LOS ANGELES, March 27 (Xinhuanet) -- A molecule designed to block cat allergies successfully prevented allergic reactions in laboratory mice as well as in human cells in tests, US researchers said Sunday.
In a paper in the April issue of the journal Nature Medicine, scientists at the University of California Los Angeles (UCLA) said these promising results could lead to a new therapy not only for human cat allergies, but also possibly for severe food allergies such as those to peanuts.
The injectable treatment puts a brake on the release of a key chemical from cells involved in cat allergy reactions. That chemical, histamine, brings on allergy symptoms such as sneezing, wheezing, itching, watery eyes and sometimes asthma.
|A molecule designed to block cat allergies successfully prevented allergic reactions in laboratory mice as well as in human cells in tests.|
When a cat-allergic person touches or inhales a protein found in cat saliva or dander, key immune system cells respond by spewing out histamine. Experts estimate that 14 percent of children 6 to 19 years old are allergic to cats.
The treatment comprises a molecule that loosely links a feline and a human protein together. The feline end is a protein called Fel d1 found in cat dander and saliva that causes so much misery in allergy sufferers. On the other end sits a piece of human antibody that docks to a cell receptor that can be recruited to stop allergic reactions.
The investigators named the molecule GFD, or Gamma Feline Domesticus, for its human and feline parts, according to lead scientist Andrew Saxon of UCLA. The cat allergen end of GFD binds to antibodies on the surface of the cell. The human end of GFD links to a different cell surface protein that interrupts the allergic response.
Saxon's team first tested GFD in blood donated by people allergic to cats. Scientists cultured blood cells with either GFD or with a purified human antibody as a control. Then they added the cat protein that triggers allergic reactions to all the blood cell cultures.
"We measured more than 90 percent less histamine in the cultures with GFD," they wrote in the paper, "those results suggested that GFD successfully prevented the immune cells from reacting to cat allergen. The next step was to test GFD in mice that we had made allergic to the allergenic protein found in cat saliva and dander."
The researchers tested GFD in two different types of allergic mice. One set was genetically engineered to have human cat-allergy cell receptors. These mice would react to cat protein only after the scientists first injected them with human allergic antibodies to cats.
When these mice were injected with cat allergen, GFD blocked the allergic reaction involving the human cell receptors, an indication that it might also work in people.
Scientists made another set of mice allergic to cats by injecting them with cat protein and an immune system booster. Their reactions to cat allergen would be comparable to reactions in a cat-allergic person.
Then scientists injected some of these mice with GFD, and injected cat allergen into the windpipes of all the mice, including a control group that was not allergic to cats. They found GFD damped asthma-like and other allergic reactions in the cat-allergic mice.
The molecule has the potential to prevent allergic reactions long after injections cease, scientists said.
"This novel approach to treating cat allergies is encouraging news for millions of cat-allergic Americans. Moreover, these results provide proof-of-concept for using this approach to develop therapies to prevent deadly food allergy reactions as well," commented Anthony S. Fauci, head of US National Institute of Allergy and Infectious Diseases.
However, further research and clinical testing would be required before it might be used in humans, Saxon noted. Enditem