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1.  Chitin Particles Are Multifaceted Immune Adjuvants 
Rationale: Chitin is a ubiquitous polysaccharide in fungi, insects, allergens, and parasites that is released at sites of infection. Its role in the generation of tissue inflammation, however, is not fully understood.
Objectives: We hypothesized that chitin is an important adjuvant for adaptive immunity.
Methods: Mice were injected with a solution of ovalbumin and chitin.
Measurements and Main Results: We used in vivo and ex vivo/in vitro approaches to characterize the ability of chitin fragments to foster adaptive immune responses against ovalbumin and compared these responses to those induced by aluminum hydroxide (alum). In vivo, ovalbumin challenge caused an eosinophil-rich pulmonary inflammatory response, Th2 cytokine elaboration, IgE induction, and mucus metaplasia in mice that had been sensitized with ovalbumin plus chitin or ovalbumin plus alum. Toll-like receptor-2, MyD88, and IL-17A played critical roles in the chitin-induced responses, and MyD88 and IL-17A played critical roles in the alum-induced responses. In vitro, CD4+ T cells from mice sensitized with ovalbumin plus chitin were incubated with ovalbumin-stimulated bone marrow–derived dendritic cells. In these experiments, CD4+ T-cell proliferation, IL-5, IL-13, IFN-γ, and IL-17A production were appreciated. Toll-like receptor-2, MyD88, and IL-17A played critical roles in these in vitro adjuvant properties of chitin. TLR-2 was required for cell proliferation, whereas IL-17 and TLR-2 were required for cytokine elaboration. IL-17A also inhibited the generation of adaptive Th1 responses.
Conclusions: These studies demonstrate that chitin is a potent multifaceted adjuvant that induces adaptive Th2, Th1, and Th17 immune responses. They also demonstrate that the adjuvant properties of chitin are mediated by a pathway(s) that involves and is regulated by TLR-2, MyD88, and IL-17A.
PMCID: PMC3029935  PMID: 20656945
chitin; adjuvant; ovalbumin; aluminum hydroxide; alum
2.  Targeting Toll-like receptors on dendritic cells modifies the TH2 response to peanut allergens in vitro 
Delivery of allergens with bacterial adjuvants has been shown to be a successful immunotherapeutic strategy for food allergy treatment in animal models. How microbial signals, acting through the innate immune system, reshape ongoing allergic responses is poorly understood.
To investigate the contribution of Toll-like receptors in the response to bacterial adjuvants, we designed an in vitro system to characterize the effect of heat-killed E.coli on peanut-induced responses of dendritic cells (DCs) and T cells.
Wild-type or Toll-Like Receptor (TLR) signaling-deficient bone-marrow derived DCs were pulsed with crude peanut extract alone (CPE) (50 µg/mL) in the presence of heat-killed E.coli (HKE) (106/mL). DC maturation was analyzed by flow cytometry. Treated DCs were co-cultured with CFSE-labeled CD4+ T cells from sensitized mice. Cytokine production from DCs and T cells was measured by bioplex assays.
Peanut pulsed DCs induced the production of IL-4, IL-5, IL-13 as well as IL-17 and IFN-γ from primed T cells. Adding HKE to CPE-pulsed DCs resulted in a significant decrease in Th2 cytokine production, associated with an increase in IFN-γ and profound attenuation of T cell proliferation. These effects were linked to HKE-induced, TLR-dependent changes in DC reactivity to CPE, especially the production of polarizing cytokines such as IL-12.
TLR signals modulate peanut-induced DC maturation in vitro leading to changes in the T cell response to peanut. These TLR effects must be confirmed in vivo and may constitute another alternative for allergen immunotherapies.
PMCID: PMC2902661  PMID: 20538332
Peanut allergy; EMP-123; Dendritic cell; Toll-like receptor; MyD88; IL-12
3.  Exosome release of β-catenin: a novel mechanism that antagonizes Wnt signaling 
The Journal of Cell Biology  2010;190(6):1079-1091.
The tetraspanins CD9 and CD82 suppress Wnt signaling by promoting the discharge of β-catenin from cells.
CD82 and CD9 are tetraspanin membrane proteins that can function as suppressors of tumor metastasis. Expression of CD9 and CD82 in transfected cells strongly suppresses β-catenin–mediated Wnt signaling activity and induces a significant decrease in β-catenin protein levels. Inhibition of Wnt/β-catenin signaling is independent of glycogen synthase kinase-3β and of the proteasome- and lysosome-mediated protein degradation pathways. CD82 and CD9 expression induces β-catenin export via exosomes, which is blocked by a sphingomyelinase inhibitor, GW4869. CD82 fails to induce exosome release of β-catenin in cells that express low levels of E-cadherin. Exosome release from dendritic cells generated from CD9 knockout mice is reduced compared with that from wild-type dendritic cells. These results suggest that CD82 and CD9 down-regulate the Wnt signaling pathway through the exosomal discharge of β-catenin. Thus, exosomal packaging and release of cytosolic proteins can modulate the activity of cellular signaling pathways.
PMCID: PMC3101591  PMID: 20837771
4.  Impact of Lactic Acid Bacteria on Dendritic Cells from Allergic Patients in an Experimental Model of Intestinal Epithelium 
Lactic acid bacteria (LAB) are Gram positive nonpathogenic commensal organisms present in human gastrointestinal tract. In vivo, LAB are separated from antigen-presenting cells such as dendritic cells (DC) by the intestinal epithelial barrier. In this study, the impact of one LAB strain (Lactobacillus casei ATCC393) on human monocyte-derived DC from allergic and healthy donors was assessed by using a polarized epithelium model. Confocal and flow cytometer analyses showed that immature DC efficiently captured FITC-labelled L. casei through the epithelial layer. After interaction with L. casei, DC acquired a partial maturation status (i.e., CD86 and CD54 increase) and increased their interleukin (IL)-10 and IL-12 production. Interestingly, after activation by L. casei in the presence of experimental epithelium, DC from allergic patients instructed autologous naïve CD4+ T cells to produce more interferon-γ than without the epithelium. Thus by modulating human DC reactivity, LAB and intestinal epithelium might modify T cell immune response and regulate the development of allergic reaction.
PMCID: PMC1847481  PMID: 17497025

Results 1-4 (4)