IBH is a Th2 type, IgE mediated allergy with an imbalance between Th1, Th2 and Treg (Hamza et al., 2007; Hamza et al., 2010; Hamza et al., 2008; Heimann et al., 2011). It is therefore important to use Th1/Treg focusing adjuvants or agents to induce and/or rebalance the Th1:Th2:Treg responses and restraint the inflammatory mechanisms. The route of injection has also to be considered and we have shown that injecting directly into the lymph nodes with the appropriate adjuvant is a promising option (Jonsdottir et al., 2015; Jonsdottir et al., 2016). Vaccination with purified allergens in Alum/monophosphoryl lipid A (MPL), but not in Alum alone, resulted in a Th1/Treg focused immune response. The IgG antibodies induced efficiently blocked the binding of IgE from IBH horses to the allergens (Jonsdottir et al., 2016). It has been demonstrated that allergen-specific IgG antibodies that compete with IgE for binding to the allergens are one of the major mechanisms in successful immunotherapy.
The year 2019 the intralymphatic vaccination with purified allergens in Alum/MPL will be reinforced in more horses and compared to subcutaneous vaccination a more practical injection route.
In order to test whether the vaccination protects the horses from developing insect bite hypersensitivity a challenge experiment has to be performed where the vaccine is tested under real conditions. A challenge experiment is planned 2020. The allergens for the vaccine will be chosen according to the microarray and the injection method depending on the results obtained from the 2019 vaccination experiment.
Twenty-six horses will be vaccinated in Iceland early year 2020 and challenged by exporting them to Switzerland in the spring to see if the vaccine protects them from SE.
The horses must be kept in Culicoides areas and be naturally exposed to the midges for 3 summers. No protection is allowed. The horses will be monitored, blood samples taken on a regular basis and clinical examination performed to look for an evidence of IBH.