So far, only two people appear to have been cured of HIV: Timothy Ray Brown, known as “the Berlin patient,” and more recently, an anonymous London patient. Both received bone marrow transplants to treat blood cancers, and in both cases, the donors harbored CCR5 mutations. In a bone marrow transplant, the recipient’s unhealthy blood stem cells are replaced with a donor’s healthy ones, which go on to make a variety of immune cells. In essence, the transplants reset the two men’s immune systems and eliminated HIV from their systems.

But it’s not practical to give all HIV patients bone marrow transplants. For one, it’s rare enough to find matching bone marrow donors, let alone those who also have CCR5 mutations. Only about 1% of people of European descent carry two copies of the mutation. A person needs to inherit two copies of the CCR5 mutation — one from mom and one from dad — to have HIV resistance. Bone marrow transplants can also be dangerous, because donor cells have the potential to attack the recipient’s cells.

“There’s an acute need to give these people something that restores their quality of life.”

Gene therapies, however, could get around some of these problems. Scientists at American Gene Technologies have engineered harmless viruses to carry a type of RNA molecule that’s designed to “silence” the CCR5 gene. The experimental therapy will involve collecting 400 milliliters of blood — about as much as in a blood donation bag — from HIV-infected patients. A machine will separate out T-cells, a type of immune cell that helps fight off infections. Scientists will use those T-cells to grow more in the lab, which will then be treated with the engineered viruses. About two weeks later, the modified cells will be infused back into the patient. The process is meant to be a one-time treatment to cure HIV.

“We think we’ll be returning the body to a normal immune system,” says Jeff Galvin, CEO of American Gene Technologies.

Scientists at the company have tested their therapy in the lab using T-cells from the blood of 13 people living with HIV. According to Galvin, the treated cells are no longer infected with HIV. The company has since formed a partnership with the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, which is also testing the therapy in human cells.

Galvin says he hopes to begin enrolling 15 to 18 patients in the trial this fall and possibly start treating them by the end of the year. The University of Maryland, Baltimore, will be one of the study sites. To be eligible for the treatment, patients will need to have enough T-cells to make the therapy. That’s a problem, because when HIV is left untreated, a person’s T-cell levels plummet. But antiretroviral drugs, which suppress the HIV virus, partially restore these vital immune cells.

While antiretroviral therapy is very effective, it has unpleasant and often severe side effects, like appetite loss, fatigue, vomiting, and mood changes. Galvin says that’s why his company is interested in a cure. “There’s an acute need to give these people something that restores their quality of life,” he says.