Allergens used for allergen specific immunotherapy (ASIT) can induce side effects due to the binding of IgE immobilized on mast cells to allergens. To prevent IgE binding, recombinant allergens from house dust mites (HDM) Dermatophagoides farinae Der f 2 or Aspergillus fumigatus (AF) fungi Asp f 3 were encapsulated into nanoparticles (NPs) developed from biodegradable polymers chitosan and alginate. Core NPs 400-440 nm in diameter and zeta potential +8 mV were prepared from amphiphilic chitosan derivative N-lauryl-N’-succinoylchitosan (LSC). Allergens Der f 2 or Asp f 3 were introduced during core NP formation. To mask allergens additionally, allergen loaded core NPs were coated by alginate shell. As a result of polyelectrolyte interaction between positively charged LSC and negatively charged alginic acid core-shell type NPs were formed which were 450-550 nm in diameter and zeta potential –13 to –20 mV. We demonstrated that the encapsulation of allergens into core NPs significantly decreased IgE reactivity while core–shell NPs masked the allergens completely, as was shown using IgE positive sera from patients allergic to HDMs or AF. Injection s.c. of both core and core-shell NPs into mice induced allergen specific IgG response comparable to free allergens. We concluded that encapsulation of allergens into coreshell NPs could increase the safety and preserve the efficacy of preparations for ASIT.
Type I allergic reactions are characterized by the formation of E class antibodies to harmless microorganisms that enter the body from the environment, such as tree or grass pollen, fragments of domestic microorganisms, food, etc. For more than 100 years, the only method to reduce allergic symptoms was allergen specific immunotherapy (ASIT), which consists of the long-term courses (up to 3 years) of subcutaneous (s.c.) administration of allergen extracts in very low doses . S.c. administration of allergens to allergic patients is associated with the development of IgE mediated reactions, which can reach the level of anaphylactic shock. Therefore, the main aim in the design of new formulations for ASIT is to prevent the recognition of allergens, incorporated into vaccines, by IgE immobilized on the mast cells in order to avoid the risk of adverse reactions. Modification of allergens such as treatment with glutaraldehyde (change of protein conformation), the use of mutant forms of allergens (removal of some IgE binding sites), conjugation of allergens with polymers (masking of some antigenic sites), etc are well known approaches to reduce allergenic and protect immunogenic properties of allergens [2–4]. Modified allergens with reduced ability to interact with IgE are much safer and can be used at doses several times higher than those of the standard allergen extracts. At the moment, intensive research is being conducted to produce anti-allergic vaccines based on nanotechnology including chitosan nanoparticles (NPs) [5, 6]. Chitosan is a natural biocompatible and biodegradable polymer with adjuvant activity. Encapsulation of HDM allergens into chitosan-based NPs was carried out by Liu Z. et al [7–9] where the effects of Der f 2 47–67 peptide  or allergen extract [8, 9] incorporated into chitosan NPs were studied. Administration of allergen containing NPs via intraperitoneal (peptide) , intranasal or sublingual routes (extract) [8, 9] reduced symptoms in the mouse model of HDM allergy. However, it is not clear whether the encapsulation is sufficient to prevent human IgE recognition. Earlier we have shown that incorporation of HDM allergens into single polymer NPs is not sufficient to completely prevent IgE binding and additional shell is required for safe allergen packaging .