MUTATIONAL ANALYSIS OF DISCONTINUOUS EPITOPES OF FOOT-AND-MOUTH-DISEASE VIRUS USING AN UNPROCESSED CAPSID PROTOMER PRECURSOR

An unprocessed capsid precursor (P1) of foot-and-mouth disease virus ( FMDV) has been expressed in mammalian cells to study discontinuous epi topes involved in viral neutralization. Amino acid replacements found in virus-escape mutants were engineered in the P1 precursor by site-di rected mutagenesis of the plasmid. In all cases the replacements aboli shed recognition of unprocessed P1 by the relevant monoclonal antibodi es (MAbs), paralleling the effects of the corresponding substitutions in neutralization of infectious FMDV. Five capsid surface residues wit hin the same discontinuous antigenic area that were never found replac ed in escape mutants were also engineered in P1. None of the substitut ions affected antibody recognition, suggesting that these residues wer e not directly involved in the interaction with the antibodies tested. The results validate site-directed mutagenesis of constructs encoding capsid precursors as an approach to probe the structure of viral disc ontinuous epitopes not amenable to analysis with synthetic peptides. ( C) 1998 Elsevier Science B.V. All rights reserved.