Rapid kidney allograft failure in patients with polyoma virus nephritis with prior treatment with antilymphocyte agents

Incidence and risk factors of infections following kidney transplantation

BACKGROUND

For patients with End-Stage Renal Disease (ESRD), kidney transplantation stands as the superior alternative to dialysis, exhibiting enhancements in both quality of life and survival rates. The objective of this study is to ascertain the prevalence of infections and associated risk factors within the initial two years post-renal transplant.

METHOD

A retrospective study of all renal transplant recipients who underwent renal transplantation at king Abdullah medical city in Makkah, Saudi Arabia from January 1st, 2018, till end of December 2021 followed up for two years.

RESULTS

A total of 43 patients were included in the study, The participants who experienced infectious episodes had a higher mean age, averaging 45.26 ± 14, in contrast to those who did not, averaging 38.75 ± 12. Most of the patients included in the study were male, 70 % of the total population. However, most infectious complications occurred in women (77 % vs. 30 %, respectively, p-value 0.004). Regarding the mode of dialysis before the transplantation, most of the patients were maintained on hemodialysis (76.7 %), and the mean duration of dialysis was longer on those presented with infections within two years post-transplant compared to those without it (3.26 ± 1.6 vs. 2 ± 1.14 years respectively). The incidence of the infections was 44.2 % (19 individuals). The most common presented infections in the patients within two years post renal transplant were urinary tract infections (20.9 %), with a high recurrence rate reaching 11.6 %. This was followed by Coronavirus disease (COVID-19) and Cytomegalovirus (CMV).

CONCLUSION

This study sheds light on the prevalence of infectious complications following renal transplantation and highlights specific risk factors associated with these infections. Understanding these patterns can aid in the development of preventive strategies and optimized care for transplant recipients during the early post-transplant period.

Outcomes of de novo belatacept-based immunosuppression regimen and avoidance of calcineurin inhibitors in recipients of kidney allografts at higher risk for underutilization

To describe an experience using a protocol using de novo belatacept (DNB) based maintenance immunosuppression in the setting of lymphocyte depletion. A retrospective, observational study was performed on 37 kidney transplant recipients treated with the DNB protocol, which was defined as belatacept initiated within 7 days after a kidney transplant with steroids and mycophenolate with anti-thymocyte globulin (ATG) induction without concomitant calcineurin inhibitors (CNIs). Patients who received a deceased donor kidney meeting one or more of the following criteria: anticipated cold ischemia time (CIT) greater than 24 h, donation after cardiac death, donor acute kidney injury, and a Kidney Donor Profile Index (KDPI) >85% during the study period were included. Patient survival at 1 year was 97.3% and graft survival was 94.6%. Delayed graft function (DGF) occurred in 40.54% of the patients. Two patients experienced a Banff 1B acute cellular rejection. BK viremia was detected in 32.4% of patients. The mean estimated glomerular filtration rate (eGFR) calculated with the use of modification of diet in renal disease (MDRD) equation at 1 year in the study group was 54.7 ml/min/1.73 m² . We believe that utilization of the DNB protocol, which allows early CNI avoidance, may decrease organ discard rates.

Patient and Graft Survival Outcomes During 2 Eras of Immunosuppression Protocols in Kidney Transplantation: Indiana University Retrospective Cohort Experience

BACKGROUND

Since 1964 when Indiana University performed its first kidney transplant, immunosuppression protocol was steroid-based until 2004 when steroid-free immunosuppression protocol was adopted. We describe clinical outcomes on our patients administered early steroid withdrawal (ESW) protocol (5 days) compared with our historical cohort (HC), who were on chronic steroid-based immunosuppression.

METHODS

We performed a retrospective study evaluating kidney transplant recipients between 1993 and 2003 (HC, n = 1689) and between 2005 and 2016 (ESW cohort, n = 2097) at the Indiana University program, with a median follow-up of 10.5 years and 6.1 years, respectively. Primary outcomes were patient and death-censored graft survival at 1, 3, and 5 years in both study cohorts. Secondary outcomes were 1-year rates of biopsy-proven acute rejection; graft function at 1, 3, and 5 years; and risk of post-transplant infection (BK virus and cytomegalovirus) in the ESW cohort. Cox proportional model and Kaplan-Meier estimates were used to estimate survival probabilities. Fisher exact tests were used to compare episodes of acute rejection in the ESW cohort.

RESULTS

No difference was observed in patient survival between the ESW and HC cohorts (P = .13). Compared with the ESW cohort, death-censored graft survival was significantly worse in the HC (5 year: 86.4% vs 90.6%, log-rank P < .001). One-year acute rejection reported in the ESW cohort alone was 15.7% and significantly worse in Black patients and younger patients (P < .05).

CONCLUSIONS

In this sizeable single-center cohort study with significant ethnic diversity, ESW is a viable alternative to steroid-based immunosuppression protocol in kidney transplant recipients.

Screening for BK Viremia/Viruria and the Impact of Management of BK Virus Nephropathy in Renal Transplant Recipients

OBJECTIVES

The prevalence of BK-induced nephritis in renal transplant recipients is estimated to be 1% to 10%; the rate of graft loss within 1 year is 30% to 65%. We conducted this study to evaluate screening of BK virus in blood and/or urine among renal transplant recipients and to assess the effects of different therapeutic modalities in renal transplant recipients with BK nephropathy.

MATERIALS AND METHODS

Kidney transplant recipients were screened at the time of transplant and then at 1, 2, 3, 6, 9, 12, 18, and 24 months posttransplant. Fiftynine patients were diagnosed with BK virus viremia. Patients were divided into 2 groups according to treatment: group 1 (n = 29) received an active treatment and group 2 (n = 30) received minimized immunosuppression.

RESULTS

Most patients required graft biopsies to confirm diagnosis (86.2% in group 1 vs 50% in group 2; P = .03). Both groups were comparable regarding demographic data. Initial posttransplant graft function was significantly better in group 1 (P = .017); ultimately, there was no significant difference between both groups regarding graft survival (P= .51). Fifty percent of patients had biopsy-proven acute T-cell-mediated rejection before BK virus-associated nephropathy diagnosis (significantly higher in group 1). Serum creatinine levels were significantly better in group 2 at 3, 4, and 5 years after BK nephropathy (P = .001, .017, and .003, respectively).

CONCLUSIONS

The prevalence of BK nephropathy in our renal transplant recipients was 5.9% with a rate of graft loss ranging from 43% to 51%. Regular screening, less intensive immunosuppressive therapy, and early intervention by reduction of immunosuppressive medications are advisable to obtain early diagnosis and to have better outcomes of BK virus-associated nephropathy with antiviral agents.

Polyomavirus Nephropathy in Kidney Transplantation

Polyomavirus nephropathy has become an important complication in kidney transplantation, with a prevalence of 1% to 8%. Unfortunately, the risk factors for polyomavirus nephropathy and renal allograft loss are not well defined. The definitive diagnosis is made through assessment of a kidney transplant biopsy. Recently, noninvasive urine and serum markers have been used to assist in polyomavirus nephropathy diagnosis and monitoring. Primary treatment is immunosuppression reduction, but must be balanced with the risks of rejection. No antiviral treatments for polyomavirus nephropathy have been approved by the Food and Drug Administration. Although cidofovir has shown in vitro activity against murine polyomaviruses, and has been effective in some patients, it is associated with significant nephrotoxicity. Graft loss due to polyomavirus nephropathy should not be a contraindication to retransplantation; however, experience is limited. This review presents potential risk factors, screening, diagnostic and monitoring methods, therapeutic management, and retransplantation experience for polyomavirus nephropathy.

Place of mTOR inhibitors in management of BKV infection after kidney transplantation

CONTEXT

BK virus (BKV) viremia and BKV-associated nephropathy (BKVAN) have become a serious nuisance to kidney transplant (KT) patients since the mid-nineties, when the incidence of this disease has increased significantly.

EVIDENCE ACQUISITION

Directory of open access journals (DOAJ), EMBASE, Google Scholar, PubMed, EBSCO, and Web of Science have been searched.

RESULTS

Many hypothesis have been made as to why this phenomenon has developed; it is of general opinion that a more potent immunosuppression is at the core of the problem. The use of the association of tacrolimus (TAC) with mycophenolic acid (MPA) has gained momentum in the same years as the increase in BKV viremia incidence making it seem to be the most likely culprit. m-TOR inhibitors (m-TORIs) have been shown to have antiviral properties in vitro and this fact has encouraged different transplant teams to use these agents when confronted with BKV infection (viremia or nephropathy). However, the results are mitigated. There had been conflicting results for example when converting from TAC-to sirolimus-based immunosuppression in the setting of established BKVAN.

CONCLUSIONS

In order to prevent BKV infection we have to minimize to some extent immunosuppression, but it is not always possible, e.g. in high immunological risk patients. Conversely, we could use m-TORIs associated with low-dose calcineurin inhibitors (CNIs). This could be actually the key to a safe immunosuppression regimen both from the immunological stand point and from the viral one.

Renal Infections

This review discusses the various gross and histologic findings seen in renal infections due to bacteria, viruses, fungi, and mycobacteria. It is crucially important to separate infectious processes in the kidney from other inflammatory or neoplastic processes, as this will have a major impact on therapy. We describe the diagnostic features of renal infections with a specific focus on the differential diagnosis and other processes that may mimic infection. The topics discussed include acute bacterial pyelonephritis, chronic bacterial pyelonephritis, xanthogranulomatous pyelonephritis, malacoplakia, viral infections in the kidney, fungal pyelonephritis and mycobacterial infection of the kidney.

Transient versus persistent BK viremia and long-term outcomes after kidney and kidney-pancreas transplantation

BACKGROUND AND OBJECTIVES

The objective was to study the long-term impact of transient versus persistent BK viremia on kidney transplant outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In total, 609 recipients who underwent kidney transplant from 2007 to 2011 were screened at months 1-12 for the occurrence of polyomavirus BK viremia; 130 patients (21.7%) developed BK viremia during the first year post-transplant. BK viremia patients were classified according to duration of infection (more or less than 3 months), and BK viral loads (more or less than 10,000 copies/ml) were classified as transient low viremia (n=42), transient high viremia (n=18), persistent low viremia (n=23), and persistent high viremia (n=47). All patients were followed a median of 36 (3-66) months. The rates of BK polyomavirus-associated nephropathy, acute rejection, and 1-year graft function were compared with the polyomavirus BK-negative control group.

RESULTS

Patient and graft survival were not significantly different among the groups. Graft function (creatinine; milligrams per deciliter) at 1 year was significantly worse in the persistent high viremia (1.75±0.6) and transient high viremia (1.85±0.7) groups compared with aviremic controls (1.47±0.4; P=0.01 and P=0.01, respectively). The incidence of BK polyomavirus-associated nephropathy was limited to the persistent high viremia group (1.3%, P<0.001). The transient high viremia (50%) and persistent high viremia (34%) groups showed significantly (P=0.01) increased incidence of acute rejection versus aviremic controls (21.5%), transient low viremia (19%), or persistent low viremia (17.3%) groups.

CONCLUSION

Low viral load BK viremia, either transient or persistent, was not associated with long-term transplant outcomes. Persistent high viremia was associated with a greater risk for BK polyomavirus-associated nephropathy and subsequent graft dysfunction. Although transient high viremia was not associated with BK polyomavirus-associated nephropathy, it was associated with worse graft function. These data support the role of surveillance for BK viremia after transplant.

Transient versus persistent BK viremia and long-term outcomes after kidney and kidney-pancreas transplantation

BACKGROUND AND OBJECTIVES

The objective was to study the long-term impact of transient versus persistent BK viremia on kidney transplant outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In total, 609 recipients who underwent kidney transplant from 2007 to 2011 were screened at months 1-12 for the occurrence of polyomavirus BK viremia; 130 patients (21.7%) developed BK viremia during the first year post-transplant. BK viremia patients were classified according to duration of infection (more or less than 3 months), and BK viral loads (more or less than 10,000 copies/ml) were classified as transient low viremia (n=42), transient high viremia (n=18), persistent low viremia (n=23), and persistent high viremia (n=47). All patients were followed a median of 36 (3-66) months. The rates of BK polyomavirus-associated nephropathy, acute rejection, and 1-year graft function were compared with the polyomavirus BK-negative control group.

RESULTS

Patient and graft survival were not significantly different among the groups. Graft function (creatinine; milligrams per deciliter) at 1 year was significantly worse in the persistent high viremia (1.75±0.6) and transient high viremia (1.85±0.7) groups compared with aviremic controls (1.47±0.4; P=0.01 and P=0.01, respectively). The incidence of BK polyomavirus-associated nephropathy was limited to the persistent high viremia group (1.3%, P<0.001). The transient high viremia (50%) and persistent high viremia (34%) groups showed significantly (P=0.01) increased incidence of acute rejection versus aviremic controls (21.5%), transient low viremia (19%), or persistent low viremia (17.3%) groups.

CONCLUSION

Low viral load BK viremia, either transient or persistent, was not associated with long-term transplant outcomes. Persistent high viremia was associated with a greater risk for BK polyomavirus-associated nephropathy and subsequent graft dysfunction. Although transient high viremia was not associated with BK polyomavirus-associated nephropathy, it was associated with worse graft function. These data support the role of surveillance for BK viremia after transplant.

BK viremia and polyomavirus nephropathy in 352 kidney transplants; risk factors and potential role of mTOR inhibition

Background

Polyomavirus BK nephropathy (PyVAN) remains an important cause of early graft dysfunction and graft loss in kidney transplantation.

Methods

In this retrospective, single centre cohort study we studied the incidence and outcome of BK viral infection in 352 patients transplanted in 2008–2011.

Results

During follow-up viral replication was detected in 48 patients (13.6%); 22 patients (6.2%) had biopsy proven PyVAN.

In multivariate logistic regression analyses risk factors for BK-viremia were lack of enrolment into randomized controlled trials (RCTs), biopsy proven acute rejections, cytomegaly virus (CMV) serostatus of both donor and recipient and previous transplantation.

In patients without PyVAN reduction or switch of immunosuppression was associated with rapid viral clearance and stable graft function. In contrast, in most patients with PyVAN graft function deteriorated and 5 patients prematurely lost their allograft. Switch of immunosuppression to a low dose cyclosporine plus mTOR inhibitor based regimen in patients with PyVAN was safe, well tolerated and tended to be associated with a better short-term outcome in terms of graft function compared to reduction of existing immunosuppression alone.

Conclusions

With the lack of licensed anti-polyoma viral drugs reduction or conversion of immunosuppression remains the mainstay of therapy in patients with PyVAN. The combination of low dose cyclosporine plus mTOR inhibition appears to be safe and warrants further investigation.

Immunophenotyping in BK virus allograft nephropathy distinct from acute rejection

Differentiating BK virus nephropathy (BKVN) from acute rejection (AR) is crucial in clinical practice, as both of them have interstitial inflammation in the grafts. The purpose of the study is to describe the inflammatory cellular constituents of BKVN and to determine the clinical utility of immunophenotyping findings in distinguishing BKVN from AR. In addition, the expression of the HLA-DR was investigated. Sixty-five renal allograft recipients were included in this study, including 22 cases of BKVN, 31 cases of AR, and 12 cases of stable allograft. Immunostaining for infiltrating lymphocytes showed that the number of CD20 cells (P < 0.001) and the percentages of CD3 (P < 0.001), CD4 (P = 0.004), CD8 (P = 0.005), and CD20 (P = 0.002) cells were all significantly different between BKVN and AR. Moreover, there were no statistically significant differences in tubule cell HLA-DR expression (P = 0.156). This observation suggests that the number of CD20 cells and the percentages of CD3, CD4, CD8, and CD20 cells in renal biopsies would aid the distinction between BKVN and AR. On the other hand, the presence of HLA-DR upregulation may not only be specific for acute rejection but also be a response to BKVN.

Management and outcome of BK viremia in renal transplant recipients: a prospective single-center study

BACKGROUND

BK viremia can lead to nephritis, which can progress to irreversible kidney transplant failure. Our prospective study provides management and outcome of BK viremia in renal transplant recipients.

METHODS

Two hundred forty de novo kidney-only recipients were enrolled from July 2007 to July 2010 and followed for 1 year. Standard immunosuppression with Thymoglobulin/interleukin 2 receptor blocker and mycophenolate mofetil/tacrolimus (Tac)/prednisone was employed. Quantitative BK virus (BKV) DNA surveillance in plasma/urine was performed at 1, 3, 6, 12, and 24 months after transplantation. Patients with significant viremia (defined as ≥10,000 viral copies/mL) underwent renal biopsy and treated with 30% to 50% reduction in doses of both mycophenolate mofetil and Tac without antiviral therapy. The target 12-hr Tac trough levels were lowered to 4 to 6 ng/mL in the significant viremia group, whereas the target levels remained unchanged at 5 to 8 ng/mL for all other groups.

RESULTS

Sixty-five patients (27%) developed BK viremia; 28 (12%) of whom had significant viremia. A total of five (21%) of the 23 (of 28) patients who underwent biopsy presented with subclinical BKV nephritis. The mean plasma BKV DNA declined by 98% (range, 76%-100%) at 1 year after peak viremia. Acute cellular rejection seen in four (14%) of 28 patients, responded to bolus steroids. There was no decline in estimated glomerular filtration rate over time from 1 month after transplantation to 1 year after peak viremia (P=0.57).

CONCLUSION

Reduction in immunosuppression alone resulted in the successful resolution of viremia with preservation of renal function and prevention of clinical BKV nephritis and graft loss.

Lower prevalence of BK virus infection in African American renal transplant recipients: a prospective study

BACKGROUND

Because the occurrence of BK virus (BKV) nephritis is far less frequent than BK viremia or viruria, analysis of risk factors for BKV nephritis as an endpoint could lead to erroneous findings. We undertook a prospective study to evaluate the risk factors for the occurrence of BKV infections using BK viruria and viremia as endpoints.

METHODS

Two hundred forty renal only transplant recipients were prospectively enrolled into our institutional review board-approved single center study to evaluate various aspects of posttransplant BKV infection. All patients were followed up for a minimum of 6 months posttransplant.

RESULTS

Of the 240 subjects, 154 were whites, 61 African Americans, and 25 belonged to other races. A total of 94 developed BKV infection (any degree of BK viruria or viremia) whereas 146 developed no infection. Among these, 33 had BK viruria alone, 61 had BK viremia with viruria and 25 had significant viremia defined as BKV DNA more than 10,000 copies/mL of plasma. Lower proportion of African Americans developed BKV infection, 14 of 61 (23%), as opposed to whites, 67 of 154 (47%). Logistic regression model showed lower risk of any BKV infection in African American recipient race (OR, 0.38; 95% CI, 0.17-0.82; P=0.016) and higher risk of significant BKV infection with occurrence of acute rejection (OR, 3.9; 95% CI, 1.31-11.8; P=0.015). The Kaplan-Meier analysis shows a trend toward greater freedom from BKV infection in African Americans as opposed to other racial groups (P=0.33).

CONCLUSION

Renal transplant recipients of African American race had a lower risk of posttransplant BKV infection compared with whites, independent of other confounding risk factors.

Polyomavirus nephropathy: a current perspective and clinical considerations

During the last decade, the human polyomaviruses (BK virus and, much less commonly, JC virus) have entered the realm of routine clinical decision making for providers caring for kidney transplant recipients. The emergence of polyomavirus-associated nephropathy (PVAN) as an important clinical entity coincided with the development and use of more potent immunosuppression agents, currently the only clear risk factor for reactivation of the virus. Ongoing efforts to define the pathogenesis, clinical presentation, and appropriate management of PVAN have led to a greater ability to prevent and control viral-induced interstitial nephritis despite continued deficiencies in our understanding of risk factors for disease and lack of published prospective polyomavirus-specific antiviral trials. The purpose of this review is to summarize advances made during the last decade and highlight emerging data that address common clinical considerations the clinician currently faces in the understanding and management of PVAN.

Risk factors for polyoma virus nephropathy

BACKGROUND

Polyoma virus-associated nephropathy (PVN) is a common cause of renal transplant failure. The risk factors for the development of PVN have not yet been studied in large cohorts of patients for periods of 20 years.

METHODS

We collected clinical, renal biopsy and urinary cytology data from all patients with renal transplantations performed at the University Hospital of Basel from 1985 to 2005. All patients with a renal biopsy and urine cytology were included (n = 880). Renal transplants were divided into three groups, according to evidence of polyoma virus (PV) infection (decoy cells in the urine) and biopsy-proven PVN: Renal transplants without evidence of a PV infection (n = 751). Renal transplants with PV reactivation, e.g. decoy cell (DC) found by urinary cytology, but without PVN (n = 90). Renal transplants with PVN (n = 39).

RESULTS

The prevalence of biopsy-proven PVN in this cohort of patients was 3.3%. Immunosuppression with mycophenolate and/or tacrolimus, ATGAM, male gender of the recipient and a higher number of transplant rejection episodes were factors significantly associated with PVN development.

CONCLUSIONS

The most important risk factors for the development of PVN are acute rejection and ATGAM used as induction therapy as well as tacrolimus and mycophenolate as maintenance therapy. Therefore, we conclude that patients with tacrolimus and mycophenolate maintenance therapy should be carefully monitored for the development of PVN.

The effect of low-dose cidofovir on the long-term outcome of polyomavirus-associated nephropathy in renal transplant recipients

BACKGROUND

Polyomavirus-associated nephropathy (PVAN) has an unfavourable impact on graft survival. The cornerstone of therapy is early reduction of immunosuppressive medications; however, the rate of graft failure is still high. Antiviral drugs, such as cidofovir, are thought to have therapeutic effects, but the benefits of cidofovir in retarding the deterioration of PVAN are still a controversial issue.

METHODS

Fourteen renal kidney recipients were diagnosed to have biopsy-proven PVAN between 2001 and 2006 in Chung-Shan Medical University Center with nearly 600 renal transplant recipients. After the diagnosis of PVAN, all patients were treated with a reduction of their original immunosuppressive medications with/without converting tacrolimus to cyclosporine. Eight of the 14 patients agreed to receive low-dose cidofovir (0.5 mg/kg) every 2 weeks for a total of six doses.

RESULTS

During 30 +/- 18 months of follow-up, three (37%) patients in the cidofovir-treated and three (50%) patients in the non-cidofovir-treated group experienced graft loss (P = 0.64). The rejection rate before PVAN diagnosis or other baseline characteristics of the patients between two groups were not significantly different. The long-term survival rate to graft loss and major graft functional decline with Kaplan-Meier analysis between the two groups were not significantly different (P = 0.898 and P = 0.243). In all demographic and clinical characteristics, we found that there was a tendency towards long-term major graft functional decline in the patients with acute rejection prior to PVAN diagnosis (P = 0.04).

CONCLUSIONS

We concluded that (1) there was no obvious effect of low-dose cidofovir on long-term graft survival in patients with PVAN, and (2) acute rejection prior to PVAN diagnosis was a potential risk factor for poorer long-term graft outcome.

Early diagnosis of polyomavirus type BK infection in tailoring immunosuppression for kidney transplant patients: screening with urine qualitative polymerase chain reaction assay

Polyomavirus type BK (BKV) nephropathy is increasingly a significant cause of graft dysfunction and even failure. Early diagnosis followed by reduction of immunosuppression has been associated with an improved prognosis. We screened 250 patients with the urine qualitative polymerase chain reaction (PCR) for BKV DNA. We followed with blood BKV PCR if the urine screen was positive and then reduced immunosuppression in viremic patients. One hundred ninety-nine patients (80%) had no viuria; 43 (17%) viuria; and 8 (3%) both viuria and viremia. Graft biopsy performed in three patients (1%) with viremia and impaired graft function all revealed BKV nephropathy. After 6 months of follow-up, seven out of eight viremic patients (88%) had negative repeat blood PCR and stabilized graft function. An early diagnosis of BKV infection with reduction of immunosuppression may reverse viremia and retard progression of BKV nephropathy. BKV screening by PCR assays should be considered in kidney transplant recipients, especially those with impaired graft function.

BK virus nephritis after renal transplantation

BK virus nephritis is an increasing problem and is posing a threat to improving renal transplant graft survival. The pathogenesis of this condition remains to be investigated. Higher prevalence of BK virus infection in recent years has been correlated with declining acute rejection rates and the use of potent immunosuppressive agents. Patients with this infection usually have asymptomatic viremia and/or nephritis with or without worsening of renal function. The diagnosis of this disease is based on detecting the virus or its effects in urine, blood, and renal tissue. In the past, approximately 30 to 60% of patients with BK virus nephritis developed graft failure. In recent years, the combination of early detection, prompt diagnosis, and therapies including preventive measures have resulted in better outcomes.

BK virus nephropathy and kidney transplantation

Nephropathy from BK virus (BKV) infection is an evolving challenge in kidney transplant recipients. It is the consequence of modern potent immunosuppression aimed at reducing acute rejection and improving allograft survival. Untreated BKV infections lead to kidney allograft dysfunction or loss. Decreased immunosuppression is the principle treatment but predisposes to acute and chronic rejection. Screening protocols for early detection and prevention of symptomatic BKV nephropathy have improved outcomes. Although no approved antiviral drug is available, leflunomide, cidofovir, quinolones, and intravenous Ig have been used. Retransplantation after BKV nephropathy has been successful.

Clinical utility of histological features of polyomavirus allograft nephropathy

BACKGROUND

The purpose of this study was to determine if histological features of polyomavirus allograft nephropathy (PVAN) are associated with the clinical presentation and outcomes of PVAN.

METHODS

We examined the histological features of initial and follow-up biopsies of 20 kidney and kidney-pancreas transplant recipients with PVAN during a time prior to routine surveillance. The subjects' demographics, clinical characteristics, and outcomes were compared based upon classification of histological features of PVAN on initial biopsy.

RESULTS

Diabetes mellitus (45%) and a history of tacrolimus-induced nephrotoxicity (35%) appeared to be prevalent in subjects with PVAN. Although histological severity of PVAN did not predict or correlate with the clinical course of PVAN, subjects with pattern C on initial PVAN biopsy presented later posttransplant, had higher serum creatinine level at presentation, and had significant allograft deterioration at follow-up than subjects with either pattern A or B on initial biopsy. Resolution of PVAN was noted in 60% of follow-up biopsies and occurred more frequently in subjects with pattern B on initial biopsy. Most subjects developed chronic allograft nephropathy after PVAN and viral clearance did not abrogate the progression to chronic allograft nephropathy.

CONCLUSIONS

These data indicate that histologic patterns of PVAN may have clinical correlation to disease presentation and prognosis.

Pharmacotherapeutic options for the management of human polyomaviruses

Polyomaviruses [BK virus (BKV), JC virus (JCV) and simian virus 40 (SV40)] have been known to be associated with diseases in humans for over thirty years. BKV-associated nephropathy and JCV-induced progressive multifocal leukoencephalopathy (PML) were for many years rare diseases occurring only in patients with underlying severe impaired immunity. Over the past decade, the use of more potent immunosuppression (IS) in transplantation, and the Acquired Immune Deficiency Syndrome (AIDS) epidemic, have coincided with a significant increase in the prevalence of these viral complications. Prophylactic and therapeutic interventions for human polyomavirus diseases are limited by our current understanding of polyomaviral pathogenesis. Clinical trials are limited by small numbers of patients affected with clinically significant diseases, lack of defined risk factors and disease definitions, no proven effective treatment and the overall significant morbidity and mortality associated with these diseases. This chapter will focus on a review of the current and future research related to therapeutic targets and interventions for polyomavirus-associated diseases.

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.

BK virus nephritis: risk factors, timing, and outcome in renal transplant recipients

BACKGROUND

BK virus nephritis (BKVN) has emerged as an important cause of renal transplant failure. Quantified analysis of its timing and clinical course is generally lacking. We have thus quantified the timing, risk factors, evolution of renal function, and transplant graft outcome in renal transplant recipients with BKVN from our center.

METHODS

A total of 41 cases of BKVN were diagnosed in 1001 renal and renal/pancreas transplant recipients. There were 2 groups: group I (N= 16), with diagnosis based on renal biopsy alone from January 1996 to August 2001, and group II (N= 25), with diagnosis based on quantitative blood BKV-PCR and biopsy from September 2001 to December 2003. The demographics, the clinical course, immunosuppressive therapy, renal function, and graft outcome were quantified. Donor, recipient, and transplant risk variables were studied using a univariate analysis. Actuarial graft survival was calculated. An immunosuppressive scale created to evaluate the degree of immunosuppression in these patients and its reduction after the diagnosis of BKVN.

RESULTS

The median time from transplant to BKVN diagnosis was 318 days (range 48-1356). The actuarial graft survival in patients with BKVN at 6 months, 1, 3, and 5 years was 97%, 90%, 58%, and 47%. The corresponding values for those without BKVN were 94%, 92%, 83%, and 76%, respectively, P < 0.001. Graft loss occurred in 46% of patients. The rate of decline of renal function in group II (N= 25) patients in the 4 months preceding BKVN was rapid (4.8 mL/min/month) and this declined to 0.7 mL/min/month at 3 months' post-BKVN diagnosis, P= 0.004. In those who recovered, the time to stabilization of renal function was a median of 112 days. The immunosuppressive scale score was 7 units at the time of diagnosis of BKVN and decreased to 3.5 units at 3 months' post-BKVN. Reduction in the dose of calcineurin inhibitors but not the overall reduction in dose of immunosuppression correlated with recovery of renal function in these patients.

CONCLUSION

BKVN is a relatively late complication of renal transplantation. Despite reduction in immunosuppression, graft loss occurred in 46% of patients. There was a steep decline in renal function in months preceding the diagnosis of BKVN, and reduction in calcineurin inhibitor dose, but not overall immunosuppression, correlated with stabilization of renal function.

BK virus-specific antibodies and BKV DNA in renal transplant recipients with BKV nephritis

We evaluated twenty renal transplant subjects at various stages of BKV nephritis (BKVN) for BKV-specific IgG and IgM antibodies using ELISA technique and BKV-DNA using PCR. They were divided as early onset (n = 7), stabilizing (n = 3), resolved (n = 8) and late onset (n = 2) BKVN. BKV-specific antibodies and BKV-DNA were simultaneously determined. The mean BKV-specific IgG level in early onset and stabilizing BKVN were 64 and 39 EIA units, and were significantly lower than 138 EIA units seen in resolved BKVN, P = 0.007, P = 0.008. The mean BKV-specific IgM levels in stabilizing BKVN was higher than resolved BKVN (130 vs 51 EIA units), P = 0.006. Mean plasma BKV loads for each group were 955,925, 5642 and 42 copies/mL of plasma, respectively. Prospective study in six BKVN cases revealed mean IgG, IgM levels and BKV-DNA at the time of diagnosis of BKVN as 39, 110 EIA units and 586,758 copies/mL of plasma, respectively. After a mean period of 5.2 months, IgG level increased to 120 EIA units (p = 0.0058) and had no detectable viral copies in circulation. Recovery from BKVN and elimination of BKV is associated with the development of BKV-specific IgG antibodies and this provides insight into the role of humoral immunity to BKV in the pathogenesis of BKVN.

Polyomavirus-associated nephropathy in renal transplantation: interdisciplinary analyses and recommendations

Polyomavirus-associated nephropathy (PVAN) is an emerging cause of kidney transplant failure affecting 1-10% of patients. As uncertainty exists regarding risk factors, diagnosis, and intervention, an independent panel of experts reviewed the currently available evidence and prepared this report. Most cases of PVAN are elicited by BK virus (BKV) in the context of intense immunosuppression. No specific immunosuppressive drug is exclusively associated with PVAN, but most cases reported to date arise while the patient is on triple immunosuppressive combinations, often comprising tacrolimus and/or mycophenolate mofetil plus corticosteroids. Immunologic control of polyomavirus replication can be achieved by reducing, switching, and/or discontinuing components of the immunosuppressive regimen, but the individual's risk of rejection should be considered. The success rate of this intervention is increased with earlier diagnosis. Therefore, it is recommended that all renal transplant recipients should be screened for BKV replication in the urine: 1) every three months during the first two years posttransplant; 2) when allograft dysfunction is noted; and 3) when allograft biopsy is performed. A positive screening result should be confirmed in <4 weeks and assessed by quantitative assays (e.g. BKV DNA or RNA load in plasma or urine). Definitive diagnosis of PVAN requires allograft biopsy. If PVAN and concurrent acute rejection is diagnosed, antirejection treatment should be considered, coupled with subsequently reducing immunosuppression. The antiviral cidofovir is not approved for PVAN, but investigational use at low doses (0.25-0.33 mg/kg intravenously biweekly) without probenicid should be considered for refractory cases. Retransplantation after renal allograft loss to PVAN remains a treatment option for patients clearing polyomavirus replication.

BK virus nephropathy in a patient with ABO-incompatible renal transplantation

A 43-year-old woman with end-stage renal disease originating from IgA nephropathy entered chronic haemodialysis therapy. She then received an ABO-incompatible living related renal transplantation. Initial immunosuppression consisted of azathioprine, methylprednisolone and tacrolimus. At 155 days after transplantation, the azathioprine was changed to mycophenolate mofetil for continuous graft dysfunction. Furthermore, a total of three courses of anti-rejection therapy was given. At 665 days after transplantation, diagnosis of BK-virus nephropathy was made by immunohistochemical analysis and viral DNA assay. Therefore the immunosuppression therapy was reduced for graft dysfunction. All five renal biopsy specimens were examined retrospectively in order to determine when the BK virus nephropathy had developed. The expressions of SV40 large T antigens were detected from the third (117 days) to the fifth (665 days) biopsies, with increasing numbers of SV40 large T antigen positive cells. In addition, many cells contained inclusion bodies which were already present in the urinary sediment for 3 months post-transplantation. Although it is difficult to make a diagnosis of early stage of BKVN, we have to consider with caution if urinary cells with inclusion body are seen. Awareness of BKVN at the earliest opportunity is important in order to avoid over-immunosuppression.

Polyomavirus nephropathy in kidney transplantation

Polyomavirus nephropathy has become an important complication in kidney transplantation, with a prevalence of 1% to 8%. Unfortunately, the risk factors for polyomavirus nephropathy and renal allograft loss are not well defined. The definitive diagnosis is made through assessment of a kidney transplant biopsy. Recently, noninvasive urine and serum markers have been used to assist in polyomavirus nephropathy diagnosis and monitoring. Primary treatment is immunosuppression reduction, but must be balanced with the risks of rejection. No antiviral treatments for polyomavirus nephropathy have been approved by the Food and Drug Administration. Although cidofovir has shown in vitro activity against murine polyomaviruses, and has been effective in some patients, it is associated with significant nephrotoxicity. Graft loss due to polyomavirus nephropathy should not be a contraindication to retransplantation; however, experience is limited. This review presents potential risk factors, screening, diagnostic and monitoring methods, therapeutic management, and retransplantation experience for polyomavirus nephropathy.

Polyomavirus BK

Polyomavirus hominis 1, better known as BK virus (BKV), infects up to 90% of the general population. However, significant clinical manifestations are rare and limited to individuals with impaired immune functions. BKV has been associated with diverse entities such as haemorrhagic cystitis, ureteric stenosis, vasculopathy, pneumonitis, encephalitis, retinitis, and even multi-organ failure. In addition, BKV has been implicated in autoimmune disease and possibly cancer. Due to high prevalence and frequent reactivation, the role of BKV in some of these pathologies has been difficult to define. Development of BKV diseases is likely to require complementing determinants in the host, the target organ, and possibly the virus, that are subject to modulators such as immunosuppression. These complex aspects are highlighted in polyomavirus-associated nephropathy (PAN), an emerging disease in renal allograft recipients that may jeopardise the progress in renal transplantation accomplished in the past 10 years. Intervention is difficult due to the lack of specific antivirals and relies mostly on improving immune control. Diagnostic strategies using urine cytology and BKV load measurements in plasma have led to earlier diagnosis of PAN, which increased the success rate of intervention. Case series suggest that cidofovir might be effective, especially when combined with reduced immunosuppression.

Polyomavirus in kidney and kidney-pancreas transplant recipients

PURPOSE

To report the incidence and clinical characteristics of polyomavirus (PV) nephritis in kidney (KTX) and kidney-pancreas transplant (KPTX) recipients.

METHODS

Single center retrospective analysis of all cases of PV nephritis in KTX and KPTX patients transplanted between 1994 and 1999.

RESULTS

Thirteen (5 KTX and 8 KPTX) patients (2.1%) had PV nephritis diagnosed on multiple biopsies (n = 22) among 504 KTX and 106 KPTX recipients. The incidence of PV nephritis was higher in cadaver donor transplants (2.6% cadaver vs. 0.7% living donors), after KPTX (1% KTX vs. 7.5% KPTX), in males (3.3% male vs. 0.7% female), and in diabetic patients (4.4% diabetic vs. 0.8% nondiabetic). The mean time to diagnosis of PV nephritis was 18 (range 6-48) months after KTX and 17 (range 9-31) months after KPTX. Three KTX patients and 5 KPTX patients had calcineurin inhibitor toxicity on biopsy prior to developing PV nephritis. Reduction in immunosuppression occurred in 100% of KTX and 63% of KPTX patients. Three patients (23%) developed rejection within 3 months of diagnosis of PV, 1 after a reduction in immunosuppression. Despite multiple antiviral treatment regimens, renal allograft failure requiring dialysis occurred in 60% of KTX and 50% of KPTX patients. All KPTX patients remain insulin independent and 2 were successfully retransplanted with living donor kidneys. 2 patients (15%) died but there was no mortality directly related to the virus.

CONCLUSIONS

Polyomavirus nephritis may be increasing in incidence and appears to be unresponsive to either conventional antiviral agents or a reduction in immunosuppression. Most of our cases occurred in male diabetic patients undergoing cadaveric donor transplantation and were preceded by biopsy-proven nephrotoxicity. Further studies are needed to better define the pathogenesis of PV and effective antiviral treatment.

Polyomavirus BK nephropathy: a (re-)emerging complication in renal transplantation

Persisting polyomavirus replication is now widely recognized as a (re-)emerging cause of renal allograft dysfunction. Up to 5% of renal allograft recipients can be affected about 40weeks (range 6-150) post-transplantation. Progression to irreversible failure of the allograft has been observed in up to 45% of all cases. The BK virus strain is involved in the majority of the cases. Risk factors may include treatment of rejection episodes and increasing viral replication under potent immunosuppressive drugs such as tacrolimus, sirolimus or mycophenolate. The diagnosis requires the histological demonstration of nuclear polyomavirus inclusions in affected tubular epithelial cells. Interstitial inflammatory infiltrates and fibrosis become more prominent in the persisting disease and may be difficult to distinguish from (coexisting) rejection. Detection of polyomavirus-inclusion bearing cells ('decoy cells') in the urine and quantification of BK virus DNA in the plasma have been proposed as surrogate markers for polyomavirus replication and allograft disease, respectively. Antiviral treatment is not yet established; however, reports of treatment with cidofovir are encouraging. Current management aims at the judicious modification and/or reduction of immunosuppression which, in view of preceding or concurrent rejection, is not without risk.