Transcriptomic signatures of chronic active antibody-mediated rejection deciphered by RNA sequencing of human kidney allografts

Natural killer (NK) cells mediate spontaneous cell-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity. This dual functionality could enable their participation in chronic active antibody-mediated rejection (CA-ABMR). Earlier microarray profiling studies have not subcategorized antibody-mediated rejection into CA-ABMR and active-ABMR, and the gene expression pattern of CA-ABMR has not been compared with that of T cell-mediated rejection (TCMR). To fill these gaps, we RNA sequenced human kidney allograft biopsies categorized as CA-ABMR, active-ABMR, TCMR, or No Rejection (NR). Among the 15,910 genes identified in the biopsies, 60, 114, and 231 genes were uniquely overexpressed in CA-ABMR, TCMR, and active-ABMR, respectively; compared to NR, 50 genes were shared between CA-ABMR and active-ABMR, and 164 genes between CA-ABMR and TCMR. The overexpressed genes were annotated to NK cells and T cells in CA-ABMR and TCMR, and to neutrophils and monocytes in active-ABMR. The NK cell cytotoxicity and allograft rejection pathways were enriched in CA-ABMR. Genes encoding perforin, granzymes, and death receptor were overexpressed in CA-ABMR versus active-ABMR but not compared to TCMR. NK cell cytotoxicity pathway gene set variation analysis score was higher in CA-ABMR compared to active-ABMR but not in TCMR. Principal component analysis of the deconvolved immune cellular transcriptomes separated CA-ABMR and TCMR from active-ABMR and NR. Immunohistochemistry of kidney allograft biopsies validated a higher proportion of CD56+ NK cells in CA-ABMR than in active-ABMR. Thus, CA-ABMR was exemplified by the overexpression of the NK cell cytotoxicity pathway gene set and, surprisingly, molecularly more like TCMR than active-ABMR.

Case report: Daratumumab for treatment of refractory late or chronic active antibody-mediated rejection in renal allograft recipients with high levels of de novo donor-specific antibodies

Background

Late or chronic active antibody-mediated rejection (AMR) associated with de novo donor-specific antibodies (dnDSA) after renal transplantation is a great clinical challenge because it is often resistant to conventional therapies. Daratumumab, an anti-CD38 monoclonal antibody that can deplete plasma cells, may be effective for the treatment of late or chronic active AMR.

Methods

We designed a novel regimen that included early intensive therapy with daratumumab plus plasmapheresis (PP)/intravenous immunoglobulins (IVIG) and later maintenance therapy with daratumumab alone, and used this regimen to treat late or chronic active AMR in two kidney transplant recipients with extremely high levels of anti-DQ7 dnDSA.

Results

Both patients had a limited clinical response to the early treatment with rituximab and PP/IVIG (with or without splenic irradiation); however, they had a remarkable decrease in anti-DQ7 DSA (MFI value from ~20,000 to ~5,000) after 2-3 months of intensive therapy with daratumumab plus PP/IVIG. Over 20 months of follow-up, patient 1 maintained a low DSA (as low as 1,572) and normal renal function on daratumumab maintenance therapy. Patient 2 retained a low DSA and improved renal function and pathological lesions within one year after treatment but then deteriorated because of acute T cell-mediated rejection.

Conclusions

Our daratumumab-based regimen has shown promising results in the treatment of refractory late active or chronic active AMR in renal transplant recipients with high-level dnDSA. This may provide a reference for better use of daratumumab in the treatment of late or chronic active AMR.

Clinical effect of rabbit anti-thymocyte globulin for chronic active antibody-mediated rejection after kidney transplantation

Chronic active antibody-mediated rejection (CAAMR) is a frequent cause of late graft loss. However, effective treatment for CAAMR after kidney transplantation has not yet been established. Here, we present the case of a kidney transplant recipient who recovered from CAAMR after administration of rabbit anti-thymocyte globulin. A 61-year-old man underwent ABO-compatible living-donor kidney transplantation for end-stage kidney disease; the kidney was donated by his wife. Five years after the transplant, the patient's serum creatinine level and urine protein-to-creatinine ratio increased. He was subsequently diagnosed with CAAMR based on the kidney allograft biopsy and the presence of donor-specific human leukocyte antigen antibodies. Rabbit anti-thymocyte globulin treatment was administered following steroid pulse therapy. Subsequently, his serum creatinine levels and urine protein to creatinine ratio improved. There was also an improvement in the pathological findings seen on biopsy and the mean fluorescence intensity of donor-specific antibodies. In conclusion, this report describes the case of a kidney transplant recipient who developed CAAMR, treated using rabbit anti-thymocyte globulin. This strategy might be a viable treatment option for CAAMR after a kidney transplant.

PSMP Is Discriminative for Chronic Active Antibody-Mediated Rejection and Associate With Intimal Arteritis in Kidney Transplantation

Chronic active antibody-mediated rejection (CAAMR) is an intermediate process that occurs during the development of chronic antibody-mediated rejection (CAMR), which is a key problem associated with the long-term kidney grafts survival. This study investigated the role played by PC3-secreted microprotein (PSMP) in the progression of CAAMR and CAMR. We showed that CAAMR and CAMR patients’ allografts dysfunction with declined survival rate, which suggested that earlier diagnosis and treatment of CAAMR might be important to prevent irreversible chronic injury of CAMR progression. We found PSMP was an important factor in the development of chronic antibody-mediated rejection. The PSMP expression increased significantly in CAAMR biopsy samples but not in CAMR and control patients, which distinguished CAAMR patients from CAMR and non-rejection patients. Moreover, our results showed that infiltration of CD68⁺ macrophages in CAAMR increased, and the correlation between CD68⁺ macrophages and PSMP expression in CAAMR patients was significant. Additionally, our data also revealed that intimal arteritis (v-lesion) accompanied by increased macrophage infiltration might have contributed to more graft loss in CAAMR, and PSMP expression was significantly associated with the v-lesion score. These results indicated that PSMP played an important role in the recruitment of macrophages and promote intimal arteritis inducing allograft lost in CAAMR progression. In future study PSMP could be a potential histopathological diagnostic biomarker and treatment target for CAAMR in kidney transplantation.

Orosomucoid 1 is involved in the development of chronic allograft rejection after kidney transplantation

Chronic allograft rejection is the most common cause of long-term allograft failure. One reason is that current diagnostics and therapeutics for chronic allograft rejection are very limited. We here show that enhanced NFκB signaling in kidney grafts contributes to chronic active antibody-mediated rejection (CAAMR), which is a major pathology of chronic kidney allograft rejections. Moreover, we found that urinary orosomucoid 1 (ORM1) is a candidate marker molecule and therapeutic target for CAAMR. Indeed, urinary ORM1 concentration was significantly higher in kidney transplant recipients pathologically diagnosed with CAAMR than in kidney transplant recipients with normal histology, calcineurin inhibitor toxicity, or interstitial fibrosis and tubular atrophy. Additionally, we found that kidney biopsy samples with CAAMR expressed more ORM1 and had higher NFκB and STAT3 activation in tubular cells than samples from non-CAAMR samples. Consistently, ORM1 production was induced after cytokine-mediated NFκB and STAT3 activation in primary kidney tubular cells. The loss- and gain-of-function of ORM1 suppressed and promoted NFκB activation, respectively. Finally, ORM1-enhanced NFκB-mediated inflammation development in vivo. These results suggest that an enhanced NFκB-dependent pathway following NFκB and STAT3 activation in the grafts is involved in the development of chronic allograft rejection after kidney transplantation and that ORM1 is a non-invasive candidate biomarker and possible therapeutic target for chronic kidney allograft rejection.

Correlation between PKB/Akt, GSK-3β expression and tubular epithelial-mesenchymal transition in renal allografts with chronic active antibody-mediated rejection

Chronic antibody-mediated rejection (ABMR) is a major cause of the transplant renal interstitial fibrosis and transplanted kidney epithelial cell transdifferentiation is one of the main mechanisms. The transforming growth factor (TGF)-β1/integrin-linked kinase (ILK) signaling pathway has a significant role in the epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells; however, the molecular mechanisms of this process have remained elusive. The present study confirmed that Akt and glycogen synthase kinase (GSK)-3β, as TGF-β1 downstream signaling factors, are involved in fibrotic processes caused by kidney disease, which, however, has been rarely reported in the kidney transplant field. Based on the Banff 2009 standard, transplanted kidney specimens were classified according to the fibrosis level. The results showed that with the reduction of the interstitial fibrosis level, E-cadherin expression was gradually reduced, while α-smooth muscle actin expression progressively increased. The expression of Akt and GSK-3β in normal human kidney tissue was not obvious but showed a marked increase with the aggravation of the interstitial fibrosis level, which confirmed the occurrence of EMT during the fibrosis process, and that phosphorylated (p)-Akt and GSK-3β have an important role in the EMT process in the transplanted kidney. A correlation analysis of p-Akt, GSK-3β, TGF-β1 and ILK suggested that overexpression of p-Akt and GSK-3β may induce and mediate the transdifferentiation of renal tubular epithelial cells to myofibroblasts and that this proceeds via TGFβ1/ILK signaling pathways.

The prognostic values of caveolin-1 immunoreactivity in peritubular capillaries in patients with kidney transplantation

The low sensitivity of C4d immunoreactivity in peritubular capillaries (PTCs) hinders its use in the diagnosis of chronic active antibody-mediated rejection (CAAMR). C4d-negative CAAMR was defined in the 2013 Banff classification, which included the expression of endothelial-associated transcripts (ENDATs). We previously showed that the ENDAT caveolin-1 (CAV-1) is a distinct feature of CAAMR. In this study, we investigated the prognostic value of CAV-1 immunoreactivity in PTCs in kidney transplant patients. Ninety-eight kidney transplant recipients were included in this study. The prognostic value of CAV-1 immunoreactivity in PTCs was evaluated by double immunostaining for CAV-1 and pathologische Anatomie Leiden endothelium (PAL-E, a PTC marker) in the PTCs of kidney allograft biopsy samples. The patients were divided into two groups: CAV-1/PAL-E<50% and CAV-1/PAL-E≥50%. Kaplan-Meier curves showed that CAV-1/PAL-E≥50% patients had a significantly worse prognosis than that of CAV-1/PAL-E<50% patients (log-rank; P<.001). C4d staining of PTCs was not associated with the development of graft failure (log-rank; P=.345), whereas in a multivariate Cox regression analysis, CAV-1 immunoreactivity in PTCs was independently associated with graft failure (hazard ratio: 11.1; P=.0324). CAV-1 immunoreactivity in PTCs may serve as a prognostic marker for kidney allograft survival.

Microvascular inflammation in early protocol biopsies of renal allografts in cases of chronic active antibody-mediated rejection

AIM

Chronic active antibody-mediated rejection (chronic ABMR) is one important cause of late-stage renal allograft loss. However, few reports have used protocol biopsy to observe changes over time in cases that develop chronic ABMR. The aim of this study was to use protocol biopsy to clarify the histological features of cases that develop chronic ABMR.

METHODS

We recruited 379 ABO compatible patients who underwent protocol biopsy at our hospital from 2010 to 2014. Seventeen of these patients were diagnosed with chronic ABMR (chronic ABMR group), and 12 patients were class 2 donor-specific antibody (DSA) positive and were not diagnosed with chronic ABMR (class 2 DSA-positive group). With the addition of a control group consisting of 30 DSA negative patients, these three groups were compared for Banff factors in protocol biopsies taken 3 months, 6 months, 1 year, 3 years, and 5 years after the transplant.

RESULTS

Three months post transplant, the chronic ABMR group had a significantly higher number of patients exhibiting g + ptc > 0 than that in the control group (P = 0.01). At 1, 3, and 5 years post transplant, significantly more subjects in the chronic ABMR and class 2 DSA-positive groups compared with the control group exhibited g + ptc > 0 (P < 0.03). Five years post transplant, the chronic ABMR group exhibited a significantly higher mean c4d score than that in the control group (P = 0.02). The only significant difference observed between the chronic ABMR group and the class 2 DSA-positive group was in cg scores at 5 years post transplant, which were significantly higher in the chronic ABMR group (P = 0.03).

CONCLUSIONS

These results suggest that cases exhibiting microvascular inflammation in the early post-transplant period may develop chronic ABMR, and it would be highly beneficial to perform focused electron microscope surveillance of these cases.

Clinical and pathological analyses of transplant glomerulopathy cases

AIM

Transplant glomerulopathy (TG) is included as one of the criteria of chronic active antibody-mediated rejection (c-AMR) in Banff 09 classification. In this report, we discuss the clinical and pathological analyses of cases of TG after renal transplantation.

PATIENTS

TG was diagnosed in 86 renal allograft biopsy specimens (BS) obtained from 50 renal transplant patients followed up at our institute between January 2006 and October 2012. We retrospectively reviewed the data of these 86 BS and 50 patients.

RESULTS

Among the 50 patients, 42 (84%) had a history of acute rejection (AR); of these, 30 (60%) had acute antibody-mediated rejection (a-AMR). Among the 86 BS of TG, the TG was mild in 35 cases (cg1 in Banff classification), moderate in 28 cases (cg2) and severe in 23 cases (cg3). Peritubular capillaritis was present in 74 BS (86%), transplant glomerulitis in 65 (76%), interstitial fibrosis and tubular atrophy (IF/TA) in 71 (83%), thickening of the peritubular capillary (PTC) basement membrane in 72 (84%), and interstitial inflammation in 40 (47%). C4d deposition in the PTC was present in 49 BS (57%); 39 of these 49 BS showed diffuse C4d deposits in the PTC (C4d3), while the remaining 10 BS showed focal deposits (C4d2). Diffuse C4d deposition in the glomerular capillaries (GC) was seen in 70 BS (81%), while focal C4d deposition in the GC was seen in 9 (11%). In the assay using plastic beads coated with HLA antigen performed in 67 serum samples obtained in the peri-biopsy period, circulating ant-HLA alloantibody was detected in 55 (82%); in 33 of the 55 (49%) samples, donor-specific antibodies (DSA) were detected. Among our study, the findings in 22 BS (26%) fully met the criteria for c-AMR in Banff '09 classification, including TG, C4d deposition in the PTC and presence of DSA, while those in 27 BS were suspicious of c-AMR. Deterioration of the renal allograft function after the biopsies was seen in 31 patients (62%), of which 11 lost their graft.

CONCLUSIONS

We suggest that histopathological changes of transplant glomerulopathy might be accompanied by inflammation of the microvasculature, such as transplant glomerulitis and peritubular capillaritis, thickening of the peritubular capillary basement membrane, and circulating anti-HLA antibodies. C4d deposition in the PTC is not always present in biopsy specimens of TG. We speculated that C4d deposition in the GC, rather than that in the PTC might be a more characteristic manifestation of TG. Many of the patients with TG had a history of AR. Anti-HLA antibody Class II, particularly when the antibody was DSA Class II, appeared to be associated with the development of TG. The prognosis of grafts exhibiting TG was not too good even under the currently used immunosuppressive protocol.

Better understanding of transplant glomerulopathy secondary to chronic antibody-mediated rejection

Transplant glomerulopathy (TG) is generally accepted to result from repeated episodes of endothelial activation, injury and repair, leading to pathological abnormalities of double contouring or multi-layering of the glomerular basement membrane. TG is a major sequel of chronic active antibody-mediated rejection (cABMR), from pre-existing or de novo anti-HLA antibodies. Hepatitis C infection, thrombotic microangiopathy or other factors may also contribute to TG development. TG prevalence is 5-20% in most series, reaching 55%, in some high-risk cohorts, and is associated with worse allograft outcomes. Despite its prevalence and clinical significance, few well-studied treatment options have been proposed. Similar to desensitization protocols, plasmapheresis with or without immunoabsorption, high-dose intravenous immunoglobulin, rituximab, bortezomib and eculizumab have been proposed in the treatment of TG due to cABMR individually or in various combinations. Robust clinical trials are urgently needed to address this major cause of allograft loss. This review summarizes the current knowledge of the epidemiology, etiology, pathology, and the preventive and treatment options for TG secondary to cABMR.