[Experiments to purify and concentrate the foot-and-mouth disease virus]

Experiments were carried out for the purification and concentration of the foot-and-mouth disease virus. For the purpose the virus suspensions were treated with chloroform and 8 per cent polyethylene glycol. The precipitated virus was eluated with phosphate buffer (of pH 7.6) up to 1:100 of the initial volume. The concentrated virus was subjected to gradient ultracentrifugation on gradient of CsCl. The fractions obtained were investigated through radial immunodiffusion reaction with early sera, containing IgM antibodies. The fractions that formed circles of precipitation were studied under electron microscope at negative contrasting. It was found that the fractions taken from between the CsCl layer of 1.42 g/cm3 density and the underlying CsCl layer of 1.50 g/cm3 density, which produced precipitation circles in the radial immunodiffusion test, contained purified virions of intact structure in concentration of 10(9).