERPIN1 proteins on E. tenella infection. Our results demonstrate that incubation with GgANXA2 protein significantly attenuated sporozoite infectivity, as evidenced by a significant reduction in parasite burden within the chicken cecum. Immunization with recombinant EtSERPIN1 exhibited potent anti-E. tenella activity, with higher body weight gains, lower cecal lesions and oocyst output, as well as elevated levels of cecal mucosa antibodies. These findings suggest that targeting GgANXA2 through EtSERPIN1 mediates adhesion and invasion processes of E. tenella, highlighting its potential as a novel therapeutic target.