Apoferritin nanoparticle based dual-antigen influenza conjugate vaccine with potential cross-protective efficacy against heterosubtypic influenza virus

Ferritin nanoparticles with self-assembling properties have been widely explored as vaccine carrier by displaying foreign antigens through genetic fusion strategy. In the present work, an apoferritin (AFt) nanoparticle was tested as influenza vaccine carrier by chemically conjugating a matrix protein 2 ectodomain (M2e) antigen peptide or/and the full-length hemagglutinin (HA) antigen on the outer surface of the AFt, with heterobifunctional sSMCC or SM(PEG)24 containing PEG chain as linkers. To each AFt nanoparticle, about 30-32 M2e or 1.8 HA antigen could be coupled. The AFt-(PEG)24-M2e, in which the M2e was coupled through SM(PEG)24 containing PEG chain, conferred higher protective efficacy in immunized mice than AFt-M2e did, but was less effective than AFt-(PEG)24-HA. When both M2e and HA were coupled, the synthesized dual-antigen vaccine candidate AFt-(PEG)24-M2e/HA elicited high level of M2e and HA antigen-specific antibodies and conferred 100% protection against lethal infection of homologous PR8 H1N1 virus strain and 70% protection against a heterologous A/FM/1/47 (FM1, H1N1) strain, which was more effective than the M2e or HA single antigen vaccine candidates. The potential cross-protective effect of the dual-antigen vaccine was further demonstrated by significant specific hemagglutination inhibition (HAI) titers in serum of the immunized mice against three other heterologous viral strains including A/Singapore/GP1908/2015 (IVR-180) H1N1, A/Anhui/1/2005 H5N1, and A/Hong Kong H3N2.