Fourteen mouse
monoclonal antibodies raised against tick-borne encephalitis virus (TBEV) and polyclonal
antisera raised against six other flaviviruses, Edge Hill (EHV),
Japanese encephalitis (JEV), Langat (LGTV),
louping ill (LIV), West Nile (WNV) and
yellow fever (YFV), were tested for their ability to enhance the replication of TBEV in cells of the mouse macrophage-like line P388 D1, and for their reactivity in ELISA and haemagglutination inhibition (HI) tests. Irrespective of their specificity for either the 51K or 58K
polypeptide present in TBEV-infected cells, 13 of the 14
monoclonal antibodies enhanced the replication of TBEV but not of WNV. The remaining
monoclonal antibody, which immunoprecipitated the 58K
polypeptide of TBEV enhanced WNV but not TBEV, although it reacted strongly with both viruses in ELISA and HI tests. Only polyclonal
antisera against viruses within the tick-borne encephalitis virus complex (TBEV, LGTV and LIV) enhanced TBEV replication, although all the polyclonal
antisera reacted with TBEV by ELISA; two (against JEV and WNV) also reacted by HI test and all enhanced the replication of WNV. These findings suggest that with TBEV, enhancement may be TBEV complex-specific rather than flavivirus-specific. Data derived from testing both polyclonal and
monoclonal antibodies suggest further that not all
antibodies that bind to the envelope
glycoprotein of TBEV are able to enhance the replication of TBEV, and that enhancement is
epitope-specific.