Specific inhibition of XC syncytia formation by anti-MuLV gp69/71 antibodies.

The XC syncytia formation observed when ecotropic murine leukemia virus producer cells were cocultivated with XC cells was specifically inhibited by anti-MuLV gp69/71 antibodies with type- or group-specific activities. Thus, the major glycoprotein of budding viruses was probably responsible for the fusion with XC cells. Since this inhibition is specific for anti-gp69/71, it provides a simple, sensitive and convenient way to type ecotropic type C viruses and to detect anti-gp69/71. The micromethod we have developed has been applied to the detection of type-specific anti-GLV gp69/71 natural antibodies in the serum of normal mice.