Allergy linked to carbohydrate transmitted by tick bite

An allergist with the University of Virginia’s School of Medicine has discovered a key component in the connection between tick bites and a rare meat allergy.

Researchers have known for roughly a decade that the bite of the Lone Star Tick can cause a flare up of Alpha-gal Syndrome.

The mechanism by which the pathogens work on the human immune system, however, has remained unknown.

Alpha-gal syndrome is a recently identified type of food allergy to red meat.

According to the Mayo Clinic, in the United States, the condition most often begins when a Lone Star tick bite transmits the alpha-gal sugar molecule into the body.

Alpha-gal sugars are found primarily in mammalian meat.

In some people, the presence of the sugars – also called carbohydrates – triggers a delayed immune system reaction that later produces mild to severe allergic reactions when they eat red meat.

The initial discovery was made in 2007 by UVA researcher and Oscar Swineford Professor of Medicine Thomas Platts-Mills, who realized that the alpha-gal carbohydrate was an ingredient in the cancer drug Cetuximab and was causing allergic reactions in patients from certain geographic areas.

Through various research methods, Platts-Mills realized that the sugars were transmitted when a Lone Star Tick fed on an animal rich in alpha-gal sugars, and then transmitted those sugars to a human victim.

The how and why it triggered alpha-gal syndrome, however, remained a mystery.

Until recently, that is, when UVA researcher Loren Erickson and his team in UVA’s Department of Microbiology, Immunology and Cancer Biology found that people with the meat allergy have an abundance of a distinctive form of immune cells known as B cells.

Also known as B lymphocytes, B cells are a type of lymphocyte white blood cell that functions in the immunity component of the adaptive immune system by secreting antibodies.

These antibodies then release chemicals that cause the allergic reaction to meat.

Erickson said the discovery marks the first clinically relevant model that he’s aware of, enabling researchers to move ahead and ask the important questions.

“We can actually use this model to identify underlying causes of the meat allergy that may inform human studies,” Erickson said. “So it's sort of a back-and-forth of experiments that you can do in animal models that you can't do in humans. But you can identify potential mechanisms that could lead to new therapeutic strategies so that we can go back to human subjects and test some of those hypotheses.”

PREVENTION IS KEY

According to the University of Delaware Cooperative Extension, Lone star ticks are extremely common in Delaware, and become active as soon as warm weather sets in each spring and summer.

Avoiding tick bites is the key to prevention. Protect against tick bites by wearing long pants and long-sleeved shirts and using insect repellents when you're in wooded, grassy areas.

The use of DEET insect repellent and a thorough, full-body tick check after spending time outside is also recommended.

People diagnosed with alpha-gal syndrome are often rumored to resort to vegetarianism to avoid flare-ups; however, poultry, fish, and in some people, lean meat such as venison, do not trigger a reaction, according to a 2013 article in the Sydney Morning Herald.

Alpha-gal allergies are the first known food allergies that cause delayed anaphylaxis, and are also the first known food-related allergy associated with a carbohydrate, rather than a protein.