A tick that causes meat allergy

Kristina Carlson didn’t give much thought to the tick she tore off her body while hiking in the North Carolina mountains in September 2020. A month later, at home in Mississippi, Carlson went to her doctor complaining of pain. joint pain and a bloated feeling in the stomach. They ruled out rheumatoid arthritis and the blood work showed nothing significant. Soon after, Ella Carlson began to suffer from eye infections. In February 2021, a strange rash appeared on her face. Her ER doctor treated her for shingles, but the rash did not improve.

When he returned to his doctor’s office, a nurse asked him: Do you remember if you have been bitten by a tick? They did another blood test, which revealed that he had antibodies associated with alpha-gal, a carbohydrate found in the meat and fat of non-primate mammals.

Alpha-gal syndrome is an allergic reaction that can occur after being bitten by the lone star tick. Named for the white dot that adorns the back of adult females, these ticks are typically found in the southeastern and south central United States. They obtain the alpha-gal molecule from the mammals they feed on and pass it on to people they bite.

Currently, individuals of these ticks have been found in New Jersey and Long Island, and have already been reported further north, on the East Coast and in areas of the Midwest. Its spread is beginning to concern researchers about the long-term complications of alpha-gal syndrome, so they are trying to find out the cause of the allergy by using genetically modified meat.

Typically, when a person eats meat from a non-primate mammal, such as a cow or a pig, their body does not react to the alpha-gal carbohydrate. But when a tick bite introduces the molecule into a person’s body, the immune system recognizes it as an invader and produces antibodies known as immunoglobulin E (IgE) to fight it off. IgE antibodies bind to different types of white blood cells: in the bloodstream, to basophils, and in the tissues, to mast cells. The next time those cells come into contact with alpha-gal from any source, including meat, the antibodies will recognize it and the immune system will attack it.

“Producing IgE would be like loading a gun,” explains Scott Commins, associate director of the Department of Allergy and Immunology at the University of North Carolina School of Medicine and one of the leading researchers on alpha-gal syndrome. . “What will pull the trigger will be the subsequent consumption of mammalian meat.”

The resulting allergic reactions, which usually begin two to six hours after ingesting alpha-gal, vary from person to person. They can be as mild as a simple tingling in the mouth or as extreme as anaphylactic shock. Some people with this syndrome may eat a double cheeseburger and experience only a slight itch in the palms of their hands or scattered hives. Others, on the other hand, ingest a small portion of pork fat present in a plate of refried beans and suffer anaphylaxis. After eating meat, Carlson immediately experienced tingling and sometimes sores in his mouth. Over the next 24 hours, his eyes would often become sore, his joints would swell, rashes would appear on various parts of his body, and his left arm would swell.

There is currently no treatment or antidote for alpha-gal syndrome. Epinephrine is often the first resort for treating anaphylaxis, and other allergic reactions can be treated with a variety of medications, including antihistamines and corticosteroids. People with this syndrome go to great lengths to avoid eating foods that can trigger the allergic reaction. When the consumption of mammalian meat and other products is stopped, the symptoms usually subside. “I eliminated all hoofed animal products from my diet, and the rash, infection, joint pain, and inflammation disappeared,” says Carlson.

One consolation for both Carlson and most of the 34,000 Americans with alpha-gal syndrome is that sensitivity to meat doesn’t appear to be permanent, usually disappearing after four to five years. That’s because the cells of the immune system responsible for the IgE response are a type of immature B lymphocytes called plasmablasts. According to Commins, it appears that these cells do not become cells that are part of the long-term immune memory, so they will not lie in wait throughout a person’s life, which they do, for example, those activated by certain vaccines that keep an eye on invaders for decades.

However, people who spend a lot of time outdoors, such as forest rangers and surveyors, may be bitten by ticks on a regular basis. “These patients seem to develop long-lasting memory cells,” says Commins. “Unfortunately, in your case the allergy may be permanent.”

The lone star is spreading

It is expected that more and more cases of people with alpha-gal syndrome will appear, since, as Richard S. Ostfeld, a disease ecologist and renowned scientist at the Cary Institute for Ecosystem Studies in the United States, warns, “it seems It could be that the tick is spreading.” “Unfortunately, our country does not have an active tick surveillance program in place.” Point-in-time records suggest that the lone star tick’s range is expanding, “but we lack rigorous high-quality data on where they are and how fast they are moving.”

It is also difficult to know why they are spreading. The main hypothesis has to do with climate change, but the researchers do not dare to reach that conclusion because it is difficult to verify it. “Some studies indicate that as the planet continues to warm, the geographic range of the lone star tick will not expand, but other studies suggest just the opposite,” Ostfeld says.

What is clear is that a changing climate like the current one is lengthening the active season for at least some species of ticks, increasing the chance that people will come across this arachnid. In the case of the black-legged tick that is commonly found in New York state, Ostfeld stresses that “we have shown that both the larval and nymphal stages appear earlier and earlier as the climate warms. Since the lone star tick behaves in a similar way, it is expected that its active season will be lengthened as well.”

The lone star tick measures just over three millimeters and is very aggressive. Often found in large groups, it can detect the heat and carbon dioxide emitted by humans two meters away. And then “they try to hunt you down,” says Ostfeld. “Literally, they run at you.”

The researchers want to find out if alpha-gal IgE might contribute to or exacerbate other conditions. In a small 2018 study, Commins and his colleagues associated the antibody with unstable plaques in coronary arteries. In a larger 2022 study that Commins was not involved in, researchers associated heart attacks with alpha-gal allergy. “We’re trying to understand if this immune response to alpha-gal is part of something larger,” says Commins.

It has also been in talks with Revivicor, a biotech subsidiary of United Therapeutics that specializes in raising pigs to harvest organs for transplantation into humans. They genetically modify the animals so they don’t carry alpha-gal, because that carbohydrate also causes the human body to reject pig organs. In 2020, the United States Food and Drug Administration approved the meat of these “free range” pigs for human consumption. For the past few months, Revivicor has been shipping meat to allergy sufferers and is considering selling it online.

Commins would like to study people who eat meat “without gal.” If the alpha-gal molecule has been removed but people continue to react to meat, the true cause of the syndrome will need to be reconsidered. “We think it’s alpha-gal, but I think those people’s tests would confirm that,” says Commins.

Sarah Goudarcy

#tick #meat #allergy

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