HLA-Class II Artificial Antigen Presenting Cells in CD4+ T Cell-Based Immunotherapy

CD4+ T cells differentiate into various T helper subsets characterized by distinct cytokine secreting profiles that confer them effector functions adapted to a variety of infectious or endogenous threats. Regulatory CD4+ T cells are another specialized subset that plays a fundamental role in the maintenance of immune tolerance to self-antigens. Manipulating effector or regulatory CD4+ T cells responses is a promising immunotherapy strategy for, respectively, chronical viral infections and cancer, or severe autoimmune diseases and transplantation. Adoptive cell therapy (ACT) is an emerging approach that necessitates defining robust and efficient methods for the in vitro expansion of antigen-specific T cells then infused into patients. To address this challenge, artificial antigen presenting cells (AAPCs) have been developed. They constitute a reliable and easily usable platform to stimulate and amplify antigen-specific CD4+ T cells. Here, we review the recent advances in understanding the functions of CD4+ T cells in immunity and in immune tolerance, and their use for ACT. We also describe the characteristics of different AAPC models and the way to improve their stimulating functions. Finally, we discuss the potential interest of these AAPCs, both as fundamental tools to decipher CD4+ T cell responses and as reagents to generate clinical grade antigen-specific CD4+ T cells for immunotherapy

Xénogreffe d'îlots de Langerhans dans le diabète non autoimmun (intérêt du transfert de gène de molécules immunosuppressives dans les modèles porc/rat et rat/souris)

La greffe d'îlots de Langerhans serait pour les patients diabétiques une solution plus physiologique que l'insulinothérapie dont la généralisation sera, malgré son efficacité, limitée par le nombre d'îlots disponibles à partir de pancréas de donneur, et par l'immunosuppression et ses effets secondaires. La xénogreffe d'îlots de porc pourrait remédier à ce problème. De plus, l'étape in-vitro lors de l'isolement des îlots, en fait un modèle intéressant pour l'évaluation de l'ingéniérie génétique des greffons par des vecteurs adénoviraux codant pour des molécules immunosuppressives. Le modèle porc/rat n'a pas permis d'évaluer cette stratégie du fait de l'absence de fonction des greffons malgré les différents agents pharmacologiques associés. Le modèle rat/souris montre que l'inhibition des signaux de costimulation (CTLA4Ig, CD40Ig) retarde efficacement le rejet par expression systémique des vecteurs et non lors de la transduction des îlots. Néanmoins aucune tolérance n'est induite.For diabetic patients, islet transplantation is a more physiological approach compared to insulin injections, however, despite its efficiency, widespread use is limited by donor shortage and immunosuppression related side effects. The use of pig islet xenografts would solve this problem. Futhermore, the possibility of in-vitro manipulation during islet purification makes it an interesting model for graft genetic engineering by adenoviral vectors for recombinant immunosuppressive molecules. Despite the use of immunosuppressive regimens, we were unable to evaluate this strategy via the pig-to-rat model due to the lack of graft finction. In the rat-to-mous e model, the inhibition of costimulatory signals (CTLA4Ig,CD40Ig) efficiently delayed rejection by systemic vector expression but not by islet transduction, although did not result in tolerance.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Induction de tolérance en transplantation par blocage de la voie CD40/CD40L (caractérisation des cellules tolérogènes induites chez le rat et évaluation chez le primate)

Le blocage de la voie de costimulation CD40/CD40L par injection d'un adénovirus codant pour CD40Ig génère des lymphocytes T régulateurs CD8+CD45RClo capables d'induire une tolérance indéfinie d'une allogreffe cardiaque chez le rat. L'étude du transcriptome de ces lymphocytes TCD8+ tolérogènes par puce à ADN a permis d'établir des hypothèses quant aux mécanismes impliqués. Le rôle de l'IFNg est retrouvé et pourrait induire l expression d'une protéine immuno-régulatrice Fgl2. La présence des molécules du CMH de classe II semble également importante. De nombreuses molécules observées dans des analyses de lymphocytes Treg par puces à ADN sont également surexprimées. D autres hypothèses, sont également discutées. Cette stratégie d induction de la tolérance a été évaluée chez le primate en faisant exprimer par des AAV recombinants le CD40Ig humain associé à sc28AT, un inhibiteur de la voie de costimulation CD28/B7. Les molécules sont fonctionnelles in vitro et l injection des animaux par AAV permet une expression prolongée de CD40Ig, mais plus faible et transitoire du sc28AT, qui semble immunogène. Le CD40Ig ne prolonge pas la survie de la greffe contrairement au sc28AT. La survie du greffon d un animal recevant les deux transgènes a été prolongée et d autres animaux sont prévus. L'expression de molécules d intérêt thérapeutique par vecteurs viraux permet de disposer d'un modèle d'évaluation de bioréactifs pour l'induction de la tolérance chez le primate dans des conditions de faisabilité satisfaisantes. L'efficacité des molécules CD40Ig et sc28AT dans ce modèle de transplantation montre les limites de la transposition des modèles rongeurs aux primates.Inhibition of the CD40/CD40L costimulation pathway using an adenovirus coding for CD40Ig can generate CD8+CD45RClo T regulatory cells that induce indefinite graft tolerance in a rat cardiac allograft model. A gene expression study of tolerogenic cells by DNA microarray allowed us to explore the mechanisms involved. As expected, IFNg seems to be a key player and might induce the expression of the immuno-regulatory protein Fgl2. MHC-II molecules seem to be important too. Other molecules observed in other Treg microarray analyses are also over-expressed. Other hypothesis are also discussed.This tolerance induction strategy was evaluated in primates using recombinant AAV coding for the human CD40Ig molecule and/or sc28AT, an inhibitor of the CD28/B7 costimulation pathway. These molecules were functional in vitro. The AAV injection led to a prolonged expression of CD40Ig whereas sc28AT molecule was produced transiently, as it seemed to be immunogenic. Unlike CD40Ig, sc28AT appeared to be efficient in vivo. The animal receiving both transgenes had delayed graft rejection, and other experiments are now scheduled. The expression of therapeutic molecules through viral vectors to evaluate the tolerance induction efficiency in primates is feasible. However the efficiency of the CD40Ig and sc28AT molecules in our model is still debatable and raises the issue of the relevance of rodent models compared to primate pre-clinical strategies.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF

Mécanismes de la lymphopénie radio-induite et implications thérapeutiques

International audienceLa lymphopénie radio-induite est fréquente et peut être profonde et durable. Bien que les lymphocytes soient connus depuis longtemps comme des cellules très radiosensibles, la lymphopénie radique est mal caractérisée. La lymphopénie radio-induite semble affecter différemment les sous-populations de lymphocytes et semble être influencée par les modalités de radiation. La profondeur et la durée de la lymphopénie sont variables selon la localisation de l’irradiation et les volumes de traitement. La lymphopénie radio-induite a été associée à un pronostic plus défavorable dans plusieurs types de tumeurs. Une connaissance plus approfondie de la lymphopénie radio-induite pourrait amener à repenser les modalités de la radiothérapie et à des approches pour restaurer le taux de lymphocytes

Tissue-plasminogen activator effects on the phenotype of splenic myeloid cells in acute inflammation

Abstract Tissue-plasminogen activator (tPA) is a serine protease well known for its fibrinolytic function. Recent studies indicate that tPA could also modulate inflammation via plasmin generation and/or by receptor mediated signalling in vitro. However, the contribution of tPA in inflammatory processes in vivo has not been fully addressed. Therefore, using tPA-deficient mice, we have analysed the effect of lipopolysaccharide (LPS) challenge on the phenotype of myeloid cells including neutrophils, macrophages and dendritic cells (DCs) in spleen. We found that LPS treatment upregulated the frequency of major histocompatibility class two (MHCII+) macrophages but also, paradoxically, induced a deep downregulation of MHCII molecule level on macrophages and on conventional dendritic cells 2 (cDC2). Expression level of the CD11b integrin, known as a tPA receptor, was upregulated by LPS on MHCII+ macrophages and cDC2, suggesting that tPA effects could be amplified during inflammation. In tPA−/− mice under inflammatory conditions, expression of costimulatory CD86 molecules on MHCII+ macrophages was decreased compared to WT mice, while in steady state the expression of MHCII molecules was higher on macrophages. Finally, we reported that tPA deficiency slightly modified the phenotype of DCs and T cells in acute inflammatory conditions. Overall, our findings indicate that in vivo, LPS injection had an unexpectedly bimodal effect on MHCII expression on macrophages and DCs that consequently might affect adaptive immunity. tPA could also participate in the regulation of the T cell response by modulating the levels of CD86 and MHCII molecules on macrophages

HLA-Class II Artificial Antigen Presenting Cells in CD4+ T Cell-Based Immunotherapy

International audienc

CTLA4Ig adenoviral gene transfer induces long-term islet rat allograft survival, without tolerance, after systemic but not local intragraft expression

Genetic engineering using recombinant adenoviruses offers an opportunity to modify islet grafts in order to prevent allograft rejection. We have used an adenovirus coding for CTLA4Ig to compare its efficacy in preventing islet rejection depending on local or systemic production after gene transfer either into the islets or intramuscularly, respectively. Islet allograft survival was also evaluated using recombinant CTLA4Ig administered intraperitoneally or incubated ex vivo with islets prior to transplantation. Transduction of islets with 10(3) or 10(4) plaque-forming units (pfu) per islets of AdCTLA4Ig prolonged islet survival (mean +/- standard deviation [SD] days = 19.5 +/- 5.8 and 19.5 +/- 5.6, respectively, vs. 10.6 +/- 2.4 in control islets, p 60 days) was obtained after intramuscular injection of AdCTLA4Ig that resulted in sustained high levels of circulating CTLA4Ig. Islets incubated in vitro with CTLA4Ig did not show prolonged survival (10.3 +/- 2.5 days). Graft rejection was delayed after one injection of CTLA4Ig (23 +/- 7.6 days, p < 0.003 vs. control). Recipients of long-term surviving grafts after intramuscular AdCTLA4Ig gene transfer were not tolerant because second islet grafts of donor origin were rejected. These recipients also had a strong inhibition of humoral responses against nominal antigens, whereas animals receiving transduced islets showed normal responses. These data demonstrate that local production of CTLA4Ig after gene transfer was as efficient as a single injection of CTLA4Ig in preventing graft rejection. Furthermore, intramuscular gene transfer of CTLA4Ig was the most efficient way to induce long-term islet graft survival but no donor-specific tolerance was induced

Tissue plasminogen activator worsens experimental autoimmune encephalomyelitis by complementary actions on lymphoid and myeloid cell responses.

BACKGROUND Tissue plasminogen activator (tPA) is a serine protease involved in fibrinolysis. It is released by endothelial cells, but also expressed by neurons and glial cells in the central nervous system (CNS). Interestingly, this enzyme also contributes to pathological processes in the CNS such as neuroinflammation by activating microglia and increasing blood-brain barrier permeability. Nevertheless, its role in the control of adaptive and innate immune response remains poorly understood. METHODS tPA effects on myeloid and lymphoid cell response were studied in vivo in the mouse model of multiple sclerosis experimental autoimmune encephalomyelitis and in vitro in splenocytes. RESULTS tPA-/- animals exhibited less severe experimental autoimmune encephalomyelitis than their wild-type counterparts. This was accompanied by a reduction in both lymphoid and myeloid cell populations in the spinal cord parenchyma. In parallel, tPA increased T cell activation and proliferation, as well as cytokine production by a protease-dependent mechanism and via plasmin generation. In addition, tPA directly raised the expression of MHC-II and the co-stimulatory molecules CD80 and CD86 at the surface of dendritic cells and macrophages by a direct action dependent of the activation of epidermal growth factor receptor. CONCLUSIONS Our study provides new insights into the mechanisms responsible for the harmful functions of tPA in multiple sclerosis and its animal models: tPA promotes the proliferation and activation of both lymphoid and myeloid populations by distinct, though complementary, mechanisms

Validation of an anti-α-Gal IgE fluoroenzyme-immunoassay for the screening of patients at risk of severe anaphylaxis to cetuximab

Abstract Background The link between immediate hypersensitivity reactions (HSR) following the first cetuximab infusion and the IgE sensitization against anti-galactose-α-1,3-galactose (α-Gal) is now well-established. An automated Fluoroenzyme-Immunoassay (FEIA) is available and may facilitate the screening of patients with anti-α-Gal IgE before treatment. Methods This study aimed to evaluate its performances as compared to a previously validated anti-cetuximab IgE ELISA, using 185 samples from two previously studied cohorts. Results Despite 21.1% of discrepancies between the two techniques, FEIA discriminated better positive patients and similarly negative ones with a ≥ 0.525 kUA/L threshold. Sensitivity was 87.5% for both tests, specificity was better for FEIA (96.3% vs ELISA: 82.1%). FEIA had a higher positive likelihood ratio (23.9 vs ELISA: 4.89) and a similar negative likelihood ratio (0.13 vs ELISA: 0.15). In our population, the risk of severe HSR following a positive test was higher with FEIA (56.7% vs ELISA: 19.6%) and similar following a negative test (0.7% vs ELISA: 0.8%). Conclusion Although the predictive value of the IgE screening before cetuximab infusion remains discussed, this automated commercial test can identify high-risk patients and is suitable for routine use in laboratories. It could help avoiding cetuximab-induced HSR by a systematic anti-α-Gal IgE screening before treatment