Abstract
Swine influenza viruses (SIVs), particularly the H1N1 and H3N2 subtypes, pose ongoing threats to the swine industry and global public health. Current commercial vaccines generally provide limited cross-protection against heterologous viruses due to the frequent antigenic drift and shift in SIVs, highlighting the need for broad-spectrum vaccines. Self-assembling nanoparticles (NPs) can elicit strong and broad immune responses, representing a promising platform for the development of broad-spectrum nanovaccines. In this study, two newly-screened conserved epitopes (H1-3 and H1-5) and (H3-1 and H3-3) in hemagglutinin (HA) of the H1 and H3 subtypes, along with a highly conservative matrix protein 2 ectodomain (M2e), were displayed on ferritin NP in cocktail and mosaic forms, respectively, and were designated MHF-cocktail (MHFc) and MHF-mosaic (MHFm) nanovaccines. Under a prime-boost immunization strategy in a mouse model, the MHFm nanovaccine induced a higher antigen-specific IgG mediated antibody dependent cellular cytotoxicity (ADCC) than the MHFc nanovaccine, and significantly enhanced antigen-specific multifunctional CD4⁺ and CD8⁺ T cell responses as well as cytotoxic T-cell activity. Enzyme-linked immunosorbent spot proliferation assays indicated that splenic lymphocytes generated following vaccination with the MHFm nanovaccine exhibited enhanced proliferative capacity and secreted higher levels of interleukin-4 (IL-4) and interferon-γ (IFN-γ) compared with those from the MHFc nanovaccine. In mice, MHFm nanovaccine provided complete cross-protection against lethal H1N1 and H3N2 SIV challenge, while MHFc nanovaccine offered partial cross-protection. This study provides a potential strategy for designing and developing cross-protective vaccines against H1N1 and H3N2 SIVs.