A combination of a potent antibody and an immune system stimulant can reduce levels of latent HIV in rhesus monkeys undergoing antiretroviral therapy, reports a study published online this week in Nature. This strategy could prevent HIV re-emergence after antiretroviral therapy.

Antiretroviral drugs help manage HIV infections by preventing viral replication. However, they do not eliminate the ‘hidden’ reservoir of latent viruses that remains in certain cells and can re-emerge if treatment stops. Broadly neutralizing antibodies have been shown to reduce virus levels when they are administered following suspension of antiretroviral therapy. However, it was unknown whether antibodies could target latent HIV reservoirs.

Dan Barouch and colleagues administered a combination of a broadly neutralizing antibody and an innate immune system stimulator to 11 rhesus monkeys that were infected with a form of the virus that infects non-human primates and were undergoing antiretroviral therapy. The stimulator activated both uninfected immune cells and those harbouring the virus, allowing the antibody to flag the infected cells for elimination. The authors found that 6 of the 11 monkeys showed signs of viral rebound 28 weeks after antiretroviral treatment was suspended. The virus rebounded in all 11 monkeys in a control group that did not receive the combination treatment, in an average of 21 days.

The monkeys began antiretroviral therapy shortly after infection, so their viral reservoirs may have been small and relatively easy to eliminate. Additionally, they were only monitored for 28 weeks, whereas in humans HIV can take up to two years to rebound. The authors conclude that, in principle, broadly neutralizing antibodies could offer a useful strategy against latent HIV infection in humans, although further testing is required.