Scientists Grew HIV's Rarest Hidden Cells in a Lab - and Found a Way to Make Them Killable

One cell in a million. That is approximately how rare the immune cells are that allow HIV to persist for life in people on antiretroviral therapy. These cells - called authentic reservoir clones, or ARCs - carry dormant HIV integrated into their DNA. Because the virus is silent, the immune system cannot detect the infected cells. When antiretroviral drugs are stopped, HIV rebounds from these reservoirs within weeks. People must take these medications indefinitely.

For decades, the extreme scarcity of ARCs made them nearly impossible to study directly. Researchers could infer their existence from viral rebound patterns, but actually isolating and examining them was beyond reach. Without that access, the question of why these cells persist - and how to eliminate them - remained unanswerable.

A team at Weill Cornell Medicine and Rockefeller University has now solved the isolation problem. Their findings, published February 24 in Nature, describe how they collected ARCs from study participants with HIV, grew them in the laboratory, and used that access to interrogate both how the cells survive and how they might be made to die.

Finding the Needle

"For decades, we have known that HIV hides in long-lived immune cells called T cells. But, we have not been able to study those extremely rare - one in a million - cells," said Dr. Brad Jones, senior author and associate professor of immunology in medicine at Weill Cornell. "By isolating ARCs, we can now directly interrogate how they survive and how to eliminate them." The study was co-led by Dr. Isabella Ferreira, a postdoctoral associate, and Alberto Herrera, a PhD candidate, both in the Jones lab.

Why "Shock and Kill" Strategies Have Stalled

Experimental therapies designed to wake up dormant HIV so the immune system can then kill infected cells have largely failed in clinical trials. The new experiments illuminate why. In laboratory conditions, very few ARCs actively produced virus particles at any given time, and activating them proved difficult. When the researchers introduced cytotoxic T lymphocytes (CTLs) - the immune system's primary HIV-killing cells - and maintained long contact with ARCs, most reservoir clones were gradually worn down and eliminated. CTLs catch ARCs during brief windows when HIV becomes momentarily visible, slowly shrinking the pool over time.

But a subset of ARCs proved resistant. Even under sustained CTL pressure, some cells persisted through multiple rounds of proliferation. Others survived without proliferating at all. "The problem is not only latency," Dr. Jones explained. "It is latency plus resistance to death."

Reversing That Resistance

The team tested deferoxamine - an FDA-approved drug used clinically for other indications - and found that it increased oxidative stress inside resistant ARC cells, making them more vulnerable to CTL attack. "By sensitizing cells to oxidative stress, we were able to restore the cell's susceptibility to immune cell attacks. That suggests rational combination strategies are within reach," Dr. Jones said. Whether this translates into meaningful reservoir reduction in people on antiretroviral therapy requires clinical testing. The study identifies a proof-of-concept mechanism, not a cure.

The team's immediate priorities include refining ARC culture techniques and establishing protocols to share methods with other laboratories. The research was supported by NIAID through the INSPIRE grant and by the NIH Martin Delaney Collaboratory grant, funding the REACH program led by Dr. Jones.