Scientists at Johns Hopkins University and Hospital said their discovery of HIV?s cellular escape route could affect the way the virus is targeted by drugs.
Scientists learned relatively recently about exosomes ? an export system cells use to purge junk proteins and other “garbage” through the cell wall. Now Stephen Gould, professor of biological chemistry at Hopkins, says HIV uses this system to avoid killing the cell.
“You have two types of viruses. One rips the cell apart and kills it as its various particles fall out. Others assemble inside the cell, then pop off one by one in little sacks,” Gould said. In some diseases, the virus eventually runs the cell down until it dies, but HIV preserves its host, converting it into a viral factory.
His findings, published in the June issue of the Public Library of Science: Biology, counters prevailing beliefs that HIV and other retroviruses can leave and enter cells only by virus-specific mechanisms.
“Surprisingly, all that?s needed for a protein to get out of the cell in exosomes are the ability to clump together and attach to the cell?s membrane,” Gould said.
HIV and AIDS infect more than 1 million Americans, and the Centers for Disease Control and Prevention estimates another 40,000 are infected each year. In the Baltimore and Towson areas, that translates to 32.8 new infections for every 100,000 people, according to the Maryland AIDS Administration.
Gould?s team added chemicals to normal cells to force nearby proteins to clump. This was enough to get them sent out of the cell in exosomes. Artificially forcing naturally clumping proteins to the membrane also resulted in deportation.
Gould?s article speculates that cells may have developed exosomes specifically to get rid of clumped proteins, which are generally broken and useless.
However, just as retroviruses like HIV exploit other cell processes for their own ends, this article shows they rely on exosomes to get out of infected cells to infect new cells.
A major protein in HIV has properties that cells interpret as clumping against the cell wall, the article states.
“The virus is not able to escape the cell in any other way,” Gould said.
As such, drugs that interfere with exosome formation might be one way to inhibit HIV infections.
