They’re best known as carriers of nasty infections such as West Nile Virus, but it turns out that the blood-sucking insects may also possess something that could protect us from heart disease — or at least their spit does.
“Ticks are quite fascinating bugs since they need several sophisticated tools to circumvent and control our defense systems–[the] immune and coagulation systems,” says study author Tim Schuijt, of the Center for Experimental and Molecular Medicine at the University of Amsterdam. “They are slow-feeders, taking almost a week to complete their blood meal.”
To ensure a steady flow of blood for that meal, deer ticks spit when they bite an unsuspecting host, injecting a protein similar to a blood-thinning drug, that prevents the blood from clotting. That’s because a tick’s bite activates the host’s blood-clotting system. So the tick spits, drinks blood for about 15 minutes, then spits for another 15, and so on until it’s sated.
But studying the tick’s saliva compounds more closely, Schuijt and his colleagues learned something new about the blood clotting process that could prove useful in treating people. The tick’s spit blocks not one but two different clotting factors made by mammalian hosts — factor V and factor X. When they are blocked, they actually end up joining forces to generate another clotting compound that can then counteract the tick’s blood thinning efforts. Previously researchers were unaware that factor X was involved in coagulating blood.
Schuijt’s discovery began when he investigated how factor V interacted with factor X (called TIX-5, short for Tick Inhibitor of factor Xa towards factor V); initially, he was trying to figure why certain animals were unaffected by tick bites. Immunity to ticks, or tick resistance was identified as early as the 1930s, and since then scientists have discovered antibodies that animals made to ward off the tick’s blood-thinning proteins. Seven years ago, Schuijt helped to identify six of the tick’s salivary proteins that ‘tick immune’ rabbits easily recognized, and eliminated. During this process, he also discovered that one of the proteins inhibits the human coagulation system, and he named it TIX-5.
“It became more fascinating when we identified the exact mechanism of how TIX-5 was able to inhibit our coagulation system. By means of TIX-5–as a tool–we found that our coagulation system works differently than the textbooks currently say. TIX-5 is a unique inhibitor that specially prevents activation of factor Xa-mediated factor V activation,” says Schuijt.
That understanding could lead to the development of new anti-clotting drugs that might be useful in cases of heart disease or stroke, when blood flow is restricted. “TIX-5 could possibly be used–or be used as an inspiration to develop– a novel anticoagulant with less side effects as the current anticoagulants,” says Schuijt. And if that happens, we would have a tick to thank.
The study is published in the journal, Circulation.