A natural ingredient of human blood has been shown to block HIV, raising hopes of a new class of drugs to treat infection with the virus.

The molecule works in a way different to current antiretroviral therapies, and so could be a new line of attack. Researchers found its potency could be boosted by making tiny changes to its chemical structure. It also worked against drug resistant HIV strains.

Antiretroviral drugs have played a key role in helping to keep the majority of people with HIV who take them alive. However, HIV has the ability to modify its structure, and there are concerns that many of the major drugs currently in use will become increasingly ineffective.

Many molecules in the blood have been thought to have some sort of inhibitory effect on HIV, but it has not been clear which are significant.

The researchers, at the University of Ulm, used state-of-the-art technology to assess the anti-HIV impact of more than one million blood proteins. They found fragments of the key molecule, which they call virus-inhibitory peptide (VIRIP), are relatively abundant.

Tweaks to its amino acid components boosted its anti-HIV potency by two orders of magnitude. Tests also showed that some derivatives of the molecule are highly stable in human blood plasma, and non-toxic even at very high concentrations.

A synthetic version of VIRIP also proved effective at blocking HIV, excluding the possibility that some other factor was responsible. VIRIP targets a sugar molecule which HIV uses to infect a host cell.

Source: BBC News, 20/APR/07