[Variability of the virulent properties of influenza A viruses in recombination].

The pattern of redistribution of human virulence in epidemic strains of influenza viruses in recombination with human avirulent strains was studied. In the course of recombination of epidemic and attenuated influenza virus strains variants with different human virulence were obtained. Some recombinants manifested enforced reactogenic properties as compared with the epidemic strain (X/28, M/35, and 0/26--H1N1, and 2P--H3N2). At the same time, recombinants No 19 (H1N1) and 1P (H3N2) with a similar set of surface antigens were innocuous for man after intranasal administration. Using the observed differences in sensitivity to remantadine as a marker of recombination, we obtained several sets of recombinants which had the antigenic structure of surface proteins of epidemic viruses and remantadine sensitivity of the other parent.