Researchers claim to have completely eliminated the human immunodeficiency virus (HIV) from a patient’s body using a stem-cell transplant. Although this is only the second time that a person has been successfully cleared of the virus, it is raising hope that a cure for HIV could be found in the near future.
The stem-cell technique works by replacing a patient’s white blood cells with HIV-resistant ones. Only one percent of people of European descent are born with these HIV-resistant white blood cells, caused by a mutation in the CCR5 gene. Whereas normally, HIV binds to receptors on the surface of white blood cells, a deletion in the CCR5 gene prevents these receptors from functioning properly and ultimately makes a person resistant to the virus.
The technique was first used ten years ago on Timothy Ray Brown, who had both HIV and a form of blood cancer that wasn’t responding to chemotherapy. Brown underwent a stem-cell transplant in which his blood cells were replaced with stem cells from a donor, and he remains free of HIV today.
After many failed attempts to replicate Brown’s success, researchers at University College London led by Dr. Ravindra Gupta, an infectious-disease physician, have finally accomplished a second remission. The latest patient, who is unnamed, was diagnosed with HIV in 2003. He was then diagnosed with cancer in 2012, and failed to respond to standard treatments.
Gupta and his colleagues then gave the patient a stem-cell transplant using a donor with the CCR5 gene mutation. As a result, the patient’s immune system became resistant to HIV. After 16 months, the virus had completely disappeared from the patient’s body, and researchers were unable to re-infect samples of the patient’s blood with HIV in the lab. After 18 more months, during which the patient stopped taking his antiviral medications, the virus has yet to reappear.
“It is premature to conclude that this patient has been cured,” said Gupta, although he hopes that the patient, like Brown, will remain free of HIV.
The CCR5 gene mutation has been known to AIDS researchers for many years. However, Aine McKnight, a professor of viral pathology at Queen Mary University of London, warns that the treatment will only help a small portion of the population. For one, the CCR5 gene mutation only prevents HIV-1. Those with the less common variety of the virus, HIV-2, wouldn’t see improvement.
Additionally, stem-cell transplants are expensive and risky. Although the most recent transplant was considerably less harsh than the first—Brown received aggressive radiotherapy across his entire body, whereas the new patient did not—the benefits of the treatment outweigh the risk only for HIV patients also suffering from cancer or other diseases. HIV drugs are now so effective that many HIV-positive people are able to live a normal lifespan, and the need for a cure just isn’t as necessary.
“If you’re well, the risk of having a [stem-cell] transplant is far greater than the risk of staying on tablets every day,” said Graham Cooke, a clinical researcher at Imperial College London.
Ultimately, the procedure will only ever be used on a small percentage of patients with HIV: those who have also been diagnosed with cancer or another disease, and already need their immune systems reconstituted via a stem-cell transplant. However, the research also indicates growing knowledge in the field of gene therapies, and a breakthrough with even broader applications might be just around the corner.
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