Antibodies raised in a natural host and monoclonal antibodies recognize similar antigenic features of foot-and-mouth disease virus.

Swine polyclonal antibodies directed against a major antigenic site (site A) of foot-and-mouth disease virus (FMDV) of serotype C, and monoclonal antibodies (MAbs) which recognize different epitopes within this site, have been compared with regard to reactivity with a panel of synthetic peptides. The peptides used represent different segments or variant sequences of site A, and their reactivities reflect differences in antigenic specificity. The results indicate a remarkable immunochemical similarity between the site A epitopes defined by murine MAbs and those recognized by antibodies elicited in a natural host of FMDV. This similarity further validates previous conclusions, based on analyses with MAbs, on the relevance of amino acid substitutions at a few critical positions on the intratypic antigenic variation of FMDV in the field. They also give further support to a dual function of the Arg-Gly-Asp motif of the G-H loop in cell attachment and in the recognition by host antibodies, as recently documented with the elucidation of the three-dimensional structure of an antigen-antibody complex of FMDV. In addition, the results encourage the use of extended panels of well-characterized MAbs for a precise molecular analysis of the antigenic variation of FMDV, and of other viruses, in the field.