Comparative analysis of the biophysical characteristics of influenza A virus variants with differing pathogenicity for mice

: Variants of influenza A virus: A/PR8/34 Pm-, nonpathogenic for mice and A/PR8/34 Pm+, pathogenic for mice, obtained after 5 passages in mice, were studied. Both variants showed close similarities in the antigenic specificity, high reproductive activity at optimal temperature and reduced activity at low and high temperatures, similar plaque-producing activity in chick fibroblast cell cultures. Differences in their polypeptide composition were found. The A/PR8/34 Pm+ variant had no HAO and a lower molecular weight of HA1. In the mapping of HA1 and NP proteins, differences in the oligopeptide compositions were observed.