Mapping antigenic epitopes of potato virus A using monoclonal antibodies and overlapping synthetic peptides

Six mouse monoclonal antibodies (MAbs) against potato virus A (PVA) were examined on their reactivity with PVA and its denatured capsid protein (PVA-CP) bound to nitrocellulose membrane. Five MAbs reacted with native PVA, three of them also with PVA-CP. MAb 534 gave no reaction in dot-blot tests. In Western blot analysis only MAbs 151, 290, and 328 reacted with PVA-CP. Competition binding test data confirm mutual spatial proximity of epitopes corresponding to these MAbs. Pepscan (SPOTs tests) with overlapping octapeptides representing the sequence of the first 60 amino acids from the N terminus of PVA-CP showed that the epitopes detected by MAb 151, 328, and 634 are located in this region. MAb 534 was deduced to react with discontinuous CP epitope. Results of analogic peptide synthesis for the MAb 151 epitope indicate that two lysine residues are essential for binding of this MAb to its epitope. Our polyclonal antibodies against PVA reacted with six different regions in this part of the CP.