MONOCLONAL-ANTIBODIES SPECIFIC FOR POTATO MOP-TOP VIRUS, AND SOME PROPERTIES OF THE COAT PROTEIN

A method was devised which gave consistent yields (1-2 mg/kg leaves) o f potato mop-top furovirus (PMTV) particles. Monoclonal antibodies (MA bs) were produced and some properties of 10 of them were studied. Four MAbs readily detected PMTV isolates from six countries in Northern Eu rope and Japan when the isolates were trapped with polyclonal antibody ; and diagnostic tests based solely on MAbs (SCR 68 to coat plates and biotin- or enzyme-labelled SCR 69 to detect trapped virus) were devis ed. The pattern of reactions of the MAbs in ELISA and immunoblots sugg ested that they react with at least five different epitopes. PMTV coat protein preparations were analysed by sodium dodecyl sulphate polyacr ylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Three bands of 23.9 kd, 21.5 kd and 20.5 kd were visible in silver-stained gels a nd all three reacted with PMTV specific MAbs. The relative amounts of the three bands varied between different virus preparations, but the 2 1.5 kd band was usually the most abundant. The three bands were probab ly not produced by anomalous behaviour in SDS-PAGE. Moreover PMTV prot ein was readily degraded by trypsin treatment giving a band of 20.5 kd . Therefore the results suggest that PMTV coat protein sub-units are s ensitive to degradation by plant proteases. At least two degraded form s were found when purified preparations were analysed by SDS-PAGE, and the undegraded protein was estimated to be 23.9 kd. The PMTV MAbs did not react in immunoblots with SDS-treated coat protein preparations o f beet necrotic yellow vein furovirus or Indian peanut clump furovirus .