Recombinant Erns-E2 protein vaccine formulated with MF59 and CPG-ODN promotes T cell immunity against bovine viral diarrhea virus infection

To obtain an effective vaccine candidate against bovine viral diarrhea virus (BVDV) disease which causes great economical loss in cattle industries, recombinant E^rns-E2 protein vaccine containing MF59 and CPG-ODN adjuvants was prepared and assessed in this study. The recombinant plasmid (pET32a-E^rns-E2) was constructed and transformed into BL21 (DE3) cells to produce E^rns-E2 protein. We immunized mice with the MF59–and CPG-ODN–adjuvanted recombinant E^rns-E2 protein, E2 protein, or E^rns protein, respectively. To evaluate immunogenicity and efficacy of a vaccine-adjuvant combination, mice were challenged with BVDV BJ175170 strain after immunization. All adjuvanted vaccines elicited detectable humoral and cellular immune responses, the BVDV-specific antibody titers as well as interleukin 4 (IL-4) levels in sera of mice immunized with the recombinant E^rns-E2 protein were higher than in those of mice immunized with either the recombinant E^rns or E2 protein. Besides, immunization with the E^rns-E2 vaccines induced higher percentage of CD4⁺IFN-γ⁺, CD8⁺IFN-γ⁺ T cells and CD3⁺TNF-α⁺ T cells compared with the other vaccines. More protective efficacy against BVDV infection was acquired in the mice treated with the recombinant E^rns-E2 protein, as shown by a reduction of viremia and slight pathological changes compared with both the control mice and the other vaccinated mice. Our findings suggest that the use of the recombinant E^rns-E2 protein vaccine formulated with MF59 and CPG-ODN adjuvants enhances T cell responses and viral control, which warrants the E^rns-E2 protein vaccine-adjuvant combination could be as a vaccine strategy to against BVDV.