Aggressive immunosuppression minimization reduces graft loss following diagnosis of BK virus-associated nephropathy: a comparison of two reduction strategies

Brincidofovir inhibits polyomavirus infection in vivo

Polyomaviruses are species-specific DNA viruses that can cause disease in immunocompromised individuals. Despite their role as the causative agents for several diseases, there are no currently approved antivirals for treating polyomavirus infection. Brincidofovir (BCV) is an antiviral approved for the treatment of poxvirus infections and has shown activity against other double-stranded DNA viruses. In this study, we tested the efficacy of BCV against polyomavirus infection in vitro and in vivo using mouse polyomavirus (MuPyV). BCV inhibited virus production in primary mouse kidney cells and brain cortical cells. BCV treatment of cells transfected with MuPyV genomic DNA resulted in a reduction in virus levels, indicating that viral inhibition occurs post-entry. Although in vitro BCV treatment had a limited effect on viral DNA and RNA levels, drug treatment was associated with a reduction in viral protein, raising the possibility that BCV acts post-transcriptionally to inhibit MuPyV infection. In mice, BCV treatment was well tolerated, and prophylactic treatment resulted in a reduction in viral DNA levels and a potent suppression of infectious virus production in the kidney and brain. In mice with chronic polyomavirus infection, therapeutic administration of BCV decreased viremia and reduced infection in the kidney. These data demonstrate that BCV exerts antiviral activity against polyomavirus infection in vivo, supporting further investigation into the use of BCV to treat clinical polyomavirus infections.

IMPORTANCE

Widespread in the human population and able to persist asymptomatically for the life of an individual, polyomavirus infections cause a significant disease burden in the immunocompromised. Individuals undergoing immune suppression, such as kidney transplant patients or those treated for autoimmune diseases, are particularly at high risk for polyomavirus-associated diseases. Because no antiviral agent exists for treating polyomavirus infections, management of polyomavirus-associated diseases typically involves reducing or discontinuing immunomodulatory therapy. This can be perilous due to the risk of transplant rejection and the potential development of adverse immune reactions. Thus, there is a pressing need for the development of antivirals targeting polyomaviruses. Here, we investigate the effects of brincidofovir, an FDA-approved antiviral, on polyomavirus infection in vivo using mouse polyomavirus. We show that the drug is well-tolerated in mice, reduces infectious viral titers, and limits viral pathology, indicating the potential of brincidofovir as an anti-polyomavirus therapeutic.

Incidence and Outcomes of BK Virus Nephropathy in Kidney Transplant Recipients With Steroid-Free Maintenance Immunosuppression

BACKGROUND

BK virus nephropathy (BKVN) is a significant complication in kidney transplant recipients, resulting in graft dysfunction and potentially leading to graft loss. This study aims to investigate the incidence and outcomes of BKVN in kidney transplant recipients receiving steroid-free maintenance immunosuppression in a Latin -American cohort.

METHODS

Case series study of BKVN among kidney transplant recipients who underwent transplantation between 2008 and 2023. The primary outcome was graft loss caused by BKVN, excluding death with function. Secondary outcomes included graft function and acute rejection episodes. The statistical analysis involved descriptive statistics and the Kaplan-Meier (K-M) method to plot the overall probabilities of not initiating dialysis.

RESULTS

During the 15-year period, 2236 kidney transplants were performed, BKVN was histologically diagnosed in 38 kidney recipients and 33 cases were analyzed. Median age was 50 years and men were 48.5% of patients. A total of 45.4% of BKVN occurred within the first 12 months of transplant. The incidence of BKVN was 1.6% but it varied by era. The rate of graft loss was 75.7% (25 cases). The K-M graft survival probability at 6 months and 12 months after diagnosis of BKVN was 38.3% (95% CI 24.7-59.4) and 22.3% (95% CI 11.7-42.8), respectively.

CONCLUSION

BKVN affected 1.6% of transplant recipients and it was associated with high-rate of graft loss. We observed that significant graft disfunction at the time of diagnosis resulted in worse outcomes with a reduced probability of graft survival.

Incidence, risk factors, outcomes, and clinical management of BK viremia in the modern era of kidney transplantation

BK viremia is endemic among kidney transplant recipients (KTRs). Incidence, risk factors, outcomes, and clinical management of detectable versus high BK viremia have not been considered previously in KTR in the modern era. This observational study examined KTR transplanted between January 1, 2009 and December 31, 2016. Any BK viral load in the serum constituted detectable BK viremia and ≥10³ copies/ml constituted high viremia. Among 1193 KTRs, the cumulative probability of developing detectable and high BK viremia within 2 years posttransplant were 27.8% and 19.6%, respectively. Significant risk factors for detectable BK viremia included recipient age (HR 1.02 [95% CI: 1.01, 1.03]) and donor age (HR 1.01 [95% CI: 1.00, 1.02]). Recipient age also predicted high BK viremia (HR 1.02 [95% CI: 1.01, 1.03]), whereas White race (HR 0.70 [95% CI: 0.52, 0.95]), nondepleting induction therapy (HR 0.61 [95% CI: 0.42, 0.89]), and delayed graft function (HR 0.61 [95% CI: 0.42, 0.88]) were protective. Mean estimated glomerular filtration rates were 4.28 ml/min/1.72 m² (95% CI: 2.71, 5.84) lower with detectable BK viremia. Although low viral load was usually not acted upon at first presentation, antiproliferative dose reductions were the most common initial management. BK viremia remains a common early complication in a modern cohort of KTRs. These findings highlight the benefit of early BKV monitoring in addition to intensive clinical management. Clinical responses beyond first positive BK viremia tests, and their implications for graft outcomes, merit further investigation.

In Vitro Study Evaluating the Effect of Different Immunosuppressive Agents on Human Polyomavirus BK Replication

BACKGROUND

Human polyomavirus BK (BKPyV) is the etiologic agent of polyomavirus-associated nephropathy, a leading cause of kidney transplant dysfunction. Because of the lack of antiviral therapies, immunosuppression minimization is the recommended treatment. This strategy offers suboptimal outcomes and entails a significant risk of rejection. Our aim was to evaluate the effect of different immunosuppressive drugs (leflunomide, tacrolimus, mycophenolic acid, sirolimus, and everolimus) and their combinations in an in vitro model of BKPyV infection.

METHODS

Human renal tubular epithelial cells were infected with BKPyV and treated with leflunomide, tacrolimus, mycophenolic acid, sirolimus, and everolimus, administered alone or in some combination thereof. Viral replication was assessed every 24 hours (up to 72 hours) by BKPyV-specific quantitative real-time polymerized chain reaction for the VIRAL PROTEIN 1 sequence in cell supernatants and by western blot analysis targeting the viral protein 1 and the glyceraldehyde 3-phosphate dehydrogenase on total protein lysates. Results were described as viral copies/mL and compared between treatments at any prespecified time point of the study.

RESULTS

The highest inhibitory effects were observed using leflunomide or everolimus plus mycophenolic acid (mean BKPyV replication log reduction 0.28). The antiviral effect of everolimus persisted when it was used in combination with tacrolimus (mean BKPyV replication log reduction 0.27).

CONCLUSIONS

Our experience confirms that everolimus has anti-BKPyV properties and prompts future research to investigate possible mechanisms of action. It also provides a rational basis for targeted clinical trials evaluating alternative immunosuppressive modification strategies.

Economic Evaluation of Screening for Polyomavirus Infection in Kidney Transplant Recipients: A Cost-Utility Analysis

Screening for polyomavirus infection after kidney transplantation is recommended by clinical practice guidelines, but cost-effectiveness of this strategy is uncertain. The aim of this study was to estimate the incremental costs and benefits of routine screening for polyomavirus infection compared with no screening in kidney transplant recipients.

Polyoma BK Virus in Kidney Transplant Recipients: Screening, Monitoring, and Management

Polyomavirus BK virus (BKPyV) infection is an important complication of kidney transplantation and allograft failure. The prevalence of viremia is 10%-15%, compared with BK-associated nephropathy (BKPyVAN) at 3%-5%. Given that there are no effective antiviral prophylaxis or treatment strategies for BKPyVAN, active screening to detect BKPyV viremia is recommended, particularly during the early posttransplant period. Immunosuppression reduction to allow viral clearance may avoid progression to severe and irreversible allograft damage. The frequency and duration of screening are highly variable between transplant centers because the evidence is reliant largely on observational data. While the primary treatment goals center on achieving viral clearance through immunosuppression reduction, prevention of subsequent acute rejection, premature graft loss, and return to dialysis remain as major challenges. Treatment strategies for BKPyV infection should be individualized to the recipient's underlying immunological risk and severity of the allograft infection. Efficacy data for adjuvant therapies including intravenous immunoglobulin and cidofovir are sparse. Future well-powered and high-quality randomized controlled trials are needed to inform evidence-based clinical practice for the management of BKPy infection.

Chk1 and the Host Cell DNA Damage Response as a Potential Antiviral Target in BK Polyomavirus Infection

The human BK polyomavirus (BKPyV) is latent in the kidneys of most adults, but can be reactivated in immunosuppressed states, such as following renal transplantation. If left unchecked, BK polyomavirus nephropathy (PyVAN) and possible graft loss may result from viral destruction of tubular epithelial cells and interstitial fibrosis. When coupled with regular post-transplant screening, immunosuppression reduction has been effective in limiting BKPyV viremia and the development of PyVAN. Antiviral drugs that are safe and effective in combating BKPyV have not been identified but would be a benefit in complementing or replacing immunosuppression reduction. The present study explores inhibition of the host DNA damage response (DDR) as an antiviral strategy. Immunohistochemical and immunofluorescent analyses of PyVAN biopsies provide evidence for stimulation of a DDR in vivo. DDR pathways were also stimulated in vitro following BKPyV infection of low-passage human renal proximal tubule epithelial cells. The role of Chk1, a protein kinase known to be involved in the replication stress-induced DDR, was examined by inhibition with the small molecule LY2603618 and by siRNA-mediated knockdown. Inhibition of Chk1 resulted in decreased replication of BKPyV DNA and viral spread. Activation of mitotic pathways was associated with the reduction in BKPyV replication. Chk1 inhibitors that are found to be safe and effective in clinical trials for cancer should also be evaluated for antiviral activity against BKPyV.

Advances in BK Virus Complications in Organ Transplantation and Beyond

Reactivation of BK virus (BKV) remains a dreaded complication in immunosuppressed states. Conventionally, BKV is known as a cause for BKV-associated nephropathy and allograft dysfunction in kidney transplant recipients. However, emerging studies have shown its negative impact on native kidney function and patient survival in other transplants and its potential role in diseases such as cancer. Because BKV-associated nephropathy is driven by immunosuppression, reduction in the latter is a convenient standard of care. However, this strategy is risk prone due to the development of donor-specific antibodies affecting long-term allograft survival. Despite its pathogenic role, there is a distinct lack of effective anti-BKV therapeutics. This limitation combined with increased morbidity and health care cost of BKV-associated diseases add to the complexity of BKV management. While summarizing recent advances in the pathogenesis of BKV-associated nephropathy and its reactivation in other organ transplants, this review illustrates the limitations of current and emerging therapeutic options and provides a compelling argument for an effective targeted anti-BKV drug.

BK viremia and nephropathy in pediatric renal transplant recipients

The renal survival rate of pediatric renal transplant recipients (pRTR) has improved with the use of modern immunosuppressive agents; however, the incidence of post-transplantation viral infection has increased. This study investigated the incidence of BK viremia and BK viral-associated nephropathy (BKVAN) in pRTR. One-hundred-and-thirty-four pRTR were divided into two groups: group 1 (n = 20, 14.9%) comprised those who were prospectively followed with longitudinal analyses after renal transplantation in the time period from May 2007 to June 2008, while group 2 (n = 114, 85.1%) cross-sectional study of those who were transplanted from January 1994 to April 2007. The mean ages at transplantation in groups 1 and 2 were 10.6 ± 4.7 years and 7.8 ± 4.5 years, respectively. BK viremia was detected in four (20.0%) patients in group 1, and seven (6.1%) in group 2 (P = 0.04), with increased incidence associated with induction therapy. The median time to detection of BK viremia after transplantation was 44 days in group 1 and 142 days in group 2. BKVAN was diagnosed in three patients (two in group 1 and one in group 2). All three patients diagnosed with BKVAN were receiving tacrolimus, mycophenolate mofetil, and corticosteroids as maintenance immunosuppression. Reducing immunosuppression resulted in reduced BK viremia. Monitoring for BK viremia and BKVAN is important in pRTR being treated with the current immunosuppressive regimen. The first line of treatment for BK viremia remains careful reduction of immunosuppression and close monitoring of renal allograft function.

Symptomatic BK virus cystitis in non-renal transplant recipients

BACKGROUND

BK virus is implicated most commonly in causing BK virus-associated nephropathy in renal transplant recipients. However, on rare occasions, it can also produce symptomatic cystitis in other solid organ transplant recipients.

METHODS

Retrospective review of 2,149 non-renal solid organ transplant recipients over a 6-year period to evaluate patients for cases of symptomatic BK virus cystitis.

RESULTS

Three patients (two heart transplant recipients and one lung transplant recipient) are reported herein with symptomatic BK virus cystitis. These patients responded to reduced immunosuppressive medication with a reduction in viral load in two instances, and the third patient appeared to have an apparent response to prolonged levofloxacin treatment.

CONCLUSIONS

A high index of suspicion should be exercised in non-renal solid organ transplant recipients (particularly heart and lung transplant recipients) who have symptoms consistent with cystitis but have a negative urine bacterial culture.

Non-immunological complications following kidney transplantation

Kidney transplantation (KT) is the most effective way to decrease the high morbidity and mortality of patients with end-stage renal disease. However, KT does not completely reverse the damage done by years of decreased kidney function and dialysis. Furthermore, new offending agents (in particular, immunosuppression) added in the post-transplant period increase the risk of complications. Cardiovascular (CV) disease, the leading cause of death in KT recipients, warrants pre-transplant screening based on risk factors. Nevertheless, the screening methods currently used have many shortcomings and a perfect screening modality does not exist. Risk factor modification in the pre- and post-transplant periods is of paramount importance to decrease the rate of CV complications post-transplant, either by lifestyle modification (for example, diet, exercise, and smoking cessation) or by pharmacological means (for example, statins, anti-hyperglycemics, and so on). Post-transplantation diabetes mellitus (PTDM) is a major contributor to mortality in this patient population. Although tacrolimus is a major contributor to PTDM development, changes in immunosuppression are limited by the higher risk of rejection with other agents. Immunosuppression has also been implicated in higher risk of malignancy; therefore, proper cancer screening is needed. Cancer immunotherapy is drastically changing the way certain types of cancer are treated in the general population; however, its use post-transplant is limited by the risk of allograft rejection. As expected, higher risk of infections is also encountered in transplant recipients. When caring for KT recipients, special attention is needed in screening methods, preventive measures, and treatment of infection with BK virus and cytomegalovirus. Hepatitis C virus infection is common in transplant candidates and in the deceased donor pool; however, newly developed direct-acting antivirals have been proven safe and effective in the pre- and post-transplant periods. The most important and recent developments on complications following KT are reviewed in this article.

Incidence, risk factors, and outcome of BK polyomavirus infection after kidney transplantation

BACKGROUND

Polyomavirus-associated nephropathy is a leading cause of kidney allograft failure. Therapeutic options are limited and prompt reduction of the net state of immunosuppression represents the mainstay of treatment. More recent application of aggressive screening and management protocols for BK-virus infection after renal transplantation has shown encouraging results. Nevertheless, long-term outcome for patients with BK-viremia and nephropathy remains obscure. Risk factors for BK-virus infection are also unclear.

AIM

To investigate incidence, risk factors, and outcome of BK-virus infection after kidney transplantation.

METHODS

This single-centre observational study with a median follow up of 57 (31-80) mo comprises 629 consecutive adult patients who underwent kidney transplantation between 2007 and 2013. Data were prospectively recorded and annually reviewed until 2016. Recipients were periodically screened for BK-virus by plasma quantitative polymerized chain reaction. Patients with BK viral load ≥ 1000 copies/mL were diagnosed BK-viremia and underwent histological assessment to rule out nephropathy. In case of BK-viremia, immunosuppression was minimized according to a prespecified protocol. The following outcomes were evaluated: patient survival, overall graft survival, graft failure considering death as a competing risk, 30-d-event-censored graft failure, response to treatment, rejection, renal function, urologic complications, opportunistic infections, new-onset diabetes after transplantation, and malignancies. We used a multivariable model to analyse risk factors for BK-viremia and nephropathy.

RESULTS

BK-viremia was detected in 9.5% recipients. Initial viral load was high (≥ 10000 copies/mL) in 66.7% and low (< 10000 copies/mL) in 33.3% of these patients. Polyomavirus-associated nephropathy was diagnosed in 6.5% of the study population. Patients with high initial viral load were more likely to experience sustained viremia (95% vs 25%, P < 0.00001), nephropathy (92.5% vs 15%, P < 0.00001), and polyomavirus-related graft loss (27.5% vs 0%, P = 0.0108) than recipients with low initial viral load. Comparison between recipients with or without BK-viremia showed that the proportion of patients with Afro-Caribbean ethnicity (33.3% vs 16.5%, P = 0.0024), panel-reactive antibody ≥ 50% (30% vs 14.6%, P = 0.0047), human leukocyte antigen (HLA) mismatching > 4 (26.7% vs 13.4%, P = 0.0110), and rejection within thirty days of transplant (21.7% vs 9.5%; P = 0.0073) was higher in the viremic group. Five-year patient and overall graft survival rates for patients with or without BK-viremia were similar. However, viremic recipients showed higher 5-year crude cumulative (22.5% vs 12.2%, P = 0.0270) and 30-d-event-censored (22.5% vs 7.1%, P = 0.001) incidences of graft failure than control. In the viremic group we also observed higher proportions of recipients with 5-year estimated glomerular filtration rate < 30 mL/min than the group without viremia: 45% vs 27% (P = 0.0064). Urologic complications were comparable between the two groups. Response to treatment was complete in 55%, partial in 26.7%, and absent in 18.3% patients. The nephropathy group showed higher 5-year crude cumulative and 30-d-event-censored incidences of graft failure than control: 29.1% vs 12.1% (P = 0.008) and 29.1% vs 7.2% (P < 0.001), respectively. Our multivariable model demonstrated that Afro-Caribbean ethnicity, panel-reactive antibody > 50%, HLA mismatching > 4, and rejection were independent risk factors for BK-virus viremia whereas cytomegalovirus prophylaxis was protective.

CONCLUSION

Current treatment of BK-virus infection offers sub-optimal results. Initial viremia is a valuable parameter to detect patients at increased risk of nephropathy. Panel-reactive antibody > 50% and Afro-Caribbean ethnicity are independent predictors of BK-virus infection whereas cytomegalovirus prophylaxis has a protective effect.

Risk Factors of Acute Rejection in Patients with BK Nephropathy After Reduction of Immunosuppression

Background

BK nephropathy (BKN) affects graft function and increases the risk of graft failure. The reduction of immunosuppression is the main treatment for BKN. However, acute rejection may develop following immunosuppression reduction, and data regarding the risk factors of acute rejection during the post-reduction period are insufficient.

Material/Methods

Of 758 patients who received a kidney transplantation (KT) between 2008 and 2011, 79 who underwent immunosuppression reduction as BKN treatment were enrolled. The risk factors of acute rejection after immunosuppression reduction were identified using multivariate logistic regression analysis.

Results

During the median follow-up period (75 months), acute rejection developed in 21.5% of study group patients and in 22.5% of KT recipients without BKN. The rejection group showed a trend of higher body mass index (24.13±3.92 vs. 22.40±3.31 kg/m², P=0.070) and lower tacrolimus levels than the no rejection group, although mycophenolate mofetil (MMF) doses were not lower in the rejection group. The rejection group showed worse graft survival than the no rejection group (P=0.001 by the log rank test). A greater number of patients in the rejection group exhibited reduced calcineurin inhibitor (CNI) level by >20% at 1 month after initial BKV detection (34.2% vs. 7.9%, P=0.008). Multivariate analysis indicated that the peak BKV PCR level (odds ratio [OR], 0.136; 95% confidence interval [CI], 0.025–0.732; P=0.020), MMF discontinuation (vs. MMF reduction; OR, 0.112; 95% CI, 0.020–0.618; P=0.012) and CNI level reduction >20% (OR, 33.752; 95% CI, 4.263–267.251; P=0.001) were significantly associated with acute rejection.

Conclusions

Acute rejection after immunosuppression reduction for BKN showed worse allograft survival than the patients without acute rejection. In addition, a CNI dose reduction >20% at 1 month after the initial BKV detection can increase the risk of acute rejection.

BK Polyomavirus: Clinical Aspects, Immune Regulation, and Emerging Therapies

BK polyomavirus (BKV) causes frequent infections during childhood and establishes persistent infections within renal tubular cells and the uroepithelium, with minimal clinical implications. However, reactivation of BKV in immunocompromised individuals following renal or hematopoietic stem cell transplantation may cause serious complications, including BKV-associated nephropathy (BKVAN), ureteric stenosis, or hemorrhagic cystitis. Implementation of more potent immunosuppression and increased posttransplant surveillance has resulted in a higher incidence of BKVAN. Antiviral immunity plays a crucial role in controlling BKV replication, and our increasing knowledge about host-virus interactions has led to the development of improved diagnostic tools and clinical management strategies. Currently, there are no effective antiviral agents for BKV infection, and the mainstay of managing reactivation is reduction of immunosuppression. Development of immune-based therapies to combat BKV may provide new and exciting opportunities for the successful treatment of BKV-associated complications.

Onset and progression of de novo donor-specific anti-human leukocyte antigen antibodies after BK polyomavirus and preemptive immunosuppression reduction

BACKGROUND

BK polyomavirus (BKPyV) viremia/nephropathy and reduction in immunosuppression following viremia may increase the risk of alloimmune activation and allograft rejection. This study investigates the impact of BKPyV viremia on de novo donor anti-human leukocyte antigen (HLA)-specific antibodies (dnDSA).

PATIENTS AND METHODS

All primary renal transplants at East Carolina University from March 1999 to December 2010, with at least 1 post-transplant BKPyV viral load testing, were analyzed. Patients were negative for anti-HLA antibodies to donor antigens (tested via single antigen beads) at transplantation and at first BKPyV testing.

RESULTS

Nineteen of 174 patients (11%) tested positive for BKPyV viremia. Within 24 months of BKPyV viremia detection, 79% of BKPyV-viremic patients developed dnDSA. Only 20% of BKPyV viremia-persistent cases, compared to 86% of BKPyV viremia-resolved cases, developed dnDSA (P = 0.03). Poor allograft survival was evident in BKPyV viremia-persistent patients (60% failure by 2 years post BKPyV diagnosis) and in BKPyV viremia-resolved patients with dnDSA (5-year post BKPyV diagnosis allograft survival of 48%).

CONCLUSIONS

Post-transplant BKPyV viremia and preemptive immunosuppression reduction is associated with high rates of dnDSA. When preemptively treating BKPyV viremia, dnDSA should be monitored to prevent allograft consequences.

Preemptive reduction of immunosuppression upon high urinary polyomavirus loads improves patient survival without affecting kidney graft function

BACKGROUND

Polyomavirus (PV) is a major cause of kidney graft disease. Monitoring by polymerase chain reaction (PCR) on blood is currently recommended. In order to avoid irreversible lesions, we investigated the clinical impact of preemptive reduction of immunosuppression (IS) in kidney transplant recipients (KTR) upon detection of high urinary PV (Upv) load, including BK virus and JC virus.

MATERIAL AND METHODS

From 2000 to 2011, in our single center, 789 consecutive KTR were distributed into 4 groups, according to the maximal Upv levels (by PCR) during the first year and the therapeutic option: (A) Upv <10⁴ copies (cp)/mL (n=573), (B) ≥10⁴ Upv <10⁷ cp/mL (n=100), and (C) Upv ≥10⁷ cp/mL (n=116); in group C, the IS drug doses were reduced in subgroup Ca (n=102) only, as 14 patients (subgroup Cb) were at risk for graft rejection.

RESULTS

The preemptive reduction of IS (group Ca) increased patient survival as compared with all other groups (P<.05), did not modify graft function, and increased graft survival vs group A (risk ratio: 5.7, confidence interval: 1.8-18.1, P=.003). Differences for risk factors are as follows (groups Ca vs A): incidence of human leukocyte antigen (HLA) immunization (>5% panel reactive antibodies): 3% vs 8% (P=.05), number of HLA mismatches: 2.7 vs 2.5 (P=.049), and incidence of acute rejection: 9.8% vs 24.2% (P=.005). PV-associated nephropathy occurred only in group Ca (2% of total grafts) without effect on patient or graft outcome.

CONCLUSION

The reduction of IS in patients with high Upv loads is beneficial for patient survival and does not affect graft survival or graft function.

Molecular mechanisms and cell signaling of 20-hydroxyeicosatetraenoic acid in vascular pathophysiology

Cytochrome P450s enzymes catalyze the metabolism of arachidonic acid to epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid and hydroxyeicosatetraeonic acid (HETEs). 20-HETE is a vasoconstrictor that depolarizes vascular smooth muscle cells by blocking K+ channels. EETs serve as endothelial derived hyperpolarizing factors. Inhibition of the formation of 20-HETE impairs the myogenic response and autoregulation of renal and cerebral blood flow. Changes in the formation of EETs and 20-HETE have been reported in hypertension and drugs that target these pathways alter blood pressure in animal models. Sequence variants in CYP4A11 and CYP4F2 that produce 20-HETE, UDP-glucuronosyl transferase involved in the biotransformation of 20-HETE and soluble epoxide hydrolase that inactivates EETs are associated with hypertension in human studies. 20-HETE contributes to the regulation of vascular hypertrophy, restenosis, angiogenesis and inflammation. It also promotes endothelial dysfunction and contributes to cerebral vasospasm and ischemia-reperfusion injury in the brain, kidney and heart. This review will focus on the role of 20-HETE in vascular dysfunction, inflammation, ischemic and hemorrhagic stroke and cardiac and renal ischemia reperfusion injury.

Clinical impact of BK virus surveillance on outcomes in kidney transplant recipients

BACKGROUND

The objective of this study was to investigate the clinical impact of BK virus surveillance on graft injury in kidney transplantation.

METHODS

BK viremia in kidney transplant recipients was evaluated by use of plasma quantitative polymerase chain reaction. The prevalence of BK viremia and BK virus-associated nephropathy (BKVAN) and the clinical impact of BK viremia on graft outcomes were assessed.

RESULTS

This study took place between January 2008 and June 2013. A total of 213 kidney transplant recipients were included. The prevalence of BK viremia and high BK viremia (≥1 × 10(4) copies/mL) was 66.7% (142/213) and 17.4% (37/213), respectively. A diagnosis of BKVAN was confirmed by means of allograft biopsy in 9 patients (4.2%). The estimated glomerular filtration rate after transplantation was similar in both the low BK viremia (<1 × 10(4) copies/mL) and non-BK viremia groups but was significantly lower in the high BK viremia group after 18 months. In receiver operating characteristic curve analysis, the area under the curve value of plasma polymerase chain reaction was 0.980. We found that a viral load >92,850 copies/mL was able to predict BKVAN with 89% sensitivity and 94.6% specificity. The risk factors for viral loads ≥1 × 10(4) copies/mL were cytomegalovirus infection, steroid pulse therapy, and acute rejection.

CONCLUSIONS

High BK viremia was associated with poor graft function after kidney transplantation. The serial monitoring of BK viremia in kidney transplant recipients was helpful in predicting BKVAN and might prevent further progression.

Factors Influencing Graft Outcomes Following Diagnosis of Polyomavirus -Associated Nephropathy after Renal Transplantation

Background

Polyomavirus associated nephropathy (PVAN) is a significant cause of early allograft loss and the course is difficult to predict. The aim of this study is to identify factors influencing outcome for PVAN.

Methods

Between 2006 and 2014, we diagnosed PVAN in 48 (7.8%) of 615 patients monitored for BK virus every 1–4 weeks after modification of maintenance immunosuppression. Logistic or Cox regression analysis were performed to determine which risk factors independently affected clinical outcome and graft loss respectively.

Results

After 32.1±26.4 months follow-up, the frequencies of any graft functional decline at 1 year post-diagnosis, graft loss and any graft functional decline at the last available follow-up were 27.1% (13/48), 25.0% (12/48), and 33.3% (16/48), respectively. The 1, 3, 5 year graft survival rates were 100%, 80.5% and 69.1%, respectively. The mean level of serum creatinine at 1 year post-diagnosis and long-term graft survival rates were the worst in class C (p<0.05). Thirty-eight of 46 (82.6%) BKV DNAuria patients reduced viral load by 90% with a median time of 2.75 months (range, 0.25–34.0 months) and showed better graft survival rates than the 8 patients (17.4%) without viral load reduction (p<0.001). Multivariate logistic regression analysis showed that extensive interstitial inflammation (OR 20.2, p = 0.042) and delayed fall in urinary viral load (>2.75 months for >90% decrease) in urine (OR 16.7, p = 0.055) correlated with worse creatinine at 1 year post-diagnosis. Multivariate Cox regression analysis showed that extensive interstitial inflammation (HR 46988, p = 0.032) at diagnosis, and high PVAN stage (HR 162.2, p = 0.021) were associated with worse long-term graft survival rates.

Conclusions

The extent of interstitial inflammation influences short and long-term graft outcomes in patients with PVAN. The degree of PVAN, rate of reduction in viral load, and viral clearance also can be used as prognostic markers in PVAN.

Efficacy of intravenous immunoglobulin in the treatment of persistent BK viremia and BK virus nephropathy in renal transplant recipients

BK virus-associated nephropathy (BKVN) can cause clinically significant viral infection in renal transplant recipients, leading to allograft dysfunction and loss. The usual management of BKVN involves the reduction of immunosuppression and the addition of leflunomide, quinolones, and cidofovir, but the rate of graft loss remains high. The aim of this study was to assess the impact of treatment with intravenous human immunoglobulin (IVIG) on the outcome of BKVN in renal transplant recipients. Upon diagnosis of BKVN, patients remained on anti-polyomavirus treatment, consisting of the reduction of immunosuppression and the use of leflunomide therapy. Treatment with IVIG was given only to patients who did not respond to 8 weeks of the adjustment of immunosuppression and leflunomide. All 30 patients had persistent BKV viremia and BKVN with their mean BK viral loads higher than the baseline (range, 15,000-2 million copies/mL). Mean peak BK load was 205,314 copies/mL compared with 697 copies/mL after 1 year of follow-up. Twenty-seven patients (90%) had a positive response in clearing viremia. The actuarial patient and graft survival rates after 12 months were 100% and 96.7%, respectively. IVIG administration appeared to be safe and effective in treating BKV viremia and BKVN and preventing graft loss in patients who had inadequate response to immunosuppression reduction and leflunomide therapy.

Viral surveillance and subclinical viral infection in pediatric kidney transplantation

The more potent immunosuppressive therapy that has successfully reduced the incidence of acute rejection and improved graft outcomes has also resulted in a higher incidence of viral complications. Sensitive molecular methods now allow for the detection of subclinical viral infection, which is increasingly recognized due to the adoption of routine post-transplant viral surveillance protocols. The goal of viral surveillance is the detection of subclinical viral infection that triggers an intervention; one that either prevents progression to viral disease or leads to early diagnosis of viral disease, which is associated with improved outcomes. Knowledge of the epidemiology and natural history of subclinical viral infection and viral disease, as well as patient-specific risk factors, is required to establish the optimal surveillance schedule which achieves the goal of early diagnosis. Evidence that detection of subclinical viral infection can impact viral disease is variable depending on the virus. This review will summarize the current data on the role of viral surveillance for BK virus (BKV), cytomegalovirus (CMV), and the Epstein-Barr virus (EBV) in the pediatric kidney transplant population.

Incidence, risk factors, and outcomes of delayed-onset cytomegalovirus disease in a large, retrospective cohort of heart transplant recipients

BACKGROUND

Delayed-onset cytomegalovirus (CMV) disease can occur among heart transplant recipients after stopping anti-CMV prophylaxis. We evaluated a large, retrospective cohort of heart transplant recipients in the United States through the use of billing data from 3 Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SID) to determine the epidemiology of delayed-onset CMV disease coded during hospital readmission.

METHODS

We identified 2280 adult heart transplant recipients from 2004 to 2010 through the use of the California, Florida, and New York SID. Demographics, comorbidities, heart failure etiology, CMV disease, and inpatient death were identified. CMV disease was classified as early-onset (≤100 days) or delayed-onset (>100 days after transplant). Possible tissue invasion by CMV was determined through the use of codes for CMV pneumonitis, hepatitis, and gastrointestinal endoscopy. Multivariate analysis was performed with the use of Cox proportional hazards models.

RESULTS

Delayed-onset CMV disease occurred in 7.5% (170/2280) and early-onset CMV disease occurred in 2.0% (45/2280) of heart transplant recipients. Risk factors for delayed-onset CMV disease included residence in a non-metropolitan locale (aHR. 1.8; 95% confidence interval [CI], 1.0-3.3) and ischemic cardiomyopathy as heart failure etiology (aHR, 1.8; 95% CI, 1.3-2.5). Inpatient death >100 days after transplant was associated with delayed-onset CMV disease with possible tissue invasion (aHR, 2.0; 95% CI, 1.1-3.8), transplant failure or rejection (aHR, 4.0; 95% CI, 2.7-5.8), and renal failure (aHR, 1.5; 95% CI, 1.1-2.0).

CONCLUSIONS

Delayed-onset CMV disease is more common than early-onset CMV disease among heart transplant recipients. These results suggest that delayed-onset tissue-invasive CMV disease may be associated with an increased risk of death.

BK virus infection: an update on diagnosis and treatment

BK virus, first isolated in 1971, is a significant risk factor for renal transplant dysfunction and allograft loss. Unfortunately, treatment options for BK virus infection are limited, and there is no effective prophylaxis. Although overimmunosuppression remains the primary risk factor for BK infection after transplantation, male gender, older recipient age, prior rejection episodes, degree of human leukocyte antigen mismatching, prolonged cold ischemia time, BK serostatus and ureteral stent placement have all been implicated as risk factors. Routine screening for BK has been shown to be effective in preventing allograft loss in patients with BK viruria or viremia. Reduction of immunosuppression remains the mainstay of BK nephropathy treatment and is the best studied intervention. Laboratory-based methods such as ELISPOT assays have provided new insights into the immune response to BK and may help guide therapy in the future. In this review, we will discuss the epidemiology of BK virus infection, screening strategies, treatment options and future research directions.

BK virus replication in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis

BACKGROUND

BK virus (BKV) is an important cause of renal dysfunction in kidney transplant (KTX) recipients. Immunosuppression intensity is a major risk factor for BKV replication in these patients. The prevalence of BKV replication in immunosuppressed patients with granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) without transplant is not known.

METHODS

Consecutive patients (n = 37) with a diagnosis of GPA (n = 25) or MPA (n = 12) without history of KTX were evaluated for plasma BKV replication by quantitative PCR (group A). Descriptive data were collected. BKV replication in this nontransplant immunosuppressed vasculitis cohort was compared with a historical cohort of vasculitis KTX recipients (group B).

RESULTS

Group A patients had mean disease duration of 75 months. Mean age was 57 years and 54% were female. Mean time from vasculitis onset to BKV testing was 36 months, and 19/37 patients were tested within 24 months of induction therapy. At the time of BKV testing, 73% were on prednisone (P) with azathioprine, mycophenolate mofetil (MMF), methotrexate or leflunomide. None of the nontransplanted vasculitis patients had detectable plasma BKV. Among 35 patients in group B, 16 were tested for BKV; 5/16 (31%) had detectable virus in plasma at a mean of 6 months after TX (p = 0.002). Most (94%) were on maintenance therapy with MMF, P and tacrolimus.

CONCLUSION

Immunosuppressed patients with GPA/MPA without KTX had no evidence of plasma BKV. However, BKV was common in GPA/MPA patients after KTX, suggesting that replication may be related to differences in immunosuppression, alloimmune activation or differences in host defense mechanisms.

Association of BK viremia with human leukocyte antigen mismatches and acute rejection, but not with type of calcineurin inhibitor

INTRODUCTION

BK viremia and polyomavirus-associated nephropathy (PVN) represent a significant problem after kidney transplantation. Both are associated with intensified immunosuppression, but other risk factors and the impact of a screening program on outcome are incompletely understood.

METHODS

Here, we report on the short- and long-term outcome of a cohort of patients, who were transplanted in 2006/2007 and included in a newly introduced systematic 3-monthly screening for BK viremia at the University Hospital Zurich. In patients testing positive for BK viremia, screening frequency was intensified and immunosuppression reduced. Patients with suspected PVN underwent transplant biopsy.

RESULTS

Among 152 included patients, 49 (32%) tested positive for BK viremia, but only 8 developed biopsy-proven PVN. BK viremia had a significant impact on estimated glomerular filtration rate and proteinuria in the first 2 years. Acute rejection episodes and the number of human leukocyte antigen (HLA) mismatches were the strongest independent predictors of BK viremia in a multiple logistic model. In contrast, no particular immunosuppressive agent or regimen was associated with enhanced risk.

CONCLUSION

Taken together, systematic BK viremia screening led to detection of a high percentage of viremic patients. With adjustment of immunosuppression, an excellent outcome was achieved. The independent association of HLA mismatches with BK viremia suggests impaired polyomavirus immunosurveillance in highly mismatched allografts.

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.

The impact of surveillance and rapid reduction in immunosuppression to control BK virus-related graft injury in kidney transplantation

We prospectively screened 609 consecutive kidney (538) and kidney-pancreas (71) transplant recipients for BK viremia over a 4-year interval using polymerase chain reaction viral load detection and protocol kidney biopsies. We found that BK viremia is common at our center: total cases 26.7%, cases during first year 21.3% (mean 4 months), and recipients with ≥ 10 000 copies/ml 12.3%. We found few predictive clinical or demographic risk factors for any BK viremia or viral loads ≥ 10,000 copies/ml, other than prior treatment of biopsy confirmed acute rejection and/or higher immunosuppressive blood levels of tacrolimus (P = 0.001) or mycophenolate mofetil (P = 0.007). Viral loads at diagnosis (<10 000 copies/ml) demonstrated little impact on graft function or survival. However, rising copy numbers demand early reductions in immunosuppressive drug doses of at least 30-50%. Viral loads >185 000 copies/ml at diagnosis were predictive of BK virus-associated nephropathy (BKVAN; OR: 113.25, 95% CI: 17.22-744.6, P < 0.001). Surveillance for BK viremia and rapid reduction of immunosuppression limited the incidence of BKVAN to 1.3%. The addition of leflunomide or ciprofloxacin to immunosuppressive dose reduction did not result in greater rates of viral clearance. These data support the role of early surveillance for BK viremia to limit the impact on transplant outcome, although the most effective schedule for screening awaits further investigation.

Leflunomide therapy for BK virus allograft nephropathy after pediatric kidney transplantation

The BK virus (BKV) can be reactivated with immunosuppressive treatment in renal allograft recipients, which can result in interstitial nephritis (BKV-associated nephropathy, BKVAN) and lead to renal allograft failure. Recently, leflunomide has been reported in some case series of BKVAN with favorable results. Most studies have included only adult patients, we herein report a pediatric case and include a literature review. The patient was a nine-yr-old female with end-stage renal disease due to hypoxic kidney injury. A deceased donor renal transplant was performed and good initial allograft function was achieved following treatment with prednisolone, tacrolimus and mycophenolate mofetil. The serum Cr level increased to 1.6 mg/dL over the following four-month period. A kidney biopsy revealed pathologic findings of acute cellular rejection and BK nephropathy. After methylprednisolone pulse therapy was administered to control acute rejection, the tacrolimus dose was reduced, and intravenous immunoglobulin treatment and leflunomide therapy were administered to control the BKVAN. Over the following 18 months, the viral load steadily decreased and remained below 100 copies/mL in the plasma. Leflunomide therapy in addition to a reduction of the immunosuppressive therapies resulted in a significant decline in the BK viral load without further deterioration of renal function.

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.

The BK virus in renal transplant recipients-review of pathogenesis, diagnosis, and treatment

The BK virus, a DNA virus from the Polyomavirus group, represents an opportunistic infection of immunosuppressed transplant recipients. Though the virus was discovered approximately 40 years ago, the emergence of BK virus nephropathy since 1995 onwards, with associated high graft loss rates, has revolutionized renal transplantation medicine. Kidney transplant professionals realized that the consequences of over-immunosuppression were as severe as the consequences of under-immunosuppression and we entered the era of immunosuppressive minimization. Despite this recognition, the optimal testing type for BK virus infections and frequency of testing are hotly debated. Similarly, optimal treatment strategies remain sources of intense controversy. The authors review the current strategies of screening, diagnosis, and possible treatment, and also review the amount and quality of evidence in favor or against. Similarities and differences between cytomegalovirus, Epstein-Barr virus, and BV virus, the three major viral infections in kidney transplantation, are highlighted.

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.

Polyomavirus-associated nephropathy: a comparison of 2 different strategies for immunosuppression reduction

Polyomavirus-associated nephropathy (PVAN) is an increasing cause of renal allograft dysfunction, but the optimal management of immunosuppression for these patients is unclear. We examined the clinical course of 58 patients with biopsy-proven PVAN diagnosed from 1997 to 2008 at Johns Hopkins Medical Institutions. Immunosuppression management was analyzed as 2 different immunosuppression reduction strategies, the first centered on eliminating a single immunosuppressive drug and reducing the doses of all other immunosuppressive drugs (Strategy A, n = 40), compared with the second, centered on reducing the doses of all immunosuppressive drugs and eliminating none (Strategy B, n = 18). Primary outcome was graft failure, defined as a 50% reduction in estimated glomerular filtration rate, or the need for dialysis within 2 years of PVAN diagnosis. Graft failure developed in 17 (29%) patients during follow-up. In unadjusted and adjusted Cox models, both strategies of immunosuppression reduction had similar efficacy in preventing graft failure (hazard ratio [HR], 0.61; 95% confidence interval, 0.18-2.06; p = 0.43). Rejection after PVAN occurred in 24 of 58 patients and was associated with a 3-fold higher risk of graft failure (HR, 2.99; p = 0.005). Ancillary therapies (cidofovir or leflunomide) were associated with a trend toward faster clearance of viremia (p = 0.65) but were not predictive of outcome.In conclusion, the 2 strategies of immunosuppression reduction had similar efficacy in preventing graft failure. Post-PVAN rejection leads to graft failure. Early repeat allograft biopsy should be considered in the management of PVAN with persistent graft dysfunction.

Infection and chronic allograft dysfunction

With the advent of more potent immunosuppressive regimens, the incidence of acute rejection following renal transplantation has declined sharply in recent years. In spite of this, long-term graft outcomes remain suboptimal because of relentless attrition by cumulated insults to the allograft. As acute rejection rates have declined, other causes of graft injury and loss have recently emerged. Among these, infectious diseases remain a persistent threat and can be associated with allograft dysfunction. This group includes nephropathy due to polyoma (BK) virus infection, cytomegalovirus disease, and bacterial infection (the latter most commonly arising from the urinary tract). Rarer infectious causes of chronic allograft dysfunction include cryoglobulinemia associated with hepatitis C, Epstein-Barr virus-associated posttransplant lymphoproliferative disease, and direct cytotoxicity from adenoviral infection or parvovirus B19.

The role of ureteral stents for all ureteroneocystostomies in kidney transplants

BACKGROUND

Despite significant advancements in renal transplantation, certain basic surgical practices such as the routine use of ureteral stents (US) remain controversial. A recent met-analysis of ureteral stenting concluded that the routine use of US resulted in improved outcomes. In contrast, the indiscriminate use of US can lead to adverse complications.

OBJECTIVE

To better define this question, we reviewed our single center experience in which US were placed selectively.

METHODS

301 patients were eligible to be enrolled. 55 living donor and 246 deceased-donor charts were analyzed for donor and recipient clinical characteristics, immunosuppressive therapy and outcomes.

RESULTS

28 US were placed for either small bladder capacity (n=7), unhealthy appearing bladder tissue (n=8) or for an uncertain vascular supply to the ureter (n=13). Patients with US did not develop urinary leaks, 8 (28%) developed complications including obstruction, encrustation, and urinary tract infections. 12 (4.3%) non-stented patients developed a clinically significant urinary leak. Risk factors for urinary leaks included dual and en-bloc pediatric donor kidney transplants, extended criteria donors and the use of single U stitch technique for ureteral anastomoses.

CONCLUSION

Our results demonstrate that the majority of patients can be successfully transplanted without the routine use of US. Selective use of US should be reserved for high-risk situations.