- Volume 66, Issue 8, 1985

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.

Antisera were raised against P3 (mol. wt. 32000), the full-length translation product of alfalfa mosaic virus (AlMV) RNA 3. P3 was made by translation in wheat germ extracts, using unfractionated AlMV RNA as message, and the products were then fractionated either by centrifugation through a sucrose gradient, or by phosphocellulose chromatography, each technique being followed by SDS-PAGE. Preparations made by each method were used in sequence to immunize a rabbit. The resulting antisera reacted on immunoblots with P3 synthesized in vitro, at dilutions of about 1:10000, but did not react with the translation products of AlMV RNA 1, RNA 2 or RNA 4. Although the antisera contained antibodies against some wheat germ components, most were removed by preabsorbing the antisera with the wheat germ extract. A minor wheat germ translation product of RNA 3, P′3, also reacted with the antisera. Since the mol. wt. of P′3 is apparently 1500 higher than that of P3, it is possible that P′3 is a readthrough product of the P3 cistron. With one antiserum preparation we were able to detect P3 in extracts of tobacco plants infected with AlMV.