Development of an in vitro infectivity assay for the C-type bovine leukemia virus

The ability of the bovine C-type leukemia virus to induce syncytia formation in monolayer cell cultures has been used to develop a specific and simple infectivity assay for the virus. Using bovine embryonic spleen cells or human diploid embryonic lung cells as indicator cells, the results of the assay can be evaluated in 4 to 6 or 6 to 8 days, respectively. Pretreatment of the indicator cells with DEAE-dextran greatly increases the sensitivity of the assay. The assay is quantitative and can be applied as a direct method for the identification of bovine C-type leukemia virus-infected animals; it also provides a simple, and sensitive procedure for the detection and titration of virus-neutralizing antibodies.