Figure 1

Amino acid sequence alignment of the mature hemagglutinin (H) proteins of Influenza H1N1 2009 and its predecessor H1N1 isolated in 2008. The amino acid sequence of the H protein shown for the Influenza H1N1 2009 virus is derived from the segment 4 sequence of the isolate A/California/08/2009(H1N1) submitted from the CDC by Shu et al. on April 29, 2009, as Genbank FJ971076. The sequence for Influenza H1N1 2008 is derived from the segment 4 sequence of the isolate A/District of Columbia/WRAMC-1154048/2008(H1N1) submitted from Walter Reed Army Institute of Research by Houng et al., collected from a patient on February 1, 2008, as Genbank CY038770. Only the sequences of the mature proteins, after cleavage of the signal sequence, are shown. Standard single-letter abbreviations for the amino acids are used. The collinear sequences were hand-aligned and also confirmed by online use of ClustalW. Amino acid positions showing differences between the two sequences are denoted with an “X”. There are 89 differences in 327 positions, or 27.2%. The canonical sites for N-linked glycosylation are underlined. Amino acid regions contributing to each of five antigenic sites are labeled Site A through Site E.