Short Communication Serum Antibodies to JC Virus, BK Virus, Simian Virus 40, and the Risk of Incident Adult Astrocytic Brain Tumors

Genomic sequences of the human polyomaviruses, JC virus (JCV) and BK virus (BKV), and simian virus 40 (SV40) have been reported from several types of human brain tumors, but there have been no population-based seroepidemiologic studies to evaluate the association between polyomavirus infection and brain tumors. We conducted a case-control study, nested within a prospective cohort, to investigate the association between antibodies to JCV, BKV, and SV40, as measured in serum collected 1–22 years before diagnosis and incident primary malignant brain tumors. Brain tumor cases (n 44) and age-, gender-, and race-matched controls (n 88) were identified from participants of two specimen banks in Washington County, Maryland. IgG antibodies to the capsid proteins of JCV and BKV were assessed using ELISAs. SV40-neutralizing antibodies were measured using plaque neutralization assays. Similar to the general population, the prevalence of JCV and BKV infection was high in our study population (77 and 85%, respectively). Antibodies to SV40 were less prevalent (11%). The odds ratio for subsequent brain tumor development was 1.46 [95% confidence interval (CI), 0.61–3.5] for JCV, 0.66 for BKV (95% CI, 0.22–1.95), and 1.00 for SV40 (95% CI, 0.30–3.32). Given the high prevalence of JCV and BKV infections and the millions who were potentially exposed to SV40 through contaminated polio vaccines, future studies should attempt to replicate these findings. Introduction The polyomavirus family includes two human viruses, JCV and BKV. SV40 is a natural polyomavirus infection of the rhesus macaque that was introduced into the human population through contaminated polio vaccine in the late 1950s (1). The three polyomaviruses are structurally and genetically similar (2). JCV and BKV are ubiquitous viruses found in human populations throughout the world, with estimates of seroprevalence in United States adults of 75 and 100%, respectively (3). Initial infections with JCV and BKV are largely asymptomatic and occur predominately in childhood, after which the viruses persist in kidney and B lymphocytes (2). Reactivation of latent JCV and BKV infections in immunocompromised individuals causes diseases, such as progressive multifocal leukoencephalopathy in AIDS patients (JCV) and nephropathy in renal transplant recipients (BKV; Ref. 2). SV40, discovered in the early 1960s, was an accidental contaminant of licensed inactivated polio vaccines manufactured between 1955 and 1961 (1). The prevalence of SV40 infection in the general population resulting from vaccination with contaminated lots is unknown. Serum antibodies to SV40 have been detected in study populations with prevalences ranging from 4 to 14% (4–7). There have been no population-based seroepidemiologic prevalence studies of SV40 antibodies. Brain tumors, including medulloblastomas, glioblastomas, astrocytomas and ependymomas, and neuroblastomas, have been induced with inoculated polyomaviruses in several animal species (8). The “tumor antigen” (T antigen), a nonstructural protein expressed by the viruses, is responsible for cell transformation in animal models. The T antigen complexes with and subsequently inactivates the tumor suppressor proteins p53 and pRb (8). Genomic sequences from all three viruses have been reported from human brain tumor tissue of different types: (a) SV40 in choroid plexus tumors (9–12) and ependymomas (9–13); (b) JCV in medulloblastomas (14); (c) BKV (11, 15– 17) and SV40 (11, 18) in meningiomas; (d) JCV (19), BKV (10, 11, 15), and SV40 (10–12, 20) in glioblastomas; and (e) JCV (19, 21), BKV (11, 15), and SV40 (11, 12, 18) in astrocytomas. No statistically significant associations have been observed between SV40 exposure from potentially contaminated polio vaccines and brain tumors in seven cohort studies conducted since 1963 (reviewed in Refs. 22 and 23). These studies did not incorporate direct measurements of SV40 infection in individuals. No observational studies have investigated the possible associations between either JCV or BKV and brain tumors. We conducted a population-based, nested case-control study, comparing the presence of polyomavirus antibodies in Received 6/19/02; revised 1/10/03; accepted 1/31/03. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported by the Training Center for Public Health Research, Johns Hopkins Bloomberg School of Public Health (JHBSPH), the Institutional Research Cancer Epidemiology Fellowship (to D. E. M. R.), 2 T32 CA093-14-19 [National Cancer Institute (NCI)], and the Early Detection Research Network, 5U01 CA86308-04 [NCI]. A. J. A. is a recipient of a KO7 award from the NCI (CA73790). 2 To whom requests for reprints should be addressed, at Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Suite 6030, Baltimore, MD 21205. 3 The abbreviations used are: JCV, JC virus; BKV, BK virus; SV40, simian virus 40; ICD, International Classification of Diseases; CI, confidence interval; OR, odds ratio. 460 Vol. 12, 460–463, May 2003 Cancer Epidemiology, Biomarkers & Prevention Research. on September 20, 2017. © 2003 American Association for Cancer cebp.aacrjournals.org Downloaded from serum collected years before diagnosis between incident cases of primary brain tumors and cancer-free controls. Materials and Methods Study Population. Two research serum banks were established in Washington County, Maryland, CLUE I in 1974 and CLUE II in 1989, so named from the campaign slogan, “Give us a clue to cancer and heart disease.” All participants gave informed consent at the time of blood donation and completed a brief questionnaire to obtain information on race, sex, age, cigarette smoking, and education. Samples from serum (20,305) and plasma (25,081) were obtained from Washington County residents in CLUE I and II, respectively. A total of 8,394 people participated in both CLUE I and II. Cases were defined as adults diagnosed with primary malignant tumors of the brain (ICD-9 191) or meninges (ICD-9 192) with no previous history of cancer, except possibly for nonmelanoma skin cancer and cervical cancer in situ. Cases diagnosed through December 31, 2000 were identified using the Washington County Cancer Registry and, since 1992, the Maryland Cancer Registry. The ratio of observed to expected number of cases, based on Surveillance, Epidemiology, and End Results incidence rates (24), was 0.94. Of the 46 cases of primary brain tumors identified, 2 of those coded as ICD-9 192 (a spinal cord tumor and benign meningioma) were excluded, leaving 44 cases in the study. Brain tumor diagnosis was confirmed by pathology reports for 36 of the cases. Analyses conducted with and without the histologically confirmed cases yielded similar results; thus all are included. Two controls were individually matched to each case on cohort participation, age within 2 years, race, gender, date of blood draw within 45 days, and freezer/thaw history of the serum sample. Controls were cancer free up to the time of cases’ diagnosis, with the possible exceptions of nonmelanoma skin cancer and cervical cancer in situ. Laboratory Assays. Serum samples were frozen and stored at 70°C, until thawed for the study. The presence of IgG antibodies to the capsid proteins of JCV and BKV was tested with an ELISA using virion particles as antigen, as described previously (25). Plaque neutralization assays were performed for SV40 antibodies, as described previously (26). Titers of 640 were considered positive for antibodies to JCV and BKV using ELISA (25). Plaque neutralization assays were performed at 1:10 and 1:40 dilutions in serum. Specimens that tested negative ( 50% plaque reduction) at both dilutions were scored negative, those that tested positive at both dilutions were scored positive, and those specimens that tested positive at 1:10 dilution and negative at 1:40 dilution were called “weak positive.” Plaque inhibition data were unavailable for one control who was classified as negative in the analysis. Laboratory personnel were masked to case-control status. Sera from monkeys shown previously to be positive for SV40 antibodies served as positive controls for the plaque neutralization assays. Positive controls for ELISA were derived from individuals known to be infected with JCV or BKV, whereas negative controls were derived from pediatric patients 3 years old. All ELISA positive controls tested positive, and negative controls tested negative. Pairs of duplicate specimens were tested blindly to assess the reliability of the ELISA assay. The percentage of agreement among duplicate pairs, within one dilution, was 93% for JCV and 87% for BKV. No correlation was observed between JCV and BKV antibody titers, indicating little cross-reactivity between antibodies to these two viruses in the ELISA assays. Statistical Methods. To assess the association between polyomavirus antibodies and brain tumors, matched ORs and 95% CIs were estimated using conditional logistic regression. To investigate dose-response relationships, JCVand BKV-positive titers were further divided into two categories (640 or 2,560 and 10,240), and SV40 plaque neutralization results were considered as three categories: (a) negative; (b) weak positive; and (c) positive. JCV and BKV data were stratified by cohort participation, and no differences in ORs were observed. For the subset of individuals who donated blood in both 1974 (CLUE I) and 1989 (CLUE II), the results of assays performed on the 1989 specimens were used in subsequent analyses. Stratification was used to explore potential differences in the association between antibodies to JCV and BKV and brain tumors by tumor type, age at diagnosis, and time from blood draw to diagnosis. All analyses were conducted using SAS, version 8 (SAS Institute, Inc., Cary, NC).