Allergy is a Th2 dominated immune response. Currently, immunotherapy is performed with allergen together with aluminiumhydroxide (alum). It is well known that application of allergens together with alum enhance a Th2 type immune response. In contrast, CpG-oligodesoxynucleotides (ODN) could drive the immune response towards Th1. It was thus the aim of our study to investigate the immunomodulatory properties of protamine-based nanoparticles (proticles) with CpG-ODN, in comparison with alum as the classical adjuvant. We selected Ara h 2 from peanut as model allergen with high relevance in food allergy.
Protamine-based nanoparticles were complexed with Ara h 2 peanut allergen and injected subcutaneously into female BALB/c mice. Four more groups of BALB/c mice were treated either with PBS as a negative control, with Ara h 2 in alum as a positive control, with Ara h 2 alone, or with uncomplexed proticles. Immunizations were done every 14 days for four times. Blood was drawn one day before the first immunization and every 7 days after each immunization. The sera were analysed by ELISA for Ara h 2-specific antibodies to see which kind of immune response was induced. An indirect measurement of Ara h 2 specific IgE antibodies has been performed with a RBL (rat basophilic leukemia) cell assay. Also cytokine release from T-cells extracted from the spleen was measured and, furthermore, intradermal skin test reactivity was evaluated.
An increase of Ara h 2-specific IgG2a antibodies was found in mice immunized with Ara h 2 complexed proticles. In contrast, highest levels of Ara h 2-specific IgG1 and IgE antibodies were found in mice treated with Ara h 2 formulated in alum and Ara h 2 alone. Confirming the prevention of IgE induction, no degranulation was seen in the RBL assay with sera from the Ara h 2-Proticle group. Additionally IL-5 levels stayed low in this group. The increase of Ara h 2-specific IgG2a in parallel to negative IgE levels in ELISA and RBL-assay, as well as the cytokine profile indicate a Th1 driven immune response induced by proticles in complex with Ara h 2. These data suggest that protamine-based nanoparticles with CpG-ODN are suitable as carriers for immunotherapy of allergy.