ABSTRACT
Early studies with foot-and-mouth disease virus (FMDV) showed that an important antigenic site on the particle, subsequently termed antigenic site 1, is highly sensitive to proteolytic enzymes. Only VP1 is cleaved, showing that the site is present on this protein. Finally, a combination of approaches led to the location of the site within VP1. The sequence of the site is variable both in length and composition, as might be expected for an important antigenic determinant and synthetic versions of this sequence were found to elicit reasonable levels of neutralising and protective antibodies in laboratory animals, encouraging attempts to develop synthetic vaccines. Unfortunately, for reasons that are not clear, the synthetic vaccines did not perform as well in target species.
Resolution of the crystal structure of FMDV showed that antigenic site 1 lies within a highly mobile loop, the G-H loop, at the surface of the virus particle and this characteristic probably accounts for its efficacy as a synthetic immunogen. In addition, the G-H loop has been shown to be the receptor binding feature of the virus. It includes a highly conserved triplet, arginine-glycine-aspartic acid, which is key to the recognition of integrin receptors on the surface of susceptible cells.
