Liposomal encapsulation of house dust mite allergens and dexamethasone modulates allergic response in a murine model of asthma

Background: House dust mite (HDM) allergens are a major cause of asthma worldwide. HDM extracts or purified allergens are the current treatment of choice known as specific immunotherapy. The aim in such strategy is to drive immune reaction away from the allergic Th2 response by inducing Th1 and/or Treg cellular response. In that regard, Toll Like Receptor-activating adjuvants have been used for inducing Th1 response, but adjuvants capable of inducing the somehow safer Treg response are poorly investigated. Methods: We describe the anti-allergic properties, in a therapeutic murine model of asthma, of HDM allergens Der s1 and Der s2 co-encapsulated with dexamethasone into dehydration-rehydration vesicles (DRV). Dexamethasone is a cortisol analogue with immune-suppressor activity known to induce specific Treg response, still with some adverse effects associated to systemic or prolonged use. Optimal lipid composition in terms of physical-chemical and anti-allergic properties was assessed using DRV liposomes of cholesterol and different phosphatidyl-cholines (PC) encapsulating Der s1+Der s2 allergens. Dipalmitoil-PC:cholesterol liposomes encapsulating different doses of dexamethasone were used to assess anti-allergic effects. Results: All liposomal compositions produced similar vesicle size, protein encapsulation and overall safe profile in treated mice. Preliminary results indicate that encapsulation of HDM allergens Der s1+Der s2 and dexamethasone into liposomes diminishes allergic response traits such as IL-5 interleukin and IgG1 and IgE antibody levels. Conclusion: These results highlight the possibility of using delivery systems such as liposomes to modulate immune response and to prevent adverse reactions to free or soluble pharmacological compounds like dexamethasone.