[Antigenic variability of avian influenza virus A/H13, isolated in the USSR]

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.