Consensus guidelines on the testing and clinical management issues associated with HLA and non-HLA antibodies in transplantation. Transplantation. 2013;95:19-47. [PMID: 23238534 DOI: 10.1097/tp.0b013e31827a19cc]

Donor-Specific Antibodies Against Donor Human Leukocyte Antigen are Associated with Graft Inflammation but Not with Fibrosis Long-Term After Liver Transplantation: An Analysis of Protocol Biopsies

Background

Donor-specific antibodies (DSA) against donor human leukocyte antigen after liver transplantation, which are associated with histological changes, have been widely studied with respect to their sustained impact on transplant function. However, their long-term impact after liver transplantation remains unclear.

Methods

We performed a cross-sectional analysis from June 2016 to July 2017 that included all patients who presented themselves for scheduled follow-up after receiving a liver transplantation between September 1989 and December 2016. In addition to a liver protocol biopsy, patients were screened for human leukocyte antigen antibodies (HLAab) and donor-specific antibodies. Subsequently, the association between human leukocyte antigen antibodies, donor-specific antibodies, histologic and clinical features, and immunosuppression was analyzed.

Results

Analysis for human leukocyte antigen antibodies and donor-specific antibodies against donor human leukocyte antigen was performed for 291 and 271 patients. A significant association between higher inflammation grades and the presence of human leukocyte antigen antibodies and donor-specific antibodies was detected, while fibrosis stages remained unaffected. These results were confirmed by multivariate logistic regression for inflammation showing a significant increase for presence of human leukocyte antigen antibodies and donor-specific antibodies (OR: 4.43; 95% CI: 1.67–12.6; p=0.0035). Furthermore, the use of everolimus in combination with tacrolimus was significantly associated with the status of negative human leukocyte antigen antibodies and donor-specific antibodies. Viral etiology for liver disease, hepatocellular carcinoma (HCC) and higher steatosis grades of the graft were significantly associated with a lower rate of human leukocyte antigen antibodies. The impact of human leukocyte antigen antibodies and donor-specific antibodies against donor human leukocyte antigen was associated with higher levels of laboratory parameters, such as transaminases and bilirubin.

Conclusion

Donor-specific antibodies against donor human leukocyte antigen are associated with histological and biochemical graft inflammation after liver transplantation, while fibrosis seems to be unaffected. Future studies should validate these findings for longer observation periods and specific subgroups.

A noninvasive diagnostic approach to retrospective donor HLA typing in kidney transplant patients using urine

Antibody-mediated rejection (AMR) is a major obstacle to long-term kidney transplantation. AMR is mostly caused by donor specific HLA antibodies, which can arise before or any time after transplantation. Incomplete donor HLA typing and unavailability of donor DNA regularly preclude the assessment of donor-specificity of circulating anti-HLA antibodies. In our centre, this problem arises in approximately 20% of all post-transplant HLA-antibody assessments. We demonstrate that this diagnostic challenge can be resolved by establishing donor renal tubular cell cultures from recipient´s urine as a source of high-quality donor DNA. DNA was then verified for genetic origin and purity by fluorescence in situ hybridization and short tandem repeat analysis. Two representative cases highlight the diagnostic value of this approach which is corroborated by analysis of ten additional patients. The latter were randomly sampled from routine clinical care patients with available donor DNA as controls. In all 12 cases, we were able to perform full HLA typing of the respective donors confirmed by cross-comparison to results from the stored 10 donor DNAs. We propose that this noninvasive diagnostic approach for HLA typing in kidney transplant patients is valuable to determine donor specificity of HLA antibodies, which is important in clinical assessment of suspected AMR.

Pre-transplant donor-reactive IL-21 producing T cells as a tool to identify an increased risk for acute rejection

Pre-transplant screening focuses on the detection of anti-HLA alloantibodies. Previous studies have shown that IFN-γ and IL-21 producing T cells are associated with the development of acute rejection (AR). The aim of this study, was to assess whether pre-transplant donor-reactive T cells and/or B cells are associated with increased rejection risk. Samples from 114 kidney transplant recipients (transplanted between 2010 and 2013) were obtained pre-transplantation. The number of donor-reactive IFN-γ and IL-21 producing cells was analyzed by ELISPOT assay. The presence of donor specific antibodies (DSA) was also determined before transplantation. Numbers of donor-reactive IFN-γ producing cells were similar in patients with or without AR whereas those of IL-21 producing cells were higher in patients with AR (p = 0.03). Significantly more patients with AR [6/30(20%)] had detectable DSA compared to patients without AR [5/84(5.9%), p = 0.03]. Multivariate logistic regression showed that donor age (OR 1.06), pre-transplant DSA (OR 5.61) and positive IL-21 ELISPOT assay (OR 2.77) were independent predictors of an increased risk for the development of AR. Aside from an advanced donor-age and pre-transplant DSA, also pre-transplant donor-reactive IL-21 producing cells are associated with the development of AR after transplantation.

Improved detection of donor-specific HLA-class II antibody in kidney transplant recipients by modified immunocomplex capture fluorescence analysis

Immunocomplex capture fluorescence analysis (ICFA) which basic principle is same as Luminex crossmatch (LXM), could detect donor-specific HLA antibody (DSA). The advantages of ICFA are (i) detection of DSA and (ii) no requirement of viable cells over the flow cytometry crossmatch (FCXM). However, FCXM has been widely used because of its higher sensitivity than ICFA, in particular HLA-class II antibody detection. In this study the accuracy of DSA detection against HLA-class II was investigated by modifying the original method of ICFA. Increment of the sensitivity was found when purified peripheral blood mononuclear cells (PBMCs) were used instead of whole blood. An ICFA-PBMC in addition to FCXM-T/B was conducted for 118 patients before kidney transplantation and 13 patients with de novo DSA against HLA-class II after transplantation. Significantly positive correlation was observed between the values of ICFA-PBMC and DSA mean fluorescence intensity (MFI) targeting class II (p < 0.0001). When the cutoff level of 1.4 was determined by receiver operating characteristic curve analysis, the average DSA MFI was found to be significantly higher in the ICFA-PBMC (class II) positive group comparing to that in the negative group (12,217 vs 3885, p = 0.0027). ICFA-PBMC and optimized cutoff level could provide valid information in cases of suspected DSA.

Lung Transplantation and the Era of the Sensitized Patient

Long term outcomes in lung transplant are limited by the development of chronic lung allograft dysfunction (CLAD). Within the past several decades, antibody-mediated rejection (AMR) has been recognized as a risk factor for CLAD. The presence of HLA antibodies in lung transplant candidates, "sensitized patients" may predispose patients to AMR, CLAD, and higher mortality after transplant. This review will discuss issues surrounding the sensitized patient, including mechanisms of sensitization, implications within lung transplant, and management strategies.

Antibody-Mediated Rejection and Lung Transplantation

Antibody-mediated rejection (AMR) is now a widely recognized form of lung allograft rejection, with mounting evidence for AMR as an important risk factor for the development of chronic lung allograft dysfunction and markedly decreased long-term survival. Despite the recent development of the consensus diagnostic criteria, it remains a challenging diagnosis of exclusion. Furthermore, even after diagnosis, treatment directed at pulmonary AMR has been nearly exclusively derived from practices with other solid-organ transplants and other areas of medicine, such that there is a significant lack of data regarding the efficacy for these in pulmonary AMR. Lastly, outcomes after AMR remain quite poor despite aggressive treatment. In this review, we revisit the history of AMR in lung transplantation, describe our current understanding of its pathophysiology, discuss the use and limitations of the consensus diagnostic criteria, review current treatment strategies, and summarize long-term outcomes. We conclude with a synopsis of our most pressing gaps in knowledge, introduce recommendations for future directions, and highlight promising areas of active research.

A virtual crossmatch-based strategy for perioperative desensitisation in lung transplant recipients with preformed donor-specific antibodies: 3-year outcome

BACKGROUND

Preformed donor-specific antibodies (DSAs) are associated with worse outcome after lung transplantation (LTx) and migvaht limit access to LTx. A virtual crossmatch (CXM)-based strategy for perioperative desensitisation protocol has been used for immunised LTx candidates since 2012 at Foch hospital. We compared the outcome of desensitised LTx candidates with high DSA mean fluorescence intensity (MFI) and those with low or no preformed DSAs, not desensitised.

METHODS

For all consecutive LTx recipients (January-2012/March-2018), freedom from CLAD and graft survival were assessed by Kaplan-Meier analysis and Cox multivariate analysis.

RESULTS

We compared outcomes for desensitised patients with high preformed DSAs (n=39) and those with no (n=216) or low pre-formed DSAs (n=66). The desensitisation protocol decreased the level of immunodominant DSA (class I/II) at 1, 3, and 6 month post-LTx (p<0.001, p<0.01, p<0.001, respectively). Freedom from CLAD and graft survival at 3 years was similar in the desensitised group as a whole and other groups. Nevertheless, incidence of CLAD was higher with persistent high- than cleared high-level (p=0.044) or no DSAs (p=0.014). Conversely, graft survival was better with cleared high DSAs than persistent high-, low-level, and no pre-formed DSAs (p=0.019, p=0.025, and p=0.044, respectively). On multivariate analysis, graft survival was associated with cleared high DSAs (HR: 0.12 [95%CI: 0.02-0.85] versus no DSAs, p=0.035) and CLAD with persistent DSAs (HR: 3.04 [1.02-9.17] versus no preformed DSAs, p=0.048).

CONCLUSION

The desensitisation protocol in LTx recipients with high preformed DSAs was associated with satisfactory outcome, with cleared high pre-formed DSAs after desensitisation identified as an independent predictor of graft survival.

Presence of donor specific HLA class 2 antibodies (DSA class 2) is associated with development of graft fibrosis more than 10 years after liver transplantation-a retrospective single center study

Here the impact of donor specific human leukocyte antigen (HLA) class 2 antibodies (DSA cl 2) on long term outcome after liver transplantation (LT) was investigated. Altogether 156 (44 pediatric and 112 adult) LT recipients were included in the study. Graft fibrosis was assessed by liver elastography and biopsy. DSA cl 2 were determined by Luminex technology. 46% of LT recipients were positive for DSA cl 2 after a median follow-up of 15 years. In the multivariate analysis DSA cl 2 were significantly associated with immunosuppressive monotherapy (OR 5.42; 95% CI: 1.02-28.90; p = .048). Compared to DSA cl 2 negative patients, positive recipients had significantly more graft fibrosis based on the liver stiffness (mean 9.4 ± 9.0 kPa vs. 6.5 ± 6.3 kPa; p < .002) and fibrosis stages determined by liver elastography (p = .016) and the performed liver biopsies (p = .002). Also, a significantly higher incidence of chronic rejections (11% vs. 2%; p = .045) and graft losses (6% vs. 0%; p = .043) were found. In the multivariate regression analysis DSA cl 2 were significantly associated with graft fibrosis (OR 4.57; 95% CI 1.59-13.10; p = .005). So, these data suggest that development of DSA cl 2 occurs more often with immunosuppressive monotherapy and may ultimately result in chronic rejection and graft fibrosis.

Treatment of donor-specific antibody-mediated rejection after heart transplantation by IgM-enriched human immunoglobulin

Antibody‐mediated graft rejection caused by donor‐specific antibodies (DSA‐MR) remains a serious problem after heart transplantation (HTx). IgM‐enriched human intravenous immunoglobulin (IGM‐IVIG) consists of 76% IgG, 12% IgM, and 12% IgA and provides a new multifactorial approach for DSA‐MR. Between 2017 and 2020, four (P1–4) of 102 patients developed DSA‐MR after HTx in our department and were repetitively treated with IGM‐IVIG in combination with anti‐thymocyte globulin. While in P1 and P4, DSA‐MR occurred within the early post‐operative interval, P2 and P3 developed DSA‐MR approximately 1 year after transplantation. An impairment of ventricular function was observed in three of four patients. Furthermore, P1 and P4 suffered from malign ventricular arrhythmias. After the application of IGM‐IVIG, the ventricular function recovered, and all patients could be discharged from the hospital. As part of a multifactorial therapeutic approach, treatment with IGM‐IVIG seems to be a safe and effective strategy to address DSA‐MR.

Comparative analysis of complement-dependent lymphocytotoxicity crossmatch and flow cytometry crossmatch results versus Luminex single-antigen bead-based donor-specific IgG class I antibody MFI values in live related renal transplant cases; a retrospective observation in 102 cases

The aim of this study was to compare the results of solid phase assay and cell-based assay, and explore the near-accurate DSA-MFI-cutoff value detected on solid phase assay above which the cell-based assay would show a positive result. In this retrospective study, 102 prospective renal transplant recipients were tested for the presence of donor-specific antibodies (DSAs) by cell-based assay (T-cell-CDC-AHG-XM and T-cell-IgG-FC-XM) and solid phase assay (class-I-IgG-L-SAB) with their corresponding donor. Among the 40 patients in the group first (L-SAB-DSA-MFI<1000), one case was positive in IgG-T-cell-FC-XM while T-cell-CDC-AHG-XM was negative in all the cases. In the second group having L-SAB-DSA-MFI values between 1000 and 3000, 19 cases were positive and the remaining 11 cases were negative in IgG-T-cell-FC-XM. T-cell-CDC-AHG-XM showed a negative reaction in all 30 cases. In the third group having L-SAB-DSA-MFI values between 3000 and 5000, IgG-T-cell-FC-XM was positive in 18 cases while, two were negative. T-cell-CDC-AHG-XM demonstrated a negative result in 14 cases while reaming six cases demonstrated a positive result. In the fourth group having L-SAB-DSA-MFI values >5000, all 12 cases showed a positive result in both IgG-T-cell FC-XM and T-cell-CDC-AHG-XM. Our results indicated that the L-SAB-DSA-MFI values >2215 were significantly (P < .001) correlated with positive IgG-T-cell-FC-XM while L-SAB-DSA-MFI values >4689 were significantly (P < .001) correlated with positive CDC-XM.

Autoantibodies to LG3 are associated with poor long-term survival after liver retransplantation

Autoantibodies are detrimental to the survival of organ transplantation. We demonstrated that Angiotensin II Type I Receptor agonistic autoantibodies (AT1R-AA) were associated with poor outcomes after liver retransplantation. To examine the effect of other autoantibodies, we studied a retrospective cohort of 93 patients who received a second liver transplant. Pre-retransplant sera were tested with Luminex-based solid-phase assays. Among 33 tested autoantibodies, 15 were significantly higher in 48 patients who lost their regrafts than 45 patients whose regrafts were still functioning. Specifically, patients with autoantibodies to the C-terminal laminin-like globular domain of Perlecan (LG3) experienced significantly worse regraft survival (p = .002) than those with negative LG3 autoantibodies (LG3-A). In multivariate analysis, LG3-A (HR = 2.35 [1.11-4.98], p = .027) and AT1R-AA (HR = 2.09 [1.07-4.10], p = .032) remained significant predictors of regraft loss after adjusting for recipient age and sex. There were synergistic deleterious effects on regraft survival in patients who were double-positive for LG3-A and donor-specific antibody (DSA) (HR = 5.26 [2.15-12.88], p = .001), or LG3-A and AT1R-AA (HR = 3.23 [1.37-7.66], p = .008). All six double-positive patients lost their liver regrafts. In conclusion, LG3-A is associated with inferior long-term outcomes of a second liver transplant. Screening anti-HLA antibodies and autoantibodies such as LG3-A/AT1R-AA identifies patients with a higher risk for liver transplantation.

Phasing out the pre-transplant cytotoxicity crossmatch: Are we missing something?

Introduction:

The anti-human globulin-enhanced complement-dependent cytotoxicity crossmatch (AHG-CDCXM) assay has been used to assess the presence of donor-specific antibodies (DSA) in recipient’s serum before kidney transplantation. The flow cytometric crossmatch (FCXM) assay was first introduced as an additional test. The aim of this study was to clinically validate the single use of the FCXM assay.

Methods:

This study compared the outcomes of a cohort of kidney transplant patients that underwent FCXM only (FCXM group) versus a cohort of kidney transplant patients that underwent AHG-CDCXM (control group).

Results:

Ninety-seven patients in the FCXM group and 98 controls were included. All crossmatches in the control group were negative. One patient in the FCXM group had a positive B cell crossmatch. One year after transplantation, there were no significant differences in patient survival (p = 0.591) and graft survival (p = 0.692) between the groups. Also, no significant difference was found in the incidence of Banff ≥ 1A acute cellular rejection episodes (p = 0.289). However, acute antibody-mediated rejections occurred in 3 controls (p = 0.028).

Conclusion:

The results showed that discontinuing the AHG-CDCXM assay does not modify the clinical outcomes in a 1-year follow-up.

Biopsy findings after detection of de novo donor-specific antibodies in renal transplant recipients: a single center experience

Background

De novo donor-specific antibodies (DSA) are associated with an increased risk of antibody-mediated rejection and a substantial reduction of allograft survival. We hypothesized that detection of DSA should prompt a biopsy even in the absence of proteinuria and loss of estimated glomerular filtration rate (eGFR). However, data on a population without proteinuria or loss of kidney function is scant, and this is the main novelty of our study design.

Methods

Single center retrospective analysis on biopsy findings after detection of de novo DSA. One-hundred-thirty-two kidney and pancreas-kidney transplant recipients were included. Eighty-four of these patients (63.6%) underwent allograft biopsy. At the time of biopsy n = 50 (59.5%) had a protein/creatinine ratio (PCR) > 300 mg/g creatinine and/or a loss of eGFR ≥ 10 ml/min in the previous 12 months, whereas 40.5% did not. Diagnosis of rejection was performed according to Banff criteria.

Results

Seventy-seven (91.7%) of the biopsies had signs of rejection (47.6% antibody mediated rejection (ABMR), 13.1% cellular, 20.2% combined, 10.7% borderline). Among subjects without proteinuria or loss of eGFR ≥ 10 ml/min/a (n = 34), 29 patients (85.3%) showed signs of rejection (44.1% antibody mediated (ABMR), 14.7% cellular, 11.8% combined, 14.7% borderline).

Conclusion

The majority of subjects with de novo DSA have histological signs of rejection, even in the absence of proteinuria and deterioration of graft function. Thus, it appears reasonable to routinely perform an allograft biopsy after the detection of de novo DSA.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01040-y.

The early impact of preformed angiotensin II type 1 receptor antibodies on graft function in a low immunological risk cohort of kidney transplant recipients

Intruduction and aim: Angiotensin II type 1 receptor antibodies (AT1R-Ab) are associated with graft rejection and poor graft outcomes in kidney transplantation (KT). We aimed to assess the frequency of preformed AT1R-Ab and their impact on graft function and survival at 1 year after KT in a low immunological risk cohort.

METHODS

We performed a prospective, observational cohort study in 67 adult KT recipients, transplanted between 2018 and 2019. A cut-off value >10 U/ml was used for AT1R-Ab detection.

RESULTS

The frequency of preformed AT1R-Ab was 10.4% and the median value of their level was 8.4 U/ml (IQR: 6.8-10.4). Donor-specific anti-human leukocyte antigen antibodies (HLA-DSA) were absent, no case of biopsy-proven rejection was reported and the incidence of graft failure was 7.5%. Estimated glomerular filtration rate (eGFR) was significantly reduced in the AT1R-Ab group [35 (29.8-55.2) vs 56.1 (41.3-66.5) ml/min, p = 0.02] at 1 year after KT. After multivariate linear regression analysis, preformed AT1R-Ab were found as an independent determinant of eGFR at 1 year after KT (β: -15.395; 95% CI: -30.49 - -0.30; p = 0.04). By Cox multivariate regression analysis, preformed AT1R-Ab were not associated with graft failure (HR: 1.36; 95% CI:0.10-14.09; p = 0.80).

CONCLUSION

Preformed AT1R-Ab are an independent determinant of graft function but do not impact graft survival at 12 months after transplantation in a prospective low immunological risk cohort of KT recipients.

Impact of the immunotherapy induction on allograft outcome and survival in kidney transplant patients with donor-specific antibodies to HLA-DQB1

BACKGROUND

The presence of donor-specific antibodies (DSAs) against HLA-DQB1 is considered a significant barrier to good outcome and allograft survival in kidney transplantation (KT). This study aimed to assess the impact of induction immunotherapy on the outcome and allograft survival in KT patients with HLA-DQB1-DSA.

METHODOLOGY

Thirty-two patients who had undergone KT and found to be positive for HLA-DQB1-DSA were monitored at least one to 10 years. They were allocated into two groups of patients: G1 received induction immunotherapy (n = 14 patients; 43.75%), and G2 did not (n = 18 patients; 56.25%).

RESULTS

In G1, 6 (42.86%) patients experienced rejection episodes (RE), 2 (14.29%) due to antibody-mediated rejection (ABMR) and 4 (28.57%) due to T-cell-mediated rejection (TCMR). In G2, 13 (72.22%) patients experienced RE, 3 (16.67%) due to ABMR, and 10 (55.56%) due to TCMR. Graft loss occurred in 4 patients from G1, 2 (14.29%) due to ABMR and 2 (14.29%) due to non-immunological causes. In G2, 9 (50.00%) patients lost their grafts, 2 (11.11%) due to TCMR, 2 (11.11%) due to ABMR, and 5 (27.78%) due to non-immunological causes. The graft survival rate was 64.29% in G1 and 45.83% in G2. Glomerulitis and peritubular capillaritis were observed in 3 and C4d-positive patients with/or without induction who lost their grafts by ABMR by HLA-DQ DSA. Two patients from G2 lost their graft by TCMR due to interstitial lymphocytic infiltrate (i1), foci of mild tubulitis (t2), interstitial edema, moderate interstitial fibrosis and tubular atrophy. Better graft survival rates were shown in patients from G1 who received induction immunotherapy.

CONCLUSION

Our study suggests that patients with an immunological profile of HLA-DQ+ DSA+ treated by immunotherapy induction have a decreased risk of ABMR and increased allograft survival, and the presence of anti-HLA-DQB1 DSA+ detected before and after KT were associated with ABMR episodes and failure.

A Retrospective Study on Human Leukocyte Antigen Types and Haplotypes in a South African Population

CONTEXT.—

Human leukocyte antigen (HLA) is a polymorphic protein of the immune system with a central role in organ transplantation. Organ recipients can be sensitized against HLA from previous exposure, which increases the likelihood of antidonor immune responses and subsequently organ rejection. HLA matching represents an attractive option to improve graft function, reduce sensitization of recipients in first transplantations, and improve organ allocation.

OBJECTIVE.—

To examine the feasibility of the reintroduction of HLA matching into the criteria in the Johannesburg program, we retrospectively assessed HLA types in our donor population.

DESIGN.—

HLA types of 782 deceased and related living donors from 2015 until 2019 were recorded and analyzed to identify the most common HLA types and haplotypes. A virtual crossmatch was also done to examine the anti-HLA antibodies in the recipient population compared with the common HLA types identified in this study.

RESULTS.—

Of the most common HLA types identified, at least 1 was present in 732 (93.6%) of the renal donors assessed. The virtual crossmatch confirmed that most recipients are sensitized against most donors, and this greatly impacts the number of recipients who can receive organ transplants.

CONCLUSIONS.—

This study determined the most common HLA types and haplotypes in a South African organ donor population. This information, combined with the evidence suggesting the immunogenic potential of these common types, the high number of recipients with antibodies against common HLA types, and the ethnic distribution of the donor and recipient populations, informs the recommendation that the pretransplantation workup should not reinclude HLA matching.

Donor-specific antibodies development in renal living-donor receptors: Effect of a single cohort

Minimization in immunosuppression could contribute to the appearance the donor-specific HLA antibodies (DSA) and graft failure. The objective was to compare the incidence of DSA in renal transplantation (RT) in recipients with immunosuppression with and without steroids. A prospective cohort from March 1st, 2013 to March 1st, 2014 and follow-up (1 year), ended in March 2015, was performed in living donor renal transplant (LDRT) recipients with immunosuppression and early steroid withdrawal (ESW) and compared with a control cohort (CC) of patients with steroid-sustained immunosuppression. All patients were negative cross-matched and for DSA pre-transplant. The regression model was used to associate the development of DSA antibodies and acute rejection (AR) in subjects with immunosuppressive regimens with and without steroids. Seventy-seven patients were included (30 ESW and 47 CC). The positivity of DSA class I (13% vs 2%; P < 0.05) and class II (17% vs 4%, P = 0.06) antibodies were higher in ESW versus CC. The ESW tended to predict DSA class II (RR 5.7; CI (0.93–34.5, P = 0.06). T-cell mediated rejection presented in 80% of patients with DSA class I (P = 0.07), and 86% with DSA II (P = 0.03), and was associated with DSA class II, (RR 7.23; CI (1.2–44), P = 0.03). ESW could favor the positivity of DSA. A most strictly monitoring the DSA is necessary for the early stages of the transplant to clarify the relationship between T-cell mediated rejection and DSA.

Urinary C-X-C Motif Chemokine 10 Is Related to Acute Graft Lesions Secondary to T Cell- and Antibody-Mediated Damage

Background

Non-invasive biomarkers of graft rejection are needed to optimize the management and outcomes of kidney transplant recipients. Urinary excretion of IFN-γ-related chemokine CXCL10 is clearly associated with clinical and subclinical T cell-mediated graft inflammation, but its relationship with antibody-mediated damage has not been fully addressed. Further, the variables influencing levels of urinary CXCL10 excretion are unknown.

Material/Methods

A total of 151 kidney graft biopsies (92 surveillance and 59 indication biopsies) and 151 matched urine samples obtained before biopsy were prospectively analyzed. T cell-mediated rejection (TCMR) and antibody-mediated rejection (AbMR) were defined according to the 2017 Banff classification criteria. Urinary CXCL10 levels were measured by ELISA and corrected by urinary creatinine.

Results

Banff scores ‘t’, ‘i’, ‘g’, and ‘ptc’ were significantly related to urinary CXCL10 levels. Multivariate analysis showed that ‘t’ (β=0.107, P=0.001) and ‘ptc’ (β=0.093, P=0.002) were significantly associated with urinary CXCL10. Donor-specific antibodies (DSAs) were related to the high excretion of urinary CXCL10 at 1 year after transplantation (odds ratio [OR] 17.817, P=0.003). Urinary CXCL10 showed good discrimination ability for AbMR (AUC-ROC 0.760, P=0.001). The third tertile of urinary CXCL10 remained significantly associated with AbMR (OR 4.577, 95% confidence interval 1.799–11.646, P=0.001) after multivariate regression analysis.

Conclusions

DSA was the only variable clearly related to high urinary CXCL10 levels. Urinary CXCL10 is a good non-invasive candidate biomarker of AbMR and TCMR, supplying information independent of renal function and other variables normally used to monitor kidney transplants.

Antibodies against HLA cross-reactivity groups: From single antigen bead assay to immunoinformatics interpretation of epitopes

Identification of anti-human leukocyte antigen (HLA) antibodies (Abs) is based on Luminex™ technology. We used bioinformatics to (i) study the correlations of mean fluorescence intensities (MFIs) for all the possible allele pairs, and (ii) determine the degree of epitope homology between HLA antigens. Using MFI data on anti-HLA Abs from 6000 Luminex™ assays, we provide an updated overview of class I and II HLA antigen cross-reactivity in which each node corresponded to an allele and each link corresponded to a strong correlation between two alleles (Spearman's ρ > 0.8). We compared these correlations with the serological groups and the results of an epitope analysis. The strongest correlations concerned allele-specific Abs directed against the same antigen. For the HLA-A locus, the highest values of Spearman's ρ reflected broad specificity. For the HLA-B locus, graphs defined the HLA-Bw4 public epitope, and correlations between HLA-A and -B alleles were only present for beads with the same Bw4 public epitope. For the HLA-C locus, we identified two groups that differed with regard to their KIR ligand subclassification. Lastly, the HLA-DRB1 subgroups were part of a network. In the epitope analysis, Spearman's ρ was related to the number of matched epitopes within pairs of alleles. The combination of Spearman's ρ with simple, undirected graphing constitutes an effective tool for understanding routinely encountered cross-reactivity profiles. Based on this model, we have implemented an online data visualization tool available at http://cusureau.pythonanywhere.com/.

Presence of a survival benefit of HLA-incompatible living donor kidney transplantation compared to waiting or HLA-compatible deceased donor kidney transplantation with a long waiting time

HLA-incompatible living donor kidney transplantation (LDKT) is one of efforts to increase kidney transplantation opportunity for sensitized patients with kidney failure. However, there are conflicting reports for outcomes of HLA-incompatible kidney transplantation compared to patients who wait for HLA-compatible deceased donor kidney transplantation (DDKT) in the United States and United Kingdom. Waiting for an HLA-compatible DDKT is relatively disadvantageous in Korea, because the average waiting time is more than five years. To study this further, we compared outcomes of HLA-incompatible LDKT with those who wait for HLA-compatible DDKT in Korea. One hundred eighty nine patients underwent HLA-incompatible LDKT after desensitization between 2006 and 2018 in two Korean hospitals (42 with a positive complement-dependent cytotoxicity cross-match, 89 with a positive flow cytometric cross-match, and 58 with a positive donor-specific antibody with negative cross-match). The distribution of matched variables was comparable between the HLA-incompatible LDKT group and the matched control groups (waiting-list-only group; and the waiting-list-or-HLA-compatible-DDKT groups; 930 patients each). The HLA-incompatible LDKT group showed a significantly better patient survival rate compared to the waiting-list-only group and the waiting-list-or-HLA-compatible-DDKT groups. Furthermore, the HLA-incompatible LDKT group showed a significant survival benefit as compared with the matched groups at all strength of donor-specific antibodies. Thus, HLA-incompatible LDKT could have a survival benefit as compared with patients who were waitlisted for HLA-compatible DDKT or received HLA-compatible DDKT in Korea. This suggests that HLA-incompatible LDKT as a good option for sensitized patients with kidney failure in countries with prolonged waiting times for DDKT.

Guiding therapeutic plasma exchange for antibody-mediated rejection treatment in lung transplant recipients - a retrospective study

Antibody-Mediated Rejection (AMR) due to donor-specific antibodies (DSA) is associated with poor outcomes after lung transplantation. Currently, there are no guidelines regarding the selection of treatment protocols. We studied how DSA characteristics including titers, C1q, and mean fluorescence intensity (MFI) values in undiluted and diluted sera may predict a response to therapeutic plasma exchange (TPE) and inform patient prognosis after treatment. Among 357 patients consecutively transplanted without detectable pre-existing DSAs between 01/01/16 and 12/31/18, 10 patients were treated with a standardized protocol of five TPE sessions with IVIG. Based on DSA characteristics after treatment, all patients were divided into three groups as responders, partial responders, and nonresponders. Kaplan-Meier Survival analyses showed a statistically significant difference in patient survival between those groups (P = 0.0104). Statistical analyses showed that MFI in pre-TPE 1:16 diluted sera was predictive of a response to standardized protocol (R²  = 0.9182) and patient survival (P = 0.0098). Patients predicted to be nonresponders who underwent treatment with a more aggressive protocol of eight TPE sessions with IVIG and bortezomib showed improvements in treatment response (P = 0.0074) and patient survival (P = 0.0253). Dilutions may guide clinicians as to which patients would be expected to respond to a standards protocol or require more aggressive treatment.

Post-transplant de novo non donor-specific HLA antibodies are not associated with poor graft outcome in non-sensitized pediatric recipients of kidney transplantation

While de novo donor-specific HLA antibodies (dnDSAs) have a detrimental impact on kidney graft outcome, the clinical significance of de novo non donor-specific antibodies (dnNDSAs) is more controversial. We retrospectively evaluated for Ab development and characteristics of dnNDSAs serially collected post-transplant sera and, when available, graft biopsy eluates, from 144 non-sensitized, primary pediatric kidney recipients, consecutively transplanted at a single center between 2003 and 2017, using HLA class I and class II single-antigen flow-bead assays (SAB). The results were compared with clinical-pathologic data from HLA antibody negative and HLA dnDSA-positive patients. Forty-five out of 144 patients developed dnNDSAs (31%). Among the dnNDSA-positive patients, 86% displayed one or more class I/II antibodies recognizing antigens included in the CREG/shared epitope groups that also comprise the mismatched donor HLA antigens. Despite potential pathogenicity, as suggested by their occasional presence within the graft, dnNDSAs displayed significantly lower MFI, and limited complement binding and graft homing properties, when compared with dnDSAs. In parallel, the graft survival probability was significantly lower in patients with dnDSA than in those with dnNDSA or without HLA antibodies (p < 0.005). Indeed, the dnNDSA-positive patients remaining dnDSA-negative throughout the posttransplant period did not develop clinical antibody mediated rejection and graft loss, and maintained good graft function at a median follow-up of 9 years. The biological characteristics of dnNDSAs may account for the low graft damaging capability when compared to dnDSAs.

Does a Useful Test Exist to Properly Evaluate the Pathogenicity of Donor-specific Antibodies? Lessons From a Comprehensive Analysis in a Well-studied Single-center Kidney Transplant Cohort

BACKGROUND

Donor-specific antibodies (DSA) play a major role in antibody-mediated rejection (AMR) and graft dysfunction. However, the clinical relevance of complement-binding anti-HLA antibodies remains unclear.

METHODS

Here, we analyzed DSA detected in the serum (sDSA) using single antigen bead, C1q, and C3d assays combined with the study of intragraft DSA (gDSA) in 86 patients who had DSA and underwent a kidney biopsy for cause (n = 58) or without evidence of kidney dysfunction (n = 28). DSA characteristics were collected and related to the presence of AMR, graft histological features, and allograft survival.

RESULTS

Forty-five patients (52%) had C1q DSA, and 42 (51%) had C3d DSA. Allograft biopsies revealed AMR in 63 cases (73%), regardless of kidney function. gDSA were identified in 74% of biopsies. We observed a strong correlation among single antigen bead mean fluorescence intensity and complement assays positivity, presence of gDSA, and AMR occurrence.

CONCLUSIONS

Complement-binding DSA per se were not significantly associated with allograft survival in the entire study sample. Finally, gDSA predicted subsequent graft loss in patients who showed a stable renal function at the day of biopsy. Our data suggest that DSA mean fluorescence intensity and presence of gDSA might provide prognostic information during posttransplant monitoring.

KDIGO Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation

The 2020 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation is intended to assist health care professionals worldwide who evaluate and manage potential candidates for deceased or living donor kidney transplantation. This guideline addresses general candidacy issues such as access to transplantation, patient demographic and health status factors, and immunological and psychosocial assessment. The roles of various risk factors and comorbid conditions governing an individual's suitability for transplantation such as adherence, tobacco use, diabetes, obesity, perioperative issues, causes of kidney failure, infections, malignancy, pulmonary disease, cardiac and peripheral arterial disease, neurologic disease, gastrointestinal and liver disease, hematologic disease, and bone and mineral disorder are also addressed. This guideline provides recommendations for evaluation of individual aspects of a candidate's profile such that each risk factor and comorbidity are considered separately. The goal is to assist the clinical team to assimilate all data relevant to an individual, consider this within their local health context, and make an overall judgment on candidacy for transplantation. The guideline development process followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. Guideline recommendations are primarily based on systematic reviews of relevant studies and our assessment of the quality of that evidence, and the strengths of recommendations are provided. Limitations of the evidence are discussed with differences from previous guidelines noted and suggestions for future research are also provided.

A Changing Paradigm in Heart Transplantation: An Integrative Approach for Invasive and Non-Invasive Allograft Rejection Monitoring

Cardiac allograft rejection following heart transplantation is challenging to diagnose. Tissue biopsies are the gold standard in monitoring the different types of rejection. The last decade has seen an increased emphasis on identifying non-invasive methods to improve rejection diagnosis and overcome tissue biopsy invasiveness. Liquid biopsy, as an efficient non-invasive diagnostic and prognostic oncological monitoring tool, seems to be applicable in heart transplant follow-ups. Moreover, molecular techniques applied on blood can be translated to tissue samples to provide novel perspectives on tissue and reveal new diagnostic and prognostic biomarkers. This review aims to provide a comprehensive overview of the state-of-the-art of the new methodologies in cardiac allograft rejection monitoring and investigate the future perspectives on invasive and non-invasive rejection biomarkers identification. We reviewed literature from the most used scientific databases, such as PubMed, Google Scholar, and Scopus. We extracted 192 papers and, after a selection and exclusion process, we included in the review 81 papers. The described limitations notwithstanding, this review show how molecular biology techniques and omics science could be deployed complementarily to the histopathological rejection diagnosis on tissue biopsies, thus representing an integrated approach for heart transplant patients monitoring.

Impact of Subclinical Borderline Inflammation on Kidney Transplant Outcomes

Supplemental Digital Content is available in the text.

Background.

Surveillance biopsies permit early detection of subclinical inflammation before clinical dysfunction, but the impact of detecting early subclinical phenotypes remains unclear.

Methods.

We conducted a single-center retrospective cohort study of 441 consecutive kidney transplant recipients between 2015 and 2018 with surveillance biopsies at 6 months post-transplant. We tested the hypothesis that early subclinical inflammation (subclinical borderline changes, T cell-mediated rejection, or microvascular injury) is associated with increased incidence of a composite endpoint including acute rejection and allograft failure.

Results.

Using contemporaneous Banff criteria, we detected subclinical inflammation in 31%, with the majority (75%) having a subclinical borderline phenotype (at least minimal inflammation with mild tubulitis [>i0t1]). Overall, subclinical inflammation was independently associated with the composite endpoint (adjusted hazard ratio, 2.88; 1.11-7.51; P = 0.03). The subgroup with subclinical borderline inflammation, predominantly those meeting the Banff 2019 i1t1 threshold, was independently associated with 5-fold increased hazard for the composite endpoint (P = 0.02). Those with concurrent subclinical inflammation and subclinical chronic allograft injury had worse outcomes. The effect of treating subclinical inflammation was difficult to ascertain in small heterogeneous subgroups.

Conclusions.

Subclinical acute and chronic inflammation are common at 6 months post-transplant in kidney recipients with stable allograft function. The subclinical borderline phenotype with both tubulitis and interstitial inflammation was independently associated with poor long-term outcomes. Further studies are needed to elucidate the role of surveillance biopsies for management of allograft inflammation in kidney transplantation.

Endothelin A Receptors Expressed in Glomeruli of Renal Transplant Patients May Be Associated with Antibody-Mediated Rejection

BACKGROUND

Non-human leukocyte antigen (HLA) anti-endothelin A receptor antibodies are presented as being potentially important, but the expression of the endothelin A receptor in glomeruli (ETA receptor (g+)) has not yet been described. We decided to evaluate the presence and relevance of the ETA receptor in for-cause renal transplant biopsies. The aim of our study was to evaluate the immunoreactivity of the ETA receptor and its significance in patients who underwent a renal transplant biopsy due to the deterioration of transplant function, with detailed characterization of staining in glomeruli.

METHODS

The immunohistochemical expression of ETA receptor (ETAR) was analyzed in renal transplant biopsies. Microscopic evaluation was performed on paraffin sections in glomeruli. The analysis was performed using a two-step scale (0: lack of ETAR expression; 1: the presence of ETAR expression-mild to moderate immunoreactivity).

RESULTS

We analyzed 149 patients who underwent renal allograft biopsy after renal transplantation. Positive staining of ETA receptors in glomeruli (ETA receptor (g+)) was noticed in 13/149 (8.7%) patients. Five of these 13 (38.5%) patients with ETA receptor (g+) developed antibody-mediated rejection (AMR), while 13 of the remaining 136 (9.5%) ETA receptor (g-) patients developed AMR (p = 0.0022). Graft loss was noticed in all but one ETA receptor (g+) patient with AMR (4/5; 80%), but only in 2/13 (15%) ETA receptor (g-) patients with AMR (p = 0.009) during the first year after biopsy.

CONCLUSIONS

The expression of endothelin A receptors in glomeruli seems to be a potentially important feature in the diagnosis of damage during antibody-mediated rejection. It may help to identify patients at a higher risk of allograft rejection and injury.

Eplet-based virtual PRA increases transplant probability in highly-sensitized patients

BACKGROUND

The reduced access of highly-sensitized (HS) patients to kidney transplantation (KTx) is one of the major challenges for transplant community. Therefore, the aim of our study was to estimate the impact of three different vPRA calculations, assessed traditionally and using eplet-based analysis, in donor offers.

METHODS

At 01-01-2020, 157 HS patients are waitlisted for deceased donor KTx and were included in this study. Total vPRA (vPRAt) was calculated considering all patient allosensitization history, using 1 k MFI cut-off. Current vPRA (vPRAc) refers only to the last year SAB assays, using 1 k MFI cut-off. For eplet vPRA (vPRAe) every SAB assay was analyzed by HLAMatchmaker and HLAfusion software. Matching runs have been performed taking vPRA calculation as unacceptable antigens (UAs).

RESULTS

All patients had at least one previous sensitizing event and patients with 100% vPRA were predominantly candidates for retransplantation (P < 0.001), had higher PRA-CDC (P < 0.001), and longer dialysis vintage waiting time (P < 0.001). Inter-group movement analysis between vPRA measures showed that 70 (45%), 124 (79%) and 80 (51%) patients were reclassified to a lower group when considering vPRAt to vPRAc, vPRAt to vPRAe and vPRAc to vPRAe, respectively. The median percentage of change in estimated number of match runs needed for 95% probability of finding an acceptable donor was significantly more pronounced by increasing vPRAt intervals, when considering the reclassification from vPRAt to vPRAe (P < 0.001) or vPRAc to vPRAe (P = 0.045), while from vPRAt to vPRAc it was not (P = 0.899).

CONCLUSIONS

Our study demonstrated that the use of total or current vPRA calculations are impairing HS patients, by decreasing transplant probability, leading to dramatically longer waiting times, when compared to eplet based vPRA.

Donor-Derived Cell-Free DNA in Kidney Transplantation as a Potential Rejection Biomarker: A Systematic Literature Review

Kidney transplantation (KTx) is the best treatment method for end-stage kidney disease. KTx improves the patient's quality of life and prolongs their survival time; however, not all patients benefit fully from the transplantation procedure. For some patients, a problem is the premature loss of graft function due to immunological or non-immunological factors. Circulating cell-free DNA (cfDNA) is degraded deoxyribonucleic acid fragments that are released into the blood and other body fluids. Donor-derived cell-free DNA (dd-cfDNA) is cfDNA that is exogenous to the patient and comes from a transplanted organ. As opposed to an invasive biopsy, dd-cfDNA can be detected by a non-invasive analysis of a sample. The increase in dd-cfDNA concentration occurs even before the creatinine level starts rising, which may enable early diagnosis of transplant injury and adequate treatment to avoid premature graft loss. In this paper, we summarise the latest promising results related to cfDNA in transplant patients.

Bias in Medicine: Lessons Learned and Mitigation Strategies

Cognitive bias consists of systematic errors in thinking due to human processing limitations or inappropriate mental models. Cognitive bias occurs when intuitive thinking is used to reach conclusions about information rather than analytic (mindful) thinking. Scientific progress is delayed when bias influences the dissemination of new scientific knowledge, as it has with the role of human leucocyte antigen antibodies and antibody-mediated rejection in cardiac transplantation. Mitigating strategies can be successful but involve concerted action by investigators, peer reviewers, and editors to consider how we think as well as what we think.

De Novo Donor Specific Antibody and Long-Term Outcome After Liver Transplantation: A Systematic Review and Meta-Analysis

Background

The impact of de novo anti-HLA donor-specific alloantibodies (DSA) which develop after long-term liver transplantation (LT) remains controversial and unclear. The aim of this study was to investigate the role of de novo DSAs on the outcome in LT.

Methods

We did a systematic review and meta-analysis of observational studies published until Dec 31, 2019, that reported de novo DSA outcome data (≥1 year of follow-up) after liver transplant. A literature search in the MEDLINE/PubMed, EMBASE, Cochrane Library, Scopus and Web of Science Core Collection databases was performed.

Results

Of 5,325 studies identified, 15 fulfilled our inclusion criteria. The studies which reported 2016 liver transplant recipients with de novo DSAs showed an increased complication risk, i.e. graft loss and chronic rejection (OR 3.61; 95% CI 1.94-6.71, P < 0.001; I2 58.19%), and allograft rejection alone (OR 6.43; 95% CI: 3.17-13.04; P < 0.001; I2 49.77%); they were compared to patients without de novo DSAs. The association between de novo DSAs and overall outcome failure was consistent across all subgroups and sensitivity analysis.

Conclusions

Our study suggested that de novo DSAs had a significant deleterious impact on the liver transplant risk of rejection. The routine detection of de novo DSAs may be beneficial as noninvasive biomarker-guided risk stratification.

Screening strategy for de novo donor-specific HLA antibodies beyond the first year after kidney transplantation: Personalized or "one size fits all"?

Screening for de novo donor-specific HLA antibodies (DSAs) after kidney transplantation is widely recommended. The aim of this single-center, cross-sectional study was to investigate the frequency of therapeutic interventions triggered by de novo DSA screening. We included 464 patients screened for de novo DSA at annual visits after a median of 5 years post-transplant (range 1 to 19 years). Overall, de novo DSAs were detected in 55/464 patients (11.9%) with a stepwise increase of the prevalence from 4.9% at 1 year post-transplant to 18.9% at >10 years post-transplant. Subsequent allograft biopsies were performed in 24/55 patients (44%). The main reasons to omit biopsies were good/stable allograft function and anticipated lack of clinical consequences (eg, relevant comorbidities). Rejection processes were detected in 16/24 biopsies (67%). Therapeutic interventions were made in 18/464 screened patients (3.9%) with a significantly higher rate in the youngest quartile of patients (≤48 years; 7.9%) compared to the middle 50% (49-67 years; 3%) and the oldest quartile (≥68 years; 1.7%) (P = .03). Our study suggests that the frequency of therapeutic interventions triggered by de novo DSA screening after kidney transplantation is overall low, but significantly higher in younger patients, arguing for a personalized, age-adapted de novo DSA screening strategy.

Safety and Efficacy of a Steroid Avoidance Immunosuppression Regimen in Renal Transplant Patients With De Novo or Preformed Donor-Specific Antibodies: A Single-Center Study

Although interest in the role of donor-specific antibodies (DSAs) in kidney transplant rejection, graft survival, and histopathological outcomes is increasing, their impact on steroid avoidance or minimization in renal transplant populations is poorly understood. Primary outcomes of graft survival, rejection, and histopathological findings were assessed in 188 patients who received transplants between 2012 and 2015 at the Scripps Center for Organ Transplantation, which follows a steroid avoidance protocol. Analyses were performed using data from the United Network for Organ Sharing. Cohorts included kidney transplant recipients with de novo DSAs (dnDSAs; n = 27), preformed DSAs (pfDSAs; n = 15), and no DSAs (nDSAs; n = 146). Median time to dnDSA development (classes I and II) was shorter (102 days) than in previous studies. Rejection of any type was associated with DSAs to class I HLA (P < .05) and class II HLA (P < .01) but not with graft loss. Although mean fluorescence intensity (MFI) independently showed no association with rejection, an MFI >5000 showed a trend toward more antibody-mediated rejection (P < .06), though graft loss was not independently associated. Banff chronic allograft nephropathy scores and a modified chronic injury score were increased in the dnDSA cohort at 6 months, but not at 2 years (P < .001 and P < .08, respectively). Our data suggest that dnDSAs and pfDSAs impact short-term rejection rates but do not negatively impact graft survival or histopathological outcomes at 2 years. Periodic protocol post-transplant DSA monitoring may preemptively identify patients who develop dnDSAs who are at a higher risk for rejection.

Experience of the first 6 years of pediatric kidney transplantation in Indonesia: A multicenter retrospective study

BACKGROUND

Pediatric kidney transplantation was only introduced in Indonesia in 2013. We therefore aimed to assess the characteristics and outcomes of transplants performed from its inception to January 2019.

METHOD

The study had a dual-center retrospective design. We examined the records of kidney transplant recipients and then calculated patient and graft survival rates by Kaplan-Meier survival analysis with 95% confidence intervals (95% CI).

RESULTS

In total, 12 kidney transplantations were performed in eleven children during the study period; among these, ten were boys, and nine had renal failure caused by congenital anomaly of the kidney or urinary tract. All donors were living, and all recipients were on dialysis at the time of transplantation, when their median age was 14.5 years (range, 8-19 years). Three patients died of infection in the first year of follow-up and two lost their allograft by the time of their last follow-up (median, 13 months; range, 4-69 months). The 1-year patient survival rate was therefore 68.18% (95% CI, 29.72%-88.61%), which remained unchanged at 3 and 5 years. However, the non-death-censored graft survival rates at 1, 3, and 5 years were 68.18% (95% CI, 29.72%-88.61%), 51.14% (95% CI, 14.5%-79.46%), and 25.57% (95% CI, 1.38%-64.78%), respectively.

CONCLUSION

Patient and graft survival rates after pediatric kidney transplantation in Indonesia are lower than those reported in other countries. Closer patient follow-up and stricter adherence to guidelines could improve transplant outcomes, but we must seek to improve the balance between infection and rejection.

Noninvasive biomarkers for prediction and diagnosis of heart transplantation rejection

For most patients with end-stage heart failure, heart transplantation is the treatment of choice. Allograft rejection is one of the major post-transplantation complications affecting graft outcome and survival. Recent advancements in science and technology offer an opportunity to integrate genomic and other omics-based biomarkers into clinical practice, facilitating noninvasive evaluation of allograft for diagnostic and prognostic purposes. Omics, including gene expression profiling (GEP) of blood immune cell components and donor-derived cell-free DNA (dd-cfDNA) are of special interest to researchers. Several studies have investigated levels of dd-cfDNA and miroRNAs in blood as potential markers for early detection of allograft rejection. One of the achievements in the field of transcriptomics is AlloMap, GEP of peripheral blood mononuclear cells (PBMC), which can identify 11 differentially expressed genes and help with detection of moderate and severe acute cellular rejection in stable heart transplant recipients. In recent years, the utilization of GEP of PBMC for identifying differentially expressed genes to diagnose acute antibody-mediated rejection and cardiac allograft vasculopathy has yielded promising results. Advancements in the field of metabolomics and proteomics as well as their potential implications have been further discussed in this paper.

HLA antibodies are associated with deterioration of kidney allograft function irrespective of donor specificity

BACKGROUND

Donor-specific antibodies are associated with high immunological risk and poor allograft outcome. Risk and clinical relevance of non-donor-specific HLA antibodies is less clear.

METHODS

A retrospective single-center study was conducted in all patients receiving a first kidney transplant at the University hospital of Zürich between 01/2006 and 02/2015. Patients were stratified into 3 groups having either no HLA antibodies at all (NoAB), HLA antibodies with donor specificity (DSA) and HLA antibodies without donor specificity (NonDSA). Allograft outcome was assessed using the slope of the estimated glomerular filtration rate (eGFR slope) starting at 12 months after transplantation.

RESULTS

During a median follow-up of 1808 days HLA antibodies were detected in 106 of 238 eligible patients (44%). Out of these, 73 patients (69%) had DSA and 33 patients (31%) had NonDSA only. Medium-term allograft function, as determined by eGFR slope over three years, improved in patients with NoAB (months 12-48: +0.7 ml/min/1.73 m²) but deteriorated significantly in patients with both DSA (months 12-48: -1.5 ml/min per1.73 m²/year, p = 0.015) and NonDSA (months 12-48: -1.8 ml/min per1.73 m²/year, p = 0.03) as compared to the group with NoAB.

CONCLUSION

Both, donor-specific and non-donor-specific HLA antibodies are associated with medium-term kidney allograft dysfunction as compared to patients with no HLA antibodies.

Donor-specific antibodies in liver transplantation: challenges in diagnosis and determining clinical impact

PURPOSE OF REVIEW

Our understanding of the clinical impact of donor-specific antibodies in liver transplant recipients has evolved in recent years as outcomes for liver allografts have improved and advances in diagnostic testing have made recognition of antibody mediated rejection in transplant patients more sensitive.

RECENT FINDINGS

Two main types of donor-specific antibodies - preformed and de novo - have been reported in the literature to have a negative impact on graft survival, and researchers have been able to further identify subclasses of class II donor-specific antibodies as being the most clinically impactful. Furthermore, there is evidence that donor-specific antibody formation can augment cellular rejection in liver grafts and lead to worsened clinical outcomes. Recent data have shown a higher prevalence of donor-specific antibody formation than previously reported.

SUMMARY

This review explores the most recent literature regarding the clinical impact of both preformed and de-novo donor-specific antibodies and potential management guidelines for patients undergoing liver transplantation. The best practice guidelines for undergoing monitoring for donor-specific antibody formation and protocol biopsies in sensitized patients will depend on further multiinstitutional studies.

A Virtual Crossmatch-based Strategy Facilitates Sharing of Deceased Donor Kidneys for Highly Sensitized Recipients

BACKGROUND

It is estimated that 19.2% of kidneys exported for candidates with >98% calculated panel reactive antibodies are transplanted into unintended recipients, most commonly due to positive physical crossmatch (PXM). We describe the application of a virtual crossmatch (VXM) that has resulted in a very low rate of transplantation into unintended recipients.

METHODS

We performed a retrospective review of kidneys imported to our center to assess the reasons driving late reallocation based on the type of pretransplant crossmatch used for the intended recipient.

RESULTS

From December 2014 to October 2017, 254 kidneys were imported based on our assessment of a VXM. Of these, 215 (84.6%) were transplanted without a pretransplant PXM. The remaining 39 (15.4%) recipients required a PXM on admission using a new sample because they did not have an HLA antibody test within the preceding 3 months or because they had a recent blood transfusion. A total of 93% of the imported kidneys were transplanted into intended recipients. There were 18 late reallocations: 9 (3.5%) due to identification of a new recipient medical problem upon admission, 5 (2%) due to suboptimal organ quality on arrival, and only 4 (1.6%) due to a positive PXM or HLA antibody concern. A total of 42% of the recipients of imported kidneys had a 100% calculated panel reactive antibodies. There were no hyperacute rejections and very infrequent acute rejection in the first year suggesting no evidence for immunologic memory response.

CONCLUSIONS

Seamless sharing is within reach, even when kidneys are shipped long distances for highly sensitized recipients. Late reallocations can be almost entirely avoided with a strategy that relies heavily on VXM.

Discovery of non-HLA antibodies associated with cardiac allograft rejection and development and validation of a non-HLA antigen multiplex panel: From bench to bedside

We analyzed humoral immune responses to nonhuman leukocyte antigen (HLA) after cardiac transplantation to identify antibodies associated with allograft rejection. Protein microarray identified 366 non-HLA antibodies (>1.5 fold, P < .5) from a discovery cohort of HLA antibody-negative, endothelial cell crossmatch-positive sera obtained from 12 cardiac allograft recipients at the time of biopsy-proven rejection. From these, 19 plasma membrane proteins and 10 autoantigens identified from gene ontology analysis were combined with 48 proteins identified through literature search to generate a multiplex bead array. Longitudinal sera from a multicenter cohort of adult cardiac allograft recipients (samples: n = 477 no rejection; n = 69 rejection) identified 18 non-HLA antibodies associated with rejection (P < .1) including 4 newly identified non-HLA antigenic targets (DEXI, EMCN, LPHN1, and SSB). CART analysis showed 5/18 non-HLA antibodies distinguished rejection vs nonrejection. Antibodies to 4/18 non-HLA antigens synergize with HLA donor-specific antibodies and significantly increase the odds of rejection (P < .1). The non-HLA panel was validated using an independent adult cardiac transplant cohort (n = 21 no rejection; n = 42 rejection, >1R) with an area under the curve of 0.87 (P < .05) with 92.86% sensitivity and 66.67% specificity. We conclude that multiplex bead array assessment of non-HLA antibodies identifies cardiac transplant recipients at risk of rejection.

Clinical Outcomes of Lung Transplantation in the Presence of Donor-Specific Antibodies

Rationale: There is significant variation in approach to pre-lung transplant donor-specific antibodies (DSA), with some centers declining to cross any DSA. We implemented a protocol for transplantation for candidates with pretransplant DSA so long as a prospective complement-dependent cytotoxicity crossmatch was negative, regardless of number, specificity, class, or mean fluorescence intensity.Objectives: To compare post-transplant outcomes including overall survival, chronic lung allograft dysfunction-free survival, antibody-mediated rejection, and acute cellular rejection in lung transplant recipients where pretransplant DSA was and was not present.Methods: This was a single-center retrospective cohort study. For recipients with pretransplant DSA, if the prospective complement-dependent cytotoxicity crossmatch was negative, the donor offer was accepted and plasmapheresis was performed within 24 hours of transplantation and continued until retrospective crossmatch results returned. Immunosuppression and post-transplant management were not otherwise modified.Results: Of the 203 included recipients, 18 (8.9%) had pretransplant DSA. The median DSA mean fluorescence intensity was 4,000 (interquartile range, 2,975-5,625; total range, 2,100-17,000). The median number of DSA present per patient was one (interquartile range, 1-2). The presence of pretransplant DSA was not associated with increased mortality (hazard ratio, 1.2; 95% confidence interval [CI], 0.4-3.4) or decreased chronic lung allograft dysfunction-free survival (hazard ratio, 1.1; 95% CI, 0.6-2.1). Recipients with pretransplant DSA were more likely to require prolonged mechanical ventilation (adjusted odds ratio, 7.0; 95% CI, 2.3-21.6) and to have antibody-mediated rejection requiring treatment (adjusted odds ratio, 7.5; 95% CI, 1.0-55.8).Conclusions: A protocol of accepting donor offers for lung transplant candidates with preformed, complement-dependent cytotoxicity crossmatch-negative DSA is associated with increased need for prolonged mechanical ventilation and antibody-mediated rejection without affecting short-term overall or chronic lung allograft dysfunction-free survival.

Human Leukocyte Antigen Examination Using Luminex®-Based Assays for Donor-Recipient Compatibility Assessment in Kidney Transplantation: Our Preliminary Experience

Background: Detection of anti-HLA antibodies (HLAabs) in organ transplantation recipients is vital to determine whether the recipient has specific HLAabs against the donor’s HLA molecules (donor-specific anti-HLA antibodies [DSA]). Methods: This preliminary study involved seven subjects: five without prior HLA sensitization and two with a history of possible HLA sensitization (kidney transplantation and pregnancy). Two of the subjects were siblings, two of the subjects were mother and son, and two of them were first cousins once removed. All the subjects underwent HLA typing, and four of the subjects underwent HLAabs assays using the sequence-specific oligonucleotide probes (SSOP) method. Results: There were 10/16 HLA matches between subjects who were siblings and between subjects who were mother and son, and 6/16 HLA matches were found between subjects who were first cousins once removed. Subjects with previous kidney transplantation developed 59 HLA-Abs toward class I and class II HLA (the mean fluorescence intensity (MFI) value range: 1,003.36 to 12,404.77). HLAabs were also found among subjects without prior HLA sensitization, albeit with relatively lower MFI values. Conclusions: HLA typing and HLAabs detection for donor-recipient compatibility assessment using the SSOP method offers more detailed, semi-quantitative results. Further research involving larger subjects in cohort settings will be useful for profiling MFI cut-off values for HLAabs.

Donor-specific antibody characteristics, including persistence and complement-binding capacity, increase risk for chronic lung allograft dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the major complication limiting long-term survival in lung transplant recipients (LTRs), with those developing donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) previously found to have increased risk for CLAD. However, as DSA responses vary in timing of development, specificity, breadth, persistence, and complement-binding capacity, we hypothesized that these characteristics would impact CLAD and survival outcomes.

METHODS

We retrospectively analyzed DSA characteristics and outcomes in a single-center cohort of 582 LTRs who had serum samples collected prospectively from 2010 to 2016. Luminex-based single antigen bead assays were performed to assess DSA.

RESULTS

DSAs were detected in 247 LTRs (42%), of which 124 (21.3%) were de novo DSAs and 53 (9.1%) were complement-binding (C1q+). CLAD developed in 208 LTRs (35.7%) during the follow-up period, with 67.8% determined as bronchiolitis obliterans syndrome phenotype and 32.2% as restrictive allograft syndrome phenotype. We found a shorter time to CLAD in LTRs with persistent DSAs (p = 0.04) and HLA-DQ-specific DSAs (p = 0.03). LTRs who developed C1q+ DSAs had significantly shorter time to CLAD (p < 0.001), with 100% of C1q+ DSAs being persistent and no differences between CLAD phenotypes. CLAD-free survival was significantly reduced in LTRs who developed C1q+ DSAs (p = 0.001), HLA-DQ-specific DSAs (p = 0.03), and multiple DSAs (p = 0.02).

CONCLUSIONS

Together, our findings demonstrate that DSA characteristics of persistence, HLA-DQ specificity, and C1q+ DSAs are associated with shorter time to CLAD. Additionally, C1q+, HLA-DQ-specific, and multiple DSAs are associated with decreased CLAD-free survival. These characteristics may improve DSA risk stratification for deleterious outcomes in LTRs.

Non-invasive cardiac allograft rejection surveillance: reliability and clinical value for prevention of heart failure

Allograft rejection-related acute and chronic heart failure (HF) is a major cause of death in heart transplant recipients. Given the deleterious impact of late recognized acute rejection (AR) or non-recognized asymptomatic antibody-mediated rejection on short- and long-term allograft function improvement of AR surveillance and optimization of action strategies for confirmed AR can prevent AR-related allograft failure and delay the development of cardiac allograft vasculopathy, which is the major cause for HF after the first posttransplant year. Routine non-invasive monitoring of cardiac function can improve both detection and functional severity grading of AR. It can also be helpful in guiding the anti-AR therapy and timing of routine surveillance endomyocardial biopsies (EMBs). The combined use of EMBs with non-invasive technologies and methods, which allow detection of subclinical alterations in myocardial function (e.g., tissue Doppler imaging and speckle-tracking echocardiography), reveal alloimmune activation (e.g., screening of complement-activating donor-specific antibodies and circulating donor-derived cell-free DNA) and help in predicting the imminent risk of immune-mediated injury (e.g., gene expression profiling, screening of non-HLA antibodies, and circulating donor-derived cell-free DNA), can ensure the best possible surveillance and management of AR. This article gives an overview of the current knowledge about the reliability and clinical value of non-invasive cardiac allograft AR surveillance. Particular attention is focused on the potential usefulness of non-invasive tools and techniques for detection and functional grading of early and late ARs in asymptomatic patients. Overall, the review aimed to provide a theoretical and practical basis for those engaged in this particularly demanding up-to-date topic.

Immunological follow-up of patients with renal transplants: A proposal for clinical practice in Colombia

Graft damage is a process that starts at the moment of transplantation, due to comorbidities of receptor, donor status, ischemia time, ischemia-reperfusion phenomenon, among others, those induce metabolic and immune factors that ultimately trigger clinical manifestations of graft dysfunction. However, the preclinical progression between the time of transplantation and the appearance of signs and symptoms of graft damage can take weeks to years. Therefore, the implementation of rational monitoring approaches during the post-transplantation period is critical and should include not only the clinical follow-up but also anticipate immunological graft damage. In the present essay, we propose an immunological monitoring algorithm for the post-renal transplantation period.

The Graz Liver Allocation Strategy-Impact of Extended Criteria Grafts on Outcome Considering Immunological Aspects

Background: Transplant centers are forced to use livers of extended criteria donors for transplantation due to a dramatic organ shortage. The outcome effect of extended donor criteria (EDCs) remains unclear. Thus, this study was designed to assess the impact of EDCs on outcome including immunological aspects after liver transplantation (LT).

Patients and Methods: Between November 2016 and March 2018, 49 patients (85.7% male) with a mean age of 57 ± 11 years underwent LT. The impact of EDCs on outcome after LT was assessed retrospectively using both MedOcs and ENIS (Eurotransplant Network Information System).

Results: About 80% of grafts derived from extended criteria donors. Alanine aminotransferase/aspartate aminotransferase (AST/ALT) levels elevated more than three times above normal values in organ donors was the only significant risk factor for primary dysfunction (PDF) and primary non-function (PNF)/Re-LT and early non-anastomotic biliary strictures (NAS). Balance of risk (BAR) score did not differ between EDC and non-EDC recipients. PDF (14.3% of all patients) and PNF (6.1% of all patients) occurred in 23.1% of EDC-graft recipients and in 10.0% of non-EDC-graft recipients (RR 2.31, p = 0.663). The 90-day mortality was 3.6%. There was no difference of early non-anastomotic biliary tract complications and biopsy proven rejections (BPR). There was no correlation of PDF/PNF with BPR and NAS, respectively; however, 66.7% of the patients with BPR also developed early NAS (p < 0.001).

Conclusion: With the Graz liver allocation strategy, excellent survival can be achieved selecting livers with no more than 2 not outcome-relevant EDCs for patients with MELD >20. Further, BPR is associated with biliary complications.