The tick is devilishly good at sucking our blood in peace. In order to pass unnoticed when they bite us, ticks produce small proteins called evasins in their saliva. The latter trap chemokines, other proteins in the cytokine family that trigger an inflammatory response when the body is attacked. Their main function is to attract leukocytes to the site of the injury. While this inflammatory response is useful in some cases, it can also get carried away and cause organ damage, as we saw in the Covid-19 epidemic.
The evasins with anti-inflammatory properties
For several years, evasins have therefore interested researchers as a possible treatment to inhibit inflammation. Previous studies in mice have shown that evasins from the tick have excellent inflammatory properties against pulmonary fibrosis or colitis (an inflammation of the lining of the colon). The problem is that these molecules are particularly difficult to isolate, stabilize, and produce in large quantities. “In the tick’s saliva, the evasins are mixed with a large number of other molecules, which makes them difficult to test or reproduce,” attests Charlotte Franck, Belgian doctoral student at the University of Sydney. This scientist is the main author of a new study published in the PNAS journal, which succeeded for the first time in chemically synthesizing evasins in order to improve their efficiency. Rather than isolating the evasins in the tick saliva, the researchers started from scratch by chemically reconstituting the molecule. They then modified these evasins by attaching a sulfate group to them, which increases their ability to bind to chemokines and their inhibitory capacity. This change also improves their stability, which opens the way for industrial production of anti-inflammatory drugs. A treatment which could also concern Covid-19, since the chemokines are factors of pulmonary inflammation in this disease. Except that it will still take several years before having a marketable drug.
A drug based on tick saliva already in the clinical trial phase
The evasines are not the only molecules produced by the tick in its saliva. Akari Therapeutics, a London startup, has developed a tick saliva medication called Nomacopan. The latter inhibits the C5 gene, which plays a key role in the inflammatory response, as well as leukotriene B4, a chemical messenger responsible for recruiting pro-inflammatory cells. The company has just released the preliminary results of a clinical trial of Nomacopan on a serious autoimmune skin disease called bullous pemphigoid, showing the effectiveness of the treatment in seven out of nine cases. The drug is also being evaluated as a treatment for atopic keratoconjunctivitis (a chronic inflammatory eye disease), and thrombotic microangiopathy (which affects small blood vessels). A painkiller in snake venom, a gel based on spider venom against erectile dysfunction or a treatment against psoriasis from the ant …, would “harmful” animals finally be our friends?
