Development of high-affinity polyclonal antibodies against chicken CKAP4 and its application in infectious bursal disease.

Infectious bursal disease (IBD), a highly infectious and acute illness triggered by infectious bursal disease virus (IBDV), is notorious for causing immunosuppression in chickens, presenting a huge challenge for global poultry production. Cytoskeleton-associated protein 4 (CKAP4), an endoplasmic reticulum-resident tumorigenesis regulator, remains unexplored in IBDV pathogenesis and lacking anti-chCKAP4 antibodies hindered research. To address the critical lack of species-specific reagents, we generated anti-chCKAP4 polyclonal antibodies with a titer of 1:102400 via prokaryotic expression and animal immunization. Tissue distribution analysis revealed constitutive CKAP4 expression in chickens, while IBDV infection significantly downregulated CKAP4 protein levels in bursal and splenic tissues. This suppression provides a basis for future investigations into the role of CKAP4 in IBDV pathogenesis and positions chCKAP4 as a potential candidate biomarker for IBD. Furthermore, the antibodies demonstrated broad cross-reactivity across commercially vital avian species (ducks, geese, pigeons, quails), enabling comparative pathogenesis studies and advancing development of avian antiviral strategies.