Biochemical and Immunological Characterization of Murine Leukemia Viruses that Are Paralysis‐inducing in Rats

The molecular size and pi of the viral structural proteins of four PVC viruses (PVC111, PVC211, PVC321 and PVC441) were compared by single or two‐dimensional polyacrylamide gel electrophoresis. PVC111 had slightly larger plSE and gPr85 molecules (about 0.5 kilodalton) than did the other PVC viruses. On the other hand, the virion structural proteins p30, p15, p12E and p12 from all the viruses had the same molecular sizes and pis. The gp70s and plOs from all the viruses showed the same molecular sizes. A monoclonal antibody to gp70 of PVC321 virus recognized the gp70s of all PVC viruses, but not the gp70s of four clones of the wild mouse ecotropic viruses, Friend murine leukemia viruses (F‐MuLV), AKR ecotropic MuLV, dual‐tropic F‐MuLV or NZB endogenous xenotropic MuLV, revealing that these four PVC viruses are homologous with each other, but distinct from the known mouse retrovirnses.