A diagram of a HIV virion: The purple and green units are docking proteins in the lipid membrane. The dark blue layer is the protective capsid, while the yellow units are the genetic material of the virus in the form of RNA. The red spots denote the enzyme reverse transcriptase.
Credit: U.S. National Institutes of Health
LONDON: A common blood molecule has been found to confer unusual resistance against HIV on a very small proportion of the population, now experts want to use it as a weapon against infection.
The molecule, a carbohydrate called Pk, is found sticking out of the surface of red and white blood cells. A lucky few – one in every million people – have abnormally high levels of the protective substance, giving them a natural advantage against HIV.
Pk in people
However, artificially bumping up levels of this molecule in the blood might also increase resistance to HIV, claims study co-author Martin L. Olsson, a clinical geneticist from Lund University in Sweden. The research is published in the journal Blood.
Almost everybody has some Pk in their blood, but amounts vary widely. Among Caucasians, 80 per cent have fairly high levels, while 20 per cent have low levels. Just a tiny proportion lie at the extremes, with one in a million having abnormally high levels, and 5 to 15 in every million, having no Pk at all.
To test how Pk levels affect HIV risk, Olsson's team took blood samples from the two extremes and tried to infect white blood cells with different strains of the virus.
They found that the blood with no Pk was 10 to 1,000 times more likely to get infected with the deadly virus, than high Pk blood. "That is quite a dramatic difference," Olsson told Cosmos Online. "It was very clear that it had a blocking or resistant effect."
HIV blocker
After this, the scientists added the molecule to white blood cells lacking Pk via tiny organic spheres called liposomes. They found that this increased their resistance by around 50 per cent.
The team also genetically altered blood cells to produce higher and lower levels of Pk. As expected, more Pk meant more resistance, while less Pk left cells more vulnerable to infection.
Pk works by blocking HIV's ordinary route into the cells, said study co-author Don Branch, an immunologist from Canadian Blood Services in Ottawa.
Normally, HIV has to bind with a chemokine receptor on the cell surface before it can get inside and infect it. However, Pk sits very close to this receptor, stopping HIV from binding properly, he added.
The next stage will be to use Pk for tests to predict people's risk of contracting HIV, and also to create new drugs to help protect against infection. In fact, the researchers are already looking at Pk-like molecules that could one day be used to treat the condition.
"All of a sudden we have a completely new target, and this could lead to a new toolbox [for treating HIV]," said Olsson.
Eva Maria Fenyö, a virologist from the University of Lund who was not involved in the study, believes it takes an important step forward. "[The study] very convincingly shows that Pk plays a role in susceptibility to HIV infection", she said.
