An improved murine leukemia virus immunofluorescence assay

The use of DEAE-dextran and polybrene during infection of mouse embryo fibroblast cell lines of Fv-1 bb origin with the radiation leukemia virus strikingly increased the proportion of cells in which virus-induced cytoplasmic antigens were detectable by indirect immunofluorescence and significantly accelerated the time course of their detection, thus making possible the development of a rapid, sensitive, and practical new assay based upon the percentage of immunofluorescence-positive cells. Direct comparisons with several other in vitro assays are presented. The assay was also tested successfully with Gross leukemia virus grown on cells of Fv-1 nn origin, and should be applicable to other murine leukemia viruses and, perhaps with minor modifications, to other mammalian leukemia viruses as well.