A joint U.S. and Canadian team of researchers say they have confirmed how specific immune cells serve as a protected reservoir of HIV, despite potent antiretroviral (ARV) therapy. They also offer ideas for eradicating that sanctuary of cells—and the virus along with it—in a study published online June 21 in Nature Medicine.

Scientists once though that HIV might be eradicated in people who kept their viral loads undetectable for several years using ARV therapy. Ultimately, they learned that HIV manages to hide out in some very long-lived cells in lymph nodes throughout the body that remain unaffected by HIV treatment. When ARV therapy is stopped, the virus comes roaring back.

Nicolas Chomont, PhD, from the Université de Montréal, Canada, and his colleagues in Montreal and Florida claim they have now confirmed which cells specifically serve as hidden sanctuaries, and how those cells manage to replicate new virus even when potent ARV therapy is being used.

The cells in question are memory CD4s—cells programmed, often in childhood, at the time of an initial infection with a disease-causing microorganism. This particular group of cells was determined to be the long-lived sanctuary of HIV more than 10 years ago.

Chomont’s team went one step further and believes it has confirmed why memory CD4s aren’t vulnerable to HIV drugs—the cells subdivide, thus replicating not only the cells, but also the virus that has become embedded in the cells’ genetic code. ARV treatment can’t reach that virus because HIV remains in the cells that are actively replicating.

The authors hope that they and other scientists may be able to develop a one-two punch that will include not only ARV therapy, but also drugs that keep the memory CD4 cells from dividing. According to Chomont, if ARV therapy is used long enough, and most of the infected cells die, then there is a chance that the infection may ultimately burn itself out.