After 11 September 2001, the USA was shaken by another terrorist attack in the same year, albeit on a much smaller scale: various newspapers and private individuals received letters containing anthrax spores, which can cause the fatal disease anthrax. Five persons fell victim to these assassination attacks. However, that was enough to increase the country’s feeling of insecurity.

The United States’ insecurity also spread to Europe. In autumn 2001 the emergency services in the canton of Zurich alone had to respond to 180 call-outs because of anthrax alarms. Fortunately the suspect powders turned out to be harmless. However, it took several days to prove their harmlessness. This is a worrying situation, since 5,000 to 10,000 inhaled anthrax spores are sufficient to have fatal consequences unless treatment is given within 24 to 48 hours.

Anthrose reveals anthrax

The diagnostic situation is now significantly better: Peter Seeberger’s research team at the ETH Laboratory for Organic Chemistry, together with the Swiss Tropical Institute and the University of Bern, has developed an antibody that specifically recognises the spores of Bacillus anthracis, the anthrax pathogen (1). The paper appeared on August, 17, in the scientific journal “Angewandte Chemie” (2).

US scientists succeeded only recently in identifying a tetrasaccharide called Anthrose on the surface of anthrax spores. This sugar seems to be present only on anthrax pathogens and not on related bacteria. Therefore Seeberger’s team tried to manufacture the sugar in larger quantities, and succeeded thanks to an automatic method for the preparation of oligosaccharides established in their laboratory (3).

A test within minutes

Next the researchers bonded the sugar to a transport protein. The reason for this was that a sufficiently large structure must be present for a successful immune response accompanied by the production of antibodies. The scientists now injected this compound into mice.

A sweet betrayer: The tetrasaccharide Anthrose (structure in photo at left), which is found on the surface of B. anthracis spores, was used for the selective detection of this biological weapon with a monoclonal antibody. Right: fluorescing antibodies on anthrax spores. (Photo: Peter Seeberger) large

From the animals that had been immunised in this way they were able to obtain monoclonal antibodies. These are antibodies that interact only with a specific structure – in the present case with anthrose. This specificity was demonstrated by experiments with the antibodies in which the latter reacted only with anthrax spores but not with closely related bacteria such as Bacillus thurigiensis or Bacillus cerius.

Peter Seeberger explains that “Anthrax spores can be detected within minutes by using this test method.” The researcher adds that the new antibody test, which has been patented by ETH, would be easy to integrate into the detection kits of the kind used by the US Post Office. “We are currently checking on its integration into commercial systems.”

A vaccine for humans is the next goal

However, the antibody is not only promising as a diagnosis tool. It could also be injected to block anthrax bacteria by what is called passive immunisation. “First of all, however, we want to test an active vaccination for humans,” says Seeberger, looking to the near future. In fact with his synthetically produced anthrose bonded to the transport protein he has already created the basis for a vaccine.

If this undertaking is successful, individuals vaccinated against anthrax could in the future open letters containing anthrax pathogens without any risk. Vaccination protection against this biological weapon would certainly be of interest to armed forces as well.