Hopes for an AIDS Cure Remain Alive
Friday, January 5, 2007; 12:00 AM
THURSDAY, Jan. 4 (HealthDay News) -- In the hide-and-seek game played out between scientists and HIV over the last 25 years, the virus has so far been winning.
"All of the drugs that we have now are specific antiretroviral agents that inhibit some step in the virus' life cycle, so they hit HIV only when it is replicating," explained researcher Paul Bieniasz, an associate professor at the Aaron Diamond AIDS Research Center in New York City.
That strategy has brought many infected patients long-term health.
"But there's always a small but significant population of virus present in infected individuals that is not replicating," Bieniasz said.
For patients on effective drug therapy, that means HIV remains dormant in tissues at levels that are undetectable by standard tests.
These tiny reservoirs of "latent" HIV lie curled up as bits of foreign DNA buried deep within the nucleus of cells. Like a tiny time bomb, this dormant virus may stay sleeping for years. On the other hand, it may also switch over to replicating status and re-start the deadly progression to AIDS.
"It's a tricky virus, and latency is an excellent strategy for HIV," said Dr. Rowena Johnston, director of basic research at the Foundation for AIDS Research (amfAR). "If the virus is latent, not only is antiretroviral therapy not going to get at it, but it's also impossible for the immune system to target it, too."
Latent virus is the major reason why scientists have failed to find a cure for HIV/AIDS. According to Bieniasz, latent virus has no real "hook" for drugs to latch onto. And because latent HIV lies deep within the nucleus, any drug that could attack it might prove far too toxic to healthy cells.
But that isn't stopping researchers from pursuing a solution to the problem.
"At amfAR, we like to think that if we haven't proven that it's impossible, then we're not doing our job if we don't go after it," Johnston said.
In fact, amfAR is funding the work of Bieniasz' lab, where researchers are creating artificial pools of latent virus in cell cultures. They are using these cultures to test the effects of thousands of compounds -- watching to see if any particular molecule pushes latent HIV into an active, replicating state.
"It's thought that one strategy to eradicate HIV and effectively cure people is to make these latent viruses replicate," Bieniasz said. "Because once they replicate, you can then hit them with existing antiretroviral drugs."