The regulatory dendritic cell marker C1q is a potent inhibitor of allergic inflammation.

The complement subunit C1q was recently identified as a marker for monocyte-derived regulatory dendritic cells supporting the differentiation of interleukin (IL)-10-secreting CD4+ T cells with a suppressive activity. Furthermore, C1q expression is upregulated in peripheral blood mononuclear cells of allergic patients in the course of successful allergen immunotherapy. Herein, we investigated a potential direct role of C1q in downregulating allergic inflammation. In mice with ovalbumin (OVA) or birch pollen (BP)-induced allergic asthma, C1q is as efficacious as dexamethasone to reduce both airway hyperresponsiveness (AHR), eosinophil, and ILC2 infiltrates in bronchoalveolar lavages, as well as allergen-specific T helper 2 cells in the lungs. Administration of C1q does not expand IL-10+/Foxp3+ regulatory T cells in the lungs, spleen, or in the blood. Depletion of plasmacytoid dendritic cells (pDCs) abrogates the capacity of C1q to reduce AHR and eosinophilic infiltrates in OVA-sensitized mice. Also C1q treatment inhibits the activation of human and mouse pDCs by CpGs, thereby demonstrating a critical role for pDCs in the anti-inflammatory activity of C1q. We conclude that regulatory dendritic cells can mediate a potent direct anti-inflammatory activity via the expression and/or secretion of molecules such as C1q, independently of their capacity to expand the pool of regulatory T cells.

Evaluation of therapeutic sublingual vaccines in a murine model of chronic house dust mite allergic airway inflammation.

BACKGROUND: Second generation therapeutic vaccines based upon recombinant allergens or natural extracts, potentially formulated in vector systems or adjuvants, are being developed. To this aim, preclinical studies in relevant animal models are needed to select proper allergens, formulations and administration schemes. OBJECTIVE: To develop a chronic house dust mite (HDM) allergy model to evaluate sublingual therapeutic vaccine candidates. METHODS: The BABL/c mice that were used were sensitized with Dermatophagoides pteronyssinus (Dpte) and Dermatophagoides farinae (Dfar) mite extracts by intraperitoneal injections followed by aerosol exposures. Animals subsequently underwent sublingual immunotherapy (SLIT) with either Dpte, Dfar or Dpte/Dfar extracts, twice a week for 8 weeks. SLIT efficacy was assessed by whole body plethysmography, lung histology and broncho-alveolar lavages cell counts. Specific T cell and antibody responses to major and minor HDM allergens were monitored in tissues and serum/saliva, respectively. RESULTS: Mice sensitized to Dpte and Dfar allergens exhibited strong airway hyperresponsiveness (AHR) and lung inflammatory infiltrates including eosinophils. Sensitized animals mounted Th2-biased cellular and humoral responses specific for group 1 and 2 major allergens, as well as group 5, 7 and 10 minor allergens. This phenotype was sustained for at least 2 months, allowing the evaluation of immunotherapeutic protocols with HDM extracts-based vaccines. In this model, SLIT decreased AHR and Th2 responses and induced HDM-specific IgAs in saliva. The Dpte/Dfar mix proved the most efficacious when compared to Dpte or Dfar extracts alone. CONCLUSIONS AND CLINICAL RELEVANCE: The efficacy of a sublingual vaccine based on a Dpte/Dfar allergen extract mix was demonstrated in a well standardized murine model of chronic allergic airway inflammation based on clinically relevant mite allergens. The latter will be used as a benchmark for evaluation of future vaccines, including recombinant allergens. This HDM allergic airway inflammation animal model is a useful tool to design and select candidate vaccines to be tested in humans.

Targeting the allergen to oral dendritic cells with mucoadhesive chitosan particles enhances tolerance induction.

BACKGROUND: Sublingual immunotherapy (SLIT) efficacy could be improved by formulations facilitating allergen contact with the oral mucosa and uptake by antigen-presenting cells (APCs). METHODS: Two types of chitosan microparticles, differing in size and surface charge, were tested in vitro for their capacity to improve antigen uptake and presentation by murine bone marrow-derived dendritic cells (BMDCs) or purified oral APCs. T-cell priming in cervical lymph nodes (LNs) was assessed by intravenous transfer of carboxyfluorescein diacetate succinimidyl ester-labelled ovalbumin (OVA)-specific CD4+ T cells and flow cytometry analysis. Ovalbumin-sensitized BALB/c mice were treated sublingually with soluble or chitosan-formulated OVA twice a week for 2 months. Airway hyperresponsiveness (AHR), lung inflammation and T-cell responses in cervical and mediastinal LNs were assessed by whole-body plethysmography, lung histology and Cytometric Bead Array technology, respectively. RESULTS: Only a mucoadhesive (i.e. highly positively charged) and microparticulate form of chitosan enhances OVA uptake, processing and presentation by murine BMDCs and oral APCs. Targeting OVA to dendritic cells with this formulation increases specific T-cell proliferation and IFN-gamma/IL-10 secretion in vitro, as well as T-cell priming in cervical LNs in vivo. Sublingual administration of such chitosan-formulated OVA particles enhances tolerance induction in mice with established asthma, with a dramatic reduction of both AHR, lung inflammation, eosinophil numbers in bronchoalveolar lavages, as well as antigen-specific Th2 responses in mediastinal LNs. CONCLUSIONS: Mucoadhesive chitosan microparticles represent a valid formulation for sublingual allergy vaccines.