Fayçal Kriaa

Protein A Sepharose immunoadsorption can restore the efficacy of platelet concentrates in patients with Glanzmann's thrombasthenia and anti-glycoprotein IIb-IIIa antibodies

Summary. Type I Glanzmanns thrombasthenia is a rare congenital platelet function disorder, characterized by undetectable platelet membrane glycoprotein IIb–IIIa (GPIIb–IIIa). Severe bleeding is controlled by transfusion of normal platelets, leading in some cases to the occurrence of anti‐GPIIb–IIIa isoantibodies, which induces a loss of transfused platelet efficacy. We used immunoadsorption on protein A Sepharose (IA‐PA), which has been shown to be efficient in decreasing the titre of antibodies in several immune diseases, in three patients with Glanzmanns thrombasthenia and anti‐GPIIb–IIIa isoantibodies on five different occasions. IA‐PA was well tolerated with no deleterious side‐effects reported. It induced a dramatic decrease of total immunoglobulin (Ig)G, including anti‐GPIIb–IIIa isoantibody levels, as assessed by the monoclonal antibody‐specific immobilization of platelet antigens test and the ex vivo inhibition of normal platelet aggregation induced by the patients platelet‐rich or platelet‐poor plasma. Elimination of the antibody was associated with a correction of the bleeding time following platelet transfusion. IA‐PA combined with platelet transfusion made it possible to control two life‐threatening haemorrhages, and allowed two surgical procedures and one bone marrow transplantation to be performed safely. Our experience suggests that IA‐PA, which restores the haemostatic efficacy of platelet transfusion, is a valuable therapeutic strategy in patients with Glanzmanns thrombasthenia and anti‐GPIIb–IIIa isoantibodies.

Protein A sepharose immunoadsorption: immunological and haemostatic effects in two cases of acquired haemophilia

Acquired haemophilia is a life‐threatening disorder caused by circulating auto‐antibodies that inhibit factor VIII coagulant activity (FBIII:C). Immunoadsorption on protein A sepharose (IA‐PA) was performed in two bleeding patients with acquired haemophilia: we observed a dramatic and quick decrease in the anti‐FVIII:C inhibitor titre leading to a normal, albeit transient, haemostatic status. In one case, IA‐PA was the only procedure which succeeded in stopping massive haemorrhage. In the second case, IA‐PA reinforced the haemostatic effect of recombinant activated factor VII by increasing the endogenous plasma factor VIII level. The efficacy of IA‐PA was sustained with immunosuppressive treatment introduced, respectively, 10 and 15 d before the IA‐PA procedures. Our experience with IA‐PA suggests that this extracorporeal anti‐FVIII:C removal procedure is a valuable therapeutic tool for acquired haemophilia and can alleviate life‐threatening haemorrhages.

Long-term results of renal transplantation using kidneys harvested from non-heartbeating donors: A 15-year experience

PURPOSE To expand the pool of suitable organ donors we developed an organ procurement program of non-heartbeating donors during the last 15 years. We compare graft survival in patients receiving renal transplants procured from non-heartbeating with recipients of kidneys from heartbeating donors. MATERIALS AND METHODS From 1986 to 1999, 60 renal transplantations were performed with kidneys harvested from non-heartbeating donors (Mastrich category IV). Kidneys were procured using a double balloon triple lumen catheter inserted into the femoral artery. The 60 kidneys were selected from 70 non-heartbeating donors based on age younger than 50 years, warm ischemia less than 30 minutes, creatinine less than 200 micromol./l., and no hypertension or major histological lesions. Long-term results of graft survival and complications were compared with a series of 1,065 renal transplantations performed during the same period with kidneys procured from heartbeating donors. RESULTS Mean age of the recipients was statistically different as non-heartbeating donors were older. However, the 10-year graft survival rates were similar in both groups (50% versus 53%). Incidence of ureteral stenosis and fistula, arterial stenosis and thrombosis was not statistically different in both groups. On the other hand, delay graft function was more frequent in non-heartbeating donors (60% versus 40%, p = 0.01). CONCLUSIONS Despite a high rate of acute tubular necrosis, kidneys harvested from non-heartbeating donors had the same graft survival rates as those procured from heartbeating donors. Surgical complications were not different. Transplantation of selected kidneys procured from non-heartbeating donors should be promoted as a response to organ shortage.

Protein A immunoadsorption cannot significantly remove the soluble receptor of urokinase from sera of patients with recurrent focal segmental glomerulosclerosis

BACKGROUND Focal segmental glomerulosclerosis (FSGS) is a serious disease, the pathogenesis of which is unknown. Its recurrence after transplantation (Tx) and its partial remission after treatment with immunoadsorption (IA) on a protein A column indicate the existence of a circulating factor responsible for the disease that is able to bind to a protein A column. Recently, the soluble receptor of urokinase (suPAR) was described as the factor responsible for FSGS. We tested the capacity of suPAR to bind to protein A and to be eliminated by IA. METHODS We measured suPAR in eluates of protein A columns from seven patients with recurrent FSGS after Tx (rFSGS) treated with IA, and in the serum of 13 patients with rFSGS and 11 healthy donors (HDs). Additionally, the plasma of these patients was immunoadsorbed in vitro on a protein A Sepharose column, and we quantified suPAR in the eluates and in pre- and post-column samples. RESULTS The concentration of suPAR was higher in the plasma of patients with rFSGS than that of HD patients. However, the concentration of suPAR was similar before and after IA on protein A for the rFSGS and HD samples. The suPAR concentration was very low in the eluates from protein A columns incubated with plasma from HD or rFSGS patients. However, 85% of rFSGS patients showed a decrease in immunoglobulin G and proteinuria. CONCLUSIONS Thus, suPAR does not significantly bind to protein A in vitro or in vivo.

Overview of clinical trials with new agents

PHARMACEUTICAL research has now produced an exciting array of new agents that selectively inhibit calcineurin activity, purine metabolism, IL-2 receptor function, TCR-CD3 receptor function, or cytokine gene transcription. These agents exhibit additive or synergistic effects and are increasingly used in combination to achieve multistep inhibition of lymphocyte activation while minimizing cumulative toxicity.

Immunosuppression advancing in the new millennium: lessons learned from recent multicenter and single center clinical trials

Progress in transplant immunosuppression has occurred in recent years with the emergence of new chemical agents along with new monoclonal antibodies. In this review, recent works are described in tacrolimus/mycophenolate mofetil/sirolimus-based immunosuppression, and also in anti-IL2R monoclonal antibody-based induction. In the light of recent multicenter and single-center clinical trials, several lessons have been learned: less acute rejection, no amelioration of patient/graft survival at short term, and significant side effects are seen with these new agents. On the other hand, several issues need to be solved or confirmed in the future by designing new trials: Are surrogate or other end points for efficacy other than patient/graft survival needed? Will these new agents avoid induction therapy? Will these new agents allow further reduction or replacement of steroids? Could these new agents treat or prevent chronic graft dysfunction? Could the use of nephrotoxic calcineurin inhibitors be limited or avoided? Is individualization of immunosuppressive therapy feasible? In our view, new trials have raised more questions that they have answered. Answering those questions is an exciting challenge for the new millennium.

Belatacept®, une nouvelle molécule originale, immunosuppressive, en transplantation d’organe

354 > En transplantation, d’importants progrès ont été notés depuis la commercialisation des inhibiteurs de la calcineurine (ICN). Les ICN (ciclosporine A et tacrolimus) réduisent l’activation des lymphocytes T alloréactifs (LT) en inhibant le premier signal d’activation, calcium-dépendant. Malheureusement, les ICN ont une toxicité rénale importante [1]. En effet, les malades transplantés d’organes autres que le rein (foie, cœur, intestin, poumon...) développent une insuffisance rénale chronique (IRC) après une dizaine d’années de traitement [2]. En transplantation rénale, les lésions liées à l’utilisation des ICN sont également observées et sont responsables fréquemment de la perte du greffon. L’enjeu actuel est de réduire, voire d’arrêter les ICN. Les nouvelles approches reposent sur la compréhension des mécanismes d’activation des LT et la mise en évidence du second signal d’activation du LT (Figure 1). Cette voie d’activation est nécessaire, mais non suffisante pour l’activation du lymphocyte T, et vient compléter les s i g n a u x t r a n s m i s lors du premier signal. Ce second signal est principalement sous la dépendance de CD28 qui i n t e r a g i t avec deux p r o t é i nes, CD80 et CD86, exprimées à la surface de la cellule présentatrice d’antigène [3]. L’absence du second signal rend le LT anergique. Au cours de l’activation lymphocytaire, un mécanisme de rétrocontrôle négatif est secondairement produit. Il implique la protéine CTLA4, synthétisée secondairement à l’activation par les LT, dont le domaine extracellulaire est homologue à CD28. CTLA4 interagit, avec une avidité supérieure à CD28, avec CD80/86. CTLA4 transmet alors un signal négatif au LT, permettant l’inhibition de la réponse immune. Une nouvelle stratégie est de bloquer le deuxième signal d’activation lymphocytaire en produisant une protéine recombinante humaine composée du domaine extracellulaire de CTLA4 conjugué aux domaines constants d’une IgG1 (CTLA4-Ig) [3] (Figure 2). Deux mutations ponctuelles dans le domaine extracellulaire de CTLA4 ont été identifiées permettant une meilleure avidité pour CD80/86. La protéine recombinante engendrée (Belatacept®) diminue in vitro la prolifération lymphocytaire [3] en dissociant l’interaction CD28-CD80/86. In vivo, dans différents modèles murins, un traitement par CTLA4-Ig associé à un anticorps dirigé contre CD40L induit la survie illimitée des greffons [4-6]. Chez les primates non humains, Belatacept® réduit la survenue de rejet aigu de greffon allogénique et augmente la durée de vie du greffon [7, 8]. Une étude originale de phase II multicentrique randomisée (22 centres, États-Unis, Canada, Europe) a été menée chez 228 malades recevant une greffe rénale [9]. Les malades étaient randomisés en trois groupes. Le groupe I (GI) était traité par NOUVELLE

Therapeutic intervention on preformed anti-HLA antibodies

The presence of broadly reactive antibodies directed at allogeneic lymphocytes is a major and increasing cause of delay in transplantation of patients with end-stage renal disease. In addition, hyperimmunized status is associated with a lower graft success rate that non-immunized status, unless patients were transplanted with excellent matched graft. Hyperimmunized patients represent an increasing proportion of graft waiting list, caused by previous graft failure, pregnancies and blood transfusions.