Evaluation of Immunoprotective Effects of DNA Vaccine Based on Eimeria maxima EF-1α Antigen and Chicken XCL1 Chemokine.

The moderate pathogenicity coupled with high host susceptibility of Eimeria maxima has precipitated substantial economic losses in the poultry industry. Addressing challenges such as emerging drug resistance underscores the imperative for innovative vaccine strategies. This study developed a novel DNA vaccine to solve this challenge by fusing E. maxima elongation factor-1α (EmEF1α) with chicken chemokine XCL1 (ChXCL1) in the pVAX1 vector. The recombinant plasmid, designated pVAX1-ChXCL1-EmEF1α, was successfully constructed and confirmed to express the ChXCL1-EmEF1α fusion protein in vitro. Immunization of chickens with this DNA vaccine elicited a robust and balanced immune response, characterized by significantly increased proportions of CD4+ (11.76%) and CD8+ (5.58%) T lymphocytes, elevated levels of Th1-associated cytokines (IFN-γ and IL-12), and strong antigen-specific IgG and IgA antibody responses. Following experimental challenge with E. maxima, vaccinated birds exhibited substantial protection: a 66.4% reduction in oocyst shedding, a 71.7% improvement in relative weight gain, marked attenuation of intestinal lesions, and an anticoccidial index (ACI) of 170. These findings demonstrate that the ChXCL1-EmEF1α DNA vaccine effectively enhances both cellular and humoral immunity. Collectively, this study validates ChXCL1 as a potent molecular adjuvant and establishes the "antigen-adjuvant" fusion DNA platform as a promising strategy for developing next-generation vaccines against avian coccidiosis.