Association of intraindividual tacrolimus variability with de novo donor-specific HLA antibody development and allograft rejection in pediatric kidney transplant recipients with low immunological risk

Age-Related Differences in Rejection Rates, Infections, and Tacrolimus Exposure in Pediatric Kidney Transplant Recipients in the CERTAIN Registry

Introduction

Data on age-related differences in rejection rates, infectious episodes, and tacrolimus exposure in pediatric kidney transplant recipients (pKTRs) on a tacrolimus-based immunosuppressive regimen are scarce.

Methods

We performed a large-scale analysis of 802 pKTRs from the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) registry from 40 centers in 14 countries. The inclusion criteria were a tacrolimus-based immunosuppressive regimen and at least 2 years of follow-up. The patient population was divided into 3 age groups (infants and young children aged <6 years, school-aged children 6-12 years, and adolescents aged >12 years) to assess age-related differences in outcome.

Results

Median follow-up was 48 months (interquartile range [IQR], 36-72). Within the first 2 years posttransplant, infants, and young children had a significantly higher incidence of infections (80.6% vs. 55.0% in adolescents, P < 0.001) and a significantly higher number of cumulative hospital days (median 13 days vs. 7 days in adolescents, P < 0.001). Adolescents had a significantly higher rate of biopsy-proven acute rejection episodes in the first-year posttransplant (21.7%) than infants and young children (12.6%, P = 0.007). Infants and young children had significantly lower tacrolimus trough levels, lower tacrolimus concentration-to-dose (C/D) ratios as an approximation for higher tacrolimus clearance, and higher tacrolimus interpatient variability (TacIPV) (all P < 0.01) than adolescents.

Conclusion

This is the largest study to date in European pKTRs on a tacrolimus-based immunosuppressive regimen, and it shows important age-related differences in rejection rates, infection episodes, as well as tacrolimus exposure and clearance. This data suggests that immunosuppressive therapy in pKTRs should be tailored and personalized according to the age-specific risk profiles of this heterogeneous patient population. The data may serve as a benchmark for future studies with novel immunosuppressive drugs.

Association of HLA B- and T-cell molecular mismatches with HLA antibodies, rejection, and graft survival in pediatric kidney transplantation

BACKGROUND

Optimizing graft survival and diminishing human leukocyte antigen (HLA) sensitization are essential for pediatric kidney transplant recipients. More precise HLA matching predicting epitope mismatches could reduce alloreactivity. We investigated the association of predicted HLA B- and T-cell molecular mismatches with the formation of de novo donor-specific antibodies, HLA antibodies, rejection, and graft survival.

METHODS

Forty-nine pediatric kidney transplant recipients transplanted from 2009 to 2020 were retrospectively studied. Donors and recipients were high-resolution HLA typed, and recipients were screened for HLA antibodies posttransplant. HLA-EMMA (HLA Epitope MisMatch Algorithm) and PIRCHE-II (Predicted Indirectly ReCognizable HLA Epitopes) predicted the molecular mismatches. The association of molecular mismatches and the end-points was explored with logistic regression.

RESULTS

Five recipients (11%) developed de novo donor-specific antibodies. All five had de novo donor-specific antibodies against HLA class II, with four having HLA-DQ antibodies. We found no associations between PIRCHE-II or HLA-EMMA with de novo donor-specific antibodies, HLA sensitization, graft loss, or rejection. However, we did see a tendency towards an increased odds ratio in PIRCHE-II predicting de novo donor-specific antibodies formation, with an odds ratio of 1.12 (95% CI: 0.99; 1.28) on HLA class II.

CONCLUSION

While the study revealed no significant associations between the number of molecular mismatches and outcomes, a notable trend was observed - indicating a reduced risk of dnDSA formation with improved molecular match. It is important to acknowledge, however, that the modest population size and limited observed outcomes preclude us from making definitive conclusions.

Tacrolimus intra-patient variability measures and its associations with allograft clinical outcomes in kidney transplantation

AIMS

Tacrolimus (Tac) is commonly prescribed in solid organ transplantation to prevent immune-mediated damage to the graft. However, its pharmacokinetics show substantial variability between and within patients. Intra-patient variability of tacrolimus (Tac-IPV) has emerged as a novel marker to predict transplant outcomes. Numerous studies report varying associations between Tac-IPV and clinical outcomes, with Tac-IPV measures showing wide discrepancies among these studies. This inconsistency could be a significant factor that influences the various outcomes reported in different studies. Our review comprehensively assesses the relationship between various Tac-IPV measures and their associations with clinical outcomes in transplant patients.

METHODS

A comprehensive literature search was conducted using the PubMed and Embase databases, covering the period from 2004 to March 31, 2023. The search focused on studies that examined the relationship between Tac-IPV and clinical outcomes in kidney transplantation (KT). The inclusion criteria were specific to studies addressing Tac-IPV, including measures such as standard deviation (SD), coefficient of variation (CV), time-weighted coefficient of variability (CV), mean absolute deviation (MAD), and Tac variability score (TVS). Clinical outcomes included the development of de novo donor-specific antibodies (dnDSA), rejection episodes, graft loss, and graft failure.

RESULTS

Among the 33 studies that met the inclusion criteria, a notable proportion presented conflicting findings in their assessment of various Tac-IPV measures regarding dnDSA, rejection episodes, graft loss, and graft failure.

CONCLUSIONS

Most studies have identified a correlation between high Tac-IPV and poor clinical outcomes; however, this relationship is multifactorial. Influencing factors include the metabolic status of KT patients, the timing of Tac-IPV calculations, and the criteria for defining high and low Tac-IPV thresholds, including the size and selection method. CV, MAD, and TWCV are the metrics that are most frequently used to determine Tac-IPV. Additionally, most of the methods for establishing Tac-IPV thresholds typically employ receiver operating characteristic (ROC) curves and median values. It is also notable that studies examining the clinical significance of Tac-IPV often include tacrolimus levels measured six months after kidney transplantation.

Non-invasive biomarkers of acute rejection in pediatric kidney transplantation: New targets and strategies

Kidney transplantation is the preferred treatment for pediatric end-stage renal disease. However, pediatric recipients face unique challenges due to their prolonged need for kidney function to accommodate growth and development. The continual changes in the immune microenvironment during childhood development and the heightened risk of complications from long-term use of immunosuppressive drugs. The overwhelming majority of children may require more than one kidney transplant in their lifetime. Acute rejection (AR) stands as the primary cause of kidney transplant failure in children. While pathologic biopsy remains the "gold standard" for diagnosing renal rejection, its invasive nature raises concerns regarding potential functional impairment and the psychological impact on children due to repeated procedures. In this review, we outline the current research status of novel biomarkers associated with AR in urine and blood after pediatric kidney transplantation. These biomarkers exhibit superior diagnostic and prognostic performance compared to conventional ones, with the added advantages of being less invasive and highly reproducible for long-term graft monitoring. We also integrate the limitations of these novel biomarkers and propose a refined monitoring model to optimize the management of AR in pediatric kidney transplantation.

Exploratory associations of tacrolimus exposure and clinical outcomes after lung transplantation: A retrospective, single center experience

PURPOSE

This study aimed to investigate the potential impact of tacrolimus (TAC) exposure on clinical outcomes after lung transplantation.

METHODS

This retrospective observational study enrolled a total of 228 lung transplant recipients. TAC trough levels (C0) were collected for 3 intervals: 0-3 months, 3-12 months, and 12-24 months. The intra-patient variability (IPV) was calculated using coefficient of variation. Genotyping of CYP3A5*3 (rs776746) was performed. Patients were further divided into groups based on the C0 cut-off value of 8 ng/mL and IPV cut-off value of 30%. Cox proportional hazards regression models were used to explore the potential impact of C0 and IPV on outcomes of interests, including de-novo donor-specific antibodies (dnDSA), chronic lung allograft dysfunction (CLAD) and mortality.

RESULTS

The influence of CYP3A5*3 polymorphism was only significant for C0 and IPV during the first 3 months. Low C0 (< 8 ng/mL) at 3-12 months increased the risk of dnDSA (hazard ratio [HR] 2.696, 95% confidence interval [CI] 1.046-6.953) and mortality (HR 2.531, 95% CI 1.368-4.685), while High IPV (≥ 30%) during this period was associated with an increased risk of mortality (HR 2.543, 95% CI 1.336-4.839). Patients with Low C0/High IPV combination had significantly higher risks for dnDSA (HR 4.381, 95% CI 1.279-15.008) and survival (HR 6.179, 95% CI 2.598-14.698), surpassing the predictive power provided by C0 or IPV alone.

CONCLUSION

A combination of Low C0/High IPV might be considered in categorizing patients towards risk of adverse clinical outcomes following lung transplantation.

Retrospective analysis on incidence and risk factors of post-transplant diabetes mellitus after lung transplantation and its association with clinical outcomes

BACKGROUND

Post-transplant diabetes mellitus (PTDM) is a common complication after transplantation. We aim to explore potential risk factors of PTDM and its association with outcomes after lung transplantation (LTx).

METHODS

A retrospective study was conducted in 100 patients who underwent LTx at our institution from 2017 to 2021. Patients' information was collected, and genotyping for single nucleotide polymorphisms known to potentially increase the risk of Type 2 DM was performed. Univariate and multivariate analyses were conducted to identify risk factors for PTDM. The primary outcome was the incidence of PTDM. Secondary outcomes were associations between PTDM and clinical outcomes following LTx.

RESULTS

Thirty-nine patients (39.0%) developed PTDM, while 10 patients (25.6%) recovered subsequently. The incidence of PTDM was associated with age > 45 (HR: 2.919, 95% CI [1.021-8.348]), pre-transplant HbA1c > 5.7% (HR: 2.344, 95% CI [1.201-4.573]), KCNJ11 rs5215 (HR: 2.090, 95% CI [1.050-4.162]) and tacrolimus concentration > 8 ng/mL in the first month (HR: 2.090, 95% CI [1.050-4.162]). Patients with PTDM experienced elevated fasting blood glucose levels (FBG) during the first month post-transplantation (p < 0.001), and required a longer duration for FBG to return to normal levels (p < 0.001). However, the presence of PTDM did not significantly impact renal function, incidence of infection episodes, chronic lung allograft dysfunction or mortality following LTx.

CONCLUSION

Advanced age, elevated HbA1c levels, KCNJ11 gene polymorphism, and early exposure to tacrolimus are all significant risk factors for PTDM following LTx. The clinical implications of these factors warrant attention.

Impact of tacrolimus intra-patient variability in adverse outcomes after organ transplantation

Tacrolimus (Tac) is currently the most common calcineurin-inhibitor employed in solid organ transplantation. High intra-patient variability (IPV) of Tac (Tac IPV) has been associated with an increased risk of immune-mediated rejection and poor outcomes after kidney transplantation. Few data are available concerning the impact of high Tac IPV in non-kidney transplants. However, even in kidney transplantation, there is still a controversy whether high Tac IPV is indeed detrimental in respect to graft and/or patient survival. This may be due to different methods employed to evaluate IPV and distinct time frames adopted to assess graft and patient survival in those reports published up to now in the literature. Little is also known about the influence of high Tac IPV in the development of other untoward adverse events, update of the current knowledge regarding the impact of Tac IPV in different outcomes following kidney, liver, heart, lung, and pancreas tran splantation to better evaluate its use in clinical practice.

Kidney transplant from HCV viremic donors to HCV-negative recipients and risk for de novo donor specific antibodies and acute rejection

BACKGROUND

Kidney transplantation from HCV-viremic donors into uninfected recipients is associated with excellent short-term outcomes. However, concerns regarding an increased risk for the development of de novo donor specific antibodies (DSA) and acute rejection have been raised in single center reports.

METHODS

A retrospective study of HCV-negative kidney-only transplant recipients between 2018 and 2020. Patients were grouped based on the donor HCV status into group 1; HCV-viremic donors, and group 2; HCV-negative donors. Inverse probability of treatment weighting (IPTW), with weights derived from the propensity score, were used to estimate the effect of donors' HCV-viremia on the recipients. The primary objective was to compare the 1-year incidence of de novo DSA. Secondary outcomes included group comparison of the incidence of biopsy proven acute rejection (BPAR), 1-year patient and allograft survival, and 1-year renal allograft function.

RESULTS

A total of 71 patients were included in the HCV NAT+ group, and 440 in the HCV- negative group. One-year incidence of de novo DSA was higher in the HCV NAT+ group in the IPTW weighted analysis (19% vs. 9%, p = .02). In the unweighted analysis, BPAR occurred in 7% of recipients in the HCV NAT+ group, compared to 3% in the control group (p = .06). However, due to the low event rate in the in the IPTW weighted groups, a statistical significance test could not be performed. Average estimated GFR was higher in the HCV-viremic group at 3 months (61 vs. 53 ml/min/1.73 m² p = .002), but comparable at 6 (59 vs. 56 ml/min/1.73 m² , p = .31) and 12 months (60 vs. 55 ml/min/1.73 m² , p = .07). Patient and allograft survival were comparable between the two groups.

CONCLUSION

Kidney transplant from HCV-viremic donors was associated with an increased risk for the development of post-transplant de novo DSA in the first year after transplantation, but no difference in patient and graft survival.

DSA in solid organ transplantation: is it a matter of specificity, amount, or functional characteristics?

PURPOSE OF REVIEW

The present review describes the clinical relevance of human leukocyte antigen (HLA) donor-specific antibodies (HLA-DSAs) as biomarkers of alloimmunity and summarizes recent improvements in their characterization that provide insights into immune risk assessment, precision diagnosis, and prognostication in transplantation.

RECENT FINDINGS

Recent studies have addressed the clinical utility of HLA-DSAs as biomarkers for immune risk assessment in pretransplant and peritransplant, diagnosis and treatment evaluation of antibody-mediated rejection, immune monitoring posttransplant, and risk stratification.

SUMMARY

HLA-DSAs have proved to be the most advanced immune biomarkers in solid organ transplantation in terms of analytical validity, clinical validity and clinical utility. Recent studies are integrating multiple HLA-DSA characteristics including antibody specificity, HLA class, quantity, immunoglobulin G subclass, and complement-binding capacity to improve risk assessment peritransplant, diagnosis and treatment evaluation of antibody-mediated rejection, immune monitoring posttransplant, and transplant prognosis evaluation. In addition, integration of HLA-DSAs to clinical, functional and histological transplant parameters has further consolidated the utility of HLA-DSAs as robust biomarkers and allows to build new tools for monitoring, precision diagnosis, and risk stratification for individual patients. However, prospective and randomized-controlled studies addressing the clinical benefit and cost-effectiveness of HLA-DSA-based monitoring and patient management strategies are required to demonstrate that the use of HLA-DSAs as biomarkers can improve current clinical practice and transplant outcomes.