Expression of the 1.8-kb cDNA allows NRK 52E to become susceptible to infection by a feline leukemia virus-C (FeLV-C) pseudotype LAPSN vector.

The NRK 52E cells in panel a contain the control vector MSCVneo, cannot be infected by the FeLV-C pseudotype LAPSN vector, thus fail to express human alkaline phosphatase, and are white. The NRK 52E cells in panel b contain MSCV (1.8 kb)neo, express FeLV-C cell surface receptor, and are readily infectable by the FeLV-C pseudotype LAPSN vector, as evidenced by their purple stain. Cells infected with the amphotropic pseudotype LAPSN vector stain purple (panels c and d). NRK-52E cells not exposed to virus do not express human alkaline phosphatase and are white (data not shown). The concentration of the FeLV-C pseudotype vector was 10 × that of the amphotropic murine leukemia virus pseudotype vector in this study. Formal titers are shown in Table 1.