Activating resting immune cells
Many researchers believe the best hope for eradicating HIV infection lies in combining antiretroviral treatment with drugs that flush HIV from its hiding places. The idea is to force resting CD4 cells to become active, whereupon they will start producing new HIV particles. The activated cells should soon die or be destroyed by the immune system, and the antiretroviral medication should mop up the released HIV.
Early attempts to employ this technique used interleukin-2 (also known as IL-2 or by the brand name Proleukin). This chemical messenger tells the body to create more CD4 cells and to activate resting cells. Researchers who gave interleukin-2 together with antiretroviral treatment discovered they could no longer find any infected resting CD4 cells. But interleukin-2 failed to clear all of the HIV; as soon as the patients stopped taking antiretroviral drugs the virus came back again.1 2
There is a problem with creating a massive number of active CD4 cells: despite the antiretroviral drugs, HIV may manage to infect a few of these cells and replicate, thus keeping the infection alive. Scientists are now investigating chemicals that don’t activate all resting CD4 cells, but only the tiny minority that are infected with HIV.
One such chemical is valproic acid, a drug already used to treat epilepsy and other conditions. In 2005 a group of researchers led by David Margolis caused a sensation when they reported that valproic acid, combined with antiretroviral treatment, had greatly reduced the number of HIV-infected resting CD4 cells in three of four patients. They concluded that:
“This finding, though not definitive, suggests that new approaches will allow the cure of HIV in the future.”3
Sadly, it seems such optimism was premature; more recent studies suggest that valproic acid has no long term benefits.4 5 In fact it’s quite possible that all related approaches are flawed because the virus has other hiding places besides resting CD4 cells. There is a lot about HIV that remains unknown.
Bone marrow transplants and gene therapy
In November 2008, a pair of German doctors made headlines by announcing they had cured a man of HIV infection by giving him a bone marrow transplant.6 The transplant - given as a treatment for leukemia - used cells from a donor with a rare genetic mutation known as Delta 32 that confers resistance to HIV infection. Twenty months after the procedure researchers reported they could find no trace of HIV in the recipient's bone marrow, blood and other organ tissues.
Other experts have said that more tests are required to verify this cure claim,7 though it is not the first of its kind. Of more than thirty HIV positive patients given bone marrow transplantation prior to 1996, two appeared to have been cured of their infection based on molecular testing and post-mortem biopsy samples.8 9
Even assuming it can be effective, bone marrow transplantation is too dangerous and costly for widespread use as a cure. Many patients die as a result of chemotherapy or reactions to the transplant, which is usually a last resort in treating life-threatening diseases. As Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, put it:
“It’s very nice, and it’s not even surprising. But it’s just off the table of practicality.”10
Nevertheless the German transplant does raise hope for related approaches. If scientists can find another way - such as gene therapy - to confer the same sort of protection against HIV as Delta 32 provides, then they may be able to stop the virus replicating. Research in this area is in its very early stages; it may be many years before a useful treatment is found, if at all.
Hope for the future
Some of the world’s top research institutions are currently engaged in studies to learn more about infected resting CD4 cells and the behaviour of HIV. But the truth is that this field does not receive a lot of funding. Of the $1.54 Billion spent by the National Institute of Allergy and Infectious Diseases (NIAID) on AIDS in 2009, only $40 million was spent on AIDS cure research.11 This represents only 3 percent of the total NIAID AIDS budget.
Yet there are still those who remain hopeful, including activist Martin Delaney who is among those calling for an end to defeatism:
“Far too many people with HIV, as well as their doctors, have accepted the notion that a cure is not likely. No one can be certain that a cure will be found. No one can predict the future. But one thing is certain: if we allow pessimism about a cure to dominate our thinking, we surely won’t get one… We must restore our belief in a cure and make it one of the central demands of our activism.”12
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