Phosphatidylserine Vesicles Enable Efficient En Bloc Transmission of Enteroviruses

Abstract

A central paradigm within virology is that each viral particle largely behaves as an independent infectious unit. Here, we demonstrate that clusters of enteroviral particles are packaged within phosphatidylserine (PS) lipid-enriched vesicles that are non-lytically released from cells and provide greater infection efficiency than free single viral particles. We show that vesicular PS lipids are co-factors to the relevant enterovirus receptors in mediating subsequent infectivity and transmission, in particular to primary human macrophages. We demonstrate that clustered packaging of viral particles within vesicles enables multiple viral RNA genomes to be collectively transferred into single cells. This study reveals a novel mode of viral transmission, where enteroviral genomes are transmitted from cell-to-cell en bloc in membrane-bound PS vesicles instead of as single independent genomes. This has implications for facilitating genetic cooperativity among viral quasispecies as well as enhancing viral replication.

Protein composition of the hepatitis A virus quasi-envelope

“…These enteroviral vesicles are much larger than eHAV, and contain a much greater number of viral capsids than eHAV vesicles (2,6). Their size resembles extracellular vesicles and autophagous blebs shed from the plasma membrane, and is distinct from MVB-derived exosomes that are generally much smaller (<150 nm) and similar to eHAV (2,17).…”

“…Recent studies have brought increasing recognition to the fact that multiple members of the Picornaviridae are released from cells enclosed in membranous vesicles in the absence of cell lysis (2)(3)(4)(5)(6). This mode of cellular egress has been suggested to play an important role in disease pathogenesis by masking viral antigens from the immune system (2) or increasing the number of viral genomes delivered to single infected cells (6).…”

“…This mode of cellular egress has been suggested to play an important role in disease pathogenesis by masking viral antigens from the immune system (2) or increasing the number of viral genomes delivered to single infected cells (6). However, many questions remain concerning the mechanisms underlying the release of virus in extracellular vesicles.…”

“…Coxsackievirus B, poliovirus, and many other members of the genus Enterovirus typically cause lytic infections in cultured cells. However, viruses in this genus are also released within extracellular vesicles before cell lysis, often with many capsids packaged within a single vesicle (4)(5)(6). The cellular egress of these classically nonenveloped viruses in membrane-bound vesicles has blurred the distinction between enveloped and nonenveloped viruses and has important implications for pathogenesis (2).…”

“…Although the size and density of eHAV vesicles are consistent with an exosome-like origin in multivesicular bodies (MVBs) (2, 3), eHAV biogenesis remains incompletely defined and the protein composition of the membranes surrounding the quasi-enveloped capsid is unknown. In contrast, the extracellular vesicles involved in egress of enteroviruses have been suggested to be derived from autophagosomes, as they contain lipidated LC3-II, a marker of autophagy, and disrupting autophagy blocks their release (4,6). However, the protein composition of these extracellular vesicles also has yet to be comprehensively investigated.…”