genetic block. TRIM5- a disrupts the shedding of HIV capsid (purple) after the virus enters the cell, preventing the release of its genetic material.
AIDS researchers have long known that HIV can not copy in monkeys, but they had only a vague idea why. Now an essential part of the puzzle fell into place :. monkey cells make a protein that specifically derail HIV
Although HIV can easily enter in monkey cells, the virus must convert its RNA into DNA before weaving themselves into the chromosomes of the host and copy itself. The new protein, described in Feb. 26 issue of Nature , blocks the transcription of DNA into RNA, the same part of the life cycle of the virus that AZT and several other anti-HIV drugs disrupt .
virologist Joseph Sodroski of the Dana-Farber Cancer Institute in Boston and colleagues found the protein by making a wide variety of monkey genes in human cell clones they knew could support growth HIV. Two clones, they engineered has become resistant to HIV, and they had one monkey factor in common: the gene for a protein called TRIM5- a . Subsequent experiments showed that the target protein of the capsid of HIV, a protein material that protects the viral genetic material and "after" uncoats the virus enters a cell, a key step in the transformation of DNA into RNA. By an unknown mechanism, TRIM5- a seems to disturb the smooth undressing of the capsid.
Translating the results of basic research into drugs is still a long shot, but Sodroski began pursuing the possibility. "We have a very clear example of something extremely potent and specific," he said. Sodroski also began to consider whether his laboratory can design an HIV able to bypass the monkey TRIM5- a , which could provide a new extremely valuable animal model. At present, the main monkey model used by researchers of AIDS is based on infecting rhesus macaques with SIV, a simian cousin of HIV, or a hybrid of SIV-HIV. Most anti-HIV drugs have little activity against both viruses and AIDS drugs and vaccines developers would favor a test virus which is more like the human version.
Nearly a dozen laboratories have hunted for the agent that counteracts HIV in monkeys, and some close competitors swallow hard as they applaud. "I'm sick as a dog because it is a beautiful piece of work," says Paul Bieniasz Center Aaron Diamond AIDS Research in New York City. "If it can be harnessed to the fight against HIV is uncertain at this time, but even if it is just a new discovery in fundamental research, it is a completely new system of antiviral cellular activity."
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