[Antigenic variability of avian influenza virus A/H13, isolated in the USSR]. / Antigennaia varibel'nost' virusov grippa ptits A/H13, izolirovannykh v SSSR.

The antigenic structure of influenza H13 viruses isolated from wild birds in the USSR in 1976-1985 was studied. Antiserum against the reference A/gull/Maryland/704/77 (H13N6) strain was used to demonstrate the antigenic variations among the viruses. The homology of nucleotide sequences in the region 99-215 for the two A/H13N6 strains, A/gull/Maryland/704/77 and A/great black-headed gull/Astrakhan/227/84, were 75% and 86%, respectively. The 9-base segment deletion in A/grey black-headed gull/Astrakhan/277/84 was observed. Comparison of the predicted amino acid sequences of the strains' hemagglutinin in the appropriate region (amino acids 2-40) revealed 5 replacements (86% homology). Two replacements of arginine by lysine and asparagine by serine in positions 15 and 16, respectively, are the most significant. The latter replacement is accompanied by a change in the glycosylation site and might alter its three-dimensional structure. Further studies of the isolate genome are under way.

[Circulation of the influenza A virus of H13 serosubtype among seagulls in the Northern Caspian (1979-1985)]. / Tsirkuliatsiia virusa grippa A seropodtipa H13 sredi chaikovykh ptits severnogo kaspiia (1979-1985 gg.).

The results of seven-year ecologo-virological studies (1979-1985) of Laridae colonies on the island Zhemchuzhnyi, northern Kaspian Sea, showed annual isolation of influenza A viruses. Altogether, 95 hemagglutinating agent have been isolated. Strains with 4 different combinations of surface antigens were identified: H5N2, H13N2, H13N3, H13N6. The possibility of transovarial transmission is confirmed by the fact of isolation of an influenza virus strain A/black-headed herring gull/Astrakhan/458/85 (H13N6) from a nestling having no contacts with the environment. Simultaneous circulation of influenza A viruses (in 1983--H13N2 and H13N6, in 1985.--H13N3 and H13N6) and the presence in the virion of neuraminidase of human influenza virus (N2) allow to consider the isolates to be natural recombinants.