Outcomes of repeat kidney transplantation following prior graft failure secondary to BK nephropathy: A single-center retrospective study.

BACKGROUND: BK virus is associated with development of nephropathy (BKVN) that can lead to graft failure after renal transplantation. There are limited data on rates of recurrence and outcomes of repeat renal transplantation after prior graft loss caused by BKVN. METHODS: After IRB approval, data on all patients who underwent a repeat renal transplantation after prior graft failure as a result of BKVN were identified. Data on management of patients prior to retransplantation, induction and maintenance immunosuppression, and key clinical and virologic outcomes were collected. Descriptive statistics were used for analysis. RESULTS: Thirteen patients were identified over a 13-year period, and follow-up of these patients occurred for a median of 4.7 years. Most patients have previous renal transplants removed prior to (7/13, 53.8%) or at the time of retransplantation (3/13, 23.1%). Close virologic monitoring of serum and urine, coupled with early immunosuppression minimization, was associated with few patients developing BK viruria above 1 × 107 c/mL (4/13, 30.8%), BK viremia above 10,000 c/mL (2/13, 15.4%), and biopsy-proven BKVN (1/12, 8.3%); most (8/13, 61.5%) developed BK viruria at any level. Renal function at 1 year post-retransplantation was generally excellent and only 1 patient developed graft failure caused by recurrent focal segmental glomerulosclerosis. In our review of the literature, 2 large observational studies of the UNOS database as well as our analysis of case reports showed excellent graft survival and very low rates of recurrent BKVN leading to graft loss. CONCLUSIONS: Retransplantation after prior graft failure caused by BKVN generally has low rates of recurrence when coupled with close monitoring and early immunosuppression minimization. Removal of failed renal transplant may allow easier monitoring for recurrence.

Risk factors for progression from low level BK dnaemia to unfavorable outcomes after BK management via immunosuppressive reduction.

BACKGROUNDS: Effective management of BK viremia (BKPyV-DNAemia) in kidney transplant recipients (KTRs) involves regular monitoring and adjustment of immunosuppression. With this strategy, the majority of patients will clear BK or have ongoing, but non-significant, low-level BKPyV-DNAemia. However, despite adjustments, some will develop more severe sequelae of BK including BKPyV-DNAemia >5 log10 copies/mL and BK nephropathy, and others may develop de novo DSA (dnDSA) or acute rejection (AR). METHODS: This was a single-center study of KTRs transplanted at the University of Wisconsin-Madison between 01/01/2015 and 12/31/2017. In this study, we sought to elucidate characteristics associated with the progression of BKPyV-DNAemia to unfavorable outcomes after decreasing immunosuppressive medications for the management of BK viremia as described in consensus guidelines. RESULTS: A total of 224 KTRs fulfilled our selection criteria; 118 (53%) resolved or had persistent low DNAemia, 64 (28%) had severe BK/nephropathy, and 42 (19%) developed dnDSA or AR. In multivariable analysis, female gender (HR: 2.05; 95% CI: 1.08-3.90; P = .02); previous rejection (HR: 2.90; 95% CI: 1.04-8.12; P = .04), and early infection (HR: 0.81; 95% CI: 0.72-0.90; P < .001) were associated with the development of severe BK/nephropathy. Conversely, non-depleting induction at transplant (HR: 2.06; 95% CI: 1.03-4.11; P = .03), HLA mismatches >3 (HR: 2.27; HR: 1.01-5.06; P = .04), and delayed graft function (HR: 4.14; 95% CI: 1.12-15.28; P = .03) were associated with development of dnDSA and/or rejection. CONCLUSION: Our study suggests that almost half of KTRs with BKPyV-DNAemia managed by our immunosuppressant adjustment protocol progress unfavorably. Identification of these risk factors could assist the frontline clinician in creating an individualized immunosuppressive modification plan potentially mitigating negative outcomes.

Routine immunohistochemistry study for polyomavirus BK nephropathy in transplanted kidney biopsies, is it recommended?

BACKGROUND: Early diagnosis and treatment of Polyomavirus BK Nephropathy (PVBKN) is a challenging issue in the management of patients with kidney transplantation. Currently, histopathologic diagnosis is the gold standard method for diagnosis of PVBKN. However, typical viral inclusions may not be found in early stages of the PVBKN and should, instead, be diagnosed using immunohistochemistry (IHC) study. There is no clear consensus about routine IHC tests in the pathologic evaluation of transplanted kidney biopsy samples. MATERIAL AND METHODS: The current study was conducted on transplanted kidney biopsy samples, since 2016 to 2019. The patients who have presented with new onset of allograft dysfunction, at least 2 weeks after transplantation surgery, were included in our study. All these biopsy samples were evaluated with routine renal biopsy stains as well as IHC for SV40 (Simvian Virus 40) antigen. The identification of typical nuclear virus inclusion body and any nuclear positive staining on IHC (≥1+ positive result) were considered as definite evidence of PVBKN. Sensitivity, specificity, Positive Predictive and Negative Predictive Values (PPV and NPV) of histopathologic assessment without IHC study were evaluated. RESULTS: Among 275 included cases, 18 (6.5%) patients with PVBKN were diagnosed. In patients with PVBKN, typical viral inclusions were detected in 14 samples (77.7%), on primary histopathological examination. However, virus-infected cells were identified just after IHC study in 4 (22.2%) of patients. Sensitivity, Specifity, PPV and NPV of morphologic histopathological assay without IHC for detection of PVBKN was 77.7, 100, 100 and 98.4% respectively. CONCLUSION: Routine IHC study for SV40 in all transplanted kidney biopsy samples with new onset of allograft dysfunction, will enhance the diagnostic sensitivity of early stage disease detection.

Intravenous Immunoglobulin Administration Significantly Increases BKPyV Genotype-Specific Neutralizing Antibody Titers in Kidney Transplant Recipients.

BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) is one of the major causes of kidney graft dysfunction, and there are no BKPyV-specific antiviral therapies available. BKPyV neutralizing antibodies (NAbs) play key roles in protecting against BKPyV replication and represent a potential therapeutic or preventive strategy. In this study, we evaluated NAb titers in intravenous immunoglobulin (i.v. Ig) preparations and in kidney transplant recipients (KTR) before and after i.v. Ig administration. NAb titers directed against major BKPyV genotypes were measured using a BKPyV pseudovirion system. Thirty-three KTR receiving high (1 g/kg of body weight/day; n = 17) or low (0.4 g/kg/day; n = 16) i.v. Ig doses were included. Median NAb titers in i.v. Ig preparations ranged from 5.9 log10 50% inhibitory concentration (IC50) for genotype I to 4.1 log10 IC50 for genotype IV. A mean of 90% of patients (range, 88% to 100%) displaying low or negative BKPyV NAb titers against genotype I reached 4 log10 IC50 after the first i.v. Ig administration. This value was reached by a mean of 44% (range, 13% to 83%) and 19% (range, 0% to 38%) of patients against genotype II and genotype IV, respectively. The benefit of i.v. Ig administration persisted until the following course of treatment (day 22 ± 7 days) for genotypes I and II, and no cumulative effect was observed through the three doses. Our findings demonstrate that i.v. Ig administration results in a significant increase in BKPyV NAb titers in KTR. These in vitro and in vivo pharmacokinetic data provide the rationale for a proof-of-concept study investigating the efficacy of i.v. Ig for the prevention of BKPyV infection in KTR.

Native kidney BK virus nephropathy, a systematic review.

BACKGROUND: There is a growing base of literature describing BK nephropathy (BKVN) in patients outside of the setting of kidney transplant. Previous systematic reviews of the literature have been limited by methodology or by the scope of patients included. STUDY DESIGN AND METHODS: Systematic Review (Prospero # CRD42018088524). SETTING & POPULATION: Patients without kidney transplant who had biopsy-proven BKVN. SELECTION CRITERIA FOR STUDIES: Full-text articles that describe native BKVN patient cases. ANALYTICAL APPROACH: Descriptive synthesis. RESULTS: The search identified 630 unique articles of which 51 were included in the final review. Sixty-five cases (including two new cases presented in this review) were identified, all but one occurred in the setting of known immunosuppression. LIMITATIONS: The primary limitation was the exclusion of studies that did not fulfill the stringent review criteria. We excluded reports with only a clinical diagnosis of BKVN, such as those with viruria and/or viremia without biopsy. CONCLUSIONS: As of May 2018, there are 65 reported cases of BKVN in native kidneys. This represents the most comprehensive description of biopsy-proven BKVN in native kidneys to date. Evaluation for BK nephropathy should be considered in immunocompromised patients who exhibit unexplained renal failure.

Which is more nephrotoxic for kidney transplants: BK nephropathy or rejection?

Little data exist comparing outcomes following BK nephropathy (BKN) vs acute rejection. We reviewed outcomes among recipients who had a primary diagnosis of biopsy-proven BKN or rejection between 1 and 18 months post-transplant. There were 96 cases of BKN and 256 cases of rejections. We compared outcomes of BKN with all rejection combined and also with cellular rejection. Seven of 256 (2.7%) patients developed BKN after treatment of rejection. Conversely, 8 of 96 (8.3%) developed rejection after BKN. The eGFR at time of diagnosis in the BKN group (33.7 ± 12.6) was lower than the rejection group (44.8 ± 23.3, P < .001). The eGFR at 6 months after diagnosis of BKN was 32.7 ± 14.9 and for rejection was 48.8 ± 20.7 (P ≤ .001). The mean eGFR at 3 years postdiagnosis was 41.6 ± 18.5 in BKN and 53 ± 21.3 for rejection (P = .001). The graft failure incidence rates were similar between 2 groups. A similar pattern was observed comparing BKN with cellular rejection. While the difference in rate of graft loss between BKN and rejection did not reach statistical significance, kidney function up to 3 years after diagnosis was worse for BKN than for rejection, suggesting that BKN is at least as damaging to kidneys as rejection.

De novo donor-specific antibody following BK nephropathy: The incidence and association with antibody-mediated rejection.

BACKGROUND AND OBJECTIVES: The risk of de novo donor-specific antibody (dnDSA) development following BK viremia (BKV) or nephropathy (BKN) after kidney transplant remains unclear. We aimed to evaluate the relationships among dnDSA, BKV (BK blood PCR > 15 000 copies), BKN, antibody-mediated rejection (AMR), and allograft loss. PATIENTS AND METHODS: We performed a retrospective cohort study of 904 solitary kidney transplant recipients transplanted between 10/2007 and 5/2014. Cox proportional hazards regression with time-dependent covariates were used to assess the relationships among BKN, isolated BKV, dnDSA, and the subsequent risk of AMR and allograft loss. RESULTS: In multivariate analysis, we observed that BKN, but not BKV was a risk factor for dnDSA (HR, 3.18, P = .008). Of the patients with BK nephropathy, 14.0% (6/43) developed dnDSA, which occurred within 14 months of BK diagnosis. DnDSA in this setting remains a risk factor for subsequent AMR (HR 4.75, P = .0001) and allograft loss (HR 2.63, P = .018). CONCLUSIONS: BKN is an independent risk factor for development of dnDSA. Improved understanding of the characteristics of patients with BKN who are at highest risk for development of dnDSA would be valuable to customize immunosuppression reduction in this population.

BK viremia surveillance and outcomes in simultaneous pancreas-kidney transplant recipients.

BACKGROUND: While screening for asymptomatic BK viremia (BKV) has been well studied in isolated kidney transplant recipients, there is a paucity of published outcomes in simultaneous pancreas-kidney (SPK) transplant recipients who underwent BKV screening followed by pre-emptive reduction in immunosuppression. METHODS: This is a single-center, retrospective review of 31 consecutive SPK recipients who were transplanted over a 5-year period following the initiation of a serum BKV screening protocol. RESULTS: BK viremia developed in 11 (35.5%) patients, and all patients achieved complete viral clearance following reduction in immunosuppression. Two patients (6.5%) developed BK virus nephropathy, but both had preserved allograft function. One patient developed mild rejection of the kidney allograft following clearance of BKV, and two patients developed mild rejection of the pancreas allograft after reduction in immunosuppression, but there were no kidney or pancreas allograft losses due to rejection. The development of BK viremia did not impact overall patient survival or kidney and pancreas allograft survival. CONCLUSION: Screening asymptomatic SPK recipients for BKV followed by reduction in maintenance immunosuppression appears to be an effective strategy to prevent kidney allograft dysfunction and graft loss due to BK virus nephropathy, without compromising pancreas allograft outcomes.

Ureteral stent duration and the risk of BK polyomavirus viremia or bacteriuria after kidney transplantation.

OBJECTIVES: Ureteral stents are used in kidney transplantation (KTX) to decrease post-operative complications, but they are associated with BK polyomavirus viremia (BKV). Our primary outcome was to determine the association between ureteral stent duration and BKV. Secondary outcome measures were the association between bacteriuria and stent duration or use of ureteral stent strings. METHODS: Between January 2010 and January 2015, 403 patients underwent KTX at the Virginia Mason Medical Center and met inclusion criteria. Stent duration was classified as short (<3 weeks) or long (>3 weeks). Multivariate logistic regression models were created to assess for factors associated with BKV. The covariates in the BKV model were chosen a priori based on stent duration and risk factors previously described in the literature. RESULTS: Ureteral stents were placed in 304 (75.4%) transplants. Stent strings were left attached in 166 (54.6%) patients. On multivariate analyses, long stent duration was significantly associated with increased risk of BKV compared with no stent (odds ratio [OR] 1.92, P=.044, 95% confidence interval [CI] 1.04-3.74). Short stent duration was not associated with BKV. Sixty-two (15.4%) patients had bacteriuria. Bacteriuria was associated with female gender (OR 2.77, P<.001, 95% CI 1.58-4.95), and there was a dose-dependent effect with stent duration compared with no stent-short duration (OR 2.46, P=.049, 95% CI 1.05-6.49) and long duration (OR 3.58, P=.004, 95% CI 1.58-9.25). Stent strings were not associated with either complication. CONCLUSIONS: The association between ureteral stents and BKV may be dose dependent.

The impact of recipient BKV shedding before transplant on BKV viruria, DNAemia, and nephropathy post-transplant: A prospective study.

We previously demonstrated that detectable BKV replication in donor urine pretransplant was significantly associated with post-transplant recipient BKV viremia. In this 4-year prospective study, we assessed whether recipient BKV replication pretransplant was associated with post-transplant viremia/BKV nephropathy. We studied 220 primary adult and pediatric organ transplant recipients for 490 person-years and 2100 clinical visits. BKV viruria was detectable in 28 (16%), 26 adults and two children; and viremia in none pretransplant. Post-transplant viruria occurred in all recipients with pretransplant BKV viruria, significantly more than in recipients without pretransplant viruria on univariate (P<.005) and multivariate analysis including type of organ transplanted and immunosuppression type (P .008). Time to post-transplant viruria was significantly shorter in recipients with pretransplant viruria (P .01). By univariate and multivariate analysis, BKV viruria in recipients pretransplant did not impact post-transplant BKV viremia (P=.97 and .97, respectively) even when stratified by type of organ transplant (kidney P=.6; liver P=.5). The peak serum and urine BKV PCR post-transplant were not significantly different in patients with pretransplant BKV viruria and no one developed BK nephropathy. In conclusion, recipient BKV viruria prior to transplant predicts post-transplant viruria but not viremia or BKV nephropathy.

Combination of Leflunomide and Everolimus for treatment of BK virus nephropathy.

BK nephropathy (BKN) is a common cause of graft dysfunction following kidney transplantation. Minimization of immunosuppressive therapy remains the first line of therapy, but this may lead to rejection and graft loss. In some cases, despite lowering immunosuppression, BK infection can persist, leading to chronic damage and kidney failure. Currently, there is no specific anti-BK viral therapy. Recent in vitro experiments have demonstrated a reduction in BK viral replication when infected cells are treated with the combination of Leflunomide and Everolimus. This study aims to explore the effect of this drugs combination on viral clearance and graft function in patients with persistent disease despite reduction in immunosuppression. We treated three patients with combination Leflunomide and Everolimus. Data on medical history, biochemical parameters and viral loads were collected. Significant improvement in viral loads was observed in two cases with resolution of viremia in another (Table 1). Two recipients had preserved allograft function. The remaining graft was lost because of combination of obstruction and BKN. No adverse reactions such as bone marrow toxicity were observed. Combination of Leflunomide and Everolimus is safe and should be considered as a rescue therapy in treatment of BKN, especially in those who fail to clear this infection despite reduction of immunosuppressive therapy.

Prevalence of polyoma BK virus infection among living-donor renal transplant recipients.

BACKGROUND: Polyomavirus nephropathy (PVN) mainly caused by BK polyomavirus (BKPyV) remains the most common productive viral infection of the kidney in immunosuppressed patients. The diagnosis of PVN is based on the detection of BK viruria and BK viremia in conjunction with histological findings in the graft biopsy. METHODS: Our study was aimed to estimate the prevalence of productive BKPyV infection among renal transplant patients within the first year post-transplant and identify those at risk of developing PVN. Our cross-sectional study was conducted on 134 kidney transplant patients. Evidence of BKPyV replication was assessed by viral quantification of blood and urine samples of studied patients using a quantitative real-time polymerase chain reaction (Q-PCR)PCR), detection of decoy cells in urine cytology smears, histological examination of graft biopsies from Q-PCR BKPyV-positive patients, and immunohistochemical staining by simian virus 40 (SV40) antibody. RESULTS: Significant BKPyV infection was prevalent in 8% (n = 11) of our patients, with a peak of BKPyV infection about 8 months post transplant. BKPyV viral load by Q-PCR assay in these patients varied from 1350 to 20,000,000 (1.35 × 10(3) to 2 × 10(7) ) copies/mL for urine samples and 935 to 18,920 (9.35 × 10(2) to 1.89 × 10(4) ) copies/mL for blood samples. All the 11 patients were positive for decoy cells but only 3 developed PVN based on histology and positive SV40 staining. BKPyV infection was more prevalent in older patients. All patients responded to reduction in their immunosuppressive regimens, apart from 2 patients who required replacement of calcineurin inhibitors-based regimen with mammalian target of ramapycin inhibitors with an overall good response. CONCLUSION: Protocol screening programs based on detection of viral replication by viruria, viremia, and decoy cells in urine are necessary to shed light on patients with high virus replication and hence increased risk of developing PVN, and to allow early diagnosis and intervention.

In kidney transplant recipients with BK polyomavirus infection, early BK nephropathy, microvascular inflammation, and serum creatinine are risk factors for graft loss.

BACKGROUND: Little information is available on the risk factors for graft loss in kidney transplant recipients with BK polyomavirus (BKPyV) nephropathy (BKVN) in the presence or absence of antibody-mediated rejection (AMR). METHODS: We examined the risk factors for graft loss in consecutive kidney allograft recipients with biopsy-confirmed BKVN, with or without concomitant AMR. RESULTS: A total of 1904 kidney transplants were performed at our institution during 2005-2011. Of these, 330 (17.33%) were diagnosed with BKPyV viremia, and 69 were diagnosed with BKVN (3.6%). Eleven patients had a concomitant diagnosis of AMR. Patients with AMR were characterized by significantly higher peak panel-reactive antibody, retransplant rates, and desensitization preconditioning at the time of transplantation, as well as microvascular inflammation (MVI = glomerulitis + peritubular capillaritis), C4d score, and donor-specific antibody at the time of diagnosis (P ≤ 0.01). Treatment with plasma exchange, intravenous immunoglobulin, and cidofovir was more prevalent in this group (P ≤ 0.02). Univariate analyses assessing the risk factors for graft loss in all patients with BKVN, identified an independent association of African-American race, deceased-donor transplantation, serum creatinine (Scr), MVI, and early disease (BKVN within 6 months of transplant) with poor outcomes. Multivariate analyses retained only 3 variables: Scr >2 mg/dL (hazard ratio [HR] = 4.3, 95% confidence interval [CI] 1.9-9.7, P = 0.0004), early BKVN (HR = 2.7, 95% CI 1.3-5.3, P = 0.004), and MVI (HR = 1.8, 95% CI 1.2-2.8, P = 0.008). CONCLUSIONS: These observations suggest that, in patients with BK infection, early BKVN, Scr >2, and MVI are predictors of poor outcomes. Further studies are needed to determine effective treatment strategies for BKVN, with or without AMR.

Banff 2013 update: Pearls and pitfalls in transplant renal pathology.

The pathological classification of rejection in renal allografts (Banff classification) has undergone substantial evolution for more than 20 years, and has been the diagnostic gold standard in clinical practice. The 2013 updated Banff classification encompasses a revised scheme of antibody-mediated rejection (ABMR) that consists of donor-specific antibody (DSA) positivity, characteristic histological manifestations for both acute and chronic ABMR, and DSA-induced endothelial cell injury which is represented by either C4d positivity, microvascular inflammation or expression of activated endothelial gene transcripts. Other modified criteria include a C4d positivity threshold, and histological definition of transplant glomerulitis and transplant glomerulopathy. Morphologically, glomerulonephritis, either recurrent or de novo, can be challenging to differentiate from ABMR-mediated transplant glomerulitis. Endothelial arteritis by itself does not warrant the diagnosis of acute T-cell mediated rejection; ABMR should also be considered based on the DSA test results. With regard to polyomavirus BK-associated nephropathy, immunohistochemical examination using anti-simian virus (SV) 40 antibody can be a promising method to assess the quantitative viral load of polyomavirus BK and graft survival. In summary, the 2013 updated Banff classification strictly defines ABMR with histopathological and serological criteria irrespective of C4d positivity. Inclusion of gene expression data relevant to ABMR highlights that the Banff criteria have entered the era of 'Seeing the Unseen' schemes, reflecting recent advances in understanding the molecular events in allograft injury.

BK virus encoded microRNAs are present in blood of renal transplant recipients with BK viral nephropathy.

BK viral infection is an important cause of renal transplant dysfunction and failure. Current strategies utilize surveillance for infection with DNA polymerase chain reaction assays and modulation of immunosuppression. Many viruses including polyomaviruses encode microRNAs (miRNAs). We have detected BK virus (BKV) encoded miRNAs in the blood of infected renal transplant recipients, and see a strong correlation between BKV encoded miRNA and BKV DNA in blood and a relationship between levels of bkv-miR-B1-5p and the presence of biopsy-proven BK viral nephropathy. Further research is needed to determine whether the detection of this and other virally encoded miRNAs may be useful in the diagnosis of active viral replication.

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.

Characterization of urinary CD4⁺ and CD8⁺ T cells in kidney transplantation patients with polyomavirus BK infection and allograft rejection.

BACKGROUND AND OBJECTIVES: The objective of this study was to characterize CD4(+) and CD8(+) T-cell populations in blood and urine of renal transplant patients with BK virus (BKV) infection or allograft rejection. MATERIALS AND METHODS: Percentages and absolute numbers of CD4(+) and CD8(+) effector memory T-cell subtype (TEM ) and terminal differentiated T cells (TTD ) in renal transplant patients with BKV infection (n = 14), with an episode of allograft rejection (n = 9), and in uncomplicated renal transplant patients with a stable kidney function (n = 12) were measured and compared using 4-color fluorescence-activated cell sorting. Results were correlated with the number of CD4(+) and CD8(+) T cells in renal biopsies. RESULTS: In patients with allograft rejection, the number of urinary CD4(+) TEM and CD8(+) TEM cells was significantly increased compared to patients with BKV infection or patients without complications. Positive correlation was found between the number of CD4(+) and CD8(+) cells in the renal biopsies and the number of CD4(+) and CD8(+) cells in urine. In patients with rejection, after 2 months of immunosuppressive therapy, a reduction in urinary CD8(+) TEM cells was found. CONCLUSIONS: CD4(+) TEM and CD8(+) TEM cells in urine could be a marker to distinguish allograft rejection from BKV-associated nephropathy and to monitor therapy effectiveness in renal transplant patients with allograft rejection.

Development and validation of a quantitative real time PCR assay for BK virus.

Several studies have shown that BK viral load in plasma and urine are reliable markers for the detection of BK virus associated nephropathy (BKVAN) in renal transplant patients. We developed a quantitative real time PCR assay based on TaqMan technology for the measurement of BK viral load in plasma and urine. Considering the high similarity of the nucleotide sequence of the BK virus (BKV) with the JC virus (JCV), we designed this assay to specifically amplify BKV. We determined the viral DNA recovery rate on manual (QIAGEN's QIAamp DNA Blood Mini Kit) and automated (BioMerieux's NucliSENS EasyMAG) extraction methods. The comparison showed a higher viral DNA recovery rate on the automated extraction (61-76% in plasma and 52-65% in urine) as compared to the manual method (49-52% in plasma and 33-56% in urine). Quantitation of the viral load was performed using an external standard curve that was constructed with serial dilution of a plasmid containing the full length of the BKV genome. Commercially available quantitative BKV standards showed good correlation with the plasmid standard. The reproducibility of the assay was determined based on the Ct values of the amplified products as well as in BK copies per milliliter of sample. This assay is linear over a 7 log range (10 to 1 × 10(7) copies per reaction), no cross-reactivity was detected with the closest-related polyomavirus JCV, as well as other viruses that may be found in immunocompromised patients, and human genomic DNA. The limit of detection of the assay is 300 copies per milliliter in both plasma and urine and the limit of quantitation is 1000 copies per milliliter using the NATtrol BK Virus Linearity Panel (ZeptoMetrix). This real time PCR assay provides a reliable and sensitive method for the quantitation of BKV in plasma and urine samples.

Native BK Polyomavirus Nephropathy in an Orthotopic Heart Transplant Patient.

BK polyomavirus nephropathy (BKVN) is a common cause of nephropathy in kidney transplant patients and is typically seen within the first year after transplantation. BK polyomavirus nephropathy can occur in the native kidneys of patients with nonrenal solid-organ transplants (NRSOT). However, this is rare, especially outside the early post-transplant period, and BKVN is not usually considered in the differential diagnosis for acute kidney injury in NRSOT patients. We present a case of a 75-year-old man who had undergone orthotopic heart transplant 13 years prior with stable allograft function who developed progressive renal dysfunction in the setting of recent unilateral obstructive nephrolithiasis requiring ureteral stenting. Kidney biopsy demonstrated evidence of polyomavirus nephritis. Serum BK viral load was elevated. Despite reducing immunosuppression and initiating leflunomide, viral clearance was never achieved. The patient experienced progressive failure to thrive before ultimately transitioning to hospice care and dying. The intensity of immunosuppression is a well-known risk factor for viral replication; ureteral stenting has also been associated with BKVN. However, since clinical manifestations of BK viral infections often include a genitourinary (GU) tract pathology, it is important for clinicians to consider BKVN in patients with NRSOT with progressive renal dysfunction, especially in the clinical context of known GU disease.