The “shock and kill” method of attempting to cure HIV may cause harmful inflammation in the brain, according to a very small study in monkeys.

Shock and kill, also known as kick and kill, involves using a treatment to reverse the latency of dormant HIV-infected cells and cause them to replicate again, thus making them vulnerable to the immune system’s attack. In theory, combining this effort with antiretroviral (ARV) drugs could destroy the majority of infected cells.

Publishing their findings in the journal AIDS, researchers conducted a study of three pig-tailed macaque monkeys infected with SIV, HIV’s simian cousin, that were treated with ARVs for more than a year.

First, they gave two of the animals the latency-reversing agent ingenol-B. The treatment did not yield a significant effect, so the investigators then paired it with another latency-reversing agent, the cancer drug vorinostat, for an additional 10 days of treatment.

The animals continued to receive standard ARV treatment throughout this process.

At the end of the 10 days of the combined ingenol-B and vorinostat treatment, one of the two monkeys remained healthy while the other developed symptoms of encephalitis, or inflammation of the brain. Blood tests showed the latter animal still had an active SIV infection.

The monkey’s encephalitis worsened, so the researchers euthanized it. They then drained the blood from the animal’s body so they could separate blood sources of SIV from any virus present in the brain. They found that SIV was still present in the brain but only in a very small region: the occipital cortex, which processes visual stimuli.

Because this study was conducted in primates, its findings may not apply to humans undergoing similar treatments. The researchers also theorize that the encephalitis may have been temporary and would have resolved itself. However, they urge caution with regard to such potential side effects as scientists explore curative strategies for HIV.

To read a press release about the study, click here.

To read the study, click here.