Functional maturation of proteolipid protein(139-151)-specific Th1 cells in the central nervous system in experimental autoimmune encephalomyelitis

Does coronaviruses induce neurodegenerative diseases? A systematic review on the neurotropism and neuroinvasion of SARS-CoV-2

The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified in 2019 in Wuhan, China. Clinically, respiratory tract symptoms as well as other organs disorders are observed in patients positively diagnosed coronavirus disease 2019 (COVID-19). In addition, neurological symptoms, mainly anosmia, ageusia and headache were observed in many patients. Once in the central nervous system (CNS), the SARS-CoV-2 can reside either in a quiescent latent state, or eventually in actively state leading to severe acute encephalitis, characterized by neuroinflammation and prolonged neuroimmune activation. SRAS-CoV-2 requires angiotensin-converting enzyme 2 (ACE2) as a cell entry receptor. The expression of this receptor in endothelial cells of blood-brain barrier (BBB) shows that SRAS-CoV-2 may have higher neuroinvasive potential compared to known coronaviruses. This review summarizes available information regarding the impact of SRAS-CoV-2 in the brain and tended to identify its potential pathways of neuroinvasion. We offer also an understanding of the long-term impact of latently form of SARS-CoV-2 on the development of neurodegenerative disorders. As a conclusion, the persistent infection of SRAS-CoV-2 in the brain could be involved on human neurodegenerative diseases that evolve a gradual process, perhapes, over several decades.

Establishment of a rat model for canine necrotizing meningoencephalitis (NME)

The pathogenesis of necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME) is still uncertain, although they are considered immune-mediated diseases. The purpose of the present study is to generate a rodent model(s) of these diseases. Rats were injected with rat cerebral or cerebellar homogenate. Rats injected with cerebral homogenate (Cbr) exhibited vacuolar or malacic changes mainly in the cerebral cortex. CD3-positive T cells and Iba-1-positive and CD163-negative microglia infiltrated and activated around the lesions. IgG deposited in the glial fibrillary acid protein (GFAP)-positive glia limitans from the early phase, and CD3-positive T cells attached to GFAP-positive astrocytes. Autoantibodies against GFAP were detected in the sera. These pathological features of Cbr rats were consistent with those of canine NME. In contrast, rats injected with cerebral homogenate (Cbe) exhibited demyelinating lesions with inflammatory reactions in the cerebellum, brainstem, and spinal cord. The presence of demyelination and autoantibodies against myelin proteins in Cbe rats was similar to murine experimental autoimmune encephalitis and differed from NME, NLE, and GME. All the present findings indicate that autoantibodies together with microglia and T cells may play a major role in the pathogenesis of idiopathic canine meningoencephalomyelitis.

New perspectives of tissue remodelling with neural stem and progenitor cell-based therapies

Compelling evidence exists that neural stem cell-based therapies protect the central nervous system (CNS) from chronic inflammatory degeneration, such as that occurring in experimental autoimmune encephalomyelitis and stroke. It was first assumed that stem cells directly replace lost cells but it is now becoming clearer that they might be able to protect the nervous system through mechanisms other than cell replacement. In immune-mediated experimental demyelination and stroke, transplanted neural stem/precursor cells (NPCs) are able to mediate efficient bystander myelin repair and axonal rescue. This is dependent on multiple capacities that transplanted NPCs exhibit within specific microenvironments after transplantation. However, a comprehensive understanding of the mechanisms by which NPCs exert their therapeutic impact is lacking. Here we will review some of the most recent evidence--and discuss some of the likely mechanisms--that support the remarkable capacity of NPCs to cross-talk with endogenous cells and to remodel the injured nervous system when applied as novel therapeutic regimes. We foresee that the exploitation of the innate mechanisms regulating these modalities of cell-to-cell communication has realistic chances of revolutionizing most of the actual understanding of stem cell biology and its application to regenerative medicine and CNS repair.

Gammadelta T cells in EAE: early trafficking events and cytokine requirements

We have previously shown that gammadelta T cells traffic to the CNS during EAE with concurrently increased expression of beta(2)-integrins and production of IFN-gamma and TNF-alpha. To extend these studies, we transferred bioluminescent gammadelta T cells to WT mice and followed their movement through the acute stages of disease. We found that gammadelta T cells rapidly migrated to the site of myelin oligodendrocyte glycoprotein peptide injection and underwent massive expansion. Within 6 days after EAE induction, bioluminescent gammadelta T cells were found in the spinal cord and brain, peaking in number between days 10 and 12 and then rapidly declining by day 15. Reconstitution of gammadelta T cell(-/-) mice with gammadelta T cells derived from beta(2)-integrin-deficient mice (CD11a, -b or -c) demonstrated that gammadelta T-cell trafficking to the CNS during EAE is independent of this family of adhesion molecules. We also examined the role of gammadelta T-cell-produced IFN-gamma and TNF-alpha in EAE and found that production of both cytokines by gammadelta T cells was required for full development of EAE. These results indicate that gammadelta T cells are critical for the development of EAE and suggest a therapeutic target in demyelinating disease.

Surgical excision of CNS-draining lymph nodes reduces relapse severity in chronic-relapsing experimental autoimmune encephalomyelitis

Despite lack of classical lymphatic vessels in the central nervous system (CNS), cells and antigens do reach the CNS-draining lymph nodes. These lymph nodes are specialized to mediate mucosal immune tolerance, but can also generate T- and B-cell immunity. Their role in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) therefore remains elusive. We hypothesized that drainage of CNS antigens to the CNS-draining lymph nodes is vital for the recurrent episodes of CNS inflammation. To test this, we surgically removed the superficial cervical lymph nodes, deep cervical lymph nodes, and the lumbar lymph nodes prior to disease induction in three mouse EAE models, representing acute, chronic, and chronic-relapsing EAE. Excision of the CNS-draining lymph nodes in chronic-relapsing EAE reduced and delayed the relapse burden and EAE pathology within the spinal cord, which suggests initiation of CNS antigen-specific immune responses within the CNS-draining lymph nodes. Indeed, superficial cervical lymph nodes from EAE-affected mice demonstrated proliferation against the immunizing peptide, and the deep cervical lymph nodes, lumbar lymph nodes, and spleen demonstrated additional proliferation against other myelin antigen epitopes. This indicates that intermolecular epitope spreading occurs and that CNS antigen-specific immune responses are differentially generated within the different CNS-draining lymphoid organs. Proliferation of splenocytes from lymphadenectomized and sham-operated mice against the immunizing peptide was similar. These data suggest a role for CNS-draining lymph nodes in the induction of detrimental immune responses in EAE relapses, and conclusively demonstrate that the tolerance-inducing capability of cervical lymph nodes is not involved in EAE.

Brain antigens in functionally distinct antigen-presenting cell populations in cervical lymph nodes in MS and EAE

Drainage of central nervous system (CNS) antigens to the brain-draining cervical lymph nodes (CLN) is likely crucial in the initiation and control of autoimmune responses during multiple sclerosis (MS). We demonstrate neuronal antigens within CLN of MS patients. In monkeys and mice with experimental autoimmune encephalomyelitis (EAE) and in mouse models with non-inflammatory CNS damage, the type and extent of CNS damage was associated with the frequencies of CNS antigens within the cervical lymph nodes. In addition, CNS antigens drained to the spinal-cord-draining lumbar lymph nodes. In human MS CLN, neuronal antigens were present in pro-inflammatory antigen-presenting cells (APC), whereas the majority of myelin-containing cells were anti-inflammatory. This may reflect a different origin of the cells or different drainage mechanisms. Indeed, neuronal antigen-containing cells in human CLN did not express the lymph node homing receptor CCR7, whereas myelin antigen-containing cells in situ and in vitro did. Nevertheless, CLN from EAE-affected CCR7-deficient mice contained equal amounts of myelin and neuronal antigens as wild-type mice. We conclude that the type and frequencies of CNS antigens within the CLN are determined by the type and extent of CNS damage. Furthermore, the presence of myelin and neuronal antigens in functionally distinct APC populations within MS CLN suggests that differential immune responses can be evoked.

Long-term human coronavirus-myelin cross-reactive T-cell clones derived from multiple sclerosis patients

Autoimmune reactions associated with MS involve genetic and environmental factors. Because murine coronaviruses induce an MS-like disease, the human coronaviruses (HCoV) are attractive candidates as environmental factors involved in a demyelinating pathology. We previously reported the isolation of HCoV-229E/myelin basic protein (MBP) cross-reactive T-cell lines (TCL) in MS patients. To investigate antigenic cross-reactivity at the molecular level, 155 long-term T-cell clones (TCC) were derived from 32 MS patients by in vitro selection with MBP, proteolipid protein (PLP) or HCoV (strains 229E and OC43). Overall, 114 TCC were virus-specific, 31 were specific for myelin Ag and 10 other were HCoV/myelin cross-reactive. Twenty-eight virus-specific TCC and 7 myelin-specific TCC were obtained from six healthy donors. RACE RT-PCR amplification of the Vbeta chains of five of ten the cross-reactive TCC confirmed clonality and sequencing identified the CDR3 region associated with cross-reactivity. Our findings have promising implications in the investigation of the role of molecular mimicry between coronaviruses and myelin in MS as a mechanism related to disease initiation or relapses.

Neural precursors attenuate autoimmune encephalomyelitis by peripheral immunosuppression

OBJECTIVE

Intracerebroventricular or intravenous (IV) injection of neural precursor cells (NPCs) attenuates experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis. Although stem cell therapy was introduced initially for cell replacement, we examine here whether NPCs possess immunomodulatory effects.

METHODS

We examined the effects of systemic administration of NPCs on central nervous system (CNS) inflammation in EAE and the interactions between NPCs and T cells in vitro and in vivo.

RESULTS

IV NPC therapy decreased significantly CNS inflammation and tissue injury and attenuated the clinical severity of EAE. IV-injected NPCs could not be found in the CNS but were detected in lymphoid organs. Coculture experiments showed that NPCs inhibited the activation and proliferation of lymph node-derived T cells in response to CNS-derived antigens and to nonspecific polyclonal stimuli. The relevance of NPC/lymph node cell interactions in vivo was further demonstrated when lymph node cells obtained from IV NPC-treated mice exhibited poor encephalitogenicity on transfer to naive mice and caused a markedly milder EAE compared with those obtained from nontreated mice.

INTERPRETATION

IV administration of neural precursors inhibits EAE by a peripheral immunosuppressive effect. Our findings suggest a profound bystander inhibitory effect of NPCs on T-cell activation and proliferation in the lymph nodes, leading to amelioration of EAE.

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitor Atorvastatin mediated effects depend on the activation status of target cells in PLP-EAE

The effect of Atorvastatin on transcriptional activity in murine experimental autoimmune encephalomyelitis (EAE) induced by PLP peptide 139-151 was analyzed by DNA microarray technique in lymph nodes and spinal cord at onset (10 days), height (20 days) and first remission (30 days) of disease. Fourteen genes were selectively influenced by Atorvastatin in EAE mice. They are mainly related to immune cell functions and regulation of cell-to-cell interaction. Interestingly, seven genes were also differentially regulated in CFA-injected control mice. But qualitative and quantitative differences to EAE mice argue for a dependency of statin effects on the activation status of target cells. Differential regulation of the newly detected candidate genes of statin effects COX-1 and HSP-105 and the previously known statin-responsive genes ICAM-1 and CD86 was confirmed by Western blot and immunohistochemistry. Flow cytometric analysis of lymph node cells revealed that the effect of Atorvastatin treatment in non-immunized healthy animals resembled the effect of immunization with PLP peptide regarding changes of T helper cells, activated B cells and macrophages. In EAE mice, these effects were partially reversed by Atorvastatin treatment. Monitoring of expression of the newly identified candidate genes and patterns of lymphocyte subpopulations might predict the responsiveness of multiple sclerosis patients to statin treatment.