Immunologic benefit of maternal donors in pediatric living donor liver transplantation

Immunosuppression minimization is safe and associated with good long-term success in pediatric recipients of liver transplant

Immunosuppression reduction after liver transplant is an important strategy to mitigate long-term medication side effects. We describe our center's experience with immunosuppression minimization to once-daily calcineurin inhibitor dosing. Success was defined as continuing daily calcineurin inhibitor monotherapy with normal transaminases and no rejection. We performed a retrospective review of eligible children who received a liver transplant between 2009 and 2016, had a surveillance biopsy, and were on twice-daily calcineurin inhibitor monotherapy. Twenty-eight of 51 eligible patients were minimized to daily calcineurin inhibitor with goal 12-hour trough detectable. Nineteen patients (68%) had 1-year success, and 17 (61%) had long-term success at a median follow-up of 5.0 years (interquartile range (IQR): 2.9-6.6). Minimization failure occurred at a median of 0.6 years (IQR: 0.3-1.0) after dose reduction. Patients with long-term success had lower aspartate aminotransferase levels prior to minimization compared to those who failed with a median of 28.0 IU/L (IQR: 20.5-32.0) versus 32.0 IU/L (IQR: 30.0-37.0), p = 0.047. The long-term success group demonstrated a trend toward greater recipients of liver transplant from living donors (53% vs. 18%, p = 0.07). At the time of the last follow-up at a median of 5.0 years (IQR: 2.9-6.1) after surveillance biopsy, most (73%) patients who failed had returned to twice-daily calcineurin inhibitor monotherapy, all had liver enzymes <2 times the upper limit of normal, and there were no patient deaths or graft losses. In conclusion, immunosuppression minimization is safe in pediatric recipients of liver transplant and should be considered to reduce long-term medication side effects and improve patient quality of life. Future studies are necessary to follow long-term outcomes and develop biomarkers to predict minimization success.

Early Detection of Epstein-Barr Virus as a Risk Factor for Chronic High Epstein-Barr Viral Load Carriage at a Living-donor-dominant Pediatric Liver Transplantation Center

BACKGROUND

Epstein-Barr virus (EBV) infection and posttransplant lymphoproliferative disorders (PTLDs) after pediatric liver transplantation (LT) account for significant morbidity and mortality. Knowledge of EBV kinetics, epidemiology, and outcomes among pediatric living-donor LT cases is largely lacking. This study aims to provide clinical information related to EBV infection, chronic high EBV load (CHL) carriage, and PTLD at a living-donor-dominant pediatric LT center.

METHODS

A total of 5827 EBV load measurements from 394 LT recipients fulfilling inclusion criteria and their clinical data were analyzed. EBV loads >1000 copies/μg DNA (742 IU/μg DNA) were considered "high," and CHL was defined by persistence >6 mo.

RESULTS

The highlighted results were as follows: (1) 94% of recipients underwent living-donor LT; (2) 80% of EBV seronegative recipients developed first EBV infection <2 y post-LT, and their EBV loads were consistently higher than those of seropositive recipients within <3 y post-LT but did not differ thereafter; (3) 61 (15%) recipients met CHL criteria, but none developed PTLD; (4) age <5 y, cytomegalovirus seronegative donors, and early development of EBV DNAemia <6 mo post-LT were independent risk factors for CHL; (5) the incidence of rejections after 1-y post-LT was comparably low among CHL carriers whose immunosuppression was minimized.

CONCLUSIONS

Early detection of EBV following LT and CMV seronegative donors would facilitate risk stratification to prevent PTLD while titrating immunosuppression among pediatric LT recipients.

Prope tolerance after pediatric liver transplantation: Experience at Shiraz Organ Transplant Center

BACKGROUND

Children receive transplants at a younger age, and the period of immunosuppression therapy may extend over decades. However, immunosuppression seems to be responsible for long-term mortality and morbidity. Pediatric liver transplant recipients can benefit from achieving immune tolerance and the opportunity of freedom from lifelong immunosuppression. This study aimed to investigate the frequency of prope tolerance among pediatric liver transplant recipients and the characteristics of these patients.

METHODS

In this retrospective cohort study of pediatric liver transplant recipients, the medical records of transplant recipients treated at Shiraz Organ Transplant Center between 1994 and 2017 were reviewed. Prope tolerance was defined as normal laboratory values and stable clinical status on low-dose monotherapy. Children treated with low-dose monotherapy were categorized as the prope tolerant group. We compared the characteristics of prope tolerant recipients on low-dose monotherapy with patients on standard immunosuppression, i.e. full-dose tacrolimus plus steroids and mycophenolate mofetil. The data were analyzed with the t-test, chi-squared test, and a Cox proportional hazard model at a 5% significance level in SPSS software version 16.

RESULTS

A total of 585 children with a mean age of 8.32 ± 5.23 years were enrolled. 341 patients were categorized as prope tolerant and 244 comprised the full immunosuppression regimen group. Mean age at transplantation and rejection frequency were lower in the prope tolerant group (p < 0.001, p < 0.001). Based on the underlying diseases, metabolic/genetic, biliary tract, and cryptogenic liver diseases were significantly more prevalent in the prope tolerant group (p < 0.001). However, autoimmune liver disease was found to be more prevalent in the full immunosuppression regimen group. Also, those who received living organs (p = 0.001) and recipients of organs from female donors had a greater likelihood of achieving prope tolerant. According to the multiple Cox regression results, age at transplantation (p = 0.022), rejection frequency (p < 0.001), and autoimmune liver diseases (p = 0.028) had a prognostic effect on prope tolerance.

CONCLUSION

Factors as underlying disease, age at transplantation, and rejection frequency were factors that were predictive of prope tolerance in this sample of children. However, the risk of rejection should be considered during the tapering period.

Cross-decoration of dendritic cells by non-inherited maternal antigen-containing extracellular vesicles: Potential mechanism for PD-L1-based tolerance in cord blood and organ transplantation

Exposure to non-inherited maternal antigens (NIMA) during the fetal period induces lifelong split tolerance to grafts expressing these allo-antigens. In adult mice, the production of extracellular vesicles (EVs) from maternal microchimeric cells causes cross-decoration (XD) of offspring dendritic cells (DC) with NIMA and upregulation of PD-L1, contributing to NIMA tolerance. To see how this may apply to humans, we tested NIMA acquisition by fetal DCS in human cord blood. The average percentage of NIMA-XD among total DCs was 2.6% for myeloid and 4.5% for Plasmacytoid DC. These cells showed higher PD-L1 expression than their non-XD counterparts (mDC: p = .0016; pDC: p = .024). We detected CD9+ EVs bearing NIMA and PD-L1 in cord blood. To determine if this immune regulatory mechanism persists beyond the pregnancy, we analyzed NIMA-expressing kidney and liver transplant recipients. We found donor antigen XD DCs in peripheral blood and graft-infiltrating DCs. As in cord blood, the pattern of donor antigen expression was punctate, and PD-L1 expression was upregulated, likely due to both protein and miRNA acquired from EV. Our findings support a mechanism for split tolerance to NIMAs that develops during pregnancy and is recapitulated in adult transplant recipients.

Immunologic benefits of maternal living donor allografts in pediatric liver transplantation: fewer rejection episodes and no evidence of de novo allosensitization

BACKGROUND

Pediatric liver transplant (LT) recipients of maternal living liver donor (LLD) grafts have been reported to experience fewer rejection episodes. However, it is unclear whether this benefit translates to reduction in developing donor-specific antibody (DSA) among maternal-LLD recipients. The aim of this study was to compare immunologic outcomes among maternal-LLD, non-maternal-LLD, and deceased donor liver transplant (DDLT) recipients.

METHODS

Children (≤18 years) who underwent LT between 1/1998 and 12/2019 at two high-volume LT centers in North America were evaluated. Patients were divided into three groups by type of graft received (maternal-LLD, non-maternal LLD, and DDLT). Clinical variables and outcomes were compared according to each graft type.

RESULTS

A total of 450 pediatric primary LT were analyzed: 275 (61.1%) DDLT, 73 (16.2%) maternal-LLD, and 102 (22.6%) non-maternal-LLD. Children receiving LLD grafts were less likely to develop rejection when compared to the DDLT group (DDLT 46.9% vs. maternal-LLD 31.5% vs. non-maternal-LLD 28.4%, p = 0.001). There was no difference in rejection rates between maternal and non-maternal-LLD recipients. A higher percentage of maternal-LLD recipients were on immunosuppression monotherapy compared to non-maternal-LLD and DDLT recipients (6.7% vs. 1.2 vs. 2.4%, respectively). A subgroup of 68 patients were tested for DSA post-LT. Maternal-LLD recipients were less likely to develop de novo DSA (maternal-LLD 11.8% vs. non-maternal-LLD 19.3% vs. DDLT 43%, p = 0.018). None of the maternal-LLD recipients developed antibody-mediated rejection.

CONCLUSIONS

These data support the concept of immunologic benefit of maternal-LLD in pediatric LT, with lower rates of rejection and allosensitization post-LT when compared to DDLT recipients.

Clinical characteristics of immune tolerance after pediatric liver transplantation

Background

Clinical operational tolerance is the ultimate goal for liver transplantation. This study aimed to investigate the clinical characteristics of immune tolerance after pediatric liver transplantation and to identify the possible predictors.

Methods

The clinical data from 37 cases of pediatric patients 2 year later after liver transplantation surgery in the Children’s Hospital of Chongqing Medical University, China, were retrospectively analyzed. According to the status of the current immunosuppressant medications of the patients, they were divided into tolerance (n = 15) and Control (n = 22) groups. The current status regarding prope/operational tolerance was reviewed and screened based on the immunosuppressant medications.

Results

The patients in the tolerance group were younger than that of Controls (p < 0.001). The children in the tolerance group experienced no acute rejection episode and exhibited no obvious abnormalities in the liver function during the continuous follow-up period. The primary disease of the tolerance group were more often diagnosed with biliary atresia (p = 0.011), and received with a living donor liver graft (p = 0.005). There were less glomerular function, diabetes mellitus, arterial hypertension events presented in the tolerance group compared with the control group, indicating low toxicity profile.

Conclusion

In the current study, there were really certain quantity of recipients following liver transplantation attained long term immune tolerance, with low toxicity and satisfied liver graft function. The younger age of the recipient and maternal donor seems to promote long-term clinical immune tolerance. Further work in larger series should be required to describe the overall perspective of tolerance.

Maternal versus paternal living kidney transplant donation is associated with lower rejection in young pediatric recipients: A Collaborative Transplant Study report

BACKGROUND

Approximately 1700 children per year with end-stage kidney disease undergo kidney transplantation in Europe and the United States of America; 30%-50% are living donor kidney transplantations. There may be immunological differences between paternal and maternal donors due to transplacental exchange of cells between the mother and fetus during pregnancy leading to microchimerism. We investigated whether the outcome of living-related kidney transplantation in young children is different after maternal compared with paternal organ donation.

METHODS

Using the international Collaborative Transplant Study (CTS) database, we analyzed epidemiological data of 7247 children and adolescents aged <18 years who had received a kidney transplant from either mother or father. Risk of treated rejection episodes and death-censored graft failure were computed using the Kaplan-Meier method and multivariable Cox regression.

RESULTS

In the recipient age group 1-4 years, the rate of treated rejection episodes in recipients of kidneys from maternal donors (N = 195) during the first 2 years post-transplant was significantly lower (hazard ratio HR = 0.47, p = .004) than in patients receiving kidneys from paternal donors (N = 179). This association between donor sex and risk of treated rejections was not observed in children aged 5-9 years. The 5-year death-censored graft survival in children aged 1-4 years with a maternal or paternal donor was comparable.

CONCLUSIONS

Maternal kidney donation in young pediatric renal transplant recipients is associated with an approximately 50% lower rate of treated rejection than paternal kidney donation. Whether this phenomenon is due to maternal microchimerism-induced donor-specific hyporesponsiveness must be evaluated in prospective mechanistic studies.

Living Donor Versus Deceased Donor Pediatric Liver Transplantation: A Systematic Review and Meta-analysis

Reduced-size deceased donors and living donor liver transplantation (LDLT) can address the organ shortage for pediatric liver transplant candidates, but concerns regarding technical challenges and the risk of complications using these grafts have been raised. The aim of this study was to compare outcomes for pediatric LDLT and deceased donor liver transplantation (DDLT) via systematic review.

METHODS

A systematic literature search was performed to identify studies reporting outcomes of pediatric (<18 y) LDLT and DDLT published between 2005 and 2019. A meta-analysis was conducted to examine peri- and postoperative outcomes using fixed- and random-effects models.

RESULTS

Overall, 2518 abstracts were screened, and 10 studies met criteria for inclusion. In total, 1622 LDLT and 6326 DDLT pediatric patients from 4 continents were examined. LDLT resulted in superior patient survival when compared with DDLT at 1, 3, and 5 y post-LT (1-y hazard ratio: 0.58, 95% confidence interval [CI] 0.47-0.73, P < 0.0001). Similarly, LDLT resulted in superior graft survival at all time points post-LT when compared with DDLT (1-y hazard ratio: 0.56 [95% CI 0.46-0.68], P < 0.0001]. The OR for vascular complications was 0.73 (95% CI 0.39-1.39) and 1.31 (95% CI 0.92-1.86) for biliary complications in LDLT compared with DDLT, whereas LDLT was associated with lower rates of rejection (OR: 0.66 [95% CI 0.45-0.96], P = 0.03).

CONCLUSIONS

This meta-analysis demonstrates that LDLT may offer many advantages when compared with DDLT in children and suggests that LDLT should continue to be expanded to optimize outcomes for pediatric LT candidates.