A recombinant vesicular stomatitis-based Lassa fever vaccine elicits rapid and long-term protection from lethal Lassa virus infection in guinea pigs

The World Health Organization has identified Lassa virus (LASV) as one of the top five pathogens to cause a severe outbreak in the near future. This study assesses the ability of a leading vaccine candidate, recombinant Vesicular stomatitis virus expressing LASV glycoprotein (VSVΔG/LASVGPC), and its ability to induce rapid and long-term immunity to lethal guinea pig-adapted LASV (GPA-LASV). Outbred guinea pigs were vaccinated with a single dose of VSVΔG/LASVGPC followed by a lethal challenge of GPA-LASV at 7, 14, 25, 189, and 355 days post-vaccination. Statistically significant rapid and long-term protection was achieved at all time points with 100% protection at days 7 and 14 post-vaccination. While 83 and 87% protection were achieved at 25 days and 6 months post-vaccination, respectively. When guinea pigs were challenged one year after vaccination 71% protection was achieved. Notable infectious virus was isolated from the serum and tissues of some but not all animals. Total LASVGPC-specific IgG titers were also measured on a monthly basis leading up to LASV challenge however, it is unclear if antibody alone correlates with short and long term survival. These studies confirm that a single dose of VSVΔG/LASVGPC can induce rapid and long-term protection from LASV infection in an aggressive outbred model of infection, and supports further development in non-human primates.