Innovative vaccine effective in treating horses with chronic allergy issues

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An innovative vaccine developed by European researchers shows promise in treating horses with chronic allergy-related problems.

It was developed by scientists at the University of Bern and the University of Zurich in co-operation with private-sector partners.

They developed a new vaccine therapy based on virus-like nanoparticles, which serves as a carrier of a so-called T-cell epitope, an enhancer of the body’s immune response.

Summer eczema on the head of a horse. Photo: Antonia Fettelschoss-Gabriel / USZ
Summer eczema on the head of a horse. Photo: Antonia Fettelschoss-Gabriel / USZ

By supporting the immune system, the vaccine is particularly suitable for older and immunocompromised animals.

It was likely to change the way pets are treated medically, according to Professor Martin Bachmann, of the University Department of Rheumatology, Immunology and Allergology at the University Hospital Bern.

The clinical potential of the vaccine for use in veterinary medicine is described in two articles in the Journal of Allergy and Clinical Immunology, the most cited journal in the field of allergy and clinical immunology.

The researchers report breakthroughs in the treatment of insect sting hypersensitivity (summer eczema) in horses and allergic dermatitis in dogs.

Allergic skin reactions due to insect bites are the most common form of allergies in horses. They manifest in weeping and bleeding wounds, as well as crusting, dandruff, swelling and thickening of the skin.

Thirty-four affected Icelandic horses participated in a placebo-controlled, double-blind clinical study conducted by a research team headed by Antonia Fettelschoss-Gabriel from the University Hospital Zurich and the University of Zurich. Nineteen horses were vaccinated, 15 were given a placebo.

The vaccine consisted of two interconnected components. The first component activates the immune system based on the mentioned virus-like nanoparticle. The second component is IL-5, a specific molecule that regulates the development and activation of so-called eosinophils, which play a significant role in allergies.

IL-31 is the central mediator of the itching. Allergens that penetrate the skin activate mast cells on the one hand and type 2 T helper cells on the other. Both cell types then turn off IL-31, which stimulates peripheral nerves to send an itch to the brain. When IL-31 is neutralized by antibodies, the itching stops. Image: M. Mohsen / University of Bern
IL-31 is the central mediator of the itching. Allergens that penetrate the skin activate mast cells on the one hand and type 2 T helper cells on the other. Both cell types then turn off IL-31, which stimulates peripheral nerves to send an itch to the brain. When IL-31 is neutralized by antibodies, the itching stops. Image: M. Mohsen / University of Bern

Immunization with this combined vaccine was well tolerated, according to the researchers, limiting the number of eosinophils in the skin and thereby reducing tissue damage. This resulted in substantially reduced skin lesions in vaccinated animals compared to the previous season, and in comparison to the placebo group.

“Unlike traditional desensitization, which tries to make the immune system tolerant to allergens, we specifically targeted the main triggers of insect hypersensitivity, the eosinophils,” Fettelschoss-Gabriel said.

Eosinophils also play a key role in allergic human asthma. The new findings gained in horses may help to develop a similar therapy in humans.

Bearded mosquitoes (Culicoides) inject allergens during the bloodsucking process, which activate type 2 T helper cells. These produce interleukin 5 (IL-5), which attracts tissue-damaging eosinophils. If IL-5 is blocked by vaccination, no eosinophils are accumulated in the skin and the damage is eliminated. Image: M. Mohsen / University of Bern
Bearded mosquitoes (Culicoides) inject allergens during the bloodsucking process, which activate type 2 T helper cells. These produce interleukin 5 (IL-5), which attracts tissue-damaging eosinophils. If IL-5 is blocked by vaccination, no eosinophils are accumulated in the skin and the damage is eliminated. Image: M. Mohsen / University of Bern

The findings in dogs were equally encouraging.

Atopic dermatitis is the most common allergic skin disease in dogs. Extensive itching causes scratches that lead to loss of coat and secondary skin infections and speed up the symptoms. It not only affects the well-being of dogs, but also affects their owners because the dogs are constantly scratching.

Researchers led by Bachmann and Professor Claude Favrot from the Department of Veterinary Medicine at the University of Zurich described the development of a virus-like particle-based vaccine against the causative agent of the disease of dogs, the protein IL-31. It proved an effective treatment.

Dogs that were particularly sensitive to dust mites had far fewer itching symptoms. The vaccination against IL-31 in dogs could also lead to the development of a similar human vaccine against itch-associated diseases.

The full team of researchers involved in the study were variously affiliated with University Hospital Bern, the universities of Bern and Zurich, Oxford University in England, and the Latvian Biomedical Research & Study Center.

Fettelschoss-Gabriel et al .: Treating insect-bite hypersensitivity in horses with active vaccination against IL-5, Journal of Allergy and Clinical Immunology , 04 April 2018 https://doi.org/10.1016/j.jaci.2018.01.041

Bachmann et al .: Vaccination against IL-31 for the treatment of atopic dermatitis in dogs , 04 April 2018, https://doi.org/10.1016/j.jaci.2017.12.994

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