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Cat Allergy Discovery Could Help Dog Lovers Too

Cat allergy

If you suffer with a cat allergy, new findings may explain why and could even help develop new ways to provide relief for allergy sufferers. Dog lovers who experience allergy symptoms may get some help as well.

Why are some people allergic to cats?

Among the people who say they are allergic to cats, some have only mild allergic reactions while others suffer a great deal. Indeed, there are people in the former group who live with cats and eventually get used to or grow out of their allergic response.

I am fortunate enough to be counted among that group and have lived with several cats over the past few decades. For individuals with severe reactions who fall into the latter group, however, such a “getting over” response is much less likely to occur.

At the University of Cambridge, a team of scientists say they have discovered why some people experience an extreme reaction to cats, a response that has remained a mystery until now. That reaction appears to involve a newly uncovered activity of the cat allergen called Fel d1, which is found in cat dander and is also known to be a culprit in allergies to dust mites.

So far, researchers have identified five allergens in cats, and Fel d1, which is secreted by the sebaceous glands in the skin, is the most common. The next most common cat allergen is Fel d4, which is in cat saliva.

Scientists have discovered that some people have a severe reaction to cats when two factors are present. One is that the Fel d1 allergen triggers a pathogen recognition receptor (protein) called Toll-like receptor 4 (TLR4), which has already been shown to be involved in allergic reactions to dust mites and nickel.

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The other factor is that Fel d1 is assisted by a common environmental bacterial toxin called lipopolysaccharide. Lipopolysaccharides are large molecules found in certain bacteria, and they act as endotoxins (toxins that are released when bacteria die) as well as trigger a significant immune response.

In the new study, the authors exposed human cells to cat and dog dander. Lipopolysaccharides were added to some samples and not others.
Using a series of tests, the investigators discovered that lipopolysaccharides enhanced the response to Fel d1and that TLR4 was the specific part of the immune system that was reacting to the mixture of Fel d1 and lipopolysaccharides.

This discovery led them to block TLR4 with a drug, which caused the cat dander protein to have no impact on human cells, thus no allergic response. This good news also appears to extend to dogs, because the allergen Can f6, found in dog dander, also triggers TLR4 when lipopolysaccharides are present.

Other info on cat allergies
Earlier in 2013, the results of other new research on cat allergies were presented at the annual meeting of the American Academy of Allergy, Asthma and Immunology. The findings of the two-year study were promising for those who are allergic to cats.

According to Mark Larche, PhD, professor of medicine at the Michael G. DeGroote School of Medicine at McMaster University, who presented the study results, participants in the research who took the new treatment for three months were still experiencing fewer allergy symptoms a full two years after treatment.
However, the new cat allergy therapy, which Larche said “has the potential to revolutionize treatment for cat allergy patients,” needs further study and so it could be two years before it is on the market.

Therefore, at least several groups of researchers are working on ways to fight cat allergy, and it appears significant progress is being made. According to Clare Bryant, lead author of the new study, the team is hopeful that their work will “lead to new and improved treatments for cat and possibly dog allergy sufferers.”

Hafner R et al. Two year persistent treatment effect achieved after 4 doses of cat-peptide antigen desensitization (Cat-PAD) in an environmental exposure chamber (EEC) model of cat allergy. The Journal of Allergy and Clinical Immunology 2013 Feb; 131(2): Suppl. AB147
Herre J et al. Allergens as immunomodulatory proteins: the cat dander protein Fel d1 enhances TLR activation by lipid ligands. Journal of Immunology, published ahead of print 22 July 2013