Feb 6, 2007
By Will Dunham
WASHINGTON (Reuters) - A naturally occurring molecule saves vital immune system cells from cellular suicide during the onslaught of the AIDS virus and might help keep the body's natural defenses working in HIV-infected people, a study found.
The findings represent a potential new avenue to fight the effects of the human immunodeficiency virus, HIV, according to U.S. National Institutes of Health scientists whose work was published on Monday in the Proceedings of the National Academy of Sciences.
Dr. Paolo Lusso and colleagues at the NIH's National Institute of Allergy and Infectious Diseases looked at the role played by interleukin 7 in averting the death of T cells, a kind of white blood cell important to the immune system.
Interleukin 7 is a substance important in maintaining proper functioning of the immune system.
AIDS has killed more than 25 million people since it was first recognized in 1981. About 40 million people now live with HIV, with sub-Saharan Africa hardest hit.
Lusso expressed "reasonable optimism" that treatment involving interleukin 7 may benefit people with AIDS, a disease for which no cure exists.
"I don't think one solution will be applicable to all the patients. It's possible that IL-7 (interleukin 7) may benefit some patients and do nothing in other cases," Lusso said in an interview.
"But I think we are moving in the right direction because we are starting to appreciate that antiretroviral therapy alone (existing AIDS drug treatment) is not sufficient to bring back a full immune competence, and we are starting to identify at least some strategies that may work."
IMMUNE SYSTEM TARGETED
An insidious aspect of HIV is that the virus attacks the body's natural defenses -- the immune system.
In assaulting the immune system, HIV hides inside certain T cells. These cells, as the infection progresses, commit cellular suicide -- called apoptosis -- undermining the body's ability to combat infections and certain cancers. In fact, the virus manages to induce the suicide of many more T cells than it directly infects.
The researchers, who also included Dr. Lia Vassena and NIAID Director Dr. Anthony Fauci, used blood samples from 24 HIV-infected people. They added interleukin 7 to the blood samples and then gauged the survival of T cells.
The actual patients themselves were not treated with interleukin 7.
The samples with interleukin 7 displayed lower levels of T cell death. The benefits differed from sample to sample based on the person's stage of infection, the study found.
The researchers believe interleukin 7 potentially could be used alongside existing AIDS drugs to bolster the immune system.
Lusso noted that existing AIDS drugs can keep the virus at bay for years, but damage to the immune system commonly persists even after years of such treatment.
Scientists want to find new ways to remedy these immune defects, with the aim to make the immune system functional even in HIV-infected people.
Lusso said apoptosis may be a major mechanism through which T cells die in AIDS. The new study is important, he said, in that it identifies how interleukin 7 may help -- by preventing these cellular suicides.
He said the next step is a study in which monkeys with the simian equivalent of HIV are given interleukin 7 to see if it blocks immune system dysfunction and immune cell depletion.