New aspects in the pathogenesis of polyomavirus-induced disease

Virale Infektionen: RNA-Viren

Rhinoviren sind die Haupterreger der sog. Erkältungskrankheiten. Eine wichtige Rolle spielen sie auch als Auslöser von Asthmaattacken.

Es findet eine stete Kozirkulation mehrerer Serotypen statt, im gemäßigten Klima gibt es Herbst-, Winter- und Frühjahrsepidemien, die Übertragung geschieht weit häufiger über infizierte Sekrete als durch Aerosole.

Rhinoviren gehören zu den Picornaviren. Rhinoviren sind sehr kleine Viren mit einem positiven Einzelstrang-RNA-Genom ohne Lipidhülle und daher gegen Detergens enthaltende Desinfektionsmittel sehr resistent. Sie sind empfindlich gegen Umgebungs-pH außerhalb des Bereichs 5,0–7,5.

Zurzeit bilden sie zusammen mit den Enteroviren das Genus Enterovirus der Picornaviren. Serologisch lassen sich über 100 Typen unterscheiden. Kennzeichnend ist die Bindungsfähigkeit an das von den meisten Rhinoviren für die Zelladsorption genützte ICAM-1 (interzelluläres Adhäsionsmolekül).

Nach einer Inkubationszeit von 1–3 Tagen tritt Schnupfen auf, die höchste Viruskonzentration im Nasensekret nach 2–4 Tagen, wiederum nach 2–4 Tagen bei disponierten Patienten auch bronchiale Obstruktion. Es konnte gezeigt werden, dass zu dieser Zeit auch Virus-RNA im Bronchialepithel vorhanden ist. Die postinfektiöse bronchiale Hyperreagibilität korreliert mit der Dauer des Virus-RNA-Nachweises im Nasopharynx. Die Immunität ist im Wesentlichen abhängig von der nur sehr kurzen Anwesenheit sekretorischer spezifischer IgA-Antikörper. Die bei den Serotypen beobachtbare Kreuzreaktivität spiegelt sich nicht in Kreuzimmunität wider.

Virale Infektionen

Adenoviren verursachen im Kindesalter Krankheiten der Atemwege und des Darms, aber auch Krankheiten der Harnwege, der Lymphorgane und kardiologische und neurologische Manifestationen werden beobachtet. Einige typische Krankheitsbilder können klinisch diagnostiziert werden.

Oncogenic T-antigen of JC virus is present frequently in human gastric cancers

BACKGROUND

JC virus (JCV) is a polyomavirus that commonly infects humans and is the causative agent of progressive multifocal leukoencephalopathy in immune-compromised patients. An association between JCV and human cancers long has been suspected, because this virus induces brain tumors in several animal models. The oncogenic potential of JCV is mediated by a transforming protein, the T-antigen (T-Ag), which is a multifunctional protein that transforms cells through interactions with various growth-regulatory genes, including p53 and pRb, and by stabilizing beta-catenin. Previously, the laboratory at the authors' institution demonstrated that JCV is present frequently in the human gastrointestinal tract and may play a role in colorectal carcinogenesis. However, to date, no studies have determined whether JCV sequences are present specifically in gastric cancers. The current study was designed to investigate whether JCV sequences and expression are found in human gastric cancers.

METHODS

DNA was extracted from 23 paraffin embedded and 14 frozen gastric cancer specimens. For the detection of JCV gene sequences, polymerase chain reaction amplifications were performed using gene-specific primers for T-Ag, VP-1 (a JCV capsid gene), and the viral regulatory region (or transcriptional control region). Immunohistochemical staining was performed with an anti-T-Ag monoclonal antibody to detect protein expression.

RESULTS

Twenty-one of 37 gastric cancers (57%) harbored JCV T-Ag sequences, and 13 of 37 gastric cancers (30%) contained VP-1 sequences. T-Ag sequences also were found in adjacent nonneoplastic mucosa. In addition, JCV regulatory region sequences were present frequently in gastric cancers and adjacent nonneoplastic mucosa. T-Ag protein expression was found in 9 of 23 gastric cancers (39%), whereas no expression was observed in any of the nonneoplastic tissues.

CONCLUSIONS

To the authors' knowledge, this is the first demonstration of the presence of JCV T-Ag expression in human gastric cancers. These findings suggest a possible role for this polyomavirus in gastric carcinogenesis.

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.

Real-time, quantitative PCR assays for the detection of virus-specific DNA in samples with mixed populations of polyomaviruses

Mixtures of polyomaviruses can be present in the central nervous system, the gastrointestinal tract, the genitourinary tract, blood, and urban sewage. We have developed 12 primer/probe sets (four per virus) for real-time, quantitative PCR assays (TaqMan) that can specifically detect BKV, JCV, and SV40 genomes present in mixtures of these viruses. The specificities of these primer/probe sets were determined by evaluating their level of interaction with the DNA from other polyomaviruses and their ability to estimate the number of copies of homologous viral DNA in blinded samples of defined mixtures of three polyomaviral DNAs. Three early region and three late region primer/probe sets determined, within a two-fold range, the number of copies of their respective DNAs. Four sets of SV40 primer/probes also detected 1.1-2.4 copies of SV40 DNA per COS-1 cell, cells estimated to contain a single copy of SV40 DNA. Three JCV primer/probe sets detected 3.7-4.2 copies per cell of JCV DNA in the JCV-transformed cell line M1-HR, cells estimated to contain between 0.5 and 1 copy of the JCV genome. We suggest that the virus-specific primer/probe sets in this study be considered sufficiently characterized to initiate the quantification of polyomavirus DNA in biological samples.

Prevalence of BK virus subtype I in Germany

The primary infection with human polyomavirus BK (BKV) occurs in early childhood and leads to viral latency within the urogenital tract. Up to 90% of the adult population are seropositive. In immunosuppressed patients, the BKV may be reactivated resulting in typical disease patterns like hemorrhagic cystitis and tubulointerstitial nephritis. Based on serological and molecular methods, BKV isolates were classified into four subtypes previously. Sixty specimens obtained from German renal and bone marrow transplant recipients were analyzed to gain data on the prevalence of BKV subtypes in Germany. With 90.9%, BKV subtype I was found to be predominant in both patient groups. 6.1% of BKV strains were classified as subtype IV. This pattern of phylogenetic distribution is similar to that demonstrated previously in England, Tanzania, the United States and Japan. Remarkably, there was one German BKV virus with a sequence which clusters together with strain SB in subtype II. The BKV subtype I was found to consist of at least three subgroups designated as Ia, Ib, and Ic. While the majority of the German sequences represent subgroup Ic, most of the Japanese sequences are clearly distinct. These findings support the hypothesis of distinct geographical prevalence of BKV subgroups. For the genotyping region, a relationship of BKV subgroups to disease patterns like hemorrhagic cystitis or tubulointerstitial nephritis could not be demonstrated.

Polyomavirus SV40 infections in Kazakhstan

OBJECTIVES

To examine the prevalence of polyomavirus SV40 infections in Kazakhstan, a central Asian country known to have used potentially contaminated SV40 poliovaccines before 1962.

METHODS

Cross-sectional study of 307 healthy volunteers from two ethnic groups (Kazakhs and Russians) in Almaty, Kazakhstan, from May through August 1999 using a specific SV40 plaque-reduction neutralization assay.

RESULTS

Of the 307 volunteers enrolled in the study, 154 were Kazakhs and 153 were Russians. The overall prevalence of SV40 antibodies was 4.9%, and there was no significant difference between the ethnic groups (p = 0.7) or between males and females. The median SV40 neutralizing antibody titers in Kazakhs and Russians were 1:40 (range 1:10-1:500) and 1:20 (range 1:10-1:500), respectively. The median ages of SV40-infected Kazakhs and Russians were not different (42 vs. 24 years; p = 0.1), although there was a trend for increased seropositivity among older Kazakhs. There was no difference in SV40 positivity between those whose childhoods were spent in rural or in urban areas (p = 0.4). Importantly, 60% (9/15) of the subjects seropositive for SV40 were born from 1969 to 1980s, when poliovaccines were free from SV40.

CONCLUSIONS

This study showed evidence of polyomavirus SV40 infections in Kazakhstan, not only among individuals potentially exposed to contaminated poliovaccines, but in younger people not exposed to such vaccines. As increasing evidence indicates an association of SV40 with selected types of human malignancies, prospective studies are needed to examine the risk of SV40 infection with the development of neoplasias.

Assessment of JC polyoma virus in colon neoplasms

PURPOSE

Research data have recently emphasized an intriguing association of JC polyoma virus with colon carcinogenesis. Tumorigenicity of JC virus is attributed to the T-antigen of its Mad-1 variant. Controversy arose when another research group did not confirm this association. The purpose of this study was to detect JC virus in a series of colon neoplasms from Greek patients.

METHODS

A nested polymerase chain reaction assay was used to detect JC virus in 80 cancerous, 25 adenomatous specimens of large bowel, and 20 colonoscopic biopsy samples from normal patients without colorectal neoplasia. Quantitation of JC virus DNA was performed by real-time polymerase chain reaction.

RESULTS

JC polyoma virus nucleotide sequence was detected in 61 percent of colon adenocarcinomas and in 60 percent of adenomas, at a viral load of 9 x 10(3) to 20 x 10(3) copies/microg DNA. Adjacent normal mucosa in 35 positive colon adenocarcinoma specimens, and normal mucosa from six patients of the control group, had low viral loads (50-450 copies/microg DNA).

CONCLUSIONS

JC polyoma virus genome is present in colon neoplasms. JC virus detection in adenomas at comparable viral loads to malignant tumors suggests its implication at early steps of colonic carcinogenesis. Taking into consideration other published data, infection of colonic epithelium with JC virus might be a prime candidate for a role in chromosomal and genomic instability.

Emergent human pathogen simian virus 40 and its role in cancer

The polyomavirus simian virus 40 (SV40) is a known oncogenic DNA virus which induces primary brain and bone cancers, malignant mesothelioma, and lymphomas in laboratory animals. Persuasive evidence now indicates that SV40 is causing infections in humans today and represents an emerging pathogen. A meta-analysis of molecular, pathological, and clinical data from 1,793 cancer patients indicates that there is a significant excess risk of SV40 associated with human primary brain cancers, primary bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma. Experimental data strongly suggest that SV40 may be functionally important in the development of some of those human malignancies. Therefore, the major types of tumors induced by SV40 in laboratory animals are the same as those human malignancies found to contain SV40 markers. The Institute of Medicine recently concluded that "the biological evidence is of moderate strength that SV40 exposure could lead to cancer in humans under natural conditions." This review analyzes the accumulating data that indicate that SV40 is a pathogen which has a possible etiologic role in human malignancies. Future research directions are considered.

BK polyoma virus allograft nephropathy: ultrastructural features from viral cell entry to lysis

BK virions must enter the host cell and target their genome to the nucleus in order to complete their life cycle. The mechanisms by which the virions accomplish these tasks are not known. In this morphological study we found that BK virions localized beneath the host cell cytoplasmic membrane in 60-70-nm, smooth (non-coated) monopinocytotic vesicles similar to, or consistent with, caveolae. In the cytoplasm, the monopinocytotic vesicles carrying virions appeared to fuse with a system of smooth, vesicles and tubules that communicated with the rough endoplasmic reticulum and was continuous with the Golgi system. Membrane-bound single virions and large tubulo-reticular complexes loaded with virions accumulated in paranuclear locations. Occasional nuclei displayed virions within the perinuclear cisterna in association to the perinuclear viral accumulations. Tubular cells with mature productive infection had large nuclei, distended by daughter virions, whereas they lacked significant numbers of cytoplasmic virions. In addition to virally induced cell necrosis, there was extensive tubular cell damage (apoptosis and necrosis) in morphologically non-infected tubules. The observed ultrastructural interactions between the BK virions and host cells are remarkably similar to viral cell entry and nuclear targeting described for SV40 virus.

BK virus-associated renal problems--clinical implications

BK virus (BKV), a human polyomavirus, infects most of the human population, but clinically relevant infections are usually limited to individuals who are immunosuppressed. After primary infection, BKV remains latent in the kidneys and can be reactivated in immune deficiency conditions, including transplantation. As primary infection occurs in childhood, BKV may be particularly important in the pediatric transplant population. BKV is associated with tubulointerstitial nephritis and ureteric stenosis in renal transplant recipients and hemorrhagic cystitis in bone marrow transplant recipients. There are increasing reports of BKV causing nephropathy and cystitis in non-renal solid organ transplant recipients and other immunodeficiency diseases. This might be related to the use of more potent immunosuppressive regimens or increasing awareness of BKV as an important pathogen. Diagnosis of BKV disease is by biopsy. Histopathological changes in renal biopsy specimens may mimic rejection or drug toxicity, but BKV nuclear inclusions can be seen. Treatment is by reduction of immunosuppression. Antiviral agents such as cidofovir are showing promise. BKV DNA polymerase chain reaction in blood or biopsy may be helpful in monitoring therapy. The impact of BKV disease in children is not well understood and prospective studies are needed to elucidate this further. This article reviews the current understanding of BKV-associated renal problems.

Pathogenesis and management of polyomavirus infection in transplant recipients

Polyomaviruses (JC virus [JCV], BK virus [BKV], and simian virus 40 [SV40]) establish subclinical and persistent infections and share the capacity for reactivation from latency in their host under immunosuppression. JCV establishes latency mainly in the kidney, and its reactivation results in the development of progressive multifocal leukoencephalopathy. BKV causes infection in the kidney and the urinary tract, and its activation causes a number of disorders, including nephropathy and hemorrhagic cystitis. Recent studies have reported SV40 in the allografts of children who received renal transplants and in the urine, blood, and kidneys of adults with focal segmental glomerulosclerosis, which is a cause of end-stage renal disease and an indication for kidney transplantation. Clinical syndromes related to polyomavirus infection are summarized in the present review, and strategies for the management of patients who receive transplants are discussed.

T cell autoimmunity to histones and nucleosomes is a latent property of the normal immune system

OBJECTIVE

Investigators in this study undertook to determine whether in vitro antigen-responsive immune (polyomavirus T antigen [T-ag]- specific) and autoimmune (histone-specific) T cells from normal individuals share structural and genetic characteristics with those from patients with systemic lupus erythematosus (SLE).

METHODS

Histone-specific T cells were generated by stimulation of peripheral blood mononuclear cells (PBMCs) with nucleosome-T-ag complexes and were subsequently maintained by pure histones. T-ag-specific T cell clones were initiated and maintained by T-ag. The frequencies of circulating histone- and T-ag-specific T cells were determined in healthy individuals and in SLE patients by limiting dilution of PBMCs. T cell receptor (TCR) gene usage and variable-region structures were determined by complementary DNA sequencing. These sequences were compared between T-ag- and histone-specific T cells and between normal individuals and SLE patients for each specificity.

RESULTS

Individual in vitro-expanded histone- and T-ag-specific T cells from normal individuals displayed identical TCR V(alpha) and/or V(beta) chain third complementarity-determining region (CDR3) sequences, indicating that they were clonally expanded in vivo. The frequencies of in vitro antigen-responsive T-ag- or histone-specific T cells from normal individuals were similar to those from SLE patients. Although heterogeneous for variable-region structure and gene usage, histone-specific T cells from healthy individuals and SLE patients selected aspartic and/or glutamic acids at positions 99 and/or 100 of the V(beta) CDR3 sequence.

CONCLUSION

Autoimmune T cells from healthy individuals can be activated by nucleosome- T-ag complexes and maintained by histones in vitro. Such T cells possessed TCR structures similar to those from SLE patients, demonstrating that T cell autoimmunity to nucleosomes may be a latent property of the normal immune system.

Quantification of polyoma BK viruria in hemorrhagic cystitis complicating bone marrow transplantation

Polyoma BK virus (BKV) is frequently identified in the urine of bone marrow transplantation (BMT) patients with hemorrhagic cystitis (HC). However, viruria is common even in asymptomatic patients, making a direct causative role of BKV difficult to establish. This study prospectively quantified BK viruria and viremia in 50 BMT patients to define the quantitative relationship of BKV reactivation with HC. Adenovirus (ADV) was similarly quantified as a control. More than 800 patient samples were quantified for BKV VP1 gene with a real-time quantitative polymerase chain reaction. Twenty patients (40%) developed HC, 6 with gross hematuria (HC grade 2 or higher) and 14 with microscopic hematuria (HC grade 1). When compared with asymptomatic patients, patients with HC had significantly higher peak BK viruria (6 x 10(12) versus 5.7 x 10(7) genome copies/d, P <.001) and larger total amounts of BKV excreted during BMT (4.9 x 10(13) versus 7.7 x 10(8) genome copies, P <.001). There was no detectable increase in BK viremia. Binary logistic regression analysis showed that BK viruria was the only risk factor, with HC not related to age, conditioning regimen, type of BMT, and graft-versus-host disease. Furthermore, the levels of ADV viruria in patients with or without HC were similar and comparable with those of BK viruria in patients without HC, suggesting that the significant increase in BK viruria in HC patients was not due to background viral reactivation or damage to the urothelium. BK viruria was quantitatively related to the occurrence of HC after BMT.

Treatment with cytotoxic immunosuppression agents increases urinary excretion of JCV in patients with autoimmune disease

Human JC virus is ubiquitous in human populations and is reactivated frequently in immunosuppressed patients. Fifty-one patients with autoimmune disease receiving immunomodulating therapy were evaluated to study the possible relationship between immunosuppression and JCV viruria. Patients were divided into cytotoxic and noncytotoxic treatment groups based on their prescription. The incidence of JCV viruria in the cytotoxic treatment group was significantly higher than that in the noncytotoxic group (67% vs. 28%; P < 0.05). Most patients with JCV viruria were receiving corticosteroid (P = 0.03 for any dose and P < 0.001 for higher-dose treatments) and cytotoxic agents (P = 0.02). Age, disease duration, and medication duration appeared not to be the precipitating factors of JCV viruria in this study. The results of clinical evaluation indicate that cytotoxic immunosuppression may play an important role in JC virus reactivation.

VP1 DNA sequences of JC and BK viruses detected in urine of systemic lupus erythematosus patients reveal no differences from strains expressed in normal individuals

The ubiquitous human polyomaviruses BK (BKV) and JC (JCV) persist with no adverse effects in immunocompetent individuals. Virus-induced pathogenesis has been linked to virus reactivation during impaired immune conditions. Previous studies have shown a significant difference between the VP1 DNA sequences of JCV obtained from control urine samples and those in progressive multifocal leukoencephalopathy brain samples. This difference could not be detected when comparing normal control urinary JCV DNA with DNA sequences from chronic progressive multiple sclerosis patients. Since BKV and JCV are readily activated in systemic lupus erythematosus (SLE) patients, the presence of specific strains, related to VP1 DNA sequences, was investigated in these patients. VP1 DNA sequences in 100 urine samples from 21 SLE patients and 75 urine samples from 75 healthy pregnant women were analysed and compared to previously reported sequences. The results show that the VP1 sequence profiles of JCV and BKV excreted by SLE patients do not differ significantly from those excreted by immunocompetent individuals. The European JCV subtypes 1A or 1B were represented among all JCV-positive urine specimens, while BKV VP1 sequences showed complete, or almost complete, identity with the MM or JL strains. Different urine samples from the same patient collected over a 1 year period were predominantly stable. BKV VP1 DNA in urine specimens from healthy pregnant women was only detected during the third trimester of their pregnancy. These results argue against SLE-specific JCV and BKV strains and suggest reactivation of the viruses rather than recurrent re-infections of patients with SLE.

Human cytomegalovirus immediate-early gene 2 expression leads to JCV replication in nonpermissive cells via transcriptional activation of JCV T antigen

Human papovavirus JCV is the causative agent of the demyelinating brain disease progressive multifocal leukoencephalopathy (PML) that typically develops as a complication of impaired immunocompetence. JCV displays a strong tropism for glial cells which is correlated by glial-specific transcriptional regulation of viral gene expression. In a previous report HCMV was shown to overcome the restricted cell specificity of JCV by inducing DNA replication of a PML-derived JCV strain in human fibroblasts which are nonpermissive for the replication of JCV alone. Here we show that productive JCV replication is induced by HCMV in human glioblastoma cells. Both in fibroblasts and in glioblastoma cells, the HCMV immediate-early transactivator 2 (IE2) is sufficient to mediate JCV replication. Furthermore, IE2 induces DNA replication of several structurally different brain- or kidney-derived JCV variants. IE2-induced JCV DNA replication is accompanied by the induction of JCV T antigen expression due to stimulation of the JCV early promoter. Our results indicate that stimulation of JCV early gene expression by HCMV-IE2 is sufficient to overcome the restricted cell specificity of JCV.

Quantification of human polyomavirus JC in brain tissue and cerebrospinal fluid of patients with progressive multifocal leukoencephalopathy by competitive PCR

Activation of human polyomavirus JC (JCV) infection is the cause of the central nervous system (CNS) disease progressive multifocal leukoencephalopathy (PML). Previous studies with uncontrolled quantification systems suggested that the virus load in the CNS correlates with the state of disease and might reflect therapeutic effects. Therefore the aim of this study was the development of a competitive system with standard PCR techniques that allowed rapid detection of JCV subtypes, simultaneous differentiation of the two human polyomaviruses JCV and BKV and absolute quantification of the virus burden in initial diagnosis and progressive disease states. Subtype- and species-specificity of the PCR was achieved with the development of a degenerative PCR primer pair that detected JCV DNA in a range regularly found in PML samples, but did not amplify BKV DNA. The accuracy of the system was evaluated by quantification of known amounts of cloned JCV DNA with a competitive JCV-specific template that exhibited a comparable amplification rate to that of the native product. The calibration study demonstrated a linear correlation over a wide range of DNA concentrations on the background of buffer or JCV-negative diagnostic samples. The reliability of the system for PML diagnosis was analysed by calibration and determination of the virus burden in tissue and cerebrospinal fluid (CSF) of 11 PML patients confirming the accuracy in both types of samples under diagnostic conditions. Comparison of the JCV DNA concentration in tissue and CSF by a tightly controlled quantification technique revealed for the first time differences in a range of about four orders of magnitude and a variable virus load in CSF samples taken at comparable states of disease. This pointed to an individual course of virus shedding and demonstrates that a controlled competitive PCR system of high accuracy is essential for reliable quantification of virus DNA either in initial diagnosis, in progressive disease or for the evaluation of therapeutic effects.

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.