Recombinant cold-adapted attenuated influenza A vaccines for use in children: Molecular genetic analysis of the cold-adapted donor and recombinants

Abstract

A previously described cold-adapted attenuated virus, A/Leningrad/134/17/57(H2N2), was further modified by 30 additional passages in chicken embryos at 25°C. This virus had a distinct temperature-sensitive (ts) phenotype, grew well in chicken embryos at 25°C, and failed to recombine with reference ts mutants of fowl plague virus containing ts lesions in five genes coding for non-glycosylated proteins (genes 1, 2, 5, 7, and 8). Recombination of A/Leningrad/134/47/57 with wild-type influenza virus strains A/Leningrad/322/79(H1N1) and A/Bangkok/1/79(H3N2) yielded ts recombinants 47/25/1(H1N1) and 47/7/2(H3N2). These recombinants inherited their ts phenotype and ability to reproduce in chicken embryos at 25° C from the cold-adapted parent. Analysis of the genome composition of the recombinants obtained by recombination of the cold-adapted donor with wild-type influenza virus strains A/Leningrad/322/79(H1N1) and A/Bangkok/1/79(H3N2) showed that recombinants 47/25/1(H1N1) and 47/7/2(H3N2) inherited five and six genes, respectively, from the cold-adapted parent, and hemagglutinin and neuraminidase genes from the wild-type strains.