IMMUNOGENICITY FOR MICE OF ATTENUATED REASSORTANTS OF A/LENINGRAD/134/47/57 (H2N2) INFLUENZA-VIRUS WITH DIFFERENT GENOME COMPOSITION

Reassortants of cold-adapted strain A/Leningrad/134/47/57 (H2N2) and virulent strain A/PR/8/34 (H1N1), modeling genomic composition of vaccinal strains, were tried in mouse experiments. Reassortants' genomes included the major part (5, 6, or 7) from cold-adapted strain and 1 to 3 genes of virulent strain. All the tested reassortants did not differ by temperature sensitivity or cold adaptation phenotypes, did not cause the death of mice, but differed by the level of reproduction in murine lungs and by immunogenicity. Strains with genomic formulas 6/2 (HA and NA of a virulent strain) and 5/3 (M) (HA, NA, and M of a virulent strain) were characterized by the highest immunogenicity. Reassortants including, besides HA and NA, PA gene 5/3 (PA) or inheriting only HA gene from strain A/pr/8/34 (H1N1) were hyperattenuated and immunogenic.