Production of monoclonal antibodies reactive with a denatured form of the Friend murine leukemia virus gp70 envelope protein: use in a focal infectivity assay, immunohistochemical studies, electron microscopy and western blotting.

Four monoclonal antibodies were selected for their ability to recognize the envelope protein of Friend murine leukemia virus (F-MuLV) in methanol-fixed tissue culture cells. Each of these monoclonal antibodies was found to react only with F-MuLV. By using recombinant retroviruses, it was determined that each of the monoclonal antibodies recognized the C-terminal one-third of the F-MuLV gp70 envelope protein. The monoclonal antibodies were effective in radioimmunoprecipitation of F-MuLV proteins, and one of the antibodies, 720, was also effective in Western blotting. The ability of antibody 720 to react with F-MuLV in methanol-fixed cells facilitated the use of a sensitive immunoperoxidase method with a focal virus infectivity assay. In immunohistochemical studies using light microscopy, antibody 720 could specifically label F-MuLV-infected cells in acetone-fixed tissue sections from F-MuLV-infected animals. Finally, in immuno-gold labelling studies using electron microscopy, antibody 720 could be used to distinguish F-MuLV from amphotropic MuLV.