Persistence of DNA sequences of BK virus and JC virus in normal human tissues and in diseased tissues

Latent and Productive Polyomavirus Infections of Renal Allografts

Polyomavirus allograft nephropathy, also termed BK virus nephropathy (BKN) after the main causative agent, the polyoma-BK-virus strain, is a major complication following kidney transplantation. BKN is the most common viral infection affecting the renal allograft with a reported prevalence of 1% up to 10%. It often leads to chronic allograft dysfunction and graft loss. BKN is most likely caused by the reactivation of latent BK viruses which, under sustained and intensive immunosuppression, enter a replicative/productive cycle. Viral disease, i.e., BKN, is typically limited to the kidney transplant. It is histologically defined by the presence of intranuclear viral inclusion bodies in epithelial cells and severe tubular injury. Virally induced tubular damage is the morphological correlate for allograft dysfunction. In this chapter, different variants of polyomavirus intranuclear inclusion bodies [types 1 through 4] and adjunct techniques [immunohistochemistry, in-situ hybridization, electron microscopy and polymerase chain reaction (PCR)] that are used for proper characterization of disease are described. Special emphasis is placed on the clinical and pathophysiological significance of different histological stages of BKN.

Discovery and epidemiology of the human polyomaviruses BK virus (BKV) and JC virus (JCV)

Although discovered over thirty years ago, many aspects of the epidemiology of BKV and JCV in the general population, such as the source of infectious virus and the mode of transmission, are still unknown. Primary infection with both BKV and JCV is usually asymptomatic, and so age seroprevalence studies have been used to indicate infection. BKV commonly infects young children in all parts of the world, with the exception of a few very isolated communities, adult seroprevalence rates of 65-90% being reached by the age of ten years. In contrast, the pattern of JCV infection appears to vary between populations; in some anti-JCV antibody is acquired early as for BKV, but in others anti-JCV antibody prevalence continues to rise throughout life. This indicates that the two viruses are probably transmitted independently and by different routes. Whilst BKV DNA is found infrequently in the urine of healthy adults, JCV viruria occurs universally, increasing with age, with adult prevalence rates often between 20% and 60%. Four antigenic subtypes have been described for BKV and eight genotypes are currently recognized for JCV. The latter have been used to trace population movements and to reconstruct the population history in various communities.

Urine cytology findings of polyomavirus infections

Polyomaviruses of the BK- and JC-strains often remain latent within the transitional cell layer of the bladder, ureters and the renal pelvis as well as in tubular epithelial cells of the kidney. Slight changes in the immune status and/or an immunocompromised condition can lead to the (re)activation of latent polyomaviruses, especially along the transitional cell layer, resulting in the shedding of viral particles and infected cells into the urine. A morphologic sign of the (re)activation of polyomaviruses is the detection of typical intranuclear viral inclusion bearing epithelial cells, so-called "decoy cells", in the urine. Decoy cells often contain polyoma-BK-viruses. The inclusion bearing cells are easily identified and quantifiable in routine Papanicolaou stained urine cytology specimens. With some experience, decoy cells can also be detected in the unstained urinary sediment by phase contrast microscopy. Different morphologic variants of decoy cells (types 1 through 4) are described and ancillary techniques (immunohistochemistry, electron microscopy (EM), and fluorescence-in-situ-hybridization (FISH)) for proper identification and characterization are discussed. Special emphasis is placed on the clinical significance of the detection of decoy cells as a parameter to assess the risk for disease, i.e., polyoma-BK-virus nephropathy (BKN) in kidney transplant recipients. The sensitivity and specificity of decoy cells for diagnosing BKN is 99% and 95%, respectively, the positive predictive value varies between 27% and more than 90%, and the negative predictive value is 99%. The detection of decoy cells is compared to other techniques applicable to assess the activation of polyomaviruses in the urine (polymerase chain reaction (PCR) and EM).

Immune responses to BK and JC viruses in immunocompromised patients

BK virus (BKV) and JC virus (JCV) are ubiquitous human polyomaviruses that establish persistent asymptomatic infections in immunocompetent individuals, but in a minority of immunocompromised patients, reactivate and cause clinical disease. BKV is associated with BKV nephropathy (BKVN) in kidney transplant recipients and JCV is the etiologic agent of progressive multifocal leukoencephalopathy (PML) in AIDS patients. Humoral responses do not appear adequate to protect against reactivation or disease, and both BKVN and PML appear to be due to a failure of cellular immune responses to control the virus. Among the goals of current research is the identification of the functional correlates of cellular immune protection against these viruses in immunocompetent individuals. Such insights may help identify the small subset of patients at risk of BKV and JCV reactivation, aid clinical management and permit the development of immunotherapeutic approaches.

Relationships between BK virus lineages and human populations

BK polyomavirus (BKV) is ubiquitous in human populations, infecting children asymptomatically and then persisting in the kidney, in which it can cause nephropathy in renal transplant patients. BKV isolates are classified into four subtypes (I-IV) using serological or genotyping methods, and subtype I is further divided into four subgroups, Ia, Ib-1, Ib-2, and Ic, based on DNA sequence variations. To clarify whether there is an association between BK virus lineages and human populations, we examined BKV-positive urine samples collected from immunocompetent individuals at various locations in Europe, Africa, and Asia. Partial BKV DNA sequences (n=299) in these samples were determined and subjected to phylogenetic and single nucleotide polymorphism analysis to classify BKV isolates around the world. The validity of the classification was confirmed by analyses based on complete BKV DNA sequences. Subtype I was the major subtype throughout the studied regions, and subtype IV was prevalent only in Asia and Europe. Subtype-I subgroups showed close relationships to major geographical areas. It has recently been shown that JC virus (a human polyomavirus closely related to BKV) co-evolved with human populations, and the present study thus suggests that host-linked evolution is the general mode of polyomavirus evolution. Additionally, our results indicate certain unique aspects of the relationship between BKV and humans.

New insights into adaptive immunity in chronic neuroinflammation

Understanding the immune response in the central nervous system (CNS) is crucial for the development of new therapeutic concepts in chronic neuroinflammation, which differs considerably from other autoimmune diseases. Special immunologic properties of inflammatory processes in the CNS, which is often referred to as an immune privileged site, imply distinct features of CNS autoimmune disease in terms of disease initiation, perpetuation, and therapeutic accessibility. Furthermore, the CNS is a stress-sensitive organ with a low capacity for self-renewal and is highly prone to bystander damage caused by CNS inflammation. This leads to neuronal degeneration that contributes considerably to the phenotype of the disease. In this chapter, we discuss recent findings emphasizing the predominant role of the adaptive immune system in the pathogenesis of chronic neuroinflammation, that is, multiple sclerosis (MS) in patients and experimental autoimmune encephalomyelitis (EAE) in rodents. In addition, we report on efforts to translate these findings into clinical practice with the aim of developing selective treatment regimens.

The role of sialic acid in human polyomavirus infections

JC virus (JCV) and BK virus (BKV) are human polyomaviruses that infect approximately 85% of the population worldwide [1,2]. JCV is the underlying cause of the fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML), a condition resulting from JCV induced lytic destruction of myelin producing oligodendrocytes in the brain [3]. BKV infection of kidneys in renal transplant recipients results in a gradual loss of graft function known as polyomavirus associated nephropathy (PVN) [4]. Following the identification of these viruses as the etiological agents of disease, there has been greater interest in understanding the basic biology of these human pathogens [5,6]. Recent advances in the field have shown that viral entry of both JCV and BKV is dependent on the ability to interact with sialic acid. This review focuses on what is known about the human polyomaviruses and the role that sialic acid plays in determining viral tropism.

Polyomavirus nephropathy in native kidneys and renal allografts: an update on an escalating threat

Polyomavirus nephropathy, also termed BK-virus nephropathy (BKN) after the main causative agent, the polyoma-BK-virus strain, is a significant complication after kidney transplantation. BKN is the most common viral infection that affects renal allografts with a prevalence of 1-9% on average 8-13 months post surgery. It can also occur sporadically in native kidneys. Viral nephropathy is caused by the (re)activation of latent BK viruses that enter into a replicative cycle under sustained and intensive immunosuppression. Pure productive kidney infections with JC- and SV-40 polyomaviruses are exceptionally rare. BKN is morphologically defined by the presence of intranuclear viral inclusion bodies in epithelial cells and tubular injury, which is the morphological correlate for renal dysfunction. Renal disease can progress through different histologic stages (from early BKN stage A to late fibrotic stage C) that carry prognostic significance; disease stages B and C often result in chronic kidney (allograft) dysfunction and end-stage renal disease. The clinical goal is to diagnose viral nephropathy in disease stage A and to limit chronic renal injury. Strategies to recognize, classify, and manage BKN are critically discussed including ancillary techniques for risk assessment and patient monitoring: (i) urine cytology and the search for so-called 'decoy cells'; (ii) PCR analyses for viral load measurements in the plasma and urine; and (iii) negative staining urine electron microscopy to identify viral particles.

Identification of a genomic subgroup of BK polyomavirus spread in European populations

BK polyomavirus (BKV) is highly prevalent in the human population, infecting children without obvious symptoms and persisting in the kidney in a latent state. In immunosuppressed patients, BKV is reactivated and excreted in urine. BKV isolates worldwide are classified into four serologically distinct subtypes, I-IV, with subtype I being the most frequently detected. Furthermore, subtype I is subdivided into subgroups based on genomic variations. In this study, the distribution patterns of the subtypes and subgroups of BKV were compared among four patient populations with various immunosuppressive states and of various ethnic backgrounds: (A) Finnish renal-transplant recipients; (B) Irish/English haematopoietic stem-cell transplant recipients with and without haemorrhagic cystitis; (C) Japanese renal-transplant recipients; and (D) Japanese bone-marrow transplant recipients. The typing sequences (287 bp) of BKV in population A were determined in this study; those in populations B-D have been reported previously. These sequences were subjected to phylogenetic and single nucleotide polymorphism analyses. Based on the results of these analyses, the BKV isolates in the four patient populations were classified into subtypes and subgroups. The incidence of subtype IV varied significantly among patient populations. Furthermore, the incidence of subgroup Ib-2 within subtype I was high in populations A and B, whereas that of Ic was high in populations C and D (P<0.01). These results suggest that subgroup Ib-2 is widespread among Europeans, whereas Ic is unique to north-east Asians. Furthermore, a phylogenetic analysis based on complete BKV DNA sequences supported the hypothesis that there is geographical separation of European and Asian BKV strains.

New commercially available PCR and microplate hybridization assay for detection and differentiation of human polyomaviruses JC and BK in cerebrospinal fluid, serum, and urine samples

JC and BK human polyomaviruses (family Polyomaviridae) may cause severe neurological or urinary tract pathologies in immunocompromised hosts. In the present study, we evaluated a new commercially available PCR and microplate colorimetric hybridization assay for the standardized differential detection of JC virus (JCV) and BK virus (BKV) genomes in clinical samples. This JC/BK Consensus test was first evaluated by testing serial dilutions of JCV or BKV plasmid DNA standards and was then compared with an in-house reference PCR assay for the detection of JC and BK virus genomes in 70 cerebrospinal fluid (CSF) samples of patients with neurological disorders and in 75 serum or plasma samples and 125 urine samples of renal graft recipients. This new test allowed a limit of detection of 10 copies and 1 copy of JC and BK virus genomes, respectively, and was able to differentiate various levels of JCV, BKV, and mixed JCV and BKV DNA genomes in a single reaction tube. Our results showed 100% specificity and sensitivity for the JC/BK Consensus test with CSF samples. With serum or plasma samples, this test had a sensitivity and a specificity of 100% for both JCV and mixed JCV and BKV DNA detection and a sensitivity and a specificity of 100 and 97.8% for BKV DNA detection, respectively. With urine samples, the sensitivity and specificity were 100 and 96.6%, respectively, for JCV DNA detection; 100 and 89.4%, respectively, for BKV DNA detection; and 44.4 and 100%, respectively, for mixed JCV and BKV DNA detection. In conclusion, our data indicate that this new test, the JC/BK Consensus test, is valuable for the sensitive and specific differential detection of single JCV and BKV infections in CSF, serum or plasma, and urine samples. The use of this reliable PCR assay would improve the routine virological diagnosis as well as the clinical care of immunocompromised patients with polyomavirus-related pathologies.

Age-related urinary excretion of BK polyomavirus by nonimmunocompromised individuals

Two polyomaviruses, BK virus (BKV) and JC virus (JCV), are ubiquitous in the human population, generally infecting children asymptomatically and then persisting in renal tissue. It is generally thought that reactivation leads to productive infection for both viruses, with progeny shed in the urine. Several studies have shown that the rate of JC viruria increases with the age of the host, but a systematic approach to examine the shedding of BKV has not been developed. To elucidate the relationship between BK viruria and host age, we obtained urine from donors (healthy volunteers or nonimmunocompromised patients) who were divided into nine age groups, each containing 50 members. A high-sensitivity PCR was used to detect BKV and JCV DNA from urinary samples, and the specificity of amplification was confirmed by sequencing or restriction analysis of the amplified fragments. The rate of BK viruria was relatively low in subjects aged <30 years but gradually increased with age in subjects aged > or =30 years. However, BK viruria was less frequent than JC viruria in adults. The detected BKV isolates were classified into subtypes, and detection rates for individual subtypes were compared among age groups; this analysis showed that viruria of subtypes I (the most prevalent subtype) and IV (the second most prevalent subtype) occurred more frequently in older subjects. Therefore, our results reveal new aspects of BK viruria in nonimmunocompromised individuals.

Inhibitory effect of gamma interferon on BK virus gene expression and replication

BK virus (BKV) is widely accepted to be the causative agent of polyomavirus nephropathy. In immunocompromised individuals, especially kidney transplant recipients, BKV can replicate in kidney epithelial cells, causing loss of renal function and eventual destruction of the graft. Advances in immunosuppressive therapies may be partially responsible for the increasing incidence of polyomavirus nephropathy among transplant recipients by more effectively eliminating components of the immune system, such as gamma interferon (IFN-gamma)-producing lymphocytes, that keep BKV infections at a subclinical level. In this study, we investigated the role of IFN-gamma in regulating lytic infection by BKV. Treatment with IFN-gamma inhibited the expression of the viral early protein large tumor antigen (TAg) and the late protein VP1 in a dose-dependent manner. We detected 1.6- and 12-fold reductions in TAg transcripts at 48 and 96 h postinfection, respectively, with 250 U/ml IFN-gamma, suggesting that IFN-gamma-mediated inhibition occurs at the level of transcription. Furthermore, IFN-gamma inhibited the level of viral progeny production as much as 50-fold at a multiplicity of infection (MOI) of 0.5 and 80-fold at an MOI of 0.1. The inhibitory effects of IFN-gamma were similar for three different strains of BKV examined. These results indicate an important role for IFN-gamma in regulating BKV lytic infection.

Inhibitory effect of gamma interferon on BK virus gene expression and replication

BK virus (BKV) is widely accepted to be the causative agent of polyomavirus nephropathy. In immunocompromised individuals, especially kidney transplant recipients, BKV can replicate in kidney epithelial cells, causing loss of renal function and eventual destruction of the graft. Advances in immunosuppressive therapies may be partially responsible for the increasing incidence of polyomavirus nephropathy among transplant recipients by more effectively eliminating components of the immune system, such as gamma interferon (IFN-gamma)-producing lymphocytes, that keep BKV infections at a subclinical level. In this study, we investigated the role of IFN-gamma in regulating lytic infection by BKV. Treatment with IFN-gamma inhibited the expression of the viral early protein large tumor antigen (TAg) and the late protein VP1 in a dose-dependent manner. We detected 1.6- and 12-fold reductions in TAg transcripts at 48 and 96 h postinfection, respectively, with 250 U/ml IFN-gamma, suggesting that IFN-gamma-mediated inhibition occurs at the level of transcription. Furthermore, IFN-gamma inhibited the level of viral progeny production as much as 50-fold at a multiplicity of infection (MOI) of 0.5 and 80-fold at an MOI of 0.1. The inhibitory effects of IFN-gamma were similar for three different strains of BKV examined. These results indicate an important role for IFN-gamma in regulating BKV lytic infection.

Phylogenetic analysis of major African genotype (Af2) of JC virus: Implications for origin and dispersals of modern Africans

Both mtDNA and the Y chromosome have been used to investigate how modern humans dispersed within and out of Africa. This issue can also be studied using the JC virus (JCV) genotype, a novel marker with which to trace human migrations. Africa is mainly occupied by two genotypes of JCV, designated Af1 and Af2. Af1 is localized to central/western Africa, while Af2 is spread throughout Africa and in neighboring areas of Asia and Europe. It was recently suggested that Af1 represents the ancestral type of JCV, which agrees with the African origin of modern humans. To better understand the origin of modern Africans, we examined the phylogenetic relationships among Af2 isolates worldwide. A neighbor-joining phylogenetic tree was constructed based on the complete JCV DNA sequences of 51 Af2 isolates from Africa and neighboring areas. According to the resultant tree, Af2 isolates diverged into two major clusters, designated Af2-a and -b, with high bootstrap probabilities. Af2-a contained isolates mainly from South Africa, while Af2-b contained those from the other parts of Africa and neighboring regions of Asia and Europe. These findings suggest that Af2-carrying Africans diverged into two groups, one carrying Af2-a and the other carrying Af2-b; and that the former moved to southern Africa, while the latter dispersed throughout Africa and to neighboring regions of Asia and Europe. The present findings are discussed with reference to relevant findings in genetic and linguistic studies.

Human demyelinating disease and the polyomavirus JCV

Many human neurological diseases involve demyelination of the central and/or peripheral nervous systems. These include the hereditary leukodystrophies--which have a genetic basis; multiple sclerosis (MS)--where the underlying cause of demyelination remains unknown; and progressive multifocal leukoencephalopathy (PML)--where the etiology is well-established as being viral. The human neurotropic polyomavirus--JC virus (JCV)--is the etiologic agent of PML, a fatal demyelinating disease of the central nervous system that occurs mainly in immunosuppressed patients, especially those with HIV/AIDS. JCV belongs to the polyomavirus family of tumor viruses that are characterized by non-enveloped icosahedral capsids containing small, circular, double-stranded DNA genomes. Serological studies have shown that JCV is widespread throughout the human population, but infections are usually restricted by the immune system, particularly cell-mediated immunity, causing the virus to enter a latent phase. An important corollary of this is that situations of severe immunosuppression may permit JCV to replicate and are thus a risk factor for PML.

Subtype I BK polyomavirus strains grow more efficiently in human renal epithelial cells than subtype IV strains

BK polyomavirus (BKPyV) is ubiquitous in human populations, infecting children without obvious symptoms and persisting in the kidney. BKPyV isolates have been classified into four subtypes (I-IV) using either serological or genotyping methods. In general, subtype I occurs most frequently, followed by subtype IV, with subtypes II and III rarely detected. As differences in growth capacity in human cells possibly determine the proportion of the four subtypes of BKPyV in human populations, here the growth properties of representative BKPyV strains classified as subtype I or IV in renal proximal tubule epithelial cells (HPTE cells) of human origin were analysed. HPTE cells were transfected with four and three full-length BKPyV DNAs belonging to subtypes I and IV, respectively, and cultivated in growth medium. Virus replication, detected using the haemagglutination assay, was observed in all HPTE cells transfected with subtype I BKPyV DNAs, whereas it was markedly delayed or not detected in those transfected with subtype IV BKPyV DNAs. It was confirmed that the transfected viral DNAs induced virus replication in HPTE cells. Furthermore, it was found that BKPyVs with archetypal transcriptional control regions replicated in HPTE cells, with only the occasional emergence of variants carrying rearranged transcriptional control regions. Essentially the same results as described above were obtained with renal epithelial cells derived from whole kidney. Thus, it was concluded that subtype I BKPyV replicates more efficiently than subtype IV BKPyV in human renal epithelial cells, supporting the hypothesis that growth capacity in human cells is related to the proportion of BKPyV subtypes in human populations.

Evolution of BK virus based on complete genome data

The human polyomavirus BK virus (BKV) is ubiquitous in humans, infecting children asymptomatically. BKV is the only primate polyomavirus that has subtypes (I-IV) distinguishable by immunological reactivity. Nucleotide (nt) variations in a major capsid protein (VP1) gene region (designated the epitope region), probably responsible for antigenic diversity, have been used to classify BKV isolates into subtypes. Here, with all the protein-encoding gene sequences, we attempted to elucidate the evolutionary relationships among 28 BKV isolates belonging to subtypes I, III, and IV (no isolate belonging to subtype II, a minor one, was included). First, using the GTR + Gamma + I model, maximum likelihood trees were reconstructed for individual viral genes as well as for concatenated viral genes. On the resultant trees, the 28 BKV isolates were consistently divided into three clades corresponding to subtypes I, III, and IV, although bootstrap probabilities are not always high. Then we used more sophisticated likelihood models, one of which takes account of codon structure, to elucidate the phylogenetic relationships among BKV subtypes, but the phylogeny of the deep branchings remained ambiguous. Furthermore, the possibility of positive selection in the evolution of BKV was examined using the nonsynonymous/synonymous rate ratio as a measure of selection. An analysis based on entire genes could not detect any strong evidence for positive selection, but that based on the epitope region identified a few sites potentially under positive selection (these sites were among those showing subtype linked polymorphisms).

Subtype IV of the BK polyomavirus is prevalent in East Asia

BK polyomavirus (BKV) is ubiquitous in human populations, infecting children asymptomatically and then persisting in the kidney. Using either serological or genotyping methods, BKV isolates have been classified into four subtypes (I-IV), with subtype I mainly detected in all countries studied so far. To elucidate the subtype of BKV prevalent in East Asia, we examined BKV-positive urine samples collected from immunocompetent elderly patients in Mongolia, Northeast China, Northwest China, Southeast China, Southwest China, Vietnam and Japan. The 287-bp typing region of the viral genome in each of these samples was PCR-amplified and sequenced, and a phylogenetic tree was constructed. According to the tree, BKV isolates in East Asia were unambiguously classified into subtype I or IV (subtypes II and III were not detected). In Japan, subtype I was mainly detected and subtype IV was rare, whereas in the other regions subtype IV was detected frequently, at rates ranging from 24 to 100%. Thus, East Asia (excluding Japan) is a region in which subtype-IV BKV is prevalent, a finding that requires the view of the geographic distribution of BKV subtypes to be revised. Furthermore, we present evidence that the immunological states of urine donors do not affect the pattern of BKV subtypes.

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.

Unique BK virus non-coding control region (NCCR) variants in hematopoietic stem cell transplant recipients with and without hemorrhagic cystitis

Hematopoietic stem cell transplant recipients frequently develop BK virus (BKV)-associated hemorrhagic cystitis, which coincides with BK viruria. However, the precise role of BKV in the etiology of hemorrhagic cystitis in hematopoietic stem cell transplant recipients remains unclear, since approximately 50% of all such adult transplant recipients excrete BKV, yet do not develop this clinical condition. In the present study, BKV were analyzed to determine if mutations in the non-coding control region (NCCR), and specific BKV sub-types defined by sequence analysis of major capsid protein VP1, were associated with development of hemorrhagic cystitis in hematopoietic stem cell transplant recipients. The regions encoding VP1 and NCCRs of BKV in urine samples collected from 15 hematopoietic stem cell transplant recipients with hemorrhagic cystitis and 20 without this illness were amplified and sequenced. Sequence variations in the NCCRs of BKV were identified in urine samples from those with and without hemorrhagic cystitis. Furthermore, five unique sequence variations within transcription factor binding sites in the canonical NCCR, O-P-Q-R-S, were identified, representing new BKV variants from a population of cloned quasi-species obtained from patients with and without hemorrhagic cystitis. Thirty-five BKV VP1 sequences were analyzed by phylogenetic analysis but no specific BKV sub-type was associated with hemorrhagic cystitis. Five previously unrecognized naturally occurring variants of the BKV are described which involve amplifications, deletions, and rearrangements of the archetypal BKV NCCRs in individuals with and without hemorrhagic cystitis. Architectural rearrangements in the NCCRs of BKV did not appear to be a prerequisite for development of hemorrhagic cystitis in hematopoietic stem cell transplant recipients.

[New trends in progressive multifocal leukoencephalopathy]

Infection by Polyomavirus JC is a model of chronic active viral infection, closely controlled by the immune system. Progressive multifocal leucoencephalopathy (PML) is a deadly demyelinating disease of the central nervous system, consecutive to the lytic infection of oligodendrocytes by JC virus. Reactivation of JC virus occurs only in the setting of severe cellular immune deficiency. During the last 25 years, the incidence of PML has significantly increased related to the AIDS pandemic and, more recently, to the growing use of immunosuppressive drugs. There is no specific antiviral treatment for PML. Nevertheless, the availability of highly active antiretroviral therapy has changed the clinical course of PML in HIV-infected individuals. One-year mortality has decreased from 90 percent to approximately 50 percent as a result of reconstitution of the immune system. Recent advances in JC virus biology give new perspectives to the pathogenesis of PML. New trends in the understanding of the cellular immune response against the JC virus have direct implications for patient management and may lead to develop future strategy of immunotherapies for PML.

Viral induced demyelination

Viral induced demyelination, in both humans and rodent models, has provided unique insights into the cell biology of oligodendroglia, their complex cell-cell interactions and mechanisms of myelin destruction. They illustrate mechanisms of viral persistence, including latent infections in which no infectious virus is readily evident, virus reactivation and viral-induced tissue damage. These studies have also provided excellent paradigms to study the interactions between the immune system and the central nervous system (CNS). Although of interest in their own right, an understanding of the diverse mechanisms used by viruses to induce demyelination may shed light into the etiology and pathogenesis of the common demyelinating disorder multiple sclerosis (MS). This notion is supported by the persistent view that a viral infection acquired during adolescence might initiate MS after a long period of quiescence. Demyelination in both humans and rodents can be initiated by infection with a diverse group of enveloped and non-enveloped RNA and DNA viruses (Table 1). The mechanisms that ultimately result in the loss of CNS myelin appear to be equally diverse as the etiological agents capable of causing diseases which result in demyelination. Although demyelination can be a secondary result of axonal loss, in many examples of viral induced demyelination, myelin loss is primary and associated with axonal sparing. This suggests that demyelination induced by viral infections can result from: 1) a direct viral infection of oligodendroglia resulting in cell death with degeneration of myelin and its subsequent removal; 2) a persistent viral infection, in the presence or absence of infectious virus, resulting in the loss of normal cellular homeostasis and subsequent oligodendroglial death; 3) a vigorous virus-specific inflammatory response wherein the virus replicates in a cell type other than oligodendroglia, but cytokines and other immune mediators directly damage the oligodendroglia or the myelin sheath; or 4) infection initiates activation of an immune response specific for either oligodendroglia or myelin components. Virus-induced inflammation may be associated with the processing of myelin or oligodendroglial components and their presentation to the host's own T cell compartment. Alternatively, antigenic epitopes derived from the viral proteins may exhibit sufficient homology to host components that the immune response to the virus activates autoreactive T cells, i.e. molecular mimicry. Although it is not clear that each of these potential mechanisms participates in the pathogenesis of human demyelinating disease, analysis of the diverse demyelinating viral infections of both humans and rodents provides examples of many of these potential mechanisms.

Cross-reactive CTL recognizing two HLA-A*02-restricted epitopes within the BK virus and JC virus VP1 polypeptides are frequent in immunocompetent individuals

Two HLA-A*02-restricted epitopes have been identified within the VP1 polypeptide of a human polyomavirus, BK virus, which is associated with polyomavirus-associated nephropathy in kidney transplant patients. Immunization of transgenic mice with recombinant modified vaccinia Ankara expressing BKV VP1 (rMVA-BKV VP1) elicited functional CTL populations recognizing the sequences LLMWEAVTV (amino acids residues 108-116, BKV VP1p108) and AITEVECFL (residues 44-52, BKV VP1p44) and cross-reactive to the previously described JC virus VP1 homologs. Flow-based analyses of PBMC from a panel of thirty healthy HLA-A*02 human volunteers indicated that the majority of these subjects harbored functional CTL populations recognizing the BKV epitopes and cross-reactive with the JCV homologs. CTL recognizing the JCV VP1p100 and JCV VP1p36 epitopes have previously been associated with prolonged survival in progressive multifocal leukoencephalopathy patients. These findings suggest that infection with BKV or JCV could potentially induce cross-protective T-cell immunity against diseases associated with these viruses.

Deciphering host migrations and origins by means of their microbes

Mitochondrial DNA and microsatellite sequences are powerful genetic markers for inferring the genealogy and the population genetic structure of animals but they have only limited resolution for organisms that display low genetic variability due to recent strong bottlenecks. An alternative source of data for deciphering migrations and origins in genetically uniform hosts can be provided by some of their microbes, if their evolutionary history correlates closely with that of the host. In this review, we first discuss how a variety of viruses, and the bacterium Helicobacter pylori, can be used as genetic tracers for one of the most intensively studied species, Homo sapiens. Then, we review statistical problems and limitations that affect the calculation of particular population genetic parameters for these microbes, such as mutation rates, with particular emphasis on the effects of recombination, selection and mode of transmission. Finally, we extend the discussion to other host-parasite systems and advocate the adoption of an integrative approach to both sampling and analysis.

Intermediate-dose cidofovir without probenecid in the treatment of BK virus allograft nephropathy

BK virus allograft nephropathy (BKVAN) is a rising complication in kidney transplant recipients. Reducing immunosuppression has been the initial form of therapy in most cases, but is not always associated with improvement in graft function. Anti-viral therapy with low-dose cidofovir (0.25-0.42 mg/kg/dose) has been used successfully in some patients, but dose-related nephrotoxicity has limited its use. We present our experience with 3 kidney transplant recipients diagnosed with BKVAN who received intermediate-dose cidofovir (0.75-1.0 mg/kg/dose) without probenecid, and without concomitant nephrotoxicity. Three female patients, ages 8, 19 and 20 yr, presented with elevated serum creatinine (SCr) values, BK virus stain positive on renal biopsy and high plasma BK viral loads. As a result of viral loads being >2 million copies/ml in two patients and a lack of response to reduction in immunosuppression in the third, we initiated therapy with low-dose cidofovir. Because of persistent positive BK stain and positive plasma viral load, we then administered intermediate-dose cidofovir, without probenecid, for several subsequent doses (seven to 15 infusions till date). All patients tolerated the intermediate-dose cidofovir with no significant rise in SCr during the course of the infusions. The most recent SCr values in all three patients were improved from those at the initial diagnosis of BKVAN. All three patients showed a marked drop in BK viral loads when on intermediate-dose cidofovir, with complete clearing of viremia in two patients. In our experience, intermediate-dose cidofovir without probenecid, used judiciously, is not associated with additional nephrotoxicity and may provide an additional alternative for treatment.

An N-linked glycoprotein with alpha(2,3)-linked sialic acid is a receptor for BK virus

BK virus (BKV) is a common human polyomavirus infecting >80% of the population worldwide. Infection with BKV is asymptomatic, but reactivation in renal transplant recipients can lead to polyomavirus-associated nephropathy. In this report, we show that enzymatic removal of alpha(2,3)-linked sialic acid from cells inhibited BKV infection. Reconstitution of asialo cells with alpha(2,3)-specific sialyltransferase restored susceptibility to infection. Inhibition of N-linked glycosylation with tunicamycin reduced infection, but inhibition of O-linked glycosylation did not. An O-linked-specific alpha(2,3)-sialyltransferase was unable to restore infection in asialo cells. Taken together, these data indicate that an N-linked glycoprotein containing alpha(2,3)-linked sialic acid is a critical component of the cellular receptor for BKV.

Analysis of the transcriptional control region of JC polyomavirus in cerebrospinal fluid from HIV-negative patients with progressive multifocal leucoencephalopathy

The human polyomavirus JC (JCV) is the causative agent of progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system (CNS). JCV has a hyper-variable non-coding transcriptional control region (TCR), which contains the origin of replication and the promoters of viral transcription and replication. The archetype form of TCR-JCV is frequently found in the urine and kidneys of healthy and immunocompromised subjects. However, the rearranged forms, possibly generated by deletion and duplication of segments of the archetype sequence, are found in the peripheral blood, cerebrospinal fluid (CSF), and brain of PML patients. Most experience on this setting has come from the human immunodeficiency virus (HIV) pandemic. Little has been described on the JCV-TCR sequences from PML-HIV-negative patients affected by other immunosuppressive disorders. The aim of this study was to analyze the JCV-TCR detected in CSF samples from 12 HIV-negative immunosuppressed patients suffering from PML and to investigate the possible role of genomic organization in the different incidences of PML in HIV-positive and HIV-negative patients. The results confirm that the JCV-TCR rearrangements play a crucial role in the development of PML, although they do not account for the higher frequency of the disease in HIV infection. These data support the hypothesis that, independently of the rearrangement patterns of JCV-TCR, the direct action of HIV together with other as yet unidentified cellular determinants can be a key to explaining the high rate of PML in HIV infection with respect to other underlying immunosuppressive conditions.

Rare cause of ureteral obstruction

This report presents bilateral ureteral obstruction due to possible ureteritis in a bone marrow transplant patient with resurgence of BK virus after hemorrhagic cystitis. This is believed to be the first description of this type of ureteral obstruction. The presented case includes the management plan.

Specific and quantitative detection of human polyomaviruses BKV, JCV, and SV40 by real time PCR

BACKGROUND

The polyomaviruses that infect humans, BK virus (BKV), JC virus (JCV), and simian virus 40 (SV40), typically establish subclinical persistent infections. However, reactivation of these viruses in immunocompromised hosts is associated with renal nephropathy and hemorrhagic cystitis (HC) caused by BKV and with progressive multifocal leukoencephalopathy (PML) caused by JCV. Additionally, SV40 is associated with several types of human cancers including primary brain and bone cancers, mesotheliomas, and non-Hodgkin's lymphoma. Advancements in detection of these viruses may contribute to improved diagnosis and treatment of affected patients.

OBJECTIVE

To develop sensitive and specific real time quantitative polymerase chain reaction (RQ-PCR) assays for the detection of T-antigen DNA sequences of the human polyomaviruses BKV, JCV, and SV40 using the ABI Prism 7000 Sequence Detection System.

STUDY DESIGN

Assays for absolute quantification of the viral T-ag sequences were designed and the sensitivity and specificity were evaluated. A quantitative assay to measure the single copy human RNAse P gene was also developed and evaluated in order to normalize viral gene copy numbers to cell numbers.

RESULTS

Quantification of the target genes is sensitive and specific over a 7 log dynamic range. Ten copies each of the viral and cellular genes are reproducibly and accurately detected. The sensitivity of detection of the RQ-PCR assays is increased 10- to 100-fold compared to conventional PCR and agarose gel protocols. The primers and probes used to detect the viral genes are specific for each virus and there is no cross reactivity within the dynamic range of the standard dilutions. The sensitivity of detection for these assays is not reduced in human cellular extracts; however, different DNA extraction protocols may affect quantification.

CONCLUSION

These assays provide a technique for rapid and specific quantification of polyomavirus genomes per cell in human samples.

Polyomavirus DNA and RNA detection in renal allograft biopsies: results from a European multicenter study

Polyomavirus mediated nephropathy is an increasingly recognized complication in renal transplant recipients. In all, 362 renal biopsies collected from 15 European transplant centers were analyzed for presence of Polyomavirus nucleic acid (BK virus [BKV] and JC virus [JCV]). We evaluated 302 biopsies of patients with renal allograft dysfunction, including three with known BKV allograft nephropathy (BKVAN), and 60 native kidney biopsies. BKV DNA was detected in 8 of the 302 (2.6 %) biopsies obtained for transplant dysfunction, but in none of the controls. BKV RNA, indicating active viral replication, was found in all BKV DNA positive biopsies available for mRNA expression studies. Retrospective immunohistochemical staining was positive for SV40 large T antigen in all seven evaluated biopsies. BKV DNA and RNA were detected in biopsy tissues from patients with inconspicuous light microscopy for BKVAN. Further studies will evaluate the potential of intrarenal viral BKV RNA as an early predictor for BKVAN.

A comparative study of BK and JC virus infections in organ transplant recipients

JC virus (JCV) rarely causes kidney disease, whereas BK virus (BKV) is a known cause of viral nephropathy. Existing studies on prevalence of JCV in healthy and transplanted subjects have reported only qualitative detection of viral DNA. We used quantitative PCR (qPCR) to assess JC viral load in transplant recipients and non-immunosuppressed controls, and compared JCV loads to BKV loads. JC viruria was seen in 8/23 (34.7%) controls, 23/103 (22.3%) renal, and 10/44 (22.7%) liver transplant patients. No patient developed JC viremia. BK viruria was seen in 2/23 (8.7%) controls, 36/103 (34.9%) renal, and 7/44 (15.9%) liver transplant patients. BK viremia was seen only in the kidney (8/103 = 7.7%) patients. The mean BKV urinary load was higher in kidney compared to liver patients and controls (4.22E + 07 vs. 2.88E + 05 vs. 4.39E + 02 copies/ml), whereas JC viral load was similar for all three patient groups (1.55E + 06 vs. 2.66E + 06 vs. 2.13E + 06 copies/ml). JCV viral loads were surprisingly high in all patient categories studied, but did not result in viremia or viral nephropathy. Although both BKV and JCV are widely latent in patients accepted for transplantation, concurrent reactivation of both viruses was infrequent. BKV viremia was seen in kidney but not liver recipients. The mechanisms underlying these notable phenomena remain to be investigated.

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.

BKV infection and hemorrhagic cystitis after allogeneic bone marrow transplant

Hemorrhagic cystitis (HC) is a well-known complication after allogeneic bone marrow transplant (BMT) and can be related to adenovirus or human polyomavirus BK (BKV) infections. In this study a group of 20 patients after allogeneic BMT has been examined. BMT urine samples were analysed for the presence of Adenovirus and BKV DNAby means of polymerase chain reaction (PCR). 5/20 BMT patients developed HC after BMT. The presence of BKV DNA in urine samples was evident in 3/15 patients without HC and in 5/5 patients with HC. In 2/5 HC-patients the BKV DNA was not found after therapy with Cidofovir and Ribavirin. The search for adenovirus DNA in all samples was negative. The analysis of BKV non-coding control region (NCCR) isolated from urine samples revealed a structure very similar to the archetype in all samples. The RFLP (Restriction Fragment Length Polymorphism assay) showed the presence of BKV subtypes I and IV, with the prevalence of subtype I (4/5). This study supports the hypothesis that HC is mainly related to BKV rather than to adenovirus infection in BMT patients. Moreover, since BKV subtype I was predominant, it is reasonable to hypothesize that a specific BKV subtype could be associated with the development of HC.

Cross-reactivity of T lymphocytes recognizing a human cytotoxic T-lymphocyte epitope within BK and JC virus VP1 polypeptides

A transgenic mouse model was used to identify an HLA-A*02-restricted epitope within the VP1 polypeptide of a human polyomavirus, BK virus (BKV), which is associated with polyomavirus-associated nephropathy in kidney transplant patients. Peptide stimulation of splenocytes from mice immunized with recombinant modified vaccinia virus Ankara expressing BKV VP1 resulted in expansion of cytotoxic T lymphocytes (CTLs) recognizing the sequence LLMWEAVTV corresponding to amino acid residues 108 to 116 (BKV VP1p108). These effector T-cell populations represented functional CTLs as assessed by cytotoxicity and cytokine production and were cross-reactive against antigen-presenting cells pulsed with a peptide corresponding to the previously described JC virus (JCV) VP1 homolog sequence ILMWEAVTL (JCV VP1p100) (I. J. Koralnik et al., J. Immunol. 168:499-504, 2002). A panel of 10 healthy HLA-A*02 human volunteers and two kidney transplant recipients were screened for T-cell immunity to this BK virus VP1 epitope by in vitro stimulation of their peripheral blood mononuclear cells (PBMC) with the BKV VP1p108 peptide, followed by tetramer labeling combined with simultaneous assays to detect intracellular cytokine production and degranulation. PBMC from 4/10 subjects harbored CTL populations that recognized both the BKV VP1p108 and the JCV VP1p100 peptides with comparable efficiencies as measured by tetramer binding, gamma interferon production, and degranulation. CTL responses to the JCV VP1p100 epitope have been associated with prolonged survival in progressive multifocal leukoencephalopathy patients (R. A. Du Pasquier et al., Brain 127:1970-1978, 2004; I. J. Koralnik et al., J. Immunol. 168:499-504, 2002). Given that both human polyomaviruses are resident in a high proportion of healthy individuals and that coinfection occurs (W. A. Knowles et al., J. Med. Virol. 71:115-123, 2003), our findings suggest a reinterpretation of this protective T-cell immunity, suggesting that the same VP1 epitope is recognized in HLA-A*02 persons in response to either BK or JC virus infection.

AIDS-associated progressive multifocal leukoencephalopathy : current management strategies

Progressive multifocal leukoencephalopathy (PML) is a rare, opportunistic infection of the CNS by the ubiquitous JC virus (JCV). PML is only seen in the context of severe and prolonged immunosuppression, a phenomenon now frequently encountered since the AIDS pandemic. PML is characterised by progressive lysis of oligodendrocytes with demyelination. A rapid clinical course ensues with focal neurological deficits and a median time to death of 3.5 months without treatment. Prior to highly active antiretroviral therapy (HAART), there was no effective therapy. Since the advent of HAART, the prognosis for PML has much improved; however, a significant number of patients appear unresponsive to antiretrovirals and some worsen because of the development of immune reconstitution disease. A better understanding of the biology of JCV and its interactions with host cells is leading to new anti-JCV-specific agents that await evaluation in randomised, controlled trials. Improved diagnostic tools and the possibility of immunotherapy and gene therapy are further advancing the field.

Genetic diversity of JC virus in the Saami and the Finns: implications for their population history

The JC virus (JCV) genotyping method was used to gain insights into the population history of the Saami and the Finns, both speaking Finno-Ugric languages and living in close geographic proximity. Urine samples from Saami and Finns, collected in northern and southern Finland, respectively, were used to amplify a 610-bp JCV-DNA region containing abundant type-specific mutations. Based on restriction site polymorphisms in the amplified fragments, we classified JCV isolates into one of the three superclusters of JCV, type A, B, or C. All 15 Saami isolates analyzed and 41 of 43 Finnish isolates analyzed were classified as type A, the European type, and two samples from Finns were classified as type B, the African/Asian type. We then amplified and sequenced a 583-bp JCV-DNA region from the type A isolates of Saami and Finns. According to type-determining nucleotides within the region, we classified type A isolates into EU-a1, -a2, or -b. Most type A isolates from Saami were classified as EU-a1, while type A isolates from Finns were distributed among EU-a1, EU-a2, and EU-b. This trend in the JCV-genotype distribution was statistically significant. On a phylogenetic tree based on complete sequences, most of the type A isolates from Saami were clustered in a single clade within EU-a1, while those from Finns were distributed throughout EU-a1, EU-a2, and EU-b. These findings are discussed in the context of the population history of the Saami and the Finns. This study provides new complete JCV DNA sequences derived from populations of anthropological interest.

Application of fibrin glue to damaged bladder mucosa in a case of BK viral hemorrhagic cystitis

BK virus is a common cause of severe hemorrhagic cystitis refractory to standard treatment. We describe a technique to achieve hemostasis after failed conservative therapy using fibrin glue applied suprapubically while visualizing and insufflating the bladder through a cystoscope. Long-term hemostasis was achieved using this novel procedure.

Detection of JC virus DNA sequences in colorectal cancers in Japan

JC virus (JCV), a ubiquitous polyoma virus that commonly infects humans, was first identified as the etiologic agent for the fetal demyelinating disease, progressive multifocal leukoencephalopathy. Recently, a number of reports have documented detection of JCV in samples derived from several types of neural as well as non-neural human tumors. It has been suggested that oncogenicity of JCV depends on a T antigen having a strict structural homology to the T antigen of simian virus 40. To clarify whether JCV might have a potential role with regard to colorectal cancers, we investigated the presence of its genome in a series of cases along with colorectal adenomas and normal colonic mucosa, targeting T antigen, VP and agnoprotein by nested polymerase chain reaction and Southern blotting and T antigen by immunohistochemistry. While VP and agnoprotein were not found in any of the samples examined, T antigen was detected in 6 of 23 colorectal cancers (26.1%) and 1 of 21 adenomas (4.8%), but none of 20 samples of normal colonic mucosa. No clear and diffuse staining with anti-T-antigen antibodies (1:100) could be detected, and there was no correlation with CD20-positive cells, which might have indicated JCV latent infection of B lymphocytes. Presence of T antigen did not influence clinicopathological variables, including survival. In one colonic cancer case positive for T antigen together with lymph node metastasis, DNA extracted from cancer cells in the lymph node revealed no detection of T antigen. Our results are in the intermediate position between the high T antigen rate (81%) in one report and the lack of it (0%) in another focused on colon cancers. It was concluded that T antigen might be integrated in cancer cells in approximately one fourth of Japanese colon cancer cases without clear and diffuse expression of the protein, suggesting a possible role in oncogenesis which might involve a hit-and-run mechanism.

New sequence polymorphisms in the outer loops of the JC polyomavirus major capsid protein (VP1) possibly associated with progressive multifocal leukoencephalopathy

JC polyomavirus(JCPyV) causes progressive multifocal leukoencephalopathy (PML) in patients with decreased immune competence. To elucidate genetic changes in JCPyV associated with the pathogenesis of PML, multiple complete JCPyV DNA clones originating from the brains of three PML cases were established and sequenced. Although unique rearranged control regions occurred in all clones, a low level of nucleotide variation was also found in the coding region. In each case, a parental coding sequence was identified, from which variant coding sequences with nucleotide substitutions would have been generated. A comparison between the parental and variant coding sequences demonstrated that all 12 detected nucleotide substitutions gave rise to amino acid changes. Interestingly, seven of these changes were located in the surface loops of the major capsid protein (VP1). Finally, 16 reported VP1 sequences of PML-type JCPyV (i.e. derived from the brain or cerebrospinal fluid of PML patients) were compared with their genotypic prototypes, generated as consensus sequences of representative archetypal isolates belonging to the same genotypes; 13 VP1 proteins had amino acid changes in the surface loops. In contrast, VP1 proteins from isolates from the urine of immunocompetent and immunosuppressed patients rarely underwent mutations in the VP1 loops. The present findings suggest that PML-type JCPyV frequently undergoes amino acid substitutions in the VP1 loops. These polymorphisms should serve as a new marker for the identification of JCPyV isolates associated with PML. The biological significance of these mutations, however, remains unclear.

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.

Kidney and urinary tract polyomavirus infection and distribution: molecular biology investigation of 10 consecutive autopsies

CONTEXT

Distinct human polyomavirus genotypes cause different diseases in patients with renal transplants: BK virus (BKV) causes tubulointerstitial nephritis and ureteral stenosis, whereas both JC virus (JCV) and BKV are responsible for hemorrhagic cystitis. These findings could result from a selective infection of kidney and urinary tract segments by JCV or BKV.

OBJECTIVE

To verify this hypothesis, 10 complete, unselected, consecutive autopsies from 9 immunocompetent patients and 1 patient affected by acquired immunodeficiency syndrome were investigated.

DESIGN

Samples from kidneys (n = 80), renal pelvis (n = 20), ureter (n = 40), and urinary bladder (n = 30) obtained from 10 consecutive autopsies were investigated by means of multiplex nested polymerase chain reaction to detect polyomavirus DNA and to distinguish different species of the Polyomavirus genus. In situ hybridization and immunohistochemistry were also carried out to define the viral status of the infected tissues.

RESULTS

Polyomavirus DNA was detected in all of the subjects (positive samples ranging from 2 to 7 samples), for a total of 43 of 170 samples (25.3%), distributed as follows: urinary bladder (10/30, 33%), renal pelvis (6/20, 30%), ureter (10/40, 25%), and kidney tissue (17/80, 21%). We found that JCV was most frequently detected overall (23/43 samples, 53.5%) and was also detected most frequently within the kidney (8/17 positive samples, 47%), the renal pelvis (5/6 positive samples, 70%), and the ureter (7/10 positive samples, 70%), whereas BKV was found in 14 samples (32.5%), and it was the prevailing genotype in urinary bladder (6/10 positive samples, 60%). Coinfection of BKV-JCV was found in 6 samples (14%). Immunohistochemistry and in situ hybridization returned negative results.

CONCLUSIONS

The viruses JCV and BKV latently persist randomly in kidney and urinary tract. Distinct diseases induced by them could be related more closely to molecular viral rearrangements than to the topographic distribution of latent viruses.

JC virus genotyping using formalin-fixed, paraffin-embedded renal tissues

Recently genotyping of JC virus (JCV) DNA in renal tissue was reported to be useful to identify the geographic origin of unidentified cadavers. In the above study, autopsied tissue samples without storage or stored in a frozen state were used. This study examined JCV DNA sequence modifications caused by formalin-fixation, in an attempt to elucidate whether formalin-fixed, paraffin-embedded tissue samples can also be used to determine the genotypes of JCV DNA in the kidney. In four cases, a 610 bp typing region of the JCV genome was PCR-amplified from renal tissues stored for 1 year in three different states: frozen at -80 degrees C [Amaker, B.H., Chandler, F.W., Huey, L.O., Colwell, R.M., 1997. Molecular detection of JC virus in embalmed, formalin-fixed, paraffin-embedded brain tissue. J. Forensic Sci., 1157-1159], formalin-fixed, paraffin-embedded [Ault, G.S., Stoner, G.L., 1992. Two major types of JC virus defined in progressive multifocal leukoencephalopathy brain by early and late coding region DNA sequences. J. Gen. Virol. 73, 2669-2678], and soaked in 5% formalin [Baksh, F.K., Finkelstein, S.D., Swalskey, P.A., Stoner, G.L., Ryschkewitsch, C.F., Randhawa, P.R., 2001. Molecular genotyping of BK and JC virus in human polyomavirus-associated interstitial nephritis after renal transplantation. Am. J. Kidney Dis. 38 (2), 354-365]. The amplified fragments were cloned, and the resultant clones were sequenced. In frozen samples, single sequences ('original' sequences) were detected in all cases. In formalin-fixed, paraffin-embedded samples, not only the original sequences but also those with 1-6 base substitutions were detected. From formalin-soaked samples, the original sequences and those with 1-5 and 10-13 substitutions were detected. The genotyping of JCV DNA was not hampered by the presence of 1-6 substitutions, but a shift in JCV genotypes was observed in sequences with 10-13 substitutions. Thus, it was concluded that the genotypes of JCV DNA in the kidney can be determined only with specimens stored in a frozen state or formalin-fixed for a short time.

Viral infection in the renal transplant recipient

Viruses are among the most common causes of opportunistic infection after transplantation and the most important. The risk for viral infection is a function of the specific virus encountered, the intensity of immune suppression used to prevent graft rejection, and other host factors governing susceptibility. Viral infection, both symptomatic and asymptomatic, causes the "direct effects" of invasive disease and "indirect effects," including immune suppression predisposing to other opportunistic infections and oncogenesis. Rapid and sensitive microbiologic assays for many of the common viruses after transplantation have replaced, for the most part, serologic testing and in vitro cultures for the diagnosis of infection. Furthermore, quantitative molecular tests allow the individualization of antiviral therapies for prevention and treatment of infection. This advance is most prominent in the management of cytomegalovirus, Epstein-Barr, hepatitis B, and hepatitis C viruses. Diagnostic advances have not been accompanied by the development of specific and nontoxic anti-viral agents or effective antiviral vaccines. Vaccines, where available, should be given to patients as early as possible and well in advance of transplantation to optimize the immune response. Studies of viral latency, reactivation, and the cellular effects of viral infection will provide clues for future strategies in prevention and treatment of viral infections.

Polyomavirus BK infection in Greek renal transplant recipients

BK polyoma virus associated nephropathy is increasingly recognized as an important cause of allograft dysfunction among renal transplant recipients. Herein we present the cases of two renal transplant recipients who developed progressive functional deterioration suspicious for BK polyoma virus involvement. One patient had been treated with mycophenolate mofetil (MMF), cyclosporine (CsA), and prednisolone (P), and the second patient with tacrolimus (Tac), MMF, and (P). Using quantitative real-time polymerase chain reactions for BK virus DNA, we monitored the content of BK virus in the blood to evaluate disease progression. The high BK virus load initially detected in the blood samples from these patients decreased in the patient who received MMF, CsA, and P after the reduction of immunosuppression, but not in the patient who was treated with Tac, MMF and P. In contrast to previous reports, our patients had not received treatment with anti-lymphocyte globulin (ALG) or monoclonal anti-CD3 antibody (OKT3) after transplantation. It is concluded that even in the absence of vigorous antirejection treatment, immunosuppressive therapy based on Tac and MMF may carry the risk of BK virus-associated nephropathy. Because BK virus specific antiviral therapy is not available, its course may be monitored by measuring the viral load in blood.

Leucoencéphalopathie multifocale progressive à BK virus chez un patient immunodéprimé par une corticothérapie

INTRODUCTION

BK virus has been described previously in renal transplant patients, but has also been reported in cases of progressive multifocal leukoencephalopathy.

METHOD

A case of progressive BK virus multifocal leukoencephalopathy induced by long-term corticosteroid therapy is reported.

RESULTS

In our case, BK virus was detected in cerebrospinal fluid by polymerase chain reaction (PCR). A detailed review of similar cases in the literature showed most of them occurred in AIDS patients, but four involved immunocompetent patients.

CONCLUSION

Though BK virus infection usually leads to urinary tract symptoms in immunologically suppressed patients, it is important to be aware of its neurological manifestations and to recognize BK infections that can occur in immunocompetent patients.

Detection of JC virus DNA sequences and expression of viral T antigen and agnoprotein in esophageal carcinoma

BACKGROUND

The human polyomavirus JC virus (JCV) causes progressive multifocal leukoencephalopathy. Subclinical infection with JCV occurs in 85-90% of the population worldwide. The virus usually remains latent but can reactivate under immunosuppressive conditions, resulting in progressive multifocal leukoencephalopathy. JCV is oncogenic in experimental animals and is associated with human brain tumors. JCV is found in normal mucosa of the gastrointestinal tract, and some colon carcinomas express the oncogenic JCV T-antigen protein. The objective of this study was to examine the presence of JCV DNA sequences and JCV protein expression in normal and malignant human esophageal tissues.

METHODS

The authors examined the presence of JCV DNA sequences and protein expression in normal and malignant human esophageal tissues. Seventy well characterized biopsy specimens from patients with a spectrum of esophageal disorders were studied by immunohistochemistry, and 18 specimens were analyzed further by polymerase chain reaction amplification.

RESULTS

JC viral DNA was isolated from 11 of 13 normal esophageal biopsy specimens (85%) and from 5 of 5 esophageal carcinomas (100%). Using immunohistochemistry, JCV T antigen was detected in 10 of 19 carcinomas (53%), agnoprotein was detected in 8 carcinomas (42%), p53 tumor suppressor was detected in 11 carcinomas (58%), and beta-catenin was detected in 4 carcinomas (21%). Zero of 51 normal, benign, and premalignant esophageal samples expressed viral proteins. Laser-capture microdissection verified the presence and specificity of JCV DNA sequences. beta-Catenin and p53 were colocalized with JCV T-antigen in the nuclei of neoplastic cells.

CONCLUSIONS

The results provide evidence for infection of gastrointestinal tract cells by JCV and suggest a potential role of JCV in the development of upper digestive tract carcinomas.

Association between a high BK virus load in urine samples of patients with graft-versus-host disease and development of hemorrhagic cystitis after hematopoietic stem cell transplantation

BK virus (BKV) load in urine alone or in combination with acute graft-versus-host disease (GVHD) was correlated to development of hemorrhagic cystitis (HC). BKV load in combination with acute GVHD discriminated the best, while BKV and viral load alone, but not GVHD, still showed predictive ability for HC.