European researchers say they have identified a key protein that can help them identify immune cells that are harbouring dormant HIV, opening up a new way to target these cells and pave the way for a cure.

Although HIV medications can greatly reduce levels of the virus in patients, there is still no cure. The drugs can’t kill all the retrovirus because HIV has a way of infecting immune cells called T-cells and then going dormant. The virus can remain inside the cell for years or decades, hidden from the drugs designed to kill it.

But if an HIV patient stops taking her antiretroviral drugs, the dormant retrovirus will “awaken” and rapidly begin reproducing.

AIDS researchers have long sought a way to find these T-cells infected with dormant HIV so that they can target them with therapies. But it’s remained a mystery how to identify them.

Now virologists at the University of Montpellier in France think they may have found a way to recognize these “sleeper cells.” They have identified a protein called CD32a that sits on the surface of HIV-infected T-cells.

Their experiments showed that healthy T-cells do not express the protein, and neither do cells carrying active HIV. Only T-cells hiding dormant HIV make the protein.

The team made their finding after placing T-cells in lab dishes and then exposing them to fluorescently tagged HIV. They watched cells become infected and searched for differences in the gene expressions between the infected and non-infected cells. That’s when they noticed the CD32a protein marker.

The researchers then tested their theory by taking blood samples from 12 HIV-infected people who were on antiretrovirus medication. Using an antibody that sticks to CD32a, the researchers were able to extract all the cells expressing the protein. As expected, all the cells were T-cells harbouring dormant HIV.

The research team says their finding paves the way to a better understanding of viral reservoirs. It’s also possible that CD32a could one day become a reliable marker of cells that are infected with dormant HIV, which could help in the creation of drugs to target these latent cells.

The findings are published in the journal Nature. France’s CNRS (National Center for Scientific Research) has now filed for a patent for the diagnostic and therapeutic use of the biomarker.

Anthony Fauci, director of the U.S. National Insitute of Allergies and Infectious Disease in Bethesda, Maryland, told Nature that the next step will be to replicate the findings by screening blood from patients of different ethnicities, ages and stages of the disease.

Fauci said he is excited about the potential of CD23a but remains cautious about the finding given the decades of research that have gone into HIV without the discovery of a cure.