Adoptive transfer of experimental allergic encephalomyelitis and localization of the encephalitogenic epitope in the SWR mouse

Inhibition of CXCR2 signaling promotes recovery in models of multiple sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease characterized by demyelination/remyelination episodes that ultimately fail. Chemokines and their receptors have been implicated in both myelination and remyelination failure. Chemokines regulate migration, proliferation and differentiation of immune and neural cells during development and pathology. Previous studies have demonstrated that the absence of the chemokine receptor CXCR2 results in both disruption of early oligodendrocyte development and long-term structural alterations in myelination. Histological studies suggest that CXCL1, the primary ligand for CXCR2, is upregulated around the peripheral areas of demyelination suggesting that this receptor/ligand combination modulates responses to injury. Here we show that in focal LPC-induced demyelinating lesions, localized inhibition of CXCR2 signaling reduced lesion size and enhanced remyelination while systemic treatments were relatively less effective. Treatment of spinal cord cultures with CXCR2 antagonists reduced CXCL1 induced A2B5+ cell proliferation and increased differentiation of myelin producing cells. More critically, treatment of myelin oligodendrocyte glycoprotein peptide 35-55-induced EAE mice, an animal model of multiple sclerosis, with small molecule antagonists against CXCR2 results in increased functionality, decreased lesion load, and enhanced remyelination. Our findings demonstrate the importance of antagonizing CXCR2 in enhancing myelin repair by reducing lesion load and functionality in models of multiple sclerosis and thus providing a therapeutic target for demyelinating diseases.

Stem cell reconstitution of autoimmune T cell repertoires

Maintenance of T cell memory in autoimmune disease may be complex because the unending renewable supply of self provides an inherent high antigen load that effectively precludes clearance, and because the broad array of potential immunogenic targets provides extensive self-recognition plasticity. Autoimmunity is characterized by a dynamic self-recognition process in which the primary autoreactivity initiating disease is soon followed and often displaced by secondary neoautoreactivities, or epitope spreading, that emerge as a result of endogenous self-priming. Here we show that the autoimmune disease process involves a tertiary phase of self recognition characterized by stem cell reconstitution of autoreactive T cells that recapitulates the myelin self recognition process involved in disease initiation and spreading during experimental autoimmune encephalomyelitis (EAE). Our study indicates that sustained autoimmune memory may not simply be due to the persistence of long-lived memory T cells, but may also involve bone marrow regeneration and replacement of the autoreactive T cell repertoire.

A novel class II-binding motif selects peptides that mediate organ-specific autoimmune disease in SWXJ, SJL/J, and SWR/J mice

Idiopathic dilated cardiomyopathy (DCM) is responsible for approximately 25% of all cases of congestive heart failure. We have recently shown that immunization of autoimmune-susceptible SWXJ mice with whole cardiac myosin leads to T cell-mediated experimental autoimmune myocarditis (EAMC) and DCM. We have now identified two disease-inducing peptides from cardiac alpha-myosin heavy chain (CAMHC). Our approach involved the use of a novel MHC class II-binding motif contained in several peptides known to be immunogenic in SWXJ (H-2(q,s)) mice or in the parental SJL/J (H-2(s)) or SWR/J (H-2(q)) mouse strains. Two of four CAMHC peptides containing the -KXXS- peptide motif were found to be immunogenic. Immunization of SWXJ or parental SJL/J and SWR/J mice with CAMHC peptides palpha406-425 or palpha1631-1650 resulted in EAMC and DCM, characterized by inflammation, fibrosis, and decompensated right-sided ventricular dilatation. Despite mediating high incidences of severe disease, both peptides were found to be cryptic determinants, thereby providing further evidence for the importance and perhaps predominance of self crypticity in autoimmunity. Both peptides showed dual parental I-A(q) and I-A(s) restriction and mediated passive transfer of disease with activated CD4(+) T cells. An intact motif was necessary for antigenicity because loss of activity occurred in peptides containing nonconservative substitutions at the motif's terminal lysine and serine residues. Our studies provide a new model for EAMC and DCM in strains of mice widely used in autoimmune studies. Moreover, the -KXXS- motif may be particularly useful in implicating previously overlooked proteins as autoimmune targets and in facilitating the development of new organ-specific autoimmune mouse models for human diseases.

Influence of a dominant cryptic epitope on autoimmune T cell tolerance

The rules governing which T cells are inactivated during peptide-induced tolerance are unclear. Here we show that MBP(89-101) contains three overlapping but distinct T cell epitopes that are restricted by a single major histocompatibility complex (MHC) class II molecule. The dominant epitope is not processed from MBP and is not relevant to the induction of autoimmunity. Pathogenic T cells recognize two minor epitopes that are processed from MBP but are presented only poorly after exposure to MBP(89-101). Induction of immunological tolerance by MBP(89-101) therefore inactivates T cells that recognize the dominant epitope and disease-relevant T cells escape tolerance. The topology of the three epitopes implicates asparagine endopeptidase as the enzyme that controls recognition of this region of MBP. Our results highlight the need to use peptides that mimic the binding of processed antigen fragments to MHC molecules for successful modulation of disease-relevant T cells.

Expression of Golli mRNA during development in primary immune lymphoid organs of the rat

The gene-of-the-oligodendrocyte lineage (Golli)-MBP transcription unit contains three Golli-specific exons together with eight exons of the "classical" myelin basic protein (MBP) gene, yielding alternatively spliced proteins which share amino acid sequence with MBP. Unlike MBP, a late antigen expressed only in the nervous system, Golli gene products are expressed pre- and post-natally at many sites. In this study, we determined the sequence of Golli in rat by RT-PCR and 5' RACE and showed that Golli sequences are expressed in primary lymphoid organs as early as e16.5, which could explain the anergic rat T cell response we previously observed in Golli-induced meningitis.

Regression and spreading of self-recognition during the development of autoimmune demyelinating disease

The autoimmune T cell repertoire in experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS) is characterized by CD4(+)T cells of the Th1 phenotype that recognize peptide determinants of central nervous system (CNS) myelin proteins in an MHC class II-restricted manner. Our recent studies and those performed by others have shown that progression to chronicity in EAE and MS is accompanied by a broadening of the T cell repertoire with time. This acquired neo-autoreactivity is commonly referred to as epitope spreading and is presumably the result of endogenous priming to new self-determinants during the CNS inflammation that accompanies disease onset and relapse. In the present study we extend our earlier observations by showing that disease progression in both EAE and MS is accompanied by two concurrent events, viz. (1) the spontaneous regression of the primary established autoimmune repertoire associated with disease onset, and (2) the emergence of the epitope spreading cascade associated with disease progression. Our data show that disease initiation and disease progression in both EAE and MS are typically associated with distinctly different autoimmune T cell repertoires. Our data support the view that the natural development of self-recognition during autoimmune disease may best be understood when considered in the temporal context of an 'epitope du jour' and 'moving target' perspective.

Spontaneous regression of primary autoreactivity during chronic progression of experimental autoimmune encephalomyelitis and multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is a widely used animal model for multiple sclerosis (MS). EAE is typically initiated by CD4(+) T helper cell type 1 (Th1) autoreactivity directed against a single priming immunodominant myelin peptide determinant. Recent studies have shown that clinical progression of EAE involves the accumulation of neo-autoreactivity, commonly referred to as epitope spreading, directed against peptide determinants not involved in the priming process. This study directly addresses the relative roles of primary autoreactivity and secondary epitope spreading in the progression of both EAE and MS. To this end we serially evaluated the development of several epitope-spreading cascades in SWXJ mice primed with distinctly different encephalitogenic determinants of myelin proteolipid protein. In a series of analogous experiments, we examined the development of epitope spreading in patients with isolated monosymptomatic demyelinating syndrome as their disease progressed to clinically definite MS. Our results indicate that in both EAE and MS, primary proliferative autoreactivity associated with onset of clinical disease invariably regresses with time and is often undetectable during periods of disease progression. In contrast, the emergence of sustained secondary autoreactivity to spreading determinants is consistently associated with disease progression in both EAE and MS. Our results indicate that chronic progression of EAE and MS involves a shifting of autoreactivity from primary initiating self-determinants to defined cascades of secondary determinants that sustain the self-recognition process during disease progression.

The epitope spreading cascade during progression of experimental autoimmune encephalomyelitis and multiple sclerosis

We have made the following observations regarding self-recognition during the development and progression of murine experimental autoimmune encephalomyelitis (EAE) and human multiple sclerosis (MS): 1) chronic progression of EAE is accompanied by a sequential, predictable cascade of neo-autoreactivity, commonly referred to as epitope spreading, presumably caused by endogenous self-priming during autoimmune-mediated tissue damage; 2) there is an invariant relationship between the progression of EAE and the emergence of epitope spreading; 3) progression of EAE can be inhibited by the induction of antigen-specific tolerance to spreading determinants after onset of initial neurologic symptoms; 4) CD4+ Th 1 cells responding to spreading determinants are autonomously encephalitogenic; 5) epitope spreading occurs during the development of MS and in some cases involves HLA-DP class II-restricted self-recognition; and 6) progression of both EAE and MS is accompanied by the decline of primary T-cell autoreactivity associated with disease onset and by the concurrent emergence of the epitope spreading cascade. Our studies directly challenge the traditional view that EAE and MS are initiated and maintained by autoreactivity directed against a single predominant myelin protein or determinant. Our results indicate that progression of EAE and MS involves a shifting of T-cell autoreactivity from primary initiating self-determinants to defined cascades of secondary determinants that sustain the inflammatory self-recognition process during disease progression.

Immunomodulating therapeutic approaches for multiple sclerosis

In this review we delineate the rationale for immunotherapy in multiple sclerosis and describe the various levels at which immune intervention, according to a modern model of the immune system organization, is feasible. Current and future immunosuppressive and immunomodulating therapeutic approaches at the level of antigen presentation and at the lymphocyte and cytokine network levels are discussed.

A predictable sequential determinant spreading cascade invariably accompanies progression of experimental autoimmune encephalomyelitis: a basis for peptide-specific therapy after onset of clinical disease

The development of autoimmune disease is accompanied by the acquired recognition of new self-determinants, a process commonly referred to as determinant spreading. In this study, we addressed the question of whether determinant spreading is pathogenic for progression of chronic-relapsing experimental autoimmune encephalomyelitis (EAE), a disease with many similarities to multiple sclerosis (MS). Our approach involved a systematic epitope mapping of responses to myelin proteolipid protein (PLP) as well as assaying responses to known encephalitogenic determinants of myelin basic protein (MBP 87-89) and myelin oligodendrocyte glycoprotein (MOG 92-106) at various times after induction of EAE in (SWR X SJL)F1 mice immunized with PLP 139-151. We found that the order in which new determinants are recognized during the course of disease follows a predictable sequential pattern. At monthly intervals after immunization with p139-151, responses to PLP 249-273, MBP 87-99, and PLP 137-198 were sequentially accumulated in al mice examined. Three lines of evidence showed that determinant spreading is pathogenic for disease progression: (a) spreading determinants mediate passive transfer of acute EAE in naive (SWR X SJL)F1 recipients; (b) an invariant relationship exists between the development of relapse/progression and the spreading of recognition to new immunodominant encephalitogenic determinants; and (c) after EAE onset, the induction of peptide-specific tolerance to spreading but not to nonspreading encephalitogenic determinants prevents subsequent progression of EAE. Thus, the predictability of acquired self-determinant recognition provides a basis for sequential determinant-specific therapeutic intervention after onset of the autoimmune disease process.

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.

Encephalitogenicity of myelin basic protein exon-2 peptide in mice

Immunization with a synthetic peptide with an amino acid sequence corresponding to mouse myelin basic protein exon-2 induced mild experimental allergic encephalitis (EAE) in B10.RIII mice, very mild disease in SJL/J mice and no disease in (SJL x PL)F1 hybrid mice. In contrast, adoptive transfer of an exon-2 peptide-specific T cell line from SJL mice induced severe relapsing EAE in syngeneic recipients. The T cell line was specific for exon-2 peptide and did not cross-react appreciably with an MBP preparation consisting of the 18.5 and 14-kDa isoforms. mRNA for exon-2 containing isoforms could be demonstrated in the spinal cord of SJL/J and B10.RIII mice by amplification using exon-2 and exon-4 oligonucleotide primers. On a relative basis, the level of exon-2 cDNA was lower than that of exon-1 cDNA in the same spinal cord preparations from both strains of mice.

Effects of laminin monoclonal antibodies on the development of cultured rat embryos

Whole rat embryos (9.5 days of gestation) were exposed to six different monoclonal antibodies to laminin during 48 hr of culture. Four (LAM I, LAM V, 5A2, 9D2) of the six were teratogenic or lethal and two (LAM II, 5D3) were not toxic at comparable levels. Teratogenicity and lethality were not related to antibody level, subclass or affinity for whole laminin. Indirect immunofluorescence studies using mouse embryo sections revealed that the toxic antibodies bound in a diffuse manner, while the nontoxic antibodies showed distinct labeling of tissues. These observations suggest that previous varied responses seen in cultured rat embryos exposed to laminin antibodies obtained from humans, monkeys, and rats were the result of differences in the epitope specificity of those antibodies.

Homing of T cells to the central nervous system throughout the course of relapsing experimental autoimmune encephalomyelitis in Thy-1 congenic mice

Chronic relapsing experimental allergic encephalomyelitis (EAE) was induced in Thy-1.1 congenic SJL/J mice by the adoptive transfer of myelin basic protein (MBP)-responsive lymph node cells from Thy-1.2 SJL/J mice. The Thy-1 congenic mouse strain was constructed on the SJL (Thy-1.2) background by the initial cross with the AKR (Thy-1.1) strain and does not reject Thy-1.2+ T cells. Quantitative immunocytochemical analysis of the central nervous system (CNS) of Thy-1.1 recipients showed preferential trafficking of Thy-1.2+ T cells to the meninges and white matter, beginning prior to onset of clinical signs. At 7 days post-transfer (dpt), Thy-1.2+ donor cells constituted 2.5% of the infiltrating cells and reached peak values (ca. 10%) during the first attack. At later stages (up to ten relapses), Thy-1.2+ T cells constituted 2-5% of the infiltrate. In control mice injected with irrelevant antigen-stimulated Thy-1.2+ T cells, only the occasional Thy-1.2+ T cell could be demonstrated up to 14 dpt. This is the first study showing unequivocally the presence of MBP-stimulated, adoptively transferred T cells within the CNS of recipients throughout the course of EAE, particularly during later relapsing stages. These results indicate that the persistent presence of antigen-specific T cells may be required for the recruitment of non-CNS antigen-responsive immune cells.

Myelin proteolipid protein: minimum sequence requirements for active induction of autoimmune encephalomyelitis in SWR/J and SJL/J mice

Proteolipid protein (PLP) is the major protein constituent of mammalian central nervous system myelin. We have previously identified two different PLP encephalitogenic T cell epitopes in two mouse strains. Murine PLP peptides 103-116 YKTTICGKGLSATV and 139-151 HCLGKWLGHPDKF are encephalitogenic determinants in SWR/J (H-2q) and SJL/J (H-2s) mice, respectively. The purpose of the present study was to determine the minimum sequence requirements for each of these PLP encephalitogens. In SWR/J mice, at least two distinct overlapping peptides can induce experimental autoimmune encephalomyelitis (EAE). The eleven residue sequences PLP 105-115 TTICGKGLSAT and PLP 106-116 TICGKGLSATV are encephalitogenic in SWR/J mice, but PLP 106-115 TICGKGLSAT, the decapeptide indigenous to both sequences, is non-encephalitogenic. In contrast, the shortest PLP sequence capable of inducing EAE in SJL/J mice is the nonapeptide 141-149 LGKWLGHPD. These data indicate that encephalitogenic determinants of PLP are short contiguous peptide sequences similar in length and diversity to those of MBP.

The synthetic 87–99 peptide of myelin basic protein is encephalitogenic in Buffalo rats

A synthetic peptide corresponding to residues 87-99 (S87-99) of myelin basic protein (BP) induced the proliferation of an encephalitogenic, BP-specific T cell line selected in vitro from inbred Buffalo-strain rats (RT1b). Active immunization with guinea pig (GP)-BP or S87-99 in complete Freund's adjuvant (CFA) and intravenous pertussigen induced acute experimental autoimmune encephalomyelitis (EAE) 10-12 days after immunization. Fifty percent of recovered rats developed a single relapse 17-21 days after immunization. T lymphocytes selected in vitro with S87-99 transferred acute, non-relapsing EAE into naive recipients. Histological examination during acute EAE revealed foci of inflammatory cells associated with demyelination in the spinal cords and peripheral nerve roots. Thus, as in several other rodent strains, the 87-99 region of BP is antigenic and encephalitogenic in the inbred Buffalo-strain rat. Additionally, the 87-99 sequence of GP-BP was predicted to be antigenic by two different methods. These results suggest that the 87-99 region of BP, which is highly conserved among mammalian species, may be widely encephalitogenic due to antigen-intrinsic properties.