Scientists have identified a number of molecular candidates for the components of canine allergens that trigger immune responses in humans – the first step in developing a vaccine against most causes of canine allergies.
There has been much research describing the nature and progression of dog allergies, but there have been very few applied studies that use this information to attempt to fully cure people of dog allergies by artificially inducing immune tolerance. But researchers have now for the first time identified candidates for the parts of the molecule that make up dog allergens that could provide us with precisely that: a “dog allergy vaccine”.
Their results were published in the Journal of the Federation of European Biochemical Societies on October 26th.
Dog allergy is a widespread disease that is increasing around the world. Over the years, scientists have been able to identify seven different canine allergens – molecules or molecular structures that bind to an antibody and produce an unusually strong immune response that would normally be harmless.
These seven are called Family dog Allergens 1 to 7 (Can f 1-7). But while there are seven, only one, Can f 1, is responsible for the majority (50-75 percent) of reactions in people with a canine allergy. It is found in tongue tissue, salivary glands, and skin of dogs.
Researchers need the IgE. still identify from Can f 1 Epitopes – those specific parts of the antigens that are recognized by the immune system and that stimulate or “determine” an immune response (this is why epitopes are also called Antigen determinants). More specifically, epitopes are short sequences of amino acids that make up part of a protein that induces the immune response.
Epitopes bind to a specific antigen receptor on the surface of immune system antibodies, B cells or T cells, much like the shape of one piece of the puzzle matches the specific shape of another piece of the puzzle. (The part of the receptor that binds to the epitope is again referred to as a Paratope). Antibodies, also known as immunoglobulin, come in five different classes or isotypes: IgA (for immunoglobulin A), IgD, IgE, IgG, or IgM. The IgE Isotype (only found in mammals) plays a key role in allergies and allergic diseases. There is also an IgE Epitope this is the piece of the puzzle that fits the IgE isotypes Paratope.
In the last few years, there has been a great deal of effort to develop epitope-focused vaccines – in this case a vaccine for dog allergies.
“We want to present the immune system with small doses of these epitopes in order to train it to deal with them, similar to the principle behind any vaccine,” said Takashi Inui, a specialist in allergy research, professor at the University of Osaka Prefecture and a lead author of the study. “But we cannot do this without first identifying the IgE epitope of Can f 1.”
So the researchers used X-ray crystallography (which involves analyzing the diffraction of X-rays by a material to identify its “crystal” structure) to determine the structure of the Can f 1 protein as a whole – the first time it has done so once done.
They found that, at first glance, the protein’s folding pattern is very similar to that of three other Can f allergens. However, the locations of the electrical surface charges were quite different, which in turn suggests a number of “residues” that are good candidates for the IgE epitope.
With this baseline data, more experimental work needs to be done to narrow down the candidates, but the results suggest that the development of a hypoallergenic vaccine against Can f 1 – a canine allergy vaccine – is within reach.
The manufacture of a “hypoallergenic vaccine” using such epitopes would not only be a world first in relation to dog allergies, but is rare in relation to allergic reactions. If the researchers’ work is actually used to develop a canine allergy vaccine, the principles behind it could be used much more broadly against various allergies.