Genetic stability of cold-adapted A/Leningrad/134/47/57 (H2N2) influenza virus: sequence analysis of live cold-adapted reassortant vaccine strains before and after replication in children

1 Influenza Branch G-16, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA 2 Research Institute for Viral Preparations, Russian Academy of Medicial Sciences, Moscow 109088, Russia and 3 Research Institute for Experimental Medicine, Russian Academy of Medical Sciences, St Petersburg 197022, Russia We previously reported that the A/Leningrad/134/47/57 (H2N2) cold-adapted virus (A/Len/47) used in preparing reassortant live attenuated vaccines for children acquired 14 (11 coding) mutations in genes coding for proteins other than haemagglutinin and neuraminidase during cold-adaptation. Preservation of these mutations in genomes of viruses isolated from children on the second, fifth, or eighth day after vaccination was examined by sequence analysis. The sequence data demonstrated that all nine coding mutations selected for examination were conserved in the genomes of all 11 strains investigated, indicating that the mutations accompanying cold-adaptation and attenuation of the A/Len/47 master vaccine are highly stable. * Author for correspondence. Fax +1 404 639 2334. e-mail njcl@ciddvdl Received 24 October 1994; accepted 21 February 1995.