TABLE 1.
Chimeric virusesa
All strains were rescued on a PR8 background. Group 1 HA heads, green; group 1 HA stalks, red; group 2 HA heads, purple; group 2 HA stalks, blue. HA sequences were amplified from the reference strains, which included A/Puerto Rico/8/34 (H1), A/California/04/09 (H1), A/Singapore/1/57 (H2), A/Perth/16/09 (H3), A/Hong Kong/1/68 (H3), A/duck/Czech/56 (H4), A/VN/1203/04 (H5), A/mallard/Sweden/81/02 (H6), A/mallard/Alberta/24/01 (H7), A/mallard/Sweden/24/2002 (H8), A/guinea fowl/Hong Kong/WF10/99 (H9), A/mallard/Interior Alaska/10BM01929/2010 (H10), A/shoveler/Netherlands/18/1999 (H11), A/mallard/Interior Alaska/7MP0167/2007 (H12), A/black headed gull/Sweden/1/1999 (H13), A/mallard/Gurjev/263/1982 (H14), A/shearwater/West Australia/2576/1979 (H15), and A/black headed gull/Sweden/5/1999 (H16) viruses. HA sequences were confirmed by Sanger sequencing. All recombinant viruses contained the regular low-pathogenicity H1 or H3 cleavage sites. Asterisks denote cross-group head/stalk combinations.