This week it was reported a person with HIV seems to be free of the virus after receiving a stem-cell transplant that replaced their white blood cells with HIV-resistant versions. The patient is only the second person ever reported to have been cleared of the virus using this method.
The patient was able to stop taking antiretroviral drugs, with no sign of the virus returning 18 months later. The stem-cell technique was 10 years ago for Timothy Ray Brown, known as the ‘Berlin patient.’ Timothy still remains HIV-free from his 2009 treatment.
Researchers warn that it is still too early to say that they have been cured. It is unclear if others were treated by the same methods and it failed.
How to beat HIV
So far, the latest patient to receive the treatment is showing a response similar to Brown’s, says Andrew Freedman, a clinical infectious-disease physician at Cardiff University in the UK who was not involved in the study. “There’s good reason to hope that it will have the same result,” he says.
Like Brown, the latest patient also had a form of blood cancer that was not responding to chemotherapy. They required a bone-marrow transplant, in which their blood cells would be destroyed and replenished with stem cells transplanted from a healthy donor.
But rather than choosing just any suitable donor, the team — led by Ravindra Gupta, an infectious-disease physician at the University of Cambridge, UK — picked a donor who had two copies of a mutation in the CCR5 gene that gives people resistance to HIV infection. This gene codes for a receptor which sits on the surface of white blood cells involved in the body’s immune response. Normally, the HIV binds to these receptors and attacks the cells, but a deletion in the CCR5 gene stops the receptors from functioning properly. About 1% of people of European descent have two copies of this mutation and are resistant to HIV infection.
The researchers report that the transplant successfully replaced the patient’s white blood cells with the HIV-resistant variant. Cells circulating in the patient’s blood stopped expressing the CCR5 receptor, and in the lab, the researchers were unable to re-infect these cells with the patient’s version of HIV.
The team found that the virus completely disappeared from the patient’s blood after the transplant. After 16 months, the patient stopped taking antiretroviral drugs, the standard treatment for HIV. In the latest follow-up, 18 months after stopping medication, there was still no sign of the virus.
The good news is Brown’s successful treatment ten years ago wasn’t just a one-off. Gupta says that the latest patient received a less aggressive treatment than Brown to prepare for the transplant. The new patient was given a regimen consisting of chemotherapy alongside a drug that targets cancerous cells, while Brown received radiation therapy across his entire body in addition to a chemotherapy drug.
This is great because stem-cell transplants in HIV patients would not necessarily need to be accompanied by very aggressive treatments that might have particularly severe side effects.
Graham Cooke, a clinical researcher at Imperial College London, believes the risks outweigh the reward for patients without bone cancer. “If you’re well, the risk of having a bone-marrow transplant is far greater than the risk of staying on tablets every day,” he says. Most people with HIV respond well to daily antiretroviral treatment.
But Cooke adds that for those who need a transplant to treat leukemia or other diseases, it seems reasonable to try and find a donor with the CCR5 mutation, which wouldn’t add any risk to the procedure.