Changes of quasispecies composition on HA level of Influenza A/PR/8/34 (H1N1) (RKI, A) and (NIBSC, B) during virus adaptation.

Passage 1 represents the MDCK cell adapted seed virus. Passage 6 represents the last of five successive virus passages in Vero cells. Passage 11 represents the last of five subsequent passages in MDCK cells, i.e. after final back-adaptation. 0% values correspond to below the detection limit. (A) In passage 6 and 11 of the PR/8/34 (RKI) the two substitutions at amino acid positions 457 and 460 are uncoupled. (B) In the first passage of the PR/8/34 (NIBSC) the two substitutions D455Y and N460D are uncoupled.