Blocking HIV's 'grappling hook'

Viruses clustered near the surface of a cell

Doctors may get a potentially potent HIV-inhibiting drug in tablet form after a breakthrough by US scientists.

The researchers have found a tiny protein molecule that locks on to the virus and stops it working a "harpoon-like" component which pushes into the cell it wants to infect.

We greatly need new targets so that we can make more active combination therapies

Prof Jonathan Weber

Unless the virus can lock its membrane against the cell membrane in this way, it cannot attack the cell and replicate.

The journal Science reports how Dr Peter Kim, from the Howard Hughes Medical Institute and the Whitehead Institute for Biomedical Research in the US, developed the protein, called 5-Helix.

There already exists another molecule developed to do the same job, and this is already being tested in clinical trials across the world.

However, because it is a relatively large molecule, it can only be taken via infusion into the bloodstream, whereas the much smaller molecule synthesised by Dr Kim can be put into a tablet.

Exciting discovery

This makes is much cheaper and easier for doctors, not to mention their patients, to incorporate as part of a combination therapy against HIV. Laboratory tests suggest that the new molecule is stable, and likely to work well on a variety of common HIV strains.

Pills are cheaper and easier for patients than infusions

Dr Kim said: "I think we are only a few steps away from testing in monkeys, for which good models of HIV infection exist, to determine whether 5-Helix or a derivative can reduce the viral load in the bloodstream."

British scientists say they are excited by the potential offered by the discovery.

Professor Jonathan Weber, a professor in communicable diseases at Imperial College, London, said that while it had yet to be proved safe and effective, it could represent a major advance.

He told BBC News Online: "We greatly need new targets so that we can make more active combination therapies.

"HIV gets into the cell by this spring-loaded mechanism - this is how most viruses enter the cell. Drugs which inhibit this process could be highly useful."

The fact that other viruses work in very similar ways offers the prospect of similar molecules to fight infections such as influenza, and RSV, a virus which causes respiratory infections.