HIV appears to enlist the aid of nano-sized structures released by infected cells to infect new cells, according to a study by researchers at the National Institutes of Health.

Known as extracellular vesicles (EVs), these bubble-like structures are made by many kinds of cells and, under most circumstances, are thought to ferry molecules from one cell to another, providing a means of communication. NIH scientists discovered that cells infected with HIV appear to produce EVs that manipulate prospective host cells to pass infection to other cells. The study appears in Scientific Reports.

“If we remove extracellular vesicles from HIV laboratory preparations, we also reduce HIV infection of human tissues in culture,” said the study’s senior author Leonid Margolis, Ph.D., of the Section of Intercellular Interactions at NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “Therapies that target extracellular vesicles could potentially hinder the ability of the virus to infect new cells.”

EVs from HIV-infected cells are believed to form in much the same way as a new virus forms. Like a bulge on an inner tube, a structure forms at the surface of the cell’s outer membrane. Eventually, the part of the membrane bubble nearest the cell surface pinches off, forming a discrete sphere, separate from the cell. In the case of the virus, the sphere contains HIV’s hereditary material, RNA. EVs typically contain little, if any, HIV RNA, and so cannot infect a cell.

In the current study, the NICHD researchers isolated HIV and EVs from infected cultures, separated the two, and then tested the ability of HIV to infect new cultures — both in the presence of EVs and on its own.

Because EVs are extremely tiny and difficult to sort with conventional techniques, the researchers devised a new technology to isolate and study them.

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