Researchers turn to tick spit to shut down our immune systems

A traditional foe could become a friend to those with a rare blood disorder

When ticks bite humans, they inject us with a substance that keeps them disguised from our immune systems. This lets them hang on to us and feed for up to 10 days without getting attacked by our bodies' defences. While this strategy certainly serves the tick — and not the humans — very well, researchers may soon be turning the tables and employing a substance in tick saliva to help people battle damaging, and potentially deadly, autoimmune diseases.

The research into tick spit was carried out by scientists at England's University of Oxford and Australia's Monash University. They discovered that the substance with which ticks inject humans shuts down the same part of our immune system as a popular, but expensive, drug called Eculizumab, which is sold under the name Soliris.

Soliris is used to combat two blood disorders in which the immune system attacks and kills blood cells: Paroxysmal nocturnal hemoglobinuria (PNH) and atypical haemolytic-uremic syndrome (aHUS). By shutting down a portion of the immune system, the drug can stop the life-threatening attack of the disease.

To map the pathways of both Soliris and the tick saliva, the researchers used super-strong microscopes at Monash's centre for cryo-electron microscopy along with a technique called X-ray crystallography, which lets scientists study the structure of crystalline molecules based on the X-ray beams that bounce off of them.

Their observations led them to the conclusion that the proteins in the tick saliva work the same to stop the out-of-control immune response as Soliris. But the saliva had two distinct advantages. First, it could be much cheaper to produce.

"Soliris is one of the most expensive drugs in the world, costing up to $500,000 per patient per year," says Associate Professor Hans Elmlund, co-lead author of a paper detailing the findings that was published Tuesday in the journal Nature Structural and Molecular Biology.

Second, the saliva might help a broader spectrum of patients because it has a different molecular makeup than Soliris. That means it could help those afflicted with PNH who've built up a resistance to the pharmaceutical.

Co-author Susana Lea, a professor at Oxford, also added that the findings could have implications for other diseases.

"Blood poisoning, or sepsis, kills over six million people a year," she says. "Affected individuals often die because of a powerful, but ultimately catastrophic, immune over-reaction called 'cytokine storm.' Our team hopes that the tick-related proteins may one day be of use in controlling cytokine storm in order to lessen mortality in conditions such as sepsis."



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