Peptide determinants of myelin proteolipid protein (PLP) in autoimmune demyelinating disease: a review

Diversity and plasticity of self recognition during the development of multiple sclerosis

Recent studies using murine animal model systems indicate that clinical progression of autoimmune disease may be due to the sequential accumulation of neoautoreactivity characterized by extensive plasticity of self recognition. In the present study, we addressed the question of whether a similar paradigm of self recognition is implicated in the development of multiple sclerosis (MS), a demyelinating disease with a presumed autoimmune etiology. Our approach was to determine serial changes over a 12-18-mo period in response to an epitope-mapping series of 265 12-mer peptides of myelin proteolipid protein (PLP) by patients with isolated monosymptomatic demyelinating syndromes (IMDS), a group of distinct clinical disorders with variable rates of progression to MS. Our data showed that an extensive array of proteolipid protein peptides could elicit autoreactivity. Moreover, differential autoreactive patterns were evident within IMDS patient subpopulations. Monocentric monophasic IMDS patients with no evidence of prior subclinical disease typically showed fully sustained autoreactivity characterized by extensive plasticity, epitope focusing, shifting, and spreading of responses to new self determinants. In contrast, multicentric monophasic IMDS patients with putative evidence of prior asymptomatic lesion formation typically showed partially sustained autoreactivity characterized by abrupt abrogation of responses to an extensive array of self determinants. No sustained autoreactivity was observed in normal control subjects or in patients with other neurologic diseases. Our results indicate that self recognition associated with the development of MS is a developmental process characterized by autoreactive diversity, plasticity, and instability.

Treatment of experimental encephalomyelitis with a novel chimeric fusion protein of myelin basic protein and proteolipid protein

It has been shown that peripheral T cell tolerance can be induced by systemic antigen administration. We have been interested in using this phenomenon to develop antigen-specific immunotherapies for T cell-mediated autoimmune diseases. In patients with the demyelinating disease multiple sclerosis (MS), multiple potentially autoantigenic epitopes have been identified on the two major proteins of the myelin sheath, myelin basic protein (MBP) and proteolipid protein (PLP). To generate a tolerogenic protein for the therapy of patients with MS, we have produced a protein fusion between the 21.5-kD isoform of MBP (MBP21.5) and a genetically engineered form of PLP (deltaPLP4). In this report, we describe the effects of treatment with this agent (MP4) on clinical disease in a murine model of demyelinating disease, experimental autoimmune encephalomyelitis (EAE). Treatment of SJL/J mice with MP4 after induction of EAE either by active immunization or by adoptive transfer of activated T cells completely prevented subsequent clinical paralysis. Importantly, the administration of MP4 completely suppressed the development of EAE initiated by the cotransfer of both MBP- and PLP-activated T cells. Prevention of clinical disease after the intravenous injection of MP4 was paralleled by the formation of long-lived functional peptide-MHC complexes in vivo, as well as by a significant reduction in both MBP- and PLP-specific T cell proliferative responses. Mice treated with MP4 were resistant to disease when rechallenged with an encephalitogenic PLP peptide emulsified in CFA, indicating that MP4 administration had a prolonged effect in vivo. Administration of MP4 was also found to markedly ameliorate the course of established clinical disease. Finally, MP4 therapy was equally efficacious in mice defective in Fas expression. These results support the conclusion that MP4 protein is highly effective in suppressing disease caused by multiple neuroantigen epitopes in experimentally induced demyelinating disease.

Delineation of the minimal encephalitogenic epitope within the immunodominant region of myelin oligodendrocyte glycoprotein: diverse V beta gene usage by T cells recognizing the core epitope encephalitogenic for T cell receptor V beta b and T cell receptor V beta a H-2b mice

The nature of the autoimmune T cell response to myelin oligodendrocyte glycoprotein (MOG), recently recognized as a potential target antigen in multiple sclerosis (MS), has not yet been characterized, in contrast to the T cell reactivity to other potential target antigens in MS such as myelin basic protein and proteolipid protein. Here, we show that the encephalitogenicity of the recombinant Ig-like domain of human MOG is associated, in H-2 b mice, with an immunodominant T cell reactivity against a single region of MOG spanning amino acids 35-55, accounting for the previously reported strong encephalitogenic activity of pMOG 35-55. A single injection of pMOG 35-55 with or without administration of pertussis toxin was sufficient to induce severe clinical experimental autoimmune encephalomyelitis (EAE) in H-2 b mice. Encephalitogenic pMOG 35-55-specific T cell lines derived from C3H.SW (V beta b) mice were diverse in their TCR V beta gene usage (V beta 1, V beta 6, V beta 8 and V beta 15), although V beta 8.2 was most predominantly expressed (48%). However, V beta 8 + T cells may only be part of the encephalitogenic MOG-specific T cell repertoire in H-2 b mice, as demonstrated by the susceptibility of C57L (V beta a) mice to disease induced by pMOG 35-55. Encephalitogenic T cell lines from V beta a mice were also diverse in their TCR V beta gene usage (V beta 1, V beta 2, V beta 6, V beta 14 and V beta 16). Such a heterogeneous TCT V beta gene expression by pMOG 35-55/I-A b-reactive T cells from both V beta a and V beta b H-2 b mice suggested multiple epitopes within pMOG 35-55. Analysis of the pattern of reactivity by pMOG 35-55-reactive T cells to a set of truncated peptides was not commensurate with independent nested epitopes, but revealed a requirement for recognition of a core sequence, YRSPFSRVV (pMOG 40-48). However, optimal stimulation was obtained with longer peptides, with each additional amino acid flanking either the N or the C terminus differentially increasing the stimulatory capacity of pMOG 40-48. Nonetheless, pMOG 40-48 was the minimal encephalitogenic epitope for both V beta a and V beta b mice. Thus, the T cell reactivity against the immunodominant encephalitogenic region of MOG is characterized by a diverse V beta gene usage and a requirement for the same core epitope. This pattern of reactivity may favor epitope-directed, rather than TCR-targeted, approaches to immunospecific therapy for MOG-related autoimmune disease.

Antibody facilitation of multiple sclerosis-like lesions in a nonhuman primate

In the human disease multiple sclerosis (MS), the immune mechanisms responsible for selective destruction of central nervous system myelin are unknown. In the common marmoset Callithrix jacchus, a unique demyelinating form of experimental allergic encephalomyelitis resembling MS can be induced by immunization with whole myelin. Here we show that the MS-like lesion can be reproduced by immunization against the extracellular domain of a single myelin protein, myelin/oligodendrocyte glycoprotein (MOG). By contrast, immunization against the quantitatively major myelin proteins myelin basic protein or proteolipid protein results in inflammation but little or no demyelination. Furthermore, in the presence of encephalitogenic (e.g., disease-inducing) T cells, the fully demyelinated lesion is reconstructed by systemic administration of IgG purified from whole myelin-, or MOG-immunized animals, and equally by a monoclonal antibody against MOG, but not by control IgG. Encephalitogenic T cells may contribute to the MS-like lesion through disruption of the blood-brain barrier that permits access of demyelinating antibody into the nervous system. The identification of MOG as a major target antigen for autoimmune demyelination in a nonhuman primate should facilitate development of specific immunotherapies for human MS.

Experimental autoimmune encephalomyelitis in rodents as a model for human demyelinating disease

The cause of multiple sclerosis (MS) is unknown, but the pathology is consistent with an immunological etiology. Studies conducted with the animal model of MS, experimental autoimmune encephalomyelitis (EAE), have provided insight into how the immune system can provoke an immunopathological response characteristic of that seen in MS. The use of inbred rats and mice for studies of EAE has been especially rewarding with respect to the identification of the epitopes of encephalitogenic antigens responsible for the induction of this autoimmune disease and in elucidating the effector mechanism underlying EAE. Moreover, it has also been possible to ascertain how EAE can be regulated, leading to therapeutic modalities which have been applied in clinical studies of MS patients. This review briefly summarizes studies of EAE in rodents, drawing comparisons with immunological findings reported in patients with MS. It is clear that important lessons can be learned from the detailed investigation of animal models that may be applicable to human immunological disorders.

A myelin oligodendrocyte glycoprotein peptide induces typical chronic experimental autoimmune encephalomyelitis in H-2b mice: fine specificity and T cell receptor V beta expression of encephalitogenic T cells

A predominant response to myelin oligodendrocyte glycoprotein (MOG) was recently observed in patients with multiple sclerosis (MS). To study the possible pathogenic role of T cell response to MOG in MS, we have investigated the encephalitogenic potential of MOG. Synthetic MOG peptides, pMOG 1-21, 35-55, 67-87, 104-117 and 202-218, representing predicted T cell epitopes, were injected into C57BL/6J and C3H.SW (H-2b) mice. The mice developed significant specific T cell responses to pMOG 1-21, pMOG 35-55 and pMOG 104-117. However, pMOG 35-55 was the only MOG peptide which could induce neurological impairment. The highly reproducible disease was chronic, with ascending paralysis and neuropathology comparable with those observed in experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein or proteolipid protein, except that in H-2b mice the disease was consistently non-remitting. These features differ markedly from those which we recently observed in PL (H-2u) mice with pMOG 35-55-induced disease. In PL mice, pMOG 35-55-induces atypical chronic relapsing EAE, the expression and progression of which are unpredictable. Hence, in different mouse strains, the same MOG peptide can induce typical EAE characterized by ascending paralysis, or atypical EAE with unpredictable clinical signs. pMOG 35-55-specific T cells from H-2b mice recognized an epitope within amino acids 40-55 of the MOG molecule, and pMOG 40-55-reactive T cell lines were encephalitogenic upon transfer into syngeneic recipients. The encephalitogenic pMOG 35-55-reactive C57BL/6J T cell lines expressed V beta 1, V beta 6, V beta 8, V beta 14 and V beta 15 gene segments, and the pMOG 35-55-reactive C3H.SW T cell lines expressed V beta 1, V beta 2, V beta 6, V beta 8, V beta 10, V beta 14, and V beta 15 gene segments. However, in both mouse strains, the utilization of the V beta 8 gene product was predominant (40-43%). The highly reproducible encephalitogenic activity of pMOG 35-55 strongly suggests a pathogenic role for T cell reactivity to MOG in MS and supports the possibility that MOG may also be a primary target antigen in the disease.

Determinant-regulated onset of experimental autoimmune encephalomyelitis: distinct epitopes of myelin proteolipid protein mediate either acute or delayed disease in SJL/J mice

In the present study we address the question of whether distinct self-determinants can target alternative autoimmune disease patterns in experimental autoimmune encephalomyelitis (EAE), an animal model widely used for studying multiple sclerosis. We have found that the clinical course of EAE can be determined by the target peptide selected for induction of disease. In SJL/J mice, actively induced and passively transferred EAE mediated by the immunodominant PLP determinants p139-151 and p178-191 consistently produced a rapid onset of severe clinical signs. In contrast, a delayed onset of both active and passive EAE is associated with the nondominant cryptic PLP determinant p104-117. The delayed disease induced with p104-117 is not associated with any unusual peptide feature, with bystander immunoregulation, with inept class II MHC binding, or with failure to induce T cell expression of CD44, VLA-4, or IL-2 receptor upon activation. However, delayed disease is associated with innate qualities of the T cell repertoire responding to the p104-117 determinant. T cell lines responding to the cryptic p104-117 show limited TCR-V beta utilization compared to the diverse repertoire responding to the dominant p139-151 determinant. The repertoire deletions are accompanied by low level production of pathogenic Th1 cytokines (IFN gamma; IL-2) and increased production of regulatory Th2 (IL-4) cytokine in activated p104-117 primed T cells. Thus, the delayed encephalitogenicity of p104-117 may be due to TCR-V beta deletions and activation defects in the responding T cell repertoire. The development of "slow disease" mediated by autoreactivity against hidden self-determinants may have important implications in the pathogenesis of both relapsing and chronic autoimmune demyelinating disease.

Self-determinants in autoimmune demyelinating disease: changes in T- cell response specificity

Recent research developments support the following views regarding antigen recognition in autoimmune demyelinating disease: there may be no single autoimmune target protein; diverse peptide self-determinants from multiple myelin proteins can be recognized; target determinant epitopes may differ among individuals; and target epitope recognition can change with time during the course of disease.