The effect of heat on the structure of foot-and-mouth disease virus and the viral ribonucleic acid

Abstract

The infective 25-mμ component of foot-and-mouth disease virus loses infectivity at 37° at the rate of 90 % in 8 h. By the use of 32P-labelled virus it has been shown that virus heated at 37° for 24 h sediments in sucrose gradients at the same rate as unheated virus. Its buoyant density in caesium chloride is also unaltered. These findings, together with the observation that the immunogenic properties of the virus are unimpaired by heating at 37°, suggest that the structure of the virus is not grossly altered by the heat treatment. The RNA extracted from heated virus with phenol shows a corresponding loss of infectivity. Whereas the RNA from unheated virus sediments as a single peak in a sucrose gradient, the sedimentation pattern of the RNA from heated virus suggests that it consists of a wide range of smaller molecules.