Antibodies to BK virus structural and tumor antigens in human sera from normal persons and from patients with various diseases, including neoplasia.

Sera from 1,279 patients with various diseases were examined for the presence of antibodies to BK virus (BKV) capsid antigens. The percentage of positive sera was comparable in all the diseases except rheumatoid arthritis and chronic nephropathies, where a slightly higher prevalence was found. Sera from 952 patients with tumors were examined for the presence of antibodies to BKV tumor and capsid antigens in comparison with a matched control group of 501 blood donors. Sera from 11 tumor patients (1.15%) and from 4 normal controls (0.80%) had antibodies to BKV tumor antigen. No higher prevalence of antibodies to BKV capsid antigens was found in any cancer type except in carcinomas of the urinary bladder, where the percentage of positive sera and of sera with high titers was higher than in other groups. BKV infection is discussed in relation to its possible connection with human non-neoplastic diseases as well as with human tumors and to its activation under conditions of immunosuppressive therapy.