Effect of trypsin and chymotrypsin on the polypeptides of large and small plaque variants of foot-and-mouth disease virus: relationship to specific antigenicity and infectivity.

Large and small plaque variants of A12 foot-and-mouth disease virus were shown to have specific antigenic determinants. Large plaque virus antigenic specificity was destroyed by trypsin treatment, but the small plaque antigen was resistant despite cleavage of the trypsin-sensitive polypeptide. The cleavage of polypeptide VP3 by trypsin resulted in the formation of a new antigen not present on untreated virus. The effects of chymotrypsin and trypsin on the polypeptides of the plaque variants have been examined and related to changes in antigenicity, infectivity, and exposure of the polypeptides at the surface of the capsid. The results are discussed in relation to the orientation of the trypsin-sensitive polypeptide in the virus capsid.