Association of renal adenocarcinoma and BK virus nephropathy post transplantation

BK Polyomavirus Activates HSF1 Stimulating Human Kidney Hek293 Cell Proliferation

Objectives

Some DNA viruses, such as BKPyV, are capable of inducing neoplastic transformation in human tissues through still unclear mechanisms. The goal of this study is to investigate the carcinogenic potential of BK polyomavirus (BKPyV) in human embryonic kidney 293 (Hek293) cells, dissecting the molecular mechanism that determines the neoplastic transformation.

Materials and Methods

BKPyV, isolated from urine samples of infected patients, was used to infect monolayers of Hek293 cells. Subsequently, intracellular redox changes, GSH/GSSH concentration by HPLC, and reactive oxygen/nitrogen species (ROS/RNS) production were monitored. Moreover, to understand the signaling pathway underlying the neoplastic transformation, the redox-sensitive HFS1-Hsp27 molecular axis was examined using the flavonoid quercetin and polishort hairpin RNA technologies.

Results

The data obtained show that while BKPyV replication is closely linked to the transcription factor p53, the increase in Hek293 cell proliferation is due to the activation of the signaling pathway mediated by HSF1-Hsp27. In fact, its inhibition blocks viral replication and cell growth, respectively.

Conclusions

The HSF1-Hsp27 signaling pathway is involved in BKPyV infection and cellular replication and its activation, which could be involved in cell transformation.

Urothelial carcinoma of the graft kidney with molecular analyses: a rare case report

Background

Malignancy after transplantation is a leading cause of death among kidney transplant recipients. However, donor-derived malignancies are rare. We report a case of a high grade papillary urothelial carcinoma arising in a transplanted kidney.

Case presentation

A 62-year-old female who received a kidney transplantation more than 30 years ago presented with urinary tract infection, acute renal failure, and hydronephrosis of the transplant kidney. Anterograde nephrostogram showed a large filling defect in the lower pole of the transplant kidney and in the proximal 3–4 cm of the ureter. A biopsy from the renal pelvic mass showed a high grade urothelial carcinoma. She underwent an anterior exenteration, resection of both transplant and native kidneys and bilateral pelvic lymph node dissection. Pathologic examination showed a high grade papillary urothelial carcinoma which appeared to arise in the pelvis of the graft kidney, involve the graft ureter and native urinary bladder. The tumor had metastasized to one left obturator lymph node but spared the two native kidneys and ureters. Short tandem repeat (STR) analysis confirmed the tumor to be of donor origin. Next-generation sequencing identified amplification of TERT and loss of CDKN2A/CDKN2B in the primary tumor.

Conclusion

While it is known that transplant recipients have an increased risk of urothelial carcinoma compared to the general population, the lack of the well-documented risk factors, such as older age at transplantation, BK polyomavirus infection, and prolonged post-transplantation history and dissemination of the tumor in this case shed light on the de novo tumorigenesis of the graft kidney within the host microenvironment. Amplification of Telomerase reverse transcriptase (TERT) and loss of cyclin dependent kinase inhibitor 2A/2B (CDKN2A/CDKN2B) detected in the tumor by next gene sequencing suggests that they may play an important role in this case.

Allograft renal cell carcinoma in pediatrics transplantation: A mini-review

Renal cell carcinoma in the pediatric age group is a rare event, and its occurrence in the allograft (recipient) kidney is an uncommon event. There is no published review study in RCC of allograft kidneys in children and adolescents. In this study, we thoroughly searched English literature (PubMed, Google Scholar, and Google) in order to find all the reported allograft kidney RCCs in the patients who have been transplanted below the age of 18. There have been 12 reports of allograft RCC in this age group. Our result showed that the age of tumor detection according to donor age is lower comparing to non-allograft RCCs, and there is a significant male preponderance. RCC in the allografts is smaller and shows low nuclear grade and has a good prognosis. These findings emphasize the importance of routine allograft ultrasonography which results in earlier detection of RCC with smaller size and better outcome.

BK Virus in Cancer Development

Polyomavirus (PyV) was discovered by accident in 1950 in the course of describing an infectious factor causing multiple tumours in rodents. The term is derived from two Greek words: poly (many) and oma (tumour). At present the family of human polyomaviruses (HPyV) consists of 10 members. One of the first members was BK virus, isolated in 1971 from the urine of a renal transplant patient. Serological examinations have shown that due to its ability to cause latent infection, about 90% of the general population can have specific antibodies attesting infection. In the case of infected persons with normal immunity, this virus is not dangerous. In the impaired immunity, however, loss of immunity results in virus reactivation and development of many life-threatening illnesses. Serological examinations have also reveal that BK polyomavirus considerably affects the development of cancers in humans. Hence, in 2012 a group of 26 researchers from 11 countries associated with the International Agency for Research on Cancer (a part of the World Health Organisation) classified BK polyomavirus within group 2B - “potentially carcinogenic to humans”

Risk factors associated with post-kidney transplant malignancies: an article from the Cancer-Kidney International Network

In kidney transplant recipients, cancer is one of the leading causes of death with a functioning graft beyond the first year of kidney transplantation, and malignancies account for 8-10% of all deaths in the USA (2.6 deaths/1000 patient-years) and exceed 30% of deaths in Australia (5/1000 patient-years) in kidney transplant recipients. Patient-, transplant- and medication-related factors contribute to the increased cancer risk following kidney transplantation. While it is well established that the overall immunosuppressive dose is associated with an increased risk for cancer following transplantation, the contributive effect of different immunosuppressive agents is not well established. In this review we will discuss the different risk factors for malignancies after kidney transplantation.

BK virus-associated collecting duct carcinoma of the renal allograft in a kidney-pancreas allograft recipient

BK polyomavirus (BKV) nephropathy is a major concern in renal transplantation. Its main consequence is graft loss, which occurs in more than 50% of the cases. De novo renal cell carcinoma in renal allograft is a very rare event. Most of these tumors are papillary or clear cell carcinomas. We report herein the first case of collecting duct carcinoma of the renal allograft in a kidney-pancreas allograft adult recipient. Collecting duct carcinoma occurs long after the cure of a BKV nephropathy. At this time, BKV viremia and viruria were negative as well as the immunostaining for SV40 in the non-tumor kidney. The viral oncoprotein Tag persists only in the tumor cells. To preserve pancreas graft function, we maintained immunosuppression levels. After a 9-months follow-up, the evolution was free from clinical and radiological progression. The oncogenic role of BKV remains controversial in human cancers. However, strong experimental data have shown an association between BKV infection and urologic neoplasms. Further works might precise the exact role of polyomaviruses in renal carcinogenesis. In the meantime, clinical vigilance for early diagnostic of these tumors is mandatory after BKV nephropathy.

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

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

Infectious Diseases and the Kidney in Children

The kidney is involved in a wide range of bacterial, viral, fungal, and parasitic diseases. In most systemic infections, renal involvement is a minor component of the illness, but in some, renal failure may be the presenting feature and the major problem in management. Although individual infectious processes may have a predilection to involve the renal vasculature, glomeruli, interstitium, or collecting systems, a purely anatomic approach to the classification of infectious diseases affecting the kidney is rarely helpful because most infections may involve several different aspects of renal function. In this chapter, a microbiological classification of the organisms affecting the kidney is adopted. Although they are important causes of renal dysfunction in infectious diseases, urinary tract infections and hemolytic uremic syndrome (HUS) are not discussed in detail because they are considered separately in chapters XX and XX, respectively.

The oncogenic potential of BK-polyomavirus is linked to viral integration into the human genome

It has been suggested that BK-polyomavirus is linked to oncogenesis via high expression levels of large T-antigen in some urothelial neoplasms arising following kidney transplantation. However, a causal association between BK-polyomavirus, large T-antigen expression and oncogenesis has never been demonstrated in humans. Here we describe an investigation using high-throughput sequencing of tumour DNA obtained from an urothelial carcinoma arising in a renal allograft. We show that a novel BK-polyomavirus strain, named CH-1, is integrated into exon 26 of the myosin-binding protein C1 gene (MYBPC1) on chromosome 12 in tumour cells but not in normal renal cells. Integration of the BK-polyomavirus results in a number of discrete alterations in viral gene expression, including: (a) disruption of VP1 protein expression and robust expression of large T-antigen; (b) preclusion of viral replication; and (c) deletions in the non-coding control region (NCCR), with presumed alterations in promoter feedback loops. Viral integration disrupts one MYBPC1 gene copy and likely alters its expression. Circular episomal BK-polyomavirus gene sequences are not found, and the renal allograft shows no productive polyomavirus infection or polyomavirus nephropathy. These findings support the hypothesis that integration of polyomaviruses is essential to tumourigenesis. It is likely that dysregulation of large T-antigen, with persistent over-expression in non-lytic cells, promotes cell growth, genetic instability and neoplastic transformation.

Seroprevalence rates of BKV, JCV, and MCPyV polyomaviruses in the general Czech Republic population

JC and BK polyomaviruses (JCV and BKV) infect humans and can cause severe illnesses in immunocompromised patients. Merkel cell polyomavirus (MCPyV) can be found in skin carcinomas. In this study, we assessed the occurrence of serum antibodies against MCPyV, BKV, and JCV polyomaviruses in a healthy population of the Czech Republic. Serum samples from 991 healthy individuals (age range: 6-64 years) were examined by enzyme-linked immunoassay (ELISA) using virus-like particles (VLPs) based on the major VP1 capsid proteins of these viruses. Overall, serum antibodies against MCPyV, JCV, and BKV were found in 63%, 57%, and 69%, respectively, of this population. For all three viruses, these rates were associated with age; the occurrence of antibodies against MCPyV and JCV was highest for those older than 59 years, while the occurrence of antibodies against BKV was highest in those aged 10-19 years and 20-29 years. This is the first large study to determine the seroprevalence rates for BKV, JCV, and MCPyV polyomaviruses in the general Czech Republic population.

Human polyomaviruses in disease and cancer

Today the human polyomavirus (HPyV) family consists of 10 members, BK virus (BKV) and JC virus (JCV) isolated 40 years ago and the more recently identified KI virus (KIPyV), WU virus (WUPyV), Merkel cell polyomavirus (MCPyV), HPyV6, HPyV7, trichodysplasia spinulosa virus (TSPyV), HPyV9 and MWPyV. Serological studies suggest that HPyVs subclinically infect the general population with rates ranging from 35% to 90%. However, significant disease is only observed in patients with impaired immune functions. Thus, BKV has been linked to hemorrhagic cystitis (HC) after allogeneic hematopoietic stem cell transplantation and PyV-associated nephropathy (PyVAN) after kidney transplantation; JCV to progressive multifocal leukoencephalopathy (PML) in HIV-AIDS, hematological diseases and in autoimmune diseases treated with certain lymphocyte-specific antibodies. KIPyV and WUPyV have been found in the respiratory tract, HPyV6 and 7 in the skin, and HPyV9 in serum and skin, and MWPyV in stools and skin, but so far none of these PyVs have been linked to any disease. TSPyV, on the other hand, was identified in trichodysplasia spinulosa, a rare skin disease characterized by virus-induced lytic as well as proliferative tumor-like features that is observed in immune-suppressed transplant patients. In contrast to all the other HPyVs so far, MCPyV is unique in its association with a cancer, Merkel cell carcinoma, which is a rare skin cancer arising in the elderly and chronically immunosuppressed individuals. The discovery of the new HPyVs has revived interest in the Polyomaviridae and their association to human disease and cancer. In this review, we summarize knowledge about this expanding family of human pathogens.

Carcinoma of the collecting ducts of Bellini and renal medullary carcinoma: clinicopathologic analysis of 52 cases of rare aggressive subtypes of renal cell carcinoma with a focus on their interrelationship

Carcinoma of the collecting ducts of Bellini and renal medullary carcinoma are rare aggressive neoplasms of putative distal nephron origin. First described in 1949, case reports and review articles constitute a major source of information on collecting duct carcinoma, whereas Davis and colleagues and the pediatric tumor registry have contributed the seminal works on renal medullary carcinoma. Here we present a detailed study of collecting duct carcinoma (n=39) and renal medullary carcinoma (n=13), characterizing these rare neoplasms and analyzing their interrelationship. Both collecting duct carcinoma and renal medullary carcinoma exhibited significant similarities, such as predilection for the right kidney, tumor mass with an epicenter in the renal medulla, and a mean size of 7 cm. Overall, both tumors exhibited a poorly differentiated adenocarcinoma histology with desmoplastic stromal response (100%), inflammatory infiltrate (100%), frequent perinephric extension (collecting duct carcinoma: 97%; renal medullary carcinoma: 83%), lymphovascular invasion (100%), intraluminal mucin (collecting duct carcinoma: 42%; renal medullary carcinoma: 73%), high nuclear grade (97%), overlapping immunoreactivity for Ulex europaeus agglutinin 1 (collecting duct carcinoma: 75%; renal medullary carcinoma:55%), CK7 (collecting duct carcinoma: 44%; renal medullary carcinoma: 71%), and high-molecular weight cytokeratin (collecting duct carcinoma: 26%; renal medullary carcinoma: 29%), and nonimmunoreactivity for Ksp-cadherin. Histologically, collecting duct carcinoma frequently had tubular, tubulopapillary, or irregular glandular architecture, whereas renal medullary carcinoma commonly demonstrated islands of anastomosing tubules and cords forming irregular microcystic spaces. Multiple metastases to the lymph nodes, lung, bone, and liver were observed in both categories at presentation (collecting duct carcinoma: 17%; renal medullary carcinoma: 36%). Only patients with organ-confined small tumors were disease free beyond the median survival time. Differential clinical features between collecting duct carcinoma and renal medullary carcinoma included proclivity for younger male individuals of African ancestry with hemoglobin abnormalities and a shorter median survival of 17 weeks (vs. 44 wk for collecting duct carcinoma) for renal medullary carcinoma. The markedly overlapping clinical features, histology, immunophenotype, metastasis patterns, and uniformly aggressive outcome in collecting duct and renal medullary carcinomas suggest that renal medullary carcinoma is a distinctive clinicopathologic subtype within the entity of collecting duct carcinoma. The extremely poor prognosis and ongoing clinical trials with specific therapeutic protocols argue for their accurate distinction from other renal cell carcinoma subtypes.

Renal cell carcinoma in the allograft: what is the role of polyomavirus?

BK virus (BKV) is known to cause subclinical infection in childhood. The virus remains latent in the human body, mainly in the urinary tract epithelium. After initiation of an immunosuppressive treatment, reactivation can occur in renal transplant recipients. BKV can cause hemorrhagic cystitis, ureteral stenosis and BKV nephropathy in immunocompromised patients. Furthermore, a number of case reports suggest an association between BKV infection and the development of urinary tract cancer. So far, an oncogenic potential of BKV has been observed in vitro and in animal models; however, its oncogenic capacity in humans remains unclear. We report the case of a 59-year-old patient who developed a poorly differentiated renal cell carcinoma in her renal allograft, with pulmonary and abdominal metastasis. Surgical removal of the allograft and cessation of the immunosuppressive therapy resulted in complete resolution of the metastatic disease.

Adaptive immunity rather than viral cytopathology mediates polyomavirus-associated nephropathy in mice

Nephropathy associated with BK polyomavirus causes kidney allograft dysfunction and failure. Understanding the pathogenesis of polyomavirus-associated allograft nephropathy (PVAN) is hampered by the species specificity of Polyomaviridae family members. Using a mouse polyomavirus (MPyV) kidney transplant model, we investigated clinically relevant variables that may contribute to PVAN. We found that the timing and source (i.e. donor vs. recipient) of MPyV infection and the titer of the viral inoculum have significant effects on the extent of allograft injury, with acute infection of the recipient by high-titer MPyV inoculums producing the most profound PVAN. In contrast, altering the degree of MHC matching or increasing ischemia/reperfusion injury by prolonging the cold ischemic time of the allograft did not affect the severity of PVAN. Survival correlated positively with serum creatinine levels, but not with viral loads in the kidney allograft. Using splenectomized alymphoplasia mice, which are unable to mount primary adaptive immune responses, we further demonstrate that persistent high viral loads in the kidney are not sufficient to cause advanced PVAN. These findings suggest that the mechanism of PVAN in mice is not a direct consequence of viral cytopathology, but rather involves interplay between viral infection and the recipient antidonor immune response.

Cryptosporidium enteritis in solid organ transplant recipients: multicenter retrospective evaluation of 10 cases reveals an association with elevated tacrolimus concentrations

BACKGROUND

Cryptosporidial enteritis, a diarrheal infection of the small intestine caused by the apicomplexan protozoa Cryptosporidium, is infrequently recognized in transplant recipients from developed countries.

METHODS

A retrospective review of all cases of cryptosporidiosis in solid organ transplant (SOT) recipients at 2 centers from January 2001 to October 2010 was performed and compared with transplant recipients with community-onset Clostridium difficile infection (CDI). A literature search was performed with regard to reported cases of cryptosporidiosis in SOT recipients.

RESULTS

Eight renal, 1 liver, and 1 lung transplant recipient were diagnosed with cryptosporidiosis at median 46.0 months (interquartile range [IQR] 25.2-62.8) following SOT. Symptoms existed for a median 14 days (IQR 10.5-14.8) before diagnosis. For the 9 patients receiving tacrolimus (TAC), mean TAC levels increased from 6.3 ± 1.1 to 21.3 ± 9.2 ng/mL (P = 0.0007) and median serum creatinine increased temporarily from 1.3 (IQR 1.1-1.7) to 2.4 (IQR 2.0-4.6) mg/dL (P = 0.008). By comparison, 8 SOT recipients (6 kidney, 2 liver) hospitalized with community-onset CDI had a mean TAC level of 10.8 ± 2.8 ng/dL during disease compared with 9.2 ± 2.3 ng/mL at baseline (P = 0.07) and had no change in median creatinine. All patients recovered from Cryptosporidium enteritis after receiving various chemotherapeutic regimens.

CONCLUSIONS

Cryptosporidiosis should be recognized as an important cause of diarrhea after SOT and is associated with elevated TAC levels and acute kidney injury. Increased TAC levels may reflect altered drug metabolism in the small intestine.

The role of immunosuppression in malignancies among 351 pediatric renal transplant patients

The incidence of de novo malignancies over a 38 year experience in 351 children ranging in age from 2 to 18 years was investigated among subjects prescribed various immunosuppressive protocols. There were 14 children (3.98%) who showed de novo malignancies, namely, 4.86 cancers for every 1000 graft-function years (GFYs). Among patients who had grafts functioning for >10 years, 7.4% suffered from cancer. Nine patients survive without a recurrence at a mean of 12.5 +/- 6.6 years including 6 with graft function. Among group I who were treated with pre-calcineurin inhibitor (CNI) therapy 3 (3.8%) children (1 male and 2 females) developed a malignancy at a mean of 15.2 +/- 11.9 years posttransplant (range, 7-35), for 4.65 cancers every 1000 GFYs. Two of them survive with functioning grafts. Among group II, who were treated by CNIs there were 273 children including 24 retransplants. Group II showed 11 malignancies (4.0%), for 5.04 malignancies for every 1000 GFYs. The incidence of cancer was similar in the 2 groups, undergoing different immunosuppressive regimens; however, the malignancies in the CNI- group were more precocious, compared with those of the conventionally-treated cohort.

The decade of polyomavirus BK-associated nephropathy: state of affairs

In the last 10 years, better immunosuppression drugs have decreased the rates of acute rejection in kidney transplantation but have also led to the emergence of polyomavirus-associated nephropathy (PVAN). This occurs in 1% to 10% of patients with kidney transplantion and is caused by BK virus in more than 95% of cases. Less than 5% of cases are attributed to the JC virus. Initially, lack of recognition or late diagnosis of PVAN resulted in rapid loss of graft function in more than 50% of patients. In recent years, it has become clear that early diagnosis and timely reduction in immunosuppression is the only proven measure, which significantly affects the outcome of PVAN. Diverse interventions have been explored including the adjunctive use of cidofovir, leflunomide, fluoroquinolones, and intravenous immunoglobulins. Allograft histology is needed to definitively establish the diagnosis of PVAN, but is of limited sensitivity in the early stage of disease. Well-established techniques and protocols for systematic screening by urine cytology and quantitative molecular-genetic techniques allow now for timely intervention before irreversible parenchymal changes occur. Moreover, preemptive reduction in immunosuppression is most effective in presumptive PVAN as defined by surrogate markers (i.e., high BK virus viremia). In this setting, preservation of graft function can be considered the rule. Nevertheless, the recovery of BK virus-specific T-cell immunity may require prolonged periods during which cytopathic damage may continue to accumulate. Despite remarkable progress in the field, important challenges remain, such as the rare patient with PVAN refractory to any intervention and the newly recognized association of PVAN with urogenital tumors.

BK virus and human cancer: innocent until proven guilty

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

Treatment options and outcome for renal cell tumors in the transplanted kidney

The diagnosis of renal cell carcinoma in a transplanted kidney is rare but with possibly devastating consequences. In addition to transplant nephrectomy, which inevitably results in a return to dialysis, various treatment options such as different techniques for nephron sparing surgery and local ablative procedures (like radiofrequency ablation or cryoablation) have been described in the literature. An important issue is to find the balance between the preservation of the transplant function, on the one hand, which is dependent on the maintenance of an immunosuppressive regimen, and a sufficiently radical tumor therapy on the other hand. To provide an overview of current therapeutic attempts to cure transplant renal cell carcinoma under these conditions, published data on related therapies and outcomes are summarized.

Collecting duct carcinoma arising in association with BK nephropathy post-transplantation in a pediatric patient. A case report with immunohistochemical and in situ hybridization study

The development of malignancy in a renal transplant graft is an uncommon phenomenon. A renal neoplasm developing in the adult donor kidney of a pediatric transplant recipient has only rarely been reported. We report a case of collecting duct carcinoma arising in association with BK virus nephropathy in an adult living-related donor renal allograft to a pediatric recipient. Our case is the second report of neoplasia occurring in association with BK virus nephropathy post-transplantation, suggesting that BK virus may play a role in oncogenesis. It has been proposed that the T-Ag protein encoded by the polyomavirus family of viruses disrupts chromosomal integrity, creating oncogenes, and inactivating tumor suppressor genes. In our study, immunohistochemical staining with antibody directed against BK virus large T antigen showed nuclear staining within urothelium, tubular epithelium, tubular intraepithelial neoplasia, and invasive carcinoma. In situ hybridization did not identify BK virus DNA within neoplastic cells. T-Ag protein expression has been shown to be tumor-specific in bladder, gastric, and colorectal cancers. The finding of T-Ag protein expression in both intraepithelial and invasive neoplastic tissues in our case raises the possibility of BK virus as a causative agent in oncogenesis.

BK virus induced nephritis in a boy with acute myeloid leukaemia undergoing bone marrow transplantation

BK virus (BKV) is a human polyomavirus. The primary infection occurs typically without specific signs or symptoms. Almost 80% of adults are seropositive. 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 the setting of immunosuppression. BKV is associated with tubulointerstitial nephritis and ureteric stenosis in renal transplant recipients. Furthermore, BKV-induced haemorrhagic cystitis (HC) is a severe complication of bone marrow transplantation (BMT) in children and adults. A combination of HC and tubulointerstitial nephritis in a patient has not been reported so far. We report on an 11-year-old boy with acute myeloid leukaemia undergoing BMT. BKV infection was reactivated during post-transplant immunosuppressive therapy causing HC associated with tubulointerstitial nephritis.

BK virus infection, replication, and diseases in pediatric kidney transplantation

Polyomavirus-associated nephropathy is diagnosed in 2-8% of pediatric renal transplants and often precedes renal allograft dysfunction. Without intervention, however, significant graft dysfunction is observed in more than 50% of cases, although progressive early graft loss is reported in only three of 32 (9%) of cases. No specific treatment is available, but early decrease in immunosuppression is followed by declining human polyomavirus type 1 (BK virus) replication and improved outcome. The data suggest differences between pediatric and adult kidney transplantation. Possibly, pediatric patients might be able to mount a more vigorous BK virus-specific immune response than adult patients under similar modulation of immunosuppression. Also the role of cidofovir and leflunomide is still unresolved in pediatric patients. Larger prospective trials are needed to better define the impact of BK virus immunity for replication and disease as well as the role of reducing immunosuppression with or without cidofovir or leflunomide in pediatric transplant patients.

BK virus associated renal cell carcinoma: case presentation with optimized PCR and other diagnostic tests

Polyomaviruses, including BK and JC viruses, have been associated with graft failure, but have not commonly been associated with malignancy. We present a case of renal cell carcinoma arising in an allograft kidney, in which the tumor and metastasis contain viral DNA. Tumor and biopsy specimens from this patient were examined with hematoxylin & eosin, immunohistochemistry (IHC) and in situ hybridization (ISH). The results were confirmed by real-time polymerase chain reaction (PCR) analysis with BKV primers. Other viruses including herpes simplex 1-2, cytomegalovirus (CMV), Epstein-Barr virus (EBV), and varicella zoster were not detected. The presence of BKV DNA in a renal cell carcinoma, including a metastatic focus, adds to the evidence that this virus may play a role in cancers of the kidney and urinary tract.

Polyoma virus in pediatric renal transplantation

Renal transplantation is the treatment of choice for children with end-stage renal disease. Patient survival and allograft survival have improved with better immunosuppressant regimes to reduce acute allograft rejection but post-transplant infections have been exacerbated. An emerging problematic virus in the past decade is the polyoma virus BKV. The features of BKV including the clinical features in the general and immune compromised population are reviewed and correlated with pediatric studies in the post-transplant population. These features are placed in context with lessons learned about BKV in relevant adult studies.

BK virus: opportunity makes a pathogen

More than 70% of the general population worldwide has serological evidence of exposure to Polyomavirus hominis type 1, better known as BK virus (BKV). BKV infection typically occurs during childhood, without specific symptoms, followed by a state of nonreplicative infection in various tissues, with the urogenital tract as the principal site. Asymptomatic reactivation and low-level replication with viruria is observed in 5% of healthy individuals. Persistent high-level BKV replication is the hallmark of polyomavirus-associated nephropathy in renal transplantation and of hemorrhagic cystitis in bone marrow transplantation. Since these manifestations are rare in other types of immunocompromised patients, the presence of specific cofactors is postulated. The role of BKV in autoimmune disease and cancer is a controversial topic and is difficult to determine, because the pathology no longer depends on BKV replication. This article discusses current views of pathogenesis, diagnosis, and treatment.