Progress in Elucidating Potential Markers and Mechanisms of Rapid Protection Conferred by the VSV-Vectored Ebola Virus Vaccine.

Research progress over the past 20 years has yielded several experimental Ebola virus (EBOV) vaccine candidates, which were shown to be effective in non-human primates when given 28 days before a lethal challenge. Of these, the vesicular stomatitis virus (VSV)-vectored vaccine against EBOV (VSV-EBOV) is unique at being able to induce rapid protection, with 100% survival achieved as soon as 7 days after EBOV challenge. In a recent mBio article, Menicucci et al. carried out a transcriptome analysis of host responses in monkeys immunized with VSV-EBOV from 28 to 3 days before challenge (A. R. Menicucci, A. Jankeel, H. Feldmann, A. Marzi, and I. Messaoudi, mBio 10:e00597-19, 2019, https://doi.org/10.1128/mBio.00597-19). It was found that surviving animals had a controlled innate immune response coupled with rapid adaptive immunity, but this was not detected in nonsurviving animals. These studies highlight the important role innate immunity plays in creating an antiviral state to restrict EBOV replication and ensuring enough time for the vaccine to induce an effective adaptive immune response.