Vps4 and the ESCRT-III complex are required for the release of infectious hepatitis C virus particles

TLDR

The assembly and release of infectious hepatitis C virus particles are poorly understood, yet many enveloped viruses exploit the host ESCRT machinery for membrane remodeling. The study aimed to determine whether HCV relies on the ESCRT pathway for virion release. A conditional virus‑like particle system was established by trans‑complementing an envelope‑deleted JFH‑1 genome with plasmids, enabling controlled production of infectious particles. Dominant‑negative ESCRT‑III or Vps4 expression markedly reduced infectious particle release without affecting replication or intracellular accumulation, confirming that HCV depends on late ESCRT components for virion egress.

Abstract

The mechanisms by which infectious hepatitis C virus (HCV) particles are assembled and released from infected cells remain poorly characterized. In this regard, many other enveloped viruses, notably human immunodeficiency virus type 1, have been shown to utilize the host vacuolar protein sorting machinery (also known as the endosomal sorting complex required for transport; ESCRT) to traffic through the cell and effect the membrane rearrangements required for the formation of enveloped particles. We postulated that this might also apply to HCV. To test this hypothesis, we established a method of conditional virus-like particle assembly involving trans-complementation of an envelope-deleted JFH-1 genome using plasmid transfection. This system reliably produced virus particles that were infectious and could be enumerated easily by focus-forming assay in Huh7 cells. Following co-transfection with plasmids expressing various dominant-negative forms of either components of the ESCRT-III complex or Vps4 (the AAA ATPase that recycles the ESCRT complexes), a reduction in particle production was seen. No significant effect was observed after co-transfection of dominant-negative ESCRT-I or Alix, an ESCRT associated protein. Dominant-negative Vps4 or ESCRT-III components had no effect on either virus genome replication or the accumulation of intracellular infectious particles. These data were confirmed using cell culture infectious HCV and we conclude that HCV requires late components of the ESCRT pathway for release of infectious virus particles.