The occurrence of SV40‐neutralizing antibodies in sera of patients with genitourinary carcinoma

Neutralizing antibodies to simian virus 40 (SV40) were detected in sera of seven of 182 patients studied at the Roswell Park Memorial Institute. Four of 91 (4.4%) bladder tumor patients, two of 24 (8.3%) patients with prostatic carcinoma, and one of four patients with testicular tumors had antibodies. Neutralizing antibodies were demonstrable in repeated bleedings over a 5–11 month period. T antibodies were not detected in any of the sera. None of the antibody‐positive patients gave a history of immunization with (potentially SV40‐contaminated) poliovirus vaccines, the only known source of major human exposure to SV40 in the United States. These findings suggest that the seven antibody‐positive donors were infected with a virus cross‐reacting with SV40 or that infection with SV40 may have occurred in some unknown manner.