Mouse adaptation of H6 avian influenza viruses and their molecular characteristics

Identification of key residues of B cell epitopes in hemagglutinin of H6 influenza A virus

IMPORTANCE

Since the escape immunity of influenza A viruses (IAVs) is mainly caused by the continuous antigenic variations in HA, the identification of key antigenic epitopes is crucial for better understanding of the escape immunity and vaccine development for IAVs. The antigenic sites of several HA subtypes, including H1, H3, H5, and H9, have been well characterized, whereas those of H6 subtype are poorly understood. Here, we mapped nine key residues of antigenic epitopes in H6 through escape mutants using a panel of MAbs. Moreover, MAbs 4C2 and 6E3, targeting 140 and 89 residues, respectively, could protect mice against lethal challenge of MA E-Teal/417. These key residues of antigenic epitopes identified here provide the molecular targets for further elucidating the antigenic evolution of H6 and better preparing the vaccine against H6 IAV.

Global distribution, receptor binding, and cross-species transmission of H6 influenza viruses: risks and implications for humans

The H6 subtype of avian influenza virus (AIV) is a pervasive subtype that is ubiquitously found in both wild bird and poultry populations across the globe. Recent investigations have unveiled its capacity to infect mammals, thereby expanding its host range beyond that of other subtypes and potentially facilitating its global transmission. This heightened breadth also endows H6 AIVs with the potential to serve as a genetic reservoir for the emergence of highly pathogenic avian influenza strains through genetic reassortment and adaptive mutations. Furthermore, alterations in key amino acid loci within the H6 AIV genome foster the evolution of viral infection mechanisms, which may enable the virus to surmount interspecies barriers and infect mammals, including humans, thus posing a potential threat to human well-being. In this review, we summarize the origins, dissemination patterns, geographical distribution, cross-species transmission dynamics, and genetic attributes of H6 influenza viruses. This study holds implications for the timely detection and surveillance of H6 AIVs.