November 30, 2020

Could a promising discovery about viral latency help scientists effectively combat human immunodeficiency virus (HIV)?

The primary obstacle to a cure for HIV infection is the reservoir, or immune cells that harbor the inactive virus when someone is being treated with antiretroviral drugs. One of the leading research strategies for eliminating HIV from the body is “shock and kill,” which involves activating a dormant virus from within these immune cells where it hides, then eliminating it. A key challenge, however, has been finding a safe way to “wake up” the virus from its latent state.

In two complementary studies—one from the Yerkes National Primate Research Center (YNPRC) of Emory University and another from the University of North Carolina at Chapel Hill—researchers report they have come closer to that goal.

The studies relied on two animal models of HIV infection. Each took a different approach, but both yielded promising results, bringing the virus out of its hiding places even in the presence of antiretroviral drugs that stopped it from replicating for months.

“If our goal is to cure HIV/AIDS, then we have to disrupt viral latency,” said Guido Silvestri, MD, chief of microbiology and immunology at the YNPRC. “What we’re doing now is a new combination approach that provides unprecedented levels of virus reactivation.”

Both approaches were tested at the YNPRC in monkeys infected with SIV, a close relative of HIV, and treated with antiretroviral drugs. At UNC, tests were also conducted in mice transplanted with human immune cells. The results represented the first occurrence of a successful systemic HIV induction in humans or an animal model with human cells that was then replicated in a completely different species infected with a different virus.

In one study, 12 monkeys were treated with the drug AZD5582, and just one experienced a temporary fever and loss of appetite—a promising sign. In the other study, researchers stimulated the cells that are the main viral hosts (CD4+ T cells) while also depleting another kind of immune cell (CD8+ T cells), which normally keeps the virus in check. The scientists indicated both the stimulation and depletion components were necessary to see SIV re-emerge.

Neither intervention mentioned above, however, reduced the size of the viral reservoir. Once the animals were taken off antiretroviral drugs, viral levels rebounded. The scientists indicated that in future studies, the initial viral reactivation needs to be combined with other modes of treatment, such as antibodies directed against the virus itself.

Want to learn more about how researchers are working toward a cure for HIV? Take a look at some other related studies from the NPRCs, including this one about reducing the viral reservoir.

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