E. Benazzi

Can C4d immunostaining on endomyocardial biopsies be considered a prognostic biomarker in heart transplant recipients

Background. The aim of this study was to assess the significance of positive C4d capillary immunostaining of endomyocardial biopsies and its correlation to clinical outcome in adult heart transplant recipients. Methods. Nine hundred eighty-five endomyocardial biopsies from 107 heart transplant recipients were evaluated. Immunostaining for detection of intragraft C4d capillary deposition was performed on paraffin-embedded tissue using anti-human C4d polyclonal antibody. Results. Positive staining of C4d was present in 36 patients (34%) and antibody-mediated rejection in eight patients (7%). The patients were subdivided into four groups on the basis of their C4d, circulating antidonor antibodies (donor-specific antibodies [DSAs]), and graft function: group 1=C4d positive, DSA negative, and no graft dysfunction; group 2=C4d positive, DSA positive, and no graft dysfunction; group 3=C4d positive, DSA positive, and signs of graft dysfunction, and group 0 (control)=all negative. An higher mortality risk was found in C4d-positive patients, when compared with negative ones (unadjusted hazard ratios: group 1: 18, group 2: 61, and group 3: 32-fold risk; P<0.0001). Conclusions. Antibody-mediated rejection is a complex and ongoing phenomenon with different phenotypic features. C4d positive predicts worse prognosis. C4d negative and DSA can be used as early mortality predictors in patients without signs of graft dysfunction.

Heart transplantation with donor-specific antibodies directed toward denatured HLA-A*02:01: a case report.

The development of solid-phase assays for antibody detection has aided in the frequent detection of human leukocyte antigen (HLA) antibodies in nonalloimmunized males. Some scientists have reported that these HLA antibodies are produced to pathogens or allergens and the reactivity with HLA coated beads is the result of cross-reactive epitopes. These antibodies may also be directed toward cryptic epitopes exposed on the denatured beads. In this report, we describe the case of a heart transplanted patient who exhibited anti-HLA-A*02:01 donor-specific antibodies detected with a bead-based assay (Luminex) and undetected with the complement-dependent cytotoxicity (CDC) test. Posttransplant monitoring, carried out with CDC and with Luminex on sera from this patient collected at the 2nd, 4th, 8th, and 12th posttransplant weeks and at 1 year confirmed the presence of anti-HLA-A*02:01 in all serum samples. Additional tests carried out with denatured and intact HLA molecules using single antigen beads demonstrated that the antibody was directed toward a cryptic epitope. One year after transplantation the patient is doing well. No sign of antibody-mediated rejection was observed throughout the follow-up. A comprehensive evaluation of the anamnesis and of antibodies is critical to avoid needless exclusion of organ donors.

Role of morphologic parameters on endomyocardial biopsy to detect sub-clinical antibody-mediated rejection in heart transplantation.

BACKGROUND The present study evaluated if morphologic parameters detect signs of early sub-clinical or latent stages of antibody-mediated rejection (AMR) and their correlation with C4d staining in cardiac transplants recipients. METHODS The study reviewed 1,270 endomyocardial biopsies (EMB) from 131 patients. Of these, 61 stained positive for C4d in the absence of acute cellular rejection >2R. Sixty-six EMB specimens negative for C4d were matched for pre-transplant diagnosis, time after transplantation, age, and acute cellular rejection (ACR) grading. Histopathologic evaluation and C4d staining were performed on formalin-fixed, paraffin-embedded sections using the C4d polyclonal antibody. RESULTS Of the 8 histologic characteristics evaluated, only endothelial swelling (78.7% sensitivity, 28.8% specificity; positive likelihood ratio, 1.10) and interstitial edema (77% sensitivity, 31.8% specificity; positive likelihood ratio, 1.13) could be considered fair predictors of C4d capillary positivity. The presence of mononuclear cells in capillaries in relation to C4d positivity showed 39.3% sensitivity and 68.2% specificity. Combining the parameters endothelial swelling and mononuclear cells in capillaries, sensitivity was 31.1% (95% confidence interval [CI] 19.9-44.3) and specificity was 71.2% (95 CI, 58.8-81.7), with a positive likelihood ratio of 1.08 (95% CI, 0.68-1.84). CONCLUSIONS Our results showed that histologic parameters did not always detect signs of early sub-clinical or latent stages of AMR. Combining the parameters of endothelial swelling and intracapillary mononuclear cells did not significantly improve the sensitivity or specificity. Screening recommendations should, therefore, be modified to include more sensitive tests such as C4d staining in the routine protocol to improve patient risk stratification.

Intravascular macrophages in cardiac allograft biopsies for diagnosis of early and late antibody-mediated rejection

BACKGROUND The aim of our study was to evaluate the role of intravascular macrophages in the diagnosis of early and late antibody-mediated rejection (AMR) on endomyocardial biopsies (EMBs). METHODS We reviewed 1,420 consecutive EMBs from 131 patients and selected 75 C4d+ EMBs. The C4d+ group was compared with a control group (66 patients) matched for age, gender, date of transplantation, follow-up, immunosuppressive regimen and primary heart disease. A total of 141 EMBs were evaluated. Immunoperoxidase staining for C4d and CD68 were performed. Post-transplant IgG anti-HLA reactivity was investigated by Luminex technology. Clinical data were also collected. Fourteen EMBs were available from 11 symptomatic AMR patients. RESULTS Of the 141 EMBs evaluated, 53 were positive for intravascular macrophages (CD68); among them, 32 were also positive for C4d (32 of 53, 60.4%). Of the 88 CD68- EMBs, 43 were also C4d+ (43 of 88, 48.9%). Of the 53 CD68+ EMBs, 30 EMBs were within the first year since transplantation (30 of 53, 57.8%), and among these 21 were also positive for C4d (21 of 30, 70.0%). In the late period, among the 23 CD68+ EMBs (23 of 53, 42.2%) 11 were also positive for C4d (11 of 23, 47.8%). In the early period, intravascular macrophages were more common in symptomatic (3 of 3, 100%) than asymptomatic (3 of 11, 27.3%) patients. Sensitivity and specificity of intravascular macrophages in predicting donor-specific antibodies (DSA) within the first year were 50.0% and 100.0%, respectively. CONCLUSIONS Intravascular macrophages predict C4d, DSA and symptoms early after transplantation; however, in the late period, they are unable to identify patients with circulating DSA, C4d and/or symptoms.

A prospective comparison of mid-term outcomes in patients treated with heart transplantation with advanced age donors versus left ventricular assist device implantation

OBJECTIVES In Europe, the age of heart donors is constantly increasing. Ageing of heart donors limits the probability of success of heart transplantation (HTx). The aim of this study is to compare the outcome of patients with advanced heart failure (HF) treated with a continuous-flow left ventricular assist device (CF-LVAD) with indication as bridge to transplantation (BTT) or bridge to candidacy (BTC) versus recipients of HTx with the donors age above 55 years (HTx with donors >55 years). METHODS we prospectively evaluated 301 consecutive patients with advanced HF treated with a CF-LVAD (n = 83) or HTx without prior bridging (n = 218) in our hospital from January 2006 to January 2015. We compared the outcome of CF-LVAD-BTT (n = 37) versus HTx with donors >55 years (n = 45) and the outcome of CF-LVAD-BTT plus BTC (n = 62) versus HTx with donors >55 years at the 1- and 2-year follow-up. Survival was evaluated according to the first operation. RESULTS The perioperative (30-day) mortality rate was 0% in the LVAD-BTT group vs 20% (n = 9) in the HTx group with donors >55 years (P = 0.003). Perioperative mortality occurred in 5% of the LVAD-BTT/BTC patients (n = 3) and in 20% of the HTx with donors >55 year group (P = 0.026). Kaplan-Meier curves estimated a 2-year survival rate of 94.6% in CF-LVAD-BTT vs 68.9% in HTx with donors >55 years [age- and sex-adjusted hazard ratio (HR) 0.25; 95% confidence interval (CI) 0.08-0.81; P = 0.02 in favour of CF-LVAD]. Considering the post-HTx outcome, a trend in favour of CF-LVAD-BTT was also observed (age- and sex-adjusted HR 0.45; 95% CI 0.17-1.16; P = 0.09 in favour of CF-LVAD), whereas CF-LVAD-BTT/BTC showed a similar survival at 2 years compared with HTx with donors >55 years, both censoring the follow-up at the time of HTx and considering the post-HTx outcome. CONCLUSIONS Early and mid-term outcomes of patients treated with a CF-LVAD with BTT indication seem better than HTx with old donors. It must be emphasized that up to 19% of patients in the CF-LVAD/BTT group underwent transplantation in an urgent condition due to complications related to the LVAD. At the 2-year follow-up, CF-LVAD with BTT and BTC indications have similar outcome than HTx using old heart donors. These results must be confirmed in a larger and multicentre population and extending the follow-up.

MicroRNA signatures in cardiac biopsies and detection of allograft rejection

BACKGROUND Identification of heart transplant (HTx) rejection currently relies on immunohistology and immunohistochemistry. We aimed to identify specific sets of microRNAs (miRNAs) to characterize acute cellular rejection (ACR), antibody-mediated rejection (pAMR), and mixed rejection (MR) in monitoring formalin-fixed paraffin-embedded (FFPE) endomyocardial biopsies (EMBs) in HTx patients. METHODS In this study we selected 33 adult HTx patients. For each, we chose the first positive EMB for study of each type of rejection. The next-generation sequencing (NGS) IonProton technique and reverse transcript quantitative polymerase chain reaction (RT-qPCR) analysis were performed on FFPE EMBs. Using logistic regression analysis we created unique miRNA signatures as predictive models of each rejection. In situ PCR was carried out on the same EMBs. RESULTS We obtained >2,257 mature miRNAs from all the EMBs. The 3 types of rejection showed a different miRNA profile for each group. The logistic regression model formed by miRNAs 208a, 126-5p, and 135a-5p identified MR; that formed by miRNAs 27b-3p, 29b-3p, and 199a-3p identified ACR; and that formed by miRNAs 208a, 29b-3p, 135a-5p, and 144-3p identified pAMR. The expression of miRNAs on tissue, through in situ PCR, showed different expressions of the same miRNA in different rejections. miRNA 126-5p was expressed in endothelial cells in ACR but in cardiomyocytes in pAMR. In ACR, miRNA 29b-3p was significantly overexpressed and detected in fibroblasts, whereas in pAMR it was underexpressed and detected only in cardiomyocytes. CONCLUSIONS miRNA profiling on FFPE EMBs differentiates the 3 types of rejection. Localization of expression of miRNAs on tissue showed different expression of the same miRNA for different cells, suggesting different roles of the same miRNA in different rejections.