National Institutes of Health (NIH) scientists found the mechanism involved in stabilising key HIV proteins and thereby concealing sites where some of the most powerful HIV neutralising antibodies bind.
Numerous spikes jut out of the surface of HIV, each containing a set of three identical, bulb-shaped proteins called gp120 that can be closed together or spread apart like the petals of a flower, researchers said.
Some of the most important sites targeted by HIV neutralising antibodies are hidden when the three gp120s, or the trimer, are closed, and the gp120 trimer remains closed until the virus binds to a cell, they said.
The researchers discovered that certain amino acids located on the gp120 protein undergo a process that stabilises the trimer in its closed position.
In this process, called sulfation, the amino acids acquire a sulfur atom surrounded by four oxygen atoms.
By either blocking or increasing sulfation of these amino acids, the researchers changed the sensitivity of the virus to different neutralising antibodies, indicating that the trimer was being either opened or closed.
The scientists suggest that if the synthesised gp120 widely used in HIV research were fully sulfated during manufacture, the resulting product would adopt a more true-to-life structure and more closely mirror the way the immune system sees unbound HIV.
This might help generate a more effective HIV vaccine, NIH researchers said.
They added that full sulfation of gp120 may enable scientists to crystallise the molecule more readily, which also could advance HIV vaccine design.