Researchers at Osaka Prefecture University in Japan have managed to pinpoint spots on certain molecules produced by dogs that are the strongest allergens. This could pave the way for more effective remedies.
Allergies to dogs are increasingly widespread and there are currently no truly effective vaccines to combat them fully. The most frequent reactions to this allergy are skin problems, conjunctivitis and asthma attacks. The reason for this failure is both the type of vaccines created to date, which are relatively non-specific, and the fact that the allergic reaction can be triggered by no less than seven different molecules (allergens), called Canis familiaris allergens 1-7 or Can f 1-7. These are released by a dog’s tongue, salivary glands and skin. This is why producing a vaccine that induces tolerance to all seven is complicated.
These molecules are very similar proteins. They are only different in their spatial conformation, as it is known in technical jargon (i.e. the shape a molecule takes when synthesised by cells). This different conformation is precisely what causes the intensity of allergic reactions.
Can f 1 is by far the most allergenic protein of all and is responsible for 50-75% of cases. Researchers at Osaka Prefecture University in Japan began with this molecule and identified its three-dimensional structure in atomic detail for the first time, using a technique called X-ray crystallography. They then compared it with other Can f molecules to identify with complete precision the points (epitopes) that can trigger a faulty reaction by the immune system in susceptible people. An allergy is precisely this exaggerated reaction to 'enemies' that are in reality harmless molecules, like those in the Can f 1 'series'.
Small but important differences
In particular, Japanese researchers have identified a 'sensitive' epitope, described in the FEBS Journal, that is targeted by type E immunoglobulins (antibodies) specific to allergic reactions.
To discover it, the scientists used sophisticated systems to measure the different electrical charges (caused by the respective chains of amino acids, the 'building blocks' of proteins) that make Can f 1 different from Can f 2, 4 and 6. These tiny differences proved to be very important from a technical point of view and enabled researchers to identify the Can f 1 epitope on which to focus to obtain a more effective vaccine with the utmost precision.
Paving a new way
Allergy vaccines are not really vaccines in the classic sense. Their aim is to induce tolerance to the allergen, i.e. to teach the immune system to recognise it and not to overreact when it encounters it. In order to achieve this, small and increasingly concentrated doses of the allergen are usually administered. However, this technique is not always successful because it is often difficult to identify the ‘correct’ molecule. This is why efforts have long been made to produce vaccines that only contain those parts of the allergen important for the reaction (epitopes).
This study by researchers in Osaka is only the first step towards more effective vaccines, and more in-depth study and testing is needed, but it is doubly innovative: the information that has emerged may not only form the basis on which to develop highly ‘tailored’ vaccines for dog allergies, but also paves the way for possible 'epitope vaccines' for other allergies.