Plasma‐Derived C1 Esterase Inhibitor for Acute Antibody‐Mediated Rejection Following Kidney Transplantation: Results of a Randomized Double‐Blind Placebo‐Controlled Pilot Study

Antibody‐mediated rejection (AMR) is typically treated with plasmapheresis (PP) and intravenous immunoglobulin (standard of care; SOC); however, there is an unmet need for more effective therapy. We report a phase 2b, multicenter double‐blind randomized placebo‐controlled pilot study to evaluate the use of human plasma‐derived C1 esterase inhibitor (C1 INH) as add‐on therapy to SOC for AMR. Eighteen patients received 20 000 units of C1 INH or placebo (C1 INH n = 9, placebo n = 9) in divided doses every other day for 2 weeks. No discontinuations, graft losses, deaths, or study drug‐related serious adverse events occurred. While the study's primary end point, a difference between groups in day 20 pathology or graft survival, was not achieved, the C1 INH group demonstrated a trend toward sustained improvement in renal function. Six‐month biopsies performed in 14 subjects (C1 INH = 7, placebo = 7) showed no transplant glomerulopathy (TG) (PTC+cg≥1b) in the C1 INH group, whereas 3 of 7 placebo subjects had TG. Endogenous C1 INH measured before and after PP demonstrated decreased functional C1 INH serum concentration by 43.3% (p < 0.05) for both cohorts (C1 INH and placebo) associated with PP, although exogenous C1 INH–treated patients achieved supraphysiological levels throughout. This new finding suggests that C1 INH replacement may be useful in the treatment of AMR.     

A Probabilistic Approach to Histologic Diagnosis of Antibody‐Mediated Rejection in Kidney Transplant Biopsies

Histologic diagnosis of antibody‐mediated rejection (ABMR) in kidney transplant biopsies uses lesion score cutoffs such as 0 versus >0 rather than actual scores and requires donor‐specific antibody (DSA); however, cutoffs lose information, and DSA is not always reliable. Using microarray‐derived molecular ABMR scores as a histology‐independent estimate of ABMR in 703 biopsies, we reassessed criteria for ABMR to determine relative importance of various lesions, the utility of equations using actual scores rather than cutoffs, and the potential for diagnosing ABMR when DSA is unknown or negative. We confirmed that the important features for ABMR diagnosis were peritubular capillaritis (ptc), glomerulitis (g), glomerular double contours, DSA and C4d staining, but we questioned some features: arterial fibrosis, vasculitis, acute tubular injury, and sum of ptc+g scores. Regression equations using lesion scores predicted molecular ABMR more accurately than score cutoffs (area under the curve 0.85–0.86 vs. 0.75). DSA positivity improved accuracy, but regression equations predicted ABMR with moderate accuracy when DSA was unknown. Some biopsies without detectable DSA had high probability of ABMR by regression, although most had HLA antibody. We concluded that regression equations using lesion scores plus DSA maximized diagnostic accuracy and can estimate probable ABMR when DSA is unknown or undetectable.     

IL‐17 Expression by Tubular Epithelial Cells in Renal Transplant Recipients with Acute Antibody‐Mediated Rejection

Acute rejection is still a common complication of kidney transplantation. IL‐17 is known to be associated with allograft rejection but the cellular source and the role of this cytokine remains unclear. We investigated IL‐17 graft expression in renal transplant recipients with acute antibody‐mediated rejection (ABMR), acute T‐cell‐mediated rejection (TCMR), interstitial fibrosis and tubular atrophy (IFTA) and acute tubular damage due to calcineurin‐inhibitor toxicity (CNI). In acute ABMR, tubular IL‐17 protein expression was significantly increased compared to TCMR, where most of the IL‐17⁺cells were CD4⁺graft infiltrating lymphocytes, IFTA and CNI control groups. The tubular expression of IL‐17 in acute ABMR colocalized with JAK2 phosphorylation and peritubular capillaries C4d deposition. In addition, IL‐17 tubular expression was directly and significantly correlated with the extension of C4d deposits. In cultured proximal tubular cells, C3a induced IL‐17 gene and protein expression along with an increased in JAK2 phosphorylation. The inhibition of JAK2 abolished C3a‐induced IL‐17 expression. The use of steroids and monoclonal antibodies reduced IL‐17 expression, JAK2 phosphorylation and C4d deposition in acute ABMR patients. Our data suggest that tubular cells represent a significant source of IL‐17 in ABMR and this event might be mediated by the complement system activation featuring this condition.     

Microarray Diagnosis of Antibody‐Mediated Rejection in Kidney Transplant Biopsies: An International Prospective Study (INTERCOM)

In a reference set of 403 kidney transplant biopsies, we recently developed a microarray‐based test that diagnoses antibody‐mediated rejection (ABMR) by assigning an ABMR score. To validate the ABMR score and assess its potential impact on practice, we performed the present prospective INTERCOM study ( clinicaltrials.gov NCT01299168) in 300 new biopsies (264 patients) from six centers: Baltimore, Barcelona, Edmonton, Hannover, Manchester and Minneapolis. We assigned ABMR scores using the classifier created in the reference set and compared it to conventional assessment as documented in the pathology reports. INTERCOM documented uncertainty in conventional assessment: In 41% of biopsies where ABMR features were noted, the recorded diagnoses did not mention ABMR. The ABMR score correlated with ABMR histologic lesions and donor‐specific antibodies, but not with T cell–mediated rejection lesions. The agreement between ABMR scores and conventional assessment was identical to that in the reference set (accuracy 85%). The ABMR score was more strongly associated with failure than conventional assessment, and when the ABMR score and conventional assessment disagreed, only the ABMR score was associated with early progression to failure. INTERCOM confirms the need to reduce uncertainty in the diagnosis of ABMR, and demonstrates the potential of the ABMR score to impact practice.     

Deceased-Donor Acute Kidney Injury and Acute Rejection in Kidney Transplant Recipients: A Multicenter Cohort

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Identifying Subphenotypes of Antibody‐Mediated Rejection in Kidney Transplants

The key lesions in antibody‐mediated kidney transplant rejection (ABMR) are microcirculation inflammation (peritubular capillaritis and/or glomerulitis lesions, abbreviated “pg”) and glomerular double contours (cg lesions). We used these features to explore subphenotypes in 164 indication biopsies with ABMR‐related diagnoses: 137 ABMR (109 pure and 28 mixed with T cell–mediated rejection [TCMR]) and 27 transplant glomerulopathy (TG), identified from prospective multicenter studies. The lesions indicated three ABMR subphenotypes: pgABMR, cgABMR, and pgcgABMR. Principal component analysis confirmed these subphenotypes and showed that TG can be reclassified as pgcgABMR (n = 17) or cgABMR (n = 10). ABMR‐related biopsies included 45 pgABMR, 90 pgcgABMR, and 25 cgABMR, with four unclassifiable. Dominating all time intervals was the subphenotype pgcgABMR. The pgABMR subphenotype presented earliest (median <2 years), frequently mixed with TCMR, and was most associated with nonadherence. The cgABMR subphenotype presented late (median 9 years). Subphenotypes differed in their molecular changes, with pgABMR having the most histologic–molecular discrepancies (i.e. potential errors). Donor‐specific antibody (DSA) was not identified in 29% of pgcgABMR and 46% of cgABMR, but failure rates and molecular findings were similar to cases where DSA was known to be positive. Thus, ABMR presents distinct subphenotypes, early pg‐dominant, late cg‐dominant, and combined pgcg phenotype, differing in time, molecular features, accompanying TCMR, HLA antibody, and probability of nonadherence.     

Bortezomib for Acute Antibody‐Mediated Rejection in Liver Transplantation

Antibody‐mediated rejection (AMR) is an uncommon, but challenging type of rejection after solid organ transplantation. We review three cases of AMR in ABO‐compatible liver transplant recipients. These cases were characterized by severe acute rejection resistant to steroids and antithymocyte globulin, histologic evidence of plasma cell infiltrates, C4d positivity and high serum anti‐HLA donor‐specific antibodies. All three patients were treated with bortezomib, a proteasome inhibitor effective in depleting plasma cells. After treatment, all patients had improved or normal liver function tests, resolution of C4d deposition and significant decline in their HLA donor‐specific antibodies.     

Progressive Multifocal Leukoencephalopathy in a Heart Transplant Recipient Following Rituximab Therapy for Antibody‐Mediated Rejection

We report the case of a male heart transplant recipient who developed acute antibody‐mediated rejection and was treated with 5 weeks of a rituximab‐containing regimen. Two months later he presented with progressive motor and cognitive impairments and was diagnosed with progressive multifocal leukoencephalopathy (PML). He was treated with reduction of his immunosuppressive medications, mirtazapine, IVIG and plasmapheresis. He died within weeks. We reviewed the current literature on PML and its association with immunosuppression, highlighting its impact in the setting of solid organ transplantation and considering the potential effect of newer biologic drugs on the incidence of this devastating disease in the transplant population.     

Eculizumab Salvage Therapy for Antibody‐Mediated Rejection in a Desensitization‐Resistant Intestinal Re‐Transplant Patient

The presence of elevated calculated panel reactive antibody (cPRA) and anti‐HLA donor specific antibodies (DSA) are high risk factors for acute antibody‐mediated rejection (AAMR) in intestinal transplantation that may lead to graft loss. Eculizumab has been used for the treatment of AAMR in kidney transplantation of sensitized patients that do not respond to other treatment. Here, we report a case where eculizumab was used to treat AAMR in a desensitization‐resistant intestinal re‐transplant patient. A male patient lost his intestinal graft to AAMR 8.14 years after his primary transplant. He received a second intestinal graft that had to be explanted a month later due to refractory AAMR. The patient remained highly sensitized despite multiple treatments. He received a multivisceral graft and presented with severe AAMR on day 3 posttransplantation. The AAMR was successfully treated with eculizumab. The patient presently maintains an elevated cPRA level above 90% but his DSAs have decreased from 18 000 MFI (mean fluorescent intensity) to below the positive cut‐off value of 3000 MFI and remains rejection free with a 2‐year follow‐up since his multivisceral transplant. Eculizumab offers an alternative to treat AAMR in intestinal transplantation in desensitization‐resistant patients.     

Presentation and Outcomes of C4d‐Negative Antibody‐Mediated Rejection After Kidney Transplantation

The updated Banff classification allows for the diagnosis of antibody‐mediated rejection (AMR) in the absence of peritubular capillary C4d staining. Our objective was to quantify allograft loss risk in patients with consistently C4d‐negative AMR (n = 51) compared with C4d‐positive AMR patients (n = 156) and matched control subjects without AMR. All first‐year posttransplant biopsy results from January 2004 through June 2014 were reviewed and correlated with the presence of donor‐specific antibody (DSA). C4d‐negative AMR patients were not different from C4d‐positive AMR patients on any baseline characteristics, including immunologic risk factors (panel reactive antibody, prior transplant, HLA mismatch, donor type, DSA class, and anti‐HLA/ABO‐incompatibility). C4d‐positive AMR patients were significantly more likely to have a clinical presentation (85.3% vs. 54.9%, p < 0.001), and those patients presented substantially earlier posttransplantation (median 14 [interquartile range 8–32] days vs. 46 [interquartile range 20–191], p < 0.001) and were three times more common (7.8% vs 2.5%). One‐ and 2‐year post–AMR‐defining biopsy graft survival in C4d‐negative AMR patients was 93.4% and 90.2% versus 86.8% and 82.6% in C4d‐positive AMR patients, respectively (p = 0.4). C4d‐negative AMR was associated with a 2.56‐fold (95% confidence interval, 1.08–6.05, p = 0.033) increased risk of graft loss compared with AMR‐free matched controls. No clinical characteristics were identified that reliably distinguished C4d‐negative from C4d‐positive AMR. However, both phenotypes are associated with increased graft loss and thus warrant consideration for intervention.     

Posttransplant De Novo Donor‐Specific HLA Antibodies Identify Pediatric Kidney Recipients at Risk for Late Antibody‐Mediated Rejection

The emerging role of humoral immunity in the pathogenesis of chronic allograft damage has prompted research aimed at assessing the role of anti‐HLA antibody (Ab) monitoring as a tool to predict allograft outcome. Data on the natural history of allografts in children developing de novo Ab after transplantation are limited. Utilizing sera collected pretransplant, and serially posttransplant, we retrospectively evaluated 82 consecutive primary pediatric kidney recipients, without pretransplant donor‐specific antibodies (DSA), for de novo Ab occurrence, and compared results with clinical–pathologic data. At 4.3‐year follow up, 19 patients (23%) developed de novo DSA whereas 24 had de novo non‐DSA (NDSA, 29%). DSA appeared at a median time of 24 months after transplantation and were mostly directed to HLA‐DQ antigens. Among the 82 patients, eight developed late/chronic active C4d+ antibody‐mediated rejection (AMR), and four C4d‐negative AMR. Late AMR correlated with DSA (p < 0.01), whose development preceded AMR by 1‐year median time. Patients with DSA had a median serum creatinine of 1.44 mg/dL at follow up, significantly higher than NDSA and Ab‐negative patients (p < 0.005). In our pediatric cohort, DSA identify patients at risk of renal dysfunction, AMR and graft loss; treatment started at Ab emergence might prevent AMR occurrence and/or progression to graft failure.     

Costs of Treatment of Acute Antibody-Mediated Rejection in Kidney Transplant Recipients

BackgroundAntibody-mediated rejection (AMR) remains challenging in kidney transplant recipients. It may negatively impact the graft survival, and its treatment is associated to relatively high expenses. The aim of our study was to assess the costs of treatment of acute AMR in the Polish settings.MethodsA total of 11 kidney transplant recipients with acute AMR diagnosed between September 2016 and August 2019 and treated in our center were included. Direct costs of inpatient and outpatient care in the first year after AMR diagnosis from the perspective of a transplant center were retrospectively calculated.ResultsThe costs of treatment of acute AMR were considerably high, with a mean 1-month cost of treatment 12,718 PLN (～€2925; ～3307 US dollars). That means that costs of management of kidney transplant recipients with acute AMR are almost 2-fold higher than hemodialysis. Intravenous immunoglobulin was responsible for the majority (55%) of costs.ConclusionsTreatment of acute AMR increases the costs of post–kidney transplant care in involved patients. Therefore, efforts should be made to minimize the risk for acute AMR. Despite its potential clinical benefits, management of acute AMR is even more expensive than dialysis. Therefore, further cost-effectiveness analyses are needed to justify the spending and to establish the best treatment regimens.     

Proteasome Inhibitor Carfilzomib‐Based Therapy for Antibody‐Mediated Rejection of the Pulmonary Allograft: Use and Short‐Term Findings

We present this observational study of lung transplant recipients (LTR) treated with carfilzomib (CFZ)‐based therapy for antibody‐mediated rejection (AMR) of the lung. Patients were considered responders to CFZ if complement‐1q (C1q)‐fixing ability of their immunodominant (ID) donor‐specific anti‐human leukocyte antibody (DSA) was suppressed after treatment. Treatment consisted of CFZ plus plasma exchange and immunoglobulins. Fourteen LTRs underwent CFZ for 20 ID DSA AMR. Ten (71.4%) of LTRs responded to CFZ. DSA IgG mean fluorescence intensity (MFI) fell from 7664 (IQR 3230–11 874) to 1878 (653–7791) after therapy (p = 0.001) and to 1400 (850–8287) 2 weeks later (p = 0.001). DSA C1q MFI fell from 3596 (IQR 714–14 405) to <30 after therapy (p = 0.01) and <30 2 weeks later (p = 0.02). Forced expiratory volume in 1s ( FEV₁) fell from mean 2.11 L pre‐AMR to 1.92 L at AMR (p = 0.04). FEV₁ was unchanged after CFZ (1.91 L) and subsequently rose to a maximum of 2.13 L (p = 0.01). Mean forced expiratory flow during mid forced vital capacity (25–75) (FEF_25–75) fell from mean 2.5 L pre‐AMR to 1.95 L at AMR (p = 0.01). FEF_25–75 rose after CFZ to 2.54 L and reached a maximum of 2.91 L (p = 0.01). Responders had less chronic lung allograft dysfunction or progression versus nonresponders (25% vs. 83%, p = 0.04). No deaths occurred within 120 days and 7 patients died post CFZ therapy of allograft failure. Larger prospective interventional studies are needed to further describe the benefit of CFZ‐based therapy for pulmonary AMR.     

Early Ultrastructural Changes in Renal Allografts: Correlation With Antibody‐Mediated Rejection and Transplant Glomerulopathy

Transplant glomerulopathy (TG) is associated with antibody‐mediated renal allograft rejection (AMR) and reduced graft survival. Histologically, TG is typically seen >1 year posttransplantation. However, ultrastructural changes including glomerular endothelial swelling, subendothelial widening and early glomerular basement membrane duplication are associated with development of TG but appear much earlier. We examined the specificity of these changes for AMR, and whether these are inevitably associated with development of TG. Of 98 for cause renal allograft biopsies carried out within 3 months of transplantation with available serologic data, 17 showed C4d‐positive AMR and 16 had histologic changes of AMR and donor‐specific antibodies (DSA), but no C4d. All three ultrastructural changes were seen in 11 of 17 biopsies with C4d‐positive AMR, 8 of 16 with histologic changes of AMR and DSA but no C4d, and 0 of 65 without histologic changes of AMR and/or DSA (p < 0.0001 for both of the former groups vs. the latter). Twenty patients with positive DSA (18 with histologic changes of AMR and 11 C4d‐positive) had ≥1 follow‐up biopsy; eight developed overt TG 3.5–30 months posttransplantation. Among the 18 patients with DSA and histologic changes of AMR, 11 C4d‐positive and 7 C4d‐negative, treatment for AMR after the early biopsy significantly reduced subsequent development of overt TG.