Development of a Pentacistronic Ebola Virus Minigenome and Its Application to Model Mouse-Adapted Ebola Virus

Ebola virus (EBOV) causes hemorrhagic disease in humans with high case fatality rates. EBOV requires adaptation to cause lethal disease in mice by acquiring single mutations in both the nucleoprotein (NP) and VP24 genes. The role(s) of these two mutations in pathogenesis remains unclear. In this study, we modeled mouse-adapted EBOV (MA-EBOV) using minigenomes and transcription/replication-competent virus-like particles (trVLPs) for investigation under BSL-2 conditions. We engineered novel pentacistronic minigenomes (5xMG) containing reporter, VP40, and glycoprotein genes as well as the NP and VP24 genes from either EBOV or MA-EBOV to assess their impacts on the viral life cycle or the host’s antiviral response. The 5xMGs were constructed, optimized, and the produced trVLPs were demonstrated to infect both human and murine cell lines. Since macrophages are key cell types in EBOV infections, RAW264.7 mouse macrophages were infected with wild-type (WT) and MA-trVLPs and RNA-sequencing of their transcriptomes were compared. This revealed selective reductions in key innate immune response mRNAs following MA-trVLP infection when compared to WT-trVLP, suggesting that MA mutations may play a role in combating innate immune responses in mouse macrophages. This work demonstrates the utility of the 5xMG system as a new versatile tool to study EBOV biology.