BK viral disease in renal transplantation

Polyomavirus nephropathy: diagnosis, histologic features, and differentiation from acute rejection

Polyomaviruses, particularly BK virus, are ubiquitous latent infections that may reactivate with immunosuppression during kidney transplantation, resulting in polyomavirus nephropathy (PVN). The levels of viruria and viremia serve as tools for screening and making a presumptive diagnosis of PVN, respectively, while a definitive diagnosis requires a kidney biopsy. There are histologic classifications of PVN based on the extent of tubular cell viral infection, interstitial fibrosis, and interstitial inflammation. These classifications correlate to some degree with graft function and loss, aiding in determining treatment efficacy and prognostication. PVN has histologic overlap with acute cell-mediated rejection, making the differential diagnosis challenging, although there are suggestive features for these different causes of graft dysfunction. This article reviews the diagnosis, histologic findings, and classifications of PVN, and discusses how to differentiate viral nephropathy from acute rejection.

Treatment of BK virus with a stepwise immunosuppression reduction and intravenous immunoglobulin in pediatric kidney transplant

BACKGROUND

BKV and BKVN are common in pediatric kidney transplant, but there is limited data on treatment approaches. Our objective was to study the prevalence of BKV and BKVN utilizing only plasma qPCR and report treatment outcomes with stepwise IR and IVIG.

METHODS

A retrospective study of all pediatric kidney transplants from 2013 to 2020. Excluded patients >21 years at transplant and immediate graft failure. Surveillance was conducted using only plasma BK qPCR at 1, 3, 6, 9, 12, 18, and 24 months and annually. BKV defined as ≥250 copies/ml and resolution as <250 copies/ml. Presumed BKVN as >10 000 copies/ml despite IR; and BKVN if confirmed on histology.

RESULTS

Fifty-six patients were included in the study; 20 (35.7%) had BKV. BKV was associated with longer duration of stent, 40 vs. 33.5 days (p = .004). Two patients (3.5%) had confirmed, and 2(3.5%) had presumed BKVN. The first-line treatment was IR in 100% of patients. BKVN confirmed and presumed received IVIG every month for six doses. Viral resolution was achieved in 70%, and no difference was noted in estimated glomerular filtration rate between BKV and non-BKV group (p = .438). There were no rejection episodes, and graft survival was 100% over median follow-up of 3 years.

CONCLUSIONS

Plasma qPCR alone is adequate for screening and monitoring treatment of BKV and BKVN. A stepwise IR and IVIG resulted in BKV resolution in the majority of patients. Larger studies are required to study the role of IVIG in the treatment of BKVN.

An application of the 2018 Banff Classification for BK polyomavirus-associated nephropathy in renal transplantation

BACKGROUND

There is still a lack of a recognized morphological classification of BK viral nephropathy (BKVN) which can better reflect the clinical manifestations and prognosis.

METHODS

We retrospectively analyzed the data of 53 patients with BKVN in our center from January 2011 to December 2018 and evaluated the new Banff 2018 classifications' predictive value for the graft prognosis.

RESULTS

The period between transplantation and BKVN diagnosis lasted for 10.3 months (IQR, 5.3-21.9 months). The main reason (92.5%) for puncture was the increase of blood serum creatinine. Of the 53 patients diagnosed with BKVN, 100% were positive for urinary BK virus-DNA, and the viral load was 1.4 × 10⁸  copies/mL (IQR, 3.7 × 10⁴ -1.3 × 10¹¹  copies/mL); 75.5% were positive for blood BK virus-DNA, and the viral load was 3.3 × 10⁴  copies/mL (IQR, 0-2.8 × 10⁷  copies/mL). There were five cases in class 1, 31 cases in class 2, and 17 cases in class 3; the viral load of urine BK was 3.3 × 10⁸ , 1.4 × 10⁸ , and 6.3 × 10⁷  copies/mL (P > .05); the viral load of blood BK was 3.3 × 10⁴ , 3.3 × 10⁴ , and 3.3 × 10⁴  copies/mL (P > .05); the 1-year graft survival rates were 100%, 90.3%, and 52.9%, respectively (P < .05).

CONCLUSION

BKVN mostly occurs within 1 year after transplantation. There is no correlation between BK virus load in hematuria and pathological damage at the time of diagnosis. The 2018 Banff Classification for BKVN can better indicate the prognosis of graft.

Impact of Pneumocystis jirovecii pneumonia on kidney transplant outcome

Backgrounds

Pneumocystis jirovecii pneumonia (PCP) remains an important cause of morbidity and mortality in kidney transplant recipients. While the acute phase toxicity in patients with PCP is well-characterized, there is a lack of data on the effects of PCP on long-term graft outcome.

Method

This retrospective observational study analyzed 1502 adult patients who underwent kidney transplantation at Seoul National University Hospital between 2000 and 2017. After a propensity score matching was performed, the graft and survival outcomes were compared between PCP-negative and PCP-positive groups.

Results

A total of 68 patients (4.5%) developed PCP after transplantation. The multivariable Cox analysis showed that positivity for cytomegalovirus and lack of initial oral antibiotic prophylaxis were risk factors of post-transplant PCP. The PCP-positive group had higher hazard ratios of graft failure [adjusted hazard ratio (HR), 3.1 (1.14–8.26); P = 0.027] and mortality [adjusted HR, 11.0 (3.68–32.80); P < 0.001] than the PCP-negative group. However, the PCP event was not related with subsequent development of de novo donor-specific antibodies or pathologic findings, such as T-cell or antibody mediated rejection and interstitial fibrosis and tubular atrophy.

Conclusions

PCP is a risk factor of long-term graft failure and mortality, irrespective of rejection. Accordingly, appropriate prophylaxis and treatment is needed to avoid adverse transplant outcomes of PCP.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1407-x) contains supplementary material, which is available to authorized users.

Quantitative detection of BK virus in kidney transplant recipients: a prospective validation study

Introduction:

BK virus (BKV) infection in renal transplant patients may cause kidney allograft dysfunction and graft loss. Accurate determination of BKV viral load is critical to prevent BKV-associated nephropathy (BKVAN) but the cut-off that best predicts BKVAN remains controversial.

Objective:

To evaluate the performance of a commercial and an in-house qPCR test for quantitative detection of BK virus in kidney transplant recipients.

Methods:

This was a prospective study with kidney transplant recipients from two large university hospitals in Brazil. Patients were screened for BKV infection every 3 months in the first year post-transplant with a commercial and an in-house real time polymerase chain reaction (qPCR) test. BKVAN was confirmed based on histopathology. The area under the curve for plasma qPCR was determined from receiver operating characteristic analysis.

Results:

A total of 200 patients were enrolled. Fifty-eight percent were male, 19.5% had diabetes mellitus, and 82% had the kidney transplanted from a deceased donor. BKV viremia was detected in 32.5% and BKVAN was diagnosed in 8 patients (4%). BKVAN was associated with viremia of 4.1 log copies/mL, using a commercial kit. The cut-off for the in-house assay was 6.1 log copies/mL. The linearity between the commercial kit and the in-house assay was R²=0.83.

Conclusion:

Our study shows that marked variability occurs in BKV viral load when different qPCR methodologies are used. The in-house qPCR assay proved clinically useful, a cheaper option in comparison to commercial qPCR kits. There is an urgent need to make BKV standards available to the international community.

[Early intervention of BK virus replication promotes stabilization of renal graft function]

OBJECTIVE

To investigate the optimal time window for intervention of BK virus (BKV) replication and its effect on the outcomes of kidney transplant recipients (KTRs).

METHODS

A retrospective analysis of the clinical data and treatment regimens was conducted among KTRs whose urine BKV load was ≥1.0×10⁴ copies/mL following the operation between April, 2000 and April, 2015. KTRs with urine BKV load <1.0×10⁴ copies/mL matched for transplantation time served as the control group.

RESULTS

A total of 54 recipients positive for urine BKV were included in the analysis. According to urine BKV load, the recipients were divided into 3 groups: group A with urine BKV load of 1.0×10⁴-1.0×10⁷ copies/mL (n=22), group B with urine BKV load >1.0×10⁷ copies/mL (n=24), and group C with plasma BKV load ≥1.0×10⁴ copies/mL (n=8); 47 recipients were included in the control group. During the follow-up for 3.2-34.5 months, the urine and plasma BKV load was obviously lowered after intervention in all the 54 BKV-positive recipients (P<0.05). Eighteen (81.82%) of the recipients in group A and 19 (79.17%) in group B showed stable or improved estimated glomerular filtration rate (eGFR) after the intervention; in group C, 4 recipients (50%) showed stable eGFR after the intervention. In the last follow-up, the recipients in groups A and B showed similar eGFR with the control group (P>0.05), but in group C, eGFR was significantly lower than that of the control group (P=0.001). The recipients in group A and the control group had the best allograft outcome with stable or improved eGFR.

CONCLUSION

Early intervention of BKV replication (urine BKV load ≥1.0×10⁴ copies/mL) in KTRs with appropriate immunosuppression reduction can be helpful for stabilizing the allograft function and improving the long-term outcomes.

Increased Frequency of BK Virus-Specific Polyfunctional CD8+ T Cells Predict Successful Control of BK Viremia After Kidney Transplantation

BACKGROUND

BK virus infection remains an important cause of loss of allograft function after kidney transplantation. We sought to determine whether polyfunctional T cells secreting multiple cytokines simultaneously, which have been shown to be associated with viral control, could be detected early after start of BK viremia, which would provide insight into the mechanism of successful antiviral control.

METHODS

Peripheral blood mononuclear cells collected during episodes of BK viral replication were evaluated by multiparameter flow cytometry after stimulation by overlapping peptide pools of BK virus antigen to determine frequency of CD8+ and CD4+ T cells expressing 1 or more cytokines simultaneously, as well as markers of T-cell activation, exhaustion, and maturation.

RESULTS

BK virus controllers, defined as those with episodes of BK viremia of 3 months or less, had an 11-fold increase in frequency of CD8+ polyfunctional T cells expressing multiple cytokines, as compared with patients with prolonged episodes of BK viremia. Patients with only low level BK viremia expressed low frequencies of polyfunctional T cells. Polyfunctional T cells were predominantly of the effector memory maturation subtype and expressed the cytotoxicity marker CD107a.

CONCLUSIONS

Noninvasive techniques for immune assessment of peripheral blood can provide insight into the mechanism of control of BK virus replication and may allow for future patient risk stratification and customization of immune suppression at the onset of BK viremia.

Minimization of maintenance immunosuppressive therapy after renal transplantation comparing cyclosporine A/azathioprine or cyclosporine A/mycophenolate mofetil bitherapy to cyclosporine A monotherapy: a 10-year postrandomization follow-up study

Long-term outcomes in renal transplant recipients withdrawn from steroid and submitted to further minimization of immunosuppressive regimen after 1 year are lacking. In this multicenter study, 204 low immunological risk kidney transplant recipients were randomized 14.2 ± 3.7 months post-transplantation to receive either cyclosporine A (CsA) + azathioprine (AZA; n = 53), CsA + mycophenolate mofetil (MMF; n = 53), or CsA monotherapy (n = 98). At 3 years postrandomization, the occurrence of biopsy for graft dysfunction was similar in bitherapy and monotherapy groups (21/106 vs. 26/98; P = 0.25). At 10 years postrandomization, patients' survival was 100%, 94.2%, and 95.8% (P = 0.25), and death-censored graft survival was 94.9%, 94.7%, and 95.2% (P = 0.34) in AZA, MMF, and CsA groups, respectively. Mean estimated glomerular filtration rate was 70.4 ± 31.1, 60.1 ± 22.2, and 60.1 ± 19.0 ml/min/1.73 m(2), respectively (P = 0.16). The incidence of biopsy-proven acute rejection was 1.4%/year in the whole cohort. None of the patients developed polyomavirus-associated nephropathy. The main cause of graft loss (n = 12) was chronic antibody-mediated rejection (n = 6). De novo donor-specific antibodies were detected in 13% of AZA-, 21% of MMF-, and 14% of CsA-treated patients (P = 0.29). CsA monotherapy after 1 year is safe and associated with prolonged graft survival in well-selected renal transplant recipient (ClinicalTrials.gov number: 980654).

Ultrasound findings of BK polyomavirus-associated nephropathy in renal transplant patients

BK polyomavirus (BKV) is an emerging pathogen in immunocompromised patients. BKV infection occurs in 1-9 % of renal transplants and causes chronic nephropathy or graft loss. Diagnosis of BKV-associated nephropathy (BKVAN) is based on detection of viruria then viremia and at least a tubule-interstitial nephritis at renal biopsy. This paper describes the ultrasound and color Doppler (US-CD) features of BKVAN. Seventeen patients affected by BKVAN were studied using a linear bandwidth 7-12 MHz probe. Ultrasound showed a widespread streak-like pattern with alternating normal echoic and hypoechoic streaks with irregular edges from the papilla to the cortex. Renal biopsy performed in hypoechoic areas highlighted the typical viral inclusions in tubular epithelial cells. Our experience suggests a possible role for US-CD in the non-invasive diagnosis of BKVAN when combined with blood and urine screening tests. US-CD must be performed with a high-frequency linear probe to highlight the streak-like pattern of the renal parenchyma.

Quantitative analysis of BKV-specific CD4+ T cells before and after kidney transplantation

BACKGROUND

BK virus (BKV) is the main infectious cause of renal allograft dysfunction. Although recent studies showed an inverse correlation between BKV-specific T-cell responses and viral load after transplantation, the importance of pre-transplant response in the process of virus reactivation has only been studied once. In this study, we aimed to determine whether pre-transplant CD4+ T-cell response can be used for prediction of BKV reactivation and BKV nephropathy (BKVN), by a method that can practically be used in routine patient monitoring.

METHODS

BKV-specific CD4+ T-cell responses of 31 kidney recipients (all from live donors) were measured by an IFN-γ-enzyme-linked-immunospot (ELISPOT) method using mixture of peptides, at day 0 and +1, +3, and +6 months posttransplant. Additionally, seven other reactivation patients as another group were also analyzed. BKV viral loads in plasma were measured by real-time polymerase chain reaction (PCR). Responses of 10 healthy people were also included as controls in the analysis.

RESULTS

All but one patient and all of the controls had detectable CD4+ T-cell responses. Reactivation occurred in 8 out of 31 patients. There was no significant association between pretransplant BKV-specific CD4+ T-cell responses and BKV reactivation and between BKV DNA levels and CD4+ T-cell responses. In the additional group consisting of reactivation patients, four patients who had BKVN showed negative correlation between BKV-DNA levels and BKV-specific CD4+ T-cell responses (p<0.05). One patient who developed BKVN, however, was not able to mount a similar CD4+ T-cell response to viral reactivation despite immunosuppressive reduction.

CONCLUSION

Even though our cohort is small, our results may suggest that pre-transplant measurement of BKV specific CD4+ T-cell response may not be necessary, and that post-transplant monitoring, particularly during reactivation, may be more helpful in the management of the infection.

Adjuvant Ciprofloxacin for Persistent BK Polyomavirus Infection in Kidney Transplant Recipients

Background. BK virus (BKV) infection is a common complication following kidney transplantation. Immunosuppression reduction is the cornerstone of treatment while adjuvant drugs have been tried in small uncontrolled studies. We sought to examine our center's experience with the use of ciprofloxacin in patients with persistent BKV infection. Methods. Retrospective evaluation of the effect of a 30-day ciprofloxacin course (250 mg twice daily) on BKV infection in kidney transplant recipients who had been diagnosed with BK viruria ≥106 copies/mL and viremia ≥500 copies/mL and in whom the infection did not resolve after immunosuppression reduction and/or treatment with other adjuvant agents. BKV in plasma and urine was evaluated after 3 months following treatment with ciprofloxacin. Results. Nine kidney transplant recipients received ciprofloxacin at a median of 130 days following the initial reduction in immunosuppression. Three patients showed complete viral clearance and another 3 had a ≥50% decrease in plasma viral load. No serious adverse events secondary to ciprofloxacin were reported and no grafts were lost due to BKV up to 1 year after treatment. Conclusion. Ciprofloxacin may be a useful therapy for persistent BKV infection despite conventional treatment. Randomized trials are required to evaluate the potential benefit of this adjuvant therapy.

The risk of polyomavirus-associated graft nephropathy is increased by a combined suppression of CD8 and CD4 cell-dependent immune effects

Polyomavirus-associated graft nephropathy (PAN) has emerged as a significant risk factor for kidney graft loss. We analyzed intracellular cytokine responses for possible protective versus permissive immunologic effects on BK-virus replication. One hundred five renal transplant patients included in a prospective single-center study were randomized to receive cyclosporine mycophenolate mofetil (MMF) (CM: n = 31), tacrolimus (Tac)/MMF (TM: n = 32) or Tac/MMF with conversion to everolimus (TErl; n = 32). Ten patients were not randomized (NR) due to contraindications to MMF. The immunosuppressive therapy was monitored pre- and posttransplantation at 4, 12, and 24 months using triple fluorescence flow cytometry for intracellular interleukin (Il)-2 Il-4 and interferon (IFN)-γ production in phorbol myristate acetate- and lipopolysaccharide- stimulated lymphocyte cultures. BK viremia screening was performed by reverse-transcriptase polymerase chain reaction testing on days 0, 14, 30, 60, 90, 120, 180, 270, 360, and 720. Seven of 105 (6.7%) patients developed biopsy-proven PAN (CM: n = 1, TM: n = 3, TErl: n = 2, NR: n = 1), among whom 4 lost their grafts (TM: n = 1, TErl: n = 2, NR: n = 1). Twenty-one of 105 (20.0%) patients had documented BK viremia. BK viremia which preceded PAN in all cases, was significantly associated with TM immunosuppression: 4/31 (12.9%) CM: 11/32 (34.4%) TM; 5/32 (15.6%) TErl, and 1/10 (10.0%) NR patients (P = .034). BK-viremic patients showed significantly diminished CD8(+) T-cell Il-2 production at 120 days (P = .011) and 1 year posttransplantation (P = .014) compared with non-BK-viremic patients. Patients with PAN displayed significantly lower CD4(+) T-cell Il-4 responses at 1 and 2 years after transplantation (1 year: P = .007; 2 years: P = .001) with diminished IFN-γ responses at 1 year after transplantation (P = .011). Our analysis showed the incidence of BK viremia to be increased among patients with defective cytotoxic CD8(+) T-cell -dependent immune reactivity. Recipients who progressed from BK viremia to overt PAN showed an additional immunologic defect in CD4(+) T-cell function. Patients on a Tac- plus MMF-based immunosuppression were at higher risk to develop BK viremia.

Currently recommended BK virus (BKV) plasma viral load cutoff of ≥4 log10/mL underestimates the diagnosis of BKV-associated nephropathy: a single transplant center experience

BACKGROUND

BK virus (BKV)-associated nephropathy (BKVAN) is a major cause of renal dysfunction and graft loss in renal transplant recipients. Monitoring plasma BK viral load (BKVL) is the recommended screening tool to predict BKVAN. American Society of Transplantation (AST) guidelines define a BKVL of ≥4 log10/mL (10,000 copies) as presumptive BKVAN and recommend reduction in immunosuppression. We evaluated the clinical sensitivity of the quantitative BKV DNA assay in predicting risk for BKVAN using the AST-recommended BKVL cutoff.

METHODS

In a retrospective, single-center study, all patients who underwent renal transplant at Henry Ford Hospital from January 2008 to August 2011 were analyzed (n = 490). Plasma BKVL Assay A (commercial large T antigen-based polymerase chain reaction [PCR]) was done in all patients. Renal biopsy was done if there was a rise in serum creatinine ≥0.5 mg from baseline. BKVAN was confirmed by biopsy. As a subset to this study, from the same cohort, data for a set of 20 consecutive Assays A and B (in-house VP1-based PCR assay) from 15 patients over a period of 3 months were collected. Differences in physicians' clinical decision-making (CDM) were analyzed between the 2 assays using chi-square test.

RESULTS

A total of 413 patients met the inclusion criteria, of which 222 patients had BK viremia. Among the 248 patients who had a renal biopsy done, 31 (12.5%) were found to have BKVAN. Eleven of the 31 (35%) patients had BKVL consistently <4 log10/mL, and thus were not diagnosed to have BKVAN using the AST-recommended BKVL cutoff of ≥4 log10/mL. A total of 8 patients lost their graft owing to BKVAN, including 3 patients with BKVL <4 log10/mL. Using a cutoff point of plasma BKVL of ≥4 log10/mL, the sensitivity, specificity, positive predictive value, and negative predicative value of the PCR Assay A for the diagnosis of biopsy-proven BKVAN were 64.5%, 98.4%, 87.0%, and 94.5%, respectively, and for the diagnosis of presumptive nephropathy were found to be 76.6%, 99.4%, 95.8%, and 96.4%, respectively. In the second part of the study, presumptive nephropathy was detected in 8 samples using Assay A and 14 samples using Assay B. Six samples in Assay A would have led to no changes in the CDM in terms of reduction in immunosuppression. Kidney biopsy was carried out in 5 patients, 4 of whom had BKVAN and had Assay B log count of ≥5. If Assay A had been used in CDM, BKVAN would have been missed in 1 patient.

CONCLUSION

Utilizing the current AST guideline cutoff of ≥4 log10 /mL, the PCR Assay A underestimated the diagnosis of BKVAN. Urgent standardization of the various BKVL assays and establishment of universal cutoff points is imperative to avoid BKVAN-related graft loss.

Identification of novel HLA class II target epitopes for generation of donor-specific T regulatory cells

Therapies capable of generating host T regulatory cells (T(R)) responsive to donor-specific HLA-class II minor histocompatibility antigens have the potential to promote tolerance of a transplanted organ. Our group has developed a novel approach for the identification of potentially therapeutic T(R) target antigens. We perform parallel non-synonymous SNP genotyping of HLA-identical subject pairs to identify peptide variations expressed by only one of the two subjects. Variant peptide pairs are then evaluated for binding a shared HLA-class II allele. Minor peptides predicted to bind HLA-class II with greater affinity than the common variant peptide are tested for HLA class II binding and in vitro induction of suppressive CD4+ T cells. Using this approach we have identified multiple pairs of variant peptides capable of differential binding and induction of suppressive CD4+ T cells. These data demonstrate the feasibility of identifying potentially therapeutic HLA class II minor antigens for generation of donor-specific T(R).

The impact of infection and tissue damage in solid-organ transplantation

Investigations over the past two decades are revealing complexities in the regulation of the innate immune response, and how this response, in turn, controls adaptive immunity. Microbial exposure, infections and tissue damage that accompany solid-organ transplantation result in the release of pathogen- and damage-associated molecular patterns, as well as pathogen- or allograft-derived antigens. Here, we review these triggers of innate and adaptive immunity, and discuss emerging paradigms of the many ways in which infections and tissue damage might directly or indirectly affect alloreactivity and the outcome of transplanted allografts.

Leflunomide efficacy and pharmacodynamics for the treatment of BK viral infection

BACKGROUND AND OBJECTIVES

BK virus is an infection in kidney transplantation patients jeopardizing graft survival. Unfortunately, there is no consensus on treatment of BK viremia and nephropathy. Leflunomide has been studied for the treatment of BK viremia and nephropathy, but there are limited data on the utility of leflunomide therapeutic drug monitoring. This study aimed to determine if a pharmacodynamic relationship exists between BK viral load reduction and leflunomide metabolite, A77 1726, serum concentrations.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study was a retrospective, single-center, longitudinal analysis of patients identified with BK viremia with or without nephropathy. Patients were grouped according to whether they received leflunomide. All BK viral PCR and A77 1726 concentrations were analyzed to determine pharmacodynamics, and were correlated with clinical outcomes.

RESULTS

Of 76 patients identified, 52 received leflunomide therapy and 24 did not. Patients who received leflunomide were further analyzed according to A77 1726 concentrations and BK clearance; there was no difference in BK clearance. There was a lack of correlation between A77 1726 concentrations and log change in BK viral PCR concentration. Multivariate analysis demonstrated that mycophenolate mofetil discontinuation, BK viremia without nephropathy, and mean BK viral load were significantly associated with BK viral clearance; leflunomide use lacked this association.

CONCLUSIONS

Pharmacodynamic analysis revealed no association between A77 1726 concentrations and BK viral PCR reductions. Multivariate analysis demonstrated that leflunomide therapy was not associated with BK viral clearance. Randomized studies are needed to determine the utility of leflunomide for BK viremia and nephropathy.