Characterization of antigenic variants of tick-borne encephalitis virus selected with neutralizing monoclonal antibodies

Antigenic variants of tick-borne ncephalitis virus were selected by the use of six neutralizing monoclonal antibodies (MAbs), each defining a different epitope of the envelope glycoprotein E. These variants were characterized with respect to antigenic changes by analysing the binding of each of 18 precisely mapped MAbs in ELISA and haemagglutination inhibition tests. The results yielded information about interrela-tions between epitopes exceeding that obtained previously from competitive binding studies. In addition, variants were tested for their specific haemagglutination activities, which revealed a significant reduction of this functional activity in one of the variants. Tick-borne ncephalitis (TBE) virus is a human pathogen which is endemic in many parts of Europe and Asia. As is typical for a flavivirus, mature virus particles contain three different proteins, the capsid protein C, the membrane protein M, and the envelope protein E (for review, see Rice et al., 1986). The E protein is a glycoprotein of Mr 55K that is capable of inducing a protective immune response invivo. Moreover, it mediates receptor-specific v rus attachment to the cell surface in vivo, as well as haemagglutination (HA) of erythrocytes at acid pH (optimu