Sialic Acid Bound Influenza A Viral Particle Cleaved HA Influenza A Viral Particle Binding of the influenza virion to the host cell GENE ONTOLOGYGO:0046718 Influenza viruses bind via their surface HA (hemagglutinin) to sialic acid in alpha 2,3 or alpha 2,6 linkage with galactose on the host cell surface. Sialic acid in 2,6 linkages is characteristic of human cells while 2,3 linkages are characteristic of avian cells. The specificity of influenza HA for sialic acid in alpha 2,6 or alpha 2,3 linkages is a feature restricting the transfer of influenza viruses between avian species and humans. This species barrier can be overcome, however. Notably, passaged viruses adapt to their host through mutation in the receptor binding site of the viral HA gene. Pubmed0 Pubmed10366560 Pubmed12954214 Pubmed7975212 Reactome Database ID Release 43168272 Reactome, http://www.reactome.org ReactomeREACT_6232