Separation of encephalomyocarditis virus from tissue components by means of protamine precipitation and enzymic digestion.

The capacity of protamine sulfate to combine with and precipitate considerable tissue debris from certain virus suspensions without significantly decreasing their infectivity or antigenicity has been reported (Warren, Weil, Russ, and Jeffries, 1949). In the case of certain viruses it has been found that concentrating the protamine-clarified suspensions in the ultracentrifuge yields sediments which can be further purified by enzymic digestion. Further ultracentrifugation of the digest yields preparations of greater purity, as measured by the ratio of infectivity to nitrogen content. Observation in the electron microscope and the analytical ultracentrifuge indicates that the final product has considerable homogeneity. Encephalomyocarditis virus was chosen for this investigation because of its marked stability, high titer, small particle size, and its resistance to certain proteolytic enzymes. The following is a description of the method employed to obtain highly purified preparations of this particular virus, and also a presentation of certain of the physical and biochemical properties of the particles isolated.