Design and Methods of the Validating Injury to the Renal Transplant Using Urinary Signatures (VIRTUUS) Study in Children.

Lack of noninvasive diagnostic and prognostic biomarkers to reliably detect early allograft injury poses a major hindrance to long-term allograft survival in pediatric kidney transplant recipients. METHODS: Validating Injury to the Renal Transplant Using Urinary Signatures Children's Study, a North American multicenter prospective cohort study of pediatric kidney transplant recipients, aims to validate urinary cell mRNA and metabolite profiles that were diagnostic and prognostic of acute cellular rejection (ACR) and BK virus nephropathy (BKVN) in adult kidney transplant recipients in Clinical Trials in Organ Transplantation-4. Specifically, we are investigating: (1) whether a urinary cell mRNA 3-gene signature (18S-normalized CD3ε, CXCL10 mRNA, and 18S ribosomal RNA) discriminates biopsies with versus without ACR, (2) whether a combined metabolite profile with the 3-gene signature increases sensitivity and specificity of diagnosis and prognostication of ACR, and (3) whether BKV-VP1 mRNA levels in urinary cells are diagnostic of BKVN and prognostic for allograft failure. RESULTS: To date, 204 subjects are enrolled, with 1405 urine samples, including 144 biopsy-associated samples. Among 424 urine samples processed for mRNA, the median A260:280 ratio (RNA purity) was 1.91, comparable with Clinical Trials in Organ Transplantation-4 (median 1.82). The quality control failure rate was 10%. Preliminary results from urine supernatant showed that our metabolomics platform successfully captured a broad array of metabolites. Clustering of pool samples and overlay of samples from various batches demonstrated platform robustness. No study site effect was noted. CONCLUSIONS: Multicenter efforts to ascertain urinary biomarkers in pediatric kidney transplant recipients are feasible with high-quality control. Further study will inform whether these signatures are discriminatory and predictive for rejection and infection.

School and sports participation post-transplant.

Pediatric recipients of life-saving organ transplants are living longer, with improved graft and overall survivals. After successful transplant, children are encouraged to return to "normal life," with school attendance and participation in age-appropriate physical activities. This transition may cause stress to the recipients, parents, teachers, and other participating caregivers and staff. Planning for school reentry and assuring education for and open lines of communication with the school staff can help alleviate some of this discomfort and ease the process for the patient and the family. Cardiovascular disease has emerged as the leading cause of death in survivors of pediatric transplantation and is contributed to by modifiable risk factors such as obesity, hypertension, and the MS. Physical activity is a proven tool in decreasing surrogate markers of this risk. Sports participation is an important way to promote an enjoyment of physical activity that can ideally persist into adulthood, but conflicting advice and opinions exist regarding type and participation in physical activity. Moreover, specific recommendations are likely not applicable to all recipients, as certain degrees of rehabilitation may be needed depending on degree and length of illness. In general, a program of rehabilitation and increased physical activity has been shown to be safe and effective for most pediatric transplant recipients. Focusing on optimizing the "normal" childhood activities of going to school and participating in sports can improve the physical, social, cognitive, and mental health outcomes of this population after transplant and should be prioritized.

Varicella infection following vaccination in a pediatric kidney transplant recipient.

Live viral vaccines have historically been avoided in children after solid organ transplantation. Multiple reports of safety and immunogenicity, largely in the pediatric liver transplant population, have led to a reconsideration of this recommendation. Here, we report the case of a 4-year-old boy who inadvertently received the live attenuated MMR-varicella vaccine (MMRV) at a routine well-child visit 16 months after receiving a living donor kidney transplant. This was not known until after he was admitted with rash and documented disseminated varicella infection 5 weeks later. He was treated with intravenous acyclovir followed by oral therapy and recovered fully. This case and its discussion illustrate what is still unknown about the risk-to-benefit ratio of live viral vaccination in any individual transplant recipient. Criteria to determine which patients should receive these vaccines should be evaluated before their use after transplant becomes routine, and all recipients and their families should be counseled to have a low threshold to seek medical care for any febrile illness or rash after live viral vaccination.

Utility of thrombophilia screening in pediatric renal transplant recipients.

Thrombosis after kidney transplantation may result in catastrophic outcomes, including graft loss. Thrombophilia has been implicated in post-transplant thrombosis; data, however, are inconclusive on the impact of acquired and inherited thrombophilia and resultant thrombosis in renal graft recipients. We aimed to evaluate whether identifying children with thrombophilia during the pretransplant evaluation predicted post-transplant outcomes. We reviewed 100 kidney transplants performed in 100 children, aged 1-18 years, in a single-center retrospective study. Routine pretransplant comprehensive thrombophilia evaluation was completed. Thrombophilia was demonstrated in 36% patients (N = 36). TEs occurred in 11 patients before kidney transplant. Low PS and antithrombin were found in 9/86 (10.5%) and 2/89 (2.2%) children, respectively. Heterozygosity for FLV and PGM were found in 5/81 (6.2%) and 1/93(1.1%) children, respectively. A post-transplant thrombotic event occurred in 10 children (10%); six involved the renal transplant. The association between a history of a pretransplant thrombotic event and post-operative renal graft thrombosis approached, but did not reach significance (P = 0.071). There was no association between preoperative screening abnormalities and post-operative TEs. Graft loss due to a thrombotic event occurred in two patients; none had underlying thrombophilia. Our data suggest that the utility of universal, comprehensive preoperative thrombophilia testing is not beneficial in determining risk of post-operative graft thrombosis. Thrombophilia testing may be considered in a select population with a history of pretransplant thrombotic event.

BK polyomavirus infection in pediatric heart transplant recipients: a prospective study.

BKV infection and nephropathy complicate pediatric HTx, but the incidence and time course of the disease are unknown. We assessed the incidence of BKV infection and its association with kidney dysfunction in pediatric HTx recipients. A single center prospective study compared pediatric (<18 years) HTx recipients, with and without BKV infection, who received an allograft between September 2013 and December 2014. Screening of urine for BKV was performed prior to transplant, and at week 1, and at months 3, 6, 9, 12, and 15 months post-transplantation. Serum for BKV DNA was assayed if BK viruria was present. Statistics included Fisher's exact test and Student's t test. Twelve patients were enrolled. Two patients were removed per parent request. Two (20%) had BK viruria and one (10%) had BK viremia. No patients developed BKVN. BK viruria was present within 2 months following transplantation. There were no identifiable risk factors for BKV infection and no statistically significant difference in renal function between the groups; however, there was a trend toward worsening renal function in those with BKV infection. BKV infection can occur early following heart transplantation. Screening for BK viruria should be considered in HTx recipients.

Prevalence of BK polyomavirus infection and association with renal dysfunction in pediatric heart transplant recipients.

BACKGROUND: BK polyomavirus (BKV) infection and nephropathy complicate renal allografts; however, their effect in the native kidneys of pediatric heart transplant (HTx) recipients is unknown. We assessed the prevalence of BKV infection and its association with kidney dysfunction in survivors of pediatric HTx. METHODS: A single-center retrospective study compared pediatric (aged <18 years ) HTx recipients, with and without BKV (controls), who received an allograft from May 1989 to July 2013. Screening of urine for BKV was performed in patients with chronic kidney disease (CKD) stage ≥2 since 2006, and since April 2012 in all HTx recipients at least at an annual evaluation. Serum for BKV DNA was assayed if BK viruria was present. Data collected included recipient and donor demographics, the immunosuppressive regimen, and history of Epstein-Bar virus (EBV) and cytomegalovirus infection. Statistics included Fisher's exact test, chi-square test, Student's t-test, and multivariate logistic regression. RESULTS: Of 98 eligible recipients, 83 (85%) were screened: 28 (34%) had BK viruria, and 7 had BK viremia. One viremic patient had biopsy-proven BKV nephropathy that progressed to end-stage renal disease. Risk factors for BK viruria were (1) longer duration since HTx (6.02 vs 2.95 years; p = 0.01), (2) worsening estimated glomerular filtration rate (71.3 vs 86.3 ml/min/1.73 m(2), p = 0.03), (3) history of EBV infection (p = 0.0002), and (4) use of sirolimus (p = 0.0003). After multivariate logistic-regression, only history of EBV infection remained associated with BKV infection (p = 0.015). CONCLUSIONS: BKV may lead to BK viremia and BK nephropathy in pediatric HTx patients. Routine screening for BK viruria should be considered.

Clinical grand rounds: atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is a rare, lifethreatening, chronic, genetic disease of uncontrolled alternative pathway complement activation. The understanding of the pathophysiology and genetics of this disease has expanded over recent decades and promising new developments in the management of aHUS have emerged. Regardless of the cause of aHUS, with or without a demonstrated mutation or autoantibody, blockade of terminal complement activation through C5 is of high interest as a mechanism to ameliorate the disease. Eculizumab, an existing monoclonal antibody directed against C5 with high affinity, prevents the perpetuation of the downstream activation of the complement cascade and the damage caused by generation of the anaphylotoxin C5a and the membrane attack complex C5b-9, by blocking C5 cleavage. We report the successful use of eculizumab in a patient after kidney transplantation and discuss the disease aHUS.

The primary hyperoxalurias.

The primary hyperoxalurias (PHs) are rare autosomal-recessive inborn errors of metabolism. In the most severe form (type 1), recurrent kidney stones and progressive nephrocalcinosis lead to the loss of kidney function, accompanied by systemic oxalosis, and often requires dialysis and/or transplantation. The variety of genetic mutations leading to PH increasingly are being defined, resulting in the ability to diagnose most patients accurately via minimally invasive means. During and after definitive diagnosis, supportive therapies with pyridoxine supplementation, urinary crystallization inhibitors, and hydration should be used, but have varying success. Emerging information about the renal tubular and intestinal transport of oxalate is leading to increasing evidence to support the use of oxalate-degrading bacteria (probiotics) and enzymes in the treatment of PH. Organ transplantation historically has offered the only potential cure for PH, and may include kidney-alone, combined liver-kidney, or pre-emptive liver-alone transplantation. Exciting new approaches in the treatment of type 1 PH, however, are under investigation. These include the restoration of defective enzymatic activity through the use of chemical chaperones, hepatocyte cell transplantation, or enzyme replacement by recombinant gene therapy. These novel approaches illustrate the goal for the ideal treatment of PH: correcting the genetic defect without exposing patients to the life-long risks associated with organ transplantation.

Hyperoxaluria and systemic oxalosis: current therapy and future directions.

Excessive urinary oxalate excretion, termed hyperoxaluria, may arise from inherited or acquired diseases. The most severe forms are caused by increased endogenous production of oxalate related to one of several inborn errors of metabolism, termed primary hyperoxaluria. Recurrent kidney stones and progressive medullary nephrocalcinosis lead to the loss of kidney function, requiring dialysis or transplantation, accompanied by systemic oxalate deposition that is termed systemic oxalosis. For most primary hyperoxalurias, accurate diagnosis leads to the use of therapies that include pyridoxine supplementation, urinary crystallisation inhibitors, hydration with enteral fluids and, in the near future, probiotic supplementation or other innovative therapies. These therapies have varying degrees of success, and none represent a cure. Organ transplantation results in reduced patient and organ survival when compared with national statistics. Exciting new approaches under investigation include the restoration of defective enzymatic activity through the use of chemical chaperones and hepatocyte cell transplantation, or recombinant gene therapy for enzyme replacement. Such approaches give hope for a future therapeutic cure for primary hyperoxaluria that includes correction of the underlying genetic defect without exposure to the life-long dangers associated with organ transplantation.