For second time ever, a groundbreaking stem cell treatment has cured HIV

The cure for HIV is notoriously elusive. For the past decade, an American named Timothy Brown was the only person thought to have ever been cleared of the virus following an innovative stem-cell transplant procedure. Today, a study published in the journal Nature suggests that there may have finally been a second.

In both cases, the patients received a chemotherapy treatment to combat their cancer, which entailed effectively scrubbing their immune system clean and revitalizing it with transplanted stem cells. Fortunately, the donor cells also carried a rare genetic mutation that causes HIV resistance, reports the MIT Technology Review. The most recent operation occurred nearly three years ago.

The term “cure” is contentious. Despite the compelling detail that the most recent patient, a London man who has asked to remain anonymous, hasn’t taken his antiretroviral drugs for HIV since September 2017, his doctors remain cautious about claiming that he’s been cured. Notably, both Brown and the London patient were being treated for cancer, not HIV. Though the new study suggests that Brown’s case was not an anomaly, doctors have unsuccessfully attempted the same procedure with other HIV patients.

The anonymous London patient’s procedures was similar to Brown’s. They both targeted CCR5, a protein receptor that the HIV virus exploits as an entrance to the immune system. Just one percent of people with Northern European heritage are born without CCR5 receptors, according to Vox, making them resistant to HIV. Between 2007 and 2008, Brown’s doctor Gero Hütter administered two bone marrow transplants from a donor who lacked CCR5 receptors. In 2009, Hütter published his findings demonstrating that Brown appeared to be HIV-free.

In the recent study, lead author Ravindra Gupta of University College London and his team followed Hütter’s protocol to treat the London patient’s Hodgkin’s lymphoma.

HIV and AIDS have had a crippling impact across the globe since it first appeared in the 1980s. The virus has killed some 35 million people, according to the World Health Organization. Some 37 million more currently suffer from the infection, which resulted in the death of 940,000 people in 2017 alone. Although doctors are apprehensive about calling the CCR5-targeted treatment a cure, the recent study is enough to give patients and physicians a glimmer of hope.