How Does a Tick Bite Cause Meat Allergies? A Study Provides New Genetic Insights



Numerous significant molecules implicated in anaphylaxis to mammalian meat have had their structures elucidated, paving the way for potential future therapies.

Scientists have discovered the genetic and molecular makeup of certain important components linked to the potentially lethal mammalian-meat allergy brought on by tick bites.

The study, which was conducted by scientists at the Garvan Institute of Medical Research, explains how antibodies interact with the sugar molecule galactose-1,3-galactose (alpha-gal/alpha-gal), which is produced by all mammals with the exception of humans and higher primates. It adds credence to the idea that the main chemical in this specific allergy is -gal.

When some tick species, such as the endemic paralysis tick Ixodes holocyclus of Eastern Australia, bite individuals and transmit -gal, the immune system may perceive the exposure as hazardous and set off an allergic reaction, which can occasionally be fatal.

Daniel Christ, a professor, studies the structure of an antibody molecule (right). Research Institute for Medical Sciences, Garvan

A certain antibody type (3-7) has a natural pocket into which -gal fits well, according to the study's lead author Professor Daniel Christ, Head of Antibody Therapeutics and Director of the Centre for Targeted Therapy at Garvan.

"We have more than 70 different types of antibodies, and -gal recognition makes this one highly overrepresented. According to Professor Christ, we appear to have a genetic predisposition to being sensitive to this sugar.

The new research, which was just published in the Proceedings of the National Academy of Sciences journal, opens the door for prospective treatment options for treating the uncommon allergic reaction.

The advantage for development of an immunological response to -gal

Researchers examined the blood of patients with mammalian-meat allergies to identify the antibodies that were made; they discovered that the 3-7 type was usually formed in reaction to -gal.

The evidence suggests that having an antibody response that can mobilize against -gal has evolutionary advantages.

"We don't know why, but over evolution, humans lost the ability to make -gal," explains Associate Professor Joanne Reed, a senior author of this work from the Westmead Institute. "It might have anything to do with defense against infectious disease,"

Professor Christ cites new findings on malaria that demonstrate the Plasmodium parasite has a -gal surface coating. A quick immune reaction to -gal may kill the parasite before it establishes, defending a person from malaria.

NSW is a global hub for allergies to mammalian meat brought on by ticks.

The highest frequency in the world and more than 1800 cases of mammalian-meat allergy are found in Sydney's northern suburbs. Another hotspot is the Queensland hinterland along the Sunshine Coast near Maleny. These regions are home to the Ixodes holocyclus paralysis tick.

The first clinician to connect tick bites with mammalian-meat allergy was Professor Sheryl van Nunen, an allergy specialist at Sydney's Northern Beaches Hospital and a co-author of the study. She claims that she sees two persons with this allergy every week on average.

It is unknown why some people experience anaphylaxis while others do not. According to Professor van Nunen, it might be connected to the quantity of saliva injected, the frequency of tick bites, or hereditary vulnerability.

According to Professor van Nunen, exposure occurs when -gal, a substance found in the saliva of some tick species, is injected during a bite. According to her, about one-third of individuals who have developed a sensitivity to -gal will also show signs of an allergy to mammalian meat. Furthermore, a second bite can more than double the adverse reaction. The presence of meat components in food, such as beef broth, soft cheeses like feta or goat's cheese, or even gelatin, might have an adverse effect on some persons who have a severe allergy.

Director of the Translation Research Pillar at Garvan, Professor Robert Brink, emphasizes the high caliber and interdisciplinary character of the activity. "The Garvan Institute of Medical Research boasts state-of-the-art expertise in genomics and antibody technology. In order to better understand mammalian-meat allergy, a significant and developing public health concern for Australia and NSW in particular, our study merges these two domains.

Reference: David B. Langley, Peter Schofield, Damien Nevoltris, Jennifer Jackson, Katherine J. L. Jackson, Tim J. Peters, Melanie Burk, Jacqueline M. Matthews, Antony Basten, Christopher C. Goodnow, Sheryl van Nunen, Joanne H. Reed, and Daniel Christ, "Genetic and structural basis of the human anti—galactosyl antibody response," Proceedings of the National Academy of Sciences, 8 July 2022.

By GARVAN INSTITUTE OF MEDICAL RESEARCH 

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