The researchers, led by Dr. Walther Mothes at Yale, have made movies of viral activity within cells that help explain why cell-to-cell transmission is so efficient, and provide potential targets for a new generation of AIDS drugs.
"Cell-to-cell transmission is a thousand times more efficient, which is why diseases such as AIDS are so successful and so deadly. And because the retroviruses are already in cells, they are out of reach of the immune system," said Mothes.
By using imaging technology that can track individual particles of virus in real time, the researchers discovered that infected cells could specifically produce viruses at the point of contact between cells.
They also observed that ten times more of these particles are found at these cellular poles than elsewhere at the surface of cells.
Scientists claimed that the ability of infected cells to specifically produce viruses only at cell-cell interfaces explains how viruses spread so efficiently.
The researchers also identified a possible weakness in the transmission chain.
The team found that viruses express a sticky protein that docks with uninfected cells and then attracts viral assembly to these sites.
If this adhesion molecule lacked a "cytoplasmic tail," then it would mean that the viral particles did not assemble at the jumping off point between cells.
Mothes is expecting that many more such targets will be identified as scientists work out the mechanics of cell-to-cell transmission.
"We are just opening the door to this whole process. It is a black box, and many, many cellular factors have to be involved in making this happen. Our hope is that somewhere down the road we will have a completely new anti-viral strategy based on targeting cell-to-cell transmission," said Mothes.
The study has been reported in the open access journal PLoS Biology.