A ferritin-based mosaic-like nanovaccine elicits effective cross-protection against H1N1 and H3N2 swine influenza viruses

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.