Augmentation of humoral and cell-mediated immune responses by recombinant rabies virus expressing canine Fc

Rabies virus (RV) infection causes a fatal neurological disease affecting both animals, particularly canines, and humans. As a novel approach, canine Fc fusion protein into a recombinant RV may enhance both humoral and cellular-mediated immunity and is expected a promising strategy for vaccine development and therapeutic interventions. To enhance the immunogenicity of a traditional rabies vaccine, we generated a recombinant RV-expressing canine Fc fusion protein (RV-Fc) by cloning the RV-Fc fusion gene into the pcDNA3 vector and expressing the recombinant protein in Vero cells, yielding a protein of approximately 42 kDa. The expression of the recombinant RV-Fc protein was confirmed via immunocytochemistry and Western blot analysis. To evaluate the induction of immune responses such as antibody and cytokine production, we performed experiments using RV and RV-Fc immunized mice model. Serum neutralization (SN) assays demonstrated that cells treated with RV-Fc elicited higher antibody titers compared to cells treated with RV alone at week 1 post-treatment (p = 0.036). ELISA revealed a statistically significant increase in humoral immune responses in mice immunized with the RV-Fc vaccine compared to those immunized with the RV vaccine. This increase was observed for IgM at week 4 (p = 0.016), IgA at week 1 (p = 0.010), and IgG at both week 1 (p = 0.027) and week 4 (p = 0.006) post-immunization. Furthermore, analysis of cytokine levels demonstrated significant elevation in both IL-4 (p = 0.020) and IL-12 (p = 0.023) in the RV-Fc group relative to the RV group. Mice infected with RV-Fc exhibited enhanced humoral immune responses, as evidenced by increased levels of CD3 T cells (p = 0.039), B220/CD3 (B/T) cells (p = 0.018), and CD4 B cells (p = 0.044) compared to mice infected with RV alone. These findings suggest that the RV-CFc vaccine candidate holds promise for enhancing both cellular and humoral immune responses, potentially offering improved protection against rabies virus infection.