FIG 4.

Alignment of the HA1 amino acid sequences of the vaccine and challenge viruses used in these studies. Orange shading, amino acids identified to be important for antigenic recognition by previous studies (41, 42, 44, 45, 75); blue shading, amino acids identified to be part of the receptor binding site; asterisks, potential N-linked glycosylation sites; red arrow, the proteolytic cleavage site; boxes, the loop at position 130, the helix at position 190, and the loop at position 220. Note that amino acids at positions higher than position 138 appear to have numbering 1 greater than their typical numbering due to an insertion in the A/turkey/England/N28/1973 isolate.