Biodegradable antigen-associated PLG nanoparticles tolerize Th2-mediated allergic airway inflammation pre- and postsensitization.

Specific immunotherapy (SIT) is the most widely used treatment for allergic diseases that directly targets the T helper 2 (Th2) bias underlying allergy. However, the most widespread clinical applications of SIT require a long period of dose escalation with soluble antigen (Ag) and carry a significant risk of adverse reactions, particularly in highly sensitized patients who stand to benefit most from a curative treatment. Thus, the development of safer, more efficient methods to induce Ag-specific immune tolerance is critical to advancing allergy treatment. We hypothesized that antigen-associated nanoparticles (Ag-NPs), which we have used to prevent and treat Th1/Th17-mediated autoimmune disease, would also be effective for the induction of tolerance in a murine model of Th2-mediated ovalbumin/alum-induced allergic airway inflammation. We demonstrate here that antigen-conjugated polystyrene (Ag-PS) NPs, although effective for the prophylactic induction of tolerance, induce anaphylaxis in presensitized mice. Antigen-conjugated NPs made of biodegradable poly(lactide-co-glycolide) (Ag-PLG) are similarly effective prophylactically, are well tolerated by sensitized animals, but only partially inhibit Th2 responses when administered therapeutically. PLG NPs containing encapsulated antigen [PLG(Ag)], however, were well tolerated and effectively inhibited Th2 responses and airway inflammation both prophylactically and therapeutically. Thus, we illustrate progression toward PLG(Ag) as a biodegradable Ag carrier platform for the safe and effective inhibition of allergic airway inflammation without the need for nonspecific immunosuppression in animals with established Th2 sensitization.

Antigen-specific tolerance in immunotherapy of Th2-associated allergic diseases.

Allergic diseases are an increasing health concern, particularly in the developed world. The standard clinical approach to treatment of allergic disease focuses on allergen avoidance and symptom control but does little to address the underlying Th2 bias of disease. Specific immunotherapy (SIT) consisting of controlled administration of allergen, however, has been demonstrated to successfully induce desensitization and tolerance in an antigen-specific manner for a variety of Th2-mediated diseases. This review focuses on the mechanisms by which current SIT approaches induce tolerance as well as discussing attempts to modify the safety and efficacy of SIT. These refinements focus on three major aspects of SIT: the route of antigen administration, modification of the antigen to remove allergenic epitopes and reduce adverse events and choice of adjuvant used to induce tolerance and/or immune deviation from Th2 to Th1 and regulatory T-cell (Treg) phenotypes. Synthesis of these recent developments in SIT provides considerable promise for more robust therapies with improved safety profiles to improve resolution of allergic disease and its associated costs.

Antigen-fixed leukocytes tolerize Th2 responses in mouse models of allergy.

Allergic diseases, including asthma and food allergies, are an increasing health concern. Immunotherapy is an effective therapeutic approach for many allergic diseases but requires long dose escalation periods and has a high risk of adverse reactions, particularly in food allergy. New methods to safely induce Ag-specific tolerance could improve the clinical approach to allergic disease. We hypothesized that Ag-specific tolerance induced by the i.v. injection of Ags attached to the surface of syngeneic splenic leukocytes (Ag-coupled splenocytes [Ag-SPs]) with the chemical cross-linking agent ethylene-carbodiimide, which effectively modulate Th1/Th17 diseases, may also safely and efficiently induce tolerance in Th2-mediated mouse models of allergic asthma and food allergy. Mice were tolerized with Ag-SP before or after initiation of OVA/alum-induced allergic airway inflammation or peanut-induced food allergy. The effects on disease pathology and Th2-directed cytokine and Ab responses were studied. Ag-SP tolerance prevented disease development in both models and safely tolerized T cell responses in an Ag-specific manner in presensitized animals. Prophylactically, Ag-SP efficiently decreased local and systemic Th2 responses, eosinophilia, and Ag-specific IgE. Interestingly, Ag-SP induced Th2 tolerance was found to be partially dependent on the function of CD25(+) regulatory T cells in the food allergy model, but was regulatory T cell independent in the model of allergic airway inflammation. We demonstrate that Ag-SP tolerance can be rapidly, safely, and efficiently induced in murine models of allergic disease, highlighting a potential new Ag-specific tolerance immunotherapy for Th2-associated allergic diseases.

The Use of Biodegradable Nanoparticles for Tolerogenic Therapy of Allergic Inflammation.

Antigen-specific tolerance is the ultimate aim of treatment of allergic diseases. Here, we describe methods for the use of biodegradable nanoparticles to safely induce tolerance for the prevention and treatment of allergic inflammation in mice. Antigen is either conjugated to the surface of carboxylated poly(lactide-co-glycolide) (PLG) or encapsulated within PLG nanoparticles, and the resulting antigen-associated nanoparticles are then washed prior to intravenous injection to inhibit antigen-specific allergic immune responses.