The Q226H Mutation in Avian H5N1 Hemagglutinin Mediates a Path towards Structural Adaptation in Humans
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The global outbreak of highly pathogenic avian influenza (HPAI) A(H5N1) among birds and the spillover to mammals increases the risk for humans. A recent case in British Columbia with a clade 2.3.4.4b H5 virus infection revealed a mixture of 226Q/H in the receptor-binding site of hemagglutinin. While significant changes in pre-existing immunity by H1 or H3 polyclonal sera are not evident, we show that the Q226H mutation enables binding to human-type a2-6 sialic acid receptors. High-resolution cryo-EM structures provide a basis for the alteration in receptor preference and show that a possible path towards human adaptation also requires a conformational change of the bound a2-6-sialylated glycan. Continued surveillance for additional mutations that could enhance this phenotype is warranted.
