Orthoflavivirus-Based, DNA-Launched, Self-Amplifying and Self-Packing RNA Replicons for Vaccine Development

Self-amplifying vaccines based on alphavirus replicons are well established. Preclinical studies of self-amplifying vaccines based on orthoflaviviruses have also been described and include replicons based on Kunjin virus (KUNV). KUNV is an Australian subtype of West Nile virus with typically mild or asymptomatic clinical presentations in humans. Single round infectious particles (SRIPs) have emerged as an effective vaccine delivery modality for KUN replicon RNA vaccines. For instance, a SRIP vaccine encoding the glycoprotein (GP) of Zaire Ebolavirus (EBOV) was previously shown to be effective in guinea pigs and non-human primates. These SRIPs comprise self-amplifying KUN replicon RNA packaged within KUNV structural proteins, and represent virus-like-particles capable of infecting cells and delivering replicon RNA encoding an immunogen. Using EBOV GP as the model immunogen, we describe herein a novel SRIP DNA plasmid construct that illustrates a simplified in vitro methodology for the production of KUN replicon SRIPs. This SRIP DNA was also evaluated as a potential DNA vaccine; however, it performed similarly to a conventional DNA vaccine for eliciting anti-GP antibodies in Ifnar1−/− mice.