Selection of H3 avian influenza viruses with SAα2,6Gal receptor specificity in pigs

Avian influenza viruses possess hemagglutinin (HA) which preferentially bind to the sialic acid alpha 2,3-galactose sialyloligosaccharides (SA alpha 2,3Gal) receptor. In contrast, human influenza viruses bind to sialic acid alpha 2,6-galactose sialyloligosaccharides (SA alpha 2,6Gal). The A/Hong Kong/68 (H3N2) virus preferentially binds to SA alpha 2,6Gal, although its HA gene was derived from an avian influenza virus strain. To elucidate the mechanisms behind acquisition of binding specificity for the human-type receptor, the avian influenza virus, A/duck/Hokkaido/5/77 (H3N2), which carries the HA with SA alpha 2,3Gal receptor specificity, was consecutively passaged in pigs. Viruses that preferentially bind to the SA alpha 2,6Gal receptor were predominantly recovered from the nasal swabs of pigs after three passages. The present results indicate that avian influenza Viruses can acquire the potential to infect humans after multiple infections in a pig population. Intensive surveillance of swine influenza is, thus, important for the preparedness for the future pandemics. (C) 2013 Elsevier Inc. All rights reserved.