Evaluation of the C protein of BVDV as a vaccine candidate: Immunoprotective studies in mice.

Bovine Viral Diarrhea Virus (BVDV) is a major pathogen associated with calf diarrhea and reproductive disorders in cattle. This study evaluated the immune-protective potential of a subunit vaccine based on the capsid C protein of the BVDV HNL-1 strain. In mice model, the C protein subunit vaccine exhibits a favorable safety and elicits robust immune-protective efficacy comparable to commercial inactivated vaccines. Immunized mice exhibited a significant increase in serum anti-C protein IgG antibodies (P < 0.01) and a neutralizing antibody response. The vaccine effectively stimulated both Th1 and Th2 immune responses, as indicated by elevated levels of IFN-γ and IL-4 (P < 0.01). Following viral challenge, substantial reductions in viral loads were observed across multiple tissues (liver, kidney, spleen, lungs, duodenum), as·well as in blood, and feces (P < 0.01). Histopathological analysis revealed markedly attenuated organ damage, reduced apoptosis of intestinal epithelial cells (P < 0.05), and significant increases in goblet cell numbers and expression of tight junction proteins (ZO-1/Occludin) (P < 0.01), indicating effective preservation of the intestinal mucosal barrier. Together, these findings collectively demonstrate that the C protein subunit vaccine confers protection through dual mechanisms: activation of both humoral and cellular immune response, and maintenance of intestinal barrier integrity. This vaccine candidate represents a promising strategy for controlling BVDV and provides a foundation for the development of novel vaccines.