VIENNA -- For years, human immunodeficiency virus (HIV) researchers have shied away from the whole notion of a cure, largely because evidence showed the virus can persist even under intensive treatment.
But now, they are -- tentatively -- expressing a renewed interest in the idea.
That interest is sparked by clinical data showing an apparent cure in a single case and some technical advances that make it easier to track very low levels of HIV infection, experts said at the International AIDS Conference here.
But progress is hampered by lack of money for research in the field and by what one prominent researcher called "fundamental gaps" in the understanding of how HIV and the human body interact.
Nonetheless, researchers gathered here last week -- before the start of the AIDS conference -- for a two-day workshop called "Towards a Cure." Led by Nobel laureate Francoise Barre-Sinoussi, the workshop considered a host of questions, including:
What are the clinical implications of HIV persistence under treatment?
Where and how does HIV hide from the immune system and anti-HIV drugs?
How does HIV persist?
What are potential therapeutic interventions and how can they be evaluated?
There has been some study of those issues "but we can certainly do better," according to Barre-Sinoussi, who was one of the researchers involved in identifying the human immunodeficiency virus.
She noted that vaccine research -- which has been much in the news here -- is supported by international groups that co-ordinate the science and lobby for money. "There is no equivalent for research into remission or functional cure," Barre-Sinoussi said.
One thing that is clear is that current therapies can only control the virus, not eradicate it, according to Maureen Goodenow of the University of Florida. That's because the virus persists -- even when it is undetectable in plasma -- in "diverse" cells and physical locations.
These so-called "reservoirs" consist of cells that harbor the virus, but in which it is not actively replicating. One important question is whether it is even possible for current therapies to eradicate any of the reservoirs, Goodenow said.
So far, the evidence is weighted against that possibility, according to Dr. Frank Maldarelli of the National Cancer Institute. "All the drugs we have now available only affect active replication," he told reporters.
Controlling replication is enough to keep a patient alive and well, but won't have any effect on cells in which the virus is lying dormant, he said. So it's critical to know if the virus can piggyback on cells without replication, he said, since there's evidence that simple growth of such cells is enough to allow the virus to spread, even when it is not actively replicating.
Researchers have tried to "intensify" therapy -- adding drugs to a successful treatment regimen in an attempt to completely eliminate all traces of HIV -- but without success, Maldarelli said. The workshop was told that even in such circumstances, low levels of HIV viremia persist, he said.
One piece of data that has galvanized researchers is the recent case of a bone marrow transplant that appears to have cured a man of HIV.
The lead researcher in that case, Dr. Gero Hutter of Berlin's Charite-Medical University, reported at the workshop that the patient remains well and off antiretroviral drugs two years after the transplant, Maldarelli said.