Partial characterization of C-type particles in a cell line (WR-9) derived from a rat epidermoid carcinoma of spontaneous origin.

A C-type virus continuously released from a cell line (WR-9) derived from a spontaneous epidermoid carcinoma was purified by means of large-scale tissue culture techniques and high-volume zonal centrifuges. With the use of relatively pure virus concentrates, partial characterization of the virus has been accomplished. Up to 60 liters of spent culture medium from relatively low virus-yielding cultures were processed at a time through the Model K ultracentrifuge in order to obtain quantities of virus sufficient for convenient Tween-ether extraction of the major polypeptide (30,000 daltons). This structural protein having group-specific reactivity was purified and isolated by isoelectric-focusing techniques. A UV absorption peak (A280) was found to be coincident with a major peak of radioacticity at pH 8.6, the isoelectric point (pI) for rat virus gs antigen previously reported by other investigators. Because species-specific (gs-1) and cross-reactive (gs-3) determinants coexist on this protein, fractions containing the group-specific antigen were identified on the basis of the mammalian interspecies determinant (gs-3), using antiserum prepared against Tween-ether-disrupted feline leukemia virus. At the same time, reactivity to the gs-1 determinants in identical fractions was observed in complement fixation and gel diffusion assays, using guinea pig antiserum known to contain principally antibodies to rat gs-1 determinants. Presently, the principal source of rat type C viral gs antigen is rat cell line MSB, which continuously releases a rat leukemia virus pseudotype of murine sarcoma virus. The WR-9 rat virus line may be of use in providing an additional source of C-type particles that are capable of yielding good gs reagents.