Amino
acid residues in the receptor binding site of these tr_SOIV were identical
to those of tr_SIV isolated from pigs in North America. Compared
with A(H1N1)pdm09, both cSOIV and tr_SOIV as well as SIV analyzed
have an alanine at position 227(H3 numbering), while the A(H1N1)
pdm09 viruses possess a glutamic acid at this position