Sakhina Begum-Haque

IL-9 as a mediator of Th17-driven inflammatory disease

We report that like other T cells cultured in the presence of transforming growth factor (TGF) β, Th17 cells also produce interleukin (IL) 9. Th17 cells generated in vitro with IL-6 and TGF-β as well as purified ex vivo Th17 cells both produced IL-9. To determine if IL-9 has functional consequences in Th17-mediated inflammatory disease, we evaluated the role of IL-9 in the development and progression of experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. The data show that IL-9 neutralization and IL-9 receptor deficiency attenuates disease, and this correlates with decreases in Th17 cells and IL-6–producing macrophages in the central nervous system, as well as mast cell numbers in the regional lymph nodes. Collectively, these data implicate IL-9 as a Th17-derived cytokine that can contribute to inflammatory disease.

A polysaccharide from the human commensal Bacteroides fragilis protects against CNS demyelinating disease

The intestinal microbiome may have a critical roll in susceptibility or resistance to immune-mediated diseases. Alterations of the gut microflora after oral antibiotic treatment can regulate encephalomyelitis (EAE), an animal model for human multiple sclerosis (MS). We now show that a zwitterionic capsular polysaccharide A (PSA) of Bacteroides fragilis can protect against central nervous system demyelinating disease. Oral administration with purified PSA protected mice against EAE prophylactic and therapeutically. PSA treatment enhanced CD103 expressing dendritic cells (DCs) that accumulated in the cervical lymph nodes. Exposure of naïve DCs to PSA induced the conversion of naïve CD4+ T cells into interleukin (IL)-10-producing FoxP3+Treg cells. Protection against EAE was completely abrogated in IL-10-deficient mice. Our results show an important role for a molecule from human commensal bacteria in protecting against EAE and suggest the possibility for protection in MS.

Central Nervous System Demyelinating Disease Protection by the Human Commensal Bacteroides fragilis Depends on Polysaccharide A Expression

The importance of gut commensal bacteria in maintaining immune homeostasis is increasingly understood. We recently described that alteration of the gut microflora can affect a population of Foxp3+Treg cells that regulate demyelination in experimental autoimmune encephalomyelitis (EAE), the experimental model of human multiple sclerosis. We now extend our previous observations on the role of commensal bacteria in CNS demyelination, and we demonstrate that Bacteroides fragilis producing a bacterial capsular polysaccharide Ag can protect against EAE. Recolonization with wild type B. fragilis maintained resistance to EAE, whereas reconstitution with polysaccharide A-deficient B. fragilis restored EAE susceptibility. Enhanced numbers of Foxp3+Treg cells in the cervical lymph nodes were observed after intestinal recolonization with either strain of B. fragilis. Ex vivo, CD4+T cells obtained from mice reconstituted with wild type B. fragilis had significantly enhanced rates of conversion into IL-10–producing Foxp3+Treg cells and offered greater protection against disease. Our results suggest an important role for commensal bacterial Ags, in particular B. fragilis expressing polysaccharide A, in protecting against CNS demyelination in EAE and perhaps human multiple sclerosis.

Gut, bugs, and brain: Role of commensal bacteria in the control of central nervous system disease

The mammalian gastrointestinal track harbors a highly heterogeneous population of microbial organisms that are essential for the complete development of the immune system. The gut microbes or “microbiota,” coupled with host genetics, determine the development of both local microbial populations and the immune system to create a complex balance recently termed the “microbiome.” Alterations of the gut microbiome may lead to dysregulation of immune responses both in the gut and in distal effector immune sites such as the central nervous system (CNS). Recent findings in experimental autoimmune encephalomyelitis, an animal model of human multiple sclerosis, suggest that altering certain bacterial populations present in the gut can lead to a proinflammatory condition that may result in the development of autoimmune diseases, in particular human multiple sclerosis. In contrast, other commensal bacteria and their antigenic products, when presented in the correct context, can protect against inflammation within the CNS. Ann Neurol 2011

A commensal symbiotic factor derived from Bacteroides fragilis promotes human CD39+Foxp3+ T cells and Treg function

Polysaccharide A (PSA) derived from the human commensal Bacteroides fragilis is a symbiosis factor that stimulates immunologic development within mammalian hosts. PSA rebalances skewed systemic T helper responses and promotes T regulatory cells (Tregs). However, PSA-mediated induction of Foxp3 in humans has not been reported. In mice, PSA-generated Foxp3+ Tregs dampen Th17 activity thereby facilitating bacterial intestinal colonization while the increased presence and function of these regulatory cells may guard against pathological organ-specific inflammation in hosts. We herein demonstrate that PSA induces expression of Foxp3 along with CD39 among naïve CD4 T cells in vitro while promoting IL-10 secretion. PSA-activated dendritic cells are essential for the mediation of this regulatory response. When cultured with isolated Foxp3+ Tregs, PSA enriched Foxp3 expression, enhanced the frequency of CD39+HLA-DR+ cells, and increased suppressive function as measured by decreased TNFα expression by LPS-stimulated monocytes. Our findings are the first to demonstrate in vitro induction of human CD4+Foxp3+ T cells and enhanced suppressive function of circulating Foxp3+ Tregs by a human commensal bacterial symbiotic factor. Use of PSA for the treatment of human autoimmune diseases, in particular multiple sclerosis and inflammatory bowel disease, may represent a new paradigm in the approach to treating autoimmune disease.

A commensal bacterial product elicits and modulates migratory capacity of CD39+ CD4 T regulatory subsets in the suppression of neuroinflammation

Tolerance established by host-commensal interactions regulates host immunity at both local mucosal and systemic levels. The intestinal commensal strain Bacteroides fragilis elicits immune tolerance, at least in part, via the expression capsular polysaccharide A (PSA). How such niche-specific commensal microbial elements regulate extra-intestinal immune responses, as in the brain, remains largely unknown. We have recently shown that oral treatment with PSA suppresses neuro-inflammation elicited during experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. This protection is dependent upon the expansion of immune-regulatory CD4 T cells (Treg) expressing CD39, an ectonucleotidase. Here, we further show that CD39 modulation of purinergic signals enhances migratory phenotypes of both total CD4 T cells and Foxp3+ CD4 Tregs at central nervous system (CNS) lymphoid-draining sites in EAE in vivo and promotes their migration in vitro. These changes are noted during PSA treatment, which leads to heightened accumulation of CD39+ CD4 Tregs in the CNS. Deficiency of CD39 abrogates accumulation of Treg during EAE, and is accompanied by elevated Th1/Th17 signals in the CNS and in gut-associated lymphoid tissues. Our results demonstrate that immune-modulatory commensal bacterial products impact the migratory patterns of CD4 Treg during CNS autoimmunity via the regulation of CD39. These observations provide clues as to how intestinal commensal microbiome is able to modulate Treg functions and impact host immunity in the distal site.

Downregulation of IL-17 and IL-6 in the central nervous system by glatiramer acetate in experimental autoimmune encephalomyelitis

T helper 17 (Th17) cells are pivotal in the immune pathogenesis of EAE. Glatiramer acetate (GA) can enhance Treg FOXp3 expression. We demonstrate that GA downregulates the expression of both IL-17 and IL-6 in two different EAE models. Increased mRNA expression in CNS for ROR gamma t, IL-17, IL-12/IL-23, IL-6, TNF-alpha, STAT4 and Th1 cytokines were significantly reduced by GA with a concomitant rise in SMAD3. The increased expression of TNF-alpha, IL-6, and IL-17 in CNS of CD25+ depleted animals was suppressed by GA treatment. This study demonstrates that both Th1 polarization and Th17 expression are modulated by GA.

Augmentation of regulatory B cell activity in experimental allergic encephalomyelitis by glatiramer acetate

We recently showed that B cells reduce CNS inflammation in mice with experimental allergic encephalomyelitis (EAE). Here, we demonstrate that adoptively transferred CD5/CD19+ B cells protect against EAE severity. Furthermore, we show that glatiramer acetate (GA), a therapeutic for relapsing multiple sclerosis treatment, amplifies this effect. Transfer of GA-conditioned B cells leads to increased production of immunoregulatory cytokines and reduced CNS inflammation, as well as decreased expression of the chemokine receptor, CXCR5, and elevated BDNF expression in the CNS. Thus B cells can protect against EAE, and GA augments this effect in maintaining immune homeostasis and controlling EAE disease progression.

Increased expression of B cell-associated regulatory cytokines by glatiramer acetate in mice with experimental autoimmune encephalomyelitis

B cells are of increasing importance as a target for multiple sclerosis treatment. Here we show that GA treatment of mice with experimental autoimmune encephalomyelitis (EAE) biases cytokine production by B cells towards cytokines associated with regulation in MS including interleukin (IL)-4, -10 and -13 and reduces pro-inflammatory IL-6, IL-12, and TNF alpha levels. GA also down-regulates expression of B cell-activating factor (BAFF) of the TNF family and a proliferation-inducing ligand (APRIL), as well as the BAFF receptor in mice with EAE. Thus, GA impacts both B cell survival and B cell cytokine production during CNS inflammatory disease in an EAE model.

Glatiramer acetate biases dendritic cells towards an anti-inflammatory phenotype by modulating OPN, IL-17, and RORγt responses and by increasing IL-10 production in experimental allergic encephalomyelitis

Paralleling our previous mechanistic studies of glatiramer acetate (GA; Copaxone) activity, we show that GA curbs the expression of Toll-like receptor (TLR) 9 and the universal adapter protein Myd88 in mice with EAE, the animal model for multiple sclerosis. Concurrent with enhanced dendritic cell (DC) production of IL-10, GA interferes with OPN, IL-17, and ROR gamma expression in DCs of mice with EAE, and suppresses brain expression of the EAE-induced chemokines, MIP1α and β, IP-10 and RANTES. Thus GA not only biases dendritic cells towards an anti-inflammatory phenotype, but also suppresses the expression of factors that affect the blood-brain barrier penetration during neuroinflammation.