Doctors in Boston have made what they consider a major discovery in the world of AIDS research: the HIV virus has become undetectable in the blood of two men following bone marrow transplants that were part of their treatment for cancer. Researchers from Brigham and Women’s Hospital presented their findings at the International AIDS Conference Thursday in Washington, D.C., and WBUR’s All Things Considered host Sacha Pfeiffer spoke with one of those infectious disease physicians, Dr. Daniel Kuritzkes.
Sacha Pfeiffer: These two patients you’re studying had detectable levels of DNA from the HIV virus in their blood before having bone marrow transplants. The transplants took place two years ago for one of the patients and four years ago for the other. What happened with their HIV infections after that point?
Dr. Daniel Kuritzkes: As the transplanted cells took hold and killed off the patients’ own cells, which is the point of the transplant, we lost the ability to detect the HIV DNA in their cells. This is important because it’s the HIV DNA in cells that is really the reservoir of HIV, and why the virus persists even though anti-retroviral therapy is stopping it from reproducing.
And what was it that you think killed them off?
We expected that the donor cells would kill the host cells, but typically the donor cells become infected by HIV in the process of doing that. That’s because in most cases, the chemotherapy that patients get before the bone marrow transplant is so severe that it causes side effects that prevent patients from continuing their AIDS medicines. In the case of our patients, they got a milder form of chemotherapy and were able to continue their anti-retroviral therapy throughout the entire transplant period. Therefore they were able to protect the uninfected donor cells from becoming infected. And that’s what’s so unique in this case.
But typically you may kill off the cancer, but the person remains HIV-positive after the treatment?
That’s exactly right.
After these transplants, your patients still tested positive for HIV in terms of antibodies, meaning their bodies still showed elevated levels of antibodies, indicating they’d been exposed to HIV. But I understand the antibody levels went down. Why is that significant?
The reason that’s significant is it tells us that there is little if any remaining HIV protein that could stimulate an antibody response.
So, considering all of that, do you consider this a cure of these two patients in terms of their HIV?
I think it’s really premature for us to talk about cure in these patients. We can’t say for certain that there isn’t HIV hiding somewhere in these patients that we don’t have access to. The only way to do that would be to stop therapy and to watch very carefully to see if any signs of HIV came back, and that’s something we can only do after we discuss this with the patients, their clinicians, and our Human Subjects Board to get approval to do that.
If transplants like the ones that your patients got are proved to be very beneficial in terms of eliminating HIV possibly, how realistic is it that these could be part of a standard step in a cure?
I don’t think bone marrow transplants are going to become a standard step towards a cure in the majority of HIV-infected patients because they’re risky and costly procedures to undergo. I do think, however, that this is an additional important step on the path towards finding a more practical cure, and it gives additional reason for optimism that we are on the right track.
Dr. Kuritzkes and his fellow researchers also want to test the tissue of the patients to search for the presence of HIV. There is another man, from Seattle, considered “cured” of HIV after receiving a stem cell transplant in Germany. But there’s now a debate over whether some of his tissue samples show evidence of HIV, and that man’s treatment had some significant differences from the Boston patients’ treatment.