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Review
. 2012 Aug 24:2:112.
doi: 10.3389/fcimb.2012.00112. eCollection 2012.

Does helminth activation of toll-like receptors modulate immune response in multiple sclerosis patients?

Affiliations
Review

Does helminth activation of toll-like receptors modulate immune response in multiple sclerosis patients?

Jorge Correale et al. Front Cell Infect Microbiol. .

Abstract

Multiple sclerosis (MS) is an inflammatory autoimmune demyelinating disease affecting the Central Nervous System (CNS), in which Th1 and Th17 cells appear to recognize and react against certain myelin sheath components. Epidemiological evidence has accumulated indicating steady increase in autoimmune disease incidence in developed countries. Reduced infectious disease prevalence in particular has been proposed as the cause. In agreement with this hypothesis, we recently demonstrated significantly better clinical and radiological outcome in helminth-infected MS patients, compared to uninfected ones. Parasite-driven protection was associated with regulatory T cell induction and anti-inflammatory cytokine secretion, including increased TGF-β and IL-10 levels. Interestingly, surface expression of TLR2, on both B cells and dendritic cells (DC) was significantly higher in infected MS patients. Moreover, stimulation of myelin-specific T cell lines with a TLR2 agonist induced inhibition of T cell proliferation, suppression of IFN-γ, IL-12, and IL-17 secretion, as well as increase in IL-10 production, suggesting the functional responses observed correlate with TLR2 expression patterns. Furthermore, parasite antigens were able to induce TLR2 expression on both B cells and DCs. All functional effects mediated by TLR2 were abrogated when MyD88 gene expression was silenced; indicating helminth-mediated signaling induced changes in cytokine secretion in a MyD88-dependent manner. In addition, helminth antigens significantly enhanced co-stimulatory molecule expression, effects not mediated by MyD88. Parasite antigens acting on MyD88 induced significant ERK kinase phosphorylation in DC. Addition of the ERK inhibitor U0126 was associated with dose-dependent IL-10 inhibition and reciprocal enhancement in IL-12, both correlating with ERK inhibition. Finally, cytokine effects and changes observed in co-stimulatory DC molecules after helminth antigen exposure were lost when TLR2 was silenced. Overall, the data described indicate that helminth molecules exert potent regulatory effects on both DCs and B cells from MS patients through TLR2 regulation.

Keywords: MyD88; helminth; mitogen activated protein kinase; multiple sclerosis; parasites; soluble egg antigen; toll-like receptors.

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Figures

Figure 1
Figure 1
Mechanisms involved in MS pathogenesis. (1) Peripheral activation; (2) Migration of activated lymphocytes across the Blood-Brain-Barrier; (3) Reactivation of lymphocytes in the CNS and secretion of pro-inflammatory mediators; (4) Induction of demyelination; (5) Induction of axonal damage.
Figure 2
Figure 2
Baseline expression of TLRs on B cells (A) and dendritic cells (B). CD19+ B cells and dendritic cells, were isolated from peripheral blood mononuclear cells using specific isolation kits according manufacturer's instructions to a purity of 95–98%. TLR2, TLR4, TLR5, and TLR9 expression was assessed in B cells and monocyte derived dendritic cells from helminth-infected MS patients, uninfected MS patients, and healthy controls, using flow cytometry. Mean fluorescence intensity (MFI) of TLR expression was corrected after subtracting MFI of the control antibody isotype. TLR2 expression in infected MS patients was found to be significantly higher (p < 0.001) than in uninfected MS patients or healthy controls. In contrast, MFI of TLR4, TLR5, and TLR9 did not differ between groups. Data represent mean values ± SEM from 12 subjects for each group.
Figure 3
Figure 3
SEA upregulated TLR2 expression on B cells and dendritic cells, from helminth-infected MS patients. B cells and dendritic cells were cultured for 48 h in the presence and in the absence of SEA, or PPD used as control antigen. TLR expression was evaluated using flow cytometry, and results expressed as mean fluorescence intensity. Following exposure to SEA, TLR2 was markedly up-regulated in B cells and dendritic cells from helminth-infected MS patients. In contrast, no significant changes were observed in TLR2 expression after PPD exposure. Likewise, exposure to SEA did not affect TLR4, TLR5, or TLR9 expression on B cells or dendritic cells. Data illustrate MFI from a representative patient. Similar results were observed in 11 additional patients.
Figure 4
Figure 4
Summary of putative mechanisms through which helminths could modulate MS. (A) Helminth-derived products influence the development of specific immunosuppressive mechanisms through interactions with dendritic cells, and B cells. (B) Signaling-dependent mechanisms generated by helminth products. Binding of carbohydrates or glycolipid helminth-derived products trigger MAPK cascades, resulting in c-Fos phosphorylation. (C) Helminth-derived products favor Th2 responses in dendritic cells by signaling-independent pathways mediated by RNAses, cystatins, and cathepsins.

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