Reactivity with Monoclonal Antibodies of Viruses from an Episode of Foot-and-mouth Disease

A panel of 12 monoclonal antibodies (MAbs) raised against foot-and-mouth disease virus (FMDV) of serotype C1 (FMDV C-S8c1) and 11 MAbs raised against other FMDVs have been used to evaluate the reactivity of 14 isolates of FMDV of serotype C1 (series FMDV C-S), 12 of them from one disease episode (Spain 1979-1982). The assays used were immunoelectrotransfer blot, immunodot and neutralization of infectivity. None of the isolates could be clearly distinguished by its reactivity with 6 non-neutralizing and 2 neutralizing MAbs raised against FMDV C-S8c1. In contrast, the isolates were distinguished in two groups by a 10(2)-fold difference in their reactivity with 6 neutralizing MAbs. The reactivity of MAbs with synthetic peptides indicated that conserved and non-conserved epitopes recognised respectively by neutralizing MAbs 4G3 and SD6 are localized in the immunogenic region (amino acids 138-156) of VP1. Thus, epidemiologically related FMDVs differ in at least one epitope critical for virus neutralization.