In December, researchers reported that an HIV-positive man who was seemingly cured of the disease after receiving a bone marrow transplant from an HIV-resistant donor was still virus-free three years after undergoing the therapy.

And as we reported last year, the initial surprising discovery of this so-called ‘Berlin patient’ had prompted several research teams to devise ways to recapitulate the genetic defect found in the bone marrow donor — a rare mutation in the gene encoding C-C chemokine receptor type 5, or CCR5, a surface protein implicated in HIV infection.

Well, the idea seems to be working. Last week, a California biotech revealed that treating people with enzymes engineered to disrupt the CCR5 gene improved immune function in the majority of HIV-infected subjects who received the experimental treatment.

The therapeutic approach, developed by Sangamo Biosciences, involved a single infusion of ‘zinc finger nuclease’ enzymes directed against CCR5. The therapy was well tolerated, the company announced, and five out of six study subjects showed elevated levels of the specific type of helper T cells that fight off HIV infections.

“These compelling data provide a mechanistic proof of concept for this novel approach to HIV therapy which shows the most promise of any yet tested,” trial investigator Carl June, director of translational research at the Abramson Family Cancer Research Institute at the University of Pennsylvania School of Medicine in Philadelphia, said in a statement. June will present the data on Wednesday at the Conference on Retroviruses and Opportunistic Infections in Boston.