Identification of the encephalitogenic epitopes of CNS proteolipid protein in BALB/c mice

Active Induction of a Multiple Sclerosis-Like Disease in Common Laboratory Mouse Strains

Experimental autoimmune encephalomyelitis (EAE) is a neuroinflammatory disease with facets in common with multiple sclerosis (MS). It is induced in susceptible mammalian species, with rodents as the preferred hosts, and has been used for decades as a model to investigate the immunopathogenesis of MS as well as for preclinical evaluation of candidate MS therapeutics. Most commonly, EAE is generated by active immunization with central nervous system (CNS) antigens, such as whole CNS homogenate, myelin proteins, or peptides derived from these proteins. However, EAE actually represents a spectrum of diseases in which specific combinations of host/CNS antigen exhibit defined clinical profiles, each associated with unique immunological and pathological features. Similar to MS, EAE is a complex disease where development and progression are also modulated by environmental factors; therefore, the establishment of any given EAE variant can be challenging and requires careful optimization. Here, we describe protocols for three EAE variants, successfully generated in our laboratory, and provide additional information as to how to maintain their unique features and reproducibility.

Experimental Autoimmune Encephalomyelitis in the Mouse

This article details the materials and methods required for both active induction and adoptive transfer of experimental autoimmune encephalomyelitis (EAE) in the SJL mouse strain using intact proteins or peptides from the two major myelin proteins: proteolipid protein (PLP) and myelin basic protein (MBP). Additionally, active induction of EAE in the C57BL/6 strain using myelin oligodendrocyte glycoprotein (MOG) peptide is also discussed. Detailed materials and methods required for the purification of both PLP and MBP are described, and a protocol for isolating CNS-infiltrating lymphocytes in EAE mice is included. Modifications of the specified protocols may be necessary for efficient induction of active or adoptive EAE in other mouse strains. © 2021 Wiley Periodicals LLC. Basic Protocol: Active induction of EAE with PLP, MBP, and MOG protein or peptide Alternate Protocol: Adoptive induction of EAE with PLP-, MBP-, or MOG-specific lymphocytes Support Protocol 1: Purification of proteolipid protein Support Protocol 2: Purification of myelin basic protein Support Protocol 3: Isolation of CNS-infiltrating lymphocytes.

Animal Models of Multiple Sclerosis

Animal models with high translational validity are essential tools in understanding disease pathogenesis and in the development of therapeutic strategies. Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system characterized by progressive neurological deficits and socioeconomic burden. Experimental autoimmune encephalomyelitis (EAE) is the most extensively utilized animal model of MS, with well-characterized rodent and non-human primate variants. The EAE model is typically induced by either active immunization with myelin-derived proteins or peptides in adjuvant or by passive transfer of activated myelin-specific CD4⁺ T lymphocytes. To date, the EAE model has been an essential tool in the development of at least seven U.S. Food and Drug Administration (FDA)-approved immunomodulatory drugs for the treatment of MS, including glatiramer acetate, fingolimod, and natalizumab. However, the translational validity of the EAE model is frequently compromised due to poor study design, inconsistent clinical scoring endpoints, and inappropriate statistical calculations. No single animal model accurately reflects the complexity of human MS pathogenesis. Beyond EAE, multiple additional animal models are described, including Theiler's murine encephalomyelitis virus and cuprizone-induced demyelination, which facilitate the study of pathogen-induced CNS autoimmunity and remyelination, respectively. This overview summarizes several of the most frequently used animal models of MS and highlights key factors that significantly influence the experimental outcome and affect translational validity. © 2021 Wiley Periodicals LLC.

Development and Pre-Clinical Evaluation of Recombinant Human Myelin Basic Protein Nano Therapeutic Vaccine in Experimental Autoimmune Encephalomyelitis Mice Animal Model

Recombinant human myelin basic protein (rhMBP) was previously produced in the milk of transgenic cows. Differences in molecular recognition of either hMBP or rhMBP by surface-immobilized anti-hMBP antibodies were demonstrated. This indicated differences in immunological response between rhMBP and hMBP. Here, the activity of free and controlled release rhMBP poly(ε-caprolactone) nanoparticles (NPs), as a therapeutic vaccine against multiple sclerosis (MS) was demonstrated in experimental autoimmune encephalomyelitis (EAE) animal model. Following optimization of nanoformulation, discrete spherical, rough-surfaced rhMBP NPs with high entrapment efficiency and controlled release pattern were obtained. Results indicated that rhMBP was loaded into and electrostatically adsorbed onto the surface of NPs. Subcutaneous administration of free or rhMBP NPs before EAE-induction reduced the average behavioral score in EAE mice and showed only mild histological alterations and preservation of myelin sheath, with rhMBP NPs showing increased protection. Moreover, analysis of inflammatory cytokines (IFN-γ and IL-10) in mice brains revealed that pretreatment with free or rhMBP NPs significantly protected against induced inflammation.

IN CONCLUSION

i) rhMBP ameliorated EAE symptoms in EAE animal model, ii) nanoformulation significantly enhanced efficacy of rhMBP as a therapeutic vaccine and iii) clinical investigations are required to demonstrate the activity of rhMBP NPs as a therapeutic vaccine for MS.

Experimental Autoimmune Encephalomyelitis in Mice

Experimental autoimmune encephalitis (EAE), the animal model of multiple sclerosis (MS), has provided significant insight into the mechanisms that initiate and drive autoimmunity. Several central nervous system proteins and peptides have been used to induce disease, in a number of different mouse strains, to model the diverse clinical presentations of MS. In this chapter, we detail the materials and methods used to induce active and adoptive EAE. We focus on disease induction in the SJL/J, C57BL/6, and BALB/c mouse strains, using peptides derived from proteolipid protein, myelin basic protein, and myelin oligodendrocyte glycoprotein. We also include a protocol for the isolation of leukocytes from the spinal cord and brain for flow cytometric analysis.

Deletion of IL-4Rα in the BALB/c mouse is associated with altered lesion topography and susceptibility to experimental autoimmune encephalomyelitis

The regulation of cytokine expression by immune deviation from a pro-inflammatory to anti-inflammatory or "regulatory" milieu is crucial to the prevention of permanent central nervous system (CNS) damage in neuroinflammation. Earlier studies in the murine experimental autoimmune encephalomyelitis (EAE) model pointed to an anti-inflammatory role for the Th2 cytokine, IL-4, which was not confirmed in IL-4Rα-deficient mice (IL-4Rα(-/-)). To examine the pathological consequences of loss of responsiveness to Th2 cytokines, we compared lesion evolution in IL-4Rα(-/-) and wild type (WT) BALB/c mice immunized with PLP180-199 and investigated how altering the magnitude of the antigen-specific autoimmune response in this model affected the pathology. We found that while changing the magnitude of the peripheral antigen-specific response differentially affected the incidence of clinical disease in WT BALB/c relative to IL-4Rα(-/-) mice, the differences in incidence did not correlate to differences in pro-inflammatory cytokine production. Additionally, although only approximately 75% of WT mice developed clinical disease, lesions were observed in 100% of the mice, principally in the cerebellum, mid-brain and cerebral hemispheres, and lesion load increased with increasing pro-inflammatory cytokine production. Despite being resistant to disease induction with increasing pro-inflammatory cytokine production, lesion incidence in IL-4Rα-deficient animals was equal to their WT counterparts. However, lesion severity in IL-4Rα-deficient animals was preferentially reduced in the mid-brain and cerebral hemispheres. From these studies, we conclude that signaling through IL-4Rα has little effect on regulating the peripheral pro-inflammatory cytokine profile in this EAE variant but has distinct effects on the determination of lesion topography.

Chemokine-mediated redirection of T cells constitutes a critical mechanism of glucocorticoid therapy in autoimmune CNS responses

Glucocorticoids (GCs) are the standard therapy for treating multiple sclerosis (MS) patients suffering from an acute relapse. One of the main mechanisms of GC action is held to be the induction of T cell apoptosis leading to reduced lymphocyte infiltration into the CNS, yet our analysis of experimental autoimmune encephalomyelitis (EAE) in three different strains of genetically manipulated mice has revealed that the induction of T cell apoptosis is not essential for the therapeutic efficacy of GCs. Instead, we identified the redirection of T cell migration in response to chemokines as a new therapeutic principle of GC action. GCs inhibited the migration of T cells towards CCL19 while they enhanced their responsiveness towards CXCL12. Importantly, blocking CXCR4 signaling in vivo by applying Plerixafor(®) strongly impaired the capacity of GCs to interfere with EAE, as revealed by an aggravated disease course, more pronounced CNS infiltration and a more dispersed distribution of the infiltrating T cells throughout the parenchyma. Our observation that T cells lacking the GC receptor were refractory to CXCL12 further underscores the importance of this pathway for the treatment of EAE by GCs. Importantly, methylprednisolone pulse therapy strongly increased the capacity of peripheral blood T cells from MS patients of different subtypes to migrate towards CXCL12. This indicates that modulation of T cell migration is an important mechanistic principle responsible for the efficacy of high-dose GC therapy not only of EAE but also of MS.

Skewed B cell differentiation affects lymphoid organogenesis but not T cell-mediated autoimmunity

B cell receptor (BCR) signalling determines B cell differentiation and may potentially alter T cell-mediated immune responses. In this study we used two transgenic strains of BCR-deficient mice expressing Epstein-Barr virus latent membrane protein (LMP)2A in B cells, where either follicular and marginal zone differentiation (D(H)LMP2A mice) or B-1 cell development (V(H)LMP2A mice) were supported, and evaluated the effects of skewed B lymphocyte differentiation on lymphoid organogenesis and T cell responses in vivo. Compared to wild-type animals, both transgenic strains displayed alterations in the composition of lymphoid organs and in the dynamics of distinct immune cell subsets following immunization with the self-antigen PLP₁₈₅₋₂₀₆. However, ex-vivo T cell proliferation to PLP₁₈₅₋₂₀₆ peptide measured in immunized D(H)LMP2A and V(H)LMP2A mice was similar to that detected in immunized control mice. Further, clinical expression of experimental autoimmune encephalitis in both LMP2A strains was identical to that of wild-type mice. In conclusion, mice with skewed B cell differentiation driven by LMP2A expression in BCR-negative B cells do not show changes in the development of a T cell mediated disease model of autoimmunity, suggesting that compensatory mechanisms support the generation of T cell responses.

Experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system that is induced in laboratory animals by the generation of an immune response against myelin epitopes. It has been used as a prototype of Th1- and/or Th17-driven, organ-specific autoimmunity and as a model for the human disease, multiple sclerosis. In this chapter we describe two classic protocols for EAE induction (active immunization and adoptive transfer of Th1- or Th17-polarized cells) in Subheadings 3.1 and 3.2, respectively. Subheading 3.3 describes methods for rating clinical disease in symptomatic animals. Subheading 3.4 includes instructions for the isolation of mononuclear cells from the inflamed spinal cords of mice with EAE. Subheading 3.5 describes a method for performing the enzyme-linked immunospot assay.

IL-9 is important for T-cell activation and differentiation in autoimmune inflammation of the central nervous system

Experimental autoimmune encephalomyelitis (EAE) is generally believed to be an autoimmune disease of the central nervous system (CNS) caused by myelin-specific Th1 and/or Th17 effector cells. The underlying cellular and molecular mechanisms, however, are not fully understood. Using mice deficient in IL-9 (IL-9(-/-) ), we showed that IL-9 plays a critical role in EAE. Specifically, IL-9(-/-) mice developed significantly less severe EAE than their WT counterparts following both immunization with myelin proteolipid protein (PLP)(180-199) peptide in the presence of Complete Freund's Adjuvant (CFA), and adoptive transfer of PLP(180-199) peptide-specific effector T cells from WT littermates. EAE-resistant IL-9(-/-) mice exhibited considerably fewer infiltrating immune cells in the CNS, with lower levels of IL-17 and IFN-γ expression, than their WT littermates. Further studies revealed that null mutation of the IL-9 gene resulted in significantly lower levels of PLP(180-199) peptide-specific IL-17 and IFN-γ production. Moreover, IL-9(-/-) memory/activated T cells exhibited decreased C-C chemokine receptors (CCR)2, CCR5, and CCR6 expression. Interestingly, IL-10 was significantly increased in IL-9(-/-) mice compared with WT littermates. Importantly, we found that IL-9-mediated Th17-cell differentiation triggers complex STAT signaling pathways.

Multiple linked quantitative trait loci within the Tmevd2/Eae3 interval control the severity of experimental allergic encephalomyelitis in DBA/2J mice

Theiler’s murine encephalomyelitis virus-induced demyelination (TMEVD) and experimental allergic encephalomyelitis (EAE) are the principal animal models of multiple sclerosis (MS). Previously we provided evidence that Tmevd2 and Eae3 may represent either a shared susceptibility locus or members of a gene complex controlling susceptibility to CNS inflammatory demyelinating disease. To explore the genetic relationship between Tmevd2 and Eae3, we generated a D2.C-Tmevd2 interval-specific congenic (ISC) line and three overlapping interval-specific recombinant congenic (ISRC) lines in which the Tmevd2 resistant allele from BALB/cByJ was introgressed onto the TMEVD-susceptible DBA/2J background. These mice, all H2^d, were studied for susceptibility to EAE elicited by immunization with PLP_180–199. Compared to DBA/2J mice, D2.C-Tmevd2 mice developed a significantly less severe clinical disease course and EAE pathology in the spinal cord, confirming the existence of Eae3 and its linkage to Tmevd2 in this strain combination. Compare to DBA/2J and D2.C-Tmevd2, all three ISRC lines exhibited clinical disease courses of intermediate severity. Neither differences in ex vivo antigen-specific cytokine nor proliferative responses uniquely cosegregated with differences in disease severity. These results indicate that multiple QTL within the Tmevd2/Eae3 interval influence EAE severity, one of which includes a homology region for a QTL found in MS by admixture mapping.

Direct and consensual murine pupillary reflex metrics: establishing normative values

Pupillometry is a non-invasive technique, based on well-established neurophysiologic principles, that can be utilized to objectively characterize pathophysiologic demyelinating and neurodegenerative changes involving the pupillary reflex pathway. In animal models of human disorders, pupillometry derived reflex metrics could potentially be used to longitudinally monitor disease activity and responses to pharmacotherapies. These investigations would have important implications for translational initiatives focused on the identification and application of novel neuroprotective and restorative treatments for human diseases such as multiple sclerosis. Here, we have established normal reference values for various pupillary reflex metrics across different mouse strains. Ultimately, we anticipate that this new data will help to catalyze unique lines of inquiry using pupillometry methods.

Protection from EAE by IL-4Ralpha(-/-) macrophages depends upon T regulatory cell involvement

The administration of Th2 cytokines or immune deviation to a Th2 phenotypic response has been shown to protect against the autoimmune pathology of experimental autoimmune encephalomyelitis (EAE). To better understand the function of Th2 cytokines in the induction stage of EAE in the absence of an overt Th2 response, we immunized IL-4 receptor alpha-deficient (IL-4Ralpha(-/-)) mice, which are unable to respond to either IL-4 or IL-13. Contrary to expectations, mice lacking IL-4Ralpha had a lower incidence of EAE and a delayed onset compared to WT BALB/c mice; however, this delay did not correlate to an alteration in the Th1/Th17 cytokine balance. Instead, IL-4Ralpha-responsive macrophages were essential promoters of disease as macrophage-specific IL-4Ralpha-deficient (LysM(cre)IL-4Ralpha(-/lox)) mice were protected from EAE. The protection afforded by IL-4Ralpha-deficiency was not due to IL-10-, IFN-gamma-, NO- or IDO-mediated suppression of T-cell responses but was dependent upon the presence of regulatory T cells (Tregs). This investigation highlights the importance of macrophages and Tregs in regulating central nervous system inflammation and demonstrates that macrophages activated in the absence of Th2 cytokines can promote disease suppression by Tregs.

B cells limit epitope spreading and reduce severity of EAE induced with PLP peptide in BALB/c mice

The role of B cells and antibody in experimental autoimmune encephalomyelitis (EAE) appears to differ based on the identity and state (protein vs. encephalitogenic peptide) of the inducing antigen and the strain of mouse utilized. The involvement of B cells in the induction of EAE by peptides of proteolipid protein (PLP) in BALB/c mice was investigated. Wild-type and B cell-deficient (B cell-/-) mice on the BALB/c background were immunized with overlapping PLP peptides, and the disease course was followed. Although incidence and onset of PLP(180-199)-induced EAE was similar in WT and B cell-/- mice, the clinical course was more severe in B cell-/- mice. During acute disease, proliferation and interferon-gamma production by lymphoid cells from both strains were similar and were elicited predominantly in response to the immunizing antigen. However, during chronic disease lymphoid cells isolated from B cell-/- mice proliferated to a greater extent and produced more interferon-gamma in response to the overlapping peptide PLP185-206 and to the smaller internal peptide PLP185-199 than did WT mice. These data suggest that B cells regulate PLP-induced EAE in BALB/c mice through control of epitope spreading.

High cell surface expression of CD4 allows distinction of CD4(+)CD25(+) antigen-specific effector T cells from CD4(+)CD25(+) regulatory T cells in murine experimental autoimmune encephalomyelitis

Analysis of T regulatory cells (Treg) and T effector cells (Teff) in experimental autoimmune encephalomyelitis is complicated by the fact that both cell types express CD4 and CD25. We demonstrate that encephalitogenic T cells, following antigen recognition, up-regulate cell surface expression of CD4. The CD4(high) sub-population contains all of the antigen response as shown by proliferation and cytokine secretion, and only these cells are capable of transferring EAE to naive animals. On the other hand, a FACS separable CD25(+) sub-population of cells displayed consistent levels of CD4 prior to and after antigen stimulation. These cells displayed characteristics of Treg, such as expressing high levels of the Foxp3 gene and the ability to suppress mitogenic T cell responses.

T-bet is essential for the progression of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is mediated by myelin-specific CD4+ T helper 1 (Th1) cells, while recovery from the disease is associated with the presence of Th2 cells. Here we used animals with targeted deletion of the T-bet gene to determine its role in the progression of EAE. T-bet regulates the production of interferon-gamma (IFN-gamma) in CD4+ and natural killer cells, and CD4+ T cells from T-bet-deficient mice were unable to differentiate into a Th1 phenotype. Moreover BALB/c mice deficient in T-bet were resistant to the induction of EAE disease, with minimal inflammatory infiltrates in the central nervous system. These mice were resistant to EAE induction even when PLP(180-199) peptide specific effector T cells from BALB/c wild type were transferred to BALB/c T-bet-deficient mice. This resistance to EAE is may be caused by the production of the anti-inflammatory cytokine interleukin-10 (IL-10) from the spleen cells upon ex vivo stimulation with PLP(180-199) peptide and in vivo presence in the central nervous system. There was no difference in the recall responses in spleen cells from T-bet-deficient and wild type mice; however, less secretion of IFN-gamma was observed from primed splenocytes. The expression of IFN-gamma was less in the central nervous system of T-bet-deficient mice whereas IL-10 was significantly higher in T-bet-deficient as compared to wild type mice. These data indicate that T-bet genes play a critical role in maintaining the encephalitogenic nature of CD4+ T cells in autoimmune responses during EAE disease progression.

Requirement of the Fc receptor common gamma-chain for gamma delta T cell-mediated promotion of murine experimental autoimmune encephalomyelitis

Immunoglobulin Fcgamma receptors (FcgammaR) are comprised of a ligand-binding alpha-chain that sometimes associates with a cell signaling common gamma-chain. These receptors comprise an important family of effector molecules that link humoral and cell-mediated adaptive immunity and regulate innate immunity. Recent animal studies suggest that FcgammaR in general, and FcR alpha-chains in particular, are required for full development of experimental autoimmune encephalomyelitis (EAE). We show here that deletion of the gamma-chain renders mice resistant to EAE, whereas deletion of the alpha-chains of FcgammaRI, FcgammaRIIB and FcgammaRIII has no protective effect. Susceptibility to EAE is fully restored in common gamma-chain-/- mice into which wild-type splenocytes are adoptively transferred, but EAE is not restored in common gamma-chain-/- mice given wild-type splenocytes depleted of gammadelta T cells. These data indicate that although the common gamma-chain is required for full development of EAE in mice, this requirement is likely FcgammaR alpha-chain-independent. Expression of the common gamma-chain by gammadelta T cells, probably in conjunction with the T cell receptor/CD3 complex, is likely the key requirement for full development of EAE.

STAT4- and STAT6-signaling molecules in a murine model of multiple sclerosis

Epidemiological studies suggest that an environmental factor (possibly a virus) acquired early in life may trigger multiple sclerosis (MS). The virus may remain dormant in the central nervous system but then becomes activated in adulthood. All existing models of MS are characterized by inflammation or demyelination that follows days after virus infection or antigen inoculation. While investigating the role of CD4+ T cell responses following Theiler's virus infection in mice deficient in STAT4 or STAT6, we discovered a model in which virus infection was followed by demyelination after a very prolonged incubation period. STAT4-/- mice were resistant to demyelination for 180 days after infection, but developed severe demyelination after this time point. Inflammatory cells and up-regulation of Class I and Class II MHC antigens characterized these lesions. Virus antigen was partially controlled during the early chronic phase of the infection even though viral RNA levels remained high throughout infection. Demyelination correlated with the appearance of virus antigen expression. Bone marrow reconstitution experiments indicated that the mechanism of the late onset demyelination was the result of the STAT4-/- immune system. Thus, virus infection of STAT4-/- mice results in a model that may allow for dissection of the immune events predisposing to late-onset demyelination in MS.