Virolysis of mouse mammary tumor virus by sera from breast cancer patients.

All type C retroviruses are lysed by human serum in apparently antibody-independent, complement-mediated reactions. In contrast, we have now determined that the mouse mammary tumor virus (MMTV), a type B retrovirus, is not disrupted by normal human serum. MMTV was lysed, however, when rabbit antibody to whole MMTV was added to the serum. By taking advantage of this dependence of MMTV lysis on specific antibody, a virolytic assay was developed, based on the measurement of reverse transcriptase released from disrupted virions, to search for evidence of antibodies to MMTV in human sera. Significantly greater virolytic activity was detected in the sera of patients with breast cancer than in sera of patients with benign disease (P less than 0.001) or colorectal cancer (P less than 0.001) or in sera from apparently healthy individuals (P less than 0.002). This assay thus appears to be able to detect a unique attribute, possibly the presence of an antibody crossreacting with MMTV, in serum in patient with breast cancer.