Abstract
Hepatitis C virus (HCV) envelope proteins E1 and E2 play an essential role in virus entry. However, the fusion mechanisms of HCV remain largely unclear, hampering the development of efficient fusion inhibitors. Here, we developed two cell-based membrane fusion models that allow for screening a peptide library covering the full-length E1 and E2 amino acid sequences. A peptide from the E2 stem domain, named E27, was found to possess the ability to block E1E2-mediated cell-cell fusion and inhibit cell entry of HCV pseudoparticles and infection of cell culture-derived HCV at nanomolar concentrations. E27 demonstrated broad-spectrum inhibition of the major genotypes 1 to 6. A time-of-addition experiment revealed that E27 predominantly functions in the late steps during HCV entry, without influencing the expression and localization of HCV co-receptors. Moreover, we demonstrated that E27 interfered with hetero-dimerization of ectopically expressed E1E2 in cells, and mutational analysis suggested that E27 might target a conserved region in E1. Taken together, our findings provide a novel candidate as well as a strategy for developing potent and broad-spectrum HCV fusion inhibitors, which may complement the current direct-acting antiviral medications for chronic hepatitis C, and shed light on the mechanism of HCV membrane fusion.
Highlights
Hepatitis C virus (HCV) is a small, enveloped single-strand RNA virus that belongs to the Hepacivirus genus in the Flaviviridae family
To further optimize the peptide length and sequence for enhancing fusion inhibition activity, we focused on and synthesized additional eight peptides (35-mer offset by 10 amino acids) covering E2 (611–715)
The mechanism by which E2 participates in fusion is not clear
Summary
HCV is a small, enveloped single-strand RNA virus that belongs to the Hepacivirus genus in the Flaviviridae family. Cell entry by HCV is a multi-step process that begins with attachment of a viral particle to the cell surface via attachment factors, followed by a complex process involving a series of specific cellular entry co-receptors, including scavenger receptor class B type I (SR-BI)[7], tetraspanin CD818, claudin-19 and occludin[10,11] tight junction proteins. Envelope protein E1 and E2-mediated interaction of HCV with entry factors leads to internalization of the www.nature.com/scientificreports/. The structural data available for E1 and E2 are too limited to explain the fusion mechanism; in particular, the cellular and viral factors involved in membrane fusion remain to be identified. Several host entry factors have been implicated in this process, the viral determinants and molecular mechanisms involved in fusion need to be further characterized. Our findings reveal new insight into HCV fusion and will help in the development of novel antivirals
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