De Novo Complement-Binding Anti-HLA Antibodies in Heart Transplanted Patients Is Associated with Severe Cardiac Allograft Vasculopathy and Poor Long-Term Survival.

Introduction: De novo anti-HLA donor specific antibodies (DSA) have been inconsistently associated with cardiac allograft vasculopathy (CAV) and long-term mortality. We tested whether C3d-binding de novo DSA were associated with CAV or long-term-survival. Methods: We included 282 consecutive patients without preformed DSA on coronary angiography between 2010 and 2012. Angiographies were classified according to CAV ISHLT grading. The primary outcome was a composite criterion of severe CAV or mortality. As the impact of de novo antibodies should be assessed only after appearance, we used a Cox regression with time-dependent covariables. Results: Of the 282 patients, 51(18%) developed de novo DSA during follow-up, 29 patients had DSA with C3d-binding ability (DSA+C3d+), and 22 were without C3d-binding ability (DSA+C3d-). Compared with patients without DSA, DSA+C3d+ patients had an increased risk for the primary outcome of severe CAV or mortality (adjusted HR = 4.31 (2.40−7.74) p < 0.001) and long-term mortality (adjusted HR = 3.48 (1.97−6.15) p < 0.001) whereas DSA+C3d- did not (adjusted HR = 1.04 (0.43−2.47) p = 0.937 for primary outcome and HR = 1.08 (0.45−2.61) p = 0.866 for mortality). Conclusion: According to this large monocentric study in heart transplant patients, donor specific antibodies were associated with worse clinical outcome when binding complement. DSA and their complement-binding ability should thus be screened for to optimize heart transplant patient follow-up.

Failure to remove de novo donor-specific HLA antibodies is influenced by antibody properties and identifies kidney recipients with late antibody-mediated rejection destined to graft loss - a retrospective study.

Current research is focusing on identifying bioclinical parameters for risk stratification of renal allograft loss, largely due to antibody-mediated rejection (AMR). We retrospectively investigated graft outcome predictors in 24 unsensitized pediatric kidney recipients developing HLA de novo donor-specific antibodies (dnDSAs), and treated for late AMR with plasmapheresis + low-dose IVIG + Rituximab or high-dose IVIG + Rituximab. Renal function and DSA properties were assessed before and longitudinally post treatment. The estimated GFR (eGFR) decline after treatment was dependent on a negative % eGFR variation in the year preceding treatment (P = 0.021) but not on eGFR at treatment (P = 0.74). At a median follow-up of 36 months from AMR diagnosis, 10 patients lost their graft. Altered eGFR (P < 0.001) and presence of C3d-binding DSAs (P = 0.005) at treatment, and failure to remove DSAs (P = 0.01) were negatively associated with graft survival in the univariable analysis. Given the relevance of DSA removal for therapeutic success, we analyzed antibody properties dictating resistance to anti-humoral treatment. In the multivariable analysis, C3d-binding ability (P < 0.05), but not C1q-binding, and high mean fluorescence intensity (P < 0.05) were independent factors characterizing DSAs scarcely susceptible to removal. The poor prognosis of late AMR is related to deterioration of graft function prior to treatment and failure to remove C3d binding and/or high-MFI DSAs.

Computer-assisted topological analysis of renal allograft inflammation adds to risk evaluation at diagnosis of humoral rejection.

Antibody-mediated rejection is associated with heterogeneous kidney allograft outcomes. Accurate evaluation of risk for graft loss at time of diagnosis is necessary to offer personalized treatment. In contrast with serological and molecular assessment, morpho-histological evaluation of antibody-mediated rejection lesions has not significantly evolved. This relies on Banff classifications designed to be of diagnostic discriminatory power rather than prognostic and face quantitative and qualitative limitations. Here we developed a method of Computer-assisted Analysis of Graft Inflammation (CAGI) to improve the classification of allograft inflammation. Digitization of immunostained biopsy sections, image processing and algorithm-driven analysis allowed quantification of macrophages, T cells, B cells, and granulocytes per unit surface of interstitium, capillaries or glomeruli. CAGI was performed on biopsy specimens of 52 patients with extensively phenotyped antibody-mediated rejection. Macrophage numbers in capillaries and interstitium, but not Banff scores or the amount of other immune cell subsets, correlated with donor-specific antibody (DSA) mean fluorescence intensity and DSA-C3d status. The quantity of macrophages in the interstitium and DSA-C3d status were the only independent predictors for significant allograft loss at the time of antibody-mediated rejection diagnosis (hazard ratio 3.71 and 2.34, respectively). A significant strategy integrating the DSA-C3d assay and the quantification of interstitial macrophages allowed identification of three groups with distinct renal prognosis: DSA-C3d-, DSA-C3d+/macrophages-low and DSAC3d+/macrophages-high. Thus, CAGI brings a missing piece to the antibody-mediated rejection puzzle by identifying morpho-histological processes that bridge in vitro parameters of DSA pathogenicity and graft loss. Hence, this approach could be useful in future integrated strategies of risk evaluation.

Complement-Binding Donor-Specific Anti-HLA Antibodies and Risk of Primary Graft Failure in Hematopoietic Stem Cell Transplantation.

Detection of donor-specific anti-HLA antibodies (DSA) has been associated with graft rejection in all forms of transplantation. The mechanism by which DSA increase the risk of graft failure remains unclear. We hypothesized that complement-binding DSA are associated with engraftment failure in hematopoietic stem cell transplantation (HSCT) and analyzed 122 haploidentical transplant recipients tested prospectively for DSA. Retrospective analysis to detect C1q binding DSA (C1q+DSA) was performed on 22 allosensitized recipients. Twenty-two of 122 patients (18%) had DSA, 19 of which were women (86%). Seven patients with DSA (32%) rejected the graft. Median DSA level at transplant for patients who failed to engraft was 10,055 mean fluorescence intensity (MFI) versus 2065 MFI for those who engrafted (P = .007). Nine patients with DSA were C1q positive in the initial samples with median DSA levels of 15,279 MFI (range, 1554 to 28,615), compared with 7 C1q-negative patients with median DSA levels of 2471 MFI (range, 665 to 12,254) (P = .016). Of 9 patients who were C1q positive in the initial samples, 5 patients remained C1q positive at time of transplant (all with high DSA levels [median, 15,279; range, 6487 to 22,944]) and experienced engraftment failure, whereas 4 patients became C1q negative pretransplant and all engrafted the donor cells (P = .008). In conclusion, patients with high DSA levels (>5000 MFI) and complement-binding DSA antibodies (C1q positive) appear to be at much higher risk of primary graft failure. The presence of C1q+DSA should be assessed in allosensitized patients before HSCT. Reduction of C1q+DSA levels might prevent engraftment failure in HSCT.