Leukemia serum reactive with retrovirus-related antigen in normal human placenta

Serum antibody reactive with a retrovirus-related p30 antigen in human normal term placenta was investigated and characterized by immunohistologic and immunoblotting methods. Sera obtained from patients with acute leukemia and malignant lymphoma were used as first antibody, and cryostat sections of placenta were the target antigen. An IgM antibody that reacted mainly with the basal aspect of syncytiotrophoblast of chorionic villi, where a putative human endogenous retrovirus p30 antigen is located, was directed by indirect immunofluorescence. This antibody activity, termed anti-basal aspect of syncytiotrophoblast (anti-BAST), was detected in the sera of many patients with acute leukemia (AML, ALL) and malignant lymphoma, and less frequently in sera of pregnant women and normal controls. As shown by immunoblotting analysis, the main reactive antigen recognized by anti-BAST was a non-glycosylated 32-kDa placental protein which was antigenically related to SSAV p30. A non-glycosylated 19-kDa protein was also considered to be one of the anti-BAST-corresponding antigens. This suggests the presence of a new antigen-antibody system of human retrovirus(es) revealed by subinfectious antigenic expression and by specific antibody activity in conditions of human health and disease, particularly, acute leukemias and malignant lymphomas of common types.