HIV may still be on a global rampage, but at least scientists are attempting to make good out of a bad situation. This virus, and its relatives, has the ability to permanently insert its own DNA into our genome, which is extremely bad news for our cells and also the main reason that AIDS remains incurable.

But scientists are using this deadly skill to their advantage, realizing the potential of exploiting these viruses in order to add in therapeutic genes to diseased cells, a budding technique known as gene therapy. And it seems that this promising technique could be holding up to its expectations, as six boys with a rare and potentially life-threatening genetic disease have just been cured with its help.

Wiskott-Aldrich syndrome affects between 1 and 10 million babies born worldwide and is almost exclusively found in males. It’s characterized by a compromised immune system and a reduced ability to form blood clots, leaving individuals vulnerable to infections and prolonged bleeding after injury. It also significantly raises the risk of developing autoimmune disorders and some types of cancer, like lymphoma.

The disease is caused by mutations in a gene called WAS, which is responsible for the production of a protein that helps white blood cells interact with foreign invaders, like harmful bacteria and viruses. Sufferers don’t make enough of this protein, meaning that their immune system cannot respond properly to pathogens. The protein also helps our clot-forming cells develop, which is why individuals with the condition also have bleeding problems.

Although the condition is often curable by means of a bone marrow transplant from a healthy donor, this is far from ideal because it requires a close tissue match, such as a sibling, and is associated with significant health problems. That’s why scientists began to wonder whether gene therapy could offer a viable alternative solution, so they designed a modified form of HIV that cannot cause disease but contains the DNA needed to create the protein that Wiskott-Aldrich patients are lacking.

Bone marrow from seven children enrolled into a clinical trial was then removed before being purified to isolate the desirable immune cells. These were then infected with the modified HIV, which delivered the therapeutic genes to the recipient’s genome. The altered cells were then put back in the children and their responses were monitored.

Although one patient died due to a preexisting drug-resistant herpes infection, the six surviving children showed long-term clinical benefit, the researchers report in JAMA. They were no longer susceptible to infection and thus spent significantly less time in hospital, and they stopped experiencing severe bleeding episodes. Furthermore, autoimmunity improved in all of the affected patients, and one child no longer needed a wheelchair, BBC News reports.

Although gene therapy got off to a bad start, with several trials being abandoned due to modified cells becoming cancerous, this encouraging trial offers renewed hope that this promising treatment could have a valuable place in medicine. That being said, larger trials are still required to ensure that the therapy is indeed safe and effective long-term.