A Lethal Pseudofilovirus Model in Ifnar1(-/-) Mice Using Recombinant Vesicular Stomatitis Viruses.

Filoviruses cause highly lethal infectious diseases with hemorrhagic symptoms and extremely high fatality rate (up to 90%). Although two vaccines against Ebola virus (EBOV) are licensed for application in endemic areas, vaccines against other filoviruses (SUDV, BDBV, MARV) are still at pre-clinical or clinical stages. The development of vaccines requires protective efficacy studies using animal models of infection. However, animal studies using wild-type filoviruses require maximum biosafety level (BSL-4), which hinders filoviral vaccine advancement. In this study, we developed a surrogate animal model of EBOV-, SUDV-, BDBV- and MARV- GP-mediated entry using Ifnar1-knockout (-/-) mice and recombinant vesicular stomatitis viruses (rVSVs), carrying a genetic sequence of filoviral glycoprotein (GP) and pseudotyped with correspondent GP. We showed that rVSV-EBOV-GP was 100% lethal for Ifnar1(-/-) mice after inoculation by multiple routes, and its active propagation was within 24 h post-infection. We performed dose-dependent lethality assessment in small groups to estimate median lethal doses for rVSV-EBOV-GP, rVSV-SUDV-GP, rVSV-BDBV-GP, rVSV-MARV-GP in Ifnar1-knockout mice and showed high viral load in liver and immune cell reservoirs. The developed models contribute to safe and effective research of filoviral vaccines and therapeutic antibodies under BSL-2 conditions.