Add one more name to the ever growing list of diseases that have been defeated by stem cell treatments: HIV. That’s right, according to a recent report in the New England Journal of Medicine, a stem cell transplant performed in Germany has unexpectedly removed all signs of HIV from a 42 year old American patient. The unnamed white male was treated two years ago for Leukemia with a dose of donor stem cells and his HIV RNA count has dropped to zero and remained there since. While the treatment was for Leukemia, Dr. Gero Hutter and colleagues at the Charite Universitatsmedizen in Berlin had selected the stem cell donor for his HIV resistant genes. While there are still many questions unanswered, this is the first such case of stem cells treating HIV that has been reported in a NEJM-caliber publication. Ladies and gentlemen, this is not a “cure” for HIV/AIDS, but it is certainly a remarkable and promising find. There’s more you need to know about the situation, so read on.
Like so many instances of “miraculous medicine”, this case has its complexities. First, the patient was being treated for Leukemia, not HIV. The patient had been HIV positive for ten years before the first stem cell treatment. His HIV medication was actually treating his condition fairly well, and it wasn’t until a round of chemotherapy (for the Leukemia) raised his HIV count that it looked to be troublesome. The original transplant from two years ago may have dropped his HIV count, but his Leukemia returned a year later. Another dose of stem cells was given and this seems to have treated the cancer as well as maintain its effect on the HIV.
Secondly, their’s the DNA of the donor to consider. Due to a genetic mutation (CCR5), the donor has a resistance to the HIV virus. Such resistance occurs in 1-3% of white males of European descent. Furthermore, while a single copy of this CCR5 gene can grant some resistance to HIV, the donor had two copies, which often leads to a good chance of full resistance to the virus. Dr. Hutter and colleagues were fully aware of the CCR5 in the donor when selecting him.
But it gets more complicated. The patient’s form of the virus, X4, is not typically affected by the CCR5 resistance! This leads to some major questions: why would a CCR5 donor’s stem cells effectively treat a patient with X4 HIV? Is it something special about stem cells? Do we not understand the CCR5 resistance? Do we not understand the X4 form of the virus? Is there a completely unknown factor affecting the results (chemotherapy, HIV medications… solar flares?)
The doctors involved in this treatment are very quick to point out that this is not a “cure”. Due to the nature of the disease, therapies of this kind must first eradicate most of the patient’s immune system before new stem cells can be introduced. This can kill about one in three patients. Just as important, while the HIV count of the patient has dropped to zero, this does not mean that he is HIV free. The virus could be hibernating in immune cells, brain cells, etc. While the chances of passing on the virus are lower with a zero count, it isn’t impossible. I think we can safely say that this therapy is a promising sign of how the virus can be put into full regression…not cured.
And stem cells may not actually be the most exciting part of this case. The CCR5 gene variant mutation may be a key to a new and very powerful form of HIV treatment. Further research into CCR5 could give scientists the tools to develop a gene therapy or protein manipulation that could mimic the HIV resistance. In combination with promising new vaccines, and the cocktails of HIV meds already available, CCR5 could be the nail in the coffin for HIV/AIDS.
Knowing all these qualifications and complexities, I’m still really excited by these results. Even if stem cells aren’t the cure for HIV/AIDS, they continue to impress me as an insanely versatile and effective route of treatment. Undoubtedly there are many years of research and clinical trials ahead before we’ll know all the answers to the questions raised by the German study, but for now I’m just going to sit and be amazed by this case. This may not be the cure for HIV/AIDS, but we’re getting closer. I can feel it.
[image credit: Bret Newton (modified from original)]
