An epitope-based peptide vaccine targeting influenza a elicits robust immune responses and induces protection in a...

Influenza A viruses remain a major global public health threat due to their high mutation rates, antigenic drift, and periodic antigenic shift, which collectively undermine the effectiveness of seasonal vaccines. Conventional influenza vaccines necessitate frequent reformulation and often result in suboptimal protection. Epitope-based vaccine strategies that focus immune responses toward conserved viral regions represent a promising approach for inducing broader and durable immunity. In this study, reverse vaccinology and immunoinformatics-guided approaches were used to design multi-epitope vaccine constructs derived from conserved regions of Influenza A H3N2 and H1N1 proteins, including hemagglutinin (HA), neuraminidase (NA), nucleoprotein (NP), and matrix proteins (M1 and M2). BALB/c mice were immunized intramuscularly and evaluated for humoral and cellular immune responses. Serum IgG levels were measured by ELISA, while functional antibodies were assessed using hemagglutination inhibition (HAI) assays. Cellular immune responses were evaluated using ELISPOT assays for IFN-γ and TNF-α secretion. Protective efficacy was assessed through homologous viral challenge with H3N2 or H1N1 strains, followed by survival analysis and lung histopathological examination. Immunization with H3N2- and H1N1-derived epitopes elicited robust specific IgG responses and induced functional HAI antibodies. Notably, H3N2-derived epitopes generated higher HAI titers, consistent with enhanced humoral immunogenicity. Vaccinated mice demonstrated strong cellular immune responses, characterized by significantly elevated IFN-γ-producing CD8⁺ T cells compared with mock-immunized controls. Upon viral challenge, all vaccinated mice exhibited 100% survival against H3N2 or H1N1 infection, whereas mock-immunized mice experienced 100% mortality. Histopathological analysis revealed protective immunopathological profiles and preserved alveolar architecture. The protective efficacy of the multi-epitope vaccination was comparable to that of the seasonal quadrivalent influenza vaccine. This study demonstrates that multi-epitope vaccines derived from conserved Influenza A proteins can induce coordinated humoral and cellular immune responses and confer robust protection against H3N2 and H1N1 viral challenge in a mouse model. This suggests support for peptide-based vaccination as an alternative method to conventional strain-matched vaccines, which reduce vaccine effectiveness or universal influenza vaccine development.