Molecular signatures of chronic antibody-mediated rejection in human liver transplants

Abstract

AbstractBackground&AimsThe role of antibody-mediated rejection (ABMR) after liver transplantation (LT) remains controversial. Chronic ABMR (cABMR) is often subclinical and potentially missed without surveillance biopsies (svLbx) which are not established in most LT centers. Transcriptome analysis previously characterized molecular changes in T cell-mediated rejection (TCMR) after solid organ transplantation. We aimed to identify molecular cABMR signatures after LT for a more comprehensive understanding of cABMR.MethodsWe retrospectively identified indication and svLbx from our prospective institutional biorepository (n=1207 over 12 years). We performed RNA-sequencing on liver biopsies (discovery cohort: n=71; validation cohort: n=58). Downstream analyses explored the unique and common molecular features of cABMR, clinical (clinTCMR) and subclinical TCMR (subTCMR) compared to no histological rejection (NHR).ResultsNineteen percent of LT recipients with donor-specific antibodies had cABMR. Eighty-one percent of patients with cABMR had ALT and AST ≤2x the upper limit of normal, only being recognized by svLbx. The cABMR group displayed differentially expressed genes (DEGs) uniquely enriched in fibrogenesis-, complement activation- and TNFα-signaling-related pathways. ClinTCMR showed DEGs uniquely enriched in antigen presentation-, interferon-signaling-, and T cell receptor-signaling-related pathways. Common cABMR and clinTCMR DEGs were enriched in chemokine-signaling- and cytokine response-related pathways. Gene set enrichment scores of interferon-signaling and extracellular matrix remodeling pathways discriminated cABMR and clinTCMR. Molecular signatures of clinTCMR correlated with histological TCMR-patterns. Molecular cABMR-signatures correlated with lobular graft injury and liver fibrosis scores. The validation cohort consistently showed patterns of DEGs associating cABMR with fibrogenesis- and NF-κB-signaling-related pathways and clinTCMR with interferon-signaling- and adaptive immunity-related pathways. SubTCMR was molecularly almost indistinguishable from NHR.ConclusionsWe report transcriptome-unique features of cABMR that is a unique molecular identity associated with inflammation and fibrogenesis.Impact and Implications– Antibody-mediated rejection (ABMR) is a recognized relevant cause of graft injury and unfavorable patient outcomes after kidney, heart and lung transplantation but the role of ABMR after liver transplantation (LT) remains controversial. Hence, we aimed to characterize chronic ABMR after LT on a molecular basis to identify unique features.– Our findings highlight chronic ABMR to be a distinct clinical phenotype of rejection after LT. Furthermore, we demonstrate chronic ABMR to present mostly with normal liver enzymes, therefore only being detected if protocol biopsies are performed for graft monitoring.– Therefore, our work emphasizes the usage of protocol graft biopsies for the detection of a fibrosis associated phenotype of cABMR. Pending external validation, the molecular signature may be used in the future to discriminate cABMR from graft injury of other causes.Graphical AbstractHighlights– Chronic ABMR was present in up to 1/5 of DSA-positive biopsies and 1/5 of biopsies with advanced fibrosis– Chronic ABMR and clinically overt TCMR have largely distinct transcriptome patterns with common up-regulated DEGs enriched in pro-inflammatory pathways– Clinical TCMR is characterized by up-regulated interferon-signaling at the transcriptome level– Chronic ABMR signatures include up-regulated DEGs enriched in pathways of fibrogenesis, complement cascades, and TNF-signaling– Common signatures of TCMR and ABMR are enriched in pathways including NF-κB signaling, chemokine signaling and cytokine responses