Intranasal and intramuscular H5-Matrix-M nanoparticle vaccines protects against highly pathogenic H5N1 influenza virus in mice

The emergence of clade 2.3.4.4b highly pathogenic H5N1 influenza virus in dairy cows and transmission to humans has heightened public health concerns. In this work, we characterized the immunogenicity and efficacy of a Matrix-M®-adjuvanted nanoparticle protein vaccine containing recombinant H5 HA of A/American wigeon/South Carolina/22/000345-001/2021 virus (clade 2.3.4.4b, H5-MNP). In naïve mice, intranasal or intramuscular vaccination with H5-MNP induced robust H5 binding and virus neutralizing antibody responses and protected against a lethal H5N1 challenge (A/Michigan/90/2024, clade 2.3.4.4b). In mice primed with seasonal influenza vaccine, one dose of H5-MNP vaccine provided similar levels of protection, with fewer breakthrough infections detected in the upper airways of mice that received the H5-MNP intranasally compared to those that were immunized intramuscularly. This novel H5-MNP vaccine technology could potentially induce protective immunity against pandemic influenza viruses in individuals with pre-existing seasonal influenza HA immunity.