Cytokine profile and T cell adhesiveness to endothelial selectins: in vivo induction by a myasthenogenic T cell epitope and immunomodulation by a dual altered peptide ligand

Whole-exome sequencing reveals a rare interferon gamma receptor 1 mutation associated with myasthenia gravis

Our study is aimed to explore the underlying genetic basis of myasthenia gravis. We collected a Chinese pedigree with myasthenia gravis, and whole-exome sequencing was performed on the two affected siblings and their parents. The candidate pathogenic gene was identified by bioinformatics filtering, which was further verified by Sanger sequencing. The homozygous mutation c.G40A (p.V14M) in interferon gamma receptor 1was identified. Moreover, the mutation was also detected in 3 cases of 44 sporadic myasthenia gravis patients. The p.V14M substitution in interferon gamma receptor 1 may affect the signal peptide function and the translocation on cell membrane, which could disrupt the binding of the ligand of interferon gamma and antibody production, contributing to myasthenia gravis susceptibility. We discovered that a rare variant c.G40A in interferon gamma receptor 1 potentially contributes to the myasthenia gravis pathogenesis. Further functional studies are needed to confirm the effect of the interferon gamma receptor 1 on the myasthenia gravis phenotype.

Predicting the effects of potentially therapeutic modified peptides on polyclonal T cell populations in a mouse model of multiple sclerosis

Altered peptide ligands (APLs) have routinely been studied in clonal populations of Th cells that express a single T cell receptor (TCR), but results generated in this manner poorly predict the effects of APLs on polyclonal Th cells in vivo, contributing to the failure of phase II clinical trials of APLs in autoimmune diseases such as multiple sclerosis (MS). We have used a panel of APLs derived from an encephalitogenic epitope of myelin proteolipid protein to investigate the relationship between antigen cross-reactivity in a polyclonal environment, encephalitogenicity, and the capacity of an APL to provide protection against experimental autoimmune encephalomyelitis (EAE) in SJL mice. In general, polyclonal Th cell lines specific for encephalitogenic APLs cross-reacted with other encephalitogenic APLs, but not with non-encephalitogenic APLs, and vice versa. This, alongside analysis of TCR Vβ usage, suggested that encephalitogenic and non-encephalitogenic subgroups of APLs expand largely non-cross-reactive Th cell populations. As an exception to the rule, one non-encephalitogenic APL, L188, induced proliferation in polyclonal CD4⁺ T cells specific for the native encephalitogen, with minimal induction of cytokine production. Co-immunization of L188 alongside the native encephalitogen slightly enhanced disease development. In contrast, another APL, A188, which induced IL-10 production without proliferation in CD4⁺ T cells specific for the native encephalitogen, was able to protect against development of EAE in a dose-dependent fashion when co-immunized alongside the native encephalitogen. These results suggest that testing against polyclonal Th cell lines in vitro may be an effective strategy for distinguishing between potentially therapeutic and non-therapeutic APLs.

On Peptides and Altered Peptide Ligands: From Origin, Mode of Action and Design to Clinical Application (Immunotherapy)

T lymphocytes equipped with clonotypic T cell antigen receptors (TCR) recognize immunogenic peptides only when presented in the context of their own major histocompatibility complex (MHC) molecules. Peptide loading to MHC molecules occurs in intracellular compartments (ER for class I and MIIC for class II molecules) and relies on the interaction of the respective peptides and peptide binding pockets on MHC molecules. Those peptide residues not engaged in MHC binding point towards the TCR screening for possible peptide MHC complex binding partners. Natural or intentional modification of both MHC binding registers and TCR interacting residues of peptides – leading to the formation of altered peptide ligands (APLs) – might alter the way peptides interact with TCRs and hence influence subsequent T cell activation events, and consequently T cell effector functions. This review article summarizes how APLs were detected and first described, current concepts of how APLs modify T cellular signaling, which biological mechanisms might force the generation of APLs in vivo, and how peptides and APLs might be used for the benefit of patients suffering from allergic or autoimmune diseases.

A dual altered peptide ligand down-regulates myasthenogenic T cell responses and reverses experimental autoimmune myasthenia gravis via up-regulation of Fas-FasL-mediated apoptosis

Myasthenia gravis (MG) and experimental autoimmune MG (EAMG) are T cell-dependent, antibody-mediated autoimmune diseases. A dual altered peptide ligand (APL) that is composed of the tandemly arranged two single amino acid analogues of two myasthenogenic peptides, p195-212 and p259-271, was demonstrated to down-regulate in vitro and in vivo MG-associated autoreactive responses. The aims of this study were to investigate the possible role of Fas-FasL-mediated apoptosis in the down-regulatory mechanism of the dual APL. We demonstrate here the effect of the dual APL on expression of key molecules involved in the Fas-FasL pathway, in a p195-212-specific T cell line, in mice immunized with Torpedo acetylcholine receptor and in mice afflicted with EAMG (induced with the latter). In vitro and in vivo results show that the dual APL up-regulated expression of Fas and FasL on the CD4 cells. Expression of the pro-apoptotic molecules, caspase 8 and caspase 3, was significantly up-regulated, while anti-apoptotic cFLIP and Bcl-2 were down-regulated upon treatment with the dual APL. The dual APL also increased phosphorylation of the mitogen-activated protein kinases, c-Jun-NH2-terminal kinase and p-38, known to play a role in the regulation of FasL expression. Further, in the T cell line incubated with the dual APL as well as in mice of the SJL inbred strain immunized with the myasthenogenic peptide and treated concomitantly with the dual APL, the percentage of apoptotic cells increased. Results strongly indicate that up-regulation of apoptosis via the Fas-FasL pathway is one of the mechanisms by which the dual APL reverses EAMG manifestations in C57BL/6 mice.

Down-regulation of T cell responses to AChR and reversal of EAMG manifestations in mice by a dual altered peptide ligand via induction of CD4+CD25+ regulatory cells

A dual altered peptide ligand (APL) composed of the tandemly arranged two single amino acid analogs of two myasthenogenic peptides, p195-212 and p259-271 was demonstrated to down-regulate in vitro and in vivo myasthenia gravis (MG) associated autoreactive responses. In this study, we demonstrate the suppressive properties of the dual APL following immunization with the whole Torpedo AChR (TAChR) and in mice with established experimental autoimmune MG (EAMG). The dual APL acts by up-regulating CD4+ CD25+ cells expressing characteristic regulatory markers along with an associated increase in levels of IL-10 and TGF-beta. The latter cytokine plays a key role in the ameliorating effects of the dual APL.

Suppression of myasthenogenic responses of a T cell line by a dual altered peptide ligand by induction of CD4+CD25+ regulatory cells

Myasthenia gravis is a T cell-dependent, antibody-mediated autoimmune disease. A dual altered peptide ligand (APL) that is composed of the tandemly arranged two single amino acid analogs of two myasthenogenic peptides, p195-212 and p259-271, was demonstrated to down-regulate in vitro and in vivo myasthenia gravis-associated autoreactive responses. The aims of this study were to demonstrate the suppressive properties and to elucidate the mechanism of action of the dual APL on a T cell line specific to the myasthenogenic peptide p195-212. We demonstrate here that incubation of cells of the line with the dual APL resulted in the inhibition of proliferation and secretion of IL-2 and IFN-gamma triggered by p195-212. In contrast, secretion of TGF-beta and IL-10 was upregulated. The dual APL induced the generation of CD4+CD25+ cells that were characterized by the expression of CD45Rb(low), cytotoxic T lymphocyte-associated antigen-4, TGF-beta, CD62L, Foxp3, and neuropilin. In addition, the dual APL-treated cells were capable of inhibiting the proliferation response of the line when the two sets of cells were cocultured. The role of CD4+CD25+ cells was further confirmed by demonstrating that the suppression was abrogated by blocking/neutralization of CD25. Thus, the dual APL acts by inducing the formation of CD4+CD25+ regulatory cells. By using a T cell line, we could show that the immunosuppressive CD4+CD25+ cells were indeed induced by the dual APL and are not part of the naturally occurring regulatory cells.

Immunomodulation by a dual altered peptide ligand of autoreactive responses to the acetylcholine receptor of peripheral blood lymphocytes of patients with myasthenia gravis

Myasthenia gravis (MG) is a T cell-dependent, antibody-mediated autoimmune disease. A dual altered peptide ligand (APL) that is composed of the tandemly arranged two single amino acid analogs of two myasthenogenic peptides was demonstrated to downregulate in vitro and in vivo murine MG associated autoreactive responses. Furthermore, treatment with the dual APL ameliorated the clinical manifestations of an established experimental autoimmune MG in mice. This study was undertaken in order to investigate the ability of the dual APL to immunomodulate MG-associated responses of peripheral blood lymphocytes (PBL) of patients with MG to the native autoantigen acetylcholine receptor (AChR). PBL of 22 of 27 patients with MG tested responded by proliferation to torpedo AChR. The proliferative responses of PBL of 21 of 22 responders were significantly inhibited by the dual APL. The inhibition was specific because a control peptide did not inhibit these proliferative responses. The dual APL also downregulated the levels of the secreted pathogenic cytokine IFN-gamma in supernatants of stimulated PBL of 80% of the tested patients. The latter inhibitions correlated with an upregulated production of the immunosuppressive cytokine, tumor growth factor beta. Thus, the results of our study demonstrate that the dual APL is capable of downregulating in vitro autoreactive responses of patients with MG and suggest that this peptide is a potential candidate for a novel specific treatment of patients with MG.

Down-regulation of myasthenogenic T cell responses by a dual altered peptide ligand via CD4+CD25+-regulated events leading to apoptosis

The myasthenogenic peptides p195-212 and p259-271 are sequences of the human acetylcholine receptor and were shown to induce myasthenia gravis-associated immune responses in mice. A dual altered peptide ligand (APL) composed of the two APLs of the myasthenogenic peptides inhibited, in vitro and in vivo, those responses. The aims of this study were to elucidate the events that follow the in vivo treatment with the dual APL and to characterize the cell population that is induced by the latter. We demonstrate here that s.c. administration of the dual APL up-regulates CD4+CD25+ regulatory T cells that are characterized by up-regulated expression of cytotoxic T lymphocyte-associated antigen 4, intracellular and membranal TGF-beta, and Foxp3. Administration of the dual APL to mice concomitant with the immunization with either of the myasthenogenic peptides resulted also in the up-regulation of c-Jun-NH2-terminal kinase activity and of Fas signaling pathway molecules as determined by measuring Fas, Fas ligand, and caspase 8. Thus, our results suggest that the suppression of myasthenia gravis-associated T cell responses exerted by the dual APL is mediated by the CD4+CD25+ immunoregulatory T cell function via TGF-beta or cytotoxic T lymphocyte-associated antigen 4, which further stimulate a cascade of events that up-regulates apoptosis.

Therapeutic vaccines in autoimmunity

Similarly to prophylactic vaccines whose purpose is to prevent infectious diseases, therapeutic vaccines against autoimmune diseases are based on their similarity to the putative causes of the disease. We shall describe here two such examples: a copolymer of amino acids related to myelin basic protein, in the case of multiple sclerosis, and a peptide derived from the nicotinic acetylcholine receptor (AChR), in the case of myasthenia gravis (MG). Copolymer 1 (Cop 1, glatiramer acetate, Copaxone) is a synthetic amino acid random copolymer, immunologically cross-reactive with myelin basic protein and suppresses experimental allergic encephalomyelitis in several animal species. Cop 1 slows the progression of disability and reduces relapse rate in exacerbating-remitting multiple sclerosis patients. It was approved by the Food and Drug Administration in 1996, and today is used by tens of thousands of patients. Cop 1 is a potent inducer of T helper 2 (Th2) regulatory cells in mice and humans, and Th2 cells are found both in the brains and spinal cords of Cop 1-treated mice. MG and experimental autoimmune MG are T cell-regulated, antibody-mediated autoimmune diseases. Two peptides, representing sequences of the human AChR alpha-subunit, p195-212 and p259-271, are immunodominant T cell epitopes in MG patients and in two strains of mice. Altered peptide ligand, composed of the tandemly arranged two single amino acid analogs, inhibits in vitro and in vivo MG-associated autoimmune responses. The active suppression is mediated by the CD4(+)CD25(+) immunoregulatory cells and is associated with the down-regulation of Th1-type cytokines and the up-regulation of the secretion of IL-10 and the immunosuppressive cytokine, transforming growth factor beta.

An altered peptide ligand inhibits the activities of matrix metalloproteinase-9 and phospholipase C, and inhibits T cell interactions with VCAM-1 induced in vivo by a myasthenogenic T cell epitope

Myasthenia gravis (MG) is a T cell-regulated, antibody-mediated autoimmune disease. Immunization with two myasthenogenic peptides, p195-212 and p259-271, which are sequences of the human acetylcholine receptor, resulted in MG-associated immune responses. A dual altered peptide ligand (APL) composed of the two APLs of the myasthenogenic peptides inhibited, in vitro and in vivo, those responses. This study was aimed at understanding the mechanism(s) underlying the in vivo inhibitory properties of the dual APL. To this end, we analyzed T cells of mice that were immunized with p259-271 for their adhesiveness toward vascular cell adhesion molecule 1, for the activity of their secreted matrix metalloproteinases (MMPs), and for their intracellular phospholipase C (PLC) activity. Immunization with p259-271 triggered the above three activities and in vivo administration of the dual APL inhibited the latter. Thus, treatment of mice with the dual APL interferes with functions required for T cells to migrate and interact with the self-AChR. This is the first indication that very late antigen 4, MMP-9, and PLC are targets for immunomodulation of autoreactive T cells by altered peptide ligands.