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Scientists from the University of Virginia have apparently approached to uncover the mystery behind a strange allergy to red meat caused by some tick bites. They report finding a way to trigger allergy in laboratory mice – an important step for the study of the disease. And with the help of animal experiments, they also claim to have identified significant changes in the immune system that can be caused by these bites.
Allergy to red meat is what happens when people become hypersensitized to alpha-gal sugar, produced in abundance by most mammals but not by primates (like us). Its symptoms are very similar to the typical food allergy, hives and swelling being common. Like other food allergies, these reactions can also be fatal and deserve immediate medical treatment.
Allergic reactions to red meat are usually delayed for hours after a meal, compared to the almost instantaneous reactions normally observed. And unlike other food allergies, the disease is mainly, if not exclusively, caused by the bites of some ticks. In the United States, the main cause is the Lone Star tick, common in all eastern, southeastern and south-central states, but other tick species from other countries have also been found. associated with allergy.
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At this point, there are still more questions than answers about the allergy to red meat. If the disease is probably rare, for example, we do not really know how often, or a single bite can transform an allergic person. More importantly, we do not know how these bites cause the allergy. Everyone has anti-alpha-gal antibodies, for example, but most of us do not have the specific type of immune response to meat – driven by a type of antibody called IgE – that characterizes the disease .
Animal models are often a crucial first step in the study of any disease or disorder in humans. And that's what the authors of the new study, published in the Journal of Immunology, say have managed to get. According to Loren Erickson, author and researcher specializing in UVA, it was not easy, because mice naturally produce alpha gal. This means that they usually do not have an immune response.
"So, our study used gene-deficient mice that make alpha-gal, which reflects humans lacking the gene that makes alpha-gal," he told Gizmodo.
In these alpha-gal deficient mice, they were then able to create the same IgE allergic reaction to eating meat as in the affected individuals. And as in humans, they induced allergy by exposing the skin of their mice to the proteins found in Lone Star ticks.
Earlier researchers have claimed to create mouse models to study allergy to red meat. But Erickson says his team's work is probably the first published research on a clinically relevant model, allowing him to study the immune responses of these allergic mice in "real time". It's something that would be much harder to do with people.
"One of the outstanding questions on the ground is what is the bite of the tick, or the tick itself, that induces an immune response to alpha-gal," Erickson said. "This model could be used to determine which chemicals / tick compounds trigger an immune response."
The model could also help researchers understand how these chemicals make the immune system become hypersensitive to alpha-gal.
For example, in their first experiments on mice, the team found evidence that a specific type of immune cell, called a CD4 + T cell, played a key role in the immune system's overreaction to alpha-gal , both during initial exposure to ticks and when mice ate meat afterwards.
Other research by the authors has shown that another type of immune cell, called cell B, is commonly present in large quantities in people allergic to red meat. And when the team created mice whose B cells could not produce a protein called MyD88, they no longer produced IgE in response to the ticks. MyD88 is thought to help immune cells communicate with the outside world through certain signaling pathways.
Removing MyD88 from people to prevent allergy to red meat is neither feasible nor practical (people who are genetically deficient in this disease are much more likely to develop severe bacterial infections, for example). But the findings provide new clues to researchers like Erickson and his team, who might one day discover a possible treatment or a way to prevent it. Currently, while some sufferers claim to be able to eat meat without incident after a while, others may have to live with the allergy forever.
The team then plans to take a closer look at the types of immune cells that are most responsible for creating the IgE antibodies that make us allergic to red meat, as well as getting this process going.
"If we can identify what these immune mechanisms are, it will give us an opportunity to develop therapeutic strategies to prevent the production of IgE antibodies directed against alpha-gal," Erickson said.
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