Alemtuzumab induction in pediatric kidney transplantation

Recipient parenchymal lymphatic cells are crucial for direct and indirect pathways of allorecognition. We proposed that alemtuzumab, being infused several weeks pretransplant could eradicate peripheral lymphatic cells and promote donor‐specific tolerance. We present here a single center, retrospective review of 101 consecutive living‐donor kidney transplantations to pediatric patients aged from seven month to 18 yr, performed between September 2006 and April 2010. Immunosupression protocol included two 30 mg doses of alemtuzumab: first given 12–29 d prior to transplantation and second at the time of transplantation. Maintenance immunosupression was based on combination of low dose and wide range CNI and mycophenolate. Patients were followed for 3.8 ± 1.4 yr and protocol biopsies were taken one month, one, and three yr post transplant. The Kaplan–Meier graft and patient survival was 96% and 97% for one yr, 89% and 93% for three yr. Biopsy proven acute rejection developed in 26% patients at one yr and in 35% at two yr, no rejections occurred beyond two yr. We conclude that alemtuzumab pretreatment prior to living related donor kidney transplantation allows to reach satisfactory middle‐term results in pediatric patients with wide range and low CNI concentrations.     

Early protocol biopsies in pediatric renal transplantation: Interest for the adaptation of immunosuppression

GPB are often performed in PRT to detect subclinical acute rejection or IF/TA. Reducing immunosuppression side effects without increasing rejection is a major concern in PRT. We report the results of GPB in children transplanted with a steroid‐sparing protocol adapted to immunological risk. Children under 18 yr who received a renal transplantation between April 1, 2009 and May 31, 2012 were included. Immunosuppression consisted of an antibody induction therapy, tacrolimus, and MMF for all recipients. CSs were administered to children under five yr old, or receiving a second allograft. Twenty‐eight children were included, 50% were CSs free. GPB were performed between three and six months. IF/TA was documented in seven biopsies; four of these seven children were CS free. One child, with CSs, presented a borderline rejection, and another child, steroid free, with significant inflammatory interstitial infiltrate, considered as a subclinical rejection, was treated with CSs pulses. The median eGFR was stable (74, 67.5, and 82 mL/min/1.73 m² at, respectively, seven days, three months, and one yr). Patient and graft survival were 100%. These results have to be confirmed in a larger cohort, with long‐term follow‐up.     

Engraftment and chimerism, particularly of T- and B-cells, in children undergoing allogeneic bone marrow transplantation

The spectrum of pediatric bone marrow transplantation has changed in recent years. Mismatched and unrelated donor transplants are common, demanding an increased vigilance to detect incipient graft failure, secondary lymphoma as well as relapse and other problems, which now are potentially treatable. To diagnose these complications it may be important to know whether blood and marrow cells are of recipient or donor origin. To evaluate the role of mixed donor-recipient chimerism in relation to clinical problems we adapted a polymerase chain-reaction technique, using fluorescent primers analyzing DNA fragment length polymorphisms, to follow prospectively 17 bone marrow grafted children. To increase the precision of chimerism analysis, immunomagnetically isolated leukocyte populations were assayed in selected cases. Five patients encountered clinical problems related to chimerism. One infant with adenosine deaminase deficiency failed to engraft stem cells, yet succumbed to graft-versus-host disease, mediated by mature donor T-cells. Three children developed significant mixed chimerism. One of these three patients died in relapse of leukemia, while the two other patients who had received T-cell depleted grafts had persistent recipient T-cells, in spite of engraftment. After 5 months, these were displaced by donor T-cells in one of the patients. In the fifth patient, also after T-cell depleted BMT, a fatal donor cell lymphoma occurred. Twelve children had stable full chimerism or in one case a low grade mixed chimerism and remain disease-free throughout follow up (median 9 months). In conclusion, the analysis of chimerism, particularly of separated leukocyte populations, offers an almost indispensable insight and a basis for therapeutic decisions in complicated situations such as grafting involving unrelated or mismatched donors, graft manipulation, adoptive immunotherapy and in immunodeficiency patients.     

Highly sensitive chimerism detection in blood is associated with increased risk of relapse after allogeneic hematopoietic cell transplantation in childhood leukemia

Analysis of chimerism in blood post‐HCT using STR‐PCR is routinely applied in parallel with quantification of MRD to predict relapse of leukemia. RQ‐PCR chimerism is 10‐ to 100‐fold more sensitive, but clinical studies in children are sparse. We analyzed IMC in blood samples following transplantation for acute lymphoblastic or myeloid leukemia in 56 children. IMC was defined as a minimum increase of (a) 0.1% or (b) 0.05% recipient DNA between two samples. The risk of relapse was higher in children with IMC of both 0.1% and 0.05% compared to children without IMC (HR 12.8 [95% CI: 3.9‐41.4; P < .0001] and 7.6 [95% CI: 2.2‐26.9; P < .01], respectively). The first IMC was detected at a median of 208 days prior to relapse. The 5‐year cumulative incidence of relapse for children with a single IMC was 45.5% (CI 12.3‐74.4) and 41.0% (14.2‐66.6) for IMC above 0.1% and 0.05%, respectively. However, in 47 and 38 children never attaining IMC > 0.1% and >0.05%, 10 and 8 children relapsed, respectively. In a landmark analysis, no association was found between IMC prior to 90 days post‐HCT and subsequent relapse by either classification of IMC and AUC for RQ‐PCR chimerism was 54.2% (95 CI 27.7‐ 84.8). Although limited by a retrospective design, these results indicate that monitoring of RQ‐PCR chimerism in peripheral blood may have a role in early detection of relapse in acute childhood leukemia .     

Early mixed T‐cell chimerism is predictive of pediatric AML or MDS relapse after hematopoietic stem cell transplant

Patients with acute myeloid leukemia (AML) who relapse after hematopoietic stem cell transplantation (HCT) have dismal outcomes. Our ability to predict those at risk for relapse is limited. We examined chimerism trends post‐HCT in 63 children who underwent HCT for AML or myelodysplastic syndrome (MDS). Mixed T‐cell chimerism at engraftment and absence of chronic graft versus host disease (cGVHD) were associated with relapse (P = 0.04 and P = 0.02, respectively). Mixed T‐cell chimerism at engraftment was predictive in patients without cGVHD (P = 0.03). Patients with engraftment mixed T‐cell chimerism may warrant closer disease monitoring and consideration for early intervention.     

Prevalence,risk factors,and consequences of overweight in children and adolescents who underwent renal transplantation – Short‐ and medium‐term analysis

To determine the prevalence and risk factors for (i) overweight/obesity and (ii) weight gain six months after transplantation and to study the effect of weight excess on graft function and survival. We performed a retrospective study of kidney transplanted children. Endpoints: (i) prevalence of overweight/obesity at sixth month, (ii) gaining 1.0 BMI SDS from one to six months. To study the effects of weight excess, graft function and survival at 36 months were the endpoints. The study included 197 individuals. At sixth month, 57/197 (29%) presented overweight/obesity, and the factors associated to this outcome were: (i) age at transplantation (OR = 3.04) and (ii) overweight/obesity in the first month (OR = 22.16). Groups presented no difference on graft function and survival at 36 months. From one to six months, 90/197 (46%) patients gained >1.0 BMI SDS. This outcome was associated with (i) female sex (OR = 2.50), (ii) steroids' pulses (OR = 2.98), (iii) steroids exposure (OR = 1.04), and (iv) living donor (OR = 2.69). The group that gained BMI presented a lower 36 months graft survival (86% vs. 98%, p < 0.001). Weight excess and gain after transplantation are frequent, particularly in younger female recipients and in those receiving high steroids exposure. The lower graft survival in patients with rapid weight gain deserves investigation.     

Donor‐specific anti‐HLA antibody production following pediatric ABO‐incompatible heart transplantation

ABO‐i heart transplantation can be performed in infants with end‐stage heart failure to increase organ availability. The development of newly detected DSAs is associated with decreased cardiac graft survival, and the effect of ABO‐i transplantation on DSA production is unknown. We examined DSA production and rejection frequency in infant recipients of ABO‐i and ABO‐c heart transplants via a retrospective cohort study of infant heart transplant recipients transplanted at a single pediatric center between January 2004 and November 2014. Patients were included if they were less than 1 year of age at transplant and had a minimum of 6 months follow‐up. DSA positivity was examined under two categories, either the lowest level detectable (MFI > 500) or a level presumed to have clinical relevance in our immunogenetics laboratory (MFI > 5000). Of 52 patients, 36 received ABO‐c transplants and 16 received ABO‐i transplants. Compared to ABO‐c recipients, the ABO‐i group showed a consistent but statistically non‐significant finding of less frequent ndDSA positivity (69.4% ABO‐c vs 43.8% ABO‐i with MFI >500, P = 0.122; 41.7% ABO‐c vs 25% ABO‐i with MFI >5000, P = 0.353). Additionally, ABO‐i patients were less likely to have any form of rejection (12.5% vs 47.2%, P = 0.027) or acute cellular rejection (6.3% vs 38.9%, P = 0.021). Our data suggest that infants receiving ABO‐i heart transplants may be less likely to develop ndDSAs or have rejection compared to same age ABO‐c recipients. Larger multicenter studies are needed to confirm results from this single center study.     

Survival outcomes scores (SOFT,BAR, and Pedi‐SOFT) are accurate in predicting post‐liver transplant survival in adolescents

SOFT and BAR scores utilize recipient, donor, and graft factors to predict the 3‐month survival after LT in adults (≥18 years). Recently, Pedi‐SOFT score was developed to predict 3‐month survival after LT in young children (≤12 years). These scoring systems have not been studied in adolescent patients (13–17 years). We evaluated the accuracy of these scoring systems in predicting the 3‐month post‐LT survival in adolescents through a retrospective analysis of data from UNOS of patients aged 13–17 years who received LT between 03/01/2002 and 12/31/2012. Recipients of combined organ transplants, donation after cardiac death, or living donor graft were excluded. A total of 711 adolescent LT recipients were included with a mean age of 15.2±1.4 years. A total of 100 patients died post‐LT including 33 within 3 months. SOFT, BAR, and Pedi‐SOFT scores were all found to be good predictors of 3‐month post‐transplant survival outcome with areas under the ROC curve of 0.81, 0.80, and 0.81, respectively. All three scores provided good accuracy for predicting 3‐month survival post‐LT in adolescents and may help clinical decision making to optimize survival rate and organ utilization.     

20‐ to 25‐year patient and graft survival following a single pediatric liver transplant—Analysis of the United Network of Organ Sharing database: Where to go from here

To understand factors contributing to liver graft loss and patient death, we queried a national database designed to follow pediatric patients transplanted between 1987 and 1995 till adulthood. A comparison was made to a cohort transplanted between 2000 and 2014. The 5‐, 10‐, 15‐, 20‐, and 25‐year patient survival and graft survival were 95.5%, 93.7%, 89.1%, 80.8%, and 73.1%, and 92.5%, 86.7%, 77.6%, 68.7%, and 62.2%, respectively. The twenty‐year patient/graft survival was significantly worse in those transplanted between 5 and 17 years of age compared to those transplanted at <5 years of age (P < 0.001). For the modern era cohort, the 3‐year patient survival was significantly lower in children transplanted at 16‐17 years of age compared to those transplanted at <5 and 11‐15 years of age (P ≤ 0.02). The 3‐year graft survival was similarly lower in children transplanted at 16‐17 years of age compared to those transplanted at <5, 5‐10, and 11‐15 years of age (P ≤ 0.001). Infection as a cause of death occurred either early or >15 years post‐transplant. Chronic rejection remained the leading cause of graft loss in both cohorts and the commonest indication for retransplantation 20‐25 years following primary transplant. Further research is required to identify modifiable factors contributing to development of chronic rejection.     

Rejection is less common in children undergoing liver transplantation for hepatoblastoma

To compare the incidence of acute histologically proven rejection in children who have had a liver transplant for hepatoblastoma with a control group of children transplanted for biliary atresia (EHBA). A retrospective case notes based study was performed. Twenty patients were identified with hepatoblastoma who were transplanted at a single unit between 1991 and 2008. These were matched as closely as possible for age, gender, year of transplant and type of immunosuppression used to the control group transplanted for biliary atresia (n = 60). There was a significant decrease in rate of acute rejection as assessed by the rejection activity index (RAI) in the hepatoblastoma group (75% vs. 50%, respectively, p < 0.04). Chronic rejection was rare in both groups, but twice as common in the biliary atresia group. Equal levels of immunosuppression were achieved in both groups. Renal function was noted to be reduced one yr post‐transplant in both groups, as previously reported. A modified immunosuppression regimen could be considered in children with hepatoblastoma undergoing liver transplantation.     

Long‐term surveillance biopsy: Is it necessary after pediatric heart transplant?

Due to limited and conflicting data in pediatric patients, long‐term routine surveillance endomyocardial biopsy (RSB) in pediatric heart transplant (HT) remains controversial. We sought to characterize the rate of positive RSB and determine factors associated with RSB‐detected rejection. Records of patients transplanted at a single institution from 1995 to 2015 with >2 year of post‐HT biopsy data were reviewed for RSB‐detected rejections occurring >2 year post‐HT. We illustrated the trajectory of significant rejections (ISHLT Grade ≥3A/2R) among total RSB performed over time and used multivariable logistic regression to model the association between time and risk of rejection. We estimated Kaplan‐Meier freedom from rejection rates by patient characteristics and used the log‐rank test to assess differences in rejection probabilities. We identified the best‐fitting Cox proportional hazards regression model. In 140 patients, 86% did not have any episodes of significant RSB‐detected rejection >2 year post‐HT. The overall empirical rate of RSB‐detected rejection >2 year post‐HT was 2.9/100 patient‐years. The percentage of rejection among 815 RSB was 2.6% and remained stable over time. Years since transplant remained unassociated with rejection risk after adjusting for patient characteristics (OR = 0.98; 95% CI 0.78‐1.23; P = 0.86). Older age at HT was the only factor that remained significantly associated with risk of RSB‐detected rejection under multivariable Cox analysis (P = 0.008). Most pediatric patients did not have RSB‐detected rejection beyond 2 years post‐HT, and the majority of those who did were older at time of HT. Indiscriminate long‐term RSB in pediatric heart transplant should be reconsidered given the low rate of detected rejection.     

A nipple‐valve technique for ureteroneocystostomy in pediatric kidney transplantation

The ureteroneocystostomy in kidney transplantation can be performed with a variety of techniques. Over a 20‐yr period, we utilized a technique of nipple‐valve ureteroneocystostomy for the pediatric kidney transplants performed at our institution. The distal ureter is everted upon itself and anchored in place with four interrupted sutures to create a nipple valve, which is then inserted into the bladder and sewn mucosa‐to‐mucosa with the same sutures. The muscularis layer is closed around the ureter without tunneling and without routine ureteral stenting. After 109 transplants, patient survival was 97.2, 97.2, and 86.9% at one, five, and 10 yr, respectively. Graft survival was 91.7, 71.7, and 53.9% at one, five, and 10 yr, respectively. The most common cause of graft loss was acute or chronic rejection, seen in 75% of those experiencing graft loss. Two patients (1.8%) developed pyelonephritis in the transplanted kidney. Nipple‐valve ureteroneocystostomy in pediatric kidney transplantation is a safe and simple method for performing the ureterovesical anastomosis with a low rate of pyelonephritis after transplantation.     

In vivo T‐cell depletion using alemtuzumab in family and unrelated donor transplantation for pediatric non‐malignant disease achieves engraftment with low incidence of graft vs. host disease

In vivo T‐cell depletion, using alemtuzumab therapy prior to SCT, can reduce the incidence of GVHD. This treatment has a potential to delay immune reconstitution resulting in increased morbidity due to viral illnesses. We retrospectively analyzed data on all pediatric patients with non‐malignant disorders who received alemtuzumab‐based conditioning regimens in our center over the last 10 yr (n = 91). Our data show an OS of 91.2%. The incidence of acute (grade 2–4) GVHD was 18.7% and that of chronic GVHD 5.5%. Viremia due to adenovirus, EBV and CMV was seen in 19.8%, 64.8% and 39.6% patients, respectively, with only two deaths attributed to viral infection (adenovirus). Chimerism level at three month was predictive of graft outcome. Nine patients, who had graft failure after first SCT, were salvaged with a second SCT using RIC and same donor (if available). Based on these results, we conclude that the use of in vivo T‐cell depletion is safe, achieves good chimerism and does not lead to increased morbidity and mortality due to viral infections. It is associated with a reduced incidence of chronic GVHD.     

Results of pediatric living donor compared to deceased donor liver transplantation in the PELD/MELD era: Experience from two centers on two different continents

The LDLT option in the pediatric population allows recipients to be transplanted early. A total of 202 consecutive pediatric liver transplants from two different institutions—108 (LDLT) and 94 (DDLT)—were retrospectively compared. Overall, one‐ and three‐yr patient and graft survival were similar between DDLT and LDLT. ACR was greater in recipients of DDLT at one and three yr (50.8% and 61.0%) compared to LDLT (30.8% and 32.2%) (p = 0.002). When the data were stratified according to PELD/MELD score, LDLT with a low score had better one‐ and three‐yr graft survival (96.2% and 96.2%) compared to DDLT (88.2% and 85.2%) (p = 0.02), with comparable patient survival (p = 0.75). Patient and graft survival were similar between DDLT and LDLT in the high PELD/MELD group. Lower incidence of ACR in both low and high PELD/MELD groups was (29.6% and 34.3%) for LDLT compared to DDLT (50.3% and 53.3%, p = 0.002 and p = 0.028, respectively). Regardless of PELD/MELD score, status, age group, and recipient weight, LDLT provides excellent patient and graft survival with a lower incidence of rejection compared to DDLT.     

Application of an epitope‐based allocation system in pediatric kidney transplantation

Donor–recipient HLA mismatch remains a leading cause for sensitization and graft loss in kidney transplantation. HLA compatibility at an epitope level is emerging as an improved method of matching compared with current HLA antigen allocation. A novel epitope‐based allocation approach to prospectively exclude donors with high‐level mismatches was implemented for pediatric KTRs on the DD waiting list. Nineteen consecutive transplants were followed for 12 months, including eight DD KTRs listed with eplet exclusions, as well as three DD KTRs and eight LD KTRs without exclusions. KTRs with eplet exclusions had estimated GFR of 78.5 mL/min/1.73 m², no episodes of rejection, and time to transplant 6.55 months. HLA‐A, HLA‐B, HLA‐DR antigen mismatches were similar between all groups. KTRs with exclusions had significantly lower class II eplet mismatches (20.4) than the contemporary DD KTRs without exclusions (63.7) and DD KTRs transplanted in the preceding decade (46.9). dnDSAs were identified in two of eight DD KTRs with exclusions, two of three DD KTRs without exclusions and five of eight LD KTRs. Epitope‐based allocation achieved timely access to transplantation, low class II eplet mismatches, and low rates of dnDSAs in the first year. This strategy requires longer follow‐up and larger numbers, but has the potential to reduce anti‐HLA sensitization and improve both graft survival and opportunities for future retransplantation.     

Analysis of factors affecting immune recovery and initial response to tetanus after DTaP vaccination in pediatric allogeneic HSCT patients

Transfer of donor immunity after allo‐HSCT is limited, requiring re‐vaccination after HSCT. The CDC 2009 guidelines introduced earlier vaccination post‐HSCT with a uniform vaccination strategy. This study objective was to describe predictors of immune recovery and initial response to tetanus after DTaP vaccination post‐HSCT. We conducted a retrospective chart review of pediatric allo‐HSCT patients transplanted between July 1, 2007–June 30, 2012 who survived >1 yr without relapse (N = 27). Response to tetanus one month after the initial dose of DTaP was defined as a ≥4 fold increase in tetanus titers ≥1 month after vaccination. Wilcoxon rank‐sum exact test and Kruskall–Wallis tests were used to analyze CD4, CD8, and CD19 counts. Exact conditional logistic regression was utilized to analyze initial tetanus vaccination response. A statistically significant increase in median CD4, CD8, and CD19 counts occurred from six to 12 months post‐HSCT (p ≤ 0.0001, 0.005, 0.004). Only 36% of patients had initial tetanus vaccination response at first attempt post‐HSCT. None of the variables tested were statistically significant in predicting initial tetanus response to vaccination. There was no association between predictors of immune recovery or transplant variables and initial tetanus response. A uniform vaccination strategy is unlikely to provide protective antibodies for many post‐HSCT patients and should be evaluated in larger studies.     

Higher doses of CD34+ PBPC are associated with a rapid acquisition of full donor chimerism and lower risk of relapse after allogeneic transplantation in pediatric patients with hematological malignancies

We conducted a retrospective study assessing the predictive value of early full donor chimerism status for relapse after allogeneic peripheral blood progenitor cell transplantation in 40 children aged between 1 and 16 years (median 8) with leukemia. The only variable that had a significant influence on chimerism status in either univariate or multivariate analysis was the number of CD34 cells infused. We found that the patients who were in complete donor chimerism by day +30 had a lower probability of relapse than those who were not (14% ± 6% versus 54% ± 15%; HR, 5.24; 95% confidence interval, 2.10-43.63; P = 0.003). Mixed chimerism by day +30, absence of chronic GvHD, and advanced disease at transplantation were significant risk factors for relapse in our patients. Children who presented early complete chimerism had a probability of developing chronic graft versus host disease significantly higher than patients with mixed chimerism (P = 0.04). Therefore, the analysis of chimerism kinetic in children undergoing peripheral blood progenitor cell transplantation would permit an early identification of patients at risk of relapse and patients with high risk of developing chronic graft versus host disease.     

Delayed graft function in pediatric deceased donor kidney transplantation: Donor‐related risk factors and impact on two‐yr graft function and survival: A single‐center analysis

There is mounting evidence that the quality of organs from cadaver donors may be influenced by events occurring around the time of brain death. Aim of this present study was to analyze the correlation of DGF with brain‐dead donor variables in a single‐center pediatric population and to evaluate DGF influence on patients‐ and grafts outcome. End‐points of the study were DGF prevalence, DGF donor‐related risk factors, graft function, patient‐ and graft survival rate, respectively, at six, 12, and 24 months FU. The univariate analysis showed that donor age above 15 yr and vascular cause of donor brain death represented risk factors for DGF. The multivariate analysis confirmed as independent risk factors for DGF donor age >15 yr. At six months FU, DGF showed a negative impact on graft function. In conclusion, among all considered brain‐dead donor resuscitation parameters, just non‐traumatic cause of death turned out to be of impact for DGF. Donor age >15 yr represented the only independent risk factor for prolonged DGF in our series of children. At two‐yr FU, DGF showed a transient negative impact on six‐month graft function.     

The impact of flow PRA on outcome in pediatric heart recipients in modern era: An analysis of the Pediatric Heart Transplant Study database

Data from patients in the Pediatric Heart Transplant Study (PHTS) registry transplanted between 2010 and 2014 were analyzed to determine the association between HLA antibody (PRA) determined by SPA using Luminex or flow cytometry with a positive retrospective cross‐match and the post‐transplant outcomes of acute rejection and graft survival. A total of 1459 of 1596 (91%) recipients had a PRA reported pretransplant; 26% had a PRA > 20%. Patients with a PRA > 20% were more likely to have CHD, prior cardiac surgery, ECMO support at listing, and waited longer for transplantation than patients with a PRA <20%. Patients with higher PRA% determined by SPA were predictive of a positive retrospective cross‐match determined by flow cytometric method (P < .001). A PRA > 50% determined by SPA was independently associated with worse overall graft survival after first month of transplant in both unadjusted and adjusted for all other risk factors. In this large multicenter series of pediatric heart transplant recipients, an elevated PRA determined by SPA remains a significant risk factor in the modern era.