High cell surface expression of CD4 allows distinction of CD4(+)CD25(+) antigen-specific effector T cells from CD4(+)CD25(+) regulatory T cells in murine experimental autoimmune encephalomyelitis

How oral probiotics affect the severity of an experimental model of progressive multiple sclerosis? Bringing commensal bacteria into the neurodegenerative process

A growing number of studies support that the bidirectional interactions between the gut microbiota, the immune system and the CNS are relevant for the pathophysiology of MS. Several studies have reported alterations in the gut microbiome of MS patients. In addition, a variety of studies in animal models of MS have suggested that specific members of the gut commensal microbiota can exacerbate or ameliorate neuroinflammation. Probiotics represent oral nontoxic immunomodulatory agents that would exert benefits when using in combination with current MS therapy. Here we investigate the effect of Vivomixx on the gut microbiome and central and peripheral immune responses in a murine model of primary progressive MS. Vivomixx administration was associated with increased abundance of many taxa such as Bacteroidetes, Actinobacteria, Tenericutes and TM7. This was accompanied by a clear improvement of the motor disability of Theiler's virus infected mice; in the CNS Vivomixx reduced microgliosis, astrogliosis and leukocyte infiltration. Notably, the presence of Breg cells (CD19⁺CD5⁺CD1d^high) in the CNS was enhanced by Vivomixx, and while spinal cord gene expression of IL-1β and IL-6 was diminished, the probiotic promoted IL-10 gene expression. One of the most significant findings was the increased plasma levels of butyrate and acetate levels in TMEV-mice that received Vivomixx. Peripheral immunological changes were subtle but interestingly, the probiotic restricted IL-17 production by Th17-polarized CD4⁺ T-cells purified from the mesenteric lymph nodes of Theiler's virus infected mice. Our data reinforce the beneficial effects of oral probiotics that would be coadjuvant treatments to current MS therapies.

Manipulation of Gut Microbiota Influences Immune Responses, Axon Preservation, and Motor Disability in a Model of Progressive Multiple Sclerosis

Gut microbiota dysbiosis has been implicated in MS and other immune diseases, although it remains unclear how manipulating the gut microbiota may affect the disease course. Using a well-established model of progressive MS triggered by intracranial infection with Theiler's murine encephalomyelitis virus (TMEV), we sought to determine whether dysbiosis induced by oral antibiotics (ABX) administered on pre-symptomatic and symptomatic phases of the disease influences its course. We also addressed the effects of microbiota recolonization after ABX withdrawn in the presence or absence of probiotics. Central and peripheral immunity, plasma acetate and butyrate levels, axon damage and motor disability were evaluated. The cocktail of ABX prevented motor dysfunction and limited axon damage in mice, which had fewer CD4⁺ and CD8⁺ T cells in the CNS, while gut microbiota recolonization worsened motor function and axonal integrity. The underlying mechanisms of ABX protective effects seem to involve CD4⁺CD39⁺ T cells and CD5⁺CD1d⁺ B cells into the CNS. In addition, microglia adopted a round amoeboid morphology associated to an anti-inflammatory gene profile in the spinal cord of TMEV mice administered ABX. The immune changes in the spleen and mesenteric lymph nodes were modest, yet ABX treatment of mice limited IL-17 production ex vivo. Collectively, our results provide evidence of the functional relevance of gut microbiota manipulation on the neurodegenerative state and disease severity in a model of progressive MS and reinforce the role of gut microbiota as target for MS treatment.

CD44 variant isoforms control experimental autoimmune encephalomyelitis by affecting the lifespan of the pathogenic T cells

CD44 variant (CD44(v)) isoforms play important roles in the development of autoimmune disorders, including colitis and arthritis, but their role in multiple sclerosis (MS) has been explored only to a limited extent. We determined the functional relevance of CD44(v) isoforms in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Genetic ablation of CD44(v7) and CD44(v10) isoforms significantly reduced the clinical EAE burden, as well as the number of inflammatory infiltrates. CD44(v7) and CD44(v10) expression on both memory T and antigen-presenting cells, participated in the development of adoptive transfer EAE. Significantly reduced mRNA expression of Th1 signature genes was detected in the brains of CD44(v10-/-) mice compared with those of CD44(WT) mice. Furthermore, forkhead transcription factor 3 (Foxp3), Bcl-2, and inducible nitric oxide synthase (iNOS) levels were reduced in CD44(v10-/-) brains, whereas active caspase-3 was elevated. Brain-infiltrating CD4(hi)CD44(v10+) T cells preceded EAE onset and paralleled disease severity in wild-type but not in CD44(v7-/-) and CD44(v10-/-) mice. CD44(v7) and CD44(v10) expression contributed to EAE by increasing the longevity of autoreactive CD4(hi)panCD44(hi) T cells. Accordingly, the absence of CD44(v7) and CD44(v10) led to increased apoptosis in the inflammatory infiltrates and reduced Th1 responses, resulting in marked disease reduction. Although absent in noninflamed human brains, we detected CD44(v3), CD44(v7), and CD44(v10) isoforms on glial cells and on perivascular infiltrating cells of MS lesions. We conclude that CD44(v7) and CD44(v10), expressed on autoreactive CD4(hi)panCD44(hi) T cells, are critically involved in the pathogenesis of classic EAE by increasing their life span. Targeting these short CD44(v) isoform regions may reduce inflammatory processes and clinical symptoms in MS.

Laminin-411 is a vascular ligand for MCAM and facilitates TH17 cell entry into the CNS

TH17 cells enter tissues to facilitate pathogenic autoimmune responses, including multiple sclerosis (MS). However, the adhesion molecules involved in the unique migratory capacity of TH17 cells, into both inflamed and uninflamed tissues remain unclear. Herein, we characterize MCAM (CD146) as an adhesion molecule that defines human TH17 cells in the circulation; following in vitro restimulation of human memory T cells, nearly all of the capacity to secrete IL-17 is contained within the population of cells expressing MCAM. Furthermore, we identify the MCAM ligand as laminin 411, an isoform of laminin expressed within the vascular endothelial basement membranes under inflammatory as well as homeotstatic conditions. Purified MCAM-Fc binds to laminin 411 with an affinity of 27 nM, and recognizes vascular basement membranes in mouse and human tissue. MCAM-Fc binding was undetectable in tissue from mice with targeted deletion of laminin 411, indicating that laminin 411 is a major tissue ligand for MCAM. An anti-MCAM monoclonal antibody, selected for inhibition of laminin binding, as well as soluble MCAM-Fc, inhibited T cell adhesion to laminin 411 in vitro. When administered in vivo, the antibody reduced TH17 cell infiltration into the CNS and ameliorated disease in an animal model of MS. Our data suggest that MCAM and laminin 411 interact to facilitate TH17 cell entry into tissues and promote inflammation.

The role of dendritic cells and regulatory T cells in the regulation of allergic asthma

Airways hyperresponsiveness (AHR) is one of the major clinical features of allergic airways disease including allergic asthma, however the immunological mechanisms leading to the induction and regulation of this disorder are not fully understood. In this review we will summarise the evidence of a number of studies, principally in murine models of AHR, suggesting a central role for respiratory tract dendritic cells (RTDC) in the induction of AHR through the generation of lung-homing, allergen-specific effector T cells. We will also summarise the evidence supporting a role for regulatory T cells in the attenuation of AHR and will propose that, as a counterpoint to their capacity to induce AHR, RTDC may also play a role in the attenuation of AHR through the generation of regulatory T cells (T(reg)). A better understanding of the relationship between the physiological and immunological responses to allergen-induced AHR attenuation, and particularly the role of RTDC and T(reg) in this process, will be essential for the development of new treatments and therapies.

Enhancing the ability of experimental autoimmune encephalomyelitis to serve as a more rigorous model of multiple sclerosis through refinement of the experimental design

Advancing the understanding of the mechanisms involved in the pathogenesis of multiple sclerosis (MS) likely will lead to new and better therapeutics. Although important information about the disease process has been obtained from research on pathologic specimens, peripheral blood lymphocytes and MRI studies, the elucidation of detailed mechanisms has progressed largely through investigations using animal models of MS. In addition, animal models serve as an important tool for the testing of putative interventions. The most commonly studied model of MS is experimental autoimmune encephalomyelitis (EAE). This model can be induced in a variety of species and by various means, but there has been concern that the model may not accurately reflect the disease process, and more importantly, it may give rise to erroneous findings when it is used to test possible therapeutics. Several reasons have been given to explain the shortcomings of this model as a useful testing platform, but one idea provides a framework for improving the value of this model, and thus, it deserves careful consideration. In particular, the idea asserts that EAE studies are inadequately designed to enable appropriate evaluation of putative therapeutics. Here we discuss problem areas within EAE study designs and provide suggestions for their improvement. This paper is principally directed at investigators new to the field of EAE, although experienced investigators may find useful suggestions herein.

Focus on FOCIS: interleukin 2 treatment associated autoimmunity

A patient from the University of Pittsburgh is presented who developed autoimmunity during IL-2 based combination therapy. IL-2 was originally described as a "T cell growth factor" capable of expanding previously activated T cells, enhancing the cytotoxicity of antigen-specific cytotoxic T cells and NK cells. High dose Interleukin 2 (HDIL2) is now FDA-approved for therapy of patients with metastatic melanoma and renal cell carcinoma, based on its ability to induce durable responses in 5-10% of patients. The antitumor effect of HDIL2 is incompletely understood, but it appears that this regimen alters the balance of immigrant T effector cells in relation to T suppressor cells. It promotes a less immunosuppressive tumor microenvironment, inducing tumor regression in a subset of patients that is yet to be defined. The antitumor activity of IL-2, as for other agents that promote durable antitumor activity against melanoma such as interferon alpha and anti-CTLA4 antibody, is frequently associated with development of autoimmunity as observed in this patient. We present studies investigating the mechanisms for the therapeutic benefit of HDIL2 in melanoma.