BK virus infection following kidney transplantation: an overview of risk factors, screening strategies, and therapeutic interventions

High-Dose Intravenous Immunoglobulin to Treat Anti-Thymocyte Globulin Induction-Related BK Virus and Cytomegalovirus Infection in Patients with ABO-Incompatible Kidney Transplantation

BACKGROUND

ABO-incompatible (ABOi) transplantation is a novel method transplantation method that carries a heightened risk of infection caused by the use of high immunosuppressant doses. This elevated risk is particularly concerning for viral infections, such as cytomegalovirus (CMV) and the BK virus (BKV) increases. Herein, we present a case where high-dose intravenous immunoglobulin (IVIG) was effective in treating viral infections after transplantation.

METHODS

A 41-year-old man underwent an ABOi transplantation. The initial isoagglutinin titer was 1:32. The patient received 200 mg of rituximab, and 3 rounds of plasmapheresis were performed. Subsequently, renal function remained normal; however, 7 months later, the renal function declined, and BK nephropathy and CMV infection were diagnosed through biopsy and serologic tests. The FK level was reduced, and mycophenolate mofetil was discontinued. Although ciprofloxacin and leflunomide were administered, their effects were minimal. Therefore, high-dose IVIG (1 g/kg) was administered 5 times over 5 weeks, which led to a reduction in BK viral load and CMV infectivity in the serum.

CONCLUSIONS

High-dose IVIG may serve as a promising alternative treatment to mitigate early transplant rejection and BKV and CMV infections.

Role of therapeutic plasma exchange as a desensitization therapy in human leukocyte antigen incompatible renal transplant patients: A single-center experience

OBJECTIVE

Despite an increase in the rate of successful live donor renal transplantation done annually, the number of potential recipients with acceptable donors is relegated to the ever-expanding cadaver-donor waiting list due to sensitization to human leukocyte antigen (HLA) antibodies. If not sufficiently suppressed, these preformed HLA antibodies can trigger antimicrobial resistance (AMR) and early graft loss. To ameliorate this situation, various desensitization treatments are administered to provide a survival benefit to highly sensitized patients.

METHOD

One hundred and six patients in the time frame of January 2017 to March 2019 were included in the study group. The desensitization protocol included therapeutic plasma exchange and administration of low-dose intravenous immunoglobulin (100 mg/kg per therapeutic plasma exchange (TPE) session) to highly sensitized patients (treatment group) who subsequently underwent renal transplantation after negative pre-transplant Centers for Disease Control and Prevention Luminex crossmatch (CDC/LumXM). We compared graft survival rates between the group undergoing desensitization (treatment group) and matched control group of patients that underwent HLA-compatible transplantation.

RESULTS

In the treatment group, Kaplan-Meier analysis estimates an average rate of patient graft survival of 95.2% at 3 years post-transplant, as compared with the rate of 86.9% in the same time frame for the control-matched group (p < 0.05 for both comparisons).

CONCLUSION

Desensitization treatment with TPE before live donor renal transplantation in the case of patients with HLA sensitization provides better survival benefits along with monitoring for donor-specific antibodies (DSAs) and other infections, rather than waiting for a compatible organ donor. The data lays out evidence that desensitization treatments can assist overcome HLA incompatibility barriers in live donor renal transplantation.

Comparison of BK virus nephropathy risk between double-J-stent with anti-reflux mechanism and standart double-J-stent: single-center experience

Aim: Ureteral stend use is a risk factor for BK nephropathy (BKVN). In 2015, we compared the patients with anti-reflux mechanism DJS (ARD-DJS) and those used standard DJS (st-DJS) in terms of BKV and BKVN frequency in 90 kidney transplant patients in two centers. With the increase in the number of our patients over time and lengthening of the follow-up duration, we needed to re-evaluate the data in one center. Material and Method: We retrospectively evaluated 211 patients who underwent kidney transplantation at Gazi Yaşargil Training and Research Hospital between September 2012 and September 2019. The following parameters were recorded, demographic data, immunosuppression protocols, presence of rejection, graft loss, plasma BKV levels, and presence of BKVN. Median and IQR follow-up time for ARD-DJS and St-DJS patients was 72 months (62,5-80,3 months) and 27,8 months (17,4-39,6 months) respectively. Results: Thirteen patients (6,1%) had BKV viremia. BKVN was revealed by kidney biopsy in 3 of 13 patients. However, graft loss due to BKVN was observed in only one patient. ARD-DJS was used in 4 of these cases and standard DJS was used in 9 of these cases. Patients in whom BKV revealed in the first 3 months were compared in the aspect of DJS technique, BKV was significantly less observed in the ARD-DJS group (ARD-DJS: 2 patients; St-DJS:9 patients), (p=0,046). Conclusion: In our study, BKV was observed less in patients with ARD-DJS that were clinically significant but not statistically significant. Therefore, prospective randomized studies with high patient numbers are needed to determine the effectiveness of ARD-DJS.

The impact of pre-graft serology on the risk of BKPyV infection post-renal transplantation

OBJECTIVES

BK polyomavirus associated nephropathy, is a troublesome disease induced by BK polyomavirus (BKPyV) infection in immunocompromised renal graft recipients with no effective available treatment, making immunosuppression reduction the only management option. Thus, pre-graft predictive BKPyV replication markers are needed for high-risk viremia patient identification.

METHODS

we conducted a retrospective study to assess the correlation between the BKPyV pre-transplant serostatus and post-transplant BKPyV infection incidence. Sera from 329 recipients and 222 matched donors were tested for anti-BKV antibodies against BKPyV serotypes I and IV by a VLPs-based IgG ELISA, and BKPyV DNA load was monitored for at least 1 year post transplantation.

RESULTS

80 recipients were viruric and 59 recipients were viremic post transplantation. In the post-transplant period, the probability of developing viremia for serotype I was increasing from 4.3% for the D-/R + group to 12.1% for the D+/R + group and climbing to 37.5% for the D+/R- group (p < 0.05). When calculating the recipient mean titers for serotypes I and IV, we observed a clear difference in the proportions of viremia passing from 50% for mean titers < 400 to 13.5% for titers ≥ 400 (p < 0.001) with also a higher proportion of presumptive nephropathy (50% vs 23.1%, p < 0.05). In univariate analysis this parameter has an odds ratio of 6.41 for the risk of developing post-transplant BKPyV viremia (95% CI: 3.16-13.07; p < 0.0001).

CONCLUSIONS

Both donor and recipient BKPyV seropositivity determination before transplantation and antibody titer may serve as a predictive tool to manage clinical BKPyV infection by identification of patients at high risk.

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.

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.

Resolution of a High Grade and Metastatic BK Polyomavirus-Associated Urothelial Cell Carcinoma Following Radical Allograft Nephroureterectomy and Immune Checkpoint Treatment: A Case Report

BACKGROUND

BK viral infection in the posttransplant setting continues to cause serious morbidity with effects ranging from allograft nephropathy and dysfunction to urothelial malignancy.

RESULTS

In this report, we present a patient that developed BK-associated nephropathy and, 6 years later, locally advanced urothelial malignancy in the renal allograft with nodal, muscle, and extremity involvement. Following radical allograft nephroureterectomy, he was treated with palliative radiation and the immune checkpoint inhibitor atezolizumab. Follow-up imaging at 1 year demonstrated radiographic complete response.

CONCLUSIONS

This report supports the growing body of evidence supporting the association of urothelial malignancy and BK virus infection in renal transplant recipients. Further, it highlights the novel application of immune checkpoint inhibitors in the treatment of advanced posttransplant malignancy, in particular when the allograft is removed and the tumor is possibly of donor origin.

Impact of Pretransplant Donor BK Viruria in Kidney Transplant Recipients

BACKGROUND

BK virus (BKV) is a significant cause of nephropathy in kidney transplantation. The goal of this study was to characterize the course and source of BKV in kidney transplant recipients.

METHODS

We prospectively collected pretransplant plasma and urine samples from living and deceased kidney donors and performed BKV polymerase chain reaction (PCR) and immunoglobulin G (IgG) testing on pretransplant and serially collected posttransplant samples in kidney transplant recipients.

RESULTS

Among deceased donors, 8.1% (17/208) had detectable BKV DNA in urine prior to organ procurement. BK viruria was observed in 15.4% (6/39) of living donors and 8.5% (4/47) of deceased donors of recipients at our institution (P = .50). BKV VP1 sequencing revealed identical virus between donor-recipient pairs to suggest donor transmission of virus. Recipients of BK viruric donors were more likely to develop BK viruria (66.6% vs 7.8%; P < .001) and viremia (66.6% vs 8.9%; P < .001) with a shorter time to onset (log-rank test, P < .001). Though donor BKV IgG titers were higher in recipients who developed BK viremia, pretransplant donor, recipient, and combined donor/recipient serology status was not associated with BK viremia (P = .31, P = .75, and P = .51, respectively).

CONCLUSIONS

Donor BK viruria is associated with early BK viruria and viremia in kidney transplant recipients. BKV PCR testing of donor urine may be useful in identifying recipients at risk for BKV complications.

The immunophenotyping of different stages of BK virus allograft nephropathy

Objectives: To investigate the immunohistochemical features of different stages of BK virus allograft nephropathy (BKVN) and further elucidate the underlying immunological mechanism involved in the evolution of BKVN. Methods: Fifty-two renal transplant recipients with biopsy proven BKVN were retrospectively selected. According to the third edition of the American Society of Transplantation Infection guidelines, 10 patients were categorized as having mild BKVN (stage A), 25 were moderate (stage B) and 17 were severe (stage C). The differential infiltrations of CD3+ (T lymphocytes), CD4+ (helper T lymphocytes), CD8+ (cytotoxic T lymphocytes), CD20+ (B lymphocytes), CD68+ (macrophages) and CD138+ (plasma cells) cells and the expression of interleukin-2 receptor (IL-2R) and human leukocyte antigen DR (HLA-DR) were compared among the three groups. Results: CD3+, CD4+, CD8+, CD20+, CD138+ and CD68+ cells infiltrations, IL-2R and HLA-DR expression were positive in the BKVN patients. Moreover, with increasing stages of BKVN, the numbers of positively stained inflammatory cells and the expression of IL-2R were significantly increased in the severe group compared to the mild group, whereas no statistically significant differences were observed with regard to HLA-DR expression. Eosinophil and neutrophil infiltration could also be observed in moderate to advanced BKVN. Conclusion: Renal allograft damage caused by BKVN involved T lymphocyte-, B lymphocyte- and mononuclear macrophage-mediated immune responses. Inflammatory cell infiltrations in the renal allograft were probably the driving force for BKVN progression. Additionally, eosinophils and neutrophils may be involved in the pathophysiological mechanism of BKVN.

Predictive Value of the Combination of Peripheral Blood Lymphocyte Count and Urinary Cytology in BK Polyomavirus-associated Nephropathy

BACKGROUND

Graft biopsy is the gold standard for diagnosis of BK polyomavirus-associated nephropathy (BKPyVAN), and polymerase chain reaction is the most specific screening technique. Development of a noninvasive, cost-effective marker for BKPyVAN is important.

METHODS

We reviewed 492 adult kidney transplant patients. We investigated peripheral blood lymphocyte (PBL) count and urinary cytology at graft biopsy in patients with BKVPyAN (n = 21), acute T-cell-mediated rejection (n = 79), and no evidence of acute rejection (n = 149). We performed univariate and multivariate logistic regression and receiver operating characteristics analyses to compare the test performance of PBL count, urinary cytology, and their combination for diagnosis of BKPyVAN.

RESULTS

The PBL count at biopsy was significantly lower in the BKPyVAN group than the acute T-cell-mediated rejection and no acute rejection groups (959 ± 290/μL, 1433 ± 673/μL, and 1531 ± 549/μL, respectively; P < .01). The PBL count was 959 ± 290/μL at diagnosis of BKPyVAN and increased to 1123 ± 377/μL, 1238 ± 419/μL, and 1292 ± 491/μL at 1, 2, and 3 months after treatment, respectively (P < .05). On univariate analysis, the area under the curve was significantly higher for the combined model than for PBL and cytology alone (0.930, 0.797, and 0.875, respectively; P < .01). The improved test performance in the combined model remained significant after multivariate adjustment (0.972, 0.844, and 0.928, respectively; P < .01).

CONCLUSIONS

Decreased PBL count was found in BKPyVAN, and the predictive performance of the combination of PBL count and urinary cytology was significantly enhanced for diagnosis of BKPyVAN.

Conversion From Mycophenolates to Mizoribine Is Associated With Lower BK Virus Load in Kidney Transplant Recipients: A Prospective Study

BACKGROUND

BK virus allograft nephropathy (BKVAN) is a graft-threatening complication after kidney transplantation. Current consensus regarding the prevention of BKVAN is to screen for BK viremia and to treat sustained BK viremia through reducing immunosuppression. This study assessed the effect of conversion from mycophenolates to mizoribine (MZR) on the prevention of BK viremia in kidney transplant recipients.

METHODS

De novo kidney transplant recipients were screened for BK viruria. Sustained high levels of BK viruria (>10⁷ copies/mL) were treated by switching from mycophenolates to MZR. The reduction and clearance of BK viruria and viremia were evaluated.

RESULTS

Fifty kidney transplant recipients with high levels BK viruria were enrolled, including 11 recipients with BK viremia. After 6 months of MZR therapy, only 3 recipients still had high levels of BK viruria. The clearance rate of BK viremia was 100%. One episode of acute rejection occurred (2.0%) and was reversed by steroid administration. The serum uric acid level of the recipients was similar before and after switching to MZR, but the proportion of recipients receiving uric acid-reducing drugs increased significantly after 3 months of MZR therapy (19/50 vs 31/50; P = .02). No new cases of BK viremia were observed after conversion to MZR.

CONCLUSION

Conversion from mycophenolates to MZR in kidney transplant recipients with sustained high levels of BK viruria was associated with reduction of BK viruria and clearance of BK viremia. This may be an effective approach to prevent BK viremia and BKVAN.

CD4+ T Cell Immune Response to VP1 and VP3 in BK Virus Infected Recipients of Renal Transplantation

OBJECTIVE

To investigate the characteristics of BK virus (BKV) specific cellular immune response in the recipients who have early infection with BKV after renal transplantation.

METHODS

The recipients of renal allografts (n = 30) were divided into groups of BK virus nephropathy (BKVN), viruria, and viremia. The BKV load was observed with real-time fluorescence quantitative polymerase chain reaction in urine and blood every three months. The values of serum creatinine (SCr) were detected. The peripheral blood mononuclear cells (PBMCs) were cultivated with overlapping peptide pool containing BKV structural proteins VP1, VP2, and VP3, and regulatory proteins large tumor antigen (LT-Ag) and small tumor antigen (st-Ag), to stimulate in vitro specific cellular immunoresponse. Flow cytometry was used to measure the proliferation of CD3+/CD4+/CD8+ T and interferon [INF]-γ/interleukin [IL]-2/tumor necrosis factor [TNF]-α T cell subsets.

RESULTS

The BKV infection increased SCr values in recipients of renal transplantation. CD4+ T cells were dominant (>90%) in the in vitro cellular immunoresponse to VP1, VP2, VP3, LT-Ag, and st-Ag. At the presence of viremia and BKVN, IL-2/IFN-γ+/TNF-α+ CD4+ T cells showed significantly decreased in vitro cellular immunoresponse to VP1, VP2, and VP3 (p < 0.05), but insignificantly changed to LT-Ag and st-Ag (p > 0.05). For the cases of viruria and viremia, IL-2/IFN-γ+/TNF-α+ CD4+ T cells showed significantly higher in vitro cellular immunoresponse to VP1, VP2, and VP3 than to LT-Ag and st-Ag (p < 0.05). The immunogenicity of VP1 and VP3 was significantly higher than that of VP2 (p < 0.05).

CONCLUSIONS

The BKV infection increases SCr values, and CD4+ T cells are dominant in the in vitro BKV specific cellular immunoresponse in the recipients of renal transplantation. Viremia significantly decreased the immunoresponse to VP1, VP2, and VP3. There is the significantly stronger immunoresponse to VP1 and VP3 when compared with that to VP2, LT-Ag, and st-Ag, suggesting that VP1 and VP3 may be the major targets for the BKV specific immune response.

Risk factors for BK virus viremia and nephropathy after kidney transplantation: A systematic review

In the last 20 years, the management of BK polyomavirus (BKPyV) reactivation in kidney transplant patients has become a true challenge for the transplant community. The only treatment option is based on the early identification of at-risk patients. The number of reported risk factors for BKPyV reactivation has increased markedly in the literature last years, although they are sometimes in an unclear or contradictory manner. Our purpose is to provide a systematic review and meta-analysis of risk factors for BKPyV viremia and nephropathy described in multivariate analyses. The PubMed database was searched for prospective or prospectively-based observational studies on risk factors for BKPyV viremia and/or nephropathy. Our qualitative assessment of risk factors was based on the odds ratios and hazard ratios calculated in multivariate regression analyses. Of the 241 publications screened, 34 were included in the qualitative analysis. In all, 144 and 19 distinct factors were analyzed for BKPyV viremia and for BKPyV nephropathy, respectively. Our evaluation highlighted eight risk factors for BKPyV viremia: a tacrolimus regimen, a deceased donor, a male recipient, a history of previous transplant, age at transplantation, ureteral stent use, delayed graft function, and acute rejection episodes increased the risk of BKV viremia to varying extents. Tacrolimus and acute rejection episodes were also associated with a higher incidence of BKPyV nephropathy. BKPyV reactivation is a serious complication after renal transplantation. With a view to combating this problem, existing data should be published in full, and new prospective international multicenter studies should be performed.

Impact of immune suppressive agents on the BK-Polyomavirus non coding control region

BACKGROUND

Reactivation of the BK-Polyomavirus (BKPyV) can cause a polyomavirus associated nephropathy in approx. 10% of kidney transplant recipients. In these cases, current therapy is based on the reduction of immunosuppression. Since BKPyV-transcription is driven by the Non-Coding-Control-Region (NCCR) we were interested whether NCCR-activity is affected by immunosuppressive agents.

METHODS

Plasma samples from 45 BKPyV-positive patients after renal transplantation were subjected to PCR-analysis. NCCR-amplicons were cloned into a plasmid that allows the quantification of early and late NCCR-activity by tdTomato and eGFP expression, respectively. HEK293T-cells were transfected with the reporter-plasmids, treated with immunosuppressive agents, and subjected to FACS-analysis. In addition, H727-cells were infected with patient derived BKPyV, treated with mTOR-inhibitors, and NCCR activity was analysed using qRT-PCR.

RESULTS

While tacrolimus and cyclosporine-A did not affect NCCR-promoter-activity, treatment with mTOR1-inhibitor rapamycin resulted in the reduction of early, but not late-NCCR-promoter-activity. Treatment with dual mTOR1/2 inhibitors (INK128 or pp242) led to significant inhibition of early, however, concomitantly enhanced late-promoter-activity. In BKPyV infected cells both rapamycin and INK128 reduced early expression, however, INK128 resulted in higher late-mRNA levels when compared to rapamycin treatment.

CONCLUSIONS

Our results demonstrate that mTOR1-inhibitors are able to reduce early-expression of wildtype and rearranged NCCRs, which might contribute to previously described inhibition of BKPyV-replication. Dual mTOR1/2-inhibitors, however, additionally might shift viral early into late-expression promoting synthesis of viral structural proteins and particle production.

Determination of viremia cut-off for risk to develop BKPyV-associated nephropathy among kidney transplant recipients

BACKGROUND

BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) is a consequence of BKPyV replication in the urinary tract in kidney transplant recipients (KTR).

OBJECTIVES

The objectives were to determine the prevalence of BKPyV replication and BKPyVAN, risk factors associated to sustained viremia and BKPyVAN, and viremia cut-off that best predict the occurrence of sustained viremia and nephropathy in KTR of a single University Hospital Kidney Transplant Center.

PATIENTS AND METHODS

All KTR undergoing transplantation from August 2010 to December 2011 were enrolled and monitored up to 2 years posttransplantation for BKPyV viruria by decoy cells shedding or polymerase chain reaction (PCR) and viremia by PCR. Kidney biopsy was indicated if sustained viremia (two or more viremia above 10 000 copies/mL) to confirm BKPyVAN diagnosis.

RESULTS

In this study, 326 transplants were performed and 246 patients were included. Prevalence of viruria was 36.9%, viremia 22.3% and nephropathy 3.2%. Male gender was the only risk factor associated to sustained viremia or nephropathy. Cut-off value of viremia that best discriminates the progression to sustained viremia and to BKPyVAN was 37 488 and 44 956 copies/mL, respectively.

CONCLUSIONS

Prevalence of viruria, viremia, and nephropathy were similar to those reported in literature but the cut-off value of viremia that best discriminates the risk of progression to nephropathy was greater than the value usually reported, which is 10 000 copies/mL.

Kidney transplant recipients with polycystic kidney disease have a lower risk of post-transplant BK infection than those with end-stage renal disease due to other causes

BACKGROUND

Polyomavirus-associated nephropathy is associated with high risk of kidney allograft loss. Whether the cause of native end-stage renal disease influences the risk of BK infection is unclear.

METHODS

A retrospective, single-center study of 2741 adult kidney transplant recipients between 1994 and 2014 was performed. Recipients had end-stage renal disease due to polycystic kidney disease (PKD, n = 549), diabetes mellitus (DM, n = 947), hypertension (HTN, n = 442), or glomerulonephritis (GN, n = 803).

RESULTS

A total of 327 recipients (12%) developed post-transplant BK viremia over a median follow-up time of 5 years. The incidence rate of BK viremia was lowest in patients with PKD (1.46 per 100 person-years) compared to other causes of ESRD (DM = 2.06, HTN = 2.65, and GN = 2.01 per 100 person-years). A diagnosis of PKD was associated with a lower risk of post-transplant BK viremia (adjusted HR (95% CI) = 0.67 (0.48-0.95), P = 0.02). BK nephropathy was significantly less common in patients with PKD (0.21 per 100 person-years) compared to those with HTN (0.80 per 100 person-years, P ≤ 0.001). Among patients with PKD, the risk of BK viremia was lower in patients with nephrectomy, compared to those without nephrectomy (adjusted HR (95% CI) = 0.42 (0.19-0.92), P < 0.05).

CONCLUSION

ESRD due to PKD is associated with a lower risk of post-transplant BK infection. The renal tubular epithelial cells in PKD are unique; they are in a proliferative but non-differentiated state. Whether this characteristic of renal tubular epithelial cells alters the BK viral reservoir or replication in PKD patients warrants further study.

Risk factors for BK virus infection in living-donor renal transplant recipients: a single-center study from China

Objectives: BK virus (BKV) infection has become one of the main complications in renal transplant recipients (RTRs) with the arrival of newer potent immunosuppressive agents. However, reports on the epidemiology of BKV infection and risk factors in Chinese population after renal transplantation are scarce.

Methods: From June 2015 to July 2016, living-donor renal transplant recipients (LDRTRs) who routinely received the quantitative BKV DNA testing of urine and plasma samples using quantitative real-time polymerase chain reaction (PCR) for the first time after transplantation were selected, while dialysis patients and healthy living donors during that period served as controls. Potential variables were compared and analyzed using logistic regression model multivariate analysis to assess the BKV infection related factors in LDRTRs.

Results: Among the 52 LDRTRs identified, BKV DNA was detected in 16 urine samples (30.8%), significantly higher than that of dialysis patients (6.3%) and healthy living donors (4.2%) (p < .001). Nevertheless, no statistically significant difference wax noted between the latter two groups in urine samples (p = .842). Meanwhile, BKV DNA detection in blood samples was all negative in the three groups. Univariate analysis shown tacrolimus (Tac) trough level and lymphocyte percentage were associated with BKV infection in LDRTRs. Multivariate regression analysis also showed Tac trough level (HR, 1.644; p = .03), lymphocyte percentage (HR, 0.878; p = .026) were associated with BKV infection in LDRTRs.

Conclusions: In Chinese population, the incidence of BKV infection increased significantly after living-donor renal transplantation. Significantly increased Tac trough level and decreased lymphocyte percentage might be the risk factors for BKV infection in LDRTRs.

BK Virus-Associated Nephropathy: Current Situation in a Resource-Limited Country

BACKGROUND

Data on BK virus-associated nephropathy (BKVAN) and treatment strategy in a resource-limited country are scarce. This study aimed to evaluate epidemiology of BKVAN and its situation in Thailand.

METHODS

A retrospective analysis was conducted among adult kidney transplant recipients at Ramathibodi Hospital from October 2011 to September 2016. Patients' demographic data, information on kidney transplantation, immunosuppressive therapy, cytomegalovirus and BK virus infections, and allograft outcomes were retrieved and analyzed.

RESULTS

This study included 623 kidney transplant recipients. Only 327 patients (52.49%) received BK virus infection screening, and 176 of 327 patients had allograft dysfunction as a trigger for screening. BKVAN was identified in 39 of 327 patients (11.93%). Deceased donor transplantation and cytomegalovirus infection were associated with a higher risk of BKVAN (odds ratio = 2.2, P = .024, 95% confidence intervals [1.1, 4.43], and odds ratio = 2.6, P = .006, 95% confidence intervals [1.29, 5.26], respectively). BKVAN patients were at significantly higher risk for allograft rejection (P < .001) and allograft failure (P = .036). At the end of the study, 4 graft losses were documented (12.12%).

CONCLUSIONS

BKVAN was associated with high rate of allograft rejection and failure. However, surveillance of its complications has been underperformed at our facility. Implementing a formal practice guideline may improve allograft outcome in resource-limited countries.

BK Polyomavirus Immune Response With Stress on BK-Specific T Cells

Polyomavirus-associated nephropathy is a pertinent cause of poor renal allograft survival. Absence of defensive immunity toward BK polyomavirus may favor the occurrence of BK polyomavirus-active infection and influence the progression to polyomavirus-associated nephropathy. Humoral immune responses may offer incomplete protection. In this review, available data on both humoral and cellular immunity were examined, with a concentration on BK polyomavirus-specific T cells; in addition, their roles in BK polyomavirus cellular immune response and immunotherapy were discussed. This traditional narrative review used PubMed and Medline searches for English language reports on BK polyomavirus immune response and BK-specific T cells published between January 1990 and November 2017. The search included the key words BK virus, BK polyomavirus, immune and response, and specific T cells. Monitoring BK polyomavirus-specific T cells has both therapeutic and prognostic value. Innovative cellular immunotherapy approaches, including development of vaccinations and infectious recombinant BK polyomavirus, could further contribute to the prevention of BK polyomavirus infection and related diseases.

p53 elevation in human cells halt SV40 infection by inhibiting T-ag expression

SV40 large T-antigen (T-ag) has been known for decades to inactivate the tumor suppressor p53 by sequestration and additional mechanisms. Our present study revealed that the struggle between p53 and T-ag begins very early in the infection cycle. We found that p53 is activated early after SV40 infection and defends the host against the infection. Using live cell imaging and single cell analyses we found that p53 dynamics are variable among individual cells, with only a subset of cells activating p53 immediately after SV40 infection. This cell-to-cell variabilty had clear consequences on the outcome of the infection. None of the cells with elevated p53 at the beginning of the infection proceeded to express T-ag, suggesting a p53-dependent decision between abortive and productive infection. In addition, we show that artificial elevation of p53 levels prior to the infection reduces infection efficiency, supporting a role for p53 in defending against SV40. We further found that the p53-mediated host defense mechanism against SV40 is not facilitated by apoptosis nor via interferon-stimulated genes. Instead p53 binds to the viral DNA at the T-ag promoter region, prevents its transcriptional activation by Sp1, and halts the progress of the infection. These findings shed new light on the long studied struggle between SV40 T-ag and p53, as developed during virus-host coevolution. Our studies indicate that the fate of SV40 infection is determined as soon as the viral DNA enters the nucleus, before the onset of viral gene expression.

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.

Impact of low-level BK polyomavirus viremia on intermediate-term renal allograft function

BACKGROUND

BK polyomavirus (BKPyV)-associated nephropathy (PyVAN) is a significant cause of premature renal transplant failure. High-level BKPyV viremia is predictive for PyVAN; however, low-level BKPyV viremia does not necessarily exclude the presence of PyVAN. As data are limited regarding whether or not low-level BKPyV viremia has an effect on intermediate-term graft outcome, this study analyzes the impact of low-level BKPyV viremia on intermediate-term graft function and outcome compared with high-level viremia and non-viremic patients.

METHODS

All renal transplant patients received follow-up examinations at the Department of Nephrology, University Hospital Essen. Patients were screened for BKPyV viremia and stratified into three groups according to their maximum BKPyV load in serum (low-level viremia, high-level viremia, and no viremia).

RESULTS

In 142 of 213 (67%) patients, BKPyV was never detected in serum; 42 of 213 (20%) patients were found positive for low-level viremia (≤10⁴ copies/mL); and 29 of 213 (13%) patients showed high-level viremia (>10⁴ copies/mL). No significant differences regarding transplant function and graft failure were observed between patients without BKPyV viremia (delta estimated glomerular filtration rate [eGFR] +0.1 mL/min [month 1 vs last visit at month 44]) and patients with low-level BKPyV viremia (delta eGFR -1.7 mL/min). In patients with high-level viremia, transplant function was significantly restricted (delta eGFR -6.5 mL/min) compared with low-level viremia until the last visit at 44 ± 9.7 months after transplantation. Although the graft function and graft loss were worse in the high-level viremia group compared with no viremia (eGFR 37 vs 45 mL/min), the difference was not significant.

CONCLUSIONS

High-level viremia was associated with impaired graft function. In contrast, low-level BKPyV viremia had no significant impact on intermediate-term graft function.

BK virus replication in renal transplant recipients: Analysis of potential risk factors may contribute in reactivation

BACKGROUND

Considering the increasing problem of BK virus infection during post renal transplant surveillance, it is necessary to distinguish the main risk factors leading to reactivation of latent BK virus. Up to now, some probable risk factors have been investigated in some studies, but the results have been confusing and contradictory.

OBJECTIVES

The goal of the present study was to determine the frequency and potential risk factors that may play a role in BK polyomavirus reactivation and nephropathy.

STUDY DESIGN

In this cross-sectional study, 110 patients, who underwent consecutive transplantation between 2010 and 2013, were enrolled without preliminary screening. Urine and blood samples were taken, and quantitative Real-time PCR assay was used to detect and measure the viral load. Demographic and clinical characteristics of the patients who had BK viremia and/or viruria were documented.

RESULTS

Among 110 cases of renal transplant recipients, BK viruria and viremia were found in 54 (49%) and 22 people (20%) respectively. The pre-transplant durations of dialysis among patients with BK viruia were found longer in comparison to BK negative patients. Treatment with Tacrolimus (p=0.03) was found to be a risk factor for development of BK viruria. In patients with viruria and viremia the median creatinine levels were 1.45mg/dl and 1.35mg/dl respectively, which were higher than those in the patients with negative results for BK viruria (p=0.002) and viremia (p=0.02). Also, treatment with Cyclosporine could significantly increase the incidence of BK virus shedding in both urine and blood among patients who received it (p=0.01). Significant relation between reactivation of BK virus and other factors such as age, sex, acute rejection and diabetes was not found.

CONCLUSION

Based on our findings, the main potential risk factors for shedding of BK virus into urine in renal transplant recipients were prolonged pre-transplant dialysis and Tacrolimus regimen. Cyclosporine regimens could be considered as risk factor for both BK viruria and viremia. A significant correlation between BK virus replication and elevated creatinine level was seen among our patients.

Correlation of BK Virus Neutralizing Serostatus With the Incidence of BK Viremia in Kidney Transplant Recipients

BACKGROUND

BK virus (BKV)-associated nephropathy is the second leading cause of graft loss in kidney transplant recipients. Due to the high prevalence of persistent infection with BKV in the general population, it is possible that either the transplant recipient or donor may act as the source of virus resulting in viruria and viremia. Although several studies suggest a correlation between donor-recipient serostatus and the development of BK viremia, specific risk factors for BKV-related complications in the transplant setting remain to be established.

METHODS

We retrospectively determined the pretransplant BKV neutralizing serostatus of 116 donors (D)-recipient (R) pairs using infectious BKV neutralization assays with representatives from the 4 major viral serotypes. The neutralizing serostatus of donors and recipients was then correlated with the incidence of BK viremia during the first year posttransplantation.

RESULTS

There were no significant differences in baseline demographics or transplant data among the 4 neutralizing serostatus groups, with the exception of calculated panel-reactive antibody which was lowest in the D+/R- group. Recipients of kidneys from donors with significant serum neutralizing activity (D+) had elevated risk for BK viremia, regardless of recipient serostatus (D+ versus D-: odd ratio, 5.0; 95% confidence interval, 1.9-12.7]; P = 0.0008). Furthermore, donor-recipient pairs with D+/R- neutralizing serostatus had the greatest risk for BK viremia (odds ratio, 4.9; 95% confidence interval, 1.7-14.6; P = 0.004).

CONCLUSIONS

Donor neutralizing serostatus correlates significantly with incidence of posttransplant BK viremia. Determination of donor-recipient neutralizing serostatus may be useful in assessing the risk of BKV infection in kidney transplant recipients.

Polyomaviruses

Over the last 10 years, the number of identified polyomaviruses has grown to more than 35 subtypes, including 13 in humans. The polyomaviruses have similar genetic makeup, including genes that encode viral capsid proteins VP1, 2, and 3 and large and small T region proteins. The T proteins play a role in viral replication and have been implicated in viral chromosomal integration and possible dysregulation of growth factor genes. In humans, the Merkel cell polyomavirus has been shown to be highly associated with integration and the development of Merkel cell cancers. The first two human polyomaviruses discovered, BKPyV and JCPyV, are the causative agents for transplant-related kidney disease, BK commonly and JC rarely. JC has also been strongly associated with the development of progressive multifocal leukoencephalopathy (PML), a rare but serious infection in untreated HIV-1-infected individuals and in other immunosuppressed patients including those treated with monoclonal antibody therapies for autoimmune diseases systemic lupus erythematosus, rheumatoid arthritis, or multiple sclerosis. The trichodysplasia spinulosa-associated polyomavirus (TSAPyV) may be the causative agent of the rare skin disease trichodysplasia spinulosa. The remaining nine polyomaviruses have not been strongly associated with clinical disease to date. Antiviral therapies for these infections are under development. Antibodies specific for each of the 13 human polyomaviruses have been identified in a high percentage of normal individuals, indicating a high rate of exposure to each of the polyomaviruses in the human population. PCR methods are now available for detection of these viruses in a variety of clinical samples.

Incidence of BK polyomavirus infection after kidney transplantation is independent of type of immunosuppressive therapy

BACKGROUND

BK polyomavirus (BKV) infection and BKV nephropathy (BKVN) are risk factors for allograft function and survival.

METHODS

We retrospectively analyzed BK viremia and BKVN in 348 patients who received a kidney transplantation donated after brain death (n=232) or living donation (n=116) between 2008 and 2013. A total of 266 patients were treated with standard immunosuppression consisting of basiliximab induction, calcineurin inhibitor (CNI), and mycophenolic acid (MPA, n=219) or everolimus (n=47); 82 patients received more intense immunosuppression with lymphocyte depletion, CNI and MPA (n=38) or everolimus (n=44).

RESULTS

BK viremia occurred in 33 (9.5%) patients in the first year and in 7 (2.0%) recipients in the second year after transplantation. BKVN occurred in 4 (1.1%) patients in the first year. Donor and recipient age, diabetes, previous transplantation, and type of transplantation (donated after brain death vs living donation) were not risk factors (P>.05). BK incidence did not differ depending on induction or maintenance immunosuppression.

CONCLUSION

Incidence of BK viremia is independent of recipient characteristics, type of transplantation as well as induction and maintenance immunosuppression.

Clinically Relevant Reactivation of Polyomavirus BK (BKPyV) in HLA-A02-Positive Renal Transplant Recipients Is Associated with Impaired Effector-Memory Differentiation of BKPyV-Specific CD8+ T Cells

Polyomavirus BK (BKPyV) frequently reactivates in immunosuppressed renal transplant recipients (RTRs) and may lead to graft loss due to BKPyV-induced interstitial nephritis (BKVN). Little is known on the differentiation of CD8⁺ T cells targeting BKPyV in RTRs. Here we investigated whether BKPyV-specific CD8⁺ T cell differentiation differs in RTRs with varying degrees of BKPyV reactivation and/or BKVN.

Using combinatorial encoding with tetramers carrying BKPyV major capsid protein (VP1) and large T antigen protein (LTAG) epitopes, we investigated CD8⁺ T cell responses to BKPyV in longitudinally obtained PBMC samples from 46 HLA-A02-positive RTRs and 20 healthy adults. We were also able to isolate BKPyV-specific CD8⁺ T cells from five renal allografts, two of which were affected by BKVN.

Before transplantation, BKPyV-specific CD8⁺ T cells targeting VP1 and LTAG epitopes appeared predominantly as central-memory and CD27⁺/CD28⁺ effector-memory (T_EM), and naïve-like PD-1-expressing cells, respectively. After viral reactivation, BKPyV-specific CD8⁺ T cells assumed CD28⁻ T_EM and T_EMRA states in patients who were able to control BKPyV, whereas differentiation lagged behind in patients with severe viral reactivation or BKVN. Furthermore, VP1-specific CD69⁺/CD103⁺ tissue-resident memory (T_RM) cells accumulated in BKVN-affected allografts but lacked signs of effector differentiation. In contrast, granzyme B-expressing effector cells were detected in allografts not affected by BKVN.

In conclusion, effector-memory differentiation of BKPyV-specific CD8⁺ T cells in patients with high viral load or BKVN is impaired. Further characterization of the specific mechanisms behind this altered cellular differentiation is necessary to develop therapies that can prevent the emergence of BKVN.

In immunosuppressed renal transplant recipients (RTRs), BKPyV frequently reactivates from latency and may cause severe interstitial nephritis in the allograft (BKVN). Not only is there no effective treatment, it also not understood why BKVN arises in some RTRs but not in all. In the current study we investigated populations of CD8⁺ T cells targeting epitopes from structural and non-structural BKPyV proteins in RTRs over the course of transplantation. In contrast to RTRs who suffered from self-limiting reactivation of BKPyV, patients who developed severe viral reactivation and BKVN were found to have BKPyV-specific CD8⁺ T cells which did not, or less often differentiate into CD28⁻ effector-memory cells during viral reactivation. Moreover, virus-specific CD8⁺ T cell activation and differentiation was not only impaired in the circulation, but possibly also in BKVN-affected renal allografts. In contrast to the CD8⁺ T cells in kidneys from three patients who did not develop BKVN, T cells in two BKVN-affected kidneys did not display typical cytotoxic effector traits. These findings suggest that impaired BKPyV-specific CD8⁺ T cell maturation in response to viral reactivation, possibly owing to inter-individual differences in sensitivity to immunosuppressive medication or to certain viral quasispecies, underlies the emergence of severe viral reactivation and BKVN.

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.

BK Virus Nephropathy in Kidney Transplantation: An Approach Proposal and Update on Risk Factors, Diagnosis, and Treatment

BK virus belongs to Polyomaviridae family; it causes 95% of nephropathy cases related to polyomavirus, with the other 5% caused by JC virus. Nephropathy jeopardizes graft function, causing a premature failure of the graft in 1%-10% of patients with kidney transplants. Nowadays, antiviral effective treatment is unknown, which is why blood and urine screening of renal transplantation patients has become the most important recommendation to guide the decrease of immunosuppression, and the only proven method to decrease poor outcomes. Different interventions, such as cidofovir, leflunomide, fluoroquinolones, and intravenous immunoglobulin, have been attempted with no improvement at all. This review aims to summarize the most relevant features of BK virus, historical issues, transmission mechanisms, risk factors, and therapeutic interventions.

Evaluation of Infectious Complications in the First Year After Kidney Transplantation

Kidney transplantation (KT) is the best available therapy for patients with end-stage renal disease. Infectious complications are a common cause of morbidity and mortality. In this study, we evaluated the risk factors and outcomes of infectious complications in the first year after transplantation. This is a retrospective and observational study of kidney transplant recipients at Ankara University's Ibni Sina Hospital between January 2009 and August 2013. A total of 206 kidney transplant recipients were evaluated. In 129 patients, 298 infectious episodes occurred: 55 (26.7%) had 1; 33 (16%) 2; 19 (9.2%) 3; 7 (3.4%) 4; and 15 (7.3%) had 5 or more infectious episodes. The most common bacterial infection was urinary tract infection (128, 42.9%). Only 4 urinary tract infection episodes (3.1%) were associated with bacteriemia. Seventeen patients (5.7%) had bacteremia. Viral infections after transplantation were CMV infection (10.1%), BK virus infection (5.7%), and zona zoster (1.1%). Deceased donor kidney transplantation was the independent risk factor. Mean follow-up period was 66 months and was the same for the patients with and without infections. There was no significant difference in 5-year survival and creatinine levels at the last follow-up (logrank P = .409). Infections are the second most common cause of mortality in KT patients. The successful treatment of these complications and effective prophylaxis may decrease these complications.

Using Genetic Variation to Predict and Extend Long-term Kidney Transplant Function

Renal transplantation has transformed the life of patients with end-stage renal disease and other chronic kidney disorders by returning endogenous kidney function and enabling patients to cease dialysis. Several clinical indicators of graft outcome and long-term function have been established. Although rising creatinine levels and graft biopsy can be used to determine graft loss, identifying early predictors of graft function will not only improve our ability to predict long-term graft outcome but importantly provide a window of opportunity to therapeutically intervene to preserve graft function before graft failure has occurred. Since understanding the importance of matching genetic variation at the HLA region between donors and recipients and translating this into clinical practise to improve transplant outcome, much focus has been placed on trying to identify additional genetic predictors of transplant outcome/function. This review will focus on how candidate gene studies have identified variants within immunosuppression, immune response, fibrotic pathways, and specific ethnic groups, which correlate with graft outcome. We will also discuss the challenges faced by candidate gene studies, such as differences in donor and recipient selection criteria and use of small data sets, which have led to many genes failing to be consistently associated with transplant outcome. This review will also look at how recent advances in our understanding of and ability to screen the genome are starting to provide new insights into the mechanisms behind long-term graft loss and with it the opportunity to target these pathways therapeutically to ultimately increase graft lifespan and the associated benefits to patients.

Fluorodeoxyglucose F(18) Positron Emission Tomography Coupled With Computed Tomography in Suspected Acute Renal Allograft Rejection

Management of kidney transplant recipients (KTRs) with suspected acute rejection (AR) ultimately relies on kidney biopsy; however, noninvasive tests predicting nonrejection would help avoid unnecessary biopsy. AR involves recruitment of leukocytes avid for fluorodeoxyglucose F(18) ((18) F-FDG), thus (18) F-FDG positron emission tomography (PET) coupled with computed tomography (CT) may noninvasively distinguish nonrejection from AR. From January 2013 to February 2015, we prospectively performed 32 (18) F-FDG PET/CT scans in 31 adult KTRs with suspected AR who underwent transplant biopsy. Biopsies were categorized into four groups: normal (n = 8), borderline (n = 10), AR (n = 8), or other (n = 6, including 3 with polyoma BK nephropathy). Estimated GFR was comparable in all groups. PET/CT was performed 201 ± 18 minutes after administration of 3.2 ± 0.2 MBq/kg of (18) F-FDG, before any immunosuppression change. Mean standard uptake values (SUVs) of both upper and lower renal poles were measured. Mean SUVs reached 1.5 ± 0.2, 1.6 ± 0.3, 2.9 ± 0.8, and 2.2 ± 1.2 for the normal, borderline, AR, and other groups, respectively. One-way analysis of variance demonstrated a significant difference of mean SUVs among groups. A positive correlation between mean SUV and acute composite Banff score was found, with r(2)  = 0.49. The area under the receiver operating characteristic curve was 0.93, with 100% sensitivity and 50% specificity using a mean SUV threshold of 1.6. In conclusion, (18) F-FDG PET/CT may help noninvasively prevent avoidable transplant biopsies in KTRs with suspected AR.

A novel cyclic helix B peptide inhibits dendritic cell maturation during amelioration of acute kidney graft rejection through Jak-2/STAT3/SOCS1

We recently synthesized a novel proteolysis-resistant cyclic helix B peptide (CHBP) that exhibits promising renoprotective effects. Dendritic cells (DCs) play an activation role in acute rejection (AR). Thus, the present study was designed to investigate the effects of CHBP on DCs in a rat renal transplantation model. The left kidney was harvested from male Lewis rats and then transplanted into male Wistar rats with or without CHBP treatment. Five successive treatment doses of CHBP after transplantation significantly ameliorated AR with lower histological injury, apoptosis and CD4⁺ and CD8⁺ T-cell infiltration in renal allografts. CHBP reduced IFN-γ and IL-1β levels but increased IL-4 and IL-10 levels in the serum. The number of mature DCs was significantly decreased in renal allografts treated with CHBP. In addition, incubating DCs with CHBP in vitro led to reduction in TNF-α, IFN-γ, IL-1β and IL-12 levels and increase of IL-10 expression at the protein level in the supernatant. Mechanistically, CHBP inhibited TLR activation-induced DC maturation by increasing SOCS1 expression through Jak-2/STAT3 signaling. In conclusion, CHBP suppresses renal allograft AR by inhibiting the maturation of DCs via Jak-2/STAT3/SOCS1 signaling, suggesting that CHBP may be an potential therapeutic drug for treating renal AR.

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.

Association of BK Virus Titers With Lymphocyte Count in Renal Transplant Patients

OBJECTIVES

Regular screening for the BK virus (BKV) is recommended for early intervention in renal transplant patients. Identification of predictors for the development of BK viremia would improve their monitoring. We performed a retrospective study investigating whether the lymphocyte count may be a predictor of BKV development in renal transplant patients.

PATIENTS AND METHODS

We retrospectively analyzed 268 renal transplant patients who were followed in our clinic from January 2011 to August 2014. The viral loads of BKV in blood detected by quantitative real-time polymerase chain reaction test were performed according to relevant guidelines. We also retrospectively monitored lymphocyte count, creatinine, immunosuppressive drug doses, and tacrolimus/cyclosporine/mTor inhibitors levels during the same time as BKV screening. Demographic and other clinical data were extracted from patients' files. The calculation of correlation coefficients and receiver operating characteristics (ROC) curve analysis were performed.

RESULTS

Overall, 16 patients (5.9%) who experienced BKV-DNA positivity were included the study. Mean age of patients was 38.2 ± 12.8 years. All patients received steroid and calcineurin inhibitors (CNIs). Mycophenolate mofetil/mycophenolic acid (MMF/MPA) was administered to 14 patients. BKV-DNA was found in 64 of the 88 (72.7%) plasma samples. The lymphocyte count on the first day of positive BKV-DNA test was significantly lower than in those with negative BKV-DNA results (1700/μl vs 2400/μl, respectively; P = .009). Its AUC of the ROC curve was 0.77 (P = .012). The optimal cutoff point for lymphocyte count was 1900/μl, and sensitivity and specificity for predict BKV positivity were 75% and 78.57%, respectively. We also found that lymphocyte count negatively correlated with the first detectable BKV titers (r = -0.438; P = .015). However, there is no relation between CNI/mTOR inhibitor levels, MMF/MPA doses, lymphocyte count, and all BKV-titers.

CONCLUSIONS

Decreased lymphocyte count may be a predictor for preceding BKV viremia. Clinicians should be more careful in terms of the decreased lymphocyte count in case of BKV replication in renal transplant patients.

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.