Can AIDS be cured?
It has long been a taboo to use the C-word when discussing the response to the pandemic, but scientists at the International AIDS Conference in Vienna are seriously discussing the idea that the human immunodeficiency virus can be eliminated from the body, or at least battered into quasi-permanent remission.
"Vienna will not be the conference to announce a cure. But we should not continue to accept that HIV is a disease which commits patients to life-long treatment," said Sharon Lewin, a physician in the infectious diseases unit of the Alfred Hospital in Melbourne, Australia.
While much effort has been invested in getting people with HIV-AIDS on a course of treatment, antiretroviral drugs essentially have to be taken for life.
If they are stopped, illness returns with a vengeance, meaning that the cost of controlling the epidemic is astronomical, while the cost of non-treatment is even higher - a Catch-22 of global proportions.
"The need for a cure is more urgent in 2010 than ever before," Dr. Lewin told conference delegates, who applauded vigorously in agreement.
What scientists would like to do is find a way to take the treatment up a notch so that replication of the AIDS virus is not just dampened but permanently stopped.
There are two major avenues being explored:
• A functional cure, where the virus is permanently suppressed so drugs are no longer needed; this is similar to a cancer being in remission;
• A sterilizing cure that would eliminate HIV from the body entirely; this is similar to a cancer that is cured with a bone marrow transplant.
While the approaches are straightforward, there are a number of hurdles.
The most obvious is that HIV is wily. It hides in reservoirs, allowing the virus to pounce anew once treatment stops. Worse, researchers aren't quite sure where those reservoirs are.
Just as significant is that the virus can silently establish itself in CD4 and T-cells, central components of the immune system. As a result, all the HIV virus in the body is not killed, even in patients who seem to be HIV-free.
"I think it was irresponsible to talk about a cure when we had no drugs. But now it's legitimate to talk about it now," said Mark Wainberg, head of the AIDS Centre at McGill University in Montreal.
As scientific knowledge increases, confidence is growing that the challenges can be met, Dr. Wainberg said.
There are reasons for optimism.
The treatment regime, known as highly active antiretroviral treatment, or HAART, is now being used by 5.2 million people worldwide. The drugs have become cheaper, easier to use and less toxic.
They have also extended the life expectancy of HIV-positive people by more than 13 years on average. For most people on treatment, HIV-AIDS is now a chronic illness, not the short-term death sentence it once was.
One spectacular scientific breakthrough - and many less noticeable advances in labs around the world - have fuelled the cure talk.
In 2008, researchers revealed that a 42-year-old German man had been cured of AIDS; he has been off drugs since and remains in good health, according to his doctors.
The case is unusual but informative. "It reminds us that HIV is an infection of the immune system," said Frank Maldarelli, head of the HIV Resistance Program at the U.S. National Institutes of Health in Bethesda, Md.
In addition to being HIV-positive, the patient developed leukemia. His treatment included a stem-cell transplant, which required that his immune system first be wiped out with drugs and radiation. Then, it turned out that the donor of his bone marrow had a rare mutation, known as Delta 32, that resulted in his white blood cells lacking the receptors that allow HIV to invade the immune system. The transplant recipient inherited that mutation and his HIV seems to have disappeared.
The problem, Dr. Maldarelli said, is that these circumstances are virtually impossible to replicate and, besides, "wholesale replacement of the immune system is not a practical approach."
Indeed, no one realistically believes that gene therapy could be done on the 33.4 million people in the world living with HIV-AIDS today. Yet, each small advance bolsters the hope that the number of new infections (2.7 million a year) can be slowed and the number of AIDS-related deaths (two million annually) can be reduced.
"There is a growing sense within the scientific community that the search for a cure for AIDS is ripe for a concerted research effort," said Robert Siliciano, a researcher at Johns Hopkins University in Baltimore, Md.
Françoise Barré-Sinoussi, the 2008 Nobel laureate in medicine for her co-discovery of the AIDS virus and president-elect of the International AIDS Society, is equally bullish. "The science in this area is evolving rapidly," she said. "There is a strong need for continued investment in research."
As tantalizing as the prospect of a cure is, scientists caution that it should not take precedence over the search for a vaccine, the quest for universal treatment with antiretrovirals, the development of microbicides and other public-health measures like the promotion of circumcision and the distribution of condoms.
"A cure is still the Holy Grail of treatment research, just as a vaccine is the Holy Grail of prevention research," Dr. Wainberg said.
"But, in the meantime, there is still a lot of practical stuff we need to do every day."
André Picard