Cellular and molecular mechanisms of tumor-induced T-cell tolerance

The spontaneous interaction between tumor cells and the immune system has been shown to result in reciprocal changes leading to a less immunogenic tumor and immune cells less capable or unable to mount an effective response against a growing malignancy. Although several mechanisms have been proposed to account for the ability of tumor cells to render immune cells less efficient, one that has gained particular attention relates to the recognition of tumor antigens by T-cells, a process that unfortunately leads to the induction and establishment of antigen-specific T-cell tolerance rather than T-cell priming. Here, we present the experimental and clinical evidence that help identify this remarkable barrier that the immune system itself and more specifically its mechanisms of tolerance induction has imposed to our efforts to effectively harness the immune system against tumors. In particular, we will discuss the central role of bone marrow-derived antigen-presenting cells (APCs) in the induction of this state of T-cell unresponsiveness and the potential role of the tumor microenvironment in determining the tolerogenic properties of these APCs. Finally, we provide information on receptor-ligands and intracellular signaling pathways that given their role in influencing the inflammatory properties of APCs are being exploited as targets to revert mechanisms of T-cell unresponsiveness in cancer.     

免疫调节性纳米制剂的研究进展

自身免疫性疾病是一类以机体免疫系统紊乱为主要特征的局部或全身慢性炎症性疾病,严重影响患者生活质量。目前,临床上主要以降低疾病活动度为主要治疗目标,尚无法治愈。诱导免疫系统重新产生针对疾病相关抗原的免疫耐受,重塑免疫稳态,是治疗这类疾病的最佳策略与终级目标。近年来,基于纳米技术的免疫调节性纳米制剂在诱导抗原特异性免疫耐受方面显示出极大的潜力。通过对具有免疫调节功能的纳米制剂的设计策略,以及可诱导免疫耐受的纳米药物在自身免疫性疾病治疗中的最新研究进展进行综述,同时,分析当前免疫调节纳米制剂在临床转化中存在的障碍,旨在为治疗自身免疫性疾病的纳米药物的相关研究提供参考。     

Immune Modulation and Prevention of Autoimmune Disease by Repeated Sequences from Parasites Linked to Self Antigens

Parasite proteins containing repeats are essential invasion ligands, important for their ability to evade the host immune system and to induce immunosuppression. Here, the intrinsic suppressive potential of repetitive structures within parasite proteins was exploited to induce immunomodulation in order to establish self-tolerance in an animal model of autoimmune neurological disease. We tested the tolerogenic potential of fusion proteins containing repeat sequences of parasites linked to self-antigens. The fusion constructs consist of a recombinant protein containing repeat sequences derived from the S-antigen protein (SAg) of Plasmodium falciparum linked to a CD4 T cell epitope of myelin. They were tested for their efficacy to control the development of experimental autoimmune encephalomyelitis (EAE), In addition, we used the DO11.10 transgenic mouse model to study the immune mechanisms involved in tolerance induced by SAg fusion proteins. We found that repeated sequences of P. falciparum SAg protein linked to self-epitopes markedly protected mice from EAE. These fusion constructs were powerful tolerizing agents not only in a preventive setting but also in the treatment of ongoing disease. The tolerogenic effect was shown to be antigen-specific and strongly dependent on the physical linkage of the T cell epitope to the parasite structure and on the action of anti-inflammatory cytokines like IL-10 and TGF-β. Other mechanisms include down-regulation of TNF-α accompanied by increased numbers of FoxP3⁺ cells. This study describes the use of repetitive structures from parasites linked to defined T cell epitopes as an effective method to induce antigen-specific tolerance with potential applicability for the treatment and prevention of autoimmune diseases.     

B-cell based gene therapy for autoimmune diseases

The essence of the adaptive immune system is self tolerance, which is maintained by various central and peripheral check points. However, the tolerance mechanisms can be broken in autoimmune disease conditions due to genetic predisposition and environmental triggers. As a consequence, a patient's tissue is attacked by his/her own adaptive immune system. An ideal therapy for autoimmune diseases should include methods to re-establish tolerance to the underpinning autoantigen(s). During the last 15 years our lab has been dedicated to developing a novel B-cell gene therapy approach for antigen-specific tolerance induction. This approach has been successfully applied to at least five different animal models for human autoimmune diseases. In this article, we will discuss many of our successful preclinical studies using the B-cell gene therapy approach to induce tolerance, as well as similar studies from others. Particular focus will be given to the tolerance induction mechanisms that have been revealed from these studies.     

T cell tolerance in transplantation: possibilities for therapeutic intervention

It is now possible to induce donor-specific transplantation tolerance in adult rodents using a number of therapeutic strategies. These include the use of non-depleting monoclonal antibodies against T cell co-receptor and costimulation molecules, and immunisation with tolerogenic antigen-presenting cells. It is a common finding to all of these models of peripheral tolerance, as well as to various mouse models of autoimmune disease, that regulatory CD4(+) T cells are the principle mediators. There are currently no specific markers for regulatory T cells and their activity has been associated with different T cell subsets defined by the expression of activation markers, such as CD25 and cytotoxic T lymphocyte antigen-4 (CTLA-4), or anti-inflammatory cytokines, such as IL-10 and TGF-beta. Differential gene expression analyses have been used to identify potential new markers for regulatory T cells and to find novel targets for therapeutic manipulation of the immune system. The challenge now is to understand the biological principles that allow such immune reprogramming so that they can be safely applied to clinical situations.     

Versatile polyion complex micelles for peptide and siRNA vectorization to engineer tolerogenic dendritic cells

Dendritic cells (DCs) are professional antigen-presenting cells that play a critical role in maintaining the balance between immunity and tolerance and, as such are a promising immunotherapy tool to induce immunity or to restore tolerance. The main challenge to harness the tolerogenic properties of DCs is to preserve their immature phenotype. We recently developed polyion complex micelles, formulated with double hydrophilic block copolymers of poly(methacrylic acid) and poly(ethylene oxide) blocks and able to entrap therapeutic molecules, which did not induce DC maturation. In the current study, the intrinsic destabilizing membrane properties of the polymers were used to optimize endosomal escape property of the micelles in order to propose various strategies to restore tolerance. On the first hand, we showed that high molecular weight (Mw) copolymer-based micelles were efficient to favor the release of the micelle-entrapped peptide into the endosomes, and thus to improve peptide presentation by immature (i) DCs. On the second hand, we put in evidence that low Mw copolymer-based micelles were able to favor the cytosolic release of micelle-entrapped small interfering RNAs, dampening the DCs immunogenicity. Therefore, we demonstrate the versatile use of polyionic complex micelles to preserve tolerogenic properties of DCs. Altogether, our results underscored the potential of such micelle-loaded iDCs as a therapeutic tool to restore tolerance in autoimmune diseases.     

Natural and induced regulatory T cells: targets for immunotherapy of autoimmune disease and allergy

Recent advances in immunology have greatly increased our understanding of immunological tolerance. In particular, there has been a resurgence of interest in mechanisms of immune regulation. Immune regulation refers to the phenomenon, previously known as immune suppression, by which excessive responses to infectious agents and hypersensitivities to otherwise innocuous antigens such as self antigens and allergens are avoided. We now appreciate that various distinct cell types mediate immune suppression and that some of these may be induced by appropriate administration of antigens, synthetic peptides and drugs of various types. The induction of antigen specific immunotherapy for treatment of autoimmune and allergic diseases remains the 'holy grail' for treatment of these diseases. This goal comes ever closer as understanding of the mechanisms of immune suppression and in particular antigen specific immunotherapy increases. Here we review evidence that immune suppression is mediated by various different subsets of CD4 T cells.     

HLA-G expression in cancers: potential role in diagnosis, prognosis and therapy

Human leukocyte antigen G (HLA-G) is a non-classic major histocompatibility complex (MHC) class I molecule that functions as an immune suppressive molecule. HLA-G has direct inhibitory effects on natural killer cells(NK), dendritic cells (DC), T cells and has long-term tolerogenic indirect effects by inducing regulator T cells (Treg). HLA-G has been reported to be involved in various physio-pathological conditions such as reproduction, transplantation, autoimmunity, infectious and malignant diseases. In this context, aberrant expression of HLA-G in malignant diseases including hematological and solid tumors has been extensively investigated and its relevance to clinicoparameters and potential significance in diagnosis, prognosis and immune target therapy has been postulated. We here summarized the HLA-G expression in malignancies and emphasis its clinical relevance to malignant disease diagnosis, prognosis, and its potential in target-based immunotherapy was also discussed.     

Aspirin and immune system

The time-tested gradual exploration of aspirin's diverse pharmacological properties has made it the most reliable therapeutic agent worldwide. In addition to its well-argued anti-inflammatory effects, many new and exciting data have emerged regarding the role of aspirin in cells of the immune system and certain immunopathological states. For instance, aspirin induces tolerogenic activity in dendritic cells and determines the fate of naive T cells to regulatory phenotypes, which suggests its immunoregulatory potential in relevance to immune tolerance. It also displays some intriguing traits to modulate the innate and adaptive immune responses. In this article, the immunomodulatory relation of aspirin to different immune cells, such as neutrophils, macrophages, dendritic cells (DCs), natural killer (NK) cells, and the T and B lymphocytes has been highlighted. Moreover, the clinical prospects of aspirin in terms of autoimmunity, allograft rejection and immune tolerance have also been outlined.     

Application of innate immune molecules for a new class of drugs: infection, inflammation and beyond

The innate immune system plays an important role systemically and locally in infectious and inflammatory diseases. Vaccines, vaccine adjuvants and anti-inflammatory drugs were developed by understanding mechanisms of the innate immune system and causative factors of infection and inflammatory diseases. Pattern-recognition receptors, such as Toll-like receptors, retinoic acid-inducible gene I (RIG-I)-like helicases and nucleotide-binding oligomerization domain(NOD)-like receptors, and their downstream signals have great potential as targets of therapeutics because they are involved in numerous diseases. Furthermore, proteolytic systems such as autophagy and immunoproteasomes play important roles in the innate immune system, making them potential therapeutic targets also. By taking advantage of the immune system, humankind has made a great effort to develop new therapeutic and preventive medicines. Accordingly, we have reported several studies on the development of vaccines and adjuvants based on novel mechanistic strategies. Additionally, we have elucidated the mechanism underlying an interaction between innate immunity and the endocrine system. This review introduces the possible use of innate immune molecules for the development of immunomodulatory drugs and the involvement of the immune system in endocrine metabolic diseases to discuss future applications of innate immune molecules to therapeutics of various inflammatory diseases.     

Gene transfer for inherited metabolic disorders of the liver: immunological challenges

Hepatocytes are a key target for gene transfer directed at correction of inborn errors of metabolism. The theoretical potential of hepatocyte-directed gene transfer contrasts with the hurdles for clinical translation of this technology. Innate immune responses following gene transfer are initiated by recognition of pathogen-associated molecular patterns by pattern recognition receptors like Toll-like receptors. Adaptive immune responses may constitute the most significant hurdle for efficient gene transfer. Besides the challenge imposed by adaptive immune responses against the vector and the potential problem of pre-existing immunity, immune responses against the transgene product may also constitute an obstacle. The liver is a tolerogenic organ. Naive T cells encounter liver antigens initially in the liver, rather than in lymphoid tissue. Lymph nodes and the spleen are anatomical compartments that provide a particular microarchitecture and microenvironment for the induction of immunity. In contrast, antigen presentation in the liver takes place in a completely different microarchitecture and microenvironment. This is a key aspect of the hepatic adaptive immune tolerance induction. Consistent with the tolerogenic nature of the liver microenvironment, the risk of antibody formation against the transgene product may be limited in the setting of hepatocyte-directed gene transfer and specifically by restricting transgene expression to hepatocytes by use of hepatocyte-specific expression cassettes. However, it is unclear to which extent animal experimental data following gene transfer predict immune responses in humans. Extrapolations from animals to humans are required but should be performed with sufficient insight into the dramatic species differences of the immune system.     

Tuning Surface Charges of Peptide Nanofibers for Induction of Antigen-Specific Immune Tolerance: An Introductory Study

Induction of antigen-specific immune tolerance has emerged as the next frontier in treating autoimmune disorders, including atherosclerosis and graft-vs-host reactions during transplantation. Nanostructures are under investigation as a platform for the coordinated delivery of critical components, i.e., the antigen epitope combined with tolerogenic agents, to the target immune cells and subsequently induce tolerance. In the present study, the utility of supramolecular peptide nanofibers to induce antigen-specific immune tolerance was explored. To study the influence of surface charges of the nanofibers towards the extent of the induced immune response, the flanking charge residues at both ends of the amphipathic fibrillization peptide sequences were varied. Dexamethasone, an immunosuppressive glucocorticoid drug, and the ovalbumin-derived OVA323-339 peptide that binds to I-A(d) MHC Class II were covalently linked at either end of the peptide sequences. It was shown that the functional extensions did not alter the structural integrity of the supramolecular nanofibers. Furthermore, the surface charges of the nanofibers were modulated by the inclusion of charged residues. Dendritic cell culture assays suggested that nanofiber of less negative ζ-potential can augment the antigen-specific tolerogenic response. Our findings illustrate a molecular approach to calibrate the tolerogenic response induced by peptide nanofibers, which pave the way for better design of future tolerogenic immunotherapies.     

The cutting-edge technologies of siRNA delivery and their application in clinical trials

siRNA therapeutics allows precise regulation of disease specific gene expression to treat various diseases. Although gene silencing approaches using siRNA therapeutics shows some promising results in the treatment of gene-related diseases, the practical applications has been limited by problems such as inefficient in vivo delivery to target cells and nonspecific immune responses after systemic or local administration. To overcome these issues, various in vivo delivery platforms have been introduced. Here we provide an overview for three different platform technologies for the in vivo delivery of therapeutic siRNAs (siRNA–GalNAc conjugate, SAMiRNA technology, and LNP-based delivery method) and their applications in the treatment of various diseases. In addition, a brief introduction to some rare diseases and mechanisms of siRNA therapeutics-mediated treatment is described.     

Gut microbiota in autoimmunity: potential for clinical applications

Microbial habitation in the human body begins immediately after birth, and adults are colonized by microbes outnumbering human cells by a factor of ten. Especially, intestinal track is a living space for diverse microbial species that have coevolved symbiotically. A principal function of the gut microbiota is to protect the host from harmful bacteria and to provide benefits for the host through several mechanisms, including direct competition for limited nutrients, training of host immune systems to recognize specifically foreign materials and conversion of otherwise indigestible food into energy and absorbable nutrients. Therefore, gut dysbiosis, a bacterial imbalance state, is related with the pathogenesis of various host diseases including autoimmune diseases. In the current review, we highlight the importance of gut microbiota in the normal health and autoimmune diseases. We also discuss regulation of gut dysbiosis and future direction for potential clinical applications, including treatment and diagnostics of autoimmune diseases.     

Cortistatin as a potential multistep therapeutic agent for inflammatory disorders

The induction of immune tolerance is critical for the prevention of autoimmunity and the maintenance of immune homeostasis. The identification of factors involved in the maintenance or restoration of such tolerance has become the focus of new therapies for inflammatory and autoimmune diseases. Cortistatin, a recently discovered cyclic neuropeptide related to somatostatin, has emerged as a potential endogenous antiinflammatory factor based on its production by, as well as its binding to, immune cells. Thus, cortistatin has been found to downregulate the inflammatory response mediated by activated macrophages. The present work reviews various recent studies involving different experimental models of sepsis, rheumatoid arthritis and inflammatory bowel disease, demonstrating that cortistatin treatment offers great benefits at both the clinical and pathological levels. These include the downregulation of both inflammatory and Th1-mediated autoimmune disease components and the emergence of regulatory T cells (Treg) that suppress autoreactive T cells, both of which contribute to the restoration of immune tolerance. While many questions need to be resolved, cortistatin appears to be an exciting and promising candidate for the treatment of several chronic inflammatory diseases and autoimmune disorders.     

Synthetic immunostimulatory oligonucleotides in experimental and clinical practice

BackgroundOligonucleotides belong to a class of macromolecules with great potential for research and various therapeutic applications. Their mechanisms of action are extremely diverse, although they are rather homogeneous in composition. Single-stranded oligodeoxynucleotides are not only inhibitors of gene expression, but their CpG sequence motifs may activate the innate immune response. Recent progress made in preclinical and clinical testing, as well as the case of the most recently discovered RNA interference technology, will help to overcome efficacy problems of the previous approaches of the ‘standard therapy’ of such diseases as tumors and various infections.MethodsThe aim of this article is to present various therapeutic aspects of oligonucleotides, and to review the most significant therapeutic applications of synthetic oligonucleotides. This paper presents a comprehensive review of current literature on various therapeutic properties of synthetic oligonucleotides.ConclusionsThe available results gathered from preclinical and clinical studies suggest that TLR9-targeted therapy of oligonucleotides can stimulate both innate and adaptive immunity. It also appears that CpG ODNs are generally safe, although moderate adverse effects, based on a backbone-related mechanism have been reported. The presented studies demonstrate that adjuvant CpG ODN can unify an immune response that leads to enhanced antigen-specific Ab formation. CpG ODN may therefore provide a unique approach to enhancing the efficacy of immunization, including the strengthening of antitumor immunity.