A species barrier for the influenza A virus is the differential expression of sialic acid， which can either be α2，3-linked for avians or α2，6-linked for human viruses. The influenza A virus hosts also express other species-specific sialic acid derivatives. One major modification at C-5 is N-glycolyl (NeuGc)， instead of N-acetyl (NeuAc). N-glycolyl is mammalian specific and expressed in pigs and horses， but not in humans， ferrets， seals， or dogs. Hemagglutinin (HA) adaptation to either N-acetyl or N-glycolyl is analyzed on a?sialoside microarray containing both α2，3- and α2，6-linkage modifications on biologically relevant N-glycans. Binding studies reveal that avian， human， and equine... More
A species barrier for the influenza A virus is the differential expression of sialic acid， which can either be α2，3-linked for avians or α2，6-linked for human viruses. The influenza A virus hosts also express other species-specific sialic acid derivatives. One major modification at C-5 is N-glycolyl (NeuGc)， instead of N-acetyl (NeuAc). N-glycolyl is mammalian specific and expressed in pigs and horses， but not in humans， ferrets， seals， or dogs. Hemagglutinin (HA) adaptation to either N-acetyl or N-glycolyl is analyzed on a?sialoside microarray containing both α2，3- and α2，6-linkage modifications on biologically relevant N-glycans. Binding studies reveal that avian， human， and equine HAs bind either N-glycolyl or N-acetyl. Structural data on N-glycolyl binding HA proteins of both H5 and H7 origin describe this specificity. Neuraminidases can cleave N-glycolyl efficiently， and tissue-binding studies reveal strict species specificity. The exclusive manner in which influenza A viruses differentiate between N-glycolyl and N-acetyl is indicative of selection.
