Recombinant Pichinde reporter virus as a safe and suitable surrogate for high-throughput antiviral screening against highly pathogenic arenaviruses.

Several arenaviruses, such as the Old World (OW) Lassa virus (LASV) and the New World (NW) Junin virus (JUNV), can cause severe and lethal viral hemorrhagic fevers in humans. Currently, no vaccines or specific antiviral therapies are FDA-approved for treating arenavirus infections. One major challenge for the development of new therapeutic candidates against these highly pathogenic viruses is that they are BSL-3/4 pathogens that need to be handled in high biocontainment laboratories. In this work, a recombinant non-pathogenic New World arenavirus, Pichinde virus (rPICV), was used for the development of a high-throughput screening (HTS) assay in the BSL-2 laboratory for the screening and identification of small molecule inhibitors against arenaviruses. The rPICV is a replication-competent virus expressing the firefly luciferase reporter gene in the infected cells proportionally to the infection rate. rPICV infection was optimized for an automated HTS in 384-well format with robust Z' scores, high signal-to-background ratios, and low intrinsic variance. Screening an established library allowed for the identification of five top hit compounds, which included ribavirin, a known inhibitor of arenaviral RNA synthesis, showing good potency and selectivity in inhibiting rPICV replication. The antiviral activity of the top hit compounds was further validated against another recombinant arenavirus, the OW lymphocytic choriomeningitis virus (rLCMV) and against laboratory strains of LASV (Josiah) and JUNV (Romero). The use of rPICV in the HTS-based antiviral assay under BSL-2 condition has proven to be safe and suitable for the identification of broad-spectrum small molecule inhibitors against highly pathogenic arenaviruses.