[Changes in the biological properties of influenza virus (HON1) strains virulent for mice when exposed to homologous antibodies].

A decrease in the virulent properties of two influenza virus strains (A/PR/8/34 and A/Mel/35 (HON1) pathogenic for mice was demonstrated in multiple passages in chick embryos in the presence of homologous antibody. The artificially developed avirulent A/PR/8/240 and A/Mel/375 variants had low immunogenic activity and a marked temperature sensitivity to 40 degrees C. Common ts mutations in the genomes of these avirulent variants located in genes 1 and 7 coding for P3 and M proteins were demonstrated.