Medicine from a Tick Bite

The tiny attacker lurks in a clump of grass, silent and nearly invisible. Only when a deer, a dog, or even a person brushes through the grass does the tick spring into action. It needs its meal of blood to survive, and the actual battle between parasite and host begins the moment the tick bites into its victim. It is vital that the tick remains unnoticed through all of this. We must not feel its bite; otherwise we would scratch and brush the pest off. The puncture must not become inflamed, and the victim’s blood must not clot. Humans and animals, on the other hand, have an entire arsenal of signal substances and immune cells for warding off parasites. That the tick can win is due to ever-increasingly sophisticated counterstrategies that have evolved over millions of years to deactivate this immune defense.

However, it has been discovered that the hated parasites could make a beneficial contribution to our health: It may be possible to model new medicines after the anti-inflammatory substances that a tick injects into the blood of its victims. A team of scientists at Merck Serono has succeeded in identifying and analyzing three of the tick proteins. This work could lead to the development of active ingredients that could be used to treat severe diseases of the immune system, such as inflammatory joint or bowel diseases or even the dreaded lupus erythematosus. With this disease, the immune system attacks the body’s own tissue for reasons that are still unexplained. The consequences are severe skin rashes, joint pain and inflammation of numerous organs.

“I find ticks to be fascinating creatures; they have been around since the time of the dinosaurs,” says Christine Power, molecular biologist. She is standing in a laboratory at the Merck Serono Research Center in Geneva, Switzerland. The futuristic building is built entirely of glass and steel struts. Its well-lit laboratories and offices line a giant, glass-enclosed interior courtyard. The width of the space seems to literally conjure up audacious projects and thoughts. For Christine Power, however, this is her everyday environment—she only has eyes for the current experiment.

A young scientist is looking through a microscope at a petri dish in which a transparent layer of cells is growing. The cells produce tick proteins—evasins, to be precise. These substances first gave cause for hope around eight years ago when Power and her colleague, Amanda Proudfoot, discovered an extremely interesting, unique characteristic of tick saliva. Ticks are capable of deactivating the chemokines of the human immune system, thus more or less turning off the alarm system that normally triggers inflammation.

“We had been looking for a way to inhibit chemokines for years,” recalls Amanda Proudfoot. Chemokines are the messenger substances in the human body that attract the defense cells in the case of an infection. The two scientists contacted a colleague in Brazil, who works with brown dog ticks. It was here that they obtained what they were hoping to study: one milliliter of tick saliva, spit out by a total of 50 of the tiny creatures. They also obtained specimens of salivary glands before beginning a research project that would last for years. The researchers did indeed find saliva that bond to specific human chemokines. From the salivary glands they were able to isolate the genetic material containing the instructions for assembling all of the proteins. They used a sophisticated screening method to examine millions of DNA fragments before they scored their first big hit: the genetic information for one of the anti-inflammatory tick proteins. Once this step has been accomplished, molecular biologists can implant the DNA building blocks into cells at will, and the cells produce tick proteins in petri dishes.