High titers of antibodies to two human polyomaviruses, JCV and BKV, correlate with increased frequency of chromosomal damage in human lymphocytes

High Resolution and Automatable Cytogenetic Biodosimetry Using In Situ Telomere and Centromere Hybridization for the Accurate Detection of DNA Damage: An Overview

In the event of a radiological or nuclear accident, or when physical dosimetry is not available, the scoring of radiation-induced chromosomal aberrations in lymphocytes constitutes an essential tool for the estimation of the absorbed dose of the exposed individual and for effective triage. Cytogenetic biodosimetry employs different cytogenetic assays including the scoring of dicentrics, micronuclei, and translocations as well as analyses of induced premature chromosome condensation to define the frequency of chromosome aberrations. However, inherent challenges using these techniques include the considerable time span from sampling to result, the sensitivity and specificity of the various techniques, and the requirement of highly skilled personnel. Thus, techniques that obviate these challenges are needed. The introduction of telomere and centromere (TC) staining have successfully met these challenges and, in addition, greatly improved the efficiency of cytogenetic biodosimetry through the development of automated approaches, thus reducing the need for specialized personnel. Here, we review the role of the various cytogenetic dosimeters and their recent improvements in the management of populations exposed to genotoxic agents such as ionizing radiation. Finally, we discuss the emerging potentials to exploit these techniques in a wider spectrum of medical and biological applications, e.g., in cancer biology to identify prognostic biomarkers for the optimal triage and treatment of patients.

Co-Detection of EBV and Human Polyomavirus JCPyV in a Case of AIDS-Related Multifocal Primary Central Nervous System Diffuse Large B-Cell Lymphoma

The human neurotropic Polyomavirus JCPyV is the widespread opportunistic causative pathogen of the fatal demyelinating disease progressive multifocal leukoencephalopathy; however, it has also been implicated in the oncogenesis of several types of cancers. It causes brain tumors when intracerebrally inoculated into rodents, and genomic sequences of different strains and expression of the viral protein large T-Antigen have been detected in a wide variety of glial brain tumors and CNS lymphomas. Here, we present a case of an AIDS-related multifocal primary CNS lymphoma in which JCPyV genomic sequences of the three regions of JCPyV and expression of T-Antigen were detected by PCR and immunohistochemistry, respectively. No capsid proteins were detected, ruling out active JCPyV replication. Sequencing of the control region revealed that Mad-4 was the strain of JCPyV present in tumor cells. In addition, expression of viral proteins LMP and EBNA-1 from another ubiquitous oncogenic virus, Epstein-Barr, was also detected in the same lymphocytic neoplastic cells, co-localizing with JCPyV T-Antigen, suggesting a potential collaboration between these two viruses in the process of malignant transformation of B-lymphocytes, which are the site of latency and reactivation for both viruses.

The Role of the JC Virus in Central Nervous System Tumorigenesis

Cancer is the second leading cause of mortality worldwide. The study of DNA tumor-inducing viruses and their oncoproteins as a causative agent in cancer initiation and tumor progression has greatly enhanced our understanding of cancer cell biology. The initiation of oncogenesis is a complex process. Specific gene mutations cause functional changes in the cell that ultimately result in the inability to regulate cell differentiation and proliferation effectively. The human neurotropic Polyomavirus JC (JCV) belongs to the family Polyomaviridae and it is the causative agent of progressive multifocal leukoencephalopathy (PML), which is a fatal neurodegenerative disease in an immunosuppressed state. Sero-epidemiological studies have indicated JCV infection is prevalent in the population (85%) and that initial infection usually occurs during childhood. The JC virus has small circular, double-stranded DNA that includes coding sequences for viral early and late proteins. Persistence of the virus in the brain and other tissues, as well as its potential to transform cells, has made it a subject of study for its role in brain tumor development. Earlier observation of malignant astrocytes and oligodendrocytes in PML, as well as glioblastoma formation in non-human primates inoculated with JCV, led to the hypothesis that JCV plays a role in central nervous system (CNS) tumorigenesis. Some studies have reported the presence of both JC viral DNA and its proteins in several primary brain tumor specimens. The discovery of new Polyomaviruses such as the Merkel cell Polyomavirus, which is associated with Merkel cell carcinomas in humans, ignited our interest in the role of the JC virus in CNS tumors. The current evidence known about JCV and its effects, which are sufficient to produce tumors in animal models, suggest it can be a causative factor in central nervous system tumorigenesis. However, there is no clear association between JCV presence in CNS and its ability to initiate CNS cancer and tumor formation in humans. In this review, we will discuss the correlation between JCV and tumorigenesis of CNS in animal models, and we will give an overview of the current evidence for the JC virus’s role in brain tumor formation.

Human Polyomavirus JCPyV and Its Role in Progressive Multifocal Leukoencephalopathy and Oncogenesis

The human neurotropic virus JCPyV, a member of the Polyomaviridiae family, is the opportunistic infectious agent of Progressive Multifocal Leukoencephalopathy (PML), a fatal disease seen in severe immunosuppressive conditions and, during the last decade, in patients undergoing immunotherapy. JCPyV is a ubiquitous pathogen with up to 85% of the adult population word-wide exhibiting antibodies against it. Early experiments demonstrated that direct inoculation of JCPyV into the brain of different species resulted in the development of brain tumors and other neuroectodermal-derived neoplasias. Later, several reports showed the detection of viral sequences in medulloblastomas and glial tumors, as well as expression of the viral protein T-Antigen. Few oncogenic viruses, however, have caused so much controversy regarding their role in the pathogenesis of brain tumors, but the discovery of new Polyomaviruses that cause Merkel cell carcinomas in humans and brain tumors in racoons, in addition to the role of JCPyV in colon cancer and multiple mechanistic studies have shed much needed light on the role of JCPyV in cancer. The pathways affected by the viral protein T-Antigen include cell cycle regulators, like p53 and pRb, and transcription factors that activate pro-proliferative genes, like c-Myc. In addition, infection with JCPyV causes chromosomal damage and T-Antigen inhibits homologous recombination, and activates anti-apoptotic proteins, such as Survivin. Here we review the different aspects of the biology and physiopathology of JCPyV.

Lymphocytes with multiple chromosomal damages in a large cohort of West Siberia residents: Results of long-term monitoring

Cells with specific multiple chromosome aberrations, defined as rogue cells (RC) have been described in different populations, predominantly those exposed to radiation. The frequency, etiology and related health risks have still not been elucidated due to their low frequency of occurrences and rarely performed studies. This study reports RC frequency using chromosome aberration (CA) assay in peripheral lymphocytes in the group of 3242 subjects, during a 30-year long follow-up study in a general rural and urban population, children environmentally exposed to radon, occupationally exposed population and lung cancer patients from the Kemerovo region (Siberia, Russian Federation). Results show that the highest RC frequency was present in children environmentally exposed to radon and the lowest in the general urban population. Total frequency of CA did not correlate with frequency of RC. Genotoxic analysis of air and water samples excluded anthropogenic pollution as a possible cause of genome damage and RC frequency. In 85% of RCs, double minutes, observed in a large number of human tumors, were present. Results of CA analysis suggested that radon and its decay products (alpha-emitters) were the leading factors causing RC in subjects exposed to high LET radiation. Thus, RC may be a candidate biomarker for exposure to this type of radiation.

Molecular biology, epidemiology, and pathogenesis of progressive multifocal leukoencephalopathy, the JC virus-induced demyelinating disease of the human brain

Progressive multifocal leukoencephalopathy (PML) is a debilitating and frequently fatal central nervous system (CNS) demyelinating disease caused by JC virus (JCV), for which there is currently no effective treatment. Lytic infection of oligodendrocytes in the brain leads to their eventual destruction and progressive demyelination, resulting in multiple foci of lesions in the white matter of the brain. Before the mid-1980s, PML was a relatively rare disease, reported to occur primarily in those with underlying neoplastic conditions affecting immune function and, more rarely, in allograft recipients receiving immunosuppressive drugs. However, with the onset of the AIDS pandemic, the incidence of PML has increased dramatically. Approximately 3 to 5% of HIV-infected individuals will develop PML, which is classified as an AIDS-defining illness. In addition, the recent advent of humanized monoclonal antibody therapy for the treatment of autoimmune inflammatory diseases such as multiple sclerosis (MS) and Crohn's disease has also led to an increased risk of PML as a side effect of immunotherapy. Thus, the study of JCV and the elucidation of the underlying causes of PML are important and active areas of research that may lead to new insights into immune function and host antiviral defense, as well as to potential new therapies.

Review on the relationship between human polyomaviruses-associated tumors and host immune system

The polyomaviruses are small DNA viruses that can establish latency in the human host. The name polyomavirus is derived from the Greek roots poly-, which means "many," and -oma, which means "tumours." These viruses were originally isolated in mouse (mPyV) and in monkey (SV40). In 1971, the first human polyomaviruses BK and JC were isolated and subsequently demonstrated to be ubiquitous in the human population. To date, at least nine members of the Polyomaviridae family have been identified, some of them playing an etiological role in malignancies in immunosuppressed patients. Here, we describe the biology of human polyomaviruses, their nonmalignant and malignant potentials ability, and their relationship with the host immune response.

Alterations of DNA damage repair pathways resulting from JCV infection

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disorder of the CNS caused by infection of glial cells with the polyomavirus, JCV. Here we report that genomic stability and DNA repair are significantly dysregulated by JCV infection of human astrocytes. Metaphase spreads exhibited increased ploidy correlating with duration of infection. Increased micronuclei formation and phospho-Histone2AX expression also indicated DNA damage. Western blot analysis revealed perturbation in expression of some DNA repair proteins including a large elevation of Rad51. Immunohistochemistry on clinical samples of PML showed robust labeling for Rad51 in nuclei of bizarre astrocytes and inclusion body-bearing oligodendrocytes that are characteristic of JCV infection. Finally, in vitro end-joining DNA repair was altered in extracts prepared from JCV-infected human astrocytes. Alterations in DNA repair pathways may be important for the life cycle of JCV and the pathogenesis of PML.

Association of JC virus T-antigen expression with the methylator phenotype in sporadic colorectal cancers

BACKGROUND & AIMS

JC virus (JCV) is a polyomavirus that ubiquitously infects humans and has been implicated in various human cancers. JCV encodes a "transforming" gene, T-antigen (T-Ag), which is believed to mediate the oncogenic potential of the virus. We have previously shown that JCV DNA sequences are usually present in human colorectal cancers (CRCs), and we have provided in vitro evidence that JCV can induce chromosomal instability (CIN) in CRC cells. This study tests the hypothesis that JCV T-Ag expression correlates with one or more forms of genomic or epigenetic instability in sporadic CRCs.

METHODS

We characterized 100 sporadic CRCs for microsatellite instability (MSI) and CIN. PCR amplifications were performed for T-Ag sequences, and immunohistochemical (IHC) staining was performed to detect T-Ag expression. De novo methylation of the promoter regions of nine putative tumor suppressor genes thought to play a role in colorectal carcinogenesis was studied by methylation-specific PCR.

RESULTS

JCV T-Ag DNA sequences were found in 77% of the CRCs and 56% of these cancers (or 43% of the total) expressed T-Ag by IHC. Significant associations were observed between T-Ag expression and CIN in CRCs (P = .017) and between T-Ag expression and promoter methylation of multiple genes (P = .01).

CONCLUSIONS

The association between T-Ag expression and promoter methylation in CRC suggests that this viral oncogene may induce methylator phenotype and that JCV may be involved in CRC through multiple mechanisms of genetic and epigenetic instability.

Glioblastoma multiforme with small cell neuronal-like component: association with human neurotropic JC virus

The human polyomavirus JCV, the etiological agent of progressive multifocal leukoencephalopathy, has been associated with primitive neuroectodermal tumors and various glial-derived tumors, including glioblastoma multiforme (GBM). Here we describe the unique clinical case of a 54-year-old man who presented with headaches, hemiparesis and drowsiness. T1 and T2 magnetic resonance images revealed a large solid tumor with a cystic component located in the right temporal lobe, with extension into the parietal lobe. Histologically, the tumor was composed of two areas, a main area of large neoplastic cells with pleomorphic atypical nuclei and abundant cytoplasm, which by immunohistochemistry was reactive for glial fibrillary acidic protein, mixed with several foci of poorly differentiated tumoral cells with elongated nuclei and scant cytoplasm, negative for GFAP, but robustly immunoreactive for synaptophysin and phosphoneurofilaments. Results from PCR in laser capture microdissected cells from both areas of the tumor revealed the presence of DNA sequences corresponding to the early, late and control regions (CR) of the JCV genome and expression of JCV proteins T-antigen and Agnoprotein in both phenotypes. No evidence for capsid protein was observed, excluding productive viral infection. Sequencing demonstrated the presence of the JCV Mad-1 strain with distinct point mutations in the CR of isolates from both, GBM and small cell architectural areas. The presence of JCV DNA sequences and expression of viral proteins further reinforces the role of the widely spread human neurotropic virus in early transformation and in the development of brain tumors.

Prediagnostic Circulating Antibodies to JC and BK Human Polyomaviruses and Risk of Non-Hodgkin Lymphoma

Viral infections have been associated with increased risk of non-Hodgkin's lymphoma (NHL). We conducted a nested case-control study to investigate the association between prediagnostic serum antibodies to the human polyomaviruses, JC (JCV) and BK (BKV), and subsequent risk of NHL. Two research serum banks were established in Washington County, Maryland, in 1974 and 1989, with the collection of blood samples from >45,000 volunteers. Incident NHL cases diagnosed through 2002 (n = 170) were identified among participants by linkage to population-based cancer registries. Two controls were matched to each case (n = 340) on age, sex, and blood draw date. Prediagnostic IgG antibodies to JCV and BKV were measured using virus-like particle ELISA. Associations between JCV and BKV antibody seropositivity and NHL were estimated using conditional logistic regression. Overall, neither antibodies to JCV [odds ratio (OR), 0.83; 95% confidence interval (95% CI), 0.56-1.23] nor BKV (OR, 0.98; 95% CI, 0.64-1.48) were associated with an increased risk of NHL. Results were similar after stratification by NHL subtype or induction period and adjustment for EBV seropositivity. Among those who donated blood in both 1974 and 1989, an increase in JCV antibody levels over time was associated with a 4-fold increased risk of NHL compared with a steep decline in antibody levels (OR, 4.59; 95% CI, 1.30-16.25; P(trend) = 0.02). Whereas JCV seropositivity was not associated with NHL overall, the finding of an increased risk of NHL associated with increasing antibody levels among those who were seropositive at baseline warrants further research into factors influencing reactivation of JCV infection.

Antibodies to JC and BK viruses among persons with non-Hodgkin lymphoma

Two related polyomaviruses, JC virus (JCV) and BK virus (BKV), commonly cause lifelong infections in humans, with periodic reactivation manifesting as viral shedding in urine. Because JCV can infect lymphocytes and cause chromosomal damage, it is a plausible candidate to cause non-Hodgkin lymphoma (NHL). To test this hypothesis, we measured IgG antibodies to JCV and BKV capsids using a virus-like particle enzyme immunoassay in 3 separate groups of subjects. First, in a U.S. population-based case-control study of NHL (724 cases, 622 controls), we found lower JCV antibody levels in cases than controls (median optical density = 0.12 vs. 0.21, p < 0.0001); likewise, JCV seroprevalence was lower in cases (49% vs. 59%, adjusted odds ratio [OR] = 0.70, 95% confidence interval [CI] = 0.56-0.87). In contrast, BKV antibody levels did not differ between groups. Second, we found that JCV and BKV antibody levels changed little over time among 24 NHL patients receiving chemotherapy. Third, we evaluated 126 homosexual men, of whom 46 were shedding JCV and 14 were shedding BKV in urine. Antibody levels were much higher in shedders than non-shedders (JCV: median optical density = 0.67 vs. 0.07, p < 0.0001; BKV: 0.87 vs. 0.40, p = 0.003), indicating that these antibodies are a marker for viral replication. Because no deficit of BKV antibody was seen in NHL cases, and because antibody levels did not change materially with chemotherapy, we suggest that the lower levels of JCV antibody observed in NHL patients may not be due entirely to a disease or treatment effect. Additional research is needed to determine whether JCV replication is decreased in individuals with NHL and whether these findings are consistent with an etiologic role for JCV in NHL.

Distribution, characterization and significance of polyomavirus genomic sequences in tumors of the brain and its covering

The etiology of brain tumors and meningiomas is still unknown. Several factors have been considered, such as genetic predisposition and environmental risk factors, but the hypothesis that one or more infectious agents may play a role in tumor pathogenesis has also been investigated. Therefore, emphasis was placed on the neurooncogenic family Polyomaviridae and the presence of human polyomavirus DNA sequences and JCV mRNA were examined in malignant human brain biopsies. Italian patients affected with different types of neoplasias of the brain and its covering were enrolled. The patients underwent surgical tumor excision and the presence of the polyomavirus genome in biopsy and other body fluids was evaluated by PCR. In addition, the genomic organization of JCV was examined in depth, with the aim of providing information on genotype distribution and TCR rearrangements in the population affected with intracranial neoplasms. On the whole, polyomavirus DNA was found in 50% of the biopsy specimens studied, JC virus DNA and BK virus DNA were amplified in 40.6% mainly glioblastomas and 9.4% of the tissue specimens, respectively, while none of the biopsy specimens tested contained Simian virus 40 DNA. Genotype 1 and Mad 4 TCR organization were the most frequent in the population enrolled. Although a cause and effect was not demonstrated and the specific role of the viruses remains unknown, the findings appear to confirm the hypothesis that JCV and BKV could be important co-factors in tumor pathogenesis.

The human polyomavirus BK: Potential role in cancer

In human cancer, a role has been suggested for the human polyomavirus BK, primarily associated with tubulointerstitial nephritis and ureteric stenosis in renal transplant recipients, and with hemorrhagic cystitis in bone marrow transplant (BMT) recipients. After the initial infection, primarily unapparent and without clinical signs, the virus disseminates and establishes a persistent infection in the urinary tract and lymphocytes. There is correlative evidence regarding potential role of polyomavirus BK in cancer. In fact, the BK virus (BKV) DNA (complete genome and/or subgenomic fragments containing the early region) is able to transform embryonic fibroblasts and cells cultured from kidney and brain of hamster, mouse, rat, rabbit, and monkey. Nevertheless, transformation of human cells by BKV is inefficient and often abortive. Evidence supporting a possible role for BKV in human cancer has accumulated slowly in recent years, after the advent of polymerase chain reaction (PCR). BKV is known to commonly establish persistent infections in people and to be excreted in the urine by individuals who are asymptomatic, complicating the evaluation of its potential role in development of human cancer. Therefore, there is no certain proof that human polyomavirus BK directly causes the cancer in humans or acts as a cofactor in the pathogenesis of some types of human cancer.

Human polyomaviruses and brain tumors

Polyomaviruses are DNA tumor viruses with small circular genomes. Three polyomaviruses have captured attention with regard to their potential role in the development of human brain tumors: JC virus (JCV), BK virus (BKV), and simian vacuolating virus 40 (SV40). JCV is a neurotropic polyomavirus that is the etiologic agent of progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system occurring mainly in AIDS patients. BKV is the causative agent of polyomavirus-associated nephropathy (PVN) which occurs after renal transplantation when BKV reactivates from a latent state during immunosuppressive therapy to cause allograft failure. SV40, originating in rhesus monkeys, gained notoriety when it entered the human population via contaminated polio vaccines. All three viruses are highly oncogenic when injected into the brain of experimental animals. Reports indicate that these viruses, especially JCV, are associated with brain tumors and other cancers in humans as evidenced from the analysis of clinical samples for the presence of viral DNA sequences and expression of viral proteins. Human polyomaviruses encode three non-capsid regulatory proteins: large T-antigen, small t-antigen, and agnoprotein. These proteins interact with a number of cellular target proteins to exert effects that dysregulate pathways involved in the control of various host cell functions including the cell cycle, DNA repair, and others. In this review, we describe the three polyomaviruses, their abilities to cause brain and other tumors in experimental animals, the evidence for an association with human brain tumors, and the latest findings on the molecular mechanisms of their actions.

Evidence against a role for SV40 in human mesothelioma

SV40 has been implicated in the etiology of 40% to 60% of human mesotheliomas. These studies could have important medical implications concerning possible sources of human infection and potential therapies if human tumors are induced by this agent. We did PCR-based analysis to detect SV40 large T antigen DNA in human mesotheliomas. None of 69 tumors in which a single copy gene was readily amplified contained detectable SV40 large T antigen sequences. Under these conditions, it was possible to detect one copy of integrated SV40 DNA per cell in a mixture containing a 5,000-fold excess of normal cells using formalin-fixed preparations. Kidney, a known reservoir of SV40 in monkeys, from some of these individuals were also negative for SV40 large T antigen sequences. A subset of mesotheliomas was analyzed for SV40 large T antigen expression by immunostaining with a highly specific SV40 antibody. These tumors as well as several human mesothelioma cell lines previously reported to contain SV40 large T antigen were negative for detection of the virally encoded oncoprotein. Moreover, mesothelioma cell lines with wild-type p53 showed normal p53 function in response to genotoxic stress, findings inconsistent with p53 inactivation by the putative presence of SV40 large T antigen. Taken together, these findings strongly argue against a role of SV40 by any known transformation mechanism in the etiology of the majority of human malignant mesotheliomas.

Polyomaviruses and human cancer: molecular mechanisms underlying patterns of tumorigenesis

Polyomaviruses are DNA tumor viruses with small circular genomes encoding only six proteins including three structural capsid proteins. Despite this simplicity, our understanding of the mechanisms of polyomavirus-mediated tumorigenesis is far from complete. The archetypal primate polyomavirus, SV40, was isolated more than 40 years ago and has been used extensively as a model system for the study of basic eukaryotic cellular processes such as DNA replication and transcription. Two human polyomaviruses have been isolated from clinical samples: JC virus (JCV) and BK virus (BKV). In this review, SV40, JCV, and BKV will be compared based on what is known about their molecular biology from experiments performed in vitro, in cell culture and in laboratory animals. The association of these viruses with clinical tumors is discussed along with the possible roles of these polyomaviruses in the etiology of human malignant disease.

Molecular characterisation of JC virus strains detected in human brain tumours

AIMS

The aim of this study was to evaluate the presence and significance of JC virus (JCV) in human brain tumours.

METHODS

Histology, immunohistochemistry (IHC) and molecular biology techniques were employed to examine specimens of tumour tissue, peripheral blood and cerebrospinal fluid taken from 22 patients with primary neuro-epithelial tumours. Furthermore, the coding viral protein (VP1) region and non-coding transcription control region (TCR) of JCV genome isolated from the tumours were submitted to sequence analysis in order to detect viral rearrangements or mutations.

RESULTS

JCV genome was found in nine of the 22 tumour specimens (40.9%), including eight astrocyte-derived tumours (seven glioblastomas and one astrocytoma) and one oligodendroglioma, and in two of the 15 cerebrospinal fluid specimens (13.3%) with positive tumour tissue (one glioblastoma and one astrocytoma). Sequence analysis of JCV VP1, which was amplified in seven tissue samples and the two cerebrospinal fluid samples, revealed only genotype 1 (four 1a and three 1b), whereas TCR was amplified in six tissue samples and only one cerebrospinal fluid sample. TCR sequence analysis was possible in four cases and identified three Mad-4 and one type II sequences; the TCR genomic structures of JCV isolated from cerebrospinal fluid were the same as those sequenced from corresponding tumour tissue, thus indicating a possible cerebrospinal fluid dissemination of neoplastic cells carrying viral DNA.

CONCLUSIONS

Our results suggest a possible role of JCV in the induction of brain tumours, especially in those originating from brain cells normally targeted by JCV infection.

Human neurotropic polyomavirus, JCV, and its role in carcinogenesis

A number of recent studies have reported the detection of the ubiquitous human polyomavirus, JC virus (JCV), in samples derived from several types of neural as well as non-neural human tumors. The human neurotropic JCV was first identified as the etiologic agent of the fatal demyelinating disease, progressive multifocal leukoencephalopathy, which usually occurs in individuals with defects in cell-mediated immunity, including AIDS. However, upon mounting evidence of the oncogenic potential of the viral regulatory protein, T-antigen, and JCV's oncogenecity in a broad range of animal models, studies were initiated to determine its potential involvement in human carcinogenesis. Initially, the most frequently observed tumors in rodent models, including medulloblastoma, astrocytoma, glioblastoma, and other neural-origin tumors were analysed. These studies were followed by analysis of non-neural tumors such as colorectal carcinomas. In a subset of each tumor type examined, JC viral genomic DNA sequences could be detected by PCR and confirmed by Southern blot hybridization or direct sequencing. In a smaller subset of the tumors, the expression of T-antigen was observed by immunohistochemical analysis. Owing to the established functions of T-antigen including its ability to interact with tumor suppressor proteins such as Rb and p53, and its ability to influence chromosomal stability, potential mechanisms of JCV T-antigen-mediated cellular dysregulation are discussed. Further, as increasing evidence suggests that T-antigen is not required for maintenance of a transformed phenotype, a hit-and-run model for T-antigen-induced transformation is proposed.

Concomitant progressive multifocal leucoencephalopathy and primary central nervous system lymphoma expressing JC virus oncogenic protein, large T antigen

This report describes the concomitant occurrence of the JC virus (JCV) induced demyelinating disease progressive multifocal leucoencephalopathy (PML) and a primary central nervous system lymphoma (PCNS-L) in a patient with AIDS. Postmortem neuropathological examination revealed characteristic features of PML including multiple lesions of demyelination, enlarged oligodendrocytes with hyperchromatic nuclei (many containing eosinophilic intranuclear inclusions), and enlarged astrocytes with bizarre hyperchromatic nuclei. Immunohistochemical analysis demonstrated the expression of the JCV capsid protein VP-1 in the nuclei of infected oligodendrocytes and astrocytes. The PCNS-L lesion located in the basal ganglia was highly cellular, distributed perivascularly, and consisted of large atypical plasmacytoid lymphocytes. Immunohistochemical examination of this neoplasm identified it to be of B cell origin. Moreover, expression of the JCV oncogenic protein, T antigen, was detected in the nuclei of the neoplastic lymphocytes. This study provides the first evidence for a possible association between JCV and PCNS-L.

Bk virus: a clinical review

We present a review of the clinically oriented literature about BK virus, a relative of JC virus, which is the etiologic agent of progressive multifocal leukoencephalopathy (PML). The kidney, lung, eye, liver, and brain have been proposed as sites of BK virus-associated disease, both primary and reactivated. BK virus has also been detected in tissue specimens from a variety of neoplasms. We believe that BK virus is most often permissively present in sites of disease in immunosuppressed patients, rather than being an etiologic agent that causes symptoms or pathologic findings. There is, however, strong evidence for BK virus-associated hemorrhagic cystitis and nephritis, especially in recipients of solid organ or bone marrow transplants. Now that BK virus can be identified by use of specific and sensitive techniques, careful evaluation of the clinical and pathologic presentations of patients with BK virus will allow us to form a clearer picture of viral-associated pathophysiology in many organ systems.

Simian virus 40 is present in human lymphomas and normal blood

Many independent studies have demonstrated Simian virus 40 (SV40) in normal and neoplastic human tissues. Clonal integration of virus in the DNA of several thyroid and bone tumors suggests a direct role for SV40 in some cancers. However, in most cases the role of SV40 remains unclear. This study determined the presence of SV40, by amplification followed by hybridization, in 266 normal and neoplastic blood and lymphoid samples. Amplification detected SV40 in 14% of non-autoimmune deficiency syndrome (AIDS) lymphomas, 28% of AIDS related lymphoma and 16% of peripheral blood lymphocytes from non-cancerous patients. No SV40 was detected in leukemia samples. Direct Southern blotting of SV40+ samples detected no virus, consistent with less than one viral genome in ten cells. Sequence analysis of SV40 in blood and lymphoid samples found sequences distinct from laboratory strains of SV40. The presence of limited quantities of SV40 in a small proportion of both normal and neoplastic tissues is suggestive of an adventitious presence with no apparent direct role in blood and lymphoid cancers.

JC virus DNA is present in the mucosa of the human colon and in colorectal cancers

JC virus (JCV) is a polyoma virus that commonly infects humans. We have found T antigen DNA sequences of JCV in the mucosa of normal human colons, colorectal cancers, colorectal cancer xenografts raised in nude mice, and in the human colon cancer cell line SW480. A larger number of viral copies is present in cancer cells than in non-neoplastic colon cells, and sequence microheterogeneity occurs within individual colonic mucosal specimens. The improved yield of detection after treatment with topoisomerase I suggests that the viral DNA is negatively supercoiled in the human tissues. These results indicate that JCV DNA can be found in colonic tissues, which raises the possibility that this virus may play a role in the chromosomal instability observed in colorectal carcinogenesis.

An association, in adult Japanese, between the occurrence of rogue cells among cultured lymphocytes (JC virus activity) and the frequency of "simple" chromosomal damage among the lymphocytes of persons exhibiting these rogue cells

Data from a previous study of the cytogenetic effects, in cultured lymphocytes, of exposure to the atomic bomb in Hiroshima have been reanalyzed to determine the relationship between the occurrence of "rogue" cells in an individual and the frequency of "simple" chromosomal damage in the nonrogue cells of the same individual. Rogue cells are cells with complex chromosomal damage, currently believed to be a manifestation of the activity of a human polyoma virus termed "JC." Among a total of 1,835 persons examined, there were 45 exhibiting rogue cells. A total of 179,599 cells were scored for simple chromosomal damage. In both the exposed and the control populations, there was an absolute increase of approximately 1.5% in the frequency of simple chromosomal damage in the nonrogue cells of those exhibiting rogue cells, when compared with the frequencies observed in those not exhibiting rogue cells, which is a statistically significant difference. It is argued that this phenomenon, occurring not only in lymphocytes but possibly also in other cells/tissues, may play a contributory role in the origin of malignancies characterized by clonal chromosome abnormalities. Unexpectedly, among those exhibiting rogue cells, there was a disproportionately greater representation of persons who had received relatively high radiation exposures from the bomb. The reason for this is unclear, but it is tempting to relate the finding to some lingering effect of the exposure (or the circumstances surrounding the exposure) on immunocompetence.