Single-step purification and refolding of recombinant mouse and human myelin oligodendrocyte glycoprotein and induction of EAE in mice

The aging mouse CNS is protected by an autophagy-dependent microglia population promoted by IL-34

Microglia harness an unutilized health-promoting potential in age-related neurodegenerative and neuroinflammatory diseases, conditions like progressive multiple sclerosis (MS). Our research unveils an microglia population emerging in the cortical brain regions of aging mice, marked by ERK1/2, Akt, and AMPK phosphorylation patterns and a transcriptome indicative of activated autophagy - a process critical for cellular adaptability. By deleting the core autophagy gene Ulk1 in microglia, we reduce this population in the central nervous system of aged mice. Notably, this population is found dependent on IL-34, rather than CSF1, although both are ligands for CSF1R. When aging mice are exposed to autoimmune neuroinflammation, the loss of autophagy-dependent microglia leads to neural and glial cell death and increased mortality. Conversely, microglial expansion mediated by IL-34 exhibits a protective effect. These findings shed light on an autophagy-dependent neuroprotective microglia population as a potential target for treating age-related neuroinflammatory conditions, including progressive MS.

Myeloid cell-specific topoisomerase 1 inhibition using DNA origami mitigates neuroinflammation

Targeting myeloid cells, especially microglia, for the treatment of neuroinflammatory diseases such as multiple sclerosis (MS), is underappreciated. Our in silico drug screening reveals topoisomerase 1 (TOP1) inhibitors as promising drug candidates for microglial modulation. We show that TOP1 is highly expressed in neuroinflammatory conditions, and TOP1 inhibition using camptothecin (CPT) and its FDA-approved analog topotecan (TPT) reduces inflammatory responses in microglia/macrophages and ameliorates neuroinflammation in vivo. Transcriptomic analyses of sorted microglia from LPS-challenged mice reveal an altered transcriptional phenotype following TPT treatment. To target myeloid cells, we design a nanosystem using β-glucan-coated DNA origami (MyloGami) loaded with TPT (TopoGami). MyloGami shows enhanced specificity to myeloid cells while preventing the degradation of the DNA origami scaffold. Myeloid-specific TOP1 inhibition using TopoGami significantly suppresses the inflammatory response in microglia and mitigates MS-like disease progression. Our findings suggest that TOP1 inhibition in myeloid cells represents a therapeutic strategy for neuroinflammatory diseases and that the myeloid-specific nanosystems we designed may also benefit the treatment of other diseases with dysfunctional myeloid cells.

Microglial autophagy-associated phagocytosis is essential for recovery from neuroinflammation

Multiple sclerosis (MS) is a leading cause of incurable progressive disability in young adults caused by inflammation and neurodegeneration in the central nervous system (CNS). The capacity of microglia to clear tissue debris is essential for maintaining and restoring CNS homeostasis. This capacity diminishes with age, and age strongly associates with MS disease progression, although the underlying mechanisms are still largely elusive. Here, we demonstrate that the recovery from CNS inflammation in a murine model of MS is dependent on the ability of microglia to clear tissue debris. Microglia-specific deletion of the autophagy regulator Atg7, but not the canonical macroautophagy protein Ulk1, led to increased intracellular accumulation of phagocytosed myelin and progressive MS-like disease. This impairment correlated with a microglial phenotype previously associated with neurodegenerative pathologies. Moreover, Atg7-deficient microglia showed notable transcriptional and functional similarities to microglia from aged wild-type mice that were also unable to clear myelin and recover from disease. In contrast, induction of autophagy in aged mice using the disaccharide trehalose found in plants and fungi led to functional myelin clearance and disease remission. Our results demonstrate that a noncanonical form of autophagy in microglia is responsible for myelin degradation and clearance leading to recovery from MS-like disease and that boosting this process has a therapeutic potential for age-related neuroinflammatory conditions.

Skeletal muscle interleukin 15 promotes CD8(+) T-cell function and autoimmune myositis

Background

Interleukin 15 (IL-15) is thought to be abundant in the skeletal muscle under steady state conditions based on RNA expression; however, the IL-15 RNA level may not reflect the protein level due to post-transcriptional regulation. Although exogenous protein treatment and overexpression studies indicated IL-15 functions in the skeletal muscle, how the skeletal muscle cell uses IL-15 remains unclear. In myositis patients, IL-15 protein is up-regulated in the skeletal muscle. Given the supporting role of IL-15 in CD8⁺ T-cell survival and activation and the pathogenic role of cytotoxic CD8⁺ T cells in polymyositis and inclusion-body myositis, we hypothesize that IL-15 produced by the inflamed skeletal muscle promotes myositis via CD8⁺ T cells.

Methods

Expression of IL-15 and IL-15 receptors at the protein level by skeletal muscle cells were examined under steady state and cytokine stimulation conditions. The functions of IL-15 in the skeletal muscle were investigated using Il15 knockout (Il15^−/−) mice. The immune regulatory role of skeletal muscle IL-15 was determined by co-culturing cytokine-stimulated muscle cells and memory-like CD8⁺ T cells in vitro and by inducing autoimmune myositis in skeletal-muscle-specific Il15^−/− mice.

Results

We found that the IL-15 protein was not expressed by skeletal muscle cells under steady state condition but induced by tumor necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) stimulation and expressed as IL-15/IL-15 receptor alpha (IL-15Rα) complex. Skeletal muscle cells expressed a scanty amount of IL-15 receptor beta (IL-15Rβ) under either conditions and only responded to a high concentration of IL-15 hyperagonist, but not IL-15. Consistently, deficiency of endogenous IL-15 affected neither skeletal muscle growth nor its responses to TNF-α and IFN-γ. On the other hand, the cytokine-stimulated skeletal muscle cells presented antigen and provided IL-15 to promote the effector function of memory-like CD8⁺ T cells. Genetic ablation of Il15 in skeletal muscle cells greatly ameliorated autoimmune myositis in mice.

Conclusions

These findings together indicate that skeletal muscle IL-15 directly regulates immune effector cells but not muscle cells and thus presents a potential therapeutic target for myositis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13395-015-0058-2) contains supplementary material, which is available to authorized users.

Critical role of activation induced cytidine deaminase in experimental autoimmune encephalomyelitis

Multiple Sclerosis (MS) is a neurodegenerative autoimmune disorder caused by chronic inflammation and demyelination within the central nervous system (CNS). Clinical studies in MS patients have demonstrated efficacy with B cell targeted therapies such as anti-CD20. However, the exact role that B cells play in the disease process is unclear. Activation Induced cytidine deaminase (AID) is an essential enzyme for the processes of antibody affinity maturation and isotype switching. To evaluate the impact of affinity maturation and isotype switching, we have interrogated the effect of AID-deficiency in an animal model of MS. Here, we show that the severity of experimental autoimmune encephalomyelitis (EAE) induced by the extracellular domain of human myelin oligodendrocyte glycoprotein (MOG1-125) is significantly reduced in Aicda deficient mice, which, unlike wild-type mice, lack serum IgG to myelin associated antigens. MOG specific T cell responses are comparable between wild-type and Aicda knockout mice suggesting an active role for antigen experienced B cells. Thus affinity maturation and/or class switching are critical processes in the pathogenesis of EAE.

Relationship between NMO-antibody and anti-MOG antibody in optic neuritis

BACKGROUND

Damage to astrocytes by anti-aquaporin-4 antibody (AQP4-Ab), also known as NMO antibody, has been implicated as the cause of neuromyelitis optica. Myelin oligodendrocyte glycoprotein (MOG) is well known as the causative protein of multiple sclerosis (MS). MOG antigen is currently considered as a cause of optic neuritis (ON) associated with MS because immunization with MOG antigen derived from oligodendrocytes induces murine ON with myelitis. We investigated the relationship between NMO antibody (NMO-Ab) and anti-MOG antibody (MOG-Ab) and potential in patients with ON for recovery of vision.

METHODS

Thirty-three eyes of 23 patients with ON were studied. At presentation, serum NMO-Ab was measured by immunofluorescence using HEK 293 cells transfected with AQP4-GFP, and anti-MOG1-125 antibody was measured by enzyme-linked immunosorbent assay. MOG-Ab seropositivity was defined by comparing with MOG-Ab level obtained from 8 healthy normal subjects.

RESULTS

Eleven (47%) of 23 ON patients were NMO-Ab seropositive, while 8 (34%) of the 23 patients were MOG-Ab seropositive. Six (26%) of 23 patients were seropositive for both NMO-Ab and MOG-Ab. Ten (43%) of 23 patients were seronegative for both antibodies. Three (50%) of 6 eyes of patients seropositive for both antibodies did not respond to corticosteroid pulse therapy and plasmapheresis, and visual acuity remained unchanged. In the NMO-Ab/MOG-Ab group, visual acuity improved significantly (P < 0.0001). In the other 3 groups (NMO-Ab/MOG-Ab, NMO-Ab/MOG-Ab, and NMO-Ab/MOG-Ab), visual acuity did not change significantly (P = 0.53, 0.42, and 0.45, respectively).

CONCLUSION

NMO-Ab and MOG-Ab could be potential biomarkers to determine visual prognosis in patients with ON.

Autoantigen conformation influences both B- and T-cell responses and encephalitogenicity

It has become increasingly clear that only antibodies recognizing conformation-dependent epitopes of myelin oligodendrocyte glycoprotein (MOG) have a demyelinating potential in the animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Nevertheless, for the induction of EAE, most studies to date have used MOG peptides or bacterially expressed MOG, neither of which contain the tertiary structure of the native antigen. Non-refolded recombinant human MOG does not induce EAE in DA rats. Therefore, we refolded this protein in order to assess the influence of MOG conformation on its pathogenicity in DA rats. DA rats immunized with refolded human MOG developed severe acute EAE. As expected, rats immunized with the refolded protein had a higher amount of conformational MOG antibodies present in serum. But in addition, a striking effect of MOG refolding on the generation of T-cell responses was found. Indeed, T-cell responses against the encephalitogenic MOG 91-108 epitope were greatly enhanced after refolding. Therefore, we conclude that refolding of MOG increases its pathogenicity both by generating conformation-dependent MOG antibodies and by enhancing its processing or/and presentation on MHC molecules. These data are important in regard to investigations of the pathogenic potential of many (auto)antigens.

Active immunization using a single dose immunotherapeutic abates established EAE via IL-10 and regulatory T cells

Stimulation of Ag-specific inducible Treg can enhance resolution of autoimmune disease. Conventional methods to induce Treg often require induction of autoimmune disease or subjection to infection. Reovirus adhesin, protein σ1 (pσ1), can successfully facilitate tolerance when fused to a tolerogen. We tested whether myelin oligodendrocyte glycoprotein (MOG) fused to pσ1 (MOG-pσ1) can stimulate Ag-specific Treg. We show that C57BL/6 mice treated nasally with MOG-pσ1 fail to induce MOG-specific Abs and delayed-type hypersensitivity (DTH) responses and resist EAE. Such resistance was attributed to stimulation of Foxp3(+) Treg, as well as Th2 cells. MOG-pσ1's protective capacity was abrogated in IL-10(-/-) mice, but restored when adoptively transferred with MOG-pσ1-induced Treg. As a therapeutic, MOG-pσ1 diminished EAE within 24 h of nasal application, unlike recombinant MOG (rMOG), pσ1, or pσ1+rMOG, implicating the importance of Ag specificity by pσ1-based therapeutics. MOG-pσ1-treated mice showed elevated IL-4, IL-10, and IL-28 production by CD4(+) T cells, unlike rMOG treated or control mice that produced elevated IFN-γ or IL-17, respectively. These data show the feasibility of using pσ1 as a tolerogen platform for Ag-specific tolerance induction and highlight its potential use as an immunotherapeutic for autoimmunity.

Antibodies to myelin oligodendrocyte glycoprotein in HIV-1 associated neurocognitive disorder: a cross-sectional cohort study

Background

Neuroinflammation and demyelination have been suggested as mechanisms causing HIV-1 associated neurocognitive disorder (HAND). This cross-sectional cohort study explores the potential role of antibodies to myelin oligodendrocyte glycoprotein (MOG), a putative autoantigen in multiple sclerosis, in the pathogenesis of HAND.

Methods

IgG antibodies against MOG were measured by ELISA in sera and cerebrospinal fluid (CSF) of 65 HIV-positive patients with HAND (n = 14), cerebral opportunistic infections (HIVOI, n = 25), primary HIV infection (HIVM, n = 5) and asymptomatic patients (HIVasy, n = 21). As control group HIV-negative patients with bacterial or viral CNS infections (OIND, n = 18) and other neurological diseases (OND, n = 22) were included. In a subset of HAND patients MOG antibodies were determined before and during antiviral therapy.

Results

In serum, significantly higher MOG antibody titers were observed in HAND compared to OND patients. In CSF, significantly higher antibody titers were observed in HAND and HIVOI patients compared to HIVasy and OND patients and in OIND compared to OND patients. CSF anti-MOG antibodies showed a high sensitivity and specificity (85.7% and 76.2%) for discriminating patients with active HAND from asymptomatic HIV patients. MOG immunopositive HAND patients performed significantly worse on the HIV dementia scale and showed higher viral load in CSF. In longitudinally studied HAND patients, sustained antibody response was noted despite successful clearance of viral RNA.

Conclusions

Persistence of MOG antibodies despite viral clearance in a high percentage of HAND patients suggests ongoing neuroinflammation, possibly preventing recovery from HAND.

Demyelination caused by the copper chelator cuprizone halts T cell mediated autoimmune neuroinflammation

Myelin reactive T cells are central in the development of the autoimmune response leading to CNS destruction in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis (EAE). Investigations on the mechanisms underlying the activation and expansion of myelin reactive T have stressed the importance of non-autoimmune conditions impinging the autoimmune repertoire potentially involved in the disease. Here, we show that CNS injury caused by the toxic cuprizone results in the generation of immunoreactivity towards several myelin components. Paradoxically, exposure to CNS injury does not increase the susceptibility to develop EAE, but render mice protected to the pathogenic autoimmune response against myelin antigens.

Intrathecal anti-alphaB-crystallin IgG antibody responses: potential inflammatory markers in Guillain-Barré syndrome

OBJECTIVE

alphaB-crystallin (alphaBC), a small stress protein with cytoprotective and anti-apoptotic functions, is a potent antigen in autoimmune demyelinating diseases. To address the role of alphaBC in Guillain-Barré syndrome (GBS) we analyzed humoral responses against alphaBC in relation to clinical, electrophysiological and CSF features in GBS.

METHODS

Anti-alphaBC-IgG antibodies were measured in serum and cerebrospinal fluid (CSF) of patients with GBS (n = 41), infectious inflammatory neurological diseases (n = 21), multiple sclerosis (n = 42), and other, non-inflammatory neurological disorders (n = 40) by ELISA using human recombinant alphaBC. Expression of alphaBC was immunohistochemically analyzed in postmortem peripheral nerve tissue of GBS and controls without neuropathy.

RESULTS

Serum alphaBC-IgG antibody levels did not differ between disease groups, whereas alphaBC-IgG antibodies in CSF were increased in GBS and infectious inflammatory neurological diseases. Calculation of an antigen specific alphaBC-IgG index (alphaBC-Ig-G(CSF) x total IgG(CSF))/(alphaBC-IgG(Serum) x total IgG(Serum)) revealed significantly elevated values in patients with GBS compared to other disease groups (p < 0.001). alphaBC-IgG indices exceeding a cut off value > 0.8 had an 85 % specificity and a 76 % sensitivity for GBS. alphaBC was overexpressed in dorsal root ganglia and spinal roots of autopsy cases with GBS.

CONCLUSIONS

We demonstrate increased alphaBC-IgG indices in a high proportion of our GBS patients, which reflect enhanced antigen-specific intrathecal antibody responses against abnormally expressed alphaBC in inflamed peripheral nerve tissue. Elevated alphaBC-IgG indices might therefore serve as markers of PNS inflammation and supplement currently used laboratory tests in the diagnosis of GBS.

Protective DNA vaccination against myelin oligodendrocyte glycoprotein is overcome by C3d in experimental autoimmune encephalomyelitis

Complement receptor 2 (CR2) and its physiological ligand, C3d, known for its molecular adjuvant property on the immune response, exhibit opposite effects with regard to autoimmunity. Although CR2 has been implicated in maintaining self-tolerance, recent studies reported a role for C3d signaling to CR2 in tolerance breakdown to self-antigens and the initiation of inflammatory autoimmune pathologies. In the present study, we have investigated the effect of C3d in a model of tolerogenic DNA vaccination encoding the myelin oligodendrocyte glycoprotein (MOG-DNA) which protected mice from the induction of an experimental autoimmune encephalomyelitis (EAE). We show that fusing two or three copies of C3d to MOG overcomes the protective effect of DNA vaccination. Multimeric C3d was able to revert the unresponsiveness state of specific T cells induced by MOG-DNA, independently of a modification in the Th1/Th2 cytokine pattern. Interestingly, the adjuvant effect of C3d was not sufficient to boost the anti-MOG antibody response after DNA vaccination. These findings suggest that C3d might be involved in self-tolerance breakdown and could contribute to the pathogenesis of central nervous system autoimmune disorders.

C3d binding to the myelin oligodendrocyte glycoprotein results in an exacerbated experimental autoimmune encephalomyelitis

The complement system is known to contribute to demyelination in multiple sclerosis and experimental autoimmune encephalomyelitis. However, there are few data concerning the natural adjuvant effect of C3d on the humoral response when it binds to myelin Ags. This study addresses the effect of C3d binding to the myelin oligodendrocyte glycoprotein (MOG) in the induction of experimental autoimmune encephalomyelitis in C57BL/6J mice. Immunization with human MOG coupled to C3d was found to accelerate the appearance of clinical signs of the disease and to enhance its severity compared with MOG-immunized mice. This finding was correlated with an increased infiltration of leukocytes into the central nervous system accompanied by increased complement activation and associated with areas of demyelination and axonal loss. Furthermore, B cell participation in the pathogenesis of the disease was determined by their increased capacity to act as APCs and to form germinal centers. Consistent with this, the production of MOG-specific Abs was found to be enhanced following MOG/C3d immunization. These results suggest that binding of C3d to self-Ags could increase the severity of an autoimmune disease by enhancing the adaptive autoimmune response.

Myelin oligodendrocyte glycoprotein antibodies in pathologically proven multiple sclerosis: frequency, stability and clinicopathologic correlations

Controversy exists regarding the pathogenic or predictive role of anti-myelin oligodendrocyte glycoprotein (MOG) antibodies in patients with multiple sclerosis (MS). Four immunopathological patterns (IP) have been recognized in early active MS lesions, suggesting heterogeneous pathogenic mechanisms. Whether MOG antibodies contribute to this pathological heterogeneity and potentially serve as biomarkers to identify specific pathological patterns is unknown. Here we report the frequencies of antibodies to human recombinant MOG (identified by Western blot and enzyme-linked immunoabsorbent assay (ELISA)) in patients with pathologically proven demyelinating disease, and investigate whether antibody status is associated with clinical course, HLA-DR2-genotype, IP or treatment response to plasmapheresis. The biopsy cohort consisted of 72 patients: 12 pattern I, 43 pattern II and 17 pattern III. No association was found between MOG antibody status and conversion to clinically definite MS, DR-2 status, IP or response to plasmapheresis. There was poor agreement between Western blot and ELISA (kappa = 0.07 for MOG IgM). Fluctuations in antibody seropositivity were seen for 3/4 patients tested serially by Western blot. This study does not support a pathologic pattern-specific role for MOG-antibodies. Variable MOG-antibody status on serial measurements, coupled with the lack of Western blot and ELISA correlations, raises concern regarding the use of MOG-antibody as an MS biomarker and underscores the need for methodological consensus.