Antigenic Analysis of the Coat Protein of Alfalfa mosaic virus and its Involvement in Aphid Transmission

Two strains -425 and Y87/47- of Alfalfa mosaic virus (AMV) were propagated in and purified from Nicotiana tabacum cv. Samsun NN. Thirty-three AMV specific monoclonal antibodies (MAbs) from two fusions were raised against strain 425. These antibodies were of isotypes IgG1 and IgM. MAbs recognised three types of epitope. Group I did not react with the virus particle surface or viral coat protein of two strains in PTA-ELISA, but they reacted with a 30-kDa structural coat protein of AMV by immunoblot analysis only and were able to recognise cryptotopes. Group II reacted with metatopes of both strains in PTA-ELISA. Group III reacted with a 30-kDa structural coat protein of AMV by immunoblot analysis and in PTA-ELISA for the Y87/47 strain only. Immunoblocking experiments in which suspensions of purified AMV and MAb were offered between parafilm membranes for acquisition by Myzus persicae revealed that MAb-2 was effective in blocking (inhibiting) transmission. This result suggests that the epitope which was localised by MAb-2 plays a role in the aphid transmission of AMV.