Isolated v-lesion represents a benign phenotype of vascular rejection of the kidney allograft - a retrospective study

Automated Urinary Chemokine Assays for Noninvasive Detection of Kidney Transplant Rejection: A Prospective Cohort Study

RATIONALE & OBJECTIVE

Prior studies have demonstrated the diagnostic potential of urinary chemokines C-X-C motif ligand 9 (CXCL9) and CXCL10 for kidney transplant rejection. However, their benefit in addition to clinical information has not been demonstrated. We evaluated the diagnostic performance for detecting acute rejection of urinary CXCL9 and CXCL10 when integrated with clinical information.

STUDY DESIGN

Single-center prospective cohort study.

SETTING & PARTICIPANTS

We analyzed 1,559 biopsy-paired urinary samples from 622 kidney transplants performed between April 2013 and July 2019 at a single transplant center in Belgium. External validation was performed in 986 biopsy-paired urinary samples.

TESTS COMPARED

We quantified urinary CXCL9 (uCXCL9) and CXCL10 (uCXCL10) using an automated immunoassay platform and normalized the values to urinary creatinine. Urinary chemokines were incorporated into a multivariable model with routine clinical markers (estimated glomerular filtration rate, donor-specific antibodies, and polyoma viremia) (integrated model). This model was then compared with the tissue diagnosis according to the Banff classification for acute rejection.

OUTCOME

Acute rejection detected on kidney biopsy using the Banff classification.

RESULTS

Chemokines integrated with routine clinical markers had high diagnostic value for detection of acute rejection (n=150) (receiver operating characteristic area under the curve 81.3% [95% CI, 77.6-85.0]). The integrated model would help avoid 59 protocol biopsies per 100 patients when the risk for rejection is predicted to be below 10%. The performance of the integrated model was similar in the external validation cohort.

LIMITATIONS

The cross-sectional nature obviates investigating the evolution over time and prediction of future rejection.

CONCLUSIONS

The use of an integrated model of urinary chemokines and clinical markers for noninvasive monitoring of rejection could enable a reduction in the number of biopsies. Urinary chemokines may be useful noninvasive biomarkers whose use should be further studied in prospective randomized trials to clarify their role in guiding clinical care and the use of biopsies to detect rejection after kidney transplantation.

PLAIN-LANGUAGE SUMMARY

Urinary chemokines CXCL9 and CXCL10 have been suggested to be good noninvasive biomarkers of kidney transplant rejection. However, defining a context of use and integration with clinical information is necessary before clinical implementation can begin. In this study, we demonstrated that urinary chemokines CXCL9 and CXCL10, together with clinical information, have substantial diagnostic accuracy for the detection of acute kidney transplant rejection. Application of urinary chemokines together with clinical information may guide biopsy practices following kidney transplantation and potentially reduce the need for kidney transplant biopsies.

Seeking Standardized Definitions for HLA-incompatible Kidney Transplants: A Systematic Review

BACKGROUND

There is no standard definition for "HLA incompatible" transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes.

METHODS

We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility.

RESULTS

Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains.

CONCLUSIONS

Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

The Pathological and Clinical Diversity of Acute Vascular Rejection in Kidney Transplantation

BACKGROUND

Vascular rejection (VR) is characterized by arteritis, steroid resistance, and increased graft loss but is poorly described using modern diagnostics.

METHODS

We screened 3715 consecutive biopsies and retrospectively evaluated clinical and histological phenotypes of VR (n = 100) against rejection without arteritis (v0REJ, n = 540) and normal controls (n = 1108).

RESULTS

Biopsy sample size affected the likelihood of arterial sampling, VR diagnosis, and final Banff v scores (P < 0.001). Local v and cv scores were greatest in larger arteries (n = 258). VR comprised 15.6% of all rejection episodes, presented earlier (median 1.0 mo, interquartile range, 0.4-8 mo) with higher serum creatinine levels and inferior graft survival, versus v0REJ (P < 0.001). Early VR (≤1 mo) was common (54%) and predicted by sensitization, delayed function, and prior corticosteroid use, with associated acute dysfunction and optimal therapeutic response, independent of Banff v score. Late VR followed under-immunosuppression in 71.4% (noncompliance 38.8%, iatrogenic 32.6%), and was associated with chronic interstitial fibrosis, incomplete renal functional recovery and persistent inflammation using sequential histopathology. The etiology was "pure" antibody-mediated VR (n = 21), mixed VR (n = 36), and "pure" T cell-mediated VR (n = 43). Isolated VR (n = 34, Banff i < 1 without tubulitis) comprised 24 T cell-mediated VR and 10 antibody-mediated VR, presenting with mild renal dysfunction, minimal Banff acute scores, and better graft survival compared with inflamed VR. Interstitial inflammation influenced acute renal dysfunction and early treatment response, whereas chronic tubulointerstitial damage determined long-term graft loss.

CONCLUSIONS

VR is a heterogenous entity influenced by time-of-onset, pathophysiology, accompanying interstitial inflammation and fibrosis. Adequate histological sampling is essential for its accurate diagnostic classification and treatment.

Adipose tissue macrophages and atherogenesis – a synergy with cholesterolaemia

Antibody-mediated rejection (ABMR) is a major obstacle to the long-term success in kidney transplantation. Diagnosis of ABMR is determined according to the internationally recognized Banff criteria. However, a significant proportion of patients does not meet all the defined criteria, and the outcome of such cases remains poorly understood. The histology of ABMR frequently lacks sensitivity and specificity. More importantly, mixed forms of ABMR and T cell-mediated rejection as well as findings of nonspecific injury are common in clinical settings. Donor-specific anti-HLA antibodies (DSA) are detectable only in half of the ABMR cases by histology. Prognostic role of non-HLA antibodies against various endothelial proteins has been discussed. Antibody independent NK cell activation reflecting killer-cells’ inhibitory receptor incompatibility is suggested in microvascular inflammation in DSA negative patients. Molecular assessment of ABMR has been prioritized to overcome high interobserver variability and improve diagnostics in mixed forms of rejections and in DSA negative cases. Finally, donor-derived cell-free DNA detected in a recipient’s peripheral blood sample has been proposed as a noninvasive marker for diagnosis of graft rejection, and thus might serve as a liquid biopsy in the near future. Despite all achievements, diagnosing ABMR in kidney allografts remains to be a challenge in a significant number of cases.

Intimal Arteritis and Microvascular Inflammation Are Associated With Inferior Kidney Graft Outcome, Regardless of Donor-Specific Antibodies

Background: The prognostic role of intimal arteritis of kidney allografts in donor-specific antibody negative (DSA–) antibody-mediated rejection (ABMR) remains unclear.

Methods: Seventy-two out of 881 patients who had undergone kidney transplantation from 2014 to 2017 exhibited intimal arteritis in biopsies performed during the first 12 months. In 26 DSA negative cases, the intimal arteritis was accompanied by tubulointerstitial inflammation as part of T cell-mediated vascular rejection (TCMRV, N = 26); intimal arteritis along with microvascular inflammation occurred in 29 DSA negative (ABMRV/DSA–) and 19 DSA positive cases (ABMRV, DSA+, N = 17). In 60 (83%) patients with intimal arteritis, the surveillance biopsies after antirejection therapy were performed. Hundred and two patients with non-vascular ABMR with DSA (ABMR/DSA+, N = 55) and without DSA (ABMR/DSA–, N = 47) served as controls. Time to transplant glomerulopathy (TG) and graft failure were the study endpoints.

Results: Transplant glomerulopathy -free survival at 36 months was 100% in TCMRV, 85% in ABMR/DSA–, 65% in ABMRV/DSA-, 54% in ABMR/DSA+ and 31% in ABMRV/DSA+ (log rank p < 0.001). Death-censored graft survival at 36 months was 98% in ABMR/DSA-, 96% in TCMRV, 86% in ABMRV/DSA–, 79% in ABMR/DSA+, and 64% in ABMRV/DSA+ group (log rank p = 0.001). In surveillance biopsies, the resolution of rejection was found in 19 (90%) TCMRV, 14 (58%) ABMRV/DSA–, and only 4 (27%) ABMRV/DSA+ patients (p = 0.006). In the multivariable model, intimal arteritis as part of ABMR represented a significant risk for TG development (HR 2.1, 95% CI 1.2–3.8; p = 0.012) regardless of DSA status but not for graft failure at 36 months.

Conclusions: Intimal arteritis as part of ABMR represented a risk for early development of TG regardless of the presence or absence of DSA. Intimal arteritis in DSA positive ABMR represented the high-risk phenotype.

Early isolated V-lesion may not truly represent rejection of the kidney allograft

Intimal arteritis is known to be a negative prognostic factor for kidney allograft survival. Isolated v-lesion (IV) is defined as intimal arteritis with minimal tubulointerstitial inflammation (TI). Although the Banff classification assesses IV as T cell-mediated rejection (TCMR), clinical, and prognostic significance of early IV (early IV, eIV) with negative C4d and donor-specific antibodies (DSA) remains unclear. To help resolve if such eIV truly represents acute rejection, a molecular study was performed. The transcriptome of eIV (n=6), T cell-mediated vascular rejection with rich TI (T cell-mediated vascular rejection, TCMRV, n=4) and non-rejection histologic findings (n=8) was compared using microarrays. A total of 310 genes were identified to be deregulated in TCMRV compared with eIV. Gene enrichment analysis categorized deregulated genes to be associated primarily with T-cells associated biological processes involved in an innate and adaptive immune and inflammatory response. Comparison of deregulated gene lists between the study groups and controls showed only a 1.7% gene overlap. Unsupervised hierarchical cluster analysis revealed clear distinction of eIV from TCMRV and showed similarity with a control group. Up-regulation of immune response genes in TCMRV was validated using RT-qPCR in a different set of eIV (n=12) and TCMRV (n=8) samples. The transcriptome of early IV (< 1 month) with negative C4d and DSA is associated with a weak immune signature compared with TCMRV and shows similarity with normal findings. Such eIV may feature non-rejection origin and reflect an injury distinct from an alloimmune response. The present study supports use of molecular methods when interpreting kidney allograft biopsy findings.