SEQUENCE CHANGES IN THE LIVE ATTENUATED, COLD-ADAPTED VARIANTS OF INFLUENZA A LENINGRAD 134 57 (H2N2) VIRUS

Nucleotide sequences were determined for the RNA segments coding for proteins other than the hemagglutinin and neuraminidase of the A/Leningrad/134/57 (H2N2) wild-type (A/Len/wt) virus and its two cold-adapted (ca) and attenuated variants, A/Leningrad/134/17/57 (A/Len/ 17/ca) and A/Leningrad/134/47/57 (A/Len/47/ca) that are used in the U.S.S.R. in the preparation of reassortant live attenuated vaccines. Ten nucleotide differences were detected between the sequences of the A/Len/wt and A/Len/17/ca viruses; of these, eight were deduced to encode amino acid (aa) substitutions. One as substitution each was predicted for the PB2, M1, M2, and NS2 proteins, whereas two as substitutions each were predicted for the PB1, and PA proteins of the A/Len/17/ca virus. Four additional nucleotide changes were found in the genome of the A/Len/47/ca virus; three of these were deduced to code for one additional as substitution each for the PB2, PB1, and NP proteins. © 1992.