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Analysis of the Epitope Structure of Plum pox virus Coat Protein

First author: Equipe de Virologie, UMR 1332 de Biologie du Fruit et Pathologie, INRA, Université de Bordeaux, BP81, 33883 Villenave d'Ornon Cedex, France; second and third authors: Centro Nacional de Biotecnología (CNB), CSIC, Campus Universidad Autónoma, 28049 Madrid; fourth author: Istituto di Virologia Vegetale del CNR, Sezione di Bari, Via Amendola 165/A, 70126 Bari, Italy; fifth author: Palacky University in Olomouc, Faculty of Science, Slechtitelu 11, Olomouc 783 71, Czech Republic; and sixth and seventh authors: Centro de Protección Vegetal y Biotecnología. Instituto Valenciano de Investigaciones Agrarias (IVIA), Carretera Moncada-Náquera km 5, 46113 Moncada, Valencia, Spain.

Typing of the particular Plum pox virus (PPV) strain responsible in an outbreak has important practical implications and is frequently performed using strain-specific monoclonal antibodies (MAbs). Analysis in Western blots of the reactivity of 24 MAbs to a 112-amino-acid N-terminal fragment of the PPV coat protein (CP) expressed in Escherichia coli showed that 21 of the 24 MAbs recognized linear or denaturation-insensitive epitopes. A series of eight C-truncated CP fragments allowed the mapping of the epitopes recognized by the MAbs. In all, 14 of them reacted to the N-terminal hypervariable region, defining a minimum of six epitopes, while 7 reacted to the beginning of the core region, defining a minimum of three epitopes. Sequence comparisons allowed the more precise positioning of regions recognized by several MAbs, including those recognized by the 5B-IVIA universal MAb (amino acids 94 to 100) and by the 4DG5 and 4DG11 D serogroup-specific MAbs (amino acids 43 to 64). A similar approach coupled with infectious cDNA clone mutagenesis showed that a V74T mutation in the N-terminus of the CP abolished the binding of the M serogroup-specific AL MAb. Taken together, these results provide a detailed positioning of the epitopes recognized by the most widely used PPV detection and typing MAbs.

Additional keyword: Sharka.