Different sensitivities of rat cells to infection by ecotropic murine leukemia viruses

The titration curves of ecotropic murine leukemia viruses with various rat cells were determined by the reverse XC assay method. The curves of N-, B-, and NB-tropic viruses with Hepano cells (derived from a Sprague-Dawley rat) and Sprague-Dawley embryo cells were of single-hit type. In contrast, the curves of these viruses with 3Y1 cells (derived from a Fischer rat) and Fischer rat embryo cells were of two-hit type. Thus, the cells derived from the Sprague-Dawley rat were sensitive to infection by ecotropic murine leukemia viruses but the cells derived from the Fischer rat were resistant.