The Accuracy of Sequence-Specific Oligonucleotide and Real-Time Polymerase Chain Reaction HLA Typing in Determining the Presence of Pre-Transplant Donor-Specific Anti-HLA Antibodies and Total Eplet Mismatches for Deceased Donor Kidney Transplantation.

High resolution human leukocyte antigen (HLA) typing is important in establishing eplet compatibility and the specificity of donor-specific anti-HLA antibodies (DSA). In deceased donor kidney transplantation, high resolution donor HLA typing may not be immediately available, leading to inaccuracies during the organ allocation process. We aimed to determine the concordance and agreement of HLA-Class I and II eplet mismatches calculated using population frequency based allelic haplotype association (linkage disequilibrium, LD) from sequence-specific oligonucleotide (SSO) and real-time polymerase chain reaction (rtPCR) donor HLA typing (available at time of donor kidney allocation) compared to high-resolution Next Generation Sequencing (NGS) donor typing. NGS high resolution HLA typing were available for all recipients prior to donor kidney allocation. A cohort of 94 deceased donor-recipient pairs from a single Western Australian center were included (77 individual donors typed, 55 local and 22 interstate). The number of class I (HLA-A+B+C) and class II (HLA-DRB1+DRB3/4/5+DQB1+DQA1+DPB1+DPA1) eplet mismatches were calculated using HLAMatchmaker, comparing LD- and NGS-HLA typing. The accuracy in assigning pre-transplant DSA was compared between methods. The concordance correlation coefficient (95%CI) for HLA-class I and II eplet mismatches were 0.994 (0.992 to 0.996) and 0.991 (0.986 to 0.993), respectively. The 95% limits of agreement for class I were -1.3 (-1.6 to -1.1) to 1.4 (1.2 to 1.7) and -4.8 (-5.7 to -3.9) to 5.0 (4.1 to 5.9) for Class II. Disagreement between the two methods were present for 11 and 37 of the Class I and II donor/recipient pairs. Of which, 5 had a difference of ≥5 class II eplet mismatches. There were 34 (36%) recipients with potential pre-transplant DSA, of which 8 (24% of recipients with DSA) had indeterminate and ultimately false positive DSA assigned by donor LD-typing. While the concordance between NGS- and LD-typing was high, the limits of agreement suggest meaningful differences between these two techniques. The inaccurate assignment of DSA from donor LD-typing may result in associated HLA being considered unacceptable mismatches, inappropriately precluding candidates' access to transplantation. Accurate imputation of two-field HLA alleles based on LD from SSO and rtPCR HLA typing remains a substantial challenge in clinical practice in-lieu of widely available, rapid, high-resolution methods.

Improve in-depth immunological risk assessment to optimize genetic-compatibility and clinical outcomes in child and adolescent recipients of parental donor kidney transplants: protocol for the INCEPTION study.

BACKGROUND: Parental donor kidney transplantation is the most common treatment option for children and adolescents with kidney failure. Emerging data from observational studies have reported improved short- and medium-term allograft outcomes in recipients of paternal compared to maternal donors. The INCEPTION study aims to identify potential differences in immunological compatibility between maternal and paternal donor kidneys and ascertain how this affects kidney allograft outcomes in children and adolescents with kidney failure. METHODS: This longitudinal observational study will recruit kidney transplant recipients aged ≤18 years who have received a parental donor kidney transplant across 4 countries (Australia, New Zealand, United Kingdom and the Netherlands) between 1990 and 2020. High resolution human leukocyte antigen (HLA) typing of both recipients and corresponding parental donors will be undertaken, to provide an in-depth assessment of immunological compatibility. The primary outcome is a composite of de novo donor-specific anti-HLA antibody (DSA), biopsy-proven acute rejection or allograft loss up to 60-months post-transplantation. Secondary outcomes are de novo DSA, biopsy-proven acute rejection, acute or chronic antibody mediated rejection or Chronic Allograft Damage Index (CADI) score of > 1 on allograft biopsy post-transplant, allograft function, proteinuria and allograft loss. Using principal component analysis and Cox proportional hazards regression modelling, we will determine the associations between defined sets of immunological and clinical parameters that may identify risk stratification for the primary and secondary outcome measures among young people accepting a parental donor kidney for transplantation. This study design will allow us to specifically investigate the relative importance of accepting a maternal compared to paternal donor, for families deciding on the best option for donation. DISCUSSION: The INCEPTION study findings will explore potentially differential immunological risks of maternal and paternal donor kidneys for transplantation among children and adolescents. Our study will provide the evidence base underpinning the selection of parental donor in order to achieve the best projected long-term kidney transplant and overall health outcomes for children and adolescents, a recognized vulnerable population. TRIAL REGISTRATION: The INCEPTION study has been registered with the Australian New Zealand Clinical Trials Registry, with the trial registration number of ACTRN12620000911998 (14th September 2020).

The association between human leukocyte antigen eplet mismatches, de novo donor-specific antibodies, and the risk of acute rejection in pediatric kidney transplant recipients.

BACKGROUND: The longitudinal relationship between HLA class I and II eplet mismatches, de novo donor-specific antibodies (dnDSA) development, and acute rejection after transplantation in childhood is unknown. METHODS: Eplet mismatches at HLA class I and II loci were calculated retrospectively for each donor/recipient pair transplanted between 2005 and 2015 at a single Australian center. Logistic regression analyses were conducted to determine the association between the number of eplet mismatches, dnDSA, and acute rejection. RESULTS: The cohort comprised 59 children (aged 0-18 years) who received their first kidney allograft and were followed for median (interquartile range) 4.5 (± 2.6) years. Overall, 32% (19/59) developed dnDSA (class I 3% (2/59), class II 14% (8/59), 15% class I and II (9/59)), and 24% (14/59) developed biopsy-proven acute rejection. Every unit increase in class I and II eplet mismatches corresponded to an increase in risk of class I (odds ratio (OR) 1.22, 95% CI 1.07-1.39, p < 0.01) and class II (OR 1.06, 95% CI 1.01-1.11, p = 0.02) dnDSA development. Compared with recipients without dnDSA, class I and II dnDSA were associated with direction of effect towards increased risk of acute cellular rejection (class I: OR 5.87, 95% CI 0.99-34.94, p = 0.05; class II: OR 12.00, 95% CI 1.25-115.36, p = 0.03) and acute antibody-mediated rejection (class I: OR 25.67, 95% CI 3.54-186.10, p < 0.01; class II: OR 9.71, 95% CI 1.64-57.72, p = 0.01). CONCLUSIONS: Increasing numbers of HLA class I or II eplet mismatches were associated with the development of dnDSA. Children who developed dnDSA were also more likely to develop acute rejection compared with children without dnDSA.

Association between Aortic Calcification, Cardiovascular Events, and Mortality in Kidney and Pancreas-Kidney Transplant Recipients.

BACKGROUND: Cardiovascular (CV) disease is the leading cause of death in kidney and simultaneous pancreas-kidney (SPK) transplant recipients. Assessing abdominal aortic calcification (AAC), using lateral spine x-rays and the Kaupilla 24-point AAC (0-24) score, may identify transplant recipients at higher CV risk. METHODS: Between the years 2000 and 2015, 413 kidney and 213 SPK first transplant recipients were scored for AAC at time of transplant and then followed for CV events (coronary heart, cerebrovascular, or peripheral vascular disease), graft-loss, and all-cause mortality. RESULTS: The mean age was 44 ± 12 years (SD) with 275 (44%) having AAC (26% moderate: 1-7 and 18% high: ≥8). After a median of 65 months (IQR 29-107 months), 46 recipients experienced CV events, 59 died, and 80 suffered graft loss. For each point increase in AAC, the unadjusted hazard ratios (HR) for CV events and mortality were 1.11 (95% CI 1.07-1.15) and 1.11 (1.08-1.15). These were similar after adjusting for age, gender, smoking, transplant type, dialysis vintage, and diabetes: aHR 1.07 (95% CI 1.02-1.12) and 1.09 (1.04-1.13). For recipients with high versus no AAC, the unadjusted and fully-adjusted HRs for CV events were 5.90 (2.90-12.02) and 3.51 (1.54-8.00), for deaths 5.39 (3.00-9.68) and 3.38 (1.71-6.70), and for graft loss 1.30 (0.75-2.28) and 1.94 (1.04-3.27) in age and smoking history-adjusted analyses. CONCLUSION: Kidney and SPK transplant recipients with high AAC have 3-fold higher CV and mortality risk and poorer graft outcomes than recipients without AAC. AAC scoring may be useful in assessing and targeted risk-lowering strategies.

Epitope matching in kidney transplantation: recent advances and current limitations.

PURPOSE OF REVIEW: Evolution of human leukocyte antigen (HLA) molecular typing techniques has progressively enabled more accurate determination of the three-dimensional building blocks that form the antibody accessibility and binding sites of each HLA allele. These immunogenic HLA regions known as epitopes are composed of polymorphic sequences of amino acid residues termed eplets. This review provides a critical appraisal of the current understanding of epitope compatibility in kidney transplantation. RECENT FINDINGS: There is a tendency to suggest that epitope matching is likely to be superior to broad antigen HLA matching such that the allocation of donor kidneys to patients with a more favorable epitope compatibility profile may lead to better allograft outcomes. A growing body of work has highlighted the association between a greater number of eplet mismatches and adverse allograft outcomes, and approaches using eplet matching have been successfully implemented in organ allocation programs. However, our understanding of epitope compatibility remains in its infancy, requiring further and more in-depth evaluation. Critically, it remains unclear how best to translate findings derived at the population level to the care of individual patients. Questions that need to be answered include a lack of consensus in the definition and interpretation of epitope compatibility, are class I and II compatibility of similar clinical importance, how best to define predetermined mismatch thresholds for utilization in organ allocation, and whether other properties such as differences in electrostatic potential between donor and recipient HLA alleles are also important in determining immunological compatibility. SUMMARY: Epitope matching likely represents a valid progression in understanding donor-recipient HLA compatibility. However, more clinical data and a better understanding about differences in methods to determine epitope compatibility are required before the approach can be widely applied in clinical practice.

The clinical and pathological significance of borderline T cell-mediated rejection.

The pathological diagnosis of borderline rejection (BL-R) denotes possible T cell-mediated rejection (TCMR), but its clinical significance is uncertain. This single-center, cross-sectional cohort study compared the functional and histological outcomes of consecutive BL-R diagnoses (n = 146) against normal controls (n = 826) and acute TCMR (n = 55) from 551 renal transplant recipients. BL-R was associated with the following: contemporaneous renal dysfunction, acute tubular necrosis, and chronic tubular atrophy (P < .001); progressive tubular injury with fibrosis by longitudinal sequential histology (45.3% at 1 year); increased subsequent acute rejection (39.4%), allograft failure (P < .001), and patient mortality (P = .007). BL-R detected by biopsy indicated for impaired function was followed by suboptimal functional recovery (46.3%), persistent inflammation (27.2%), and acute rejection episodes (50.0%) despite antirejection treatment in 83.3%. By 1 year after BL-R, the incidence of new-onset microvascular inflammation (9.3%), C4d staining (22.3%), transplant glomerulopathy (13.3%), and de novo donor-specific antibodies (31.5%) exceeded normal controls (P < .05-.001). BL-R inflammation in protocol biopsy persisted in 28.0% and progressed to acute rejection in 32.6%; however, it resolved in 61.6% of the untreated cases. In summary, BL-R is a heterogeneous diagnostic grouping, ranging from mild inconsequential inflammation to clinically significant TCMR, which is capable of immune-mediated tubular injury resulting in inferior functional, immunological, and histological consequences.