Ultracentrifugal studies of the infective and complement-fixing components in the virus system of foot-and-mouth disease

Abstract

The sedimentation constant of the infective particle in foot-and-mouth disease has been determined by modifications of the methods of Elford (1936) and Polsen (1941). A new high-speed, swinging-cup rotor was employed. A sedimentation constant of 70 Svedberg units was obtained for the infective particle in a variety of starting materials derived from guineapigs, mice and cattle. The validity of the data is discussed in relation to the accuracy with which a sedimentation constant may be determined by these methods. Ultracentrifugal studies employing inclined tubes have demonstrated that in fresh preparations the infective particle is associated with from 0 to 50% of the initial complement-fixing activity. The remaining complement-fixing activity is associated with a component of sedimentation constant 8 Svedberg units. This slower sedimenting component, if infective, contributes less than 0⋅01% of the initial infectivity. A direct and relatively precise method is described for the determination of the partition of a biological activity between two or more components of a virus system. By the use of radial and inclined tubes in non-optical procedures a correlation between these methods has been established. It is shown that the sedimentation constant of a biologically active component may be estimated by procedures based on sampling in inclined tubes. The G integral is introduced as an accurate and convenient parameter which greatly facilitates the calculation and presentation of the results of ultracentrifugal studies.

Biophysical Studies of the Virus System of Vesicular Stomatitis

“…Serial twofold dilutions of the experimental sample were tested with excess of the specific antisera. In view of the observed greater lability of the antigenic material in vesicular stomatitis the accuracy of determination of complement-fixing activity in this work is about f 15 yo and is inferior to that observed in previous studies of the virus system of foot-and-mouth disease (Bradish et al 1952).…”

“…The extension of studies of this type to the virus system of vesicular stomatitis presents advantages because of the greater mass of the infective particle which, on the basis of earlier ultrafiltration and ultracentrifugation data (Galloway & Elford, 1933; Elford & Galloway, 1937) has an equivalent diameter of about 75 mp. This larger particle facilitates the use of certain biophysical methods which were not employed in the previous study (Bradish et al 1952). Of particular value is the comparison which may be made between the data obtained by the biological assay of ultracentrifugal fractions and those derived by direct optical-analytical ultracentrifugation and by electron microscopy.…”

“…The methods employed were generally as described by Bradish et al (1952). The Model E and Model L Spinco Ultracentrifuges (manufactured by the Specialised Instrument Corporation, Belmont, California, U.S.A.) were used with a range of angle rotors designed to accommodate capped Lusteroid tubes of capacity from 8 ml.…”

“…It was shown in the previous paper (Bradish et al 1952) that the process of centrifugation in radial C . J .…”

“…In addition to the angle rotors described above a special swinging-cup rotor was employed (Bradish et al 1952) in conjunction with a range of fittings designed to allow samples of from 2-5 to 0.05 ml. to be centrifuged in strictly radial tubes.…”