[Immunological and etiological aspects of a study of the Aina/1448 serotype of the tick-borne encephalitis virus].

Blood sera (1488 specimens) of the human population collected in the zone of isolation of tick-borne encephalitis (TBE) virus strains belonging to the Aina/1448 serotype were tested by the neutralization, hemagglutination-inhibition, agar gel diffusion and precipitation, and complement fixation tests with antigens of the Aina/1448 strain and prototype TBE virus strains representing the eastern and western serotypes. The dominating role of the Aina/1448 serotype in the formation of herd immunity in different areas of the forest-steppe and taiga zones of the Irkutsk region was established. Antibody to the Aina/1448 strain was found in the blood of the normal population and patients with acute and chronic forms of TBE. In TBE patients the percentage of virus-neutralizing antibody to the Aina/1448 strain was significantly higher (36.8%) than in the general population (16.6%). These are differences in the structure of immunity in vaccinees and nonvaccinees with TBE vaccine. Sera from the nonvaccinees reacted with the Aina/1448 strain more frequently, sera of the vaccinees more frequently contained antibody to different serotypes of TBE virus. Diagnostic problems and criteria of evaluation of the local antigenic variants of TBE virus are discussed.