Immunochemical studies of foot-and-mouth disease: II. Characterization of RNA-free viruslike particles

A new antigen of foot-and-mouth disease virus (FMDV) is described. It has a sedimentation rate of 75 S, and a density of 1.31 g/ml. It is noninfectious and appears to be devoid of RNA. It has an estimated diameter of 21 mμ. It fixes complement when used as an antigen in the complement-fixation test and forms a precipitin line with homotypic serum in agar plates. It differs from the 140 S FMDV antigen in that: (a) it cannot be disrupted to the 12 S subunit at pH 6.0; and (b) it appears to react with specific antibody to the 12 S subunit as well as with specific antibody to the 140 S intact virus. It occurs as approximately 85% of the total complement-fixing activity of one of the four foot-and-mouth disease viruses studied.