Integrative Omics Analysis Unravels Microvascular Inflammation-Related Pathways in Kidney Allograft Biopsies.

In solid-organ transplantation, microRNAs (miRNAs) have emerged as key players in the regulation of allograft cells function in response to injury. To gain insight into the role of miRNAs in antibody-mediated rejection, a rejection phenotype histologically defined by microvascular inflammation, kidney allograft biopsies were subjected to miRNA but also messenger RNA (mRNA) profiling. Using a unique multistep selection process specific to the BIOMARGIN study (discovery cohort, N=86; selection cohort, N=99; validation cohort, N=298), six differentially expressed miRNAs were consistently identified: miR-139-5p (down) and miR-142-3p/150-5p/155-5p/222-3p/223-3p (up). Their expression level gradually correlated with microvascular inflammation intensity. The cell specificity of miRNAs target genes was investigated by integrating their in vivo mRNA targets with single-cell RNA sequencing from an independent allograft biopsy cohort. Endothelial-derived miR-139-5p expression correlated negatively with MHC-related genes expression. Conversely, epithelial-derived miR-222-3p overexpression was strongly associated with degraded renal electrolyte homeostasis and repressed immune-related pathways. In immune cells, miR-150-5p regulated NF-κB activation in T lymphocytes whereas miR-155-5p regulated mRNA splicing in antigen-presenting cells. Altogether, integrated omics enabled us to unravel new pathways involved in microvascular inflammation and suggests that metabolism modifications in tubular epithelial cells occur as a consequence of antibody-mediated rejection, beyond the nearby endothelial compartment.

CRISPR/Cas9-Engineered HLA-Deleted Glomerular Endothelial Cells as a Tool to Predict Pathogenic Non-HLA Antibodies in Kidney Transplant Recipients.

BACKGROUND: After kidney transplantation, donor-specific antibodies against human leukocyte antigen donor-specific antibodies (HLA-DSAs) drive antibody-mediated rejection (ABMR) and are associated with poor transplant outcomes. However, ABMR histology (ABMRh) is increasingly reported in kidney transplant recipients (KTRs) without HLA-DSAs, highlighting the emerging role of non-HLA antibodies (Abs). METHODS: W e designed a non-HLA Ab detection immunoassay (NHADIA) using HLA class I and II-deficient glomerular endothelial cells (CiGEnCΔHLA) that had been previously generated through CRISPR/Cas9-induced B2M and CIITA gene disruption. Flow cytometry assessed the reactivity to non-HLA antigens of pretransplantation serum samples from 389 consecutive KTRs. The intensity of the signal observed with the NHADIA was associated with post-transplant graft histology assessed in 951 adequate biopsy specimens. RESULTS: W e sequentially applied CRISPR/Cas9 to delete the B2M and CIITA genes to obtain a CiGEnCΔHLA clone. CiGEnCΔHLA cells remained indistinguishable from the parental cell line, CiGEnC, in terms of morphology and phenotype. Previous transplantation was the main determinant of the pretransplantation NHADIA result (P<0.001). Stratification of 3-month allograft biopsy specimens (n=298) according to pretransplantation NHADIA tertiles demonstrated that higher levels of non-HLA Abs positively correlated with increased glomerulitis (P=0.002), microvascular inflammation (P=0.003), and ABMRh (P=0.03). A pretransplantation NHADIA threshold of 1.87 strongly discriminated the KTRs with the highest risk of ABMRh (P=0.005, log-rank test). A multivariate Cox model confirmed that NHADIA status and HLA-DSAs were independent, yet synergistic, predictors of ABMRh. CONCLUSION: The NHADIA identifies non-HLA Abs and strongly predicts graft endothelial injury independent of HLA-DSAs.

Deciphering the Prognostic and Predictive Value of Urinary CXCL10 in Kidney Recipients With BK Virus Reactivation.

BK virus (BKV) replication increases urinary chemokine C-X-C motif ligand 10 (uCXCL10) levels in kidney transplant recipients (KTRs). Here, we investigated uCXCL10 levels across different stages of BKV replication as a prognostic and predictive marker for functional decline in KTRs after BKV-DNAemia. uCXCL10 was assessed in a cross-sectional study (474 paired urine/blood/biopsy samples and a longitudinal study (1,184 samples from 60 KTRs with BKV-DNAemia). uCXCL10 levels gradually increased with urine (P-value < 0.0001) and blood BKV viral load (P < 0.05) but were similar in the viruria and no BKV groups (P > 0.99). In viremic patients, uCXCL10 at biopsy was associated with graft functional decline [HR = 1.65, 95% CI (1.08-2.51), P = 0.02], irrespective of baseline eGFR, blood viral load, or BKVN diagnosis. uCXL10/cr (threshold: 12.86 ng/mmol) discriminated patients with a low risk of graft function decline from high-risk patients (P = 0.01). In the longitudinal study, the uCXCL10 and BKV-DNAemia trajectories were superimposable. Stratification using the same uCXCL10/cr threshold at first viremia predicted the subsequent inflammatory response, assessed by time-adjusted uCXCL10/cr AUC (P < 0.001), and graft functional decline (P = 0.03). In KTRs, uCXCL10 increases in BKV-DNAemia but not in isolated viruria. uCXCL10/cr is a prognostic biomarker of eGFR decrease, and a 12.86 ng/ml threshold predicts higher inflammatory burdens and poor renal outcomes.

No clinical benefit of rapid versus gradual tapering of immunosuppression to treat sustained BK virus viremia after kidney transplantation: a single-center experience.

Immunosuppressive drug tapering is currently the recommended treatment of BK virus (BKV) viremia after kidney transplantation; however, its exact modalities remain unclear. We retrospectively compared two consecutive strategies in 111 patients with sustained viremia: a gradual monitoring/tapering group (GT, n = 57) before 2012 and a rapid monitoring/tapering group (RT, n = 54) after 2012. At viremia diagnosis, the dose of mycophenolic acid (MPA) and tacrolimus levels (T0 ) were similar among patient groups. However, following onset, the dose of MPA at 1 month (P = 0.002) and 3 months (P = 0.005) and Tac T0 at 1 month (P = 0.030) and 3 months (P = 0.006) were lower in the RT group. This rapid minimization shortened BKV viremia (P < 0.001) and resulted in a better protection of graft function in patients with confirmed BKV-associated nephropathy (P = 0.033) without impacting 5-year graft survival. Survival without rejection was similar (P = 0.571), but the RT group had increased the development of de novo donor-specific antibodies (dnDSAs; P < 0.001). Multivariate Cox analysis identified basiliximab versus Thymoglobulin® induction [hazard ratio (HR), 3.090; P = 0.001] and the RT strategy (HR, 6.021; P = 0.002) as independently associated with dnDSAs. Compared to a gradual tapering, rapid immunosuppression tapering to treat sustained BKV viremia does not improve medium-term clinical outcome but increases the risk of developing dnDSAs.

Urinary C-X-C Motif Chemokine 10 Independently Improves the Noninvasive Diagnosis of Antibody-Mediated Kidney Allograft Rejection.

Urinary levels of C-X-C motif chemokine 9 (CXCL9) and CXCL10 can noninvasively diagnose T cell-mediated rejection (TCMR) of renal allografts. However, performance of these molecules as diagnostic/prognostic markers of antibody-mediated rejection (ABMR) is unknown. We investigated urinary CXCL9 and CXCL10 levels in a highly sensitized cohort of 244 renal allograft recipients (67 with preformed donor-specific antibodies [DSAs]) with 281 indication biopsy samples. We assessed the benefit of adding these biomarkers to conventional models for diagnosing/prognosing ABMR. Urinary CXCL9 and CXCL10 levels, normalized to urine creatinine (Cr) levels (CXCL9:Cr and CXCL10:Cr) or not, correlated with the extent of tubulointerstitial (i+t score; all P<0.001) and microvascular (g+ptc score; all P<0.001) inflammation. CXCL10:Cr diagnosed TCMR (area under the curve [AUC]=0.80; 95% confidence interval [95% CI], 0.68 to 0.92; P<0.001) and ABMR (AUC=0.76; 95% CI, 0.69 to 0.82; P<0.001) with high accuracy, even in the absence of tubulointerstitial inflammation (AUC=0.70; 95% CI, 0.61 to 0.79; P<0.001). Although mean fluorescence intensity of the immunodominant DSA diagnosed ABMR (AUC=0.75; 95% CI, 0.68 to 0.82; P<0.001), combining urinary CXCL10:Cr with immunodominant DSA levels improved the diagnosis of ABMR (AUC=0.83; 95% CI, 0.77 to 0.89; P<0.001). At the time of ABMR, urinary CXCL10:Cr ratio was independently associated with an increased risk of graft loss. In conclusion, urinary CXCL10:Cr ratio associates with tubulointerstitial and microvascular inflammation of the renal allograft. Combining the urinary CXCL10:Cr ratio with DSA monitoring significantly improves the noninvasive diagnosis of ABMR and the stratification of patients at high risk for graft loss.