Passive Transfer of Animal-Derived Polyclonal Hyperimmune Antibodies Provides Protection of Mice from Lethal Lassa Virus Infection

Background: Lassa virus (LASV) can cause severe acute systemic infection in humans. No approved antiviral drugs or vaccines are currently available. Antibody-based therapeutics are considered a promising treatment strategy in the management of LASV disease. Methods: We used chimeric Ifnar(−/−) C57BL/6 (Ifnar(−/− Bl6)) mice, a lethal LASV mouse model, to evaluate the protective efficacy of polyclonal antibodies purified from sera of rabbits hyperimmunized with virus-like particles displaying native-like LASV glycoprotein GP spikes. Results: Polyclonal anti-LASV GP antibodies provided 100% protection against lethal LASV infection in a pre- and post-exposure treatment setting and prevented LASV disease. Treatment also significantly lowered viremia level and virus load in organs. When treatment was initiated at the onset of symptoms, the hyperimmune antibodies provided partial protection and increased the survival rate by 80%. Conclusions: Our findings support the consideration of animal-derived hyperimmune antibodies targeting GP as an effective treatment option for highly pathogenic LASV.