[The NS gene--a possible determinant of apathogenicity of a cold-adapted donor of attenuation A /Leningrad/134/47/57 and its reassortants].

Phenotypical properties of single-gene reassortants of attenuated cold-adapted strain A/Leningrad/135/47/57 (H2N2) and strain A/PR8/34 virulent for laboratory animals were studied. Only the group of reassortants inheriting NS gene from cold-adapted virus was fully attenuated for various animals species, similarly as reassortants with 6/2 genomic formula containing all the 6 internal protein genes from strain A/Leningrad/134/47/57. Reassortant 25A-1 single-gene for NS was temperature-sensitive (ts) on mammalian cells but formed plaques at 40 degrees C on chicken kidney cells.

[Immunogenicity of attenuated reassortants of influenza A virus /Leningrad/134/47/57 (H2N2) for mice, depending on their genome].

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.

[Variations in the temperature range for reproduction of virulent and attenuated cold-adapted influenza A viruses].

The informativity of RCT40, RCT37.5, and RCT25 markers for differentiation of wild type strains from ca-recombinants obtained on the basis of ca donors of attenuation was studied. The RCT25 marker and express RCT37.

Study of live recombinant cold-adapted influenza bivalent vaccine of type A for use in children: an epidemiological control trial.

Live cold-adapted recombinant bivalent vaccine of influenza type A was studied in a controlled field trial in 1982-1983 among nearly 30,000 children 3-15 years old. The bivalent vaccine consisted of recombinants 47/25/1 (H1N1) and 47/7/2 (H3N2) of wild-type viruses A/Brazil/11/78 (H1N1) and A/Bangkok/1/79 (H3N2) with cold-adapted donor A/Leningrad/134/47/57 (H2N2). The recombinants which received mutant nonglycoprotein genes from cold-adapted donor did not suppress each other after simultaneous inoculation of children and stimulated antibody response to both strains.