Abstract: Insect bite hypersensitivity (IBH) is an allergic dermatitis of horses caused by IgE-mediated reactions to bites of Culicoides and sometimes Simulium spp. The allergens causing IBH are probably salivary gland proteins from these insects, but they have not yet been identified. The aim of our study was to identify the number and molecular weight of salivary gland extract (SGE) proteins derived from Culicoides nubeculosus which are able to bind IgE antibodies (ab) from the sera of IBH-affected horses. Additionally, we sought to investigate the IgG subclass (IgGa, IgGb and IgGT) reactivity to these proteins. Individual IgE and IgG subclass responses to proteins of C. nubeculosus SGE were evaluated by immunoblot in 42 IBH-affected and 26 healthy horses belonging to different groups (Icelandic horses born in Iceland, Icelandic horses and horses from different breeds born in mainland Europe). Additionally, the specific antibody response was studied before exposure to bites of Culicoides spp. and over a period of 3 years in a cohort of 10 Icelandic horses born in Iceland and imported to Switzerland. Ten IgE-binding protein bands with approximate molecular weights of 75, 66, 52, 48, 47, 32, 22/21, 19, 15, 13/12 kDa were found in the SGE. Five of these bands bound IgE from 50% or more of the horse sera. Thirty-nine of the 42 IBH-affected horses but only 2 of the 26 healthy horses showed IgE-binding to the SGE (p<0.000001). Similarly, more IBH-affected than healthy horses had IgGa ab binding to the Culicoides SGE (19/22 and 9/22, respectively, p<0.01). Sera of IBH-affected horses contained IgE, IgGa and IgGT but not IgGb ab against significantly more protein bands than the sera of the healthy horses. The cohort of 10 Icelandic horses confirmed these results and showed that Culicoides SGE specific IgE correlates with onset of IBH. IBH-affected horses that were born in Iceland had IgGa and IgGT ab (p< or =0.01) as well as IgE ab (p=0.06) against a significantly higher number of SGE proteins than IBH-affected horses born in mainland Europe. The present study shows that Culicoides SGE contains at least 10 potential allergens for IBH and that IBH-affected horses show a large variety of IgE-binding patterns in immunoblots. These findings are important for the future development of a specific immunotherapy with recombinant salivary gland allergens.
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The study investigated proteins from the salivary glands of a species of insect (Culicoides nubeculosus) which cause allergies in horses. It found that as many as ten proteins from these insects can cause allergic reactions in horses, highlighting potential leads for targeted therapies.
Research Objectives and Methods
The research aimed to identify the allergens that cause Insect Bite Hypersensitivity (IBH) in horses, a disorder associated with skin inflammation due to allergic reactions from bites of insects like Culicoides and Simulium spp.
The researchers used a technique called “immunoblot”, which allows them to identify which proteins horses’ IgE antibodies (the ones involved in allergy reactions) bind to, to spot the problematic proteins in the salivary gland extracts (SGE).
The study included 42 horses with IBH and 26 healthy ones, including those born in Iceland, on mainland Europe and a group of Icelandic horses imported to Switzerland and exposed to the bites of Culicoides spp. over three years.
Key Findings
Ten proteins taken from the salivary glands of Culicoides nubeculosus insects were identified as capable of binding IgE antibodies from horse serum and hence potentially provoking allergic reactions in horses.
The affected horses showed a clear reaction, with IgE-binding onto the insect SGE, while this was significantly less likely in healthy horses.
The study further identified the variability in immune response among horses, with affected horses demonstrating a wide range of IgE-binding patterns.
Interestingly, horses born in Iceland showed a significantly higher number of antibodies against these allergens than horses born on mainland Europe, indicating a possible factor of geographical variation.
Implications
The study identified at least ten potential allergens in Culicoides SGE that cause IBH, which provides valuable direction for future research and treatment strategies.
The results also explore the importance of geographical variation, suggesting that horses from different locations may have different immune responses to the same allergens.
These findings contribute to the development of specific immunotherapies using salivary gland allergens.
Cite This Article
APA
Hellberg W, Wilson AD, Mellor P, Doherr MG, Torsteinsdottir S, Zurbriggen A, Jungi T, Marti E.
(2006).
Equine insect bite hypersensitivity: immunoblot analysis of IgE and IgG subclass responses to Culicoides nubeculosus salivary gland extract.
Vet Immunol Immunopathol, 113(1-2), 99-112.
https://doi.org/10.1016/j.vetimm.2006.04.009
Division of Clinical Research, Department of Clinical Veterinary Medicine, University of Berne, Bremgartenstr. 109 A, P.O. Box, 3001 Berne, Switzerland.