Progress made regarding the molecular characterization of

Progress made regarding the molecular characterization of the disease-causing Spadin has now opened the door for new forms of allergen-specific immunotherapy which allow reduced side effects and targeting of specific pathways of the allergic immune response (Niederberger et al., 2004, Creticos et al., 2006, Valenta et al., 2010). We have developed a strategy for AIT (i.e., B cell epitope-based allergy vaccines) which is based on fusion proteins consisting of non-allergenic peptides which are derived from the IgE binding sites of disease-causing allergens but do not bind IgE themselves and PreS, a surface protein from hepatitis B which serves as a non-allergenic carrier protein providing T cell help (Focke-Tejkl et al., 2015). The allergen-derived peptides used for the construction of the B cell epitope-based allergy vaccines lack IgE reactivity and therefore do not induce IgE-mediated side effects but focus blocking allergen-specific IgG towards the IgE binding sites of the allergen. In the vaccine allergen-specific T cell epitopes are reduced as much as possible (Focke-Tejkl et al., 2015; Niederberger et al., 2015) because, when present in previously engineered hypoallergenic allergen derivatives, they were found to cause late phase side effects (Campana et al., 2015). In the B cell epitope-based allergy vaccine concept the T cell help for the induction of allergen-specific IgG antibodies comes from T cell epitopes of the non-allergenic PreS carrier protein (Focke-Tejkl et al., 2015). Since grass pollen is one of the most important allergen sources world-wide and causes severe respiratory manifestations in allergic patients (Suphioglu et al., 1992), we constructed a grass pollen vaccine consisting of four recombinant derivatives of the four major timothy grass pollen allergens (i.e., Phl p 1, Phl p 2, Phl p 5, Phl p 6) based on the B cell epitope-based strategy. It has been demonstrated that with a combination of these four timothy grass pollen allergens all grass pollen allergic patients can be diagnosed (Linhart et al., 2005, Hatzler et al., 2012). The hypoallergenic peptides incorporated in the grass pollen allergy vaccine have been identified in combined approaches using epitope mapping and structural analyses of the allergens (Focke et al., 2001, Focke-Tejkl et al., 2014, Focke-Tejkl et al., 2015). The in vitro immunological characterization, experimental animal data and a safety skin test study performed in grass pollen allergic patients indicated that the vaccine lacks allergenic activity and has the potential to induce allergen-specific IgG antibodies upon vaccination, which compete with allergic patients IgE antibodies for the binding sites on the natural allergens (Focke-Tejkl et al., 2015, Niederberger et al., 2015).
Methods
Results
Discussion This AIT study is the first to investigate safety as well as clinical and immunological effects of a new strategy for AIT which is based on a B cell epitope-based recombinant allergy vaccine. It shows that three monthly injections of a vaccine consisting of four recombinant fusion proteins combining non-allergenic peptides derived from the four major timothy grass pollen allergens, Phl p 1, 2, 5 and 6 with the hepatitis B preS protein are effective in reducing allergen-induced immediate allergic reactions as demonstrated by the reduction of TNSS, TOSS and immediate skin responses in grass pollen allergic patients. We consider the reduction of the TNSS observed after vaccination with the 20 and 40 μg dose of BM32 as relevant because its magnitude is comparable to that observed after administration of systemic antihistamines in the pollen chamber model (Horak et al., 2010). Furthermore, it has been demonstrated that a one point difference in the rhinoconjunctivitis total symptom score is clinically relevant in grass pollen-induced allergic rhinoconjunctivitis (Devillier et al., 2014). The study further shows that the new B cell epitope based vaccine was very well tolerated although high doses of up to 160 μg of the four recombinant proteins per injection were administered without any up-dosing. In fact, the previous in vitro assessment of BM32 had shown that the vaccine exhibited almost no IgE reactivity and allergenic activity when exposed to basophils of allergic patients (Focke-Tejkl et al., 2015). It was found that allergic patients failed to exhibit any relevant immediate type skin reactions even when tested at the height of the grass pollen season (Niederberger et al., 2015). We also had reduced the presence of grass allergen-specific T cell epitopes in BM32 but a complete elimination of all T cell epitopes is not possible due to the diversity of allergic patients T cell epitope recognition. However, we found that the reduction of allergen-specific T cell epitopes in the vaccine resulted in a strong reduction of T cell and pro-inflammatory cytokine responses when BM32 was tested in PBMC cultures from grass pollen allergic patients (Focke-Tejkl et al., 2015). Accordingly, no late skin responses were found in grass pollen allergic patients when BM32 was applied by atopy patch testing (Niederberger et al., 2015).The latter study indeed suggests that BM32 has a strongly reduced potential to induce late phase, T cell-mediated side effects in patients.