Sept. 23, 2005 -- An important family of anti-HIV drugs may boost the immune
Sept. 23, 2005 -- An important family of anti-HIV drugs may boost the immune systems of people not infected with the AIDS virus.
The drugs, called protease inhibitors, are specifically designed to attack a major HIV enzyme. But accumulating evidence suggests that they do much more. The drugs apparently increase production of T cells, a crucial component of the immune system.
T cells -- produced in the thymus -- are the kind of cell that HIV loves to infect. T cell numbers increase in people treated with AIDS drugs. That, nearly everyone thought, is because lowering the amount of HIV in the body allows a rebound in T cells.
Now there's evidence that protease inhibitors may do more than fight HIV. Mayo Clinic immunologists David McKean, PhD, and Andrew Badley, MD, led a team that looked at what happens to T cells when people who don't have HIV take AIDS drugs.
The researchers looked at seven adult health care workers who took the drugs because they'd had possible exposure to HIV. None of the health care workers became infected.
But five of the seven had a huge increase -- up to 1,000-fold -- in brand-new T cells. This seemed to be due to Viracept, a protease inhibitor they took in combination with a different kind of AIDS drug called Combivir. Neither of the two drugs that make up Combivir is thought to directly increase T cells.
"We think the protease inhibitors are responsible for these naive T cells," McKean tells WebMD. "There is no evidence the other antiviral drugs have any effect on the thymus."
Cancer Vaccine
What makes this finding exciting is that the new T cells did not turn around and attack the body. In mouse experiments the new cells appeared ready to fight disease. That could be a big help for elderly patients as people make fewer and fewer new T cells as they age.
"The ability of [AIDS drugs] to boost T-cell numbers may allow patients who normally don't respond to vaccines -- such as those with chronic disease, or the elderly -- to mount an effective immune response," Badley says in a news release.
Perhaps the most exciting part of the new findings is that AIDS drugs could provide an army of new T cells to fight cancer. McKean says cancer vaccines tend to fail because tumors suppress antitumor immune responses.
"If we can use [AIDS drugs] to increase the number of newly produced T cells in cancer patients, we can potentially improve the likelihood of getting a cancer vaccine to work," he says.
McKean and colleagues report their findings in the current issue of the journal AIDS.
