ISOLATION AND SOME CHARACTERISTICS OF A GROUP-SPECIFIC ANTIGEN OF MURINE LEUKEMIA VIRUSES

Gross leukemia virus from infected rats was purified by potassium tartrate density gradient centrifugation as a band at a density of 1.156 g/ml. A group-specific antigen of the murine leukemia viruses (MuLV-gs1), released from intact virus by Tween-ether or sodium dodecyl sulfate (SDS) and detected by rat antisera, was separated from other components by Sephadex G 200 and CM-cellulose chromatography and by isoelectric focusing. The antigen has an estimated molecular weight of 35,000-40,000 and a sedimentation value s20,w of 2.7, and separates by immunoelectrophoresis into 2 immunologically identical components with β- and γ-globulin mobility. It can be resolved into at least 2 molecular species by isoelectric focusing and into 3 by polyacrylamide gel electrophoresis, all of which show immunologic identity. Rabbits immunized with disrupted Gross virus or with MuLV-gs1 (isolated by Sephadex G 200 chromatography) form precipitating antibody to MuLV-gs1, whereas rabbits immunized with intact virus do not. The evidence suggests that MuLV-gs1 is an internal component of the virus and contains 2.5-4% nucleic acid. © 1969.