Sialic acid receptors: focus on their role in influenza infection

Receptor-binding specificity is a major determinant of host range, pathogenesis, and interspecies transmission in influenza virus. Recognition of different conformations of sialic acid by the influenza virus hemagglutinin has driven influenza intra- and interspecies transmission for nearly 100 years since the first human pandemic was recorded in 1918. Key amino acid residues near or at the receptor-binding site of the hemagglutinin of different influenza A subtypes correlate with the ability of the virus to infect and replicate in the upper or lower respiratory tract of the host and transmit efficiently. A global concern exists for those highly pathogenic avian viruses that have emerged with the potential to cause a novel pandemic in humans. Studying the receptor-binding affinity to sialic acid receptors as a marker of pandemic risk could provide reliable measures to aid in timely pandemic planning and surveillance worldwide.