HIV Update: HIV Vaccine Shows Promising Results on Old World Monkeys

A new scientific study has once again showed that efficacy of the known human immunodeficiency virus (HIV) vaccine RV114.

RV114 is the only HIV vaccine that has been tested and shown to reduce HIV acquisition in Phase III clinical trial.

The new study, published in the journal Nature Medicine, aims to reproduce the trial results of the RV114 on Old World monkeys, rhesus macaques. Additionally, researchers wanted to test out their hypothesis stating that replacing the alum adjuvant in the vaccine with different adjuvant, MF59, would decrease the acquisition of simian immunodeficiency virus (SIV), the primate form of SIV, at an increased rate and yield a more efficacious vaccine.

For the study, the researchers simulated potential HIV infection by rectally challenging the macaques with SIV. With the simulation, the researchers were able to recapitulate the results in of RV114 trial, with 44 percent reduced risk of acquisition.

However, the study disproves the scientist working theory that MF59 could improve the efficacy of the vaccine. In fact, the MF59-combined RV114 was unable to prevent SIV acquisition at a greater rate and triggered an adaptive immune response only at the site of infection.

"These fascinating clinical results effectively dispel our previous belief that the RV144 vaccine could possibly become more effective with the MF59 adjuvant," explained Rafick-Pierre Sekaly, PhD, a professor of pathology at Case Western Reserve University School of Medicine and co-author of the study, in a statement. "Instead, we found that the modified vaccine actually triggered the recruitment of innate cells in the site of infection. Through this research, we were able to confirm the efficacy of the current RV144 vaccine in preventing infection by HIV/SIV in macaques, creating an even clearer pathway to the near-term development of this vaccine for human use."

Furthermore, researchers found a unique association between an intercellular pathway known as Ras-Raf-MEK-ERK (RAS) and the efficacy of RV144. According to a press release, 10 of the 12 genes linked to RAS pathway were expressed within the vaccine and have been shown to trigger several subsets of innate and adaptive responses. These responses were associated with the decreased risk of SIV acquisition in the alum-vaccine group.

Further studies are still needed in order to fully grasp the role of RAS activation in HIV-vaccine efficacy in humans.