Systematic analysis of the combinatorial nature of epitopes recognized by TCR leads to identification of mimicry epitopes for glutamic acid decarboxylase 65-specific TCRs

Human iPSC-derived CD4+ Treg-like cells engineered with chimeric antigen receptors control GvHD in a xenograft model

CD4+ T cells induced from human iPSCs (iCD4+ T cells) offer a therapeutic opportunity for overcoming immune pathologies arising from hematopoietic stem cell transplantation. However, most iCD4+ T cells are conventional helper T cells, which secrete inflammatory cytokines. We induced high-level expression of FOXP3, a master transcription factor of regulatory T cells, in iCD4+ T cells. Human iPSC-derived, FOXP3-induced CD4+ T (iCD4+ Treg-like) cells did not secrete inflammatory cytokines upon activation. Moreover, they showed demethylation of the Treg-specific demethylation region, suggesting successful conversion to immunosuppressive iCD4+ Treg-like cells. We further assessed these iCD4+ Treg-like cells for CAR-mediated immunosuppressive ability. HLA-A2 CAR-transduced iCD4+ Treg-like cells inhibited CD8+ cytotoxic T cell (CTL) division in a mixed lymphocyte reaction assay with A2+ allogeneic CTLs and suppressed xenogeneic graft-versus-host disease (GVHD) in NSG mice treated with A2+ human PBMCs. In most cases, these cells suppressed the xenogeneic GvHD progression as much as natural CD25+CD127- Tregs did.

Clostridia and Enteroviruses as Synergistic Triggers of Type 1 Diabetes Mellitus

What triggers type 1 diabetes mellitus (T1DM)? One common assumption is that triggers are individual microbes that mimic autoantibody targets such as insulin (INS). However, most microbes highly associated with T1DM pathogenesis, such as coxsackieviruses (COX), lack INS mimicry and have failed to induce T1DM in animal models. Using proteomic similarity search techniques, we found that COX actually mimicked the INS receptor (INSR). Clostridia were the best mimics of INS. Clostridia antibodies cross-reacted with INS in ELISA experiments, confirming mimicry. COX antibodies cross-reacted with INSR. Clostridia antibodies further bound to COX antibodies as idiotype-anti-idiotype pairs conserving INS-INSR complementarity. Ultraviolet spectrometry studies demonstrated that INS-like Clostridia peptides bound to INSR-like COX peptides. These complementary peptides were also recognized as antigens by T cell receptor sequences derived from T1DM patients. Finally, most sera from T1DM patients bound strongly to inactivated Clostridium sporogenes, while most sera from healthy individuals did not; T1DM sera also exhibited evidence of anti-idiotype antibodies against idiotypic INS, glutamic acid decarboxylase, and protein tyrosine phosphatase non-receptor (islet antigen-2) antibodies. These results suggest that T1DM is triggered by combined enterovirus-Clostridium (and possibly combined Epstein-Barr-virus-Streptococcal) infections, and the probable rate of such co-infections approximates the rate of new T1DM diagnoses.

T-Cell Epitopes and Neo-epitopes in Type 1 Diabetes: A Comprehensive Update and Reappraisal

The autoimmune disease type 1 diabetes is characterized by effector T-cell responses to pancreatic β-cell-derived peptides presented by HLA class I and class II molecules, leading ultimately to β-cell demise and insulin insufficiency. Although a given HLA molecule presents a vast array of peptides, only those recognized by T cells are designated as epitopes. Given their intimate link to etiology, the discovery and characterization of T-cell epitopes is a critical aspect of type 1 diabetes research. Understanding epitope recognition is also crucial for the pursuit of antigen-specific immunotherapies and implementation of strategies for T-cell monitoring. For these reasons, a cataloging and appraisal of the T-cell epitopes targeted in type 1 diabetes was completed over a decade ago, providing an important resource for both the research and the clinical communities. Here we present a much needed update and reappraisal of this earlier work and include online supplementary material where we cross-index each epitope with its primary references and Immune Epitope Database (IEDB) identifier. Our analysis includes a grading scale to score the degree of evidence available for each epitope, which conveys our perspective on several useful criteria for epitope evaluation. While providing an efficient summary of the arguably impressive current state of knowledge, this work also brings to light several deficiencies. These include the need for improved epitope validation, as few epitopes score highly by the criteria employed, and the dearth of investigations of the epitopes recognized in the context of several understudied type 1 diabetes-associated HLA molecules.

BCR-ABL-specific CD4+ T-helper cells promote the priming of antigen-specific cytotoxic T cells via dendritic cells

The advent of tyrosine kinase inhibitor (TKI) therapy markedly improved the outcome of patients with chronic-phase chronic myeloid leukemia (CML). However, the poor prognosis of patients with advanced-phase CML and the lifelong dependency on TKIs are remaining challenges; therefore, an effective therapeutic has been sought. The BCR-ABL p210 fusion protein's junction region represents a leukemia-specific neoantigen and is thus an attractive target for antigen-specific T-cell immunotherapy. BCR-ABL p210 fusion-region-specific CD4+ T-helper (Th) cells possess antileukemic potential, but their function remains unclear. In this study, we established a BCR-ABL p210 b3a2 fusion-region-specific CD4+ Th-cell clone (b3a2-specific Th clone) and examined its dendritic cell (DC)-mediated antileukemic potential. The b3a2-specific Th clone recognized the b3a2 peptide in the context of HLA-DRB1*09:01 and exhibited a Th1 profile. Activation of this clone through T-cell antigen receptor stimulation triggered DC maturation, as indicated by upregulated production of CD86 and IL-12p70 by DCs, which depended on CD40 ligation by CD40L expressed on b3a2-specific Th cells. Moreover, in the presence of HLA-A*24:02-restricted Wilms tumor 1 (WT1)235-243 peptide, DCs conditioned by b3a2-specific Th cells efficiently stimulated the primary expansion of WTI-specific cytotoxic T lymphocytes (CTLs). The expanded CTLs were cytotoxic toward WT1235-243-peptide-loaded HLA-A*24:02-positive cell lines and exerted a potent antileukemic effect in vivo. However, the b3a2-specific Th-clone-mediated antileukemic CTL responses were strongly inhibited by both TKIs and interferon-α. Our findings indicate a crucial role of b3a2-specific Th cells in leukemia antigen-specific CTL-mediated immunity and provide an experimental basis for establishing novel CML immunotherapies.

Generation of Large Numbers of Antigen-Expressing Human Dendritic Cells Using CD14-ML Technology

We previously reported a method to expand human monocytes through lentivirus-mediated introduction of cMYC and BMI1, and we named the monocyte-derived proliferating cells, CD14-ML. CD14-ML differentiated into functional DC (CD14-ML-DC) upon addition of IL-4, resulting in the generation of a large number of DC. One drawback of this method was the extensive donor-dependent variation in proliferation efficiency. In the current study, we found that introduction of BCL2 or LYL1 along with cMYC and BMI1 was beneficial. Using the improved method, we obtained CD14-ML from all samples, regardless of whether the donors were healthy individuals or cancer patients. In vitro stimulation of peripheral blood T cells with CD14-ML-DC that were loaded with cancer antigen-derived peptides led to the establishment of CD4+ and CD8+ T cell lines that recognized the peptides. Since CD14-ML was propagated for more than 1 month, we could readily conduct genetic modification experiments. To generate CD14-ML-DC that expressed antigenic proteins, we introduced lentiviral antigen-expression vectors and subjected the cells to 2 weeks of culture for drug-selection and expansion. The resulting antigen-expressing CD14-ML-DC successfully induced CD8+ T cell lines that were reactive to CMVpp65 or MART1/MelanA, suggesting an application in vaccination therapy. Thus, this improved method enables the generation of a sufficient number of DC for vaccination therapy from a small amount of peripheral blood from cancer patients. Information on T cell epitopes is not necessary in vaccination with cancer antigen-expressing CD14-ML-DC; therefore, all patients, irrespective of HLA type, will benefit from anti-cancer therapy based on this technology.

Immune response to HHV-6 and implications for immunotherapy

Most adults remain chronically infected with HHV-6 after resolution of a primary infection in childhood, with the latent virus held in check by the immune system. Iatrogenic immunosuppression following solid organ transplantation (SOT) or hematopoetic stem cell transplantation (HSCT) can allow latent viruses to reactivate. HHV-6 reactivation has been associated with increased morbidity, graft rejection, and neurological complications post-transplantation. Recent work has identified HHV-6 antigens that are targeted by the CD4+ and CD8+ T cell response in chronically infected adults. T cell populations recognizing these targets can be expanded in vitro and are being developed for use in autologous immunotherapy to control post-transplantation HHV-6 reaction.

Generation of a large number of functional dendritic cells from human monocytes expanded by forced expression of cMYC plus BMI1

Anticancer vaccination therapies with monocyte-derived dendritic cells (DC) are widely conducted. A large number of primary monocytes (approximately 10(8) cells) are needed to generate the number of DC required to achieve an effect upon vaccination, and monocytes are usually purified from peripheral blood mononuclear cells obtained by apheresis procedure, which is somehow invasive for cancer patients. As a means to facilitate the generation of DC for therapeutic use, we herein report a method to amplify human monocytes. We found that lentivirus-mediated transduction of cMYC along with BMI1 induced proliferation of CD14(+) monocytes derived from 9 out of 12 blood donors, and we named the monocyte-derived proliferating cells CD14-ML. Their proliferation continued for 3-5 weeks in the presence of M-CSF and GM-CSF, resulting in 20-1000-fold amplification. Importantly, the expanded CD14-ML differentiated into fully functional DC (CD14-ML-DC) upon the addition of IL-4 to the culture. We successfully stimulated autologous CD8(+) T cells with CD14-ML-DC pulsed with cytomegalovirus peptide or MART-1 peptide to generate antigen-specific CTL lines. This is the first report describing the method for in vitro expansion of human peripheral blood monocytes.

Human CD4+ T cell response to human herpesvirus 6

Following primary infection, human herpesvirus 6 (HHV-6) establishes a persistent infection for life. HHV-6 reactivation has been associated with transplant rejection, delayed engraftment, encephalitis, muscular dystrophy, and drug-induced hypersensitivity syndrome. The poor understanding of the targets and outcome of the cellular immune response to HHV-6 makes it difficult to outline the role of HHV-6 in human disease. To fill in this gap, we characterized CD4 T cell responses to HHV-6 using peripheral blood mononuclear cell (PBMC) and T cell lines generated from healthy donors. CD4(+) T cells responding to HHV-6 in peripheral blood were observed at frequencies below 0.1% of total T cells but could be expanded easily in vitro. Analysis of cytokines in supernatants of PBMC and T cell cultures challenged with HHV-6 preparations indicated that gamma interferon (IFN-γ) and interleukin-10 (IL-10) were appropriate markers of the HHV-6 cellular response. Eleven CD4(+) T cell epitopes, all but one derived from abundant virion components, were identified. The response was highly cross-reactive between HHV-6A and HHV-6B variants. Seven of the CD4(+) T cell epitopes do not share significant homologies with other known human pathogens, including the closely related human viruses human herpesvirus 7 (HHV-7) and human cytomegalovirus (HCMV). Major histocompatibility complex (MHC) tetramers generated with these epitopes were able to detect HHV-6-specific T cell populations. These findings provide a window into the immune response to HHV-6 and provide a basis for tracking HHV-6 cellular immune responses.

Generation of dendritic cells and macrophages from human induced pluripotent stem cells aiming at cell therapy

This report describes generation of dendritic cells (DCs) and macrophages from human induced pluripotent stem (iPS) cells. iPS cell-derived DC (iPS-DC) exhibited the morphology of typical DC and function of T-cell stimulation and antigen presentation. iPS-DC loaded with cytomegalovirus (CMV) peptide induced vigorous expansion of CMV-specific autologous CD8+ T cells. Macrophages (iPS-MP) with activity of zymosan phagocytosis and C5a-induced chemotaxis were also generated from iPS cells. Genetically modified iPS-MPs were generated by the introduction of expression vectors into undifferentiated iPS cells, isolation of transfectant iPS cell clone and subsequent differentiation. By this procedure, we generated iPS-MP expressing a membrane-bound form of single chain antibody (scFv) specific to amyloid β (Aβ), the causal protein of Alzheimer's disease. The scFv-transfectant iPS-MP exhibited efficient Aβ-specific phagocytosis activity. iPS-MP expressing CD20-specific scFv engulfed and killed BALL-1 B-cell leukemia cells. Anti-BALL-1 effect of iPS-MP in vivo was demonstrated in a xeno-transplantation model using severe combined immunodeficient mice. In addition, we established a xeno-free culture protocol to generate iPS-DC and iPS-MP. Collectively, we demonstrated the possibility of application of iPS-DC and macrophages to cell therapy.

Cytokine-dependent modification of IL-12p70 and IL-23 balance in dendritic cells by ligand activation of Valpha24 invariant NKT cells

CD1d-restricted invariant NKT (iNKT) cells play crucial roles in various types of immune responses, including autoimmune diseases, infectious diseases and tumor surveillance. The mechanisms underlying their adjuvant functions are well understood. Nevertheless, although IL-4 and IL-10 production characterize iNKT cells able to prevent or ameliorate some autoimmune diseases and inflammatory conditions, the precise mechanisms by which iNKT cells exert immune regulatory function remain elusive. This study demonstrates that the activation of human iNKT cells by their specific ligand alpha-galactosylceramide enhances IL-12p70 while inhibiting the IL-23 production by monocyte-derived dendritic cells, and in turn down-regulating the IL-17 production by memory CD4(+) Th cells. The ability of the iNKT cells to regulate the differential production of IL-12p70/IL-23 is mainly mediated by a remarkable hallmark of their function to produce both Th1 and Th2 cytokines. In particular, the down-regulation of IL-23 is markedly associated with a production of IL-4 and IL-10 from iNKT cells. Moreover, Th2 cytokines, such as IL-4 and IL-13 play a crucial role in defining the biased production of IL-12p70/IL-23 by enhancement of IL-12p70 in synergy with IFN-gamma, whereas inhibition of the IFN-gamma-promoted IL-23 production. Collectively, the results suggest that iNKT cells modify the IL-12p70/IL-23 balance to enhance the IL-12p70-induced cell-mediated immunity and suppress the IL-23-dependent inflammatory pathologies. These results may account for the long-appreciated contrasting beneficial and adverse consequence of ligand activation of iNKT cells.

Immunogenicity in peptide-immunotherapy: from self/nonself to similar/dissimilar sequences

The nature of the relationship between an antigenic amino acid sequence and its capability to evoke an immune response is still an unsolved problem. Although experiments indicate that specific (dis)continuous amino acid sequences may determine specific immune responses, how immunogenic properties and recognition informations are mapped onto a non-linear sequence is not understood. Immunology has invoked the concept of self/nonself discrimination in order to explain the capability of the organism to selectively immunoreact. However, no clear, logical and rational pathway has emerged to relate a structure and its immuno-nonreactivity. It cannot yet be dismissed what Koshland wrote in 1990: "Of all the mysteries of modern science, the mechanism of self versus nonself recognition in the immune system ranks at or near the top". This chapter reviews the concept of self/nonself discrimination in the immune system starting from the historical perspective and the conceptual framework that underlie immune reaction pattern. It also introduces future research directions based on a proteomic dissection of the immune unit, qualitatively defined as a low-similarity sequence and quantitatively delimitated by the minimum amino acid requisite able to evoke an immune response, independently ofany, microbial or viral, "foreignness".

Insulin-like growth factor-binding protein-2 is a target for the immunomodulation of breast cancer

Breast cancer is immunogenic and well suited to treatment via immunomodulation. The disease is often treated to remission and time to relapse is generally measured in years in many cases. Immune-based therapeutics, such as cancer vaccines, may be able to affect the clinical progression of micrometastatic disease. Immune targets must be identified that have the potential to inhibit tumor growth. Insulin-like growth factor-binding protein-2 (IGFBP-2) has direct effects on breast cancer proliferation via stimulation of critical signaling pathways. We questioned whether IGFBP-2 was an immune target in breast cancer. IGFBP-2-specific IgG antibody immunity was preferentially detected in breast cancer patients compared with controls (P = 0.0008). To evaluate for the presence of T-cell immunity, we identified potential pan-HLA-DR binding epitopes derived from IGFBP-2 and tested the peptides for immunogenicity. The majority of epitopes elicited peptide-specific T cells in both patients and controls and had high sequence homology to bacterial pathogens. IGFBP-2 peptide-specific T cells could respond to naturally processed and presented IGFBP-2 protein, indicating that these peptides were native epitopes of IGFBP-2. Finally, both immunization with IGFBP-2 peptides as well as adoptive transfer of IGFBP-2-competent T cells mediated an antitumor effect in a transgenic mouse model of breast cancer. This is the first report of IGFBP-2 as a human tumor antigen that may be a functional therapeutic target in breast cancer.

Distinct subsets of human invariant NKT cells differentially regulate T helper responses via dendritic cells

Invariant natural killer T (iNKT) cells regulate the T helper (Th) 1/2 balance and elicit either enhancement or suppression of the immune responses. However, the exact mechanism by which iNKT cells exert these contrasting functions has remained elusive. We demonstrate herein that two major distinct subsets of human iNKT cells, CD4+CD8beta(-) (CD4+) and CD4(-)CD8beta(-) (double negative; DN) cells, express functional CD40 ligand (CD40L), but they differentially regulate the dendritic cell (DC) function by reciprocal NKT-DC interactions, thereby influencing the subsequent Th response. The CD4 subset stimulated by alpha-galactosylceramide (alpha-GalCer)-loaded DC immediately produced massive amounts of IL-4 and IL-13, which together with IFN-gamma enhanced CD40L-induced IL-12 production by DC. In contrast, the DN subset eliminated the DC by cytolysis and changed the living DC into a default subtype, in turn markedly down-regulating the levels of IL-12. Therefore, the DC stimulated by the CD4 subset preferentially induced Th1 responses, whereas the DC reacted with the DN subset induced a shift toward Th2 responses. These findings may provide an important insight into better understanding the contribution of iNKT-DC cross-talk governing the Th1/2 balance and the diverse influences of iNKT cells in various diseases.

Genetically Manipulated Human Embryonic Stem Cell-Derived Dendritic Cells with Immune Regulatory Function

Genetically manipulated dendritic cells (DC) are considered to be a promising means for antigen-specific immune therapy. This study reports the generation, characterization, and genetic modification of DC derived from human embryonic stem (ES) cells. The human ES cell-derived DC (ES-DC) expressed surface molecules typically expressed by DC and had the capacities to stimulate allogeneic T lymphocytes and to process and present protein antigen in the context of histocompatibility leukocyte antigen (HLA) class II molecule. Genetic modification of human ES-DC can be accomplished without the use of viral vectors, by the introduction of expression vector plasmids into undifferentiated ES cells by electroporation and subsequent induction of differentiation of the transfectant ES cell clones to ES-DC. ES-DC introduced with invariant chain-based antigen-presenting vectors by this procedure stimulated HLA-DR-restricted antigen-specific T cells in the absence of exogenous antigen. Forced expression of programmed death-1-ligand-1 in ES-DC resulted in the reduction of the proliferative response of allogeneic T cells cocultured with the ES-DC. Generation and genetic modification of ES-DC from nonhuman primate (cynomolgus monkey) ES cells was also achieved by the currently established method. ES-DC technology is therefore considered to be a novel means for immune therapy.

Vaccination and infection as causative factors in Japanese patients with Rasmussen syndrome: molecular mimicry and HLA class I

Rasmussen syndrome is an intractable epilepsy with a putative causal relation with cellular and humoral autoimmunity. Almost half of the patients have some preceding causative factors, with infections found in 38.2%, vaccinations in 5.9% and head trauma in 8.9% of Japanese patients. In a patient with seizure onset after influenza A infections, cross-reaction of the patient's lymphocytes with GluRε2 and influenza vaccine components was demonstrated by lymphocyte stimulation test. Database analyses revealed that influenza A virus hemagglutinin and GluRε2 molecules contain peptides with the patient's HLA class I binding motif (HLA − A*0201). The relative risks of HLA class I genotypes for Rasmussen syndrome are 6.1 (A*2402), 6.4 (A*0201), 6.3 (A*2601) and 11.4 (B*4601). The relative risks of HLA class I-A and B haplotypes are infinity (A*2601+B*5401), 21.1 (A*2402+B*1501), 13.3 (A*2402+B*4801) and 5.1 (A*2402+B*5201). Some alleles and haplotypes of HLA class I may be the risk factors in Japanese patients. Cross-reactivity of cytotoxic T lymphocytes may contribute to the processes leading from infection to the involvement of CNS.

Involvement of Regulatory T Cells in the Experimental Autoimmune Encephalomyelitis-Preventive Effect of Dendritic Cells Expressing Myelin Oligodendrocyte Glycoprotein plus TRAIL

We previously reported the protection from myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) by the adoptive transfer of genetically modified embryonic stem cell-derived dendritic cells (ES-DC) presenting MOG peptide in the context of MHC class II molecules and simultaneously expressing TRAIL (ES-DC-TRAIL/MOG). In the present study, we found the severity of EAE induced by another myelin autoantigen, myelin basic protein, was also decreased after treatment with ES-DC-TRAIL/MOG. This preventive effect diminished, if the function of CD4(+)CD25(+) regulatory T cells (Treg) was abrogated by the injection of anti-CD25 mAb into mice before treatment with ES-DC-TRAIL/MOG. The adoptive transfer of CD4(+)CD25(+) T cells from ES-DC-TRAIL/MOG-treated mice protected the recipient mice from MOG- or myelin basic protein-induced EAE. The number of Foxp3(+) cells increased in the spinal cords of mice treated with ES-DC-TRAIL/MOG. In vitro experiments showed that TRAIL expressed in genetically modified ES-DC and also in LPS-stimulated splenic macrophages had a capacity to augment the proliferation of CD4(+)CD25(+) T cells. These results suggest that the prevention of EAE by treatment with ES-DC-TRAIL/MOG is mediated, at least in part, by MOG-reactive CD4(+)CD25(+) Treg propagated by ES-DC-TRAIL/MOG. For the treatment of organ-specific autoimmune diseases, induction of Treg reactive to the organ-specific autoantigens by the transfer of DC-presenting Ags and simultaneously overexpressing TRAIL therefore appears to be a promising strategy.

Infections as causative factors of epilepsy

Epilepsies bearing some relationship to infections or vaccinations are often encountered clinically. While the onset of epilepsy or aggravation of seizures may follow common infections or vaccinations, complete seizure control has also been observed after infections. However, the true mechanisms underlying the relationship between infections and epilepsies have not been fully elucidated. Recently, advances in immunology have contributed to the study of autoimmune mechanisms in Rasmussen’s syndrome, a prototype of autoimmune epilepsy related to infections. The roles of autoimmunity, including cytotoxic T cells and autoantibodies against neural molecules, have been demonstrated in Rasmussen’s syndrome. This review postulates the probable molecular mimicry of microbial and neural components in Rasmussen’s syndrome and proposes possible autoimmune mechanisms related to the development of symptomatic epilepsies.

T-cell molecular mimicry in Chagas disease: identification and partial structural analysis of multiple cross-reactive epitopes between Trypanosoma cruzi B13 and cardiac myosin heavy chain

Chagas disease cardiomyopathy (CCC) is one of the few examples of post-infectious autoimmunity, where infectious episodes with an established pathogen, the protozoan parasite Trypanosoma cruzi, clearly triggers molecular mimicry-related target organ immune damage. CD4+ T-cell clones infiltrating hearts from CCC patients cross-reactively recognize human cardiac myosin, the major heart protein, and the immunodominant B13 protein from T. cruzi. Moreover, in vitro priming with B13 leads to the recovery of cardiac myosin cross-reactive T-cell clones. In order to identify cross-reactive epitopes between B13 protein and human cardiac myosin, we used B13 peptide S15.4, preferentially recognized by CCC patients, to establish a T-cell clone from an HLA-DQ7 individual. The B13 S15.4 peptide-specific CD4+ T-cell clone 3E5 was tested in proliferation assays against 15 Lys/His-substituted S15.4-derived peptides for TCR/HLA contact analysis. Together with previous HLA-binding data and molecular modeling of the HLA-DQ7-peptide S15.4 complex, Lys/His scanning analysis showed eight TCR/HLA contact positions. Clone 3E5 was also tested against 45 15-mer peptides from human beta-cardiac myosin heavy chain bearing the central HLA-DQ7 binding motif. Clone 3E5 recognized 13 peptides from cardiac myosin. The alignment of cross-reactive peptides in cardiac myosin showed very limited sharing of residues or side chains with similar chemical/structural features at aligned positions, indicative of a very degenerate TCR recognition pattern. The existence of degenerate intramolecular recognition, with multiple low-homology, cross-reactive epitopes in a single autoantigenic protein may have implications in increasing the magnitude of the autoimmune response in CCC and other autoimmune diseases.

Coculture of Th cells with interleukin (IL)-7 in the absence of antigenic stimuli induced T-cell anergy reversed by IL-15

Interleukin-7 (IL-7) is an important survival factor for T cells. We report here for the first time that it has another important role, facilitating T-cell clonal unresponsiveness, or anergy. The anergy was induced by a 20-day coculture of activated-human CD4(+) T-cell clones with IL-7 and irradiated peripheral blood mononuclear cells without antigenic stimuli. T-cell survival, but not T-cell anergy induction, was dependent on direct cell contacts between T cells and irradiated peripheral blood mononuclear cells. The anergic T cells exhibited no or very low expression of IL-7 receptor alpha chain (IL-7Ralpha), IL-2 receptor alpha chain (IL-2Ralpha), and common gamma chain (gammac), and did not express cytotoxic T-lymphocyte-associated protein 4, but expressed IL-15Ralpha. Coculture for 3 to 9 days of anergic T cells with a T-cell-activating cytokine IL-15, but not IL-2, restored the responsiveness of IL-7-induced anergic T cells together with reexpressions of IL-7Ralpha, IL-2Ralpha, and gammac. The anergy induction by IL-7 and restoration of responsiveness by IL-15 suggest novel mechanisms for regulation of helper T-cell responses, induction of peripheral tolerance, and breakdown of T-cell self-tolerance.

Prevention of Experimental Autoimmune Encephalomyelitis by Transfer of Embryonic Stem Cell-Derived Dendritic Cells Expressing Myelin Oligodendrocyte Glycoprotein Peptide along with TRAIL or Programmed Death-1 Ligand

Experimental autoimmune encephalomyelitis (EAE) is caused by activation of myelin Ag-reactive CD4+ T cells. In the current study, we tested a strategy to prevent EAE by pretreatment of mice with genetically modified dendritic cells (DC) presenting myelin oligodendrocyte glycoprotein (MOG) peptide in the context of MHC class II molecules and simultaneously expressing TRAIL or Programmed Death-1 ligand (PD-L1). For genetic modification of DC, we used a recently established method to generate DC from mouse embryonic stem cells (ES cells) in vitro (ES-DC). ES cells were sequentially transfected with an expression vector for TRAIL or PD-L1 and an MHC class II-associated invariant chain-based MOG epitope-presenting vector. Subsequently, double-transfectant ES cell clones were induced to differentiate to ES-DC, which expressed the products of introduced genes. Treatment of mice with either of the double-transfectant ES-DC significantly reduced T cell response to MOG, cell infiltration into spinal cord, and the severity of MOG peptide-induced EAE. In contrast, treatment with ES-DC expressing MOG alone, irrelevant Ag (OVA) plus TRAIL, or OVA plus PD-L1, or coinjection with ES-DC expressing MOG plus ES-DC-expressing TRAIL or PD-L1 had no effect in reducing the disease severity. In contrast, immune response to irrelevant exogenous Ag (keyhole limpet hemocyanin) was not impaired by treatment with any of the genetically modified ES-DC. The double-transfectant ES-DC presenting Ag and simultaneously expressing immune-suppressive molecules may well prove to be an effective therapy for autoimmune diseases without inhibition of the immune response to irrelevant Ag.

Peptides from common viral and bacterial pathogens can efficiently activate diabetogenic T-cells

Cross-reactivity between an autoantigen and unknown microbial epitopes has been proposed as a molecular mechanism involved in the development of insulin-dependent diabetes (type 1 diabetes). Type 1 diabetes is an autoimmune disease that occurs in humans and the nonobese diabetic (NOD) mouse. BDC2.5 is an islet-specific CD4+ T-cell clone derived from the NOD mouse whose natural target antigen is unknown. A biometrical analysis of screening data from BDC2.5 T-cells and a positional scanning synthetic combinatorial library (PS-SCL) was used to analyze and rank all peptides in public viral and bacterial protein databases and identify potential molecular mimic sequences with predicted reactivity. Selected sequences were synthesized and tested for stimulatory activity with BDC2.5 T-cells. Active peptides were identified, and some of them were also able to stimulate spontaneously activated T-cells derived from young, pre-diabetic NOD mice, indicating that the reactivity of the BDC2.5 T-cell is directed at numerous mouse peptides. Our results provide evidence for their possible role as T-cell ligands involved in the activation of diabetogenic T-cells.

B-Raf contributes to sustained extracellular signal-regulated kinase activation associated with interleukin-2 production stimulated through the T cell receptor

A T cell receptor (TCR) recognizes and responds to an antigenic peptide in the context of major histocompatibility complex-encoded molecules. This provokes T cells to produce interleukin-2 (IL-2) through extracellular signal-regulated kinase (ERK) activation. We investigated the roles of B-Raf in TCR-mediated IL-2 production coupled with ERK activation in the Jurkat human T cell line. We found that TCR cross-linking could induce up-regulation of both B-Raf and Raf-1 activities, but Raf-1 activity was decreased rapidly. On the other hand, TCR-stimulated kinase activity of B-Raf was sustained. Expression of a dominant-negative mutant of B-Raf abrogated sustained but not transient TCR-mediated MEK/ERK activation. The inhibition of sustained ERK activation by either expression of a dominant-negative B-Raf or treatment with a MEK inhibitor resulted in a decrease of the TCR-stimulated nuclear factor of activated T cells (NFAT) activity and IL-2 production. Collectively, our data provide the first direct evidence that B-Raf is a positive regulator of TCR-mediated sustained ERK activation, which is required for NFAT activation and the full production of IL-2.

Degenerate recognition and response of human CD4+ Th cell clones: implications for basic and applied immunology

It was once considered that the T cell response is an all or nothing type event, but recent studies have clearly indicated that T cells show many different types of activation in recognition of altered ligands for T cell receptors (TCR). In this review, we summarize our recent findings on the response of human CD4+ helper T (Th) cell clones to altered peptide ligands (APL); peptides carrying single or multiple residue substitutions in antigenic peptides. The extensive analyses revealed that TCR-antagonism and partial agonism are frequently observed by the stimulation with APLs substituted at particular amino acid residues of antigenic peptides. We observed unique partially agonistic APLs inducing prolongation of T cell survival without cell proliferation. Superagonistic APLs stimulated enhanced proliferation and production of cytokines in Th cell clones reactive to tumor-associated antigens. The other APL induced enhanced production of interleukin-12 by antigen presenting cells and subsequent enhancement of IFN-gamma production by T cells reactive to allergens. By utilizing an HLA-DR-restricted T cell epitope library generated by mutated invariant chain genes, it was revealed that human Th cell clones recognize a more diverse array of peptides with multiple and simultaneous amino acid substitutions in an antigenic peptide. APLs also induced altered intracellular signaling events including intracellular calcium increase and phosphorylation of signaling molecules. This information provides basic knowledge regarding the characteristics of antigen recognition by human Th cells and the subsequent activation, and a novel method for manipulation of human Th cell responses by APLs, as a possible candidate for antigen-specific immuno-potentiating or immunosuppressive therapy.

Enhanced Priming of Antigen-Specific CTLs In Vivo by Embryonic Stem Cell-Derived Dendritic Cells Expressing Chemokine Along with Antigenic Protein: Application to Antitumor Vaccination

Dendritic cell (DC)-based immunotherapy is regarded as a promising means for anti-cancer therapy. The efficiency of T cell-priming in vivo by transferred DCs should depend on their encounter with T cells. In the present study, we attempted to improve the capacity of DCs to prime T cells in vivo by genetic modification to express chemokine with a T cell-attracting property. For genetic modification of DCs, we used a recently established method to generate DCs from mouse embryonic stem cells. We generated double-transfectant DCs expressing a chemokine along with a model Ag (OVA) by sequential transfection of embryonic stem cells, and then induced differentiation to DCs. We comparatively evaluated the effect of three kinds of chemokines; secondary lymphoid tissue chemokine (SLC), monokine induced by IFN-gamma (Mig), and lymphotactin (Lptn). All three types of double transfectant DCs primed OVA-specific CTLs in vivo more efficiently than did DCs expressing only OVA, and the coexpression of SLC or Lptn was more effective than that of Mig. Immunization with DCs expressing OVA plus SLC or Mig provided protection from OVA-expressing tumor cells more potently than did immunization with OVA alone, and SLC was more effective than Mig. In contrast, coexpression of Lptn gave no additive effect on protection from the tumor. Collectively, among the three chemokines, expression of SLC was the most effective in enhancing antitumor immunity by transferred DCs in vivo. The findings provide useful information for the development of a potent DC-based cellular immunotherapy.

Specificity, degeneracy, and molecular mimicry in antigen recognition by HLA-Class II restricted T cell receptors: implications for clinical medicine

Abstract In humans, increased susceptibility to specific autoimmune diseases is closely associated with specific HLA-class II alleles. CD4(+) T cells that recognize short self-peptides in the context of HLA-class II molecules via their T cell receptor (TCR) are considered to mediate the central role of pathogenesis in autoimmunity. Although both self- and nonself-peptides are presented on HLA-class II molecules under physiological conditions, several mechanisms exist to avoid the T cell response to the self-peptide/HLA-class II complex. One of the mechanisms that account for the breakdown in immune tolerance is cross-recognition by TCR between a pathogen-derived antigen and a host antigen (molecular mimicry theory). Epidemiological studies have indicated that a number of autoimmune diseases are developed or exacerbated after infections. Therefore, elucidating the recognition nature of HLA-class II restricted TCR in detail is necessary in order to understand disease processes. A large body of evidence indicates that T cell recognition is highly degenerate, and many different peptides can activate an individual T cell. Degeneracy of TCR recognition also can appear in various physiological outcomes, ranging from full activation to strong antagonism. Here, we review the clinical implications of our findings on T cell recognition, as well as a new direction of future applications for analyses in molecular mimicry. We also describe the latest developments in methods of mapping TCR epitopes for CD4(+) T cells using a peptide epitope expression library generated in the class II-associated invariant chain peptide substituted invariant chain gene format.