Monoclonal antibody detects a common surface antigen on two independently established murine Moloney sarcoma virus non-producer transformants

Monoclonal antibodies were raised against a cell surface glycoprotein (46K antigen) expressed by a Moloney sarcoma virus (Mo-MSV)-transformed STU mouse cell line (Sac). Although non-productively transformed Sac cells expressed the 46K antigen at their surface, transplantation of Sac non-producer cells into immunocompetent mice failed to induce anti-46K antibody production. Only transplantation of helper virus-superinfected Sac cells led to the development of anti-46K antibodies in addition to antibodies against helper virus structural antigens. Hybridomas producing anti-46K antibodies were established by fusion of mouse myeloma cells with spleen cells taken from mice bearing Sac tumour cells infected with Moloney helper virus. The monoclonal antibodies were subsequently tested against STU mouse transformants [spontaneously transformed or experimentally transformed with the progressor strain of Mo-MSV and the chemical carcinogen 3-methylcholanthrene (MCA), respectively] and BALB/c mouse transformants [transformed with Mo-MSV, simian virus 40 (SV40) or MCA]. Only one of the transformed cell lines tested, a non-producer transformant (PV-TC-77) induced with the progressor strain of Mo-MSV in an STU mouse was found to express a 46K antigen on the cell surface. The 46K surface antigen expressed by PV-TC-77 cells exhibited the same serological, biochemical and biological properties as the 46K Sac cell surface antigen. Though detectable on the surface of PV-TC-77 non-producer cells, immunocompetent syngeneic recipients of non-producer PV-TC-77 cells remained unresponsive against their 46K surface antigen. Only transplantation of helper virus-infected PV-TC-77 producer cells led to antibody development against the 46K surface antigen.