Antoine Durrbach

Evidence to support the role of HLA-G5 in allograft acceptance through induction of immunosuppressive/ regulatory T cells.

The soluble HLA-G5 isoform encoded by intron-4 retaining spliced transcript has been previously detected in vivo in sera and grafts from transplanted patients who had significantly better graft acceptance. These findings led us to investigate the role of HLA-G5 in tolerance induction in vitro and its biological relevance in allograft acceptance in vivo. We demonstrated that engagement of Ig-like transcript-2 and Ig-like transcript-4 receptors by HLA-G5 is involved in inhibition of T cell alloproliferative responses. Naive T cells sensitized in vitro with HLA-G5, for as little as 18 h, 1) lost their ability to respond to subsequent allogeneic stimulus, and 2) acquired regulatory properties because they inhibited the reactivity of other T cells. These HLA-G5-induced T cells act in an Ag-nonspecific fashion and through soluble factors. Biological relevance was provided by ex vivo analyzes of samples from liver-kidney cotransplanted patients who had high HLA-G5 serum levels and no graft rejection. We showed that addition of HLA-G5-containing sera from these patients inhibited T cell alloresponses and that serum HLA-G5 was responsible for this inhibition. Notably, PBMC from transplanted patients exposed to high levels of circulating HLA-G5 did not respond to allostimulation and inhibited alloreactivity of other T cells. These results demonstrate that HLA-G5-mediated tolerance involves the induction of immunosuppressive T cells. These findings provide evidence supporting the tolerogenic properties of HLA-G and emphasize its potential application as a relevant therapeutic candidate capable of limiting allograft rejection.

Five-Year Safety and Efficacy of Belatacept in Renal Transplantation

Belatacept is a first-in-class co-stimulation blocker in development for primary maintenance immunosuppression. A Phase II study comparing belatacept with cyclosporine (CsA) for prevention of acute rejection and protection of renal function in kidney transplant recipients demonstrated similar efficacy and significantly higher measured GFR at 1 year for belatacept, but the incidence of posttransplantation lymphoproliferative disorder was higher. Here, we present the results for the extension of this trial, which aimed to assess long-term safety and efficacy of belatacept. Seventy-eight of 102 patients who were receiving belatacept and the 16 of 26 who were receiving CsA completed the long-term extension period. GFR remained stable in patients who were receiving belatacept for 5 years, and the incidences of death/graft loss or acute rejection were low. The frequencies of serious infections were 16% for belatacept and 27% for CsA, and neoplasms occurred in 12% of each group. No patients who were treated with belatacept and one patient who was treated with CsA developed posttransplantation lymphoproliferative disorder during the follow-up period. Serious gastrointestinal disorders occurred more frequently with belatacept (12% belatacept versus 8% CsA), and serious cardiac disorders occurred more frequently with CsA (2% belatacept versus 12% CsA). Pharmacokinetic analyses showed consistent exposure to belatacept over time. CD86 receptor saturation was higher in patients who were receiving belatacept every 4 weeks (74%) compared with every 8 weeks (56%). In conclusion, this study demonstrated high patient persistence with intravenous belatacept, stable renal function, predictable pharmacokinetics, and good safety with belatacept over 5 years.

Human leukocyte antigen-G (HLA-G) expression in biliary epithelial cells is associated with allograft acceptance in liver-kidney transplantation

BACKGROUND/AIMS Liver allograft is known to protect simultaneously transplanted organs from acute rejection. We have reported that only 6% of combined liver-kidney recipients, versus 32.5% of kidney recipients, develop kidney graft acute rejection. Release of soluble human leukocyte antigen (HLA) molecules by the liver has been proposed as a possible tolerogenic mechanism involved in the better acceptance of double transplants. The HLA-G molecule is acknowledged to possess tolerogenic properties. METHODS We investigated the involvement of HLA-G in allogeneic transplant acceptance by analyzing its expression in kidney and liver biopsies of 40 combined transplanted patients. RESULTS We demonstrate the presence of HLA-G in 14 out of 40 liver and five out of nine kidney transplants biopsies. HLA-G is expressed de novo by cells that are otherwise frequently susceptible target cells of acute rejection, i.e. liver biliary and renal tubular epithelial cells. We show a significant association between HLA-G expression in liver biliary epithelial cells and the absence of liver graft rejection. No acute or chronic rejection of the kidney graft was observed in patients in whom HLA-G was expressed in the liver graft. CONCLUSIONS HLA-G expression in the liver allograft is associated with a lower frequency of hepatic and renal acute rejection and may be involved in the acceptance of simultaneously transplanted organs.

Urinary cystatin C as a specific marker of tubular dysfunction.

Abstract Background: Cystatin C (CST3), a strong inhibitor of cysteine proteinases, is freely filtered by the kidney glomerulus and is reabsorbed by the tubules, where it is almost totally catabolized, with the remainder then eliminated in urine. In tubular diseases, it seems sensible to postulate that CST3 degradation would be reduced and consequently an increase in its urinary elimination would be observed. Methods: We report here the development of an automatic quantitative assay to measure CST3 concentrations in urine using a Behring N-Latex Cystatin C kit on a BNII laser nephelometer. We tested its clinical relevance on several kidney disease patients. Results: This assay is sensitive (limit of detection 0.008mg/L) and precise (within- and between-day CVs <4%). Reference values for freshly collected urine samples range from 0.03 to 0.18mg/L. Mean urine CST3 concentrations obtained from 52 patients with kidney tubular disease (4.31±3.85mg/L) were significantly higher than those for 60 controls (0.096±0.044mg/L; p<0.0001) and 47 glomerular disease patients (0.106±0.133mg/L; p<0.0001). Conclusion: Increased urinary CST3 concentrations allow the accurate detection of tubular dysfunction among pure and mixed nephropathies. Because of its ability to be processed on automated clinical chemistry analyzers, this assay could easily be used as an adjunct to the standard panel used to screen kidney pathologies, even in emergency situations.

Alloreactive CD4+ and CD8+ T cells express the immunotolerant HLA-G molecule in mixed lymphocyte reactions: in vivo implications in transplanted patients.

HLA‐G displays immunotolerogenic properties towards the main effector cells involved in graft rejection through inhibition of NK‐ and CTL‐mediated cytolysis and CD4+ T cell alloproliferation. HLA‐G expression is restricted in healthy tissues to trophoblast and thymus but is extended to various tissues under pathological conditions. HLA‐G was detected in allograft biopsies and sera from transplanted patients who displayed a better graft acceptance. However, the cells involved in such de novo expression of HLA‐G remain to be characterized. By flow cytometry and confocal microscopy, we demonstrated that, following allogeneic stimulation in vitro, both CD4+ and CD8+ T cell subsets can express membrane‐bound HLA‐G1 and/or soluble HLA‐G5molecules. Such HLA‐G1/‐G5 expression is regulated at the transcriptional level. Soluble HLA‐G5 could be detected by using a novel monoclonal antibody, 5A6G7, specific for the intron 4‐retaining sequence of HLA‐G5. Finally, the biological relevance of these data was provided by analysis of transplanted patients in whom we identified both CD4+ and CD8+ T cells expressing HLA‐G. The HLA‐G‐positive T cells we describe here may constitute a cellular source of HLA‐G after allotransplantation and may be involved in the improved graft acceptance which is observed in HLA‐G‐positive transplanted patients.

Belatacept-Based Regimens Are Associated With Improved Cardiovascular and Metabolic Risk Factors Compared With Cyclosporine in Kidney Transplant Recipients (BENEFIT and BENEFIT-EXT Studies)

Background. Cardiovascular disease, the most common cause of death with a functioning graft among kidney transplant recipients, can be exacerbated by immunosuppressive drugs, particularly the calcineurin inhibitors. Belatacept, a selective co-stimulation blocker, may provide a better cardiovascular/metabolic risk profile than current immunosuppressants. Methods. Cardiovascular and metabolic endpoints from two Phase III studies (BENEFIT and BENEFIT-EXT) of belatacept-based regimens in kidney transplant recipients were assessed at month 12. Each study assessed belatacept in more intensive (MI) and less intensive (LI) regimens versus cyclosporine A (CsA). These secondary endpoints included changes in blood pressure, changes in serum lipids, and the incidence of new-onset diabetes after transplant (NODAT). Results. A total of 1209 patients were randomized and transplanted across the two studies. Mean systolic blood pressure was 6 to 9 mm Hg lower and mean diastolic blood pressure was 3 to 4 mm Hg lower in the MI and LI groups versus CsA (P≤0.002) across both studies at month 12. Non-HDL cholesterol was lower in the belatacept groups versus CsA (P<0.01 MI or LI vs. CsA in each study). Serum triglycerides were lower in the belatacept groups versus CsA (P<0.02 MI or LI vs. CsA in each study). NODAT occurred less often in the belatacept groups versus CsA in a prespecified pooled analysis (P<0.05 MI or LI vs. CsA). Conclusions. At month 12, belatacept regimens were associated with better cardiovascular and metabolic risk profiles, with lower blood pressure and serum lipids and less NODAT versus CsA. The overall profile of belatacept will continue to be assessed over the 3-year trials.

Soluble HLA-G Inhibits Cell Cycle Progression in Human Alloreactive T Lymphocytes

HLA-G is involved in regulating T cell responses. Various mechanisms have been proposed to explain the inhibition of T cell proliferation. In this context, the possible role of HLA-G in cell cycle regulation remains to be explored. Using stably transfected M8 cells expressing the secreted isoform (HLA-G5) of HLA-G, we investigated the role of HLA-G in inducing apoptosis and in controlling the cell cycle of activated T cells. Soluble HLA-G (HLA-G5) inhibited both CD4 and CD8 T cell proliferation. However, HLA-G5 did not induce T cell apoptosis, as determined by 3,3′-diethyloxacarbocyanine and propidium iodine labeling. It induced accumulation of the retinoblastoma protein, but not its phosphorylated and active form. Treatment of activated T cells with HLA-G5 also reduced the amounts of cyclin D2, E, A, and B by >80%. In contrast, it induced an accumulation of p27kip, but not p21cip, in activated T cells. HLA-G does not induce apoptosis of alloreactive T cells, but induces p27kip1 and inhibits cell cycle progression.

Risk factors and long-term outcome of transplant renal artery stenosis in adult recipients after treatment by percutaneous transluminal angioplasty.

Transplant renal artery stenosis (TRAS) is a common complication of kidney transplantation but attempts to identify predisposing risk factors for TRAS have yielded conflicting results. In order to determine the predisposing factors for transplant (TRAS), we retrospectively reviewed the records of 29 renal allograft recipients with TRAS treated with percutaneous transluminal angioplasty (PTA). The TRAS group was compared with a case‐control group of 58 patients. Predisposing factors for TRAS included CMV infection (41.4% vs. 12.1% p = 0.0018) and initial delayed graft function (DGF) (48.3% vs. 15.5% p = 0.0018), respectively in the TRAS and the control group. Acute rejection occurred more frequently in patients from the TRAS group (48.3%) compared with the control group (27.6%), although the difference was not significant (p = 0.06). In a multivariate analysis, only CMV infection (p = 0.005) and DGF (p = 0.009) appear to be significantly and independently associated with TRAS. The long‐term graft survival was significantly higher in the control group, compared with the TRAS group (p = 0.03). Our study suggests that CMV infection and DGF are two reliable risk factors for TRAS. Despite treatment by PTA with primary successful results, TRAS significantly affects long‐term graft outcome.

Critical care management and outcome of severe Pneumocystis pneumonia in patients with and without HIV infection

BackgroundLittle is known about the most severe forms of Pneumocystis jiroveci pneumonia (PCP) in HIV-negative as compared with HIV-positive patients. Improved knowledge about the differential characteristics and management modalities could guide treatment based on HIV status.MethodsWe retrospectively compared 72 patients (73 cases, 46 HIV-positive) admitted for PCP from 1993 to 2006 in the intensive care unit (ICU) of a university hospital.ResultsThe yearly incidence of ICU admissions for PCP in HIV-negative patients increased from 1993 (0%) to 2006 (6.5%). At admission, all but one non-HIV patient were receiving corticosteroids. Twenty-three (85%) HIV-negative patients were receiving an additional immunosuppressive treatment. At admission, HIV-negative patients were significantly older than HIV-positive patients (64 [18 to 82] versus 37 [28 to 56] years old) and had a significantly higher Simplified Acute Physiology Score (SAPS) II (38 [13 to 90] versus 27 [11 to 112]) but had a similar PaO2/FiO2 (arterial partial pressure of oxygen/fraction of inspired oxygen) ratio (160 [61 to 322] versus 183 [38 to 380] mm Hg). Ventilatory support was required in a similar proportion of HIV-negative and HIV-positive cases (78% versus 61%), with a similar proportion of first-line non-invasive ventilation (NIV) (67% versus 54%). NIV failed in 71% of HIV-negative and in 13% of HIV-positive patients (p < 0.01). Mortality was significantly higher in HIV-negative than HIV-positive cases (48% versus 17%). The HIV-negative status (odds ratio 3.73, 95% confidence interval 1.10 to 12.60) and SAPS II (odds ratio 1.07, 95% confidence interval 1.02 to 1.12) were independently associated with mortality at multivariate analysis.ConclusionThe yearly incidence of ICU admissions for PCP in HIV-negative patients in our unit increased from 1993 to 2006. The course of the disease and the outcome were worse in HIV-negative patients. NIV often failed in HIV-negative cases, suggesting that NIV must be watched closely in this population.

Primary brain lymphomas after kidney transplantation: presentation and outcome.

Background. Non-Hodgkin’s lymphoma is the second most frequent neoplasia following solid-organ transplantation. The objective of this study is to describe the clinical, histologic, and radiologic features of primary posttransplantation brain lymphomas (PTBL) in addition to their outcome. Methods. Twenty-five kidney transplant patients with histologically proven PTBL from 11 French centers were retrospectively investigated. Results. Immunosuppressive regimen included induction with antithymocyte globulins (ATG) in 20 patients. Median overall delay between transplantation and lymphoma was 18 months (4–264). Six of 10 patients with late posttransplantation brain lymphomas (PTBL) occurrence (>3 years) had been recently switched from azathioprine to mycophenolate mofetil (median switch lymphoma delay 14 months). Cerebral computed tomography (CT) scans and magnetic resonance imaging (MRI) revealed multifocal lesions (n=18), with a ring contrast enhancement (n=20) similar to cerebral abscesses, as observed in HIV-related brain lymphomas. Histology showed large B-cell non-Hodgkin’s lymphoma in 87.5% of cases; Epstein-Barr virus (EBV) was detected in 95%. After lymphoma diagnosis, immunosuppressive treatment was reduced in all patients, and all but one received complementary treatment by surgery (n=2), anti-CD21 antibodies (n=2), chemotherapy including high-dose intravenous methotrexate (n=7), encephalic radiotherapy (n=5), or chemotherapy plus radiotherapy (n=8). Median overall survival was 26 months. Patients with a radiotherapy-based regimen seemed to have a longer survival (36 vs. 7 months, P <0.005). Conclusions. Our study showed that PTBL are EBV-induced large B-cell lymphomas, which mimic cerebral abscesses on imaging and whose occurrence may be influenced by immunosuppression modifications. Treatment by radiotherapy is associated with better survival.