The particles are coated with antibodies to a particular virus, so they will form clumps that should be visible on conventional body scans if that virus is present.

The team working on the technology, from the Harvard Medical School's Center for Molecular Imaging Research in Charlestown, Massachusetts, have already managed to detect viruses in body fluids and tissue samples. They hope to be able to detect viruses in patients' bodies within a couple of years.

Much of the technology has already been tested in humans, so the scientists are confident that it will be safe.

Scans revealing where virus populations are - HIV, for example, tends to concentrate in the lymph nodes - could help doctors improve treatments. And a scan could reveal whether viruses used in gene therapy to ferry new DNA into patients have actually reached the parts of the body they are intended for- and in sufficient numbers to do any good (Journal of the American Chemical Society, DOI: 10.1021/ ja036409g).

Usually, viruses can only be detected indirectly, by capturing and amplifying viral DNA through the PCR technique, which takes about two hours. "It's cumbersome, takes time, gives you false positives and negatives, and only detects fragments of the virus," says Manuel Perez, head of the team developing the new technique - which gives an answer in half the time.

It relies on particles 50 nanometres wide. They have a core of iron oxide and a coating of dextran, a sugar to which antibodies stick easily. A top coat of antibodies to the virus under investigation is added, and the particles are ready for use.

In lab tests, the nanoparticles have been added to samples of body fluids; in patients, they would simply be injected.

If live viruses are present, they stick to the antibodies on the nanoparticles, forming a large cluster of particles w
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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-207-331-2751
New Scientist
20-Aug-2003