Immunogenicity and allergenicity of Culicoides imicola (Diptera: Ceratopogonidae) extracts.

The research is about understanding the properties of the insect, Culicoides imicola, that cause allergic reactions (termed as “sweet itch”) in horses during the summer. The study also investigates whether the severity of the allergic reactions is related to specific levels of antibodies.

Background Information and Objectives

• The allergic skin reactions experienced by horses, known as “sweet itch” or Summer Seasonal Recurrent Dermatitis (SSRD), are thought to be caused by allergens present in several Culicoides species.
• The particular insect species, Culicoides imicola (C. imicola), is studied, suspected to be a causative agent of SSRD in horses in Israel.
• The primary objective of the research was to identify the components of C. imicola that had immunogenic and allergenic properties – in simpler terms, to identify the parts of the insect that can provoke an immune response and cause allergies.

Research Methods and Techniques

• Whole body extracts of C. imicola were injected into susceptible horses to observe hypersensitivity reactions – an intensified allergic reaction.
• The researchers attempted to identify and isolate portions of the whole body extracts to determine their immunogenic and allergenic potency.
• The rabbits were introduced to the whole body extracts of C. imicola and then the reactivity of their induced immune response was examined.
• The allergenic potency was tested by exposing the extracts to horse sera (the clear fluid part of blood) and observing the reaction.
• The researchers also carried out specific immunoglobulin E (IgE) and immunoglobulin G (IgG) ELISA tests (tests to measure specific types of antibodies in the blood) to assess the body’s immune response in susceptible and non-susceptible horses.

Main Findings and Conclusions

• The research identified various antigenic components – parts able to provoke an immune response – in the C. imicola extracts.
• Despite demonstrating that these components can elicit an immune response, the research did not find conclusive evidence linking increased IgE levels with allergic reactivity, contrary to some previously held notions regarding allergic responses.
• The study concluded that the identified components were capable of generating an immune response, but clear evidence indicating that these allergic reactions in horses were due to specific corresponding antibody levels was not found through this study.