Cell Immune Tolerance Research Articles

Abstract 4723: Targeting the IDO and TDO pathway through inhibition of the aryl hydrocarbon receptor

Abstract Though checkpoint inhibitors have become the cornerstone of immune-based oncology therapy, the majority of cancer patients do not benefit from these agents. Resistance to checkpoint inhibitors is due in part to the presence of immunosuppressive molecules which prevent immune activation despite T cell checkpoint inhibition. One such immunosuppressive molecule is kynurenine. Kynurenine, metabolized from tryptophan by indoleamine-pyrrole 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2), binds to the Aryl hydrocarbon receptor (AHR) in multiple immune cell types which leads to a net immunosuppressive environment. IDO1 inhibitors combined with checkpoint inhibitors have led to substantial clinical benefit in early clinical trials, validating disruption of the kynurenine pathway as a therapeutic strategy and substantiating that metabolites within human cancers induce immune cell tolerance. Given that kynurenine can be synthesized by both IDO1 and TDO2 and that AHR is activated by endogenous ligands other than kynurenine, AHR inhibition provides a novel approach to reverse immunosuppression in a broad range of tumor types. We will present data demonstrating that AHR antagonism can affect multiple immune cell types within the tumor microenvironment, reverse immune suppression and lead to tumor growth inhibition in tumor models. In addition, AHR inhibition combined with checkpoint inhibitors leads to enhanced anti-tumor activity and improved survival in these models relative to either agent alone. Kynurenine can lead to increased levels of many immunosuppressive cytokines including IL22 in human T-cells which is reversed with AHR inhibition. In addition, we have previously shown that kynurenine addition during T-cell maturation leads to a more quiescent T-effector cells while AHR antagonism during maturation maintains T-cells in a more naïve-like, T-central memory state. In vivo studies in the B16 and the B16-IDO overexpressing models demonstrate that kynurenine-mediated activation of the AHR pathway leads to faster tumor growth and a more immunosuppressive tumor microenvironment, with FOXP3 T-cells playing a major role. There are also more suppressive myeloid cells in the IDO overexpressing model. AHR antagonism inhibits growth in the B16-IDO model and reverses the immunosuppressive microenvironment as indicated by changes in T cell and myeloid cell populations as well as AHR-dependent gene expression. Similar activity is also seen in the CT26 model. In addition, enhanced tumor growth inhibition and survival benefit is seen in combination with checkpoint inhibitors. Our data indicate that AHR is a viable target for reversing immune suppression in the tumor microenvironment and could have activity in many tumor types due to activation via kynurenine and multiple other potential ligands. Citation Format: Jeremy Tchaicha, Karen McGovern, Luis Felipe Campesato, Silvia Coma, Xiaoyan Michelle Zhang, Meghan Walsh, Jill Cavanaugh, Taha Merghoub, Jedd Wolchok, Mark Manfredi. Targeting the IDO and TDO pathway through inhibition of the aryl hydrocarbon receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4723.

Protective action of bone marrow mesenchymal stem cells in immune tolerance of allogeneic heart transplantation by regulating CD45RB+ dendritic cells.

Bone marrow-derived mesenchymal stem cells (BMSCs) could exert a potent immunosuppressive effect and therefore may have a therapeutic potential in T-cell-dependent pathologies. We aimed to examine the effects of BMSCs on immune tolerance of allogeneic heart transplantation and the involvement of CD45RB+ dendritic cells (DCs). Bone marrow-derived DCs and BMSCs were co-cultured, with CD45RB expression on the surface of DCs measured by flow cytometry. qRT-PCR and Western blotting were used to detect mRNA and protein levels. Cytometric bead array was performed to determine the serum level of IL-10. Survival time of transplanted heart and expression of CD4+ , CD8+ , IL-2, IL-4, IL-10, IFN-γ were determined. Immunofluorescence assay was employed to determine intensity of C3d and C4d. DCs co-cultured with BMSCs showed increased CD45RB and Foxp3 levels. CD45RB+ DCs co-cultured with T-cells CD4+ displayed increased T-cell CD4+ Foxp3 ratio and IL-10 than DCs. Both of them extended survival time of transplanted heart, decreased histopathological classification and score, intensity of C3d, C4d, proportion of CD4+ , expression levels of IL-2 and IFN-γ, and increased the CD4+ Foxp3 ratio and levels of IL-4 and IL-10. CD45RB+ DCs achieved better protective effects than DCs. BMSCs increased the expression of CD45RB in the bone marrow-derived DCs, thereby strengthening immunosuppression capacity of T cells and immune tolerance of allogeneic heart transplantation.

Oestrogen, an evolutionary conserved regulator of T cell differentiation and immune tolerance in jawed vertebrates?

In teleosts, as in mammals, the immune system is tightly regulated by sexual steroid hormones, such as oestrogens. We investigated the effects of 17β-oestradiol on the expression of several genes related to T cell development and resulting T cell subpopulations in sea bass, Dicentrarchus labrax, for a primary lymphoid organ, the thymus, and two secondary lymphoid organs, the head-kidney and the spleen. In parallel, the oxidative burst capacity was assessed in leucocytes of the secondary lymphoid organs. Apoptosis- and proliferation-related genes, indicative of B and T cell clonal selection and lymphoid progenitor activity, were not affected by elevated oestrogen-levels. Sex-related oestrogen-responsiveness in T cell and antigen-presenting cell markers was observed, the expression of which was differentially induced by oestrogen-exposure in the three lymphoid organs. Remarkably, in the spleen, oestrogen increased regulatory T cell-related gene expression was associated with a decrease in oxidative burst capacity. To the best of our knowledge, this study indicates for the first time that physiological levels of oestrogen are likely to promote immune tolerance by modulating thymic function (i.e., T cell development and output) and peripheral T cells in teleosts, similar to previously reported oestrogenic effects in mammals.

Exosomes in Nasopharyngeal Carcinoma.

Exosomes are nanosized (30-100nm) membrane microvesicles secreted through a complex cellular process. Exosomes contain a variety of bioactive molecules, such as proteins, microRNAs(miRNAs or miRs) and long non-coding RNAs (lncRNAs), playing an important role in the cell-to-cell substance transportation and signal transduction. Nasopharyngeal carcinoma-related exosomes (NPC-Exo) have been identified in circulating blood and contribute to tumor cell proliferation, angiopoiesis, and immune tolerance through remodeling of tumor microenvironment (TME). Nasopharyngeal carcinoma-related exosomes may also induce epithelial-mesenchymal transition (EMT), thus promoting tumor metastasis and chemoradioresistance. Clinically, the exosomes may serve as novel biomarkers for diagnosis and targeted therapies of nasopharyngeal carcinoma. This review article updates the understanding of exosomes in nasopharyngeal carcinoma(NPC).

Indoleamine 2,3-dioxygenase and inducible nitric oxide synthase mediate immune tolerance induced by CTLA4Ig and anti-CD154 hematopoietic stem cell transplantation in a sensitized mouse model

Cytotoxic T-lymphocyte-associated protein 4 immunoglobulin (CTLA4Ig) and anti-cluster of differentiation 154 (anti-CD154) are able to block B7/CD28 and CD40/CD154 co-stimulatory signals in T cells. Additionally, they promote hematopoietic stem cell transplantation (HSCT) in sensitized recipients and are able to induce immune tolerance and complete hematopoietic reconstitution. Indoleamine 2, 3-dioxygenase (IDO) and nitric oxide (NO) have been implicated in T cell immune tolerance. The aim of the present report was to study the in vivo tolerogenic mechanisms by which CTLA4Ig and anti-CD154 induce transplantation survival in mice receiving HSCT. BALB/c mice were sensitized via splenocyte transfusion and pretreated with CTLA4Ig plus anti-CD154 on day-7. IDO and inducible nitric oxide synthase (iNOS) inhibitors were applied on days-7 to 0 and the mice were divided into 4 groups (n=10) and injected with IDO every other day. The mice were sacrificed on day 0, and splenocytes were separated to identify CD11c+ antigen-presenting cells, which were subsequently assessed for IDO expression and activity. The concentration of NO was tested using a nitrate reductase kit. Following the acceptance of allogeneic HSCT, mice were tested for homing and engraftment, as well as survival rate. Application of the IDO inhibitor increased the concentration of NO, whereas a decrease in NO resulted in increased IDO activity. Immune tolerance was abrogated in the presence of both IDO and iNOS inhibitors, whereas this effect was not observed with either compound alone. CTLA4Ig and anti-CD154 may induce immune tolerance by affecting the activity of IDO and iNOS. This tolerance was abrogated in the presence of both IDO and iNOS inhibitors. A cross-regulatory pathway was observed between the IDO and NO pathways, in which the inhibition of IDO stimulated the iNOS pathway and vice versa.

Sinulariolide suppresses LPS‑induced phenotypic and functional maturation of dendritic cells.

The dendritic cell (DC) maturation process is essential for the development of T cell responses and immune tolerance. Accordingly, DCs are considered a major target in the development of immunomodulating agents. In the present study, the effect of sinulariolide, an active compound isolated from the cultured soft coral Sinularia flexibilis, on lipopolysaccharide (LPS)‑induced murine bone marrow‑derived DCs was evaluated. The different phenotypes, cytokine secretion and the mix‑lymphocyte reaction of DCs were detected using flow cytometry and ELISA. The experimental results revealed that the phenotypic and functional maturation of DCs stimulated by LPS were markedly reduced by sinulariolide in a concentration‑dependent manner, including the expression of co‑stimulatory molecules (CD40, CD80 and CD86). In addition, sinulariolide reduced the release of tumor necrosis factor‑α, interleukin (IL)‑6, IL‑12 and nitric oxide from the LPS‑activated DCs, decreased their abilities to stimulate allogeneic T cell proliferation, and inhibited LPS‑induced nuclear factor‑κB pathways. These findings offer novel insight into the immunopharmacological function of sinulariolide and its effects on DCs.

The Importance of Dendritic Cells in Maintaining Immune Tolerance.

Immune tolerance is necessary to prevent the immune system from reacting against self, and thus to avoid the development of autoimmune diseases. In this review, we discuss key findings that position dendritic cells (DCs) as critical modulators of both thymic and peripheral immune tolerance. Although DCs are important for inducing both immunity and tolerance, increased autoimmunity associated with decreased DCs suggests their nonredundant role in tolerance induction. DC-mediated T cell immune tolerance is an active process that is influenced by genetic variants, environmental signals, as well as the nature of the specific DC subset presenting Ag to T cells. Answering the many open questions with regard to the role of DCs in immune tolerance could lead to the development of novel therapies for the prevention of autoimmune diseases.

Role of dendritic cell maturation factors produced by human invariant NKT cells in immune tolerance.

In this study, we used the culture supernatant of iNKT cells to identify human myeloid DC maturation factors produced by human CD4+ iNKT cells. S100A8 had a strong maturation effect. Notably, the recombinant S100A8 protein displayed properties of DC maturation functioning, and the induction of DC differentiation by both the purified and the recombinant protein were blocked by anti-S100A8 and anti-TLR-4 mAbs. DC differentiation induced by anti-major histocompatibility complex class II/CD1d Ab, S100A8, or both was qualitatively indistinguishable from that induced by the coculture of DCs and iNKT cells or via culture supplementation with supernatants from activated CD4+ iNKT cells. S100A8 also induced CD4+/CD25+/Foxp3+ Treg cells from naïve T cells. S100A8 may contribute to DC differentiation by elevating transcription factors or activating transcription factor-2, heat shock factor-1, or both, in mature DCs. S100A8 is a novel candidate iNKT cell-dependent DC maturation factor.

Immune Tolerance Mediated by TIM-3,LAG-3 and BTLA and Their Reversion in Hematological Malignancies-Review

The main mechanism of tumor immune suppression is due to the T cell exhaustion which is mediated by abnormal expression of T-cell immunosuppressive receptors in immune cells. Blocking these molecules may restore partial or all functions of T cells. This article reviews the advance on the role of the newly discovered T cell immuno-suppressive receptors such as TIM-3, LAG-3 and BTLA, including their mediated T cell-immune tolerance and the study of targeted immunotherapy in hematological malignancies, so as to provide the new strategy for immune-targeted therapy for hematological malignancies.

The effect of dietary phytoestrogen content on the development of systemic lupus erythematosus in the MRL/lpr mouse.

Abstract Systemic lupus erythematosus is a prototypical autoimmune disease, characterized by the loss of immune cell tolerance to self-antigens, and the subsequent production of autoantibodies leading to multi-organ damage. SLE is an incurable, highly variable autoimmune disease that most often affects women of child-bearing age. We investigated the effects of three standard commercial diets with varying phytoestrogen content on the development of lupus in female MRL/lpr mice. The diets include Harlan 2018 which contains soybean meal, Teklad 7013 which contains both soy and alfalfa, and Research Diets Inc. D11112226 (RD) purified ingredients diet, containing no measurable phytoestrogens. Mice fed the 2018 diet developed severe glomerulonephritis with high levels of complement C3 protein deposition and moderate IgG immune-complex deposition, while mice fed the RD diet developed minimal evidence of renal damage and protein deposition. The mice fed the RD diet, however, had increased levels of multiple pro-inflammatory cytokines, while immune cell populations remained unchanged. Immunofluorescence revealed distinct infiltrating cellular phenotypes in the kidney, dependent on dietary source. Splenocyte miRNA-148a was markedly elevated in mice fed the 2018 and 7013 diets, while circulating miRNA values were not statistically different. Our results suggest that dietary isoflavones can worsen the development of glomerulonephritis due to enhanced immune complex protein deposition and altered cellular infiltration phenotypes. Our results also support that each organ system must be evaluated independently, and that what is measured in circulation does not necessarily reflect what is occurring in disease target organs.

Matrine derivate MASM suppresses LPS-induced phenotypic and functional maturation of murine bone marrow-derived dendritic cells

Dendritic cell (DC) maturation process is a crucial step for the development of T cell immune responses and immune tolerance. In this study, we evaluated MASM, a novel derivative of the natural compound matrine that possesses a significant anti-inflammatory and immune-regulating property, for its efficacy to inhibit lipopolysaccharides (LPS)-induced maturation of murine bone marrow-derived dendritic cells. Here we show that MASM profoundly suppresses LPS-induced phenotypic and functional DC maturation. MASM inhibited LPS-induced expression of costimulatory molecules CD80 and CD86 in a concentration-dependent manner. MASM also attenuated LPS-induced IL-12p70, TNF-α, IL-6 and NO release of DCs. The MASM-treated DCs were highly efficient at antigen capture via mannose receptor-mediated endocytosis but showed weak stimulatory capacity for allogeneic T cell proliferation. Furthermore, MASM inhibited LPS-induced PI3K/Akt, MAPK and NF-κB pathways. These novel findings provide new insight into the immunopharmacological role of MASM in impacting on the DCs.

Erythropoeitin Signaling in Macrophages Promotes Dying Cell Clearance and Immune Tolerance

The failure of apoptotic cell clearance is linked to autoimmune diseases, nonresolving inflammation, and developmental abnormalities; however, pathways that regulate phagocytes for efficient apoptotic cell clearance remain poorly known. Apoptotic cells release find-me signals to recruit phagocytes to initiate their clearance. Here we found that find-mesignal sphingosine 1-phosphate (S1P) activated macrophage erythropoietin (EPO) signaling promotedapoptotic cell clearance and immune tolerance. Dyingcell-released S1P activated macrophage EPOsignaling. Erythropoietin receptor (EPOR)-deficient macrophages exhibited impaired apoptotic cell phagocytosis. EPO enhanced apoptotic cell clearance through peroxisome proliferator activated receptor-γ (PPARγ). Moreover, macrophage-specific Epor(-/-) mice developed lupus-like symptoms, and interference in EPO signaling ameliorated the disease progression in lupus-like mice. Thus, we have identified a pathway that regulates macrophages to clear dying cells, uncovered the priming function of find-me signal S1P, and found a role of the erythropoiesis regulator EPO in apoptotic cell disposal, with implications for harnessing dying cell clearance.

Surface Antigen Profiling of Helicobacter pylori-Infected and -Uninfected Gastric Cancer Cells Using Antibody Microarray.

Comprehensive immunophenotyping cluster of differentiation (CD) antigens in gastric adenocarcinoma, specifically between Helicobacter pylori-infected and -uninfected gastric cancer patients by using DotScan(™) antibody microarray has not been conducted. Current immunophenotyping techniques include flow cytometry and immunohistochemistry are limited to the use of few antibodies for parallel examination. We used DotScan(™) antibody microarray consisting 144 CD antibodies to determine the distribution of CD antigens in gastric adenocarcinoma cells and to elucidate the effect of H. pylori infection toward CD antigen expression in gastric cancer. Mixed leukocytes population derived from gastric adenocarcinoma patients were immunophenotyped using DotScan(™) antibody microarray. AGS cells were infected with H. pylori strains and cells were captured on DotScan(™) slides. Cluster of differentiation antigens involved in perpetuating the tolerance of immune cells to tumor cells was upregulated in gastric adenocarcinoma cells compared to normal cells. CD279 which is essential in T cells apoptosis was found to be upregulated in normal cells. Remarkably, H. pylori-infected gastric cancer patients exhibited upregulated expression of CD27 that important in maintenance of T cells. Infection of cagA+ H. pylori with AGS cells increased CD antigens expression which involved in cancer stem cell while cagA- H. pylori polarized AGS cells to express immune-regulatory CD antigens. Increased CD antigens expression in AGS cells infected with cagA+ H. pylori were also detected in H. pylori-infected gastric cancer patients. This study suggests the tolerance of immune system toward tumor cells in gastric cancer and distinct mechanisms of immune responses exploited by different H. pylori strains.

Ex Vivo Modulation of Donor Cells Results in Enhanced Survival and Reduced Gvhd Mortality

Allogeneic hematopoietic stem cell transplant (HSCT) represents a potential curative treatment for a number of life-threatening blood malignancies. The utility of this treatment regimen, however, is limited by a number of serious complications including graft versus host disease, which occurs in approximately half of all transplant patients. Standard-of-care for treating acute GvHD has remained unchanged for several decades and consists of high doses of steroids, which are only effective in approximately 35 percent of the cases. Therefore, the reduction of GvHD represents a large unmet medical need, and new approaches are needed to effectively attenuate GvHD. Here we present a fundamentally novel strategy for potentially reducing GVHD - by modulating donor mobilized peripheral blood cells with small molecules prior to HSCT, a programmed mobilized peripheral blood (mPB) allogeneic graft, with reduced T-cell alloreactivity, can be administered as the hematopoietic cell source for HSCT.To this end, we applied our screening platform to identify a combination of small molecule modulators (FT1050, FT4145) that promote the activation of genes implicated in cell cycle, immune tolerance and anti-viral properties of T cells, as well as in the survival, proliferation and engraftment potential of CD34+ cells. Genome-wide expression analysis of the T-cell compartment of mobilized peripheral blood following treatment with FT1050+FT4145 revealed the induction of genes involved in cell cycle (e.g., CCND1, CCNE1), immune tolerance (e.g., ALDH, AREG) and anti-viral properties (e.g., EFNB2). To further assess the therapeutic impact of ex vivo programming with FT1050 and FT4145, a number of T cell assays to assess T cell phenotype and function were conducted on mPB. Overall, ex vivo programming of mPB resulted in reduced allogeneic T cell responses and was accompanied by reduced capacity of modulated T cells to produce Interferon Gamma (IFN-ɣ). Concomitantly, the ability of the modulated T cells to make Interleukin 4 (IL-4) and 10 (IL-10) was enhanced, suggesting a polarization of these cells towards a less inflammatory functional state. This was further evidenced by increased surface expression of an immune-inhibitory molecule, PD1, and reduced expression of the activation markers 41BB and ICOS.We next examined the potential beneficial role of ex vivo programming with FT1050+FT4145 in a major histocompatibility complex (MHC) mis-matched HSCT mouse model. Briefly, lethally irradiated BALB/c mice received bone marrow and splenocytes from C57BL/6 donor mice pulse treated with vehicle or FT1050+FT4145. Significantly less GvHD, as determined by survival, weight loss, GVHD score (diarrhea, inactivity, hunched posture, ruffled fur, eye lesion, snout swelling/skin integrity), cytokine production and histopathology of GvHD target organs was observed in recipients receiving FT1050+FT4145 treated cells as compared to those receiving vehicle treated cells. In addition, we observed increased levels of donor T regulatory cells (Tregs) in secondary lymphoid organs concomitant with decreased levels of circulating IFN-ɣ in recipients receiving FT1050+FT4145 treated cells. Based on the attenuation of alloreactive T-cell responses in these preclinical studies, we believe our findings provide a compelling scientific basis to support the clinical evaluation of ex vivo programmed mobilized peripheral blood in patients undergoing HSCT for the treatment of hematologic malignancies. DisclosuresLevin:Fate Therapeutics, Inc: Employment, Equity Ownership. Shoemaker:Fate Therapeutics Inc: Employment.

Down-expression of miR-152 lead to impaired anti-tumor effect of NK via upregulation of HLA-G.

It is known that chronic HBV infection (CHB) is the major risk factor for hepatocellular carcinoma (HCC) because CHB could not only cause liver tumorigenesis but also lead to change of local microenviroment and lower immune response to infected and cancerous cells (immune tolerance). Human leucocyte antigen-G (HLA-G) belongs to a non-classic MHC-I family and was considered to be an immune tolerance molecule, which could bind to immunosuppressive receptors of natural killer cell (NK) and T cells and trigger immunosuppressive signaling. Recently, numerous studies highlighted that microRNAs (miRNAs) were significantly differentially expressed in HCC tumorigenesis, and the expression was tissue-specific, indicating that miRNAs may cause great epigenetic changes in HCC tumorigenesis. In this study, we found that the expression of HLA-G was upregulated by hepatitis B virus (HBV) infection and miR-152; a HLA-G-targeting miRNA was downregulated by HBV infection. And high expression of HLA-G further suppressed NK against cancer cells, providing a new concept that miR-152 was involved in HBV-induced hepatocellular carcinoma.

Contribution of dendritic cells to the autoimmune pathology of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a heterogeneous disease in which excessive inflammation, autoantibodies and complement activation lead to multisystem tissue damage. The contribution of the individual genetic composition has been extensively studied, and several susceptibility genes related to immune pathways that participate in SLE pathogenesis have been identified. It has been proposed that SLE takes place when susceptibility factors interact with environmental stimuli leading to a deregulated immune response. Experimental evidence suggests that such events are related to the failure of T-cell and B-cell suppression mediated by defects in cell signalling, immune tolerance and apoptotic mechanism promoting autoimmunity. In addition, it has been reported that dendritic cells (DCs) from SLE patients, which are crucial in the modulation of peripheral tolerance to self-antigens, show an increased ratio of activating/inhibitory receptors on their surfaces. This phenotype and an augmented expression of co-stimulatory molecules is thought to be critical for disease pathogenesis. Accordingly, tolerogenic DCs can be a potential strategy for developing antigen-specific therapies to reduce detrimental inflammation without causing systemic immunosuppression. In this review article we discuss the most relevant data relative to the contribution of DCs to the triggering of SLE.

In vivo induction of regulatory T cells for immune tolerance in hemophilia

Current therapy for the X-linked coagulation disorder hemophilia is based on intravenous infusion of the specifically deficient coagulation factor. However, 20–30% of hemophilia A patients (factor VIII, FVIII, deficiency) generate inhibitory antibodies against FVIII. While formation of inhibitors directed against factor IX, FIX, resulting from hemophilia B treatment is comparatively rare, a serious complication that is often associated with additional immunotoxicities, e.g. anaphylaxis, occurs. Current immune tolerance protocols to eradiate inhibitors are lengthy, expensive, not effective in all patients, and there are no prophylactic tolerance regimens to prevent inhibitor formation. The outcomes of recent experiments in animal models of hemophilia demonstrate that regulatory CD4+ T cells (Treg) are of paramount importance in controlling B cell responses to FVIII and FIX. This article reviews several novel strategies designed to in vivo induce coagulation factor-specific Treg cells and discusses the subsets of Treg that may promote immune tolerance in hemophilia. Among others, drug- and gene transfer-based protocols, lymphocyte transplant, and oral tolerance are reviewed.

Advance in targeted immunotherapy for hematological malignancies based on immunosuppressive receptors

T cell immune deficiency results in inefficient anti-tumor immune response in most patients with hematological malignancies, thereby tumor cells escaping the attack of host immune system, that is the immune escape of tumor cells. Recently, new insights regard to the CD8+ T cell exhaustion which is one of the most important mechanisms of tumor immune suppression. The CD8+ T cell exhaustion is mediated by abnormal expression of T-cell immunosuppressive receptors such as PD-1 and CTLA-4. Blocking these molecules may restore the partial or all functions of T cells. This article reviewed the advances on the role of the PD-1 and CTLA-4 in hematological malignancies, including their functions on mediating T cell-immune tolerance and the progression of targeted immunotherapy, to provide the new strategy for hematological malignancies. Key words: Hematological malignancies; PD-1; CTLA-4; PD-L1; Molecular targeted therapy

FR104, an Antagonist Anti-CD28 Monovalent Fab’ Antibody, Prevents Alloimmunization and Allows Calcineurin Inhibitor Minimization in Nonhuman Primate Renal Allograft

Selective targeting of CD28 might represent an effective immunomodulation strategy by preventing T cell costimulation, while favoring coinhibition since inhibitory signals transmitted through CTLA-4; PD-L1 and B7 would not be affected. We previously showed in vitro and in vivo that anti-CD28 antagonists suppress effector T cells while enhancing regulatory T cell (Treg) suppression and immune tolerance. Here, we evaluate FR104, a novel antagonist pegylated anti-CD28 Fab' antibody fragment, in nonhuman primate renal allotransplantation. FR104, in association with low doses of tacrolimus or with rapamycin in a steroid-free therapy, prevents acute rejection and alloantibody development and prolongs allograft survival. However, when FR104 was associated with mycophenolate mofetil and steroids, half of the recipients rejected their grafts prematurely. Finally, we observed an accumulation of Helios-negative Tregs in the blood and within the graft after FR104 therapy, confirmed by Treg-specific demethylated region DNA analysis. In conclusion, FR104 reinforces immunosuppression in calcineurin inhibitor (CNI)-low or CNI-free protocols, without the need of steroids. Accumulation of intragraft Tregs suggested the promotion of immunoregulatory mechanisms. Selective CD28 antagonists might become an alternative CNI-sparing strategy to B7 antagonists for kidney transplant recipients.

Enhanced immune response to hepatitis B vaccination through immunization with a Pre-S1/Pre-S2/S vaccine.

Efficacy and safety of recombinant yeast-derived hepatitis B vaccines for prevention of hepatitis B have been demonstrated unequivocally worldwide as reflected in reduction in HBsAg carrier rates and hepatocellular carcinoma. A new generation of recombinant HBV vaccines expressed in mammalian cells containing Pre-S/S epitopes has been developed in several countries. Such vaccines are useful in special risk groups, i.e., in non-responders to conventional HBV vaccines including older adults, obese people, health care workers, patients with renal failure and on dialysis, transplant patients, patients with HIV as well as travelers on short notice to HBV endemic regions. The future of such vaccines depends on their enhanced immunogenicity and cost profile. Sci-B-Vac™ is a mammalian cell-derived recombinant Pre-S1/Pre-S2/S hepatitis B vaccine which has been shown to be highly immunogenic, inducing faster and higher seroprotection rates against HBV with higher anti-HBs levels at lower HBsAg doses as compared to conventional yeast-derived vaccines. Recently, it has been suggested that such Pre-S/S vaccines against HBV might be efficacious not only for prevention but also for intervention in persistent HBV infection. Data obtained in a recent clinical trial conducted in Vietnam in patients with chronic hepatitis B suggest that repeated monthly i.m. injections of the Sci-B-Vac™ co-administered with daily oral lamivudine treatment can suppress HBV replication and lead to anti-HBs seroconversion in ~50 % of treated patients. Optimization of protocols and efficacy of such an intervention, intended to bypass T cell exhaustion and immune tolerance to HBV remains to be explored.