Isolation of a non-focus-forming agent from strain MC29 avian leukosis virus.

Abstract

Strain MC29 avian leukosis virus induces a broad spectrum of cancers principally of the myeloid hematopoietic system, but it also causes primary tumors of the kidney and liver and, not infrequently, erythroblastosis. An unusual feature for a leukosis virus is the capacity of the strain to produce marked and very rapid morphological alterations of chick embryo cells with formation of foci in the cell monolayers resembling those associated with Rous sarcoma virus infection. This report describes isolation from terminal dilution clones of a component of strain MC29 with properties distinctly different from those of the standard strain. This agent does not produce foci or cause morphological alteration of chick embryo cells typical of MC29 infection. Further, it induces erythroblastosis in the chicken to the exclusion of myeloid hematopoietic tissue response and does not cause cancers of other organs affected by MC29. In other properties, the agent behaves as a leukosis virus in the activation of Rous sarcoma virus non-producer cells, in the interference with Rous sarcoma virus infection of chicken embryo cells, and in ultrastructural and sedimentation properties and RNA component constitution.