As a result of serial passages (42 passages) at low temperatures (26 degrees--28 degrees C) of two influenza H1N1 and H3N2 virus strains stable cold-adapted (ca) variants were produced. Investigations of them showed the ca A/USSR/03/84 (H1N1) variant to have ts-mutations in genes 1, 2, 4, 5, 7, and 8 and the ca A/USSR/215/79 (H3N2) to have ts-mutations in genes 1, 3, 4, 5, 7 and 8. These ca-variants may be recommended as attenuation donors to be used in recombination experiments with epidemic influenza viruses in order to obtain attenuated reassortant candidate vaccine strains.

Adaptation, Physiological↗

PubMedDate not supplied

[Production and properties of inhibitor-resistant mutants of influenza A virus recombinants].

Inhibitor-resistant (Ir) mutants could be selected from recombinants between influenza virus A/PR8/34 (H1N1) and A/Greifswald 6/74, A/Greifswald, 1/76, A/Erfurt 8/77 (all (H3N2)). Spontaneous mutants were selected by cultivation on chorioallantoic membrane fragments in roller tubes, in the presence of 10% inactivated rabbit serum. The Ir-mutants thus obtained were cloned during two successive plaque-to-plaque passages. The appearance of resistance to heat-stable rabbit serum inhibitors was concomitant with the development of resistance to inhibitors contained in guinea pig, horse and human sera. There was, however, no significant change in the resistance to calf serum inhibitors. Ir-mutants caused larger plaques in primary chick embryo fibroblasts, as compared with the initial inhibitor-sensitive (Is) recombinants. The yield in the infected chick embryo allantoic fluid (established by the hemagglutination test) was significantly higher in 2 out of 8 Ir-strains, as against the initial Is-strains. Hemagglutinins from three Ir/Is pairs were investigated by a bidimensional peptide-mapping technique. In one case there was a difference in the tryptic peptides of the Ir-mutant in comparison with those of the Is parental strain.

Animals↗