Dog Allergy Vaccine May Be On Hand, Scientists Say
Dog allergies have inspired many studies on their origin and development, but so far scientists have not been able to identify specific allergens that may provide a cure.
Allergies to dogs are increasingly reported worldwide, causing sleep problems, eczema and itchy skin and difficulty breathing in people with asthma. Today scientists published the results of a study in the Federation of European Biochemical Societies journal that found a way to develop an allergy vaccine in dogs.
Scientists have already identified seven different allergens, which are molecules or molecular structures that bind to an antibody, causing the immune system to overreact. These allergens are called Canis familiaris 1 to 7 (Can f 1-7). However, it is only one allergen, Can f 1, which causes about 50 to 75 percent of reactions in people with allergies to dogs. Can f 1 is found on the skin, tissue of the tongue and salivary glands of dogs.
So far, scientists have failed to identify the IgE epitopes of Can f 1 – the parts of antigens recognized by the immune system that stimulate or determine an immune response. Epitopes are also called antigenic determinants. Epitopes are sequences of amino acids in proteins that cause the immune system to overreact.
Epitopes get stuck in a paratope – a specific part of antigen receptors – on the surface of immune system antibodies called B cells or T cells, much like pieces of a puzzle. Also called immunoglobulins, there are five different isotypes or classes of antibodies: IgA (for immunoglobulin A), IgD, IgE, IgG, and IgM. Present only in mammals, the IgE isotype has a key role to play in allergies. And there is a specific IgE epitope which corresponds to the paratope of the IgE isotype.
“We want to be able to present small doses of these epitopes to the immune system to train it to manage them, just like the principle of any vaccine,” said study co-author Takashi Inui. , from Osaka Prefecture University, Japan. “But we can’t do that without first identifying the Can f 1 IgE epitope.” Takashi, an allergy researcher, was also involved in earlier efforts to develop an epitope-focused vaccine.
Using x-ray crystallography, where x-rays are diffracted through a material to identify its structure, researchers have identified for the first time the structure of the Can f 1 protein as a whole. They determined that Can f 1 closely resembles three other Can f allergens. But the location of the electric charges on the surface of Can f 1 was quite different. This suggests that there are residues on the surface which may be good candidates for interlocking with the IgE epitope.
Although more research is needed, an epitope-based allergy vaccine would be revolutionary not only for canine allergens, but any other allergic reaction as well. The principles used in the new study could also be used to fight other common allergies.
Dogs, cats, rodents, birds, and other feathered or furry animals lose microscopic patches of skin called dander, which can cause allergic reactions and asthma attacks, according to the American Lung Association.
Additionally, proteins found in the saliva, urine and feces of dogs and cats can cause such reactions. Dried saliva can fall from a pet’s fur and be carried through the air, where it can be inhaled by the allergic person. Dust from dried feces can be inhaled in the same way.
Animal fur does not itself cause allergic reactions: short-haired and hairless animals also contribute dander to indoor air pollution, just like long-haired animals.
Pet allergens, according to the association, can stay in the air for long periods of time, and much longer than allergens left behind by cockroaches and mites. The microscopic size of these allergens allows them to easily adhere to bedding, fabrics, furniture and objects carried around homes. They have been found in schools, public buildings, and even homes without animals.
According to a study published in the journal Allergy Asthma and Immunology Research, at least 20% of the world’s population suffers from canine allergies.
Edited by Siân Speakman and Kristen Butler