Synergistic Targeting of Innate Receptors TLR7 and NOD2 for Therapeutic Intervention in Multiple Sclerosis.

Regulation of neuroinflammation is critical for maintaining central nervous system (CNS) homeostasis and holds therapeutic promise in autoimmune diseases such as multiple sclerosis (MS). Previous studies have highlighted the significance of selective innate signaling in triggering anti-inflammatory mechanisms, which play a protective role in an MS-like disease, experimental autoimmune encephalomyelitis (EAE). However, the individual intra-CNS administration of specific innate receptor ligands or agonists, such as for toll-like receptor 7 (TLR7) and nucleotide-binding oligomerization-domain-containing protein 2 (NOD2), failed to elicit the desired anti-inflammatory response in EAE. In this study, we investigated the potential synergistic effect of targeting both TLR7 and NOD2 simultaneously to prevent EAE progression. Our findings demonstrate that simultaneous intrathecal administration of NOD2- and TLR7-agonists led to synergistic induction of Type I IFN (IFN I) and effectively suppressed EAE in an IFN I-dependent manner. Suppression of EAE was correlated with a significant decrease in the infiltration of monocytes, granulocytes, and natural killer cells, reduced demyelination, and downregulation of IL-1ß, CCL2, and IFNγ gene expression in the spinal cord. These results underscore the therapeutic promise of concurrently targeting the TLR7 and NOD2 pathways in alleviating neuroinflammation associated with MS, paving the way for novel and more efficacious treatment strategies.

Targeting Signaling Pathway Downstream of RIG-I/MAVS in the CNS Stimulates Production of Endogenous Type I IFN and Suppresses EAE.

Type I interferons (IFN), including IFNß, play a protective role in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Type I IFNs are induced by the stimulation of innate signaling, including via cytoplasmic RIG-I-like receptors. In the present study, we investigated the potential effect of a chimeric protein containing the key domain of RIG-I signaling in the production of CNS endogenous IFNß and asked whether this would exert a therapeutic effect against EAE. We intrathecally administered an adeno-associated virus vector (AAV) encoding a fusion protein comprising RIG-I 2CARD domains (C) and the first 200 amino acids of mitochondrial antiviral-signaling protein (MAVS) (M) (AAV-CM). In vivo imaging in IFNß/luciferase reporter mice revealed that a single intrathecal injection of AAV-CM resulted in dose-dependent and sustained IFNß expression within the CNS. IFNß expression was significantly increased for 7 days. Immunofluorescent staining in IFNß-YFP reporter mice revealed extraparenchymal CD45+ cells, choroid plexus, and astrocytes as sources of IFNß. Moreover, intrathecal administration of AAV-CM at the onset of EAE induced the suppression of EAE, which was IFN-I-dependent. These findings suggest that accessing the signaling pathway downstream of RIG-I represents a promising therapeutic strategy for inflammatory CNS diseases, such as MS.

An Experimental Model of Neuromyelitis Optica Spectrum Disorder-Optic Neuritis: Insights Into Disease Mechanisms.

Background: Optic neuritis (ON) is a common inflammatory optic neuropathy, which often occurs in neuromyelitis optica spectrum disease (NMOSD). An experimental model of NMOSD-ON may provide insight into disease mechanisms. Objective: To examine the pathogenicity of autoantibodies targeting the astrocyte water channel aquaporin-4 [aquaporin-4 (AQP4)-immunoglobulin G (AQP4-IgG)] in the optic nerve. Materials and Methods: Purified IgG from an AQP4-IgG-positive NMOSD-ON patient was together with human complement (C) given to wild-type (WT) and type I interferon (IFN) receptor-deficient mice (IFNAR1-KO) as two consecutive intrathecal injections into cerebrospinal fluid via cisterna magna. The optic nerves were isolated, embedded in paraffin, cut for histological examination, and scored semi-quantitatively in a blinded fashion. In addition, optic nerves were processed to determine selected gene expression by quantitative real-time PCR. Results: Intrathecal injection of AQP4-IgG+C induced astrocyte pathology in the optic nerve with loss of staining for AQP4 and glial fibrillary acidic protein (GFAP), deposition of C, and demyelination, as well as upregulation of gene expression for interferon regulatory factor-7 (IRF7) and CXCL10. Such pathology was not seen in IFNAR1-KO mice nor in control mice. Conclusion: We describe induction of ON in an animal model for NMOSD and show a requirement for type I IFN signaling in the disease process.

Protective roles for myeloid cells in neuroinflammation.

Myeloid cells represent the major cellular component of innate immune responses. Myeloid cells include monocytes and macrophages, granulocytes (neutrophils, basophils and eosinophils) and dendritic cells (DC). The role of myeloid cells has been broadly described both in physiological and in pathological conditions. All tissues or organs are equipped with resident myeloid cells, such as parenchymal microglia in the brain, which contribute to maintaining homeostasis. Moreover, in case of infection or tissue damage, other myeloid cells such as monocytes or granulocytes (especially neutrophils) can be recruited from the circulation, at first to promote inflammation and later to participate in repair and regeneration. This review aims to address the regulatory roles of myeloid cells in inflammatory diseases of the central nervous system (CNS), with a particular focus on recent work showing induction of suppressive function via stimulation of innate signalling in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE).