30 August 2019

Allergy-Relieving Cat Food

Welcome back. An email from a high-school classmate mentioned that she would like to have a cat, but her daughter and a grandson are so allergic to cats, they’ve been to the emergency room several times. Commiserating, I told her about a recent study that might go a long way toward resolving that problem.

Although the researchers are affiliated with NestlĂ© Purina Research, a major manufacturer of cat food, it’s such a cool idea, I set aside the concern I raised in an earlier blog post, Research Sponsor Bias. They’re working to develop a cat food that can reduce cat allergens, the substances that cause allergic reactions.

Warren’s allergen scores in 2005 indicated
a high sensitivity to his family's three cats
(from blog post, Time for Allergies).
Cat Allergen
Of the potential allergens cats produce, Fel d1 is the most important. Fel d1 is a protein produced by their salivary and sebaceous glands and to a lesser extent by their skin. Cat saliva has the highest concentration.

As cats groom, their saliva spreads Fel d1 through their fur, where it is released to the environment when cats shed hair and dander. Fel d1 remains airborne for long periods, and it clings to fabrics, carpet and furniture.

Cat grooming itself, the saliva spreading Fel d1
(photo from catcheckup.com/why-cats-arch-their-backs).
In earlier work, the researchers showed the effects of Fel d1 could be neutralized in cat saliva with immunoglobulin Y.

(We interrupt this program to review some terms that may be new to you. Immunoglobulins are also known as antibodies. They are proteins the body produces to help fight antigens. Antigens are toxins or other foreign substances which stimulate an immune response, especially the production of antibodies. Antigens are unique to the pathogen (bacterium, virus or other disease-causing microorganism) and occur on the pathogen’s surface. Antibodies recognize and bind to particular antigens and aid in their destruction.)

Adding the Antibody to Cat Food
Immunoglobulin Y (abbreviated IgY) is the major antibody in bird, reptile and lungfish blood. High concentrations of IgY accumulate in chicken egg yolk and can be used to deliver antigen-specific IgY in food.

For the current study, the researchers set out to determine if adding an anti-Fel d1-IgY antibody to cats’ food instead of to their saliva would significantly reduce the active Fel d1 on cat hair.

An assortment of 105 cats (males, females, neutered, spayed and intact) completed a 4-week period of acclimation, followed by a 2-week control period and a 10-week test period. The cats were individually fed a complete and balanced diet in amounts adequate to maintain ideal body weight. During the test period, the food was supplemented with the antibody.

Hair was collected twice weekly during the control period and once weekly during the test period using a new brush for each cat and each collection. Approximately 100 milligrams of hair was taken from each brush for Fel d1 analysis.

Success! Cat food supplemented with the chicken egg antibody significantly reduced the active allergen on the cats’ hair. Half of the cats had a reduction of at least 50%, and 86% of the cats had a reduction of at least 30%. Baseline levels of the allergen were highly variable among cats, but cats with the highest initial levels showed the greatest decrease.

Active-Fel d1 means and standard errors over 10 weeks of testing with an anti-Fel d1-egg-IgY antibody added to cat food; means were significantly reduced from baseline at week 1 (P<0.05) and weeks 3 through 10 (P<0.001) (from onlinelibrary.wiley.com/doi/10.1002/iid3.244).
Wrap Up
Taking the next step, a collaborating investigator affiliated with Washington University School of Medicine conducted a 4-week pilot study. He exposed 11 cat-sensitive people to hair from cats fed the antibody diet and a control diet.

Key measures of allergy symptoms supported the benefits of the antibody diet over the control diet. The Total Nasal Symptom Score, which combines nasal congestion, nasal itching, sneezing and runny nose (rhinorrhea), was substantially reduced; and though the reduction in the Total Ocular Symptom Score was not statistically significant, scratchy and itchy eyes did show significant improvement.

If testing with a larger human population confirms these findings, this could be a real breakthrough for allergy-suffering cat lovers. Stay tuned, and thanks for stopping by.

Papers on adding antibody to cat food in Immunity, Inflammation and Disease and EMJ Allergy & Immunology journals:
Article on study on ScienceNews website:
Background on cat allergen, antibodies and immunoglobulin-Y from Wikipedia:

After preparing this post, I came across another recent study that’s equally promising. The investigators, nearly all from Switzerland, are working on a vaccine that would immunize cats to neutralize Fel d1. I refer you to: www.jacionline.org/article/S0091-6749(19)30349-5/fulltext

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