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

Human cytomegalovirus-related gastrointestinal disease after kidney transplantation: A systematic review

BACKGROUND

Human-cytomegalovirus (hCMV) infection involving the gastrointestinal tract represents a leading cause of morbidity and mortality among kidney transplant (KT) recipients (KTRs). Signs and symptoms of the disease are extremely variable. Prompt anti-viral therapy administration and immunosuppression modification are key factors for optimizing management. However, complex work-up strategies are generally required to confirm the preliminary diagnosis. Unfortunately, solid evidence and guidelines on this specific topic are not available. We consequently aimed to summarize current knowledge on post-KT hCMV-related gastrointestinal disease (hCMV-GID).

METHODS

We conducted a systematic review (PROSPERO ID: CRD42023399363) about hCMV-GID in KTRs.

RESULTS

Our systematic review includes 52 case-reports and ten case-series, published between 1985 and 2022, collectively reporting 311 cases. The most frequently reported signs and symptoms of hCMV-GID were abdominal pain, diarrhea, epigastric pain, vomiting, fever, and GI bleeding. Esophagogastroduodenoscopy and colonoscopy were the primary diagnostic techniques. In most cases, the preliminary diagnosis was confirmed by histology. Information on anti-viral prophylaxis were extremely limited as much as data on induction or maintenance immunosuppression. Treatment included ganciclovir and/or valganciclovir administration. Immunosuppression modification mainly consisted of mycophenolate mofetil or calcineurin inhibitor minimization and withdrawal. In total, 21 deaths were recorded. Renal allograft-related outcomes were described for 26 patients only. Specifically, reported events were acute kidney injury (n = 17), transplant failure (n = 5), allograft rejection (n = 4), and irreversible allograft dysfunction (n = 3).

CONCLUSIONS

The development of local and national registries is strongly recommended to improve our understanding of hCMV-GID. Future clinical guidelines should consider the implementation of dedicated diagnostic and treatment strategies.

BK polyomavirus DNAemia in pancreas transplant recipients compared to pancreas-kidney recipients

BACKGROUND

BK polyomavirus (BKV) infection is a common complication of kidney transplantation. While BKV has been described in non-kidney transplant recipients, data are limited regarding its epidemiology and outcomes in pancreas transplant recipients.

METHODS

We conducted a retrospective cohort study of adults who underwent pancreas transplantation from 2010-2020. The primary outcome was BKV DNAemia. Secondary outcomes were estimated glomerular filtration rate (eGFR) reduction by 30%, eGFR < 30 mL/min/1.73 m2 , endstage kidney disease, and pancreas allograft failure. Cox regression with time-dependent variables was utilized.

RESULTS

Four hundred and sixty-six patients were analyzed, including 74, 46, and 346 with pancreas transplant alone (PTA), pancreas-after-kidney, or simultaneous pancreas-kidney transplants, respectively. PTA recipients experienced a lower incidence of BKV DNAemia (8.8% vs. 32.9%; p < .001) and shorter duration of DNAemia (median 28.0 vs. 84.5 days). No PTA recipients with BKV DNAemia underwent kidney biopsy or developed endstage kidney disease. Lymphopenia, non-PTA transplantation, and older age were associated with BKV DNAemia, which itself was associated with pancreas allograft failure (adjusted hazard ratio 2.14, 95% confidence interval 1.27-3.60; p = .004). Among PTA recipients, BKV DNAemia was not associated with eGFR reduction or eGFR < 30 mL/min/1.73 m2 .

CONCLUSIONS

BKV DNAemia was common among PTA recipients, though lower than a comparable group of pancreas-kidney recipients. However, BKV DNAemia was not associated with adverse native kidney outcomes and no PTA recipients developed endstage kidney disease. Conversely, BKV DNAemia was associated with pancreas allograft failure. Further studies are needed to estimate the rate of BKV nephropathy in this population, and further evaluate long-term kidney outcomes.

Stepwise Reduction of Mycophenolate Mofetil with Conversion to Everolimus for the Treatment of Active BKV in Kidney Transplant Recipients: A Single-Center Experience in Vietnam

Background: No specific antiviral drug can effectively treat BKV reactivation after kidney transplantation. Thus, we evaluated stepwise-reduced immunosuppression to treat BKV reactivation. Methods: 341 kidney-transplant recipients were monitored for BKV infection (BKV-viremia, BKV-viruria). Positive samples with a significant virus load were nested PCR-genotyped in the VP1 region. In 97/211 patients presenting BKV viremia ≥104 copies/mL and/or BKV viruria ≥107 copies/mL, or BKV-nephropathy immunosuppression (i.e., mycophenolate mofetil [MMF]) was reduced by 50%. If viral load did not decrease within 28 days, MMF dose was further reduced by 25%, although calcineurin-inhibitor (CNI) therapy remained unchanged. If BKV viral load did not decrease within another 28 days, MMF was withdrawn and replaced by everolimus combined with reduced CNIs. Results: Only 41/97 BKV (+) cases completed the 6-month follow-up. Among these, 29 (71%) were in the BKV-I group and 12 (29%) were in BKV-IV. BKV viruria and BKV viremia were significantly decreased from 9.32 to 6.09 log10 copies/mL, and from 3.59 to 2.45 log10 copies/mL (p < 0.001 and p = 0.024, respectively). 11/32 (34.4%) patients were cleared of BKV viremia; 2/32 (6.3%) patients were cleared of BKV in both serum and urine, and 9/9 (100%) only had BKV viruria but did not develop BKV viremia. eGFR remained stable. No patient with BKV-related nephropathy had graft loss. There was a significant inverse relationship between changes in eGFR and serum BKV load (r = −0.314, p = 0.04). Conclusions: This stepwise immunosuppressive strategy proved effective at reducing BKV viral load in kidney transplant recipients that had high BKV loads in serum and/or urine. Renal function remained stable without rejection.

Determining host factors contributing to the reactivation of JC virus in kidney transplant recipients

BACKGROUND AND AIMS

The John Cunningham virus (JCV) is the established etiological agent of the polyomavirus-associated nephropathy among renal transplant recipients. In the present study, we aimed to determine the probable predictive factors leading to JCV replication in renal transplant patients.

MATERIAL AND METHODS

Urine and plasma samples were collected from a total of 120 consecutive renal-transplanted patients without preliminary screening from Jan 2018 to Mar 2019. After DNA extraction, the simultaneous detection and quantification of JCV and BK polyomavirus (BKV) were conducted using a Real-time quantitative PCR method. Moreover, statistical analyses were performed using the statistical software packages, SPSS version 21.

RESULTS

The prevalence of JCV viruria and viremia among renal transplant recipients were 26 (21.67%) and 20 (16.67%), respectively. A significant association was observed between the JCV and two risk factors, diabetes mellitus (P = 0.002) and renal stones (P = 0.015). The prevalence of JCV viremia among recipients who were grafted near time to sampling was significantly higher (P = 0.02). There was a statistically significant coexistence between BK and JC viruses among our patients (P = 0.029). The frequency of JCV viruria in males was reported almost three times more than in females (P = 0.005). The JCV shedding in urine was significantly associated with the tropical steroids like prednisolone acetate, which have been the standard regimen (P = 0.039). Multivariable analysis revealed duration of post-transplantation (OR, 0.89; P = 0.038), diabetes mellitus (OR, 1.85; P = 0.034), and renal stone (OR 1.10; P = 0.04) as independent risk factors associated with JCV viremia post-renal transplantation.

CONCLUSION

It seems that the discovery of potential risk factors, including immunological and non-immunological elements, may offer a possible preventive or therapeutic approach in the JCV disease episodes. The results of this study may also help clarify the probable clinical risk factors involving in progressive multifocal leukoencephalopathy development.

Nephrotoxicity of calcineurin inhibitors as a risk factor for BK polyomavirus replication after kidney transplantation

BK polyomavirus-associated nephropathy (PyVAN) is responsible for a significant percentage of transplanted kidneys prematurely terminating their function. Its occurrence is closely related to the intensity of immunosuppressive therapy. In a group of 161 newly transplanted patients, we prospectively evaluated 457 protocol renal biopsies performed within the first year after transplantation. Using the calcineurin inhibitors (CI) nephrotoxicity score, the incidence of nephrotoxicity was monitored as a manifestation of excessive immunosuppression. Findings were correlated with clinical evidence of active BK polyomavirus (BKPyV) replication and PyVAN. Compared to the normal histology, nephrotoxicity was associated with more frequent BKPyV viremia and viruria (p = .01 and p < .01, respectively) and more common occurrence of PyVAN. The persistence of toxicity in the subsequent biopsy proved to be a negative risk factor of viremia and viruria (p = .03 and p < .01, respectively), independently of the initial BKPyV status. Toxicity could also be used as a predictor of viremia and viruria (p = .04 and p < .01, respectively) even in the absence of viral replication at the time of initial biopsy. The early histological manifestation of CI nephrotoxicity was associated with significant BKPyV reactivation in the risky first posttransplant year.

BK virus nephropathy in a heart transplant recipient

BK virus nephropathy in kidney transplantation is widely recognized as an important cause of graft dysfunction and loss. In the case of transplants of organs other than kidney, BK virus nephropathy in native kidneys has been recognized as a cause of chronic kidney disease, which is related with immunosuppression; however, the diagnosis is usually late because the renal dysfunction is attributed to other causes, such as toxicity by anticalcineurinic drugs, interstitial nephritis due to medications, hemodynamic changes, diabetes, hypertension, etc. We report a case of BK virus nephropathy in a patient who underwent heart transplantation due to peripartum cardiomyopathy. The kidney biopsy reported active chronic tubulointerstitial nephritis associated with late stage polyomavirus nephritis and the blood viral load for BK virus was positive (logarithm 4.5). The immunosuppressive treatment was reduced, and after two years of follow-up, the patient had stable renal function with a serum creatinine of 2.5 mg/dL (GFR of 23.4 mL/min/1.73m2). We recommend that the BK virus be considered as a cause of renal dysfunction in heart transplant recipients, with the aim of detecting its replication in time to reduce immunosuppressive therapy before irreversible compromise of renal function may manifest.

The Role of HLA and KIR Immunogenetics in BK Virus Infection after Kidney Transplantation

BK virus (BKV) is a polyomavirus with high seroprevalence in the general population with an unremarkable clinical presentation in healthy people, but a potential for causing serious complications in immunosuppressed transplanted patients. Reactivation or primary infection in kidney allograft recipients may lead to allograft dysfunction and subsequent loss. Currently, there is no widely accepted specific treatment for BKV infection and reduction of immunosuppressive therapy is the mainstay therapy. Given this and the sequential appearance of viruria-viremia-nephropathy, screening and early detection are of utmost importance. There are numerous risk factors associated with BKV infection including genetic factors, among them human leukocyte antigens (HLA) and killer cell immunoglobulin-like receptors (KIR) alleles have been shown to be the strongest so far. Identification of patients at risk for BKV infection would be useful in prevention or early action to reduce morbidity and progression to frank nephropathy. Assessment of risk involving HLA ligands and KIR genotyping of recipients in the pre-transplant or early post-transplant period might be useful in clinical practice. This review summarizes current knowledge of the association between HLA, KIR and BKV infection and potential future directions of research, which might lead to optimal utilization of these genetic markers.

Human BK and JC polyomaviruses: Molecular insights and prevalence in Asia

Polyomaviridae family consists of small circular dsDNA viruses. Out of the 14 human polyomaviruses described so far, BKPyV and JCPyV have been studied extensively since their discovery in 1971. Reportedly, both BKPyV and JCPyV are widely distributed across the globe with the frequency of 80-90 % in different populations. The primary infection of these viruses is usually asymptomatic and latent which is activated as a consequence of immunosuppression. Activated BKPyV and JCPyV viruses lead to the development of BK Virus Associated Nephropathy and Progressive Multifocal Leukoencephalopathy, respectively. Immense progress has been made during the last few decades regarding the molecular understanding of polyomaviruses. Epidemiology of polyomaviruses has also been studied extensively. However, most of the epidemiological studies have focused on European and American populations. Therefore, limited data is available regarding the geographical distribution of these potentially oncogenic viruses in Asian countries. In this article, we have presented a compendium of latest advances in the molecular understanding of polyomaviruses and their pathobiology. We also present a comprehensive review of published literature regarding the epidemiology and prevalence of BKPyV and JCPyV in Asian regions. For this purpose, a thorough search of available online resources was performed. As a result, we retrieved 24 studies for BKPyV and 22 studies for JCPyV, that describe their prevalence in Asia. These studies unanimously report high occurrence of both BKPyV and JCPyV in Asian populations. The available data from these studies was categorized into two groups: on the basis of prevalence (low, medium and high) and disease development (healthy and diseased). Altogether, Korean population hasbeen evidenced to possess highest frequency of BKPyV (66.7 %), while JCPyV was found to be most prevalent in Taiwan (88 %). Due to high and ubiquitous distribution of these viruses, frequent studies are required to develop a better understanding regarding the epidemiology and pathobiology of these viruses in Asia.

Identification of BK Virus Genotypes in Recipients of Renal Transplant in Vietnam

OBJECTIVES

This study aims to investigate the prevalence and distribution of BK polyomavirus (BKV) genotypes in recipients of renal transplant in Vietnam.

METHODS

One hundred six patients who underwent renal transplantation were included in this study. These patients were from the Department of Nephrology, Military Hospital 103, Vietnam Military Medical University. Quantification and genotyping of the BK virus was performed using in-house molecular methods from urine and plasma samples.

RESULTS

BKV infection was detected in 82 patients (77.4%), including 58 patients who had the presence of both BK viremia and BK viruria, and 24 patients (22.60%) with BKV positive findings in the urine alone. Particularly, 16 patients (15.09%) had high BK viremia >10⁴ copies/mL and 20 patients (18.9%) had BK viruria >10⁷ copies/mL. BK virus nephropathy (BKVN) was confirmed in 6 patients (5.66%) by immunohistochemistry examination. Genotyping of BKV was performed successfully in 50 out of the 82 patients, with 36 out of 50 (72%) belonging to the BKV-I subtype and 14 out of 50 (28%) belonging to the BKV-IV subtype; no cases of genotypes II or III were observed. Using phylogenetic analysis of the subgroups, the BKV-I/b-1 subtype was found the predominant subgroup (100%), whereas BKV-IV included 21.43% of IV/a-1, 6.67% of IV/a-2, and 50% of IV/c-1, respectively. There remain 3 cases of BKV-IV (21.43%) that could not be categorized into any subgroups. In the 6 patients diagnosed BKVN, 5 of them were infected with subgroup I/b-1 (83.3%) and 1 patient was infected with subgroup IV/c-1 (16.7%). No significant difference between BKV genotypes was observed in relation to age, sex, HLA mismatch, viral load, BKVN, and immunosuppressive therapy.

CONCLUSIONS

This research indicated a high prevalence of BKV infection and BKV-I was predominant, followed by BKV-IV among recipients of renal transplant in Vietnam.

Prevalence and Risk Factors of BK Viremia and Clinical Impact of BK Virus Surveillance on Outcomes in Kidney Transplant Recipients: A Single-Center Cross-Sectional Study

OBJECTIVES

BK virus is a polyomavirus that can cause nephropathy and graft loss after kidney transplant. The aim of our study was to screen the BK viremia prevalence, to understand the value of the inter-vention for BK virus nephropathy, and to determine the risk factors associated with BK viremia after kidney transplant in our center.

MATERIALS AND METHODS

Our retrospective cross-sectional study included 91 adult kidney transplant recipients who were seen between 2015 and 2017 and who had follow-up from 1 month to over 2 years. BK viremia was evaluated by use of plasma quantitative polymerase chain reaction. The prevalence of BK viremia and the clinical treatments and outcomes of BK virus nephropathy were assessed.

RESULTS

The prevalence of BK viremia was 5.5% (5/91 patients). BK virus nephropathy was confirmed by allograft biopsy in 4.4% (4/91 patients) of all patients. Delayed graft function was found to be an independent risk factor for BK viremia (P < .001). Patients with BK viremia had significantly higher serum creatinine levels (P = .04). Patients who were diagnosed with BK viremia at 1 to 5 years after kidney transplant had higher serum creatinine (P = .02) and uric acid levels (P = .02). After reduction or discontinuation of calcineurin inhibitor, BK virus was cleared in all patients with BK virus nephropathy, with higher level of serum creatinine but no graft loss.

CONCLUSIONS

Delayed graft function was considered as a risk factor for viremia. Early detection of BK viremia replication is important. The strategy of reduction of immunosuppression was effective for BK virus nephropathy and graft function improvement.

Comparison of Transplant Outcomes for Low-level and Standard-level Tacrolimus at Different Time Points after Kidney Transplantation

BACKGROUND

Optimal tacrolimus (TAC) trough levels for different periods after kidney transplantation (KT) has not been definitely established. This study aimed to investigate transplant outcomes of low-level (LL) and standard-level (SL) TAC according to post-transplant period.

METHODS

A total of 278 consecutive kidney transplant recipients (KTRs) receiving TAC-based immunosuppression were divided into LL and SL-TAC groups (4-7 and 7-12 ng/mL for 0-2 months, 3-6 and 6-10 ng/mL for 3-6 months, 2-5 and 5-8 ng/mL for 7-12 months, respectively) according to TAC trough level at each period. We compared estimated glomerular filtration rate (eGFR), biopsy-proven acute rejection (BPAR), de novo donor-specific antibody (dnDSA), calcineurin inhibitor (CNI) toxicity, opportunistic infection, and allograft survival.

RESULTS

SL-TAC group showed significantly higher mean eGFR at 0-2 months than LL-TAC group (72.1 ± 20.3 vs. 64.2 ± 22.7 mL/min/1.73m²; P = 0.003). Incidence of BPAR at 7-12 months was significantly lower in SL-TAC group than in LL-TAC group (0.0% vs. 3.9%; P = 0.039). Patients with persistent SL-TAC lasting 12 months showed higher eGFR at 7-12 months than those with persistent LL-TAC (65.5 ± 13.0 vs. 57.9 ± 13.9 mL/min/1.73m²; P = 0.007). No significant differences in dnDSA, CNI toxicity, serious infections, or allograft survival were observed.

CONCLUSIONS

Maintenance of proper TAC trough level after 6 months could reduce BPAR without adverse drug toxicities in KTRs. Moreover, persistent SL-TAC during the first year after KT might have a beneficial effect on a trend for a lower incidence of dnDSA and better renal allograft function.

BK virus as a mediator of graft dysfunction following kidney transplantation

PURPOSE OF REVIEW

BK virus is a significant risk factor for kidney allograft dysfunction and loss among renal transplant recipients. Currently, there is no proven effective treatment except for the reduction of immunosuppression. In this review, we discuss diagnostic challenges and current treatment options for BK in kidney transplant recipients.

RECENT FINDINGS

Antiviral and antibiotic therapies have been employed for BK viraemia with variable efficacy. In addition, novel therapeutic regimens such as adoptive transfer of targeted T cells have been described as possible treatment options for recipients with BK nephropathy. BK can also be seen in the native kidneys of pancreas, heart, lung and liver transplant recipients, suggesting that BK screening measures should be employed to other solid organ transplant recipients.

SUMMARY

Early screening for BK combined with reduction of immunosuppression remains the mainstay of treatment for BK viraemia. New therapeutic advances demonstrate promise in vitro; however, the in-vivo efficacy will be demonstrated by future studies.

T cell therapies for human polyomavirus diseases

Rapid restoration of virus-specific T immunity via adoptive transfer of ex vivo generated T cells has been proven as a powerful therapy for patients with advanced cancers and refractory viral infections such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV). BK virus (BKV), John Cunningham virus (JCV), and Merkel cell carcinoma virus (MCV) are the members of the rapidly growing human polyomavirus (hPyV) family that commonly infects most healthy humans. These viruses have a clearly established potential for causing severe end-organ damage or malignant transformation, especially in individuals with weakened immunity who are unable to mount or regain endogenous T-cell responses as a result of underlying leukemia or iatrogenic immunosuppression in autoimmunity, bone marrow and solid organ transplant settings. Here we will discuss recent advances in using T-cell-based immunotherapies to save patients suffering from PyV-associated diseases including hemorrhagic cystitis, BKV virus-associated nephropathy, and JC-associated progressive multifocal leukoencephalopathy (PML). We will also review progress in the understanding of Merkel cell carcinoma (MCC) as a virally driven tumor that is amenable to immune intervention and can be targeted with adoptively transferred T cells specific for viral oncoproteins.

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

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