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Figure. Partial HA1 domain cDNA sequences from five 1918-19 cases.
A 563-bp fragment encoding antigenic (19,20)
and receptor-binding (21) sites of the HA1
domain is shown, with the sequences aligned to A/Brevig Mission/1/1918
(BREVIG18) (15). Dots represent sequence
identity as compared to BREVIG18. The numbering of the nucleotide sequence
is aligned to A/PR/8/1934 (GenBank accession no. NC_002017) and refers
to the sequence of the gene in the sense (mRNA) orientation. The partial
HA1 translation product for BREVIG18 is shown above its cDNA sequence.
Amino acid numbering is aligned to the H3 HA1 domain (15).
Boxed amino acids indicate potential glycosylation sites as predicted
by the sequence (15). Residues that have
been shown experimentally to affect receptor-binding specificity in H1
HAs, D77, A138, P186, D190, L194, and D225 (21–23)
are indicated by a white diamond symbol above these six residues. Residues
defining four antigenic sites are indicated: Cb (black circle),
Sa (black square), Sb (black diamond), and Ca
(black triangle) (19,20). Residues that have
been mapped to both receptor-binding and antigenic sites (positions 194
and 225) are marked with two symbols. When a nucleotide change as compared
to BREVIG18 results in a changed amino acid, the resultant amino acid
is shown in lower case to the right of the BREVIG18 residue. Strain abbreviations
and GenBank accession numbers: A/Brevig Mission/1/1918 (BREVIG18, # AF116575),
A/South Carolina/1/1918 (SC18, # AF117241), A/New York/1/1918 (NY18, #
AF116576), A/London/1/1918 (LONDON18, # AY184805), and A/London/1/1919
(LONDON19, # AY184806).
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