Lymphocytic choriomeningitis arenavirus requires cellular COPI and AP-4 complexes for efficient virion production

Lymphocytic choriomeningitis virus (LCMV) is a bisegmented negative-sense RNA virus classified within the Arenaviridae family of the Bunyavirales order. LCMV is associated with fatal disease in immunocompromized populations, and as the prototypical arenavirus, acts as a model for the many serious human pathogens within this group. Here, we examined the dependence of LCMV multiplication on cellular trafficking components using a recombinant LCMV expressing enhanced green fluorescent protein in conjunction with a curated siRNA library. The screen revealed a requirement for subunits of both the coat protein 1 (COPI) coatomer and adapter protein 4 (AP-4) complexes. By rescuing a recombinant LCMV harboring a FLAG-tagged glycoprotein (GP-1) envelope spike (rLCMV-GP1-FLAG), we showed infection resulted in marked co-localization of individual COPI and AP-4 components with both LCMV nucleoprotein (NP) and GP-1, consistent with their involvement in viral processes. To further investigate the role of both COPI and AP-4 complexes during LCMV infection, we utilized the ARF-I inhibitor brefeldin A (BFA) that prevents complex formation. Within a single 12-h cycle of virus multiplication, BFA pre-treatment caused no significant change in LCMV-specific RNA synthesis, alongside no significant change in LCMV NP expression, as measured by BFA time-of-addition experiments. In contrast, BFA addition resulted in a significant drop in released virus titers, approaching 50-fold over the same 12-h period, rising to over 600-fold over 24 h. Taken together, these findings suggest COPI and AP-4 complexes are important host cell factors required for the formation and release of infectious LCMV.