How tick bites can lead to meat allergies

When most people think of food allergies, they think of things like nuts, eggs, or shellfish. However, red meat has been causing more allergic reactions in recent years, and the culprit is a sugar molecule found in red meat called galactose-alpha-1,3-galactose, or alpha-gal. The picture is complicated by the fact that people do not tend to be naturally allergic to the sugar molecule found in red meat but instead become allergic to it after experiencing a tick bite.

The tick that leads to the red meat allergy has been linked to the lone star tick, which has a white spot in the shape of Texas on its back and is generally found in the southeastern United States. Dr. Thomas Platts-Mills, a lead allergy research from the University of Virginia helped to identify this critical link after he himself developed the meat allergy.

When Platts-Mills heard that an effective cancer drug, called cetuximab, was causing allergy-like side effects in 10x more people living in the southeastern United States than those living elsewhere, he decided to partner with Bristol-Myers Squibb, the drug’s distributor, to conduct blood tests. He found that all the cancer patients experiencing this reaction had pre-existing antibodies to the alpha-gal sugar. The sugar was indeed found in abundance in cetuximab.

What was causing people living in the southeastern United States to develop this sensitivity to alpha-gal sugar? The area where these cancer patients lived mapped on to the same geographical area where Rocky Mountain spotted fever, a disease carried by the lone star tick, occurs. With this clue, Platts-Mils screened more patients with meat allergies, and his studies revealed that 80% of these patients had reported tick bites. The tick bites resulted in 20x more antibodies to the alpha-gal sugar.

While Platts-Mills’ work helped to reveal the role of tick bites in red meat allergies and the allergic reaction to cetuximab, the mechanism by which the bite confers this sensitivity to the alpha-gal sugar is not yet understood. Some researchers have suggested that a virus or bacteria carried in the tick’s saliva may cause the change in the immune system of those who have been bitten.

A former member of Platts-Mills’ team at the University of Virginia is now conducted research on mice at the University of North Carolina to improve our understanding of how ticks cause these allergies. Now that more red meat allergies are being reported outside the southeastern United States – namely in Duluth, Minnesota, the eastern tip of Long Island, and Hanover, New Hampshire, one important question researchers are interested in is whether the lone star tick has traveled to new parts of the country, or if instead ticks of other species now cause the red meat allergies. Research that improves our understanding of how exactly ticks enable these allergies will hopefully enable us to develop effective interventions to reduce the suffering that accompanies these allergies.

Author
Dr. Summit Shah

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