Dynamic viral integration patterns actively participate in the progression of BK polyomavirus-associated diseases after renal transplantation

The classical lytic infection theory along with large T antigen-mediated oncogenesis cannot explain the BK polyomavirus (BKPyV)-associated tumor secondary to BKPyV-associated nephropathy (BKVAN), viremia/DNAemia, and viruria after renal transplantation. This study performed virome capture sequencing and pathological examination on regularly collected urine sediment and peripheral blood samples, and BKVAN and tumor biopsy tissues of 20 patients with BKPyV-associated diseases of different stages. In the early noncancerous stages, well-amplified integration sites were visualized by in situ polymerase chain reaction, simultaneously with BKPyV inclusion bodies and capsid protein expression. The integration intensity, the proportion of microhomology-mediated end-joining integration, and host PARP-1 and POLQ gene expression levels increased with disease progression. Furthermore, multiomics analysis was performed on BKPyV-associated urothelial carcinoma tissues, identifying tandem-like structures of BKPyV integration using long-read genome sequencing. The carcinogenicity of BKPyV integration was proven to disturb host gene expression and increase viral oncoprotein expression. Fallible DNA double-strand break repair pathways were significantly activated in the parenchyma of BKPyV-associated tumors. Olaparib showed an antitumor activity dose-response effect in the tumor organoids without BRCA1/2 genes mutation. In conclusion, the dynamic viral integration patterns actively participate in the progression of BKPyV-associated diseases and thus could be a potential target for disease monitoring and intervention.

The Relationship between Acute Rejection, Hemoglobin Level, and BK Virus Infection Among Renal Transplant Recipients

BACKGROUND

This study aimed to explore the risk factors for BK virus (BKV) infection in renal transplant recipients (RTRs) routinely treated with tacrolimus.

METHODS

Forty-two cases with BKV infections and 51 patients without BKV infections were enrolled in the study. Eighty-seven healthy individuals and 77 patients undergoing dialysis were randomly included as controls. A logistic regression model was used to analyze potential variables in order to evaluate factors related to BKV infection in the renal transplant recipients.

RESULTS

The number of individuals with acute rejection in BKV positive RTRs is significantly higher than that in BKV negative RTRs. Hemoglobin levels in BKV positive RTRs were significantly lower than those in BKV negative RTRs (109.61 ± 20.11 vs. 130.16 ± 26.297, p < 0.001). There was a positive correlation between tacrolimus levels and hemoglobin concentration in RTRs (r = 0.329, p = 0.023). The results of a multivariate regression analysis indicated that a history of acute rejection (OR = 4.157, p = 0.031) and low hemoglobin (OR = 0.963, p < 0.001) were risk factors for BKV infection.

CONCLUSIONS

Acute rejection and low hemoglobin were risk factors for BKV infection after renal transplantation.

Association of donor hepatitis C virus infection status and risk of BK polyomavirus viremia after kidney transplantation

Kidney transplantation (KT) from deceased donors with hepatitis C virus (HCV) into HCV-negative recipients has become more common. However, the risk of complications such as BK polyomavirus (BKPyV) remains unknown. We assembled a retrospective cohort at four centers. We matched recipients of HCV-viremic kidneys to highly similar recipients of HCV-aviremic kidneys on established risk factors for BKPyV. To limit bias, matches were within the same center. The primary outcome was BKPyV viremia ≥1000 copies/ml or biopsy-proven BKPyV nephropathy; a secondary outcome was BKPyV viremia ≥10 000 copies/ml or nephropathy. Outcomes were analyzed using weighted and stratified Cox regression. The median days to peak BKPyV viremia level was 119 (IQR 87-182). HCV-viremic KT was not associated with increased risk of the primary BKPyV outcome (HR 1.26, p = .22), but was significantly associated with the secondary outcome of BKPyV ≥10 000 copies/ml (HR 1.69, p = .03). One-year eGFR was similar between the matched groups. Only one HCV-viremic kidney recipient had primary graft loss. In summary, HCV-viremic KT was not significantly associated with the primary outcome of BKPyV viremia, but the data suggested that donor HCV might elevate the risk of more severe BKPyV viremia ≥10 000 copies/ml. Nonetheless, one-year graft function for HCV-viremic recipients was reassuring.

Scientific and clinical developments in Merkel cell carcinoma: A polyomavirus-driven, often-lethal skin cancer

Merkel cell carcinoma (MCC) is a primary neuroendocrine skin cancer that recurs in ~40% of cases. Merkel cell polyomavirus (MCPyV) and ultraviolet (UV)-induced mutations are two major causative factors of MCC. Virus-positive MCCs express polyomavirus oncoproteins that are highly immunogenic yet are required for ongoing tumor growth. Virus-negative MCCs have a high burden of UV-DNA mutations that encode tumor-specific UV-neoantigens. Thus, both UV- and virus-induced MCCs are highly immunogenic, enabling diverse T-cell targeted therapies. Optimal MCC management is challenging given its rarity, aggressive nature, rapidly evolving care guidelines, and fundamental differences in management compared to other skin cancers. MCC is often managed aggressively with extensive surgery, radiotherapy or systemic therapy, frequently leading to toxicities that might have been avoidable while still achieving optimal disease control. Thus, multi-disciplinary care is crucial for providing patients with the best possible outcomes. The outlook for many patients with advanced MCC has progressed remarkably over the past decade due to PD-1 pathway blocking agents that provide durable benefit for a substantial subset of MCC patients. The management of early-stage MCC has also improved due to better approaches to integrate surgery and radiotherapy. Prognostic accuracy and ongoing surveillance have advanced due to stage-specific recurrence data and sophisticated "liquid biopsies" that allow early detection of disease recurrence. Here we summarize both recent striking progress and pressing challenges such as PD-(L)1-refractory MCC, and management of MCC patients with immune dysfunction. We also highlight diverse resources to allow providers to take advantage of recent progress in this fast-moving field.

BK Virus and Transplantation

As guest editors, we are pleased to present this Special Issue on BK virus (BKV) and transplantation with the intention of exploring some aspects related to BKV-associated diseases in transplant recipients, since they are still unclear [...].

[BK-virus and pathophysiology of associated diseases]

BK virus (BKV) is a widely distributed polyomavirus in the world population. It is the causative agent of BKV-associated nephropathy in kidney transplant recipients and hemorrhagic cystitis in bone marrow transplant patients. To date, there is no specific antiviral treatment against BKV. A better understanding of the pathophysiology of BKV-associated diseases, especially in immunocompromised patients, may contribute to the development of novel preventive and therapeutic strategies. After a detailed description of the genomic characteristics of the virus, its replication cycle and available model systems, the pathophysiological and immune mechanisms involved in BKV infection are developed and discussed in this review.

BK Virus in Kidney Transplantation: A Case Study

Prevention as well as treatment of viral infections in transplant recipients relies on minimal immunosuppressive therapy consistent with graft survival and the use of antiviral therapies in proportion to perceived risk. BK virus creates an even greater challenge in posttransplant management and graft survival because of difficulty in diagnosing and treatment. BK nephropathy develops in 1% to 5% of transplant recipients, with loss of allograft function occurring in 50% of the cases. We present a case of a 67-year-old man who developed BK virus allograft nephropathy 9.5 months after transplantation. His allograft function was extended through rigorous treatment with an antiviral agent, reduction of immunosuppressant, and monitoring in an outpatient setting.

The Bali STD/AIDS Study: human papillomavirus infection among female sex workers

Female sex workers in low priced brothel areas in Denpasar, Bali, Indonesia participated in an intervention study designed to promote condom use and sexually transmitted disease (STD)/AIDS prevention. The intervention provided educational sessions for sex workers, STD treatment for sex workers, condom distribution, and media for clients. The brothel areas were divided into high and low areas for programme effort. The high effort areas received a more intensive behavioural intervention than the low effort areas. A clinic was available for STD treatment in both areas. Behavioural surveys and STD testing were used to evaluate the programmes. About 600 were evaluated for several STDs and completed personal interviews at enrolment and at six-month intervals during the 18-month study. About 50% of women were new to the study at each round. Human papillomavirus (HPV) testing of cervical swabbed specimens, using polymerase chain reaction methodology, was performed at the beginning of the study and 18 months later.

Human papillomavirus infection was initially high in these women (38.3%) and declined to 29.7% after 18 months ( P <0.01). The prevalence of HPV infection declined with age ( P <0.01). HPV infection was associated with a number of STD symptoms that were reported in personal interviews. These associations were stronger in the first time period. Infection with Neisseria gonorrhoeae was associated with HPV infection at baseline ( P =0.03). HPV infection declined in the study area with the more intensive educational programme ( P <0.01). The prevalence of HPV infection declined over time and was associated with study area and age of woman.

BK Virus Infection in Kidney Transplantation: A Case for Early Intervention

The prognosis for renal allograft survival in a patient with BK virus–associated nephropathy is distressing because nearly 50% of affected grafts are lost. With these statistics in mind, attempting clinical intervention before BK virus disease develops seems appropriate. Noninvasive screening tools such as tests to detect decoy cells in urine can enable diagnosis of BK viral infection in its early stages. Although it is not entirely clear which patients with BK infection will have BK disease develop, it may be possible to intervene in this early warning period to prevent the further development of BK virus–associated nephropathy. We present a case of a 50-year-old man in whom asymptomatic BK viruria developed 6 weeks after he received a non-HLA matched kidney from a deceased donor. This BK viruria was accompanied, subsequently, by an unexplained increase in serum creatinine level 2 months after transplantation. Following a change in his immunosuppressive regimen as therapy for presumed renal allograft dysfunction associated with BK viral infection, the decoy cells in his urine disappeared and his creatinine levels stabilized.

Cidofovir in the Treatment of BK Virus-Associated Hemorrhagic Cystitis after Allogeneic Hematopoietic Stem Cell Transplantation

After allogeneic hematopoietic stem cell transplantation (HSCT), BK virus-associated hemorrhagic cystitis (BKV-HC) is a common complication. Although supportive measures have been the standard of care for many years, several studies suggested the efficacy of cidofovir. The aim of this study was to assess the safety profile and efficacy of cidofovir. A retrospective study was conducted on all patients treated with cidofovir in our HSCT unit between March 2011 and May 2013. Data for efficacy (partial [PR] or complete response [CR]), prescription (dose, frequency, number of doses, and administration route), and toxicity were collected from published reports and medical files. Renal toxicity was evaluated using creatinine clearance calculated with the Cockcroft and Gault formula. A parallel literature search using PubMed (last search, May 2015) was performed. From March 2011 to June 2013, 27 of 181 patients undergoing allogeneic HSCT in our department received cidofovir for BKV-HC: 24 (88.9%) intravenously, 1 intravesically, and 2 via both routes. Mean dose was 5 mg/kg per administration, for a median of 4 injections (range, 1 to 11), from twice a week to once every 2 weeks. CR was achieved in 22 patients (81.5%), PR in 2, and no response in 2 patients. Eight patients presented renal failure (29.6%): 6 moderate (creatinine clearance < 60 mL/min) and 2 severe (creatinine clearance < 30 mLmin). Mean decrease in creatinine clearance after cidofovir was 27% (35 mL/min; range, 2 to 159). In 3 cases renal insufficiency and hematologic toxicity led to discontinuation of treatment or switch to intravesical instillation. For 3 patients cidofovir dose was reduced because of nephrotoxicity. Thirteen studies have reported on the use of cidofovir for BKV-HC (204 patients) since 2005. Intravenous cidofovir was used for 91.3% of patients, with doses ranging from .5 to 5 mg/kg. The main toxicity reported was renal failure (9% to 50% in 9 studies). Between 60% and 100% of CRs were observed independently of cidofovir dose or administration route. Cidofovir is an effective therapy for BKV-HC but requires very precise renal function management to avoid toxicity. Cidofovir treatment modalities (high dose, intravesical instillation, or low dose [≤1 mg/kg]) needs to be investigated in randomized controlled trials.

Solid, non-skin, post-liver transplant tumors: Key role of lifestyle and immunosuppression management

Liver transplantation has been the treatment of choice for end-stage liver disease since 1983. Cancer has emerged as a major long-term cause of death for liver transplant recipients. Many retrospective studies that have explored standardized incidence ratio have reported increased rates of solid organ cancers post-liver transplantation; some have also studied risk factors. Liver transplantation results in a two to five-fold mean increase in the rate of solid organ cancers. Risk of head and neck, lung, esophageal, cervical cancers and Kaposi’s sarcoma is high, but risk of colorectal cancer is not clearly demonstrated. There appears to be no excess risk of developing breast or prostate cancer. Environmental risk factors such as viral infection and tobacco consumption, and personal risk factors such as obesity play a key role, but recent data also implicate the role of calcineurin inhibitors, whose cumulative and dose-dependent effects on cell metabolism might play a direct role in oncogenesis. In this paper, we review the results of studies assessing the incidence of non-skin solid tumors in order to understand the mechanisms underlying solid cancers in post-liver transplant patients and, ultimately, discuss how to prevent these cancers. Immunosuppressive protocol changes, including a calcineurin inhibitor-free regimen, combined with dietary guidelines and smoking cessation, are theoretically the best preventive measures.

Incidence and Factors Associated with De Novo DSA After BK Viremia in Renal Transplant Recipients

BK polyomavirus infection and de novo donor-human leukocyte antigen (HLA) specific antibodies (dnDSA) are two well-known and distinct complications occurring after kidney transplantation. Recent literature suggests an association between the two events. This study aims to examine the relationship between BK viremia (BKV) and dnDSA and to identify potential risk factors for dnDSA following BKV in kidney transplant recipients. A retrospective review of 1019 recipients from Houston Methodist Hospital was conducted. All patients underwent routine screening for BKV and dnDSA. Median follow-up was 44 months. BKV was detected in 186 (18%) patients at a median of 107 (82-205) days post-transplant. dnDSA occurred in 283 (28%) patients at a median of 272 (62-575) days post-transplant. Of the 69 dnDSA-positive/BKV-positive patients, dnDSA detection occurred after BKV onset in 46 patients. Thus, 46 (28%) previously DSA-negative patients later became dnDSA-positive following BKV, not significantly different from the rate seen in BKV-negative patients (26%; p=0.5). Median time to DSA detection following BKV onset was 232 days (interquartile range, 119-460) post-BKV detection. Multivariate analysis revealed a greater number of HLA mismatches and viral clearance as risk factors for development of dnDSA following BKV, whereas delayed graft function was associated with a lower risk of dnDSA. In conclusion, despite being considered a result of over-immunosuppression, BKV can still be followed by dnDSA in a substantial proportion of patients. Monitoring for dnDSA in patients being managed for BKV may be warranted.

BIOPSY-PROVEN BK VIRUS NEPHROPATHY WITHOUT DETECTABLE BK VIREMIA IN A ONE-YEAR POST-KIDNEY TRANSPLANT RECIPIENT

BK virus nephropathy (BKVN) is an important clinical problem in kidney transplant (KT) recipients. The sequence of disease is usually viruria, viremia and then nephropathy. Diagnosis of BK virus (BKV) infection includes checking BKV DNA in the urine, in the plasma and histology on renal biopsy. This last method is used to diagnose BKVN. We describe a KT patient with BKVN without detectable BK viremia. A 62-year-old female with hypertensive nephropathy underwent renal transplant from a living relative donor in December 2011. Fourteen months after transplantation, her serum creatinine(SCr) rose up from 1.2 to 1.6 mg/dl with biopsy-proven acute antibody-mediated and cellular rejection. After pulse methylprednisolone, plasmapheresis and intravenous immunoglobulin, her SCr decreased to baseline but she subsequently developed cytomegalovirus infection with pancytopenia and transaminitis. The SCr rose to 1.9 mg/dl despite ganciclovir treatment. Renal ultrasound and antegrade pyelogram showed partial obstruction of the proximal ureter with moderate hydronephrosis. A quantitative polymerase chain reaction (PCR) assay for BKV DNA was negative (less than 10 copies/ml). A renal biopsy was performed and the pathology revealed viral cytopathic changes in the tubular epithelium with interstitial inflammation. The renal biopsy also showed BKV nucleic acid sequences by in-situ hybridization confirming BKVN. Immunosuppression regimen was changed to cyclosporine, low-dose prednisolone and leflunomide. A temporary percutaneous nephrostomy was performed. Her renal function improved within one week. The diagnosis of BKVN should be considered in a KT recipient with a rising SCr with or without BK viremia and should be made by renal biopsy.

[THE ETIOLOGY OF VIRAL INFECTIONS UNDER TRANSPLANTATION OF KIDNEY AND ALGORITHM OF THEIR LABORATORY DIAGNOSTIC]

The article presents data of virology examination of recipients of kidney in respect of actual agents of viral infections--cytomegalovirus, Epshtein-Barr virus, viruses of human herpes simplex type I and II, virus of human herpes type VI, Varicella-zoster virus, parvovirus B19, adenoviruses and BK virus. The dynamics of development of infectious processes were analyzed for dominating viral infections during 12 months after organ transplantation. The etiologic structure of viral complications in recipients of kidney was identified. The dominating role of cytomegalovirus, Epshtein-Barr virus, BK virus infections (41.9, 30.4 and 17.5% correspondingly) was established. The algorithm of implementation of virology examination of donors and recipients with indication of evaluation of obtained data and recommendations for its application.

BK Virus in Recipients of Kidney Transplants

Since its discovery in 1971, the BK virus, a human polyomavirus, has emerged as a significant cause of renal dysfunction and transplant graft loss in kidney transplant recipients. Improved screening methods have been effective in assisting in the early identification of the virus, and thus, prompt intervention to prevent the progression of the disease. Treatment options for the virus are limited; therefore, lowering immunosuppressive medications should be considered the first line of treatment. Current adjunctive therapies are not guaranteed to control the viral activity and may have limited therapeutic value.

Impact of combined acute rejection on BK virus-associated nephropathy in kidney transplantation

BK virus-associated nephropathy (BKVAN) is one of the major causes of allograft dysfunction in kidney transplant (KT) patients. We compared BKVAN combined with acute rejection (BKVAN/AR) with BKVAN alone in KT patients. We retrospectively analyzed biopsy-proven BKVAN in KT patients from 2000 to 2011 at Seoul National University Hospital. Among 414 biopsies from 951 patients, biopsy-proven BKVAN was found in 14 patients. Nine patients had BKVAN alone, while 5 patients had both BKVAN and acute cellular rejection. BKVAN in the BKVAN alone group was detected later than in BKVAN/AR group (21.77 vs 6.39 months after transplantation, P=0.03). Serum creatinine at diagnosis was similar (2.09 vs 2.00 mg/dL). Histological grade was more advanced in the BKVAN/AR group (P=0.034). Serum load of BKV, dose of immunosuppressants, and tacrolimus level showed a higher tendency in the BKVAN alone group; however it was not statistically significant. After anti-rejection therapy, immunosuppression was reduced in the BKVAN/AR group. Renal functional deterioration over 1 yr after BKVAN diagnosis was similar between the two groups (P=0.665). These findings suggest that the prognosis of BKVAN/AR after anti-rejection therapy followed by anti-BKV therapy might be similar to that of BKVAN alone after anti-BKV therapy.

Native kidney BK virus nephropathy associated with acute lymphocytic leukemia

BACKGROUND

Polyoma BK virus nephropathy is a common complication after renal transplantation and is rarely seen in non-renal transplant recipients. There are only a couple of case reports of BK virus nephropathy in native kidneys in non-transplant patients, including a recent report of a 73-year-old patient with chronic lymphatic leukemia. A variety of treatment options, including leflunomide and cidofovir, were reported in these patients.

CASE DIAGNOSIS/TREATMENT

Here we report the case of a 10-year-old boy with acute lymphatic leukemia who presented with non-oliguric hypertensive acute kidney injury at the 12th maintenance cycle of his chemotherapy. The workup supported the clear diagnosis of BK virus nephropathy with tubulointerstitial changes, and the patient responded favorably to intravenous immunoglobulin therapy.

CONCLUSIONS

Pediatric nephrologists need to consider BK virus nephropathy as a differential diagnosis of acute kidney injury in immunocompromised non-transplant patients.

[ABO-incompatible kidney transplantion]

The widespread worldwide implementation of ABO-incompatible kidney transplantation (ABOi KT) programs have increased the chances of gaining access to kidney transplantation. In Italy the practice of ABOi KT has somewhat lagged behind that practiced in many other European Countries. Even though some Italian Transplant Centers have recently started ABOi KT programs, most of them appear still reluctant in adopting this procedure. In this paper, nephrologists from two different Italian Transplant Centers express their contrasting point of view concerning specific issues related to ABOi KT. The first issue concerns the safety and efficacy of ABOi KT and how it compares with HLA-incompatible kidney transplantation. The second concerns to what extent does ABOi KT be adopted, whenever a paired kidney exchange program is available. The third issue regards the indications or contraindications of ABOi KT in specific patient categories. The last issue is about the economical sustainability of ABOi KT programs nowadays. The different point of views of the discussants are summarized in the context of the most recent available evidence.

Patterns of polyomavirus SV40 infections and associated cancers in humans: a model

A model is described that predicts patterns of polyomavirus SV40 infections and associated cancers in humans. The model proposes that SV40 infections were established in humans primarily by exposure to contaminated oral poliovaccines and that infections persist today in geographic regions where poor sanitation or living conditions allow maintenance of infections transmitted by a fecal/urine-oral route. Predictions from the model include that SV40 infections and virus-associated malignancies will be restricted geographically and demographically and that in developed countries, such as the US, SV40 prevalence rates will be generally very low. The model highlights the importance of selection of populations for investigations of SV40 human infections. This model can explain inconsistencies in the published literature of SV40 infections in humans and can guide the design of future studies.

BK virus infection in transplant recipients: clinical manifestations, treatment options and the immune response

Polyomavirus BK (BKV) is ubiquitously present amongst the general population establishing a latent, seemingly asymptomatic infection in immunocompetent individuals. In transplant recipients, however, BKV reactivation is common and can lead to distinctive pathological entities in different patient groups: in renal transplant (RT) recipients, it is associated with nephropathy (BKVN) and ureteral stenosis, and in haematopoietic stem cell transplant (HSCT) recipients with haemorrhagic cystitis (HC). Furthermore, BKV employs several potentially oncogenic mechanisms to promote its replication in cells and has been inconsistently linked to the development of malignancies. BKVN is currently a major cause of allograft failure in RT recipients. HC causes prolonged hospital stay and increased mortality in HSCT recipients. Despite its discovery more than 40 years ago, few advances have been made with regard to therapeutic strategies. Current therapies aim to restore the impaired immune response, e.g. by lowering immunosuppressive agents in RT recipients. However, this is a double-edged sword since it also increases the chance of rejection. Therefore, more specific and effective treatment strategies are urgently needed. Here, we will review the current knowledge on the structure and lifecycle of BKV, characteristics of the BKV-specific immune response, its clinical manifestations and the strengths and limitations of available treatments Polyomavirus BK (BKV) is ubiquitously present amongst the general population establishing a latent, seemingly asymptomatic infection in immunocompetent individuals. In transplant recipients, however, BKV reactivation is common and can lead to distinctive pathological entities in different patient groups: in renal transplant (RT) recipients, it is associated with nephropathy (BKVN) and ureteral stenosis, and in haematopoietic stem cell transplant (HSCT) recipients with haemorrhagic cystitis (HC). Furthermore, BKV employs several potentially oncogenic mechanisms to promote its replication in cells and has been inconsistently linked to the development of malignancies. BKVN is currently a major cause of allograft failure in RT recipients. HC causes prolonged hospital stay and increased mortality in HSCT recipients. Despite its discovery more than 40 years ago, few advances have been made with regard to therapeutic strategies. Current therapies aim to restore the impaired immune response, e.g. by lowering immunosuppressive agents in RT recipients. However, this is a double-edged sword since it also increases the chance of rejection. Therefore, more specific and effective treatment strategies are urgently needed. Here, we will review the current knowledge on the structure and lifecycle of BKV, characteristics of the BKV-specific immune response, its clinical manifestations and the strengths and limitations of available treatments methods.

The influence of immunosuppressive agents on BK virus risk following kidney transplantation, and implications for choice of regimen

The increasing incidence of BK-associated nephropathy following kidney transplantation has prompted an examination of strategies for risk reduction and management through immunosuppression manipulation. Evidence from retrospective and prospective studies suggests that BK viruria and viremia, and the need for BK virus treatment, are higher with tacrolimus than cyclosporine. Combined therapy with tacrolimus and mycophenolic acid may be associated with a particularly higher risk of BK infection, but data are conflicting as to whether mycophenolic acid per se is an independent risk factor. The incidence of BK-related events may be reduced in patients receiving mTOR inhibitors (everolimus or sirolimus) with cyclosporine vs a calcineurin inhibitor with mycophenolic acid. De novo immunosuppression regimens that avoid rabbit antithymocyte globulin and tacrolimus, particularly tacrolimus with mycophenolic acid, may be advantageous, whereas low-exposure cyclosporine with an mTOR inhibitor appears a favorable option. Routine screening for BK infection during the first 2 years posttransplant is recommended to allow preemptive modification of the immunosuppressive regimen. In patients at high risk of BK virus infection, appropriate de novo immunosuppression or very early conversion to an mTOR inhibitor to facilitate reduction or discontinuation of calcineurin inhibitors or antimetabolites should be considered. Extensive further research into optimal avoidance, screening, and treatment strategies is required.

In situ force mapping of mammary gland transformation

Tumor progression is characterized by an incremental stiffening of the tissue. The importance of tissue rigidity to cancer is appreciated, yet the contribution of specific tissue elements to tumor stiffening and their physiological significance remains unclear. We performed high-resolution atomic force microscopy indentation in live and snap-frozen fluorescently labeled mammary tissues to explore the origin of the tissue stiffening associated with mammary tumor development in PyMT mice. The tumor epithelium, the tumor-associated vasculature and the extracellular matrix all contributed to mammary gland stiffening as it transitioned from normal to invasive carcinoma. Consistent with the concept that extracellular matrix stiffness modifies cell tension, we found that isolated transformed mammary epithelial cells were intrinsically stiffer than their normal counterparts but that the malignant epithelium in situ was far stiffer than isolated breast tumor cells. Moreover, using an in situ vitrification approach, we determined that the extracellular matrix adjacent to the epithelium progressively stiffened as tissue evolved from normal through benign to an invasive state. Importantly, we also noted that there was significant mechanical heterogeneity within the transformed tissue both in the epithelium and the tumor-associated neovasculature. The vascular bed within the tumor core was substantially stiffer than the large patent vessels at the invasive front that are surrounded by the stiffest extracellular matrix. These findings clarify the contribution of individual mammary gland tissue elements to the altered biomechanical landscape of cancerous tissues and emphasize the importance of studying cancer cell evolution under conditions that preserve native interactions.

BK virus associated nephropathy in renal transplantation: where do we stand

BK virus is an increasingly identified complication in renal allograft recipients. During the last decade, the use of potent immunosuppressive medications has led to reemergence of this virus. Despite the paucity of randomized trials, we have come a long way in the knowledge of BK virus associated nephropathy. This review highlights the epidemiological, pathogenic, pathological, and clinical aspects of BK virus. It summarizes advances made in prophylaxis and treatment strategies to curtail this virus in an era of modern immunosuppression. The old word of wisdom- prevention is better than cure- might be relevant in context of BK virus prophylaxis with flouroquinolones in years to follow.

Effect of Pap smear collection and carrageenan on cervicovaginal human papillomavirus-16 infection in a rhesus macaque model

BACKGROUND

Human papillomavirus (HPV) infection of the genital mucosa is thought to require trauma to the cervicovaginal epithelium. Therefore, we determined whether a cytology specimen collection procedure (Pap smear), which disrupts the epithelium by design, renders the cervix more susceptible to HPV infection in a primate model.

METHODS

In a series of female rhesus macaques, a speculum examination was performed with (n = 8) or without (n = 4) a cytology specimen collection procedure as it is commonly practiced in a gynecology clinic. An internal digital examination was performed after specimen collection using Surgilube (n = 4) or 1% iota-carrageenan, a previously indentified HPV inhibitor (n = 4) as the lubricant. The cervix was then inoculated with HPV16 pseudovirions expressing red fluorescent protein. After 3 days, the reproductive tracts were excised and the cervix was cryosectioned. Sections were analyzed by fluorescent confocal microscopy for the number of red fluorescent protein-positive keratinocytes.

RESULTS

Substantial infection of the ectocervix, the transformation zone, and the endocervix was detected, but only in conjunction with the cytology specimen collection procedure (cytology using Surgilube vs without cytology using Surgilube, mean = 84 infectious events per section vs mean = 0.05 infectious events per section, difference = 84 infectious events per section, 95% confidence interval = 19 to 384 infectious events per section). When the carrageenan gel was substituted for Surgilube for an internal digital examination, the mean number of infectious events decreased (carrageenan gel vs Surgilube, mean = 3.5 events per section vs mean = 84 infectious events per section difference = 81 events per section, 95% confidence interval = 33 to 213 events per section).

CONCLUSIONS

These findings indicate that cytology screening in women might lead to a transient enhancement of susceptibility to HPV infection and that use of a carrageenan-based gel during the examination might mitigate this enhancement.

[Investigation of BK and JC virus DNA positivities by real-time polymerase chain reaction in the clinical samples of patients with high risk]

Human polyomaviruses, namely BK (BKV) and JC (JCV) viruses are small DNA viruses that cause latent infections worldwide. Primary infections are usually acquired in the early periods of life and are generally asymptomatic. However BKV/JCV infections may cause severe clinical conditions in immunosuppressive patients such as bone marrow and solid organ transplantation or cancer patients. The aim of this retrospective study was to investigate the presence of BKV and JCV nucleic acids by real-time polymerase chain reaction (RT-PCR) in the clinical samples of patients with high risk. A total of 268 (62 blood, 206 urine) samples obtained from 115 immunocompromised patients hospitalized in Gazi University Hospital between July 2007 to January 2009, were included to the study. Viral nucleic acids were extracted from the samples with High Pure PCR Template Preparation Kit (Roche, Germany). By using amplification mix (TIB Molbiol GmbH, Germany) that included primers targeting 174 (JCV) and 219 (BKV) base pair fragments of the small t antigen, and hybridization probes (Roche, Germany), nucleic acids were amplified with LightCycler (Roche Applied Science, Germany) system. As a result, total polyomavirus DNA positivity rate was found as 33.2% (89/268). When BKV and JCV DNA positivities were evaluated according to the samples, 25.2% (53/206) of urine samples yielded positive results for BKV, 14.5% (30/206) for JCV and 2.4% (5/206) for both BKV and JCV. Only one of the blood samples (1/62; 1.6%) were found positive by means of BKV DNA, while none of the blood samples were positive for JCV DNA. The distribution of BKV and JCV DNA positivity rates according to the inpatient clinics were as follows, respectively; 24.3% and 9.5% for pediatric nephrology, 9.6% and 8.2% for renal transplantation unit, 13.5% and 18.9% for adult nephrology, 30.8% and 15.4% for bone marrow transplantation unit, 22.9% and 8.6% for pediatric clinics. In samples from pediatric hematology patients, BKV positivity was 36.4% (4/11), while there were no JCV positivity. However, in hematology patients, while JCV was positive in one of the three samples, no BKV positivity was detected.BKV was seen in three of six samples obtained from patients in the intensive care unit. JCV was positive in both of the two samples obtained from patients in pediatric endocrinology. The only patient that had BKV DNA in blood sample was a renal transplant patient. BKV + JCV DNAs were positive together in only five (1.9%) of the urine samples. In 24% (22/89) of the samples, BKV DNA was found ≥ 10⁷ copies/ml, in 2.2% (2/89) JCV DNA was ≥ 10⁷ copies/ml, whereas in 2.2% (2/89) of samples both BKV and JCV DNA was ≥ 10⁷ copies/ml. All of those samples with high DNA levels were urine. The data of this study led to the establishment of a collaborative algorithm between the laboratory and clinics in our hospital for the diagnosis and follow-up of the patients in terms of BKV/JCV infections. In conclusion, since BKV/JCV reactivations and infections are crutial in immunosuppressive patients, especially medical centers specialized in bone marrow and renal transplantation, diagnostic and monitoring procedures related to those infections should be programmed.

Viral infections after kidney transplantation

Chronic immunosuppression, required to maintain allograft function postorgan transplant, predisposes transplant patients to a variety of viral infections. These can occur at every stage of post-transplantation. Some infections, however, such as cytomegalovirus (CMV), Epstein Barr virus (EBV), or BK virus (BKV), tend to occur within months after transplantation. CMV infections can be easily prevented by prophylaxis therapy whereas EVB or BKV infections can be prevented by lowering (when possible) immunosuppression. Some viral infections can result in posttransplant lymphoproliferative disorders (EBV), Kaposi sarcoma (human herpes simplex virus type 8), or skin and/or cervical cancers (papillomavirus). Other viral infections, such as those due to influenza or para influenzae viruses, respiratory syncytial virus, or West nile fever virus, are mostly acquired through environmental spread. Thanks to modern laboratory technique, and a formidable antiviral armamentarium, viral infections in organ transplant patients i) can be easily detected at early stages, and ii) can be efficiently treated.

Life-style and genital human papillomavirus in a cross-sectional survey in Shanxi Province, China

BACKGROUND

To determine the age-stratified HPV prevalence rate and the risk factors of life-style associated with HPV infection among women in rural China.

METHODS

An age-stratified, cross-sectional survey of 941 women between 16-59 years old was conducted in rural China. Carcinogenic HPV infection was determined using Digene's Hybrid Capture II HPV DNA test and interviews of life-style were conducted. Odds ratios (OR) and 95% confidence interval (CI) from the logistic regression models were used to determine the risk factors associated with HPV.

RESULTS

Among 941 women, 745 who had sexual intercourse underwent a cervical examination. The prevalence rate of 13 carcinogenic HPV infections among women 20-59 years old was 15.97%. the rate of HPV prevalence in the 25-34 age group was statistically lower than that in 20-24 and 35-59 age groups (X²=13.3, P=0.0013). The OR of bathing every 7-19 days, 20-180 days, less than once every 180 days vs. bathing at least once a week were 1.19, 1.83 and 2.29 respectively and they had a dose-response relationship (Trend Test: P=0.003). The OR of women aged 25-34 age group vs. 20-24 age group was 0.40 (0.16 - 0.97) and the OR of bathing once every 180 days or less vs. at least once weekly was 2.22 (1.14 - 4.33) adjusted for the other confounding factors,.

CONCLUSIONS

The HPV prevalence rate was lowest among child bearing women aged 25-34 year. Also, personal hygiene is significantly associated with the HPV infection in this area, regardless of age.

High-level polyomavirus JC viruria following long-term steroid therapy

C virus is a highly seroprevalent ubiquitous polyomavirus which is acquired at an early age through respiratory or oral route, Thereafter JCV establishes persistent, but mainly asymptomatic, infections in various tissues, including the genitourinary tract and brain. In individuals with altered immunity, viral replication can occur leading to serious organ diseases. In contrast to polyomavirus BK, that is found infrequently in the urine of healthy adults, JC viruria occurs universally. Herein we describe a case of an otherwise immunocompetent patient who presented a very high-level asymptomatic polyomavirus JC viruria following long-term steroid therapy.

Cathepsin L is required for ecotropic murine leukemia virus infection in NIH3T3 cells

Recently it has been reported that a cathepsin B inhibitor, CA-074Me, attenuates ecotropic murine leukemia virus (Eco-MLV) infection in NIH3T3 cells, suggesting that cathepsin B is required for the Eco-MLV infection. However, cathepsin B activity was negative or extremely low in NIH3T3 cells. How did CA-074Me attenuate the Eco-MLV infection? The CA-074Me treatment of NIH3T3 cells inhibited cathepsin L activity, and a cathepsin L specific inhibitor, CLIK148, attenuated the Eco-MLV vector infection. These results indicate that the suppression of cathepsin L activity by CA-074Me induces the inhibition of Eco-MLV infection, suggesting that cathepsin L is required for the Eco-MLV infection in NIH3T3 cells. The CA-074Me treatment inhibited the Eco-MLV infection in human cells expressing the exogenous mouse ecotropic receptor and endogenous cathepsins B and L, but the CLIK148 treatment did not, showing that only the cathepsin L suppression by CLIK148 is not enough to prevent the Eco-MLV infection in cells expressing both of cathepsins B and L, and CA-074Me inhibits the Eco-MLV infection by suppressing both of cathepsins B and L. These results suggest that either cathepsin B or L is sufficient for the Eco-MLV infection.

BK virus large T and VP-1 expression in infected human renal allografts

OBJECTIVE

We investigated the expression of early and late phase BK virus (BKV) proteins and their interactions with host cell proteins in renal allografts, with ongoing polyomavirus associated nephropathy (PVAN), and correlated this with the nuclear and cell morphology.

METHODS

Frozen sections from three patients with renal allografts (two biopsies, one explant) with PVAN were analysed by indirect immunofluorescence using BKV specific anti-polyoma large T-antigen and anti-VP-1 antibodies, as well as anti-p53, anti-Ki67, anti-caspase-3, anti-bcl2 and anti-cytokeratin 22 antibodies. Nuclear morphology and size were estimated by DNA Hoechst staining.

RESULTS

In infected tubular cells the early and late phases of infection could be distinguished according to expression of large T-antigen or VP-1. The early phase revealed almost normal nuclear proportions, whereas in later phases nuclear size increased about 2 to 3 fold. Expression of large T-antigen was strongly associated with accumulation of p53 in the nucleus, accompanied by the activation of the cell cycle associated cell protein Ki67. In contrast, expression of BKV VP1 correlated only weakly with p53. Virus dependent cell lysis was due to necrosis, since neither caspase 3 nor nuclear nor cytoskeleton changes indicated apoptosis.

CONCLUSION

In our selected patients with PVAN a clear distinction between early and late phases was possible, according to the protein expression patterns of BKV markers. Striking nuclear enlargement is only present in the late phase of infection. In the inflammatory setting of PVAN, BKV dependent effects appear to be mediated by the inhibition of p53, resulting in the activation of the cell cycle. We assume that in PVAN similar BKV mechanisms are operative as in certain in vitro systems.

[BK viral infection after renal transplantation]

Viral infections have been a subject of great interest in patients after organ transplantations. Post-transplant immunosuppressive therapy is often associated with transfenction or reactivation of viruses. The human polyomavirus type I, also called BKvirus (BKV), causes polyomavirus-associated nephropathy (PVAN) in 1-10% of renal transplant recipients. Thanks to increased PVAN awareness and improved diagnostic techniques, the rate of graft loss has lowered, more consistently in centres with active screening and intervention programs. The risk factors for PVAN are not conclusively defined and likely involve complementing determinants of recipient, graft, and virus. Central element seems to be the failing balance between BKV replication and BKV-specific immune control, which can result from intense triple immunosuppression, HLA-mismatches, prior rejection and anti-rejection treatment, or BKV-seropositive donor/seronegative recipient pairs. PVAN diagnosis requires the evaluation of a renal biopsy showing polyomavirus cytopathic changes and confirming BKV through an ancillary technique such as immunohistochemistry. The success rate of the intervention is increased with earlier diagnosis. Therefore, it is recommended that all renal transplant recipients should be screened for BKV replication in urine and serum. The treatment of BKVN consists mainly of reduction in immunosuppressive therapy. Currently, in the clinical management of PVAN, no satisfactory antiviral treatment has been defined. Retransplantation after renal allograft loss to PVAN remains a treatment option for patients clearing polyomavirus replication.

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 Nephropathy in Pediatric Renal Transplant Recipients: An Analysis of the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) Registry

BACKGROUND AND OBJECTIVES

There is limited information regarding BK virus nephropathy in pediatric kidney transplantation. The objective of this study was to evaluate cases of BK virus nephropathy in the North American Pediatric Renal Trials and Collaborative Studies database.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using a questionnaire that was sent to North American Pediatric Renal Trials and Collaborative Studies centers, we assessed the incidence, risk factors, clinical features, and outcomes of BK virus nephropathy in pediatric renal transplant recipients who received a transplant between 2000 and 2004.

RESULTS

BK virus nephropathy was reported in 25 (4.6%) of 542 patients at a median onset of 10.1 mo after transplantation. The median age was 11 yr. All patients who were tested reported BK viruria, and 19 (91%) of 21 who had plasma tested reported BK viremia. Treatment of BK virus nephropathy included reduction of immunosuppression (84%), cidofovir (24%), leflunomide (8%), and intravenous Ig (20%). Simultaneous rejection treatment was reported in four (16%). The median creatinine was 2.0 mg/dl at a mean follow-up of 24 mo. There were six (24%) graft failures in the patients with BK virus nephropathy at a mean of 24 mo after diagnosis. Rejection occurred in eight (32%) after diagnosis. Multivariate analysis showed that use of polyclonal induction therapy and zero HLA DR mismatch were associated with the development of BK virus nephropathy.

CONCLUSIONS

This first multicenter, retrospective, cohort study of BK virus nephropathy in pediatric renal transplant recipients found a BK virus nephropathy incidence of 4.6% and identified polyclonal induction and zero HLA DR mismatch as significant risk factors for BK virus nephropathy.

Identification of a retroviral receptor used by an envelope protein derived by peptide library screening

This study demonstrates the power of a genetic selection to identify a variant virus that uses a new retroviral receptor protein. We screened a random peptide library within the receptor-binding domain of a feline leukemia virus retroviral Envelope (FeLV Env) protein for productive infection of feline AH927 cells. One variant, A5, obtained with altered tropic properties acquired the ability to use the solute carrier protein family 35 member F2 (SLC35F2) as a receptor. The SLC35F2 protein is a presumed transporter of unknown function predicted to encode 8 to 10 transmembrane-spanning regions and is not homologous to any identified retroviral receptor. Expression of the feline SLC35F2 cDNA in nonpermissive cells renders the cells susceptible to infection by A5 virus, with remarkably high titers in the range of 10(5) infectious units per ml. The human SLC35F2 ORF also functioned as the retroviral receptor, albeit at lower efficiency than the feline homologue. The successful selection of a novel molecule, the SLC35F2 transporter/channel-type protein, as a receptor by the FeLV Env backbone suggests that multipass transmembrane proteins may be particularly suited for use in productive viral entry and fusion. The analysis of retroviral Env libraries randomized in the receptor-binding domain offers a viable means to develop viral vectors targeted to specific cell types in the absence of known targeting ligands.

Is there a role for SV40 in human cancer?

The question of whether Simian Virus 40 (SV40) can cause human tumors has been one of the most highly controversial topics in cancer research during the last 50 years. The longstanding debate began with the discovery of SV40 as a contaminant in poliovirus vaccine stocks that were used to inoculate approximately 100 million children and adults in the United States between 1955 and 1963, and countless more throughout the world. Concerns regarding the potential health risk of SV40 exposure were reinforced by studies demonstrating SV40's potential to transform human cells and promote tumor growth in animal models. Many studies have attempted to assess the relationship between the potential exposure of humans to SV40 and cancer incidence. Reports of the detection of SV40 DNA in a variety of cancers have raised serious concerns as to whether the inadvertent inoculation with SV40 has led to the development of cancer in humans. However, inconsistent reports linking SV40 with various tumor types has led to conflicting views regarding the potential of SV40 as a human cancer virus. Several recent studies suggest that older detection methodologies were flawed, and the limitations of these methods could account for most, if not all, of the positive correlations of SV40 in human tumors to date. Although many people may have been exposed to SV40 by polio vaccination, there is inadequate evidence to support widespread SV40 infection in the population, increased tumor incidence in those individuals who received contaminated vaccine, or a direct role for SV40 in human cancer.

Simian virus 40 in posttransplant lymphoproliferative disorders

Simian virus 40 (SV40) is an oncogenic DNA virus, which is an emergent pathogen implicated in some human malignancies, including B-cell lymphomas. As with other malignancies that occur during immunosuppression, it is hypothesized that SV40 infections may be associated with some posttransplant lymphoproliferative disorders (PTLDs). Specimens were tested initially for Epstein-Barr virus (EBV) by in situ hybridization for EBV-encoded small RNA and/or by immunohistochemical staining for EBV-latent membrane protein 1. Coded DNA specimens extracted from formalin-fixed, paraffin-embedded tissues from 22 PTLD cases were examined by polymerase chain reaction using primers for the SV40 large tumor antigen (T-ag) gene and confirmed by sequence analysis. In addition, samples were assessed for the expression of SV40 T-ag by immunohistochemical staining. Epstein-Barr virus was detected in 18 (82%) of 22 PTLD cases. Simian virus 40 T-ag sequences were detected in 2 (13%) of the 16 cases with amplifiable DNA: one with EBV-negative T-cell PTLD and the other with EBV-positive B-cell monomorphic PTLD. Immunohistochemical staining showed expression of SV40 T-ag in 1 of 2 cases containing viral DNA sequences and in none of the SV40 T-ag DNA-negative samples. Expression of SV40 T-ag was restricted to malignant cells and not to reactive lymphocytes. These results suggest that SV40 may be associated with a small subset of PTLD cases. Additional studies are needed to determine the role of SV40 in EBV-negative PTLD.

Renal transplant patient with polyoma virus bladder infection and subsequent polyoma virus nephropathy

Polyoma virus nephropathy (PVN) is a significant cause of renal allograft dysfunction in transplant patients. A 58-year-old male received a cadaveric renal transplant and 12 weeks later presented with fever, diarrhea, and dysuria. He was diagnosed with a polyoma virus infection of the bladder by a transurethral bladder biopsy. One year post-transplant, he presented with renal allograft dysfunction and was diagnosed by biopsy with PVN of the non-native kidney. The diagnosis of a polyoma virus infection was confirmed by immunoreactivity to the polyoma T-antigen. We suggest that polyoma virus infection of the bladder be included in the differential diagnosis of urinary dysfunction in post-transplant patients, as such infections might be an under-recognized comorbidity in individuals with PVN.

BK virus nephritis after renal transplantation

BK viremia and nephritis are increasing problems in renal transplant recipients. The exact cause of the increasing prevalence of this condition remains poorly understood. Increasing prevalence has been correlated with newer immunosuppressive agents and the decline in acute rejection rates in recent years. The clinical manifestation varies from the asymptomatic state of viremia and nephritis to clinical renal dysfunction. The diagnosis of this infection is based on the combination of the presence of urinary decoy cells, virus in the urine/blood, and typical renal histological findings of interstitial nephritis. Routine post-transplant screening for BK viremia and viruria prior to the occurrence of nephritis and the reduction in immunosuppressive therapy for subjects with viremia appear to be attractive approaches. The treatment of BKV nephritis (BKVN) consists of reduction in immunosuppressive therapy and antiviral therapy with cidofovir or leflunomide or a combination of both. Approximately 30-60% of subjects with BKVN experienced irreversible graft failure. However, in recent years, the combinations of early detection, prompt diagnosis, and appropriate reduction in immunosuppressive therapy have been associated with better outcome. The pathogenesis of BK virus infection in renal transplant recipients needs to be explored. The source of BKV infection (donor as opposed to recipient), the role of host humoral, and cellular immunity to BKV, and the role of alloimmune activation in renal graft to the occurrence of nephritis are discussed in this review.

Transplantation: polyomavirus nephropathy and the risk of specific immunosuppression regimens

BK virus is ubiquitously present in the latent state in humans, and awareness of the importance of BK polyomavirus is emerging among the kidney transplant community. First discovered in 1971 in the urine of a renal transplant recipient, BK virus nephropathy (BKVN) has come to be recognized as a significant cause of genitourinary disease and potential graft loss in the kidney transplant patient. In this review, we discuss the risk factors, available methods of diagnosis and therapeutic monitoring, and current approaches to therapy of BKVN.

Polyoma BK virus and haemorrhagic cystitis in haematopoietic stem cell transplantation: a changing paradigm

Haemorrhagic cystitis (HC) is a distinct clinical disorder of multiple aetiologies. It is characterized by painful haematuria due to haemorrhagic inflammation of the urinary bladder mucosa. In allogeneic haematopoietic stem cell transplantation (HSCT), HC occurring before engraftment is mostly transient and self-limiting, whereas that after engraftment is severe and sometimes life-threatening. Pre- and post-engraftment HC represent distinct disorders with different aetiologies and treatment implications. Recent data suggest that reactivation of the polyoma BK virus (BKV) plays a pivotal role in post-engraftment HC. Urotoxicity of the conditioning regimen and alloimmune reaction accompanying graft-versus-host disease (GVHD) upon engraftment are also important pathogenetic factors. Based on data from BKV studies, we propose that HC may be divided into three phases. In the first phase, the conditioning regimen damages uroepithelial cells, providing a milieu for BKV replication. In the second phase, unchecked uroepithelial BKV replication leads to BK viruria. In the last phase after engraftment, alloimmunity against BKV-infected uroepithelial cells leads to HC. The quinolone antibiotics suppress BKV replication in vivo and in vitro, suggesting that their prophylactic use may prevent the occurrence of HC.

A related donor and reduced intensity conditioning reduces the risk of development of BK virus-positive haemorrhagic cystitis in allogeneic haematopoetic stem cell-transplanted patients

The significance of the BK virus (BKV) and possible co-factors for the development of late onset haemorrhagic cystitis (HC) in allogeneic haematopoetic stem cell (HSCT)-transplanted patients is reviewed. BKV-associated HC causes significant morbidity and mortality in HSCT patients, however, BK-viruria cannot distinguish patients at risk of HC, since it is observed in patients with and without HC. Several studies have therefore attempted to identify co-factors for the development of HC. Acute graft versus host disease was in the past, though less so recently, reported to correlate to the incidence of HC. However, patients who had received grafts from unrelated donors (URD) and had had full conditioning prior to HSCT were shown to have an increased risk of HC, compared to patients who had received HSCT from a related donor (RD) or patients who had received reduced intensity conditioning. In conclusion, HSCT patients with BK-viruria, an URD and receiving full conditioning have an increased risk of developing HC.