Leonilda M.B. Santos

Vitamin D3 induces IDO+ tolerogenic DCs and enhances Treg, reducing the severity of EAE.

A growing body of evidence supports the hypothesis that vitamin D is an important environmental factor in the etiology of T‐cell‐mediated autoimmune diseases such as multiple sclerosis (MS).

Oral Tolerance: A Biologically Relevant Pathway to Generate Peripheral Tolerance against External and Self Antigens

OT is a relevant biological pathway for generating peripheral tolerance against both self and external antigens with minimal side effects (fig. 3). This route might, therefore, contain promising potential for the treatment of autoimmune and allergic diseases in the human (fig. 3). Thus, oral administration of autoantigens suppresses experimental autoimmune diseases (EAE, EAU, AA, collagen-induced arthritis, NOD diabetes) in a disease- and antigen-specific manner, and oral administration of alloantigens has led to increase of allograft survival. OT might be important in treatment of immune complex diseases and food allergies. OT is mediated by T lymphocytes using at least two nonmutually exclusive mechanisms: suppression and anergy. Suppression can be adoptively transferred by CD8+ T lymphocytes which act by releasing TGF-beta and IL-4 following antigen-specific triggering. Antigen-driven tissue-directed suppression occurs following oral administration of an antigen from the target organ, even if it is not the disease-inducing antigen (bystander suppression). Thus, synthetic peptides can induce OT, and tolerogenic epitopes of antigen may be different from the autoreactive epitope. Due to the promising results in animal models, OT is being tested in clinical trials in multiple sclerosis, rheumatoid arthritis and uveitis [193, 194].

Characterization of immunomodulatory properties and accessory cell function of small intestinal epithelial cells

We have studied the immunomodulatory properties of epithelial cells from the small intestine on T cell immune function in vitro. Proliferation of lymph node cells stimulated either with antigen or with mitogen was inhibited by epithelial cells in a dose-dependent fashion. The epithelial cell-mediated suppression of lymphocyte proliferation was blocked by indomethacin, a cyclooxygenase pathway inhibitor, demonstrating that the suppressive effect of epithelial cells was related to prostaglandin secretion. Furthermore, the action of epithelial cell-secreted prostaglandin on lymphocytes was related to its effect on IL-2 as the suppressive effect of epithelial cells was abrogated by the addition of exogenous IL-2. As previously reported, epithelial cells constitutively express MHC class II and we found them able to present antigen in a class II-restricted fashion when their suppressive effects were blocked by indomethacin. Furthermore, epithelial cells activated by LPS secrete an IL-1 like molecule in a fashion analogous to other antigen-presenting cells. These results demonstrate that epithelial cells can both enhance and suppress in vitro T cell immune responses and further characterize the mechanisms by which intestinal epithelial cells may function in gut-associated immune responses.

Plasmacytoid dendritic cells are increased in cerebrospinal fluid of untreated patients during multiple sclerosis relapse

The plasmacytoid dendritic cells (pDCs) express a high level of Toll-like receptor 9 (TLR-9), which recognizes viral DNA. Activated via TLR-9, pDCs also secrete large amounts of type I interferon which are involved either in stimulation or down regulation of immune response in multiple sclerosis (MS). In the present study, we determinate pDCs levels by flow cytometry in Cerebrospinal Fluid (CSF) and Peripheral Blood from MS patients in relapsing and in remitting phases of the disease, comparing with other non-inflammatory diseases (OND). We provide evidence that MS patients in relapse without any treatment have a significantly (p < 0.01) higher percentage of pDCs in CSF than do patients in remission or those with OND. No change in the percentage of pDCs was observed in the peripheral blood of any of these patients. The increase of pDCs in central nervous system during relapse may be explained either by a virus infection or a down regulatory process.

Disappearance of cerebrospinal fluid oligoclonal bands after natalizumab treatment of multiple sclerosis patients

Intrathecal immunoglobulin synthesis in an oligoclonal pattern is the most common immunologic abnormality detected in MS patients. Various treatments, such as immunomodulators and immunosuppressors, have not been found to modify it. Natalizumab hinders migration of encephalitogenic T-cells into the central nervous system (CNS), reducing inflammatory response. Its impact on CSF oligoclonal bands (OCBs) has not been demonstrated. This report describes its effect in four out of six patients with multiple sclerosis after a mean of 10 infusions: the CSF was negative for OCBs at the second lumbar puncture. In conclusion, natalizumab treatment can reduce CSF OCBs to undetectable levels, although the clinical significance of this observation is not yet known.

Structural brain abnormalities are related to retinal nerve fiber layer thinning and disease duration in neuromyelitis optica spectrum disorders

Background: Although aquaporin-4 (AQP4) is widely expressed in the human brain cortex, lesions are rare in neuromyelitis optica (NMO) spectrum disorders (NMOSD). Recently, however, several studies have demonstrated occult structural brain atrophy in NMO. Objective: This study aims to investigate magnetic resonance imaging (MRI) patterns of gray matter (GM) and white matter (WM) abnormalities in patients with NMOSD and to assess the visual pathway integrity during disease duration correlation of the retinal nerve fiber layer (RNFL) and pericalcarine cortex thickness. Methods: Twenty-one patients with NMOSD and 34 matched healthy controls underwent both high-field MRI (3T) high-resolution T1-weighted and diffusion-tensor MRI. Voxel-based morphometry, cortical analyses (Freesurfer) and diffusion-tensor imaging (DTI) analyses (TBSS-FSL) were used to investigate brain abnormalities. In addition, RNFL measurement by optic-coherence tomography (OCT) was performed. Results: We demonstrate that NMOSD is associated with GM and WM atrophy, encompassing more frequently the motor, sensory and visual pathways, and that the extent of GM atrophy correlates with disease duration. Furthermore, we demonstrate for the first time a correlation between RNFL and pericalcarine cortical thickness, with cortical atrophy evolving over the course of disease. Conclusions: Our findings indicate a role for retrograde and anterograde neurodegeneration in GM atrophy in NMOSD. However, the presence atrophy encompassing almost all lobes suggests that additional pathomechanisms might also be involved.

EFFECTS OF CHLORELLA VULGARIS EXTRACT ON CYTOKINES PRODUCTION IN LISTERIA MONOCYTOGENES INFECTED MICE

ABSTRACT In this study, we have investigated the effects of the unicellular-green-algae Chlorella vulgaris on the production of INF-γ, IL-2, IL-4 and IL-10 in normal and Listeria monocytogenes infected mice. Our results demonstrated that in normal/non infected mice, CVE administration produced no effects in the levels of all cytokines studied. However, Listeria monocytogenes infection enhanced the production of INF-γ and IL-2 at 48 and 72 h after the bacteria inoculation. Interestingly, the treatment with five consecutive doses of 50 mg/Kg/day of Chlorella vulgaris given previously to infection, led to further increases in INF-γ and IL-2 levels at 48 and 72 h in relation to the presence of infection alone. No changes in IL-4 and IL-10 production were observed in Listeria monocytogenes and CVE treated/infected mice. These results are in accordance with the literature, which shows that CVE is a biological response modifier that enhances resistance to Listeria monocytogenes through augmentation of IL-2 and IFN-γ.

Regulatory T Cell Induction during Plasmodium chabaudi Infection Modifies the Clinical Course of Experimental Autoimmune Encephalomyelitis

Background Experimental autoimmune encephalomyelitis (EAE) is used as an animal model for human multiple sclerosis (MS), which is an inflammatory demyelinating autoimmune disease of the central nervous system characterized by activation of Th1 and/or Th17 cells. Human autoimmune diseases can be either exacerbated or suppressed by infectious agents. Recent studies have shown that regulatory T cells play a crucial role in the escape mechanism of Plasmodium spp. both in humans and in experimental models. These cells suppress the Th1 response against the parasite and prevent its elimination. Regulatory T cells have been largely associated with protection or amelioration in several autoimmune diseases, mainly by their capacity to suppress proinflammatory response. Methodology/Principal Findings In this study, we verified that CD4+CD25+ regulatory T cells (T regs) generated during malaria infection (6 days after EAE induction) interfere with the evolution of EAE. We observed a positive correlation between the reduction of EAE clinical symptoms and an increase of parasitemia levels. Suppression of the disease was also accompanied by a decrease in the expression of IL-17 and IFN-γ and increases in the expression of IL-10 and TGF-β1 relative to EAE control mice. The adoptive transfer of CD4+CD25+ cells from P. chabaudi-infected mice reduced the clinical evolution of EAE, confirming the role of these T regs. Conclusions/Significance These data corroborate previous findings showing that infections interfere with the prevalence and evolution of autoimmune diseases by inducing regulatory T cells, which regulate EAE in an apparently non-specific manner.

Nitric Oxide and TNFα Effects in Experimental Autoimmune Encephalomyelitis Demyelination

The involvement of inducible nitric oxide synthase (iNOS), which plays various roles in the progression of autoimmune diseases, was studied in iNOS knockout (KO) mice and wild-type (WT) controls with respect to experimental autoimmune encephalomyelitis (EAE). The iNOS (KO) mice presented a less severe form of the disease than the WT control mice. Although the levels of TNFα decreased in the periphery in both groups, an increase in the number of TNFα-positive cells was detected in the central nervous system during the acute phase of EAE in the WT mice, but not in the KO mice. These findings suggest that NO and TNFα contribute to the pathogenesis of acute EAE.

Expression and activity of nitric oxide synthase isoforms in rat brain during the development of experimental allergic encephalomyelitis.

The activity and expression of nitric oxide synthase (NOS) isoforms and protein nitrotyrosine (NT) residues were investigated in whole encephalic mass (WEM) homogenates during the development of experimental allergic encephalomyelitis (EAE) in Lewis rats. EAE stages (0-III) were daily defined by clinical evaluation, and in the end of each stage, WEMs were removed for analysis of NOS activity, protein NT residues and mRNA for the different NOS isoforms. In the presence of NADPH, WEMs from EAE-III rats showed lower Ca2+-dependent NOS activity than those from control group. These differences disappeared in the presence of exogenous calmodulin, flavin adenine dinucleotide (FAD), tetrahydrobiopterin (BH4) and NADPH. Of all the cofactors, just the omission of FAD caused comparable decrease of Ca2+-dependent NOS activity from both groups. Ca2+-independent NOS activity from EAE-III animals was insensitive to the omission of any of the cofactors, while in control animals this activity was significantly inhibited by the omission of either FAD or BH4. Increased levels of both iNOS mRNA and protein NT expression were observed in animals with EAE, which also showed lower levels of a thermolabile NOS inhibitor in WEM homogenates and sera than controls. In conclusion, during late EAE stages, constitutive Ca2+-dependent NOS activity decreases concomitantly with iNOS upregulation, which could be responsible for the high protein NT levels. The differential dependence of iNOS activity on cofactors and the absence of an endogenous thermolabile NOS inhibitor in animals with EAE could reflect additional control mechanisms of NOS activity in this model of multiple sclerosis.