Immunogenicity of Virus-like Particles Based on VP1 Protein of Bovine Norovirus

Bovine Norovirus (BNoV) is a member of the enterovirus family that can cause gastroenteritis in calves. This virus poses a significant risk to calf growth and development as well as to the long-term sustainability of the cattle industry in China and elsewhere. No specific treatment or vaccine is currently available; thus, the development of a safe and effective vaccine is paramount. Here, we describe a strategy to assemble BNoV virus-like particles (VLPs) using the insect baculovirus expression system (BEV) to express the major structural protein, VP1, and demonstrate their potentiality as vaccines. The results showed that the BNoV-VLP self-assembled into complete spherical particles with a diameter of approximately 40 nm. When it was immunized in mice, the levels of specific IgG and IgA antibodies peaked at weeks 6 and 7 post-immunization, respectively, with maximum titers of 1:25,600 and 1:200. Moreover, we observed a significant increase in the CD4⁺/CD8⁺ T-cell ratio in splenic lymphocytes of immunized mice (p < 0.05), accompanied by a significant increase in TNF-α⁺CD4⁺ T-cells and TNF-α⁺CD8⁺ T-cells (p < 0.05). These results demonstrate that BNoV-VLPs are promising vaccine candidates for providing immunoprotection in the future. These studies support the significant practical implications of using a scientific basis for the development of a BNoV-VLP vaccine.