The virus that causes AIDS can hide in the bone marrow, avoiding drugs and later awakening to cause illness, according to new research that could point the way to better treatments.

Finding that hideout is a first step, but years of research lie ahead.

'I don't know how many people realize that, although the drugs have reduced mortality, we still have a long way to go.'—Dr. Kathleen Collins

Dr. Kathleen Collins of the University of Michigan and her colleagues report in this week's edition of the journal Nature Medicine that the HIV virus can infect long-lived bone marrow cells that eventually convert into blood cells.

The virus is dormant in the bone marrow cells, she said, but when those progenitor cells develop into blood cells, it can be reactivated and cause renewed infection. The virus kills the new blood cells and then moves on to infect other cells, Collins said.

"If we're ever going to be able to find a way to get rid of the cells, the first step is to understand" where a latent infection can continue, she said.

In recent years, drugs have reduced AIDS deaths sharply, but patients need to keep taking the medicines for life or the infection comes back. That's an indication that while the drugs battle the active virus, some of the disease remains hidden away to flare up once the therapy is stopped.

One hideout was found earlier in blood cells called macrophages. Another pool was discovered in memory T-cells, and research began on attacking those.

But those couldn't account for all the HIV virus still circulating, Collins said, showing there were more locations to check out and leading her to study the blood cell progenitors.

Finding these sources of infection is important because eliminating them would be a cure that allows AIDS patients to stop taking drugs after their infection ends. That's critical in countries where the treatment is hard to afford and deliver.

"I don't know how many people realize that, although the drugs have reduced mortality, we still have a long way to go," Collins said in a phone interview. "That is mainly because we can't stop the drugs — people have to take [them] for a lifetime."

The long-term goal is to develop ways to eradicate HIV or limit the lifelong need for medication. If the approach works, its safety also need to be shown.

The research was funded by the National Institutes of Health, Burroughs Wellcome Foundation, University of Michigan, Rackham Predoctoral Fellowship, National Science Foundation and a Bernard Maas Fellowship.