Identification of a conformational epitope on the VP1 G-H Loop of type Asia1 foot-and-mouth disease virus defined by a protective monoclonal antibody

Although neutralizing antigenic sites of foot-and-mouth disease virus (FMDV) can be defined by selection of monoclonal antibody (MAb) escape mutants, no conformational neutralizing epitope on the major antigenic site located on the G-H loop of type Asia1 FMDV has been precisely mapped. In this study, we generated a potent neutralizing MAb 3E11, which recognized a conformation-dependent epitope and neutralized FMDV Asia1/YS/CHA/05 in vitro. Importantly, a dose of 5.5 NT50 of the MAb 3E11 completely protected suckling mice from a dose of 10 LD50 of homologous virus challenge in vivo. Through a 12-mer random peptide phage display, synthetic peptide analysis and constructing a series of FMDV Asia1/YS/CHA/05 mutants using reverse genetic system, we finely mapped the neutralizing epitope as the 12-amino acid peptide 141SXRGXLXXLXRR152. These results provide additional insights into the virus–MAb interaction at the amino acid level and may help in the development of an epitope-based Asia1 FMDV vaccine.