Scientists have identified a number of molecular candidates for the parts of dog allergens that cause immune reactions in humans, which is the first step toward developing a vaccine against the majority of dog allergy causes.
Many studies have been conducted to describe the nature and progression of dog allergies, but there have been very few applied studies that use this information to try to cure people of dog allergies completely by artificially inducing immune tolerance. However, for the first time, researchers have identified candidates for those parts of the molecules that make up dog allergens that could provide us with exactly that: a “dog allergy vaccine.”
Their findings were published in the journal of the Federation of European Biochemical Societies. Being allergic to dogs is a common condition that is spreading around the world. Scientists have identified seven different dog allergens over the years – molecules or molecular structures that bind to an antibody and cause an unusually strong immune response that would normally be harmless.
Canis familiaris allergens 1–7 are the names given to these seven allergens (Can f 1-7). However, of the seven, only one, Can f 1, is responsible for the majority (50-75%) of reactions in people allergic to dogs. It is found in the tongue tissue, salivary glands, and skin of dogs.
We want to be able to present small doses of these epitopes to the immune system to train it to deal with them, similar to the principle behind any vaccine. However, we won’t be able to do so unless we first identify the Can f 1 IgE epitope.
Takashi Inui
Can f 1’s IgE epitopes have yet to be identified by researchers — those specific parts of the antigens recognized by the immune system and stimulate or ‘determine’ an immune response (which is why epitopes are also called antigen determinants). Epitopes are short amino acid sequences that are part of a protein that triggers an immune response.
Epitopes, like the shape of a jigsaw puzzle piece, bind to a specific antigen receptor on the surface of immune system antibodies, B cells, or T cells. (The portion of the receptor that binds to the epitope is referred to as a paratope.) Antibodies, also known as immunoglobulins, are classified into five isotypes or classes: IgA (for immunoglobulin A), IgD, IgE, IgG, and IgM. The IgE isotype is important in allergies and allergic diseases. There is also an IgE epitope, which is a puzzle piece that fits the paratope of the IgE isotype.
In recent years, there has been a great deal of effort put into developing epitope-focused vaccines, such as a vaccine against dog allergies.
“We want to be able to present small doses of these epitopes to the immune system to train it to deal with them, similar to the principle behind any vaccine,” said Takashi Inui, an allergy researcher and professor at Osaka Prefecture University, as well as the study’s lead author. “However, we won’t be able to do so unless we first identify the Can f 1 IgE epitope.”
So, for the first time, the researchers used X-ray crystallography (the analysis of x-ray diffraction through a material to determine its ‘crystal’ structure) to determine the structure of the Can f 1 protein as a whole.
They discovered that the protein’s folding pattern appears to be very similar to three other Can f allergens. The locations of surface electrical charges, on the other hand, were quite different, implying a series of ‘residues’ that are good candidates for the IgE epitope.
More experimental work is needed to narrow down the candidates using this basic data, but the findings suggest that developing a hypoallergenic vaccine against Can f 1 – a dog-allergy vaccine – is within our grasp.
The development of a ‘hypoallergenic vaccine’ using such epitopes would not only be a world-first for dog allergies, but also for any allergic reaction. If the researchers’ work is used to develop a dog allergy vaccine, the principles behind it could be used to treat a wide range of allergies.
