The antigenic expression of murine leukemia virus GP₇₁ on murine and heterologous species cells

RNA C type viruses are oncogenic agents in many animal species and in particular are associated with all types of murine leukemia. The expression of the major glycoprotein, gp71, of murine leukemia virus, in which virus neutralizing and type specific determinants reside, was studied on the surface of a variety of mouse cell lines with a monospecific rabbit antiserum raised against purified Friend gp71. Using live cell membrane immunofluorescence, most primary and established murine fibroblast cell lines tested, except those of BALB/c origin, were found to bind significant amounts of anti gp71 antiserum. Thymocytes from C57BL/6J (G(IX)^-) and 129/J (G(IX)⁺) mouse strains were also positive for gp71, as were thymocytes from BALB/c. Adsorptions revealed that normal nonproducer murine cells displayed group and interspecies determinants, as did virus producing cells, and that the antiserum was predominantly type specific for Friend, Moloney, and Rauscher cells. Immunoferritin electron microscopy localized the antigenic determinants on both the virus and cell membrane. The distribution and nature of cell surface expression of gp71 may be helpful in designing gp71 immunization or serum therapy protocols for protection against murine leukemia.