Scientists watch proteins move on surface of HIV virus in real-time

The research team, including co-lead author Dr. Scott Blanchard of Weill Cornell Medical College in New York, NY, says the discovery may shed light on how the HIV virus infects human immune cells, paving the way for strategies that prevent such infection.

"Making the movements of HIV visible so that we can follow, in real-time, how surface proteins on the virus behave will hopefully tell us what we need to know to prevent fusion with human cells - if you can prevent viral entry of HIV into im-mune cells, you have won," explains Dr. Blanchard.

In their study, Dr. Blanchard and colleagues describe how they created fluores-cent molecules, referred to as "beacons," and introduced them to the outer cov-ering of the HIV virus - called the "envelope."

They then modified a technique called single-molecule fluorescence resonance energy transfer (smFRET) imaging to watch two of the beacons.

This imaging method uses fluorescent light to measure the distance viral parti-cles travel. In this study, the team were able to measure distances - down to a billionth of an inch - between the two beacons, which lit-up in different colors. The team were then able to detect real-time shape-shifting of the virus as the two beacons moved.

Using this technology, the researchers were able to analyze the movements of envelope proteins - gp120 and gp41, known as "trimers" - on the surface of the HIV virus.

Such proteins are important in allowing the HIV virus to infect human cells that carry CD4 receptor proteins - the proteins that assist HIV in binding to a cell. The researchers explain that these proteins "open up like a flower" when CD4 is present, revealing a gp41 subunit.