Mutagenic activity of BKV and JCV in human and other mammalian cells

Mohamed S, Gouda W. Case-control study: Unveiling human polyomaviruses and papillomavirus in Egyptian colorectal cancer patients

BACKGROUND

Colorectal cancer (CRC) is a cancer type that is thought to be influenced by human papillomaviruses (HPVs) and human polyomaviruses (HPyVs). In Egypt, CRC ranks as the 7th most common cancer, accounting for 3.47% of male cancers and 3% of female cancers. However, there is currently a lack of information regarding the presence of PyVs and HPVs co-infection specifically in CRC cases in Egypt. Therefore, the aim of this study was to investigate the occurrence of HPVs and HPyVs (JCPyV, BKPyV, and SV40) infections, as well as co-infections, among CRC patients in Egypt. Additionally, the study aimed to assess any potential association between these viral infections and tumor stages.

METHODS

In the present study, we analyzed a total of 51 tissue samples obtained from Egyptian CRC patients, along with 19 polyps' samples. Our investigation focused on the detection and genotyping of HPyVs using Real-Time PCR. Additionally, we employed real-time PCR for the detection of HPVs, and for their genotyping, we utilized a combination of PCR amplification followed by sequencing.

RESULTS

In our study, we found evidence of HPyVs infection in the CRC patients, specifically SV40 (25.5%) and BKPyV (19.6%). However, JCPyV was not detected in the samples that were examined. Additionally, we discovered that HPV was present in 43.1% of the CRC patients. When considering viral co-infections, 19.6% of the CRC samples showed coexistence of multiple viruses, while no co-infections were found in the polyps samples. Importantly, we observed a significant correlation between the presence of HPVs and advanced colorectal tumor grades B2 and D.

CONCLUSION

Our findings provide valuable data for the detection of oncogenic viruses in colorectal cancer (CRC) and underscore the association of viral co-infections with advanced tumor stages. However, further research with larger cohorts is necessary to validate these findings and strengthen their significance in the field of CRC.

BK nephropathy in the native kidneys of patients with organ transplants: Clinical spectrum of BK infection

Nephropathy secondary to BK virus, a member of the Papoviridae family of viruses, has been recognized for some time as an important cause of allograft dysfunction in renal transplant recipients. In recent times, BK nephropathy (BKN) of the native kidneys has being increasingly recognized as a cause of chronic kidney disease in patients with solid organ transplants, bone marrow transplants and in patients with other clinical entities associated with immunosuppression. In such patients renal dysfunction is often attributed to other factors including nephrotoxicity of medications used to prevent rejection of the transplanted organs. Renal biopsy is required for the diagnosis of BKN. Quantitation of the BK viral load in blood and urine are surrogate diagnostic methods. The treatment of BKN is based on reduction of the immunosuppressive medications. Several compounds have shown antiviral activity, but have not consistently shown to have beneficial effects in BKN. In addition to BKN, BK viral infection can cause severe urinary bladder cystitis, ureteritis and urinary tract obstruction as well as manifestations in other organ systems including the central nervous system, the respiratory system, the gastrointestinal system and the hematopoietic system. BK viral infection has also been implicated in tumorigenesis. The spectrum of clinical manifestations from BK infection and infection from other members of the Papoviridae family is widening. Prevention and treatment of BK infection and infections from other Papovaviruses are subjects of intense research.

New insights on the association between the prostate cancer and the small DNA tumour virus, BK polyomavirus

In recent years the scientific literature in the field of the prostate carcinoma (PCa) pointed out on the genetic heterogeneity and mutations occurring in this tumour, while little attention was given to the causes of PCa onset, in particular infectiuos agents. In this brief commentary, we wish to point out recent advancements done on the role of the human polyomavirus BK (BKPyV) in the development of PCa by harnessing both humoral and cellular immune responses. Altogether, these new insights suggest that BKPyV is involved in the transforming activity during the multistep process of PCa development. Although these findings do not provide evidence for a causal relationship between BKPyV and PCa development, additional investigations with novel techniques will help to make it a concrete event.

Polyomavirus BK and prostate cancer: a complex interaction of potential clinical relevance

Several studies associating BK polyomavirus (BKPyV) and prostate cancer (PCa) suggested that this virus may exert its oncogenic activity at early stages of cancer development. The BKPyV oncogene, the large T antigen (LTag), has frequently been detected in areas of proliferative inflammatory atrophy, which is considered a precursor lesion leading to prostatic intraepithelial neoplasia and overt PCa. In a recently updated systematic review, the presence of BKPyV was significantly higher in PCa tissues than in healthy control tissues, providing an indication for a link between BKPyV infection and cancer risk. In addition, recent original investigations highlighted an association between expression of the virus and the clinical course of PCa. For example, by studying immune responses elicited against BKPyV LTag, a significant association between LTag positive cancer lesions and a peculiar regulatory profiling has been observed in PCa patients with evidence of disease recurrence after surgical radical prostatectomy. Lastly, a study carried out in a larger cohort of patients undergoing radical prostatectomy revealed the IgG response against LTag as an independent predictor of disease recurrence. Although a full picture of the mechanisms potentially responsible for the involvement of BKPyV in PCa is not available yet, continuing work on this topic should help to refine the potential role of BKPyV in PCa patients, perhaps revealing unsuspected associations with the clinical course of this disease.

BK polyomavirus from patients with tissue-derived prostate adenocarcinoma

Aim: To explore the potential role of BK polyomavirus (BKV) in prostate tumorigenesis. Materials & methods: A total of 82 patients (no immunosuppression history) were divided into two groups. Group 1 included 32 patients receiving radical prostatectomy due to prostate adenocarcinoma. Group 2 consisted of 50 patients receiving transurethral resection of prostate or incision of prostate (TUIP) due to benign prostatic hyperplasia. Prostate tissue specimens of group 1 were obtained from two regions of the prostate: one was from the peripheral section of the prostate or proximal to the region where adenocarcinoma was confirmed by the preoperative needle biopsies (mark A region), the other was from the central section of the prostate or distal from the region where adenocarcinoma was confirmed by the needle biopsies (mark B region). If BKV alone was detected in either of the two regions, that case was regarded as BKV-positive prostate cancer. Those of group 2 were obtained from transrectal prostate biopsy before transurethral resection of prostate or transurethral incision of the prostate. Total DNA was extracted from each of the tissues and subjected to single or nested PCR using the β-globin system to detect targeted sequences within: the LTag gene; the VP1 gene and the transcriptional control region (TCR). Results: In group 1, BKV DNA sequences were detected in six cases (18.8%, 6/32), which were all in the A regions. Among the six cases, there were four cases with all of LTag, VP1 and TCR amplified, one case with LTag and TCR amplified, and one case with only the LTag amplified. In group 2, there was only one case (2.0%, 1/50) in which BKV DNA sequences were detected, and the only amplified fragment was VP1. The difference between the two groups was statistically significant (p = 0.008). Conclusion: BKV is often detected in the prostate cancer tissue and may be associated with progression of prostate cancer.

DNA viruses and the cellular DNA-damage response

It is clear that a number of host-cell factors facilitate virus replication and, conversely, a number of other factors possess inherent antiviral activity. Research, particularly over the last decade or so, has revealed that there is a complex inter-relationship between viral infection and the host-cell DNA-damage response and repair pathways. There is now a realization that viruses can selectively activate and/or repress specific components of these host-cell pathways in a temporally coordinated manner, in order to promote virus replication. Thus, some viruses, such as simian virus 40, require active DNA-repair pathways for optimal virus replication, whereas others, such as adenovirus, go to considerable lengths to inactivate some pathways. Although there is ever-increasing molecular insight into how viruses interact with host-cell damage pathways, the precise molecular roles of these pathways in virus life cycles is not well understood. The object of this review is to consider how DNA viruses have evolved to manage the function of three principal DNA damage-response pathways controlled by the three phosphoinositide 3-kinase (PI3K)-related protein kinases ATM, ATR and DNA-PK and to explore further how virus interactions with these pathways promote virus replication.

JC virus: an oncogenic virus in animals and humans?

JC virus (JCV) is a human polyomavirus of the Polyomaviridae family, which also includes BK virus and simian vacuolating virus 40 (SV40). JC virus was first isolated in 1971 from the brain of a patient with Progressive Multifocal Leukoencephalopathy (PML). Like other polyomaviruses, JCV has a restricted host range. The virus infects the majority of the human population with seroconversion occurring during adolescence. JCV has a limited and specific tissue tropism infecting the kidney and oligodendrocytes and astrocytes in the central nervous system (CNS). Initial JCV infection is generally asymptomatic in immunocompetent hosts, and it establishes a persistent infection in the kidney and possibly bone marrow. In immunocompromised individuals JCV can cause a lytic infection in the CNS and lead to development of the fatal, demyelinating disease PML. The name polyoma is derived from the Greek terms: poly, meaning many, and oma, meaning tumors, owing to the capacity of this group of viruses to cause tumors. JCV inoculation of small animal models and non-human primates, which are not permissive to a productive JCV infection, leads to tumor formation. Given the ubiquitous nature of the virus and its strong association with cancer in animal models, it is hypothesized that JCV plays a role in human cancers. However, the role for JCV in human cancers and tumor formation is not clear. Some researchers have reported an association of JCV with human cancers including brain tumors, colorectal cancers, and cancers of the gastrointestinal tract, while other groups report no correlation. Here, we review the role of JCV in cancers in animal models and present the findings on JCV in human cancers.

BK virus and human cancer: innocent until proven guilty

BK virus (BKV) is a polyomavirus that ubiquitously infects the human population. Following a typically subclinical primary infection, BKV establishes a life-long persistent infection in the kidney and urinary tract. BKV is known to reactivate and cause severe disease in immunosuppressed patients, particularly renal and bone marrow transplant patients. Infection of BKV in rodent animal models or cells in culture often results in tumor formation or transformation, respectively. When co-expressed with activated oncogenes, BKV large tumor antigen drives the transformation of primary human cells. An etiological role of BKV in human cancer, however, remains controversial. Multiple reports have demonstrated conflicting results in regards to the presence of BKV sequences and/or proteins in various tumor types. This review compiles the most recent findings of BKV detection in a number of human cancers. Due to the lack of conclusive causality data from these studies, there does not appear to be a definitive association between BKV and human cancers.

BK virus as a cofactor in the etiology of prostate cancer in its early stages

Prostate cancer has been projected to cause almost 10% of all male cancer deaths in the United States in 2007. The incidence of mutations in the tumor suppressor genes Rb1 and p53, especially in the early stages of the disease, is low compared to those for other cancers. This has led to the hypothesis that a human virus such as BK virus (BKV), which establishes a persistent subclinical infection in the urinary tract and encodes oncoproteins that interfere with these tumor suppressor pathways, is involved. Previously, we detected BKV DNA in the epithelial cells of benign and proliferative inflammatory atrophy ducts of cancerous prostate specimens. In the present report, we demonstrate that BKV is present at a much lower frequency in noncancerous prostates. Additionally, in normal prostates, T-antigen (TAg) expression is observed only in specimens harboring proliferative inflammatory atrophy and prostatic intraepithelial neoplasia. We further demonstrate that the p53 gene from atrophic cells expressing TAg is wild type, whereas tumor cells expressing detectable nuclear p53 contain a mix of wild-type and mutant p53 genes, suggesting that TAg may inactivate p53 in the atrophic cells. Our results point toward a role for BKV in early prostate cancer progression.

Polyomaviruses and human diseases

Polyomaviruses are small, nonenveloped DNA viruses, which are widespread in nature. In immunocompetent hosts, the viruses remain latent after primary infection. With few exceptions, illnesses associated with these viruses occur in times of immune compromise, especially in conditions that bring about T cell deficiency. The human polyomaviruses BKV and JCV are known to cause, respectively, hemorrhagic cystitis in recipients of bone marrow transplantation and progressive multifocal leukoencephalopathy in immunocompromised patients, for example, by HIV infection. Recently, transplant nephropathy due to BKV infection has been increasingly recognized as the cause for renal allograft failure. Quantitation of polyomavirus DNA in the blood, cerebrospinal fluid, and urine, identification of virus laden "decoy cells" in urine, and histopathologic demonstration of viral inclusions in the brain parenchyma and renal tubules are the applicable diagnostic methods. Genomic sequences of polyomaviruses have been reported to be associated with various neoplastic disorders and autoimmune conditions. While various antiviral agents have been tried to treat polyomavirus-related illnesses, current management aims at the modification and/or improvement in the hosts' immune status. In this chapter, we provide an overview of polyomaviruses and briefly introduce its association with human diseases, which will be covered extensively in other chapters by experts in the field.

Transforming Activities of JC Virus Early Proteins

Polyomaviruses, as their name indicates, are viruses capable of inducing a variety of tumors in vivo. Members of this family, including the human JC and BK viruses (JCV, BKV), and the better characterized mouse polyomavirus and simian virus 40 (SV40), are small DNA viruses that commandeer a cell's molecular machinery to reproduce themselves. Studies of these virus-host interactions have greatly enhanced our understanding of a wide range of phenomena from cellular processes (e.g., DNA replication and transcription) to viral oncogenesis. The current chapter will focus upon the five known JCV early proteins and the contributions each makes to the oncogenic process (transformation) when expressed in cultured cells. Where appropriate, gaps in our understanding of JCV protein function will be supplanted with information obtained from the study of SV40 and BKV.

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.

The polyomavirus, JCV and its involvement in human disease

The human neurotropic polyomavirus, JC virus (JCV), is the etiologic agent of progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system that occurs mainly in immunosuppressed patients. JCV has also been found to be associated with human tumors of the brain and other organs. In this chapter, we describe JC virus and its role in human diseases.

Expression of JC virus regulatory proteins in human cancer: potential mechanisms for tumourigenesis

JC virus (JCV) is a human polyomavirus that is the etiologic agent of the fatal demyelinating disease of the central nervous system known as progressive multifocal leukoencephalopathy (PML). JCV is also linked to some tumours of the brain and other organs as evidenced by the presence of JCV DNA sequences and the expression of viral proteins in clinical samples. Since JCV is highly oncogenic in experimental animals and transforms cells in culture, it is possible that JCV contributes to the malignant phenotype of human tumours with which it is associated. JCV encodes three non-capsid regulatory proteins: large T-antigen, small t-antigen and agnoprotein that interact with a number of cellular target proteins and interfere with certain normal cellular functions. In this review, we discuss how JCV proteins deregulate signalling pathways especially ones pertaining to transcriptional regulation and cell cycle control. These effects may be involved in the progression of JCV-associated tumours and may represent potential therapeutic targets.

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.

Detection and expression of human BK virus sequences in neoplastic prostate tissues

BK virus (BKV) is ubiquitous in the human population and establishes a lifelong, subclinical persistent infection in the urinary tract. When the immune system is compromised, it can cause severe disease in the kidney and bladder. Detection of BKV sequences in urinary tract neoplasms has led to the postulate that this virus may induce human oncogenesis through the function of its large tumor antigen (TAg). In this study, examination of prostate tumor tissue sections using in situ hybridization shows the presence of BKV sequences in atrophic epithelium. Solution polymerase chain reaction on DNA extracted from the tissues and sequence analysis of the products reveal the presence of BKV regulatory and early region sequences. In addition, immunohistochemical analysis using monoclonal antibodies specific to TAg or p53 shows the expression of TAg in some of the samples and p53 staining that can be correlated to TAg expression. Although the normal cellular localization of TAg and p53 is nuclear, double immunofluorescence labeling with anti-p53 and TAg antibodies indicates colocalization of p53 and TAg to the cytoplasm in the glandular epithelial cells of the sections. Although BKV DNA was found in benign and atrophic lesions, TAg and p53 coexpression was observed only in atrophic lesions.

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.

JCV T-antigen interacts with the neurofibromatosis type 2 gene product in a transgenic mouse model of malignant peripheral nerve sheath tumors

The human polyomavirus, JC virus, has recently been associated with several human CNS tumors, including medulloblastomas and a broad range of glial-origin tumors. This ubiquitous virus is the causative agent of the rare demyelinating disease, progressive multifocal leukoencephalopathy in immunocompromised individuals. Expression of the viral protein, T-antigen, which possesses the ability to transform cells of neural origin, has been detected in human CNS tumors. In an effort to further understand the transforming potential of JCV T-antigen, transgenic mice expressing JCV T-antigen under the control of the Mad-4 promoter were generated. As described previously, approximately 50% of the animals developed pituitary tumors by 1 year of age. However, a small subset of the animals developed solid masses arising from the soft tissues surrounding the salivary gland, the sciatic nerve, and along the extremities that histologically resemble malignant peripheral nerve sheath tumors, rare neoplasms that occur in individuals with neurofibromatosis type 1 (NF1). JCV T-antigen was detected in tumor tissue by immunohistochemistry and immunoprecipitation/Western blotting, but not in normal tissues and was colocalized with NF2, the putative tumor suppressor protein associated with neurofibromatosis type 2, in the nucleus of some cells. In addition, T-antigen was co-precipitated with NF2, but not with NF1 protein, although NF1 was detectable in tumor tissue. Furthermore, precipitated immunocomplexes contained T-antigen, NF2, and p53, suggesting that these three proteins may form a ternary complex. The importance of these findings on mechanisms of T-antigen-mediated tumorigenesis and the pathogenesis of neurofibromatosis are discussed. Oncogene (2004) 23, 5459-5467. doi:10.1038/sj.onc.1207728 Published online 10 May 2004

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.

Oncogenic transformation by BK virus and association with human tumors

BK virus (BKV), a human polyomavirus closely related to JC virus and Simian Virus 40, is ubiquitous in human populations worldwide. After primary infection, BKV establishes a lifelong latent infection in many organs. BKV transforms rodent cells to the neoplastic phenotype and is highly oncogenic in rodents. This review considers the oncogenic potential of BKV in humans and its possible involvement in human tumors. BKV sequences and T antigen (Tag) are detected in several types of human neoplasms, although the viral load is generally low, with less than one copy of the viral genome per cell. The possible causative role of BKV in human oncogenesis rests on the ability of BKV Tag to inactivate the functions of tumor suppressor proteins p53 and pRB family as well as on its ability to induce chromosomal aberrations in human cells. A 'hit and run' mechanism and secretion of paracrine growth factors by BKV Tag-positive cells, recruiting into proliferation neighboring and distant cells, are discussed as possible BKV pathogenic elements in human oncogenesis.

Analysis of the excreted JC virus strains and their potential oral transmission

JC virus (JCV) particles have been detected in urban sewage of divergent geographical areas. In this study, the authors evaluate the genetic characteristics and the infective capabilities of JCV strains in relation to the potential oral transmission of JCV in the population. JCV strains excreted in urine and detected in sewage have been described as presenting archetypal structure of the regulatory region of the viral genome. The regulatory region of JCV viral particles detected in two urban sewage samples have been cloned and characterized. From a total of 40 clones tested, 39 presented archetypal-like regulatory regions, whereas 1 of the clones analyzed presented a tandem repeated structure. Archetypal strains present in the urine of a pregnant woman were able to infect SVG cells, producing infectious virions, as demonstrated by confirmative cell culture, electron microscopy, and in situ DNA hybridization. This is the first description of archetypal JCV productive infection of SVG cells. SVG cells were also successfully infected with Mad-4 JCV viral particles subjected to pH 3 for 1 h at 37 degrees C and to 10 microg/ml of trypsin in the same conditions. A decrease in the viral progeny production was observed when Mad-4 was subjected to acidic pH. Mad-4 did not produce any detectable infection in the enteric cell line CaCo-2. The oral route could represent a significant route of transmission of JCV infections because JCV virions have demonstrated relative resistance in the environment and to some of the conditions present in the gastrointestinal tract. The archetypal strains commonly detected in the environment may be implicated in the transmission of JCV among the population. Sporadic infection with strains presenting tandem repeated structures may have implications in pathogenicity.

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.

Chromosomal aberrations induced by BK virus T antigen in human fibroblasts

Human fibroblasts, transfected with a recombinant DNA containing the neo gene and BK virus (BKV) early region, which expresses BPV large T antigen (TAg), show cytogenetic alterations characterized by dicentric chromosomes and other structural aberrations such as deletions, duplications, translocations, and ring chromosomes. Such alterations were absent or significantly less frequent in human fibroblasts transfected with a plasmid expressing only the neo gene. The chromosome damage in BKV-transfected cells was evident before the appearance of the morphologically transformed phenotype and therefore seems to be a primary effect of TAg expression in human cells. The specific pattern of chromosome aberrations suggests the prevalence of an indirect clastogenic effect, determined by the inhibition of p53 regulatory functions on genome stability by BKV TAg. Due to the widespread distribution of BKV in the human population and to the latent state of BKV DNA in many human organs, the clastogenic activity of BKV TAg may potentially participate in an oncogenic process involving BKV latently infected cells.

Increased frequency of specific locus mutation following human cytomegalovirus infection

The effect of human cytomegalovirus (HCMV) infection on the frequency of mutations at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus was studied in Chinese hamster lung V79 cells. When V79 cells were infected with HCMV (strain AD169) at multiplicities of 0.1 to 50 plaque forming units (PFU) per cell the presumptive mutation frequency, as determined by the number of 6-thioguanine-resistant (TGr) colonies, was increased up to 16.8-fold (P < 0.005), depending on the multiplicity of infection. Increases in the mutation frequency at the hprt locus were also observed for other laboratory-adapted HCMV strains (C-87, Davis) and for low passage clinical isolates (82-1, 84-2). The expression time required for the maximum increase in TGr colonies was 3 days and was consistent among the HCMV strains evaluated in this study. UV-irradiation of HCMV stock up to a dose of 9.6 x 10(4) ergs/mm2 increased the mutation frequency, but further exposure to UV light or to heat (56 degrees for 30 min) significantly decreased the frequency of TGr-resistant colonies, suggesting that expression of HCMV genes was involved in the mutation process. HCMV-induced TGr cells demonstrated substantially reduced (> 96%) incorporation of [3H]hypoxanthine. PCR analysis of the hprt locus demonstrated deletions in 9 of 19 HCMV-induced TGr colonies randomly selected for further study, while 2 of 17 spontaneously developed TGr colonies demonstrated deletions. Although insertions were not detected in spontaneously developed clones, 3 of 19 HCMV-induced TGr clones had insertions in the hprt gene. Neither HCMV-specific DNA sequences nor HCMV-specific proteins were detected in the TGr clones obtained after HCMV infection. Infection of V79 cells with HCMV also increased their sensitivity to mutation with N-methyl-N'-nitro-N-nitrosoguanidine, giving a synergistic enhancement of the mutation frequency. These results indicate that HCMV infection has the capacity to induce mutations in the cellular genome and increase the sensitivity of infected cells to mutation by genotoxic chemicals. Although inactivated HCMV particles are responsible for a modest increase in the mutation frequency, expression of HCMV genes is associated with a substantial enhancement of the mutation frequency.

Large T antigen coding sequences of two DNA tumor viruses, BK and SV40, and nonrandom chromosome changes in two glioblastoma cell lines

The T antigen (TAg) coding sequences of two DNA tumor viruses, BKV and SV40, were detected by Polymerase Chain Reaction (PCR) amplification followed by Southern-blot hybridization in two human glioblastoma multiforme derived cell lines. RT-PCR analysis indicated that these two TAg coding sequences were expressed in both tumor cell lines carrying the viral early region DNAs. Moreover, analytical polyacrylamide gel electrophoresis (PAGE) and DNA sequence analyses showed that the amplified PCR products are indistinguishable from the TAg coding sequences of BKV and SV40 wildtype strains. Cytogenetic study performed in the two cell lines showed unbalanced changes, mainly gains of chromosomes 3p, 5, 6, 7, and 19 and losses of chromosomes 3, 3q, 16, 9p22-->pter, 18, and 20. Excess of chromosomes 6 and 7 are common to the two cell lines. The putative role of the TAg of the two DNA tumor viruses in transformation and karyotype changes is discussed.

High incidence of BK virus large-T-antigen-coding sequences in normal human tissues and tumors of different histotypes

T-antigen (TAg) coding sequences specific for BK virus (BKV) were detected, by PCR amplification followed by Southern-blot hybridization, in a high percentage of human tumors and tumor-cell lines, as well as in normal tissues, by analysis of 189 specimens. Specifically, the BKV early region was detected in 85% of brain tumors and in all normal brain tissues, in 78% of osteosarcomas, in 38% of Ewing's tumors, in 40% of normal bone specimens and in 71% of normal peripheral blood cell samples. Wilms' tumor tissues used as a control were all negative for BKV sequences. RT-PCR analysis indicated that TAg coding sequences were expressed in specimens carrying BKV early region, ranging from 64% of the osteosarcomas to 100% of glioblastomas, Ewing's tumors, peripheral blood cells and normal bone. Moreover, DNA sequencing performed in 12 different positive samples revealed that the amplified PCR products are identical to the early-region sequence of wild-type BKV. The role of BKV TAg and its possible mechanism of action in human tumorigenesis are discussed.

An immunohistochemical study of p53 and proliferating cell nuclear antigen expression in progressive multifocal leukoencephalopathy

Nuclear p53 immunoreactivity is demonstrated in infected oligodendroglia, as well as in a proportion of reactive and bizarre astrocytes, in seven progressive multifocal leukoencephalopathy (PML) biopsies. This likely represents binding to, and prolongation of the half-life of, wild-type p53 protein by JC virus T-antigen. Other possible mechanisms are considered. The same cells show proliferating cell nuclear antigen (PCNA) positivity, as do a proportion of morphologically normal oligodendroglia and astrocytes, reflecting proliferating populations of these glial sub-types. It is possible that functional inactivation of p53 in nonlytically infected astrocytes may allow neoplastic astrocyte clones to emerge. However, p53 and PCNA immunoreactivity per se cannot be regarded as indicative of neoplasia in PML, and caution must be exercised in the interpretation of such nuclear staining profiles.