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

BK polyomavirus DNAemia, allograft rejection, and de novo donor-specific antibodies after lowering target tacrolimus levels in pediatric kidney transplant recipients

BACKGROUND

BK polyomavirus (BKV) DNAemia is a challenging infectious complication after kidney transplant (KT). Reduction of immunosuppression is the mainstay of management, and tacrolimus is often the first immunosuppressive medication adjusted upon the diagnosis of BKV DNAemia. This study aimed to evaluate the impact of a new institutional protocol with lower target tacrolimus levels on BKV DNAemia, allograft rejection, and de novo donor-specific antibodies (dnDSA) among pediatric KT recipients.

METHODS

We conducted a retrospective chart review of all KT episodes between January 2013 and December 2018. The new protocol with lower target tacrolimus levels was implemented in March 2015. One hundred twenty-seven patients were included in primary analysis. All patients received induction with basiliximab and methylprednisolone and were maintained on a steroid-based immunosuppressive regimen.

RESULTS

In the post-intervention cohort, cumulative incidence of BKV DNAemia at 100 days (13.4% vs. 17.8%, p = .605) and 18 months post-KT (34.1% vs. 26.7%, p = .504) was not significantly different from the pre-intervention cohort. Biopsy-proven rejection rate did not change. However, we observed a trend toward earlier development of dnDSA in the post-intervention cohort using the Kaplan-Meier survival analysis (log-rank p = .06). Younger recipient age at the time of transplant was found to slightly increase the risk of BKV DNAemia (OR: 1.09, 95% CI [1.01, 1.16], p = .024). There was an association between BKV DNAemia and biopsy-proven rejection of any type (adjustedOR: 2.77, 95% CI [1.26, 6.23], p = .012), especially acute T-cell-mediated rejection grade 1A and above (adjustedOR: 2.95, 95% CI [1.06, 8.30], p = .037), after adjusted for recipient age at the time of transplant.

CONCLUSIONS

Targeting lower tacrolimus levels did not decrease the incidence of BKV DNAemia within 100 days or 18 months post-KT, nor did it increase the risk of biopsy-proven rejection among pediatric KT recipients in our center. However, there was a trend toward earlier development of dnDSA, which may portend worse long-term graft outcome post-KT. Our findings highlight the need for individualized immunosuppressive regimens based on immunologic and infectious risk factors and the importance of implementing innovative biomarkers to guide therapy and improve outcomes.

The Second International Consensus Guidelines on the Management of BK Polyomavirus in Kidney Transplantation

BK polyomavirus (BKPyV) remains a significant challenge after kidney transplantation. International experts reviewed current evidence and updated recommendations according to Grading of Recommendations, Assessment, Development, and Evaluations (GRADE). Risk factors for BKPyV-DNAemia and biopsy-proven BKPyV-nephropathy include recipient older age, male sex, donor BKPyV-viruria, BKPyV-seropositive donor/-seronegative recipient, tacrolimus, acute rejection, and higher steroid exposure. To facilitate early intervention with limited allograft damage, all kidney transplant recipients should be screened monthly for plasma BKPyV-DNAemia loads until month 9, then every 3 mo until 2 y posttransplant (3 y for children). In resource-limited settings, urine cytology screening at similar time points can exclude BKPyV-nephropathy, and testing for plasma BKPyV-DNAemia when decoy cells are detectable. For patients with BKPyV-DNAemia loads persisting >1000 copies/mL, or exceeding 10 000 copies/mL (or equivalent), or with biopsy-proven BKPyV-nephropathy, immunosuppression should be reduced according to predefined steps targeting antiproliferative drugs, calcineurin inhibitors, or both. In adults without graft dysfunction, kidney allograft biopsy is not required unless the immunological risk is high. For children with persisting BKPyV-DNAemia, allograft biopsy may be considered even without graft dysfunction. Allograft biopsies should be interpreted in the context of all clinical and laboratory findings, including plasma BKPyV-DNAemia. Immunohistochemistry is preferred for diagnosing biopsy-proven BKPyV-nephropathy. Routine screening using the proposed strategies is cost-effective, improves clinical outcomes and quality of life. Kidney retransplantation subsequent to BKPyV-nephropathy is feasible in otherwise eligible recipients if BKPyV-DNAemia is undetectable; routine graft nephrectomy is not recommended. Current studies do not support the usage of leflunomide, cidofovir, quinolones, or IVIGs. Patients considered for experimental treatments (antivirals, vaccines, neutralizing antibodies, and adoptive T cells) should be enrolled in clinical trials.

Beyond the First Year: Epidemiology and Management of Late-Onset Opportunistic Infections After Kidney Transplantation

Late opportunistic infections (OI) occurring beyond the first year after kidney transplantation (KT) are poorly described and not targeted by prophylactic strategies. We performed a ten-year retrospective monocentric cohort study describing epidemiology, risk factors and impact of late OI occurring 1 year after KT. We included clinically symptomatic OI requiring treatment besides BK virus nephropathy. Control groups included early OI occurring in the first year after KT, and KT recipients without OI since KT and alive with a functional allograft at 1 year. Among 1066 KT recipients, 185 (19.4%) presented a first episode of OI 21.0 (8.0-45.0) months after KT: 120 late OI (64.9%) and 65 early OI (35.1%). Late OI were mainly viral (N = 83, 69.2%), mostly herpes zoster (HZ) (N = 36, 43.4%). Pneumocystis represented most late fungal infections (N = 12/25, 48%). Compared to early OI, we reported more pneumocystis (p = 0.002) and less invasive aspergillosis (p = 0.01) among late OI. Patients with late OI were significatively younger at KT (54.0 ± 13.3 vs. 60.2 ± 14.3 years, p = 0.05). Patient and allograft survival rates between late OI and control groups were similar. Only age was independently associated with mortality. While late OI were not associated with higher mortality or graft loss, implementing prophylactic strategies might prevent such infections.

Diagnostic performance of GcfDNA in kidney allograft rejection: a meta-analysis

In this comprehensive meta-analysis, our objective was to evaluate the diagnostic utility of graft-derived cell-free DNA (GcfDNA) in kidney allograft rejection and explore associated factors. We conducted a thorough search of PubMed, Embase, and the Cochrane Library databases, spanning from their inception to September 2022. Statistical analysis was executed utilizing Stata 15, Meta-DiSc 1.4, and Review Manager 5.4 software. The combined pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and the area under the summary receiver operating characteristics (SROC) curve from the synthesis of findings across ten studies were as follows: 0.75 (0.67-0.81), 0.78 (0.72-0.83), 3.36 (2.89-4.35), 0.32 (0.24-0.44), 8.77 (4.34-17.74), and 0.83 (0.80-0.86), respectively. Among the ten studies primarily focused on GcfDNA's diagnostic potential for antibody-mediated rejection (ABMR), the optimal cut-off threshold demonstrated substantial diagnostic efficacy, with pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, DOR, and area under the summary receiver operating characteristics curve values of 0.83 (0.74-0.89), 0.75 (0.70-0.80), 3.37 (2.64-4.30), 0.23 (0.15-0.36), 14.65 (7.94-27.03), and 0.85 (0.82-0.88), respectively. These results underscore the high diagnostic accuracy of GcfDNA in detecting rejection. Furthermore, the optimal cut-off threshold proves effective in diagnosing ABMR, while a 1% threshold remains a robust diagnostic criterion for rejection. Notably, for ABMR diagnosis, droplet digital PCR digital droplet polymerase chain reaction emerges as a superior method in terms of accuracy when compared to other techniques. Nonetheless, further research is warranted to substantiate these findings.

Pre-Existing Intrarenal Parvovirus B19 Infection May Relate to Antibody-Mediated Rejection in Pediatric Kidney Transplant Patients

Viral infections can lead to transplant dysfunction, and their possible role in rejection is described. In total, 218 protocol biopsies performed in 106 children at 6, 12 and 24 months after transplantation were analyzed according to Banff '15. RT-PCR for cytomegalovirus, Epstein-Barr virus, BK virus and Parvovirus B19 was performed on blood and bioptic samples at the time of transplant and each protocol biopsy. The prevalence of intrarenal viral infection increases between 6 and 12 months after transplantation (24% vs. 44%, p = 0.007). Intrarenal Parvovirus B19 infection is also associated with antibody-mediated rejection (ABMR) (50% ABMR vs. 19% T-cell-mediated rejection, p = 0.04). Moreover, Parvovirus infection is higher at 12 months of follow-up and it decreases at 48 months (40.4% vs. 14%, p = 0.02), while in 24% of grafts, Parvovirus is already detectable at the moment of transplantation. Intrarenal Parvovirus B19 infection seems to be related to ABMR in pediatric kidney recipients. The graft itself may be the way of transmission for Parvovirus, so performance of a PCR test for Parvovirus B19 should be considered to identify high-risk patients. Intrarenal Parvovirus infection presents mainly during the first-year post-transplantation; thus, we recommend an active surveillance of donor-specific antibodies (DSA) in patients with intrarenal Parvovirus B19 infection during this period. Indeed, it should be considered a treatment with intravenous immunoglobulins in patients with intrarenal Parvovirus B19 infection and DSA positivity, even in the absence of ABMR criteria for kidney biopsy.

BK virus genotypes and humoral response in kidney transplant recipients with BKV associated nephropathy

BACKGROUND

Among kidney transplant recipients (KTR) with BK virus associated nephropathy (BKVN), BKV genotypes' evolution and anti-BKV humoral response are not well established. We aim to analyze BKV replication and genetic evolution following transplantation, and characterize concomitant anti-BKV-VP1 humoral response.

METHODS

We retrospectively analyzed 32 cases of biopsy-proven BKVN. Stored plasma and kidney biopsies were tested for BKV viral load, and VP1 sequencing performed on positive samples. BKV-VP1 genotype-specific neutralizing antibodies (NAbs) titers were determined at transplantation and BKVN.

RESULTS

At the time of BKVN diagnosis, BKV viral load was 8.2 log₁₀ IU/10⁶ cells and 5.4 log₁₀ IU/mL in kidney and plasma, respectively. VP1 sequencing identified the same BKV-subtype in both compartments in 31/32 cases. At the time of transplantation, 8/20 (40%) of biopsies tested positive for BKV detection, whereas concomitant BKV viremia was negative. VP1 sequencing identified a different subtype compared to BKVN in 5/6 of these samples. This was confirmed following transplantation: 8 patients had a BKV+ biopsy before BKV viremia, and VP1 sequencing identified a different subtype compared to BKVN in all of them. After the onset of BKV viremia and prior to BKVN diagnosis, the BKV subtype in BKV+ plasma and kidney biopsy was the same as the one isolated at BKVN. BKV-VP1 NAbs titers were significantly higher at the time of BKVN compared to transplantation (p = .0031), with similar titers across genotypes.

CONCLUSION

Altogether, our data suggest that among some KTR with BKVN, the BKV genotype from the donor may not be responsible for BKVN pathogenesis.

Characteristics, risk factors and outcome of BKV nephropathy in kidney transplant recipients: a case-control study

BACKGROUND

Following kidney transplantation, BK virus associated nephropathy (BKVN) occurs in 1 to 10% of kidney transplant recipients (KTR) and represents a major cause of graft loss. We aim at identifying factors associated with biopsy proven BKVN among KTR.

METHODS

We conducted a retrospective case-control study including all KTR with a biopsy-proven diagnosis of BKVN between 2005 and 2019. Clinical characteristics and outcome were described. For each case, one control KTR without BKV infection was identified and matched by age, transplant date, and donor status. Factors associated with BKVN diagnosis were identified using exact conditional logistic regression. Comparative survival was described using Kaplan-Meier estimator.

RESULTS

Sixty-four cases of BKVN were identified among 1737 new kidney transplantation (3.7% prevalence). Clinical characteristics did not differ between groups, except for a higher c-PRA among cases. BKVN occurred in a median time of 11 (5-14.5) months after KT, and was associated with a significantly impaired graft function at diagnosis. Following BKVN, 61 (95%) of the patients had immunosuppression reduction, which led to BKV DNAemia resolution in 49% of cases. In multivariate analysis, factors associated with BKVN diagnosis were lymphopenia < 500/mm³ and a prednisone dose > 7.5 mg/day. Median duration of follow-up was 40 months for both groups. BKVN was associated with a significantly increased risk of graft rejection (P = 0.02) and return to dialysis (P = 0.01).

CONCLUSIONS

BKVN remains a severe complication in KTR and is associated with an increased risk for acute rejection and return to dialysis. Lymphopenia below 500/mm³ and corticosteroid maintenance therapy are significantly associated with biopsy-proven BKVN diagnosis.

Development of de novo donor-specific antibodies in renal transplant recipients with BK viremia managed with immunosuppression reduction

BACKGROUND

Reduction of immunosuppression (IS) upon detection of Polyomavirus (BK) viremia is widely used to prevent BK virus nephropathy. This retrospective case-control study assesses the frequency of de novo donor-specific antibodies (dnDSA) in renal transplant recipients with IS modulation due to BK viremia and the associated risk of antibody mediated rejection.

METHODS

Our cohort included recipients of kidney transplantation between 2007 and 2017 with clinical, HLA antibody, and biopsy data. BK positivity was defined as viremia >10 000 c/ml or biopsy proven BK nephropathy. A total of 190 BK cases matched our inclusion criteria, each case was matched with two controls based on gender, donor type, and transplant within 1 year (N = 396).

RESULTS

Despite lower number of HLA antigen mismatches (mean = 3.5 vs. 4.4, p < .001), dnDSA rates were higher in BK cases than in control group (22.1% vs. 13.9%, p = .02), with the majority detected following IS reduction for BK infection, and arising earlier posttransplant compared with no BK infection (294d vs. 434d, p < .001). Antibody mediated rejection rates were similar between cases and controls (8.9% and 8.3%, respectively), but rejection was more likely to occur earlier posttransplant in the BK cases (354d vs. 602d, p = .03).

CONCLUSION

Our data suggest a link between IS reduction and the generation of dnDSA and/or rejection, supporting close monitoring for DSA in patients with reduced IS due to BK infection given their increased risk to develop dnDSA.

Virus-Associated Nephropathies: A Narrative Review

While most viral infections cause mild symptoms and a spontaneous favorable resolution, some can lead to severe or protracted manifestations, specifically in immunocompromised hosts. Kidney injuries related to viral infections may have multiple causes related to the infection severity, drug toxicity or direct or indirect viral-associated nephropathy. We review here the described virus-associated nephropathies in order to guide diagnosis strategies and treatments in cases of acute kidney injury (AKI) occurring concomitantly with a viral infection. The occurrence of virus-associated nephropathy depends on multiple factors: the local epidemiology of the virus, its ability to infect renal cells and the patient's underlying immune response, which varies with the state of immunosuppression. Clear comprehension of pathophysiological mechanisms associated with a summary of described direct and indirect injuries should help physicians to diagnose and treat viral associated nephropathies.

Long-Term Infectious Complications of Kidney Transplantation

Infections remain a common complication of solid-organ transplantation. Most infections in the first month after transplant are typically health care-associated infections, whereas late infections, beyond 6-12 months, are community-acquired infections. Opportunistic infections most frequently present in the first 12 months post-transplant and can be modulated on prior exposures and use of prophylaxis. In this review, we summarize the current epidemiology of postkidney transplant infections with a focus on key viral (BK polyomavirus, cytomegalovirus, Epstein-Barr virus, and norovirus), bacterial (urinary tract infections and Clostridioides difficile colitis), and fungal infections. Current guidelines for safe living post-transplant are also summarized. Literature supporting prophylaxis and vaccination is also provided.

Occurrence of de novo Donor Specific Antibodies after Covid-19 in kidney transplant recipients is low despite immunosuppression modulation

Introduction

Methods

Results

Conclusion

Innate Immunity Response to BK Virus Infection in Polyomavirus-Associated Nephropathy in Kidney Transplant Recipients

BK polyomavirus (BKV) mainly causes infection in uroepithelial and renal tubular epithelial cells of either immunocompetent or immunocompromised hosts. Despite asymptomatic or mild clinical features in immunocompetent hosts with BK infection, serious complications are frequently found in immunocompromised patients, especially patients with kidney transplantation. Accordingly, BKV-associated nephropathy (BKVN) demonstrates a wide range of clinical manifestations, including ureteric stenosis and hemorrhagic cystitis. In addition, BKV re-infection in post-kidney transplantation is also a main cause of kidney allograft dysfunction and graft loss. Since the direct anti-BKV is unavailable, immune response against BKV infection is the main mechanism for organism control and might be a novel strategy to treat or suppress BKV. As such, the innate immunity, consisting of immune cells and soluble molecules, does not only suppress BKV but also enhances the subsequent adaptive immunity to eradicate the virus. Furthermore, the re-activation of BKV in BKVN of kidney-transplanted recipients seems to be related to the status of innate immunity. Therefore, this review aims to collate the most recent knowledge of innate immune response against BKV and the association between the innate immunity status of kidney-transplanted recipients and BKV re-activation.

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

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

Characterization of Kidney Retransplantation Following Graft Failure Due to BK Virus Nephropathy

INTRODUCTION

Immunosuppression following kidney transplantation increases risk of BK polyomavirus reactivation, a common cause of graft dysfunction and failure. Subsequent retransplantation is a viable option that has not been extensively studied. This study further characterizes BK Virus Nephropathy (BKVN) and retransplantation in the most expansive population to date, geographically, temporally, and in magnitude.

MATERIALS AND METHODS

The OPTN/UNOS database was used to identify patients who received kidney or kidney-pancreas transplantation between 1987 and 2018 that resulted in BKVN-attributed failure (n = 1587). This population was divided into those who underwent retransplantation (n = 495) and those who did not (n = 1092).

RESULTS

The retransplanted cohort was younger (45 vs. 53 yr; P<0.0001) and had fewer prior kidney transplants (P<0.003), lower expected post-transplant survival (P<0.001), lower rates of delayed graft function (DGF) (14.1% vs. 22.2%; P=0.0008), a greater proportion of white patients (55.4% vs. 43.2%; P=0.0002), a greater proportion of living donors (35.8% vs. 23.0%; P<0.0001), and longer allograft lifespan (2.95 vs. 2.41 yr; P<0.0001), compared to those not retransplanted. Among retransplants, DGF and high kidney donor profile index (KDPI) were associated with decreased allograft lifespan (P=0.001, P=0.0005, respectively). Steroid induction had no effect on allograft lifespan when compared to steroid-free regimens (P=0.915). Retransplanted allografts lasted longer than previous BKVN-failed grafts (10.44 and 3.70 years, respectively; P<0.0001).

CONCLUSIONS

Retransplantation following BKVN-associated graft failure has been associated with favorable outcomes. To maximize allograft lifespan in retransplantation, clinicians may consider selection of low KDPI donors, prevention of delayed graft function, and tailored immunosuppressive regimens that minimize steroids.

Chronic Kidney Allograft Disease: New Concepts and Opportunities

Chronic kidney disease (CKD) is increasing in most countries and kidney transplantation is the best option for those patients requiring renal replacement therapy. Therefore, there is a significant number of patients living with a functioning kidney allograft. However, progressive kidney allograft functional deterioration remains unchanged despite of major advances in the field. After the first post-transplant year, it has been estimated that this chronic allograft damage may cause a 5% graft loss per year. Most studies focused on mechanisms of kidney graft damage, especially on ischemia-reperfusion injury, alloimmunity, nephrotoxicity, infection and disease recurrence. Thus, therapeutic interventions focus on those modifiable factors associated with chronic kidney allograft disease (CKaD). There are strategies to reduce ischemia-reperfusion injury, to improve the immunologic risk stratification and monitoring, to reduce calcineurin-inhibitor exposure and to identify recurrence of primary renal disease early. On the other hand, control of risk factors for chronic disease progression are particularly relevant as kidney transplantation is inherently associated with renal mass reduction. However, despite progress in pathophysiology and interventions, clinical advances in terms of long-term kidney allograft survival have been subtle. New approaches are needed and probably a holistic view can help. Chronic kidney allograft deterioration is probably the consequence of damage from various etiologies but can be attenuated by kidney repair mechanisms. Thus, besides immunological and other mechanisms of damage, the intrinsic repair kidney graft capacity should be considered to generate new hypothesis and potential therapeutic targets. In this review, the critical risk factors that define CKaD will be discussed but also how the renal mechanisms of regeneration could contribute to a change chronic kidney allograft disease paradigm.

Deceased-Donor Acute Kidney Injury and BK Polyomavirus in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

BK polyomavirus (BKV) infection commonly complicates kidney transplantation, contributing to morbidity and allograft failure. The virus is often donor-derived and influenced by ischemia-reperfusion processes and disruption of structural allograft integrity. We hypothesized that deceased-donor AKI associates with BKV infection in recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 1025 kidney recipients from 801 deceased donors transplanted between 2010 and 2013, at 13 academic centers. We fitted Cox proportional-hazards models for BKV DNAemia (detectable in recipient blood by clinical PCR testing) within 1 year post-transplantation, adjusting for donor AKI and other donor- and recipient-related factors. We validated findings from this prospective cohort with analyses for graft failure attributed to BKV within the Organ Procurement and Transplantation Network (OPTN) database.

RESULTS

The multicenter cohort mean kidney donor profile index was 49±27%, and 26% of donors had AKI. Mean recipient age was 54±13 years, and 25% developed BKV DNAemia. Donor AKI was associated with lower risk for BKV DNAemia (adjusted hazard ratio, 0.53; 95% confidence interval, 0.36 to 0.79). In the OPTN database, 22,537 (25%) patients received donor AKI kidneys, and 272 (0.3%) developed graft failure from BKV. The adjusted hazard ratio for the outcome with donor AKI was 0.7 (95% confidence interval, 0.52 to 0.95).

CONCLUSIONS

In a well-characterized, multicenter cohort, contrary to our hypothesis, deceased-donor AKI independently associated with lower risk for BKV DNAemia. Within the OPTN database, donor AKI was also associated with lower risk for graft failure attributed to BKV.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_03_10_CJN18101120_final.mp3.

Polyomavirus Associated Nephropathy: Frequency and Graft Survival Analysis in Northeast of Iran

Background & Objective:

Polyomavirus-associated nephropathy (PVAN), mainly caused by the BK virus, is one of the most important infectious complications of kidney transplantation. The leading histopathologic characteristics of PVAN is viral cytopathic effects, such as nucleomegaly with smudged or clumped chromatin and intranuclear ground-glass inclusion, mostly in tubular epithelial cells. Moreover, tubular necrosis, tubulitis, interstitial inflammation, atrophy, and fibrosis have been noted. Positive immunohistochemistry (IHC) staining for SV-40 highlights the infected epithelial cells of renal tubules.

Methods:

A total of 85 core needle biopsies of transplanted kidneys were evaluated histologically and were stained for SV-40 using the IHC method. In addition, a follow-up of graft failure was performed.

Results:

Our findings revealed that the frequency of polyomavirus infection in kidney transplant patients in the Northeast of Iran is 4.7%. There was no significant correlation between PVAN and graft rejection. Although a higher rate of graft loss was observed in PVAN patients, in comparison with non-PVAN patients (25% vs. 14.8%), the difference was not statistically significant. Moreover, patients with immunohistochemically confirmed PVAN and those with histopathologic features of viral-like cytopathic effects had significantly lower graft survival in the follow-up period (42.5 vs. 196.8 months and 109.4 vs. 205.7 months, respectively).

Conclusion:

The frequency of polyomavirus infection in kidney transplant patients in the Northeast of Iran is 4.7%. There was no significant correlation between PVAN and graft rejection. Furthermore, we observed that polyomavirus infection accelerates the course of graft loss.

BK Virus-Associated Nephropathy after Renal Transplantation

Recent advances in immunosuppressive therapy have reduced the incidence of acute rejection and improved renal transplantation outcomes. Meanwhile, nephropathy caused by BK virus has become an important cause of acute or chronic graft dysfunction. The usual progression of infection begins with BK viruria and progresses to BK viremia, leading to BK virus associated nephropathy. To detect early signs of BK virus proliferation before the development of nephropathy, several screening tests are used including urinary cytology and urinary and plasma PCR. A definitive diagnosis of BK virus associated nephropathy can be achieved only histologically, typically by detecting tubulointerstitial inflammation associated with basophilic intranuclear inclusions in tubular and/or Bowman’s epithelial cells, in addition to immunostaining with anti-Simian virus 40 large T-antigen. Several pathological classifications have been proposed to categorize the severity of the disease to allow treatment strategies to be determined and treatment success to be predicted. Since no specific drugs that directly suppress the proliferation of BKV are available, the main therapeutic approach is the reduction of immunosuppressive drugs. The diagnosis of subsequent acute rejection, the definition of remission, the protocol of resuming immunosuppression, and long-term follow-up remain controversial.

Intravenous immunoglobulin as a preventive strategy against BK virus viremia and BKV-associated nephropathy in kidney transplant recipients-Results from a proof-of-concept study

BK virus (BKV) replication occurs frequently in kidney transplant recipients (KTR), potentially leading to BKV-associated nephropathy (BKVAN) and graft loss. Patients with high titers of BKV-neutralizing antibodies (NAbs) are protected against BKV replication, and intravenous immunoglobulin (IVIg) infusion can increase NAb titers. We investigated whether early IVIg administration prevents BKV replication in patients with low NAb titers (<4 log₁₀ against the BKV-specific genotype). Based on NAb titers on the day of transplantation, KTR followed in the Strasbourg University Hospital (n = 174) were retrospectively divided into the following 3 risk categories for BKV replication: (1) patients with low NAb titers ("high-risk") who received IVIg for the first 3 posttransplant months (n = 44), (2) patients with low NAb titers ("high-risk") who did not undergo IVIg treatment (n = 41), and (3) patients with high NAb titers ("low-risk") who did not receive IVIg (n = 89). At 12 posttransplant months, the incidence of BKV viremia in the high-risk group treated with IVIg (6.8%) was similar to that observed in the low-risk group (10.1%) and markedly lower than that of the untreated high-risk group (36.6%; P < .001). Similar results were observed with regard to BKVAN. We conclude that IVIg may be a valuable strategy for preventing BKV replication.

Increasing net immunosuppression after BK polyoma virus infection

BACKGROUND

Reducing immunosuppression can effectively treat BK viremia (BKV) and BK nephropathy, but has been associated with increased risks for acute rejection and development of donor-specific antibodies (DSA). To date there have been no systematic evaluations of re-escalating immunosuppression in transplant patients with resolving BKV. Importantly, the safety of this approach and impact on graft survival is unclear.

METHODS

We performed a single-center retrospective review of kidney transplant recipients between July 2011 and June 2013 who had immunosuppression reduction after developing BKV (plasma PCR ≥ 1000 copies/ml). Changes in immunosuppression and patient outcomes were tracked until occurrence of a complication event: biopsy-proven acute rejection (BPAR), detection of de novo DSA, or recurrent BKV. Patients were grouped according to whether or not net immunosuppression was eventually increased.

RESULTS

Out of 88 patients with BKV, 44 (50%) had net immunosuppression increased while the other 44 did not. Duration of viremia, peak viremia, induction, and sensitization status were similar between the two groups. In a Kaplan-Meier analysis, increasing immunosuppression was associated with less BPAR (P = .001) and a trend toward less de novo DSA development (P = .06). Death-censored graft survival (P = .27) was not different between the two groups. In the net immunosuppression increase group, recurrent BKV occurred in 22.7% without any BKV-related graft losses.

CONCLUSION

These findings support potential benefits of increasing immunosuppression in patients with low-level or resolved BKV, but prospective trials are needed to better understand such an approach.

Epidemiology of parvovirus B19 and anemia among kidney transplant recipients: A meta-analysis

Background

Persistent anemia has been described in kidney transplant (KTx) recipients with parvovirus B19 virus infection. However, the epidemiology of parvovirus B19 and parvovirus B19-related anemia after KTx remains unclear. We conducted this systematic review (1) to investigate the incidence of parvovirus B19 infection after KTx and (2) to assess the incidence of parvovirus B19 among KTx patients with anemia.

Materials and Methods

A systematic review was conducted in EMBASE, MEDLINE, and Cochrane databases from inception to March 2019 to identify studies that reported the incidence rate of parvovirus B19 infection and/or seroprevalence of parvovirus B19 in KTx recipients. Effect estimates from the individual studies were extracted and combined using random-effects, generic inverse variance method of DerSimonian and Laird. The protocol for this systematic review is registered with PROSPERO (no. CRD42019125716).

Results

Nineteen observational studies with a total of 2108 KTx patients were enrolled. Overall, the pooled estimated seroprevalence of parvovirus B19 immunoglobulin G was 62.2% (95% confidence interval [CI]: 45.8%-76.1%). The pooled estimated incidence rate of positive parvovirus B19 DNA in the 1^st year after KTx was 10.3% (95% CI: 5.5%-18.4%). After sensitivity analysis excluded a study that solely included KTx patients with anemia, the pooled estimated incidence rate of positive parvovirus B19 DNA after KTx was 7.6% (95% CI: 3.7%-15.0%). Among KTx with anemia, the pooled estimated incidence rate of positive parvovirus B19 DNA was 27.4% (95% CI: 16.6%-41.7%). Meta-regression analysis demonstrated no significant correlations between the year of study and the incidence rate of positive parvovirus B19 DNA (P = 0.33). Egger's regression asymmetry test was performed and demonstrated no publication bias in all analyses.

Conclusion

The overall estimated incidence of positive parvovirus B19 DNA after KTX is 10.3%. Among KTx with anemia, the incidence rate of positive parvovirus B19 DNA is 27.4%. The incidence of positive parvovirus B19 DNA does not seem to decrease overtime.

Combined association of recipient killer cell immunoglobulin-like haplotype AA and donor HLA-C*07 gene with BK virus associated nephropathy in kidney transplant patients

Kidney transplant recipient killer cell immunoglobulin-like receptors (KIR) genotype and HLA-C status of their donors have been separately associated with BK virus-associated nephropathy (BKVAN) and BK virus infection. Our aim was to determine whether different combinations of recipients KIR genes and donor HLA-C ligands influence the risk of BKVAN. Retrospective case-control study included 23 recipients with BKVAN and 46 recipients with persistently negative BK virus. Donor HLA-C*07 positivity was associated with lower odds for BKVAN, recipients bearing KIR haplotype AA or lacking any activating KIR genes were more frequent in BKVAN while recipient/donor combination HLA-C*07 negative/KIR AA positive was significantly associated with BKVAN. Our study complements and confirms results from several previously published studies, suggesting potential clinical usefulness.

The Use of Donor-Derived Cell-Free DNA for Assessment of Allograft Rejection and Injury Status

Patient monitoring after kidney transplantation (KT) for early detection of allograft rejection remains key in preventing allograft loss. Serum creatinine has poor predictive value to detect ongoing active rejection as its increase is not sensitive, nor specific for acute renal allograft rejection. Diagnosis of acute rejection requires allograft biopsy and histological assessment, which can be logistically challenging in some cases and carries inherent risk for complications related to procedure. Donor-derived cell-free DNA (dd-cfDNA), DNA of donor origin in the blood of KT recipient arising from cells undergoing injury and death, has been examined as a potential surrogate marker for allograft rejection. A rise in dd-cfDNA levels precedes changes in serum creatinine allows early detections and use as a screening tool for allograft rejection. In addition, when used in conjunction with donor-specific antibodies (DSA), it increases the pre-biopsy probability of antibody-mediated rejection (ABMR) aiding the decision-making process. Advancements in noninvasive biomarker assays such as dd-cfDNA may offer the opportunity to improve and expand the spectrum of available diagnostic tools to monitor and detect risk for rejection and positively impact outcomes for KT recipients. In this this article, we discussed the evolution of dd-cfDNA assays and recent evidence of assessment of allograft rejection and injury status of KT by the use of dd-cfDNA.

Degree of Glomerulosclerosis in Procurement Kidney Biopsies from Marginal Donor Kidneys and Their Implications in Predicting Graft Outcomes

Background: This study aimed to assess the association between the percentage of glomerulosclerosis (GS) in procurement allograft biopsies from high-risk deceased donor and graft outcomes in kidney transplant recipients. Methods: The UNOS database was used to identify deceased-donor kidneys with a kidney donor profile index (KDPI) score > 85% from 2005 to 2014. Deceased donor kidneys were categorized based on the percentage of GS: 0-10%, 11-20%, >20% and no biopsy performed. The outcome included death-censored graft survival, patient survival, rate of delayed graft function, and 1-year acute rejection. Results: Of 22,006 kidneys, 91.2% were biopsied showing 0-10% GS (58.0%), 11-20% GS (13.5%), >20% GS (19.7%); 8.8% were not biopsied. The rate of kidney discard was 48.5%; 33.6% in 0-10% GS, 68.9% in 11-20% GS, and 77.4% in >20% GS. 49.8% of kidneys were discarded in those that were not biopsied. Death-censored graft survival at 5 years was 75.8% for 0-10% GS, 70.9% for >10% GS, and 74.8% for the no biopsy group. Among kidneys with >10% GS, there was no significant difference in death-censored graft survival between 11-20% GS and >20% GS. Recipients with >10% GS had an increased risk of graft failure (HR = 1.27, p < 0.001), compared with 0-10% GS. There was no significant difference in patient survival, acute rejection at 1-year, and delayed graft function between 0% and 10% GS and >10% GS. Conclusion: In >85% KDPI kidneys, our study suggested that discard rates increased with higher percentages of GS, and GS >10% is an independent prognostic factor for graft failure. Due to organ shortage, future studies are needed to identify strategies to use these marginal kidneys safely and improve outcomes.

Outcomes of kidney retransplantation after graft loss as a result of BK virus nephropathy in the era of newer immunosuppressant agents

We conducted this study using the updated 2005-2016 Organ Procurement and Transplantation Network database to assess clinical outcomes of retransplant after allograft loss as a result of BK virus-associated nephropathy (BKVAN). Three hundred forty-one patients had first graft failure as a result of BKVAN, whereas 13 260 had first graft failure as a result of other causes. At median follow-up time of 4.70 years after the second kidney transplant, death-censored graft survival at 5 years for the second renal allograft was 90.6% for the BK group and 83.9% for the non-BK group. In adjusted analysis, there was no difference in death-censored graft survival (P = .11), acute rejection (P = .49), and patient survival (P = .13) between the 2 groups. When we further compared death-censored graft survival among the specific causes for first graft failure, the BK group had better graft survival than patients who had prior allograft failure as a result of acute rejection (P < .001) or disease recurrence (P = .003), but survival was similar to those with chronic allograft nephropathy (P = .06) and other causes (P = .05). The better allograft survival in the BK group over acute rejection and disease recurrence remained after adjusting for potential confounders. History of allograft loss as a result of BKVAN should not be a contraindication to retransplant among candidates who are otherwise acceptable.

Recent Advances and Clinical Outcomes of Kidney Transplantation

Recent advances in surgical, immunosuppressive and monitoring protocols have led to the significant improvement of overall one-year kidney allograft outcomes. Nonetheless, there has not been a significant change in long-term kidney allograft outcomes. In fact, chronic and acute antibody-mediated rejection (ABMR) and non-immunological complications following kidney transplantation, including multiple incidences of primary kidney disease, as well as complications such as cardiovascular diseases, infections, and malignancy are the major factors that have contributed to the failure of kidney allografts. The use of molecular techniques to enhance histological diagnostics and noninvasive surveillance are what the latest studies in the field of clinical kidney transplant seem to mainly focus upon. Increasingly innovative approaches are being used to discover immunosuppressive methods to overcome critical sensitization, prevent the development of anti-human leukocyte antigen (HLA) antibodies, treat chronic active ABMR, and reduce non-immunological complications following kidney transplantation, such as the recurrence of primary kidney disease and other complications, such as cardiovascular diseases, infections, and malignancy. In the present era of utilizing electronic health records (EHRs), it is strongly believed that big data and artificial intelligence will reshape the research done on kidney transplantation in the near future. In addition, the utilization of telemedicine is increasing, providing benefits such as reaching out to kidney transplant patients in remote areas and helping to make scarce healthcare resources more accessible for kidney transplantation. In this article, we discuss the recent research developments in kidney transplants that may affect long-term allografts, as well as the survival of the patient. The latest developments in living kidney donation are also explored.

Viral load and duration of BK polyomavirus viraemia determine renal graft fibrosis progression: histologic evaluation of late protocol biopsies

BACKGROUND

Polyomavirus BK (BKV) infection of the renal allograft causes destructive tissue injury with inflammation and subsequent fibrosis.

METHODS

Using a prospective cohort of patients after kidney transplantation performed between 2003 and 2012, we investigated the role of BKV viraemia in the development and progression of interstitial fibrosis and tubular atrophy (IFTA). The primary outcome was moderate-to-severe IFTA assessed by protocol biopsy at 36 months.

RESULTS

A total of 207 consecutive recipients were enrolled. Of these, 57 (28%) developed BKV viraemia with 10 (5%) cases of polyomavirus-associated nephropathy (PVAN). Transient (<3 months) BKV viraemia occurred in 70% of patients, and persistent (≥3 months) BKV viraemia in 30%. A high viral load (≥10 000 copies/mL) was detected in 18% and a low viral load (<10 000 copies/mL) in 61%, while the viral load could not be determined in 21%. Moderate-to-severe IFTA was significantly increased in high [71%; odds ratio (OR) = 12.1; 95% confidence interval (CI) 1.62-90.0; P = 0.015] or persistent BKV viraemia (67%; OR = 6.33; 95% CI 1.19-33.7; P = 0.031) with corresponding rise in 'interstitial fibrosis + tubular atrophy' scores. Only patients with transient low BKV viraemia showed similar incidence and progression of IFTA to the no-BKV group. Persistent low BKV viraemia was uncommon yet the progression of fibrosis was significant. Only recipients with PVAN experienced inferior graft survival at 5 years.

CONCLUSIONS

These data suggest that only transient low BKV viraemia does not negatively affect the progression of allograft fibrosis in contrast to excessive risk of severe fibrosis after high or persistent BKV viraemia.

Promises of Big Data and Artificial Intelligence in Nephrology and Transplantation

Kidney diseases form part of the major health burdens experienced all over the world. Kidney diseases are linked to high economic burden, deaths, and morbidity rates. The great importance of collecting a large quantity of health-related data among human cohorts, what scholars refer to as “big data”, has increasingly been identified, with the establishment of a large group of cohorts and the usage of electronic health records (EHRs) in nephrology and transplantation. These data are valuable, and can potentially be utilized by researchers to advance knowledge in the field. Furthermore, progress in big data is stimulating the flourishing of artificial intelligence (AI), which is an excellent tool for handling, and subsequently processing, a great amount of data and may be applied to highlight more information on the effectiveness of medicine in kidney-related complications for the purpose of more precise phenotype and outcome prediction. In this article, we discuss the advances and challenges in big data, the use of EHRs and AI, with great emphasis on the usage of nephrology and transplantation.

Successful treatment of BK virus associated-nephropathy in a human immunodeficiency virus-positive kidney transplant recipient

BK virus (BKV) is an opportunistic pathogen in those with impaired immunity. Viral replication is generally asymptomatic but is able to induce cytopathic alterations in renal cells. If BKV infection is left untreated, it leads to BKV-associated nephropathy (BKVAN) and graft loss. There is scarce experience in the management of BKV infection in kidney transplant recipients living with HIV. We report the successful treatment of BKVAN in an HIV-positive kidney transplant recipient who experienced BKV replication in the immediate post-transplantation period. A change in therapy from calcineurin inhibitor to sirolimus, steroid withdrawal and a short course of an immunomodulatory agent (leflunomide) controlled BKV viremia in the absence of drug side-effects or impairment of graft function.

BK Polyomavirus-associated nephropathy managed by screening policy in a real-life setting

BACKGROUND

BK polyomavirus-associated nephropathy (PyVAN) is an important complication after kidney transplantation. Prevalence ranges from 1% to 10%, and graft loss occurs in approximately 50% of the cases. There is no effective treatment, so early viral detection with immunosuppression tapering is the current strategy to prevent PyVAN.

AIMS

To verify the frequency of PyVAN in a single center and evaluate the response to immunosuppressive adjustments through graft survival analysis.

METHODS

Retrospective evaluation of a cohort of kidney transplant recipients with biopsy-proven PyVAN, compared with no-PyVAN patients regarding clinical aspects, immunosuppression, and graft survival over at least 2 years.

RESULTS

There were 1404 kidney transplants analyzed in the study period, 58 with biopsy-proven PyVAN. Cumulative incidence was 4.1%. Median time from transplantation to PyVAN diagnosis was 6 (1-41) months. PyVAN was associated with recipient male gender (P = .041) and deceased donation (P = .005). Graft survival was inferior for PyVAN compared to no-PyVAN patients, 81.8% vs 75.2%, P = .019. Thirteen (22.4%) PyVAN patients lost their grafts, nine (15.5%) losses attributed to BKPyV infection. Three patients with BKPyV-associated graft losses were submitted to a successful second kidney transplant, with no evidence of viral replication during follow-up.

CONCLUSION

PyVAN still is an important cause of kidney graft failure. Even though implementing active vigilance and immunosuppressive adjustment, this real-life single-center study demonstrated inferior graft survival in PyVAN patients compared to non-PyVAN.

BK polyomavirus genotypes in renal transplant recipients in the United States: A meta-analysis

BACKGROUND

In the United States, increasing ethnic diversity has been apparent. However, the epidemiology and trends of BKV genotypes remain unclear. This meta-analysis was conducted with the aim to assess the prevalence of BKV genotypes among kidney transplant (KTx) recipients in the United States.

METHODS

A comprehensive literature review was conducted through October 2018 utilizing MEDLINE, Embase, and Cochrane Database to identify studies that reported the prevalence of BKV subtypes and/or subgroups in KTx recipients in the United States. Pooled prevalence rates were combined using random effects, generic inverse variance method. The protocol for this study is registered with PROSPERO (no. CRD42019134582).

RESULTS

A total of eight observational studies with a total of 193 samples (urine, blood, and kidney tissues) from 188 BKV-infected KTX recipients were enrolled. Overall, the pooled estimated prevalence rates of BKV subtypes were 72.2% (95% confidence of interval [CI]: 62.7-80.0%) for subtype I, 6.8% (95% CI: 2.5-16.9%) for subtype II, 8.3% (95% CI: 4.4-15.1%) for subtype III, and 16.1% (95% CI: 10.4-24.2%) for subtype IV, respectively. While metaregression analysis demonstrated a significant positive correlation between year of study and the prevalence of BKV subtype I (slopes = +0.1023, P = .01), there were no significant correlations between year of study and percentages of BKV subtype II-IV (P > .05). Among KTx recipients with BKV subtype I, the pooled estimated percentages of BKV subgroups were 22.4% (95% CI: 13.7-34.5%) for subgroup Ia, 30.6% (95% CI: 17.7-47.5%) for subgroup Ib1, 47.7% (95% CI: 35.8-59.9%) for subgroup Ib2, and 4.1% (95% CI:1.2-13.3%) for subgroup Ic, respectively.

CONCLUSION

BKV subtype I is the most prevalent subtype among KTx recipients in the United States and its prevalence seems to increasing overtime. Subgroup Ib2 is the most common subgroup among BKV subtype I.

Reducing calcineurin inhibitor first for treating BK polyomavirus replication after kidney transplantation: long-term outcomes

BACKGROUND

Reducing immunosuppression is the mainstay of treating BK polyomavirus (BKPyV) viraemia after kidney transplantation, but the best approach, efficacy and impact are undefined. We established a standard operating procedure (SOP) treating BKPyV viraemia based on first reducing calcineurin inhibitor ('CNI first'). The aim of this study was to investigate long-term outcomes in 644 consecutive transplantations using this SOP.

METHODS

Patients were monitored for active BKPyV infection by urinary decoy cells and, if positive, by BKPyV viraemia. In case of sustained BKPyV viraemia >1000 copies/mL, immunosuppression was reduced stepwise according to the SOP. Patients were classified as 'no decoy cells' [n = 432 (66%)], 'decoy cells/no viraemia' [n = 107 (17%)] and 'viraemia' [n = 105 (17%)].

RESULTS

At 6-years post-transplant, graft survival was ∼84%, the clinical rejection rate was ∼25% and they were not different among the three groups (P = 0.14; P = 0.91). The median estimated glomerular filtration rate at the last follow-up was similar (range 49-53 mL/min, P = 0.08). Of 105 viraemic patients, 101 (96%) cleared BKPyV viraemia. In 39% of patients, viraemia clearance followed a tacrolimus reduction. A reduction of mycophenolic acid was required in 43% and discontinuation in 3%. No short-term graft loss was directly attributable to BKPyV-associated nephropathy. After a median follow-up of 5 years after clearance of BKPyV viraemia, 11/101 patients (11%) developed clinical rejection: 7 (7%) T-cell-mediated rejection and 4 (4%) antibody-mediated rejection (ABMR).

CONCLUSIONS

Immunosuppression reduction based on 'CNI first' leads to similar long-term outcomes in patients with/without BKPyV viraemia and is associated with a low risk for ABMR after clearance of BKPyV viraemia. Randomized trials are needed to compare the risks and benefits of immunosuppression reduction strategies in kidney transplant patients with BKPyV viraemia.

BK polyomavirus in solid organ transplantation-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

The present AST-IDCOP guidelines update information on BK polyomavirus (BKPyV) infection, replication, and disease, which impact kidney transplantation (KT), but rarely non-kidney solid organ transplantation (SOT). As pretransplant risk factors in KT donors and recipients presently do not translate into clinically validated measures regarding organ allocation, antiviral prophylaxis, or screening, all KT recipients should be screened for BKPyV-DNAemia monthly until month 9, and then every 3 months until 2 years posttransplant. Extended screening after 2 years may be considered in pediatric KT. Stepwise immunosuppression reduction is recommended for KT patients with plasma BKPyV-DNAemia of >1000 copies/mL sustained for 3 weeks or increasing to >10 000 copies/mL reflecting probable and presumptive BKPyV-associated nephropathy, respectively. Reducing immunosuppression is also the primary intervention for biopsy-proven BKPyV-associated nephropathy. Hence, allograft biopsy is not required for treating BKPyV-DNAemic patients with baseline renal function. Despite virological rationales, proper randomized clinical trials are lacking to generally recommend treatment by switching from tacrolimus to cyclosporine-A, from mycophenolate to mTOR inhibitors or leflunomide or by the adjunct use of intravenous immunoglobulins, leflunomide, or cidofovir. Fluoroquinolones are not recommended for prophylaxis or therapy. Retransplantation after allograft loss due to BKPyV nephropathy can be successful if BKPyV-DNAemia is definitively cleared, independent of failed allograft nephrectomy.

Effects of denosumab on bone metabolism and bone mineral density in kidney transplant patients: a systematic review and meta-analysis

OBJECTIVE

The use of immunosuppressive agents, especially glucocorticoids, are associated with increased risks of bone loss in kidney transplant patients. Denosumab, a potent antiresorptive agent, has been shown to increase bone mineral density (BMD) in patients with CKD. However, its effects on bone metabolism and BMD in kidney transplant patients remain unclear.

METHODS

A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through April 2018 to identify studies evaluating denosumab's effect on changes in bone metabolism and BMD from baseline to post-treatment course in kidney transplant patients. Study results were pooled and analyzed utilizing random-effects model. The protocol for this systematic review is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42018095055).

RESULTS

Five studies (a clinical trial and four cohort studies) with a total of 162 kidney transplant patients were identified. The majority of patients had a baseline eGFR ≥ 30 mL/min/1.73 m². After treatment (≥ 6 to 12 months), there were significant increases in BMD with standardized mean differences (SMDs) of 3.26 (95% CI 0.88-5.64) and 1.83 (95% CI 0.43 to 3.22) for lumbar spine and femoral neck, respectively. There were also significant increases in T scores with SMDs of 0.92 (95% CI 0.58 to 1.25) and 1.14 (95% CI 0.17 to 2.10) for lumbar spine and femoral neck, respectively. After treatment, there were no significant changes in serum calcium (Ca) or parathyroid hormone (PTH) from baseline to post-treatment course (≥ 6 months) with mean differences (MDs) of 0.52 (95% CI, - 0.13 to 1.16) mmol/L and - 13.24 (95% CI, - 43.85 to 17.37) ng/L, respectively. The clinical trial data demonstrated more asymptomatic hypocalcemia in the denosumab (12 episodes in 39 patients) than in the control (1 episode in 42 patients) group. From the cohort studies, the pooled incidence of hypocalcemia following denosumab treatment was 1.7% (95% CI 0.4 to 6.6%). All reported hypocalcemic episodes were mild and asymptomatic, but the majority of patients required Ca and vitamin D supplements.

CONCLUSION

Among kidney transplant patients with good allograft function, denosumab effectively increases BMD and T scores in the lumbar spine and femur neck. From baseline to post-treatment, there are no differences in serum Ca and PTH. However, mild hypocalcemia can occur following denosumab treatment, requiring monitoring and titration of Ca and vitamin D supplements.

Factors at de novo donor-specific antibody initial detection associated with allograft loss: a multicenter study

We aimed to evaluate patient factors including nonadherence and viral infection and de novo donor-specific antibody (dnDSA) characteristics [total immunoglobulin G (IgG), C1q, IgG3, and IgG4] as predictors of renal allograft failure in a multicenter cohort with dnDSA. We performed a retrospective observational study of 113 kidney transplant recipients with dnDSA and stored sera for analysis. Predictors of death-censored allograft loss were assessed by Cox proportional modeling. Death-censored allograft survival was 77.0% (87/113) during a median follow-up of 2.2 (IQR 1.2-3.7) years after dnDSA detection. Predictors of allograft failure included medication nonadherence [HR 6.5 (95% CI 2.6-15.9)], prior viral infection requiring immunosuppression reduction [HR 5.3 (95% CI 2.1-13.5)], IgG3 positivity [HR 3.8 (95% CI 1.5, 9.3)], and time post-transplant (years) until donor-specific antibody (DSA) detection [HR 1.2 (95% CI 1.0, 1.3)]. In the 67 patients who were biopsied at dnDSA detection, chronic antibody-mediated rejection [HR 11.4 (95% CI 2.3, 56.0)] and mixed rejection [HR 7.4 (95% CI 2.2, 24.8)] were associated with allograft failure. We conclude that patient factors, including a history of viral infection requiring immunosuppression reduction or medication nonadherence, combined with DSA and histologic parameters must be considered to understand the risk of allograft failure in patients with dnDSA.

Viral infections directly involved in kidney allograft function

Modern immunosuppressive therapy has dramatically reduced the incidence of acute rejection and improved graft survival in kidney transplant patients. However, infectious complications remain an important issue. Amongst the various pathogens, viruses such as adenovirus and polyomavirus BK can directly cause acute or chronic graft dysfunction. Adenovirus mainly causes haemorrhagic cystitis and tubulointerstitial nephritis in kidney transplant patients. While patients show apparent clinical symptoms such as fever, dysuria, gross haematuria, frequency and urgency of urination, and most patients show acute graft dysfunction, these symptoms and graft dysfunction are reversible. Polyomavirus BK infection, however, is asymptomatic but graft outcome is poor if the patient develops tissue-invasive nephropathy confirmed by graft biopsy. Recently, an attempt to create a pathological classification for predicting the clinical course has been made by the Banff Working Group on Polyomavirus Nephropathy. With regards to treatment, the basic strategy is a reduction of calcineurin inhibitor and/or antimetabolites, and the effectiveness of several adjunct treatments has been investigated in several clinical trials. There are other unresolved issues, such as the diagnosis of subsequent acute rejection, the definition of remission, methods of resuming immunosuppression and long-term follow-up. Most of all, development of effective vaccines and novel drug discovery are necessary to prevent the development and progression of BKV-associated nephropathy.