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SUMMARY: The infective component of the virus system of foot-and-mouth disease was concentrated and purified by ultracentrifugation and solvent extraction. Infective materials derived from ox, guinea-pig, mouse, chicken, goose and tissue culture were employed. The infective concentrates (D-fractions) and the separated smaller complement-fixing components (U-fractions) were characterized by infectivity, complement-fixing activity and nitrogen content. The D-fractions, of activity up to 1014·5 ID50/g. N, represented less than 0·1% of the initial protein content. Electron micrographs of the D-fractions showed clusters and hexagonal arrays of 25 to 27 mμ ‘spherical’ particles of granular structure. These defined fractions of the virus system were used in a number of subsequent investigations.
Bradish et al. (1960) studied this question.