High prevalence of circulating antibodies to MuLV p30 antigen in human sera. An autoimmune response?

To study the possible involvement of a murine leukemia virus (MuLV) related agent in human cancer, an extensive immunoblotting analysis of human sera (cancer, autoimmune as well as control normal ones) for the presence of antibodies to MuLV structural proteins was performed. Out of 350 sera, 89 reacted with gag precursor Pr65, 72 reacted with major viral core protein p30 and five with the matrix protein p15. Antibody reactivity to the env-encoded glycoprotein gp70 was detected in 7 cases out of 16 sera tested. There were no significant differences between pathological and normal sera concerning the patterns and the frequency of the reactivity. Sera from patients with various malignancies (mainly with breast cancer) generally displayed more intensive signals to MuLV p30 than normal sera. Epitope mapping revealed that MuLV p30-reactive antibodies recognize an antigenic determinant(s) located at the carboxyterminus of the protein.