Lassa virus (LASV) is an Arenaviridae-family hemorrhagic fever virus with a high death rate and comorbidities such as persistent seizures and irreversible bilateral or unilateral deafness. According to the CDC, LASV is prevalent throughout West Africa, and Lassa fever accounts for 10–16 percent of hospitalizations in regions of Sierra Leone and Liberia each year. An ongoing epidemic in Nigeria has resulted in 144 deaths from 568 confirmed cases of LASV as of November 2018, with many more suspected, underscoring the critical need for a vaccine to prevent this deadly illness. Researchers previously reported on pLASV-GPC, a DNA vaccine containing a codon-optimized LASV glycoprotein precursor gene that totally protects Guinea pigs and nonhuman primates (NHPs) from viremia, clinical illness, and death after fatal LASV exposure. The immunogenicity profile of the LASV DNA vaccine in protected NHPs is described here. After two vaccinations with pLASV-GPC, 100% of the NHPs developed antigen-specific binding antibodies. In a pseudovirus test, these antibodies mostly adhered to the formed LASV glycoprotein complex and demonstrated strong neutralizing efficacy. T cell responses were also seen in NHPs vaccinated with pLASV-GPC DNA, as assessed by the IFN ELISpot test.

These findings show that the pLASV-GPC DNA vaccine may elicit functional, LASV-specific T cell and antibody responses, and the tests used in this study will offer a framework for future clinical trials to discover correlates of protection and describe immune responses.