A new weapon against tuberculosis?
Tuberculosis is an extremely insidious disease. The pathogen Mycobacterium tuberculosis can rest undetected many years in the human body, and infected people show no symptoms – until the disease suddenly breaks out. Worldwide, the number of deaths related to tuberculosis amounts to 2 million per year, eight million new infections occur annually. Dangerous centers of infection are, for instance, third-world countries or prisons in countries of the former Soviet Union. In some of the prisons, one hundred percent of the inmates carry the pathogen. Another serious problem is the increasing resistance of tuberculosis-pathogens against antibiotics.
Therefore, next to prevention in the affected countries, the search for new active agents against Mycobacterium tuberculosis has top priority. Funded by the German Ministry of Science and Education, a systematic search for such substances has begun. In the course of this project, scientists around Jens Peter von Kries at the so-called Screening Unit of the Berlin-based Forschungsinstitut für Molekulare Pharmakologie (FMP) made a surprising discovery: They identified a promising agent that inhibits the growth of tuberculosis bacteria. First tests at the cooperating Max Planck Institute for Infection Biology in Berlin showed the effectiveness of the substance in living tissue. "The substance that we discovered attacks the pathogens within their host cells", says Dr. von Kries. These host cells are part of the human immune system and form the first wall of defense agains the disease. In those so-called macrophages the tuberculosis pathogens remain undetected and grow, at the same time blocking an effective response of the immune system.
Currently, the scientists are filing a patent. Thus, Jens Peter von Kries does not want to disclose further details. He only says: "Our substance has already been clinically tested for other purposes. What’s new is the fact that it inhibits the growth of Mycobacterium tuberkulosis." The scientist adds: "Many people encounter the substance in their every-day life."
But how did the researchers came across this substance? To explain that, the head of the Screening Unit expands on the topic. "Screening with high-throughput methods is common practice for the pharmaceutical industry", says Dr. von Kries. Automated detection systems are screening thousands of substances, always looking for a clue to a well defined question. That may concern a certain pathway in molecular reactions which is already known. Using multiple procedures, researchers can find out whether there are other substances that cause similar reactions. "In academic research this procedure is a novelty", says von Kries. He established, together with colleagues from other institutes, the Screening Unit at the FMP, and the laboratory is involved in the search for active agents against tuberculosis pathogens funded by the German Ministry of Science and Education. The project is coordinated by Dr. Matthias Wilmanns (European Molecular Biology Laboratory in Hamburg)
One way to investigate such agents is called absorption spektroscopy. This method allows researchers to compare certain spectral lines of active substances that are well known to spectra of other substances. Spectral lines emerge when light of a defined wave length hits a sample and is then detected by a special camera. "If we find similar patterns we start to look more closely at the samples", says von Kries. Using this method, he obtained sixteen or seventeen hits out of 20,000 samples. "I selected four of those hits and gave the substances to our partners at Max Planck Institute for Infection Biology", says von Kries. One of the samples was actually effective against tuberculosis bacteria. Jens Peter of Kries: "That was quite unexpected, it was like winning the lottery."
The systematic search had concentrated entirely on a certain basic mechanism in cells. "This mechanism is part of the signal transduction from the outside into the cell and further into the nucleus", explains von Kries. In signal transduction, encymes play an important role. There are known substances that interfere with this chemical pathway and stop signal transduction. The team of the Screening Unit at FMP used two of these substances as reference material and compared the spectra to other materials via absorption spectroscopy.
"In our next screenings we will continue to take a closer look at signal transduction", says von Kries. For this, the Screening Unit is supported by Caliper Life Sciences of Rüsselsheim, Germany. The company supported the FMP with brand-new equipment. The automated screening machine can examine up to 30,000 samples per day using modern lab-on-a-chip technology. The robot offers several advantages. One is the high throughput, a second one is the fact that "the robot of Caliper examines enzymes on a substrate which closely matches the natural environment of the cell", says Jens Peter von Kries. He adds: "Thus, the results will be more accurate than with other screening methods." The researchers at the Screening Unit hope to identify even weak substances that show only small effects. Such potential agents would remain undetected in conventional screening procedures. By identifying such substances, whole new classes of active agents could be discovered and possibly be of use for producing new medicaments with, for instance, less side effects.
Core of the Caliper Screening-robot is a chip made of quartz, roughly the size of a hand, with twelve tiny reaction canals (see also press release from May 6, 2005 (in German): www.fv-berlin.de/pm_archiv/2005/19-wirkstoffe.htm ). Just recently, the final adjustments in the FMP laboratory were made so that the Screening-robot can start its work. With this machine, FMP will be the first scientific institute worldwide that makes use of such a modern Lab-on-a-Chip technology. "Of course I hope to produce further hits with the new equipment", says von Kries, "however, I doubt that we will win the lottery each week."
Dr. Björn Maul | alfa