Abstract
The highly pathogenic Old World arenavirus Lassa virus (LASV) and the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) use α-dystroglycan as a cellular receptor and enter the host cell by an unusual endocytotic pathway independent of clathrin, caveolin, dynamin, and actin. Upon internalization, the viruses are delivered to acidified endosomes in a Rab5-independent manner bypassing classical routes of incoming vesicular trafficking. Here we sought to identify cellular factors involved in the unusual and largely unknown entry pathway of LASV and LCMV. Cell entry of LASV and LCMV required microtubular transport to late endosomes, consistent with the low fusion pH of the viral envelope glycoproteins. Productive infection with recombinant LCMV expressing LASV envelope glycoprotein (rLCMV-LASVGP) and LCMV depended on phosphatidyl inositol 3-kinase (PI3K) as well as lysobisphosphatidic acid (LBPA), an unusual phospholipid that is involved in the formation of intraluminal vesicles (ILV) of the multivesicular body (MVB) of the late endosome. We provide evidence for a role of the endosomal sorting complex required for transport (ESCRT) in LASV and LCMV cell entry, in particular the ESCRT components Hrs, Tsg101, Vps22, and Vps24, as well as the ESCRT-associated ATPase Vps4 involved in fission of ILV. Productive infection with rLCMV-LASVGP and LCMV also critically depended on the ESCRT-associated protein Alix, which is implicated in membrane dynamics of the MVB/late endosomes. Our study identifies crucial cellular factors implicated in Old World arenavirus cell entry and indicates that LASV and LCMV invade the host cell passing via the MVB/late endosome. Our data further suggest that the virus-receptor complexes undergo sorting into ILV of the MVB mediated by the ESCRT, possibly using a pathway that may be linked to the cellular trafficking and degradation of the cellular receptor.
Highlights
Over the past decades, several arenaviruses have emerged as causative agents of severe viral hemorrhagic fevers (VHF) that belong to the most devastating human diseases [1]
We and others had shown that lymphocytic choriomeningitis virus (LCMV) and Lassa virus (LASV) attach to a cellular receptor, adystroglycan, followed by internalization by endocytosis via a novel and unusual pathway
We discovered that during cell entry LASV and LCMV pass through a particular intracellular compartment, the multivesicular body (MVB)/late endosome, which is implicated in the internalization and degradation of cellular membrane receptors
Summary
Several arenaviruses have emerged as causative agents of severe viral hemorrhagic fevers (VHF) that belong to the most devastating human diseases [1]. The Old World arenavirus Lassa virus (LASV) is the most prevalent human pathogen among the arenaviruses, causing several hundred thousand infections per year in Africa with thousands of deaths [2,3]. The prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) merits significant attention as a powerful tractable experimental model system to study virus-host interactions and as a prevalent human pathogen of clinical significance in congenital infections [6,7,8]. LCMV infection of immunosuppressed adults can result in severe disease and death [9,10]
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