Genetic control of resistance to clinical EAE accompanied by histological symptoms

Differential patterns of spinal cord pathology induced by MP4, MOG peptide 35-55, and PLP peptide 178-191 in C57BL/6 mice

In this study we demonstrate that experimental autoimmune encephalomyelitis (EAE) induced by the MBP-PLP fusion protein MP4, MOG peptide 35-55, or PLP peptide 178-191 in C57BL/6 mice, respectively, displays distinct features of CNS pathology. Major differences between the three models resided in (i) the region-/tract-specificity and disseminated nature of spinal cord degeneration, (ii) the extent and kinetics of demyelination, and (iii) the involvement of motoneurons in the disease. In contrast, axonal damage was present in all models and to a similar extent, proposing this feature as a possible morphological correlate for the comparable chronic clinical course of the disease induced by the three antigens. The data suggest that the antigen targeted in autoimmune encephalomyelitis is crucial to the induction of differential histopathological disease manifestations. The use of MP4-, MOG:35-55-, and PLP:178-191-induced EAE on the C57BL/6 background can be a valuable tool when it comes to reproducing and studying the structural-morphological diversity of multiple sclerosis.

Delineating the impact of neuroantigen vs genetic diversity on MP4-induced EAE of C57BL/6 and B6.129 mice

MBP-PLP fusion protein (MP4)-induced experimental autoimmune encephalomyelitis (EAE) is a model for multiple sclerosis (MS) that encompasses both a time-dependent attack on central nervous system (CNS) regions and a B cell component, mirroring important features of human multiple sclerosis. Comparing C57BL/6 with B6.129 mice immunized with MP4, we point out similarities regarding these hallmarks and thus propose that they are largely dependent on the nature of the MP4 antigen itself, while differences between the two strains suggest that additional fine-tuning is brought about by the genetic repertoire of the animal. Overall, our data imply that (i) the interplay between both the antigenic trigger and genetic variables can define the outcome of MP4-induced autoimmune encephalomyelitis in C57BL/6 and B6.129 mice and (ii) that MP4 is not only a strong neuroantigen when it comes to reproducing the dynamics in effector mechanisms as is typical of the disease but also a promising agent for studying interindividual heterogeneity derived from genetic diversity in EAE/MS.

Fundamental differences in the dynamics of CNS lesion development and composition in MP4- and MOG peptide 35-55-induced experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is characterized by a dynamic inflammatory process in which CNS lesions of distinct cellular composition coexist. In particular the formation of B cell plaques has been ascribed an important role as predictor of disease progression. Here we show that the novel MBP-PLP fusion protein (MP4)-induced experimental autoimmune encephalomyelitis (EAE) of C57BL/6 mice fulfils these criteria inducing differential cellular infiltration of B cells, T cells, macrophages and granulocytes and permitting the quantification and staging of the disease. On the contrary, both key features - dynamic CNS inflammation and B cell infiltration - were absent in the classical MOG:35-55-induced EAE of C57BL/6 mice, which was characterized by a static CD4(+) T cell and macrophage-mediated CNS immunopathology throughout the disease. MP4-induced EAE may thus provide a unique opportunity for studying immune-pathomechanisms of the disease that have been previously neglected due to experimental shortcomings in murine EAE.

Comparing the CNS morphology and immunobiology of different EAE models in C57BL/6 mice - a step towards understanding the complexity of multiple sclerosis

Multiple sclerosis (MS) is a chronic neurodegenerative disease that causes central nervous system (CNS) inflammation and demyelination, affecting approximately two million people worldwide. In humans, different subtypes of the disease have been noted, characterized by distinct clinical courses and different histopathological manifestations. These disease variants likely result from the targeting of different neuroantigens in the CNS and possibly from the involvement of different effector arms of the immune system such as CD4(+) and CD8(+) T cells as well as autoantibodies. Mechanistic studies addressing the pathomechanisms of MS involve experimental autoimmune encephalomyelitis (EAE) in which immunization with neuroantigens is used to elicit the disease. Mechanism-oriented studies of EAE rely mostly on gene-modified mice on the C57BL/6 (B6) background. Here, we discuss how a systematic immuno- and histopathological comparison of the presently available EAE models on the B6 background, i.e. myelin basic protein-proteolipid protein (MBP-PLP) fusion protein (MP4)-, myelin oligodendrocyte glycoprotein (MOG) peptide 35-55- and PLP peptide 178-191-induced EAE, can facilitate our understanding of the complexity of MS. We point out how the development of further models on this basis can help cover the plethora of disease manifestations seen in MS.

MP4- and MOG:35-55-induced EAE in C57BL/6 mice differentially targets brain, spinal cord and cerebellum

Mechanism-oriented studies of EAE rely mostly on gene-modified mice on the C57BL/6 background. Here we report that MP4-induced EAE displays characteristic differences in CNS pathology as compared to MOG peptide 35-55-elicited disease. While in the latter, the topology of CNS infiltration remained unchanged throughout the disease, in MP4-induced EAE it was dynamic and stage-dependent shifting from the brain to the spinal cord and finally to the cerebellum. Unlike in the MOG peptide model, the frequencies and sizes of CNS lesions in MP4-induced disease showed a clear correlation with clinical disease severity. These characteristic features of MP4-induced EAE may contribute to modelling the complex spectrum of disease manifestations seen in MS.

MBP-PLP fusion protein-induced EAE in C57BL/6 mice

Gene knock-out and knock-in mice are becoming increasingly indispensable for mechanism-oriented studies of EAE. Most gene-modified mice are on the C57BL/6 background, for which presently there are only two EAE models available, the MOG peptide 35-55 and the PLP 178-191 peptide induced disease. However, because MS is not a single pathogenic entity, different EAE models are required to reproduce and study its various features. Here we are introducing MBP-PLP fusion protein (MP4)-induced EAE for C57BL/6 mice. B cell- and CD8+ T cell-dependence, as well as multi-determinant recognition are among the unique features of this demyelinating EAE.

Antisecretory factor expression is regulated by inflammatory mediators and influences the severity of experimental autoimmune encephalomyelitis

Antisecretory factor (ASF) was originally identified as a potent inhibitor of intestinal fluid secretion induced by a number of enterotoxins. In addition to its involvement in intestinal fluid secretion, ASF modulates the proliferation of memory/effector T cells and is expressed by cells of the immune system. This report describes the role of ASF in modulating immune responses and assesses the regulation of ASF during an in vivo immunological reaction. ASF expression was redistributed during adoptively transferred experimental autoimmune encephalomyelitis (EAE), and in response to other inflammatory stimuli. Administration of the anti-ASF antibody TLD-1A8A increased the clinical severity and duration of the disease. Consistent with these findings, addition of TLD-1A8A to T cell proliferation assays resulted in up-regulation of the proinflammatory cytokines IL-18 and IL-6 and in down-regulation of IL-10. Furthermore, we identified cytokines that regulated the expression of ASF at both the mRNA and protein level. ASF, therefore, appears to play a previously unappreciated and potentially important role in the regulation of immune responses.

The Wistar Kyoto (RT1(l)) rat is resistant to myelin basic protein-induced experimental autoimmune encephalomyelitis: comparison with the susceptible Lewis (RT1(l)) strain with regard to the MBP-directed CD4+ T cell repertoire and its regulation

Here, we demonstrate that the Wistar Kyoto (WKY/NHsd) rat, which bears the same RT1(l) haplotype as the experimental autoimmune encephalomyelitis (EAE)-susceptible Lewis rat strain, is highly resistant to myelin basic protein (MBP)-induced EAE. No differences between Lewis and WKY strains were found in T cell proliferative specificity or the use of Vbeta8.2 T cell receptors in response to MBP. A Th2 cytokine bias correlated with WKY's EAE resistance. MBP challenge of WKY-into-Lewis adoptive transfer recipients produced a novel biepisodic EAE. The WKY strain should be useful in studies of many tissue-specific autoimmune diseases to which the Lewis rat is susceptible.

Regulatory T cells in experimental allergic encephalomyelitis. III. Comparison of disease resistance in Lewis and Fischer 344 rats

Rats of the Fischer 344 (F344) strain are resistant to experimental allergic encephalomyelitis (EAE) induced by active immunization with guinea pig myelin basic protein (MBP) in complete Freund's adjuvant whereas Lewis (LEW) rats are susceptible even though both strains share the same I-A-like class II alleles of the MHC RT1.B locus. To determine factors that might contribute to this difference in disease susceptibility, we have compared in these two strains (1) the frequency of MBP-reactive T cells in the lymph nodes and spleens of MBP-immunized animals, (2) the dominant MBP epitopes recognized by responding T cells, (3) the ability of MBP-reactive T cells to enter the central nervous system (CNS), and (4) the frequency of CD8+ regulatory T cells (RTC) whose activity is functionally antagonistic to MBP-reactive T cells. The results indicate that MBP-reactive T cell numbers are similar in MBP-immunized F344 and LEW rats, they both recognize p68-88 as the dominant encephalitogenic epitope of MBP, and MBP-reactive T cells isolated from immunized rats and adoptively transferred to naive animals are similarly effective in penetrating the blood-brain barrier and entering the CNS, leading to pathogenesis in EAE. However, the frequency of RTC that functionally inhibit MBP-reactive T cells is greater in F344 rats.

A Genome-Wide Search Identifies Two Susceptibility Loci for Experimental Autoimmune Encephalomyelitis on Rat Chromosomes 4 and 10

Experimental autoimmune encephalomyelitis (EAE) is an autoimmune disease of the central nervous system that exhibits many pathologic similarities with multiple sclerosis. The genetic loci that contribute to mononuclear cell infiltration of the central nervous system and clinical manifestations of EAE in the rat were investigated in the F2 progeny of the highly susceptible Lewis and resistant Brown Norway strains. The data confirmed that the Lewis allele of a MHC-linked gene is necessary, but not sufficient, to confer EAE susceptibility in the F2 progeny. Subsequent analyses were thus restricted to the subset of the F2 animals with EAE-predisposing MHC genotypes. A genome-wide scan approach was performed using 103 microsatellite markers covering 85% of the genome. Two non-MHC regions were identified, one near the centromere of chromosome 4 and the other on the long arm of chromosome 10, that significantly contributed to the disease. In addition, three regions on chromosomes 9, 13, and 17 were suggestive for linkage. Congenic mapping is now needed to reduce the support intervals encoding the loci of interest to sizes amenable to physical mapping and to eventually demonstrate the involvement of some of the candidate genes of immunologic importance localized in these regions.

Cytokines in relapsing experimental autoimmune encephalomyelitis in DA rats: persistent mRNA expression of proinflammatory cytokines and absent expression of interleukin-10 and transforming growth factor-beta

Experimental autoimmune encephalomyelitis (EAE) in rats is typically a brief and monophasic disease with sparse demyelination. However, inbred DA rats develop a demyelinating, prolonged and relapsing encephalomyelitis after immunization with rat spinal cord in incomplete Freund's adjuvant. This model enables studies of mechanisms related to chronicity and demyelination, two hallmarks of multiple sclerosis (MS). Here we have investigated, in situ, the dynamics of cytokine mRNA expression in the central nervous system (CNS) and peripheral lymphoid organs (lymph node cells and splenocytes) of diseased DA rats. We demonstrate that peripheral lymphoid cells stimulated in vitro with encephalitogenic peptides 69-87 and 87-101 of myelin basic protein responded with high mRNA expression for proinflammatory cytokines; interferon-gamma, interleukin-12 (IL-12), tumour necrosis factors alpha and beta, IL-1 beta and cytolysin. A high expression of mRNA for these proinflammatory cytokines was also observed in the CNS where it was accompanied by classical signs of inflammation such as expression of major histocompatibility complex class I and II, CD4, CD8 and IL-2 receptor. The expression of mRNA for proinflammatory cytokines was remarkably long-lasting in DA rats as compared to LEW rats which display a brief and monophasic EAE. Furthermore, mRNAs for putative immunodownmodulatory cytokines, i.e. transforming growth factor-beta (TGF-beta), IL-10 and IL-4 were almost absent in DA rats, in both the CNS and in vitro stimulated peripheral lymphoid cells, while their levels were elevated in the CNS of LEW rats during the recovery phase. We conclude that the MS-like prolonged and relapsing EAE in DA rats is associated with a prolonged production of proinflammatory cytokines and/or low or absent production of immunodownmodulatory cytokines.

Memantine abrogates neurological deficits, but not CNS inflammation, in Lewis rat experimental autoimmune encephalomyelitis

Memantine, a clinically employed drug with N-methyl-D-aspartate (NMDA) receptor antagonistic effects, dose-dependently ameliorates neurological deficits in Lewis rat experimental autoimmune encephalomyelitis (EAE). Interestingly, this therapeutic effect was not due to dampened CNS inflammation, as assessed by immunohistochemical evaluation of spinal cord tissue. Furthermore, numbers of interferon gamma (IFN gamma) mRNA expressing cells were not decreased, as assessed by in situ hybridization. Systemic immunity in terms of numbers of IFN gamma secreting cells in response to immunodominant myelin basic protein (MBP) peptides ex vivo was not reduced, and non-toxic doses of memantine did not affect lymphocyte proliferation or IFN gamma secretion in vitro. Considering these findings, we hypothesize that effector mechanisms responsible for reversible neurological deficits in EAE may involve NMDA receptors, and this highlights neurons as targets during autoimmune neuroinflammation.

Cloning of myelin basic protein-reactive T cells from the experimental allergic encephalomyelitis-resistant rat strain, LER

Rats of the LER inbred strain are resistant to the active induction of experimental allergic encephalomyelitis (EAE), although they are susceptible to adoptively transferred EAE when they are injected with encephalitogenic T cells from EAE-susceptible Lewis rats. The mechanism of resistance remains to be elucidated. We report here that myelin basic protein (MBP)-specific T cells can be cloned from LER rats immunized with MBP, that these CD4+ LER T cells can recognize the encephalitogenic peptide (MBP-EP) and will divide vigorously when it is presented to them, and that these T cells bear V beta 8 + TCR chains. Nevertheless, in contrast to Lewis T cells with the same specificity and TCR beta chains, LER T cells from MBP-EP-specific clones cannot induce EAE when adoptively transferred into naive rats of either strain. Thus, LER T cells can assemble and use a TCR with the canonical encephalitogenic V beta 8.2-D beta-J beta region in response to immunization with MBP, yet they continue to display resistance to EAE.

Differential recognition of sequences within the encephalitogenic region of myelin basic protein capable of eliciting cell-mediated immune responses in experimental autoimmune encephalomyelitis

The fine specificity of myelin basic protein (MBP) epitopes capable of eliciting in vivo delayed-type hypersensitivity responses in Lewis rats with experimental autoimmune encephalomyelitis (EAE) was compared to those eliciting in vitro antigen-specific T cell proliferation and augmentation of disease transfer. Utilizing a panel of synthetic peptides with sequences representing the 68-86 region of guinea pig (GP-) or bovine myelin basic protein (B-MBP), animals were primed with one species of peptide and subsequently challenged with either the same peptide or peptides with truncations or substitutions representative of the other species of MBP. In regard to minimal length sequences capable of eliciting delayed-type hypersensitivity (DTH), rats primed with GP-MBP and complete Freund's adjuvant (CFA) exhibited a hierarchical pattern of responsiveness to challenge with a series of truncated peptides, ranking as follows: GP-68-86 > GP-72-86 > GP-68-84 > > GP-75-86 = no activity. This response pattern corresponds to that previously reported for T cell proliferation and activation for disease transfer. Furthermore, a comparison of these T cell-mediated immune parameters, as elicited by the substituted peptides, revealed the response patterns of DTH reactivity to be similar to that previously described for in vitro T cell proliferation with significant DTH responses generated only by the peptide species for which the animal was primed. In contrast, a cross-reactive pattern of recognition was observed in cells mediating disease transfer, with all four 68-86 sequences capable of augmenting activation for adoptive transfer of disease, regardless of the peptide species for which the animal was primed.(ABSTRACT TRUNCATED AT 250 WORDS)

Resident macrophages (ramified microglia) of the adult brown Norway rat central nervous system are constitutively major histocompatibility complex class II positive

A flow cytometric phenotype for isolated adult central nervous system (CNS) ramified microglia was previously defined (CD45low CD11b/c+) in the Lewis strain rat, that clearly distinguished these cells from all blood-derived leucocytes, the latter being CD45high. Consistent with the reported lack of major histocompatibility complex (MHC) expression in the CNS, isolated microglia were mostly MHC class II-. Employing these phenotypic criteria, we now show that a proportion of microglia in Brown Norway (BN) strain rats are constitutively MHC class II+. In spinal cord, up to 25% of microglia are distinctly positive and most have some level of expression. In situ staining of MHC class II+ microglial cells in BN rats indicates that positive cells are typical of ramified microglia on the grounds of both morphological appearance and anatomical location. In Lewis (LEW) rats, the few MHC class II-expressing cells isolated from the normal CNS are CD45high blood-derived cells and not resident microglia. After infection of both LEW and BN rats with a neurotropic murine hepatitis virus (MHV-JHM), MHC class II was rapidly upregulated on microglia in the BN but not in the LEW strain. In the latter, inflammatory cells were the predominant MHC class II-expressing population. Nevertheless, most microglia in the LEW strain could, after some delay, be induced to express MHC class II after transfer of an experimental autoimmune encephalomyelitis (EAE)-inducing encephalitogenic T cell line. Paradoxically, strains resistant to EAE (exemplified by the BN) contained more constitutive MHC class II-expressing microglia than susceptible ones, when a variety of strains were examined. The results clearly establish that the normal CNS may contain MHC class II-expressing cells that are a resident rather than a transient blood-derived population. It is significant that this expression is strain related, but there is no evidence that microglial cell constitutive MHC class II expression predisposes to EAE susceptibility.

Evidence for target tissue regulation of resistance to the induction of experimental allergic encephalomyelitis in AO rats

A myelin basic protein (MBP)-specific T cell line derived from F1 hybrids between experimental allergic encephalomyelitis (EAE)-susceptible DA (RT1avl) strain and EAE-resistant AO (RT1u) strain was capable of inducing clinical EAE in F1 hybrids and DA, but not in AO rats. In vitro restimulation with MBP presented by AO antigen-presenting cells (APC) resulted in the generation of a MBP-specific subline restricted by RT1u MHC products which induced clinical EAE in F1 hybrids but not in the AO parental strain. Deletion of hosts' leukocytes using sublethal irradiation and cytotoxic drugs did not abrogate the resistance of AO rats, which argues against the involvement of hosts' lymphoid cells in the regulation of autoagression. Thus, mechanism(s) regulating the activity of autoagressive T cells on functional elements in the target tissue might be responsible for differences in susceptibility to EAE.

Experimental allergic encephalomyelitis and corticosterone studies in resistant and susceptible rat strains

In an effort to understand the role of endogenous corticosterone production on the induction of experimental allergic encephalomyelitis (EAE) in rats, experiments in our study were performed using inbred rat strains that differ in basal corticosterone levels. Levels of corticosterone in serum samples were determined for LEW, WF, LER, and PVG rats, all of which had significantly lower corticosterone levels than BN or F344 rats. However, despite the twofold interstrain differences in basal concentrations, all animals tested showed considerable increases in corticosterone levels after being stressed by anesthesia. A series of determinations of steroid levels was made for LEW and BN rats during the postinflammatory periods of EAE induction; as expected, BN rats (EAE resistant) showed no change from their high basal levels, whereas LEW (EAE susceptible) showed consistent and long-lasting twofold increases in their circulating levels of corticosterone during the inflammatory process. Because the high corticosterone phenotype may be causally related to EAE resistance, [(BN x LEW) x BN]F1 backcross rats were tested for the possible coinheritance of the high corticosterone phenotype and EAE resistance. Contrary to the expectation of genetic linkage, our results demonstrate no correlation between the two genetic traits in this rat strain combination.

Genetic differences in the T cell receptor alleles of LEW rats and their encephalomyelitis-resistant derivative, LER, and their impact on the inheritance of EAE resistance

Experimental allergic encephalomyelitis (EAE) is an animal model for the human disease, multiple sclerosis. The LEW rat strain is very susceptible to induction of EAE, whereas the closely related, major histocompatibility complex (MHC)-identical, inbred strain LER is resistant. In this report, the two rat strains have been compared for differences at a number of immunologically relevant loci by restriction fragment length analysis and by nucleotide sequencing. A major difference between the two strains was discovered at the T cell receptor beta chain locus (TcR beta). Both variable (V beta 8) and constant (C beta 1) region elements of TcR beta showed allelic variation between LEW and LER. The known genetic influences in rat models of autoimmunity are currently limited to those encoded by the rat MHC, RT-1. In this study we report our characterization of the allelic differences in TcR beta chains between two rats which differ in their susceptibility to induced EAE, with the goal of understanding the role played by these allelic forms of TcR in the pathogenesis of EAE. The importance of the TcR beta allelic difference in resistance or susceptibility to EAE was assessed in a study of backcross rats scored for both EAE and for the novel LER TcR beta allele. We found that the TcR beta allele from the susceptible strain was present in three out of four susceptible rats, suggesting that it is an important, but not the only, genetic factor in EAE. Supporting this conclusion were the observations that 12 of 13 rats with homozygous LER-derived TCR beta alleles were resistant to EAE.