Experimental autoimmune encephalomyelitis in the common marmoset: a translationally relevant model for the cause and course of multiple sclerosis

Animal model of multiple sclerosis: Experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a very complex and heterogeneous disease, with an unknown etiology and which, currently, remains incurable. For this reason, animal models are crucial to investigate this disease, which has increased in prevalence in recent years, affecting 2.8 million people worldwide, and is the leading cause of non-traumatic disability in young adults between the ages of 20-30years. Of all the models developed to replicate MS, experimental autoimmune encephalomyelitis (EAE) best reflects the autoimmune pathogenesis of MS. There are different methods to induce it, which will give rise to different types of EAE, which will vary in clinical presentation and severity. Of the EAE models, the most widespread and used is the one induced in rodents due to its advantages over other species. Likewise, EAE has become a widely used model in the development of therapies for the treatment of MS. Likewise, it is very useful to define the cellular and molecular mechanisms involved in the pathogenesis of MS and to establish therapeutic targets for this disease. For all these reasons, the EAE model plays a key role in improving the understanding of MS.

Marmosets as models of infectious diseases

Animal models of infectious disease often serve a crucial purpose in obtaining licensure of therapeutics and medical countermeasures, particularly in situations where human trials are not feasible, i.e., for those diseases that occur infrequently in the human population. The common marmoset (Callithrix jacchus), a Neotropical new-world (platyrrhines) non-human primate, has gained increasing attention as an animal model for a number of diseases given its small size, availability and evolutionary proximity to humans. This review aims to (i) discuss the pros and cons of the common marmoset as an animal model by providing a brief snapshot of how marmosets are currently utilized in biomedical research, (ii) summarize and evaluate relevant aspects of the marmoset immune system to the study of infectious diseases, (iii) provide a historical backdrop, outlining the significance of infectious diseases and the importance of developing reliable animal models to test novel therapeutics, and (iv) provide a summary of infectious diseases for which a marmoset model exists, followed by an in-depth discussion of the marmoset models of two studied bacterial infectious diseases (tularemia and melioidosis) and one viral infectious disease (viral hepatitis C).

A 4D transcriptomic map for the evolution of multiple sclerosis-like lesions in the marmoset brain

Single-time-point histopathological studies on postmortem multiple sclerosis (MS) tissue fail to capture lesion evolution dynamics, posing challenges for therapy development targeting development and repair of focal inflammatory demyelination. To close this gap, we studied experimental autoimmune encephalitis (EAE) in the common marmoset, the most faithful animal model of these processes. Using MRI-informed RNA profiling, we analyzed ~600,000 single-nucleus and ~55,000 spatial transcriptomes, comparing them against EAE inoculation status, longitudinal radiological signals, and histopathological features. We categorized 5 groups of microenvironments pertinent to neural function, immune and glial responses, tissue destruction and repair, and regulatory network at brain borders. Exploring perilesional microenvironment diversity, we uncovered central roles of EAE-associated astrocytes, oligodendrocyte precursor cells, and ependyma in lesion formation and resolution. We pinpointed imaging and molecular features capturing the pathological trajectory of WM, offering potential for assessing treatment outcomes using marmoset as a platform.

Review of Environmental and Health Factors Impacting Captive Common Marmoset Welfare in the Biomedical Research Setting

As a small-bodied neotropical nonhuman primate species, common marmosets have unique requirements for adequate husbandry and veterinary care to ensure proper maintenance and to promote good animal welfare in a biomedical research setting. Environmental conditions, as well as medical and research-related manipulations, can impact marmoset welfare. Research focus areas, including basic neuroscience, transgenics, and aging, involve additional implications for marmoset welfare. This manuscript provides a comprehensive review of factors that should be considered and mitigated as needed by clinical and research staff working with marmosets in biomedical research facilities to optimize the welfare of captive marmosets.

CCR3 plays a role in murine age-related cognitive changes and T-cell infiltration into the brain

Targeting immune-mediated, age-related, biology has the potential to be a transformative therapeutic strategy. However, the redundant nature of the multiple cytokines that change with aging requires identification of a master downstream regulator to successfully exert therapeutic efficacy. Here, we discovered CCR3 as a prime candidate, and inhibition of CCR3 has pro-cognitive benefits in mice, but these benefits are not driven by an obvious direct action on central nervous system (CNS)-resident cells. Instead, CCR3-expressing T cells in the periphery that are modulated in aging inhibit infiltration of these T cells across the blood-brain barrier and reduce neuroinflammation. The axis of CCR3-expressing T cells influencing crosstalk from periphery to brain provides a therapeutically tractable link. These findings indicate the broad therapeutic potential of CCR3 inhibition in a spectrum of neuroinflammatory diseases of aging.

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

Regulatory T Cells Increase After rh-MOG Stimulation in Non-Relapsing but Decrease in Relapsing MOG Antibody-Associated Disease at Onset in Children

Background

Myelin oligodendrocytes glycoprotein (MOG) antibody-associated disease (MOGAD) represent 25% of pediatric acquired demyelinating syndrome (ADS); 40% of them may relapse, mimicking multiple sclerosis (MS), a recurrent and neurodegenerative ADS, which is MOG-Abs negative.

Aims

To identify MOG antigenic immunological response differences between MOGAD, MS and control patients, and between relapsing versus non-relapsing subgroups of MOGAD.

Methods

Three groups of patients were selected: MOGAD (n=12 among which 5 relapsing (MOGR) and 7 non-relapsing (MOGNR)), MS (n=10) and control patients (n=7). Peripheral blood mononuclear cells (PBMC) collected at the time of the first demyelinating event were cultured for 48 h with recombinant human (rh)-MOG protein (10 μg/ml) for a specific stimulation or without stimulation as a negative control. The T cells immunophenotypes were analyzed by flow cytometry. CD4⁺ T cells, T helper (Th) cells including Th1, Th2, and Th17 were analyzed by intracellular staining of cytokines. Regulatory T cells (T_regs, Foxp3⁺), CD45RA^-Foxp3⁺ T_regs and subpopulation naive T_regs (CD45RA⁺Foxp3^int), effector T_regs (CD45RA^-Foxp3^high) and non-suppressive T_regs (CD45RA^-Foxp3^int) proportions were determined.

Results

The mean onset age of each group, ranging from 9.9 to 13.8, and sex ratio, were similar between MOGR, MOGNR, MS and control patients as analyzed by one-way ANOVA and Chi-square test. When comparing unstimulated to rh-MOG stimulated T cells, a significant increase in the proportion of Th2 and Th17 cells was observed in MOGAD. Increase of Th17 cells was significant in MOGNR (means: 0.63 ± 0.15 vs. 1.36 ± 0.43; Wilcoxon-test p = 0.03) but not in MOGR. CD4⁺ T_regs were significantly increased in MOGNR (means: 3.51 ± 0.7 vs. 4.59 ± 1.33; Wilcoxon-test p = 0.046) while they decreased in MOGR. CD45RA^-Foxp3⁺ T_regs were significantly decreased in MOGR (means: 2.37 ± 0.23 vs. 1.99 ± 0.17; paired t-test p = 0.021), but not in MOGNR. MOGR showed the highest ratio of effector T_regs/non suppressive-T_regs, which was significantly higher than in MOGNR.

Conclusions

Our findings suggest that CD4⁺ Th2 and Th17 cells are involved in the pathophysiology of MOGAD in children. The opposite response of T_regs to rh-MOG in MOGNR, where CD4⁺ T_regs increased, and in MOGR, where CD45RA^-Foxp3⁺ T_regs decreased, suggests a probable loss of tolerance toward MOG autoantigen in MOGR which may explain relapses in this recurrent pediatric autoimmune disease.

Complete Freund's adjuvant-free experimental autoimmune encephalomyelitis in Dark Agouti rats is a valuable tool for multiple sclerosis studies

Experimental autoimmune encephalomyelitis (EAE) is classically induced with complete Freund's adjuvant (CFA). The immune response against CFA has a confounding influence on the translational capacity of EAE as a multiple sclerosis model. Here, we compare clinical, cellular and molecular properties between syngeneic spinal cord homogenate (SCH)- and SCH + CFA-immunized Dark Agouti rats. EAE signs were observed earlier and the cumulative clinical score was higher without CFA. Also, a higher number of immune cells infiltrates in the spinal cords was noticed at the peak of EAE without CFA. High spinal cord abundance of CD8⁺CD11bc⁺MHC class II⁺ cells was detected in SCH-immunized rats. Myelin basic protein -specific response can be elicited in the cells from the lymph nodes draining the site of SCH immunization. This CFA-free EAE is a reliable multiple sclerosis model.

Altered astrocytic function in experimental neuroinflammation and multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that affects about 2.5 million people worldwide. In MS, the patients' immune system starts to attack the myelin sheath, leading to demyelination, neurodegeneration, and, ultimately, loss of vital neurological functions such as walking. There is currently no cure for MS and the available treatments only slow the initial phases of the disease. The later-disease mechanisms are poorly understood and do not directly correlate with the activity of immune system cells, the main target of the available treatments. Instead, evidence suggests that disease progression and disability are better correlated with the maintenance of a persistent low-grade inflammation inside the CNS, driven by local glial cells, like astrocytes and microglia. Depending on the context, astrocytes can (a) exacerbate inflammation or (b) promote immunosuppression and tissue repair. In this review, we will address the present knowledge that exists regarding the role of astrocytes in MS and experimental animal models of the disease.

Deciphering the heterogeneity of myeloid cells during neuroinflammation in the single-cell era

Multiple sclerosis (MS) is a disabling neuroinflammatory disease, which is little understood and lacks a sufficient therapeutic regimen. Myeloid cells have repeatedly shown to play a pivotal role in the disease progression. During homeostasis, only the CNS‐resident microglia and CNS‐associated macrophages are present in the CNS. Neuroinflammation causes peripheral immune cells to infiltrate the CNS contributing to disease progression and neurological sequelae. The differential involvement of the diverse peripheral and resident myeloid cell subsets to the disease pathogenesis and outcome are highly debated and difficult to assess. However, novel technological advances (new mouse models, single‐cell RNA‐Sequencing, and CYTOF) have improved the depth of immune profiling, which allows the characterization of distinct myeloid subsets. This review provides an overview of current knowledge on the phenotypes and roles of these different myeloid subsets in neuroinflammatory disease and their therapeutic relevance.

The Fabp5/calnexin complex is a prerequisite for sensitization of mice to experimental autoimmune encephalomyelitis

We previously showed that calnexin (Canx)-deficient mice are desensitized to experimental autoimmune encephalomyelitis (EAE) induction, a model that is frequently used to study inflammatory demyelinating diseases, due to increased resistance of the blood-brain barrier to immune cell transmigration. We also discovered that Fabp5, an abundant cytoplasmic lipid-binding protein found in brain endothelial cells, makes protein-protein contact with the cytoplasmic C-tail domain of Canx. Remarkably, both Canx-deficient and Fabp5-deficient mice commonly manifest resistance to EAE induction. Here, we evaluated the importance of Fabp5/Canx interactions on EAE pathogenesis and on the patency of a model blood-brain barrier to T-cell transcellular migration. The results demonstrate that formation of a complex comprised of Fabp5 and the C-tail domain of Canx dictates the permeability of the model blood-brain barrier to immune cells and is also a prerequisite for EAE pathogenesis.

Sinomenine Alleviates Murine Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis through Inhibiting NLRP3 Inflammasome

Multiple sclerosis (MS) is known as a chronic neuroinflammatory disorder typified by an immune-mediated demyelination process with ensuing axonal damage and loss. Sinomenine is a natural alkaloid with different therapeutic benefits, including anti-inflammatory and immunosuppressive activities. In this study, possible beneficial effects of sinomenine in an MOG-induced model of MS were determined. Sinomenine was given to MOG_35-55-immunized C57BL/6 mice at doses of 25 or 100 mg/kg/day after onset of MS clinical signs till day 30 post-immunization. Analyzed data showed that sinomenine reduces severity of the clinical signs and to some extent decreases tissue level of pro-inflammatory cytokines IL-1β, IL-6, IL-18, TNFα, IL-17A, and increases level of anti-inflammatory IL-10. In addition, sinomenine successfully attenuated tissue levels of inflammasome NLRP3, ASC, and caspase 1 besides its reduction of intensity of neuroinflammation, demyelination, and axonal damage and loss in lumbar spinal cord specimens. Furthermore, immunoreactivity for MBP decreased and increased for GFAP and Iba1 after MOG-immunization, which was in part reversed upon sinomenine administration. Overall, sinomenine decreases EAE severity, which is attributed to its alleviation of microglial and astrocytic mobilization, demyelination, and axonal damage along with its suppression of neuroinflammation, and its beneficial effect is also associated with its inhibitory effects on inflammasome and pyroptotic pathways; this may be of potential benefit for the primary progressive phenotype of MS.