Physicochemical, biological and serological properties of a leukemogenic virus isolated from cultured radl-V-induced lymphomas of C57BL/Ka mice

Abstract

RadLV/VL 3, a virus spontaneously and continuously produced at high titer by BL/VL 3 cells, a line established in culture from a RadLV-induced C57BL/Ka mouse thymic lymphoma, has been extensively characterized. Evidence is presented indicating that it is a C-type RNA virus with highly thymotropic and leukemogenic biologic properties identical with those of its RadLV parent. It was not significantly neutralized by antibodies prepared against other ecotropic or xenotropic murine C-type viruses, used individually or in combination, whereas these antibodies effectively neutralized MCF-247 virus. However, antisera prepared against RadLV/VL 3 in rabbits and mice readily neutralized RadLV/VL 3. Curiously, the rabbit antiserum also had strong neutralizing activity against three other C-type endogenous viruses of the C57BL/Ka strain, BL/Ka(B), BL/Ka(N), and BL/Ka(X), all of which are fibrotropic (replicate readily in fibroblasts of appropriate tropism) and lack thymotropic and leukemogenic activity. In interference assays, these viruses and RadLV/VL 3 exhibited little or no capacity for mutual or self-interference, nor did RadLV/VL 3 interfere with the replication of MCF-247 virus in mink cells. However, the addition to cultures of increasing concentrations of the purified envelope glycoprotein (gp71) of RadLV/VL 3, though devoid of effect on BL/Ka(B) and BL/Ka(N), strongly inhibited the replication of RadLV and RadLV/VL 3 both in vitro and in vivo, and partially inhibited the xenotropic replication of BL/Ka(X). Competition radioimmunoassays with purified virion polypeptides demonstrated that the gp71 of RadLV/VL 3 is distinctively different from that of all other viruses tested; that the p12's of RadLV/VL 3 and BL/Ka(B) are similar or identical, whereas that of BL/Ka(N) competes in the AKR-MuLV p12 assay; and that the p30's of all of the viruses studied are indistinguishable by this method. Finally, RadLV/VL 3 failed to elicit cytopathic changes or transformed cell foci after serial passage in mink lung cells, even after co-infection with the xenotropic BL/Ka(X) virus, indicating that it is apparently devoid of MCF activity. Thus, MCF activity is apparently not a prerequisite for thymotropic and leukemogenic activity, at least in the C57BL/Ka strain.