[Nonvirion (soluble) antigen of the tick-borne encephalitis virus]

Immunoelectrophoretic analysis of the cells destroyed as a result of infection with tick-borne encephalitis virus showed a considerable portion of nonvirion ("soluble") antigen to remain associated with cell membranes and to be released after treatment of the cells with detergents. After treatment with nonionic detergents, the nonvirion antigen showed electrophoretic heterogeneity in immunoelectrophoresis, and after treatment with sodium dodecyl-sulphate behaved as a homogeneous population of protein molecules. Using radioactively labeled carbohydrate precursors, lipids, and RNA, the nonvirion antigen was demonstrated to be a complex structure: a membrane-containing ribonucleoprotein. The immunoprecipitation of proteins by means of antibodies ligated to CNBr-activated sepharose confirmed that protein NV 5 (p93) of tick-borne encephalitis virus was an antigenically active component of the nonvirion antigen. This protein was found to undergo proteolytic cleavage in immunochemical reaction. The possible role of the nonvirion antigen in reproduction of flaviviruses is discussed.