Abstract
Background: Eimeria tenella, a highly pathogenic apicomplexan parasite, causes severe avian coccidiosis, threatening global poultry production. Apical membrane antigens (AMAs), conserved proteins in apicomplexan parasites, are critical for host cell invasion, making them promising vaccine targets. In this study, we constructed an the overexpression strain of E. tenella AMA2 (EtAMA2-OE) and evaluated its pathogenicity and immunogenicity. Methods: Transcriptional profiling of EtAMA2 during infection was conducted using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). A homozygous EtAMA2-OE strain was generated using plasmid transfection, drug selection, and flow cytometry. Pathogenicity was assessed through in vitro sporozoite invasion assays and in vivo evaluations, including cecal lesion scoring, oocyst shedding, and weigh-gain monitoring in chicks. Furthermore, immunogenicity was evaluated by challenging immunized chicks with wild-type E. tenella. Results: The EtAMA2-OE strain significantly enhanced invasion efficiency and pathogenicity, causing severe cecal pathology, increased oocyst output, and weight loss. Importantly, immunization with EtAMA2-OE conferred substantial immunity, resulting in significantly reduced oocyst shedding and markedly attenuated cecal lesions in immunized chicks. Conclusions: The present data indicated that EtAMA2 had dual functions as a virulence factor critical for early invasion and a promising vaccine antigen. This study thereby provided new insights for future drug target screening and development of a vaccine against coccidiosis.