Characterization of an amphotropic murine C-type virus that is NB-tropic.

Abstract

Abstract Cocultivation of SIPC-2 myeloma cells with clone A 31 , BALB/3T3 cells results in the continuous production of a C-type virus by the A 31 cells that has been designated S/A-1. S/A-1 virus possessed the essential properties of a murine retrovirus, including a buoyant density of 1.16 g/cm 3 , C-type morphology, high molecular weight (70 S) RNA, and an RNA-dependent DNA polymerase. After cloning by three endpoint dilution passages in A 31 , and SIRC cells, the virus was shown to possess ecotropic as well as xenotropic activity. For example, the S/A-1 virus producibility infected mouse cells, including BALB/3T3, NIH/3T3, SC-1, 3T3 FL, and F 1 cells as well as non-mouse cells, including normal rat kidney, rabbit corneal (SIRC), Chinese hamster peritoneal, mink lung, Pekin duck embryo, human rhabdomyosarcoma, and guinea pig embryo cells. The S/A-1 virus infected A 31 , cells do not induce XC-syncytia and the virus does not induce foci in mink lung cells. Thus, the data suggest that it is an amphotropic virus whose ecotropism is different (i.e., NB-tropic) from the previously reported amphotropic viruses (i.e., N-tropic). In addition, S/A-1 virus is different from the mink cell focus-inducing (MCF) viruses (J. W. Hartley, N. K. Wolford, L. J. Old, and W. P. Rowe 1977, Proc. Nat. Acad. Sci. USA 74 , 789–792) in terms of its lack of focus-inducing activity on mink lung cells, B-tropism, and ability to replicate in human rhabdomyosarcoma and F 1 mouse cells. The structural proteins of cloned S/A-1 virus were compared to those of 1504-A virus, a previously described amphotropic virus isolated from feral mice (J. W. Hartley and W. P. Rowe 1976, J. Virol. 19 19–26; S. Rasheed, M. B. Gardner, and E. Chan 1976, J. Virol. 19 , 13–18), by electrophoresis on a linear 7–20% acrylamide slab gel and staining with Coomassie blue. S/A-1 differed from 1504-A in terms of (a) the mobility of a protein with a molecular weight of approximately 12,000 daltons (pl5) and (b) the fact that it has a “double” p30.