The battle against HIV has been a long and difficult. As scientists have searched unsuccessfully for a cure, more than 35 million people worldwide have died of the illness since the 1980s.

Now emerging medical science—made possible by high-tech gene editing and grant money from the US National Institutes of Health—is yielding positive results in the petri dish and in monkeys, according to a new study published in the PLOS Pathogens. The study was small, but suggested scientists can genetically modify the immune system to better fight the virus.

The experiment involved genetically modifying stem cells to produce immune-system T cells and other blood cells with a specific chimeric antigen receptor (CAR) that enables them to identify and attach to antigens on HIV-infected cells. Once attached, the CAR-T cell kills the infected cells. Even better, the genetic modifications also protect the CAR-T cells from becoming infected with HIV themselves. According to the study, with these modifications, the CAR-T cells can act as sentinels, offering a robust response to the virus in infected cells. It was the first time such a method yielded results in a relevant large-animal model.

Perhaps the most notable finding researchers documented was that the engineered cells killed HIV-infected cells in petri dishes and in two macaque monkeys for a full two years. “These results set the stage for future attempts to eradicate viral infection and provide more effective immune surveillance for HIV,” the study says.

The researchers did note that their technique did not eradicate infected cells in which the HIV virus was dormant. For that reason, they say, future studies should focus on a combination approach to treatment. That would mean engineering cells to attack HIV infections while also making the blood system resistant to infection.

According to STAT, human trials of this treatment technique could begin within the next two years. The researchers are currently in communication with Calimmune, a Tucson, Arizona-based HIV gene medicines laboratory, to advance the project.

It’s not clear how much of an impact this kind of gene-therapy approach can really have on HIV at a population level, though. CAR-T therapies for cancer currently cost about $500,000. That’s an astronomical sum considering people with HIV can live relatively normal lives by taking affordable antiretroviral therapy medication already on the market.