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Scientists are closer to understanding the strange meat allergy caused by ticks



The most common cause of red meat allergy in the United States is believed to be the Lone Star tick, Amblyomma americanum.
Photo: Allen G. Breed (AP)

Researchers at the University of Virginia have apparently come closer to revealing the mystery of a strange red meat allergy caused by certain tick bites. They report finding a way to trigger the allergy in lab mice – an important step in studying the condition. And with the help of animal experiments, they also claim that they have identified important changes in the immune system that can be caused by these bites.

Red meat allergy is what happens when humans become hypersensitive to sugar alpha-gal, which is abundantly produced by most mammals but not primates (like us). Its symptoms are much like the typical food allergy, where hives and swelling are common. Like other food allergies, these reactions can also be life-threatening and deserve immediate medical treatment.

Allergic reactions to red meat are usually delayed for hours after a meal, compared with the almost immediate reactions that normally occur. And unlike other food allergies, the condition is mainly, if not exclusively, caused by the bite of certain ticks. In the United States, the leading culprit has been the Lone Star fortress, which is common throughout the eastern, southeast, and south-central states, but other ticks in other countries have also been linked to the allergy.

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Right now there are more questions than answers about red meat allergy. Although the condition is probably rare, for example, we do not quite know how often it occurs, nor the chance that a single piece should make anyone allergic. Most important of all, we do not know how these chews reinforce the allergy. For example, everyone has alpha-gal antibodies, but most of us do not have the specific type of immune response to meat – led by a type of antibody called IgE – that characterizes the condition.

Animal models are often a crucial early step in studying any disease or disorder that exists in humans. And that's what the authors of the new study, published in the Journal of Immunology, say they've managed to pull off. But according to older author and UVA researcher Loren Erickson, it wasn't exactly easy, since mice naturally produce alpha-gal. This means that they do not usually have an immune response to it at all.

"Thus, our study used mice that are deficient in the gene that makes alpha-gal, which reflects people who also lack the gene that makes alpha-gal. crazy, "he told Gizmodo.

In these alpha-gal deficient mice, they were then able to create the same IgE-allergic reaction to eating meat seen in people with the condition. And as with humans, they induced the allergy by Exposing the skin of their mice to proteins found in Lone Star ticks.

Previous researchers have argued that they created mouse models to study red meat allergy, but Erickson says his team's work is probably the first published research of a clinical relevant model, one that allows the team to study the immune response of these allergic mice in "real time." It's something that would be much more difficult to do with humans.

"One of the outstanding questions in the field is what is it about the tick bit, or the tick itself, which induces an immune response to alpha gal, "Erickson said." This model could be used to find out which chemicals / compounds in the tick gene that triggers an immune response. "

The model can also help researchers understand how these chemicals make the immune system hypersensitive to alpha gal.

In their early mice experiments, for example, the team found evidence that a specific type of immune cell, called a CD4 + T cell, played a key role in the immune response to alpha-gal, both during the initial tick exposure and when the mice ate meat. afterwards.

Other research by the authors has found that another type of immune cell, called a B cell, is often found in high levels among people with red meat allergy. And when the team created mice whose B cells could not produce a protein called MyD88, the mice no longer produced IgE in response to the ticks. MyD88 is believed to help immune cells communicate with the outside world through certain signaling pathways.

To knock out MyD88 in humans to prevent red meat allergy is not exactly feasible or even practical (humans genetically deficient in it are much more likely to develop serious bacterial infections, for one). But the results provide new clues for researchers like Erickson and his team to track – clues that may one day reveal a possible treatment or way to prevent it. Currently, while some people with the condition report that they can eat meat without incident after a certain time, others may have to live with the allergy forever.

The team then plans to take a closer look at what types of immune cells are most responsible for creating IgE antibodies that make us allergic to red meat, as well as how the whole process gets started.

"If we can identify what these immune mechanisms are, it provides an opportunity to develop therapeutic strategies to prevent the generation of IgE antibodies against alpha-gal," Erickson said.


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