A “potential cure” for AIDS?
During the past week, there has been a flurry of media coverage about what some people are claiming is a “potential cure” for AIDS. I’ve seen coverage in a variety of news outlets, from the Wall Street Journal to the Metro and Yahoo News.
Having read about dozens – if not hundreds – of “AIDS cures” in the 25+ years of the epidemic, I maintain what I think is a healthy degree of skepticism about such claims.
Many past claims of AIDS cures have had little of no scientific basis, often relying instead on magical thinking, secret ingredients, and pseudoscientific techniques. In a relatively few instances, the claims about potential cures have been based in legitimate medical research.
Unfortunately, time and experience have shown that either the researchers, the media, or both were overenthusiastic in announcing a cure or potential cure that is, at best, still many years away.
In my opinion, the recent news fits into the latter category. The current story involves the case of an HIV-infected American man living in Berlin, Germany, who received a bone marrow transplant for acute leukemia. At the time, he had been successfully treated with an HIV drug regimen for several years. HIV drugs dramatically reduce the production of HIV in the body, but they aren’t able to eliminate the virus completely. Like other people who’ve been successfully treated with HIV drugs, the Berlin patient remained infected with the HIV virus and, as such, couldn’t be considered “cured” of the disease.
His leukemia treatment involved a combination of radiation and chemotherapy followed by a bone marrow transplant – one of the options available for persons with acute leukemia. However, the Berlin patient’s transplant procedure was unusual, because his doctors screened potential bone marrow donors for a particular gene mutation called the CCR5 delta 32. People who inherit this mutation from both parents – about one in every 60 White Americans and Europeans – have a natural immunity to the most common forms of HIV; they lack a receptor called CCR5 that the virus uses to infect cells.
The doctors found a bone marrow donor with the CCR5 mutation and transplanted the marrow into the Berlin patient. They hoped that, with its CCR5 delta 32 mutation, this transplanted marrow might help the patient fight HIV more effectively. They also stopped his HIV drugs at that time due to concerns that the drugs might harm the transplanted marrow cells. They planned to restart his HIV treatment when detectable levels of the virus reappeared in his blood.
However, to their delight and surprise, the doctors found that there was no detectable HIV in his blood – nor was there any detectable HIV in his bone marrow, lymph nodes, intestines, or brain. Now, more than 600 days after his bone marrow transplant, the Berlin patient continues to have no detectable HIV.
So is this truly a cure?
Based on what I’ve read, some HIV specialists think that the Berlin patient may be functionally “cured,” in the sense that he has no detectable HIV, a normal CD4 T-cell count, and remains off HIV treatment. However, because HIV has the capacity to live for a very long time in some cells, and it is not currently possible to scan every cell for HIV, we can’t be sure that the virus has been completely cleared from his body.
In the Wall Street Journal, Nobel Prize winning researcher David Baltimore said that the case of the Berlin patient could serve as a “proof of principle” for a gene therapy approach for fighting HIV infection. However, since it’s just a single case, Baltimore also noted that the finding might simply be a fluke.
Could this marrow transplant approach be readily applied to other HIV-infected persons?
For the present, the answer seems to be a resounding “No” for several reasons. First, bone marrow transplants are inherently risky procedures, with a relatively high rate of serious health complications and risk of death. They are also very expensive, costing up to $250,000. In addition, since the CCR5 Delta 32 mutation is relatively uncommon, the number of potential marrow donors would be very small.
It is possible that researchers might someday develop techniques to produce large amounts of cells lacking the CCR5 receptor, and that these cells might be successfully transplanted into HIV-infected persons. However, even if such techniques are developed, they will likely have to undergo years of testing to ensure that they are safe and effective and can be performed at an affordable cost.
