ICAM1 and allergen-specific nanobodies for allergy treatment

Pollen allergens belong to the most important initiators causing seasonal allergies. The recognition of allergens by specific IgE antibodies is a key event for the initiation of allergic inflammation. The prevention of the IgE binding to its specific allergen results in antagonizing the cascade of allergic inflammation and hence in the absence of allergic symptoms. It has been already demonstrated that allergen-specific IgG antibodies, if directed towards IgE epitopes on given allergens, inhibit the binding of IgE antibodies to allergens. This is the reason why within the scope of their joint project both applicants based on their professional expertise will generate pollen allergen-specific antibodies to investigate their potential to prevent allergy. For this purpose the powerful nanobody generation technology will be applied for the first time providing the generation of a large number of different nanobodies including probably also nanobodies that are able to inhibit IgE binding to allergens. Thus, this technology represents a significant improvement compared to used methods so far. The isolated nanobodies will be investigated to identify those that are able to inhibit the IgE binding to allergens and hence have protective potential and are suitable candidates for passive treatment of seasonal allergies. In parallel, the efficacy of the isolated allergen-specific nanobodies for topical treatment for seasonal allergies will be analyzed. For this purpose allergen-specific nanobodies will be combined with ICAM1-specific nanobodies which will be also generated within the frame of this project to form bi-specific constructs. These bi-specific nanobodies derivatives will be tested for their potential to inhibit allergen penetration across mucosal epithelium. The immobilization to ICAM1 is desirable because the applicants could show recently that ICAM1 is an appropriate attachment point to bind allergens via bi-specific antibodies. Another advantage to use ICAM1 for immobilizing bi-specific nanobody derivatives is that ICAM1 is also the receptor for many rhinovirus strains and consequently the bi-specific nanobody derivative could be used to prevent rhinovirus infection by inhibiting rhinovirus to penetrate the body.

Allergic symptoms (runny nose, itchy red eyes, sneezing) elicit by pollen allergens are cumbersome for affected individuals causing a substantial decreased quality of life. The rapidly increasing frequency of IgE-mediated allergies has emphasized the necessity to act and to devise various strategies for effective interventions. Passive administration of allergen-specific IgG antibodies that inhibit the binding of IgE antibodies to allergens and therefore abrogate allergic inflammation is one successful option to deal with pollen allergies. However, the time-consuming large-scale production of clinical-grade quality IgG antibodies resulting in high expenses prompted researchers and policymaker to search for equivalent alternatives. Within this project, we succeeded to develop a very attractive and also cost-effective alternative to antibodies. We generated allergen-specific nanobodies, small antibodies with many beneficial properties and demonstrated for the first time that they reduce allergen-induced basophil activation. With this important observation, we offered the first proof that allergen-specific nanobodies have great potential to be further developed for future pollen allergy treatment. While the described results serve as foundation to prepare a nanobody-based drug for systemic application, we also pursued a second, very innovative administration route. We selected the nose and eyes to immobilize allergen-specific nanobodies on their mucosal surfaces. This protective nanobody shield should stop allergen penetration into the body. For this purpose, we combined allergen-specific nanobodies with nanobodies recognizing the intercellular adhesion molecule-1 (ICAM-1). ICAM-1 is a cell surface receptor that is highly up-regulated in epithelial cells of allergic patients representing an ideal anchor for our bi-specific nanobodies. To date, we managed to show that our bi-specific nanobodies remain immobilized to the cell surface and were able to simultaneously bind allergens. Whether our bi-specific nanobodies are able to prevent allergens from crossing the cell barrier has still to be thoroughly tested. This proof of principle analysis is currently on going and if necessary, the approach will be refined and driven forward within a follow-up project.