FIG. 1.

NA and HA genes used to generate recombinant influenza A/WSN viruses. (A) Schematic diagram of the influenza B/Yamagata/16/88 and A/WSN/33 parental and chimeric NA genes showing the ORFs of the NAs. NCRs are indicated by lines. CT, cytoplasmic tail; EC, ectodomain; TM, transmembrane domain. In BNA/A65 and BNA/ACT-ATM the NCRs have been extended by insertion of 65 nt into the 3′ NCR (nt 20 to 84) and insertion of 36 nt (nt 1298 to 1333) into the 5′ NCR, respectively. Flu B wt NA, influenza B/Yamagata wild-type virus NA; Flu A wt NA, influenza A/WSN wild-type virus NA. The asterisk in Flu B wild-type NA indicates the position of the start codon of the NB protein which is upstream of that of the NA protein. This upstream sequence coding for the amino terminus of the NB protein is not included in the chimeric constructs. (B) Schematic representation of the influenza B/Yamagata/16/88 and A/WSN/33 virus HA and the chimeric BHA-ACT/ATM segments. Flu B wt HA, influenza B/Yamagata wild-type virus HA; Flu A wt HA, influenza A/WSN wild-type virus HA. The ORFs are shown as boxes. The NCRs are represented as lines. CT, cytoplasmic tail; EC, ectodomain; TM, transmembrane domain. For details, see Materials and Methods.