The only HIV vaccine to achieve even moderate success in humans also works in monkeys. Publishing their findings in Nature Medicine, researchers sought to reproduce the results of the RV144 HIV vaccine trial, this time in macaque monkeys, testing the vaccine’s efficacy in preventing rectal exposure to SIV, HIV’s simian cousin.

The scientists also tested to see whether changing a component of the vaccine known as the alum adjuvant, which is an agent common to nonliving vaccines that can prompt immunity through antibodies, would improve the vaccine’s efficacy. They used an adjuvant called MF59 instead.

The original form of the vaccine decreased the infection rate by 44 percent among the monkeys, a result statistically similar to the 31 percent efficacy found in humans. The vaccine with the MF59 adjuvant did not improve efficacy, however.

A considerable finding in the study was that the researchers were able to identify, based on a genetic analysis conducted before administration of the vaccine, whether the monkeys would respond to it. Their forecasting model successfully predicted outcomes in two thirds of the animals.

“We have seen that pre-selecting subjects that will benefit from a therapy based on their predicted response or risk of disease is an excellent way to improve potential outcomes,” Rafick-Pierre Sékaly, PhD, a professor of pathology at Case Western Reserve University School of Medicine, said in a press release. “These study results strongly support the notion that personalized and predictive vaccinology will soon become a reality, including in HIV—a disease area for which this type of precision medicine is desperately needed but has not yet been extensively studied.”

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