New treatments for AIDS and other diseases may be possible in the future, thanks to research that sheds light on how HIV turns off the T-cells produced by the body to attack viruses.

Healthy individuals produce T-cells that attack viruses. In AIDS patients, T-cells don't work properly, but the reason has been elusive until now.

An international team of researchers led by Bruce Walker, MD, director of the Partners AIDS Research Center at Massachusetts General Hospital, learned that the AIDS virus causes a molecular switch, or pathway, to stop functioning, thereby preventing the T-cells from doing their jobs.

"The immune cells are there, but they have been turned off in persons with high viral loads," said Dr. Walker.

Blocking the switch restores some function to HIV-specific CD8 and CD4 T cells, the investigators learned.

The same pathway plays a role in other chronic viral infections, leading the researchers to speculate that in the future, doctors might be able to switch a person's immune system back on so it could combat not only HIV, but also cancer, Hepatitis C and other diseases.

The scientists' findings are slated for publication in the journal Nature. The University of KwaZulu-Natal in South Africa and other institutions participated in the groundbreaking research effort.

"One of the next questions we need to answer is whether we can turn [the immune system] back on for HIV-infected patients in a way that will benefit them without incurring serious side effects," said study co-first author Cheryl L. Day, PhD.

One major worry is that manipulating the immune system in such a fashion could spur too much activity, causing an autoimmune disease that could attack healthy cells. That possibility means that any research involving humans must be conducted with utmost caution, said Dr. Walker.