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Antiviral Res. 2019 Feb;162:118-129. doi: 10.1016/j.antiviral.2018.12.019. Epub 2018 Dec 30.

An E. coli-produced single-chain variable fragment (scFv) targeting hepatitis B virus surface protein potently inhibited virion secretion.

Author information

1
Key Laboratory of Medical Molecular Virology, Ministry of Education and Ministry of Health, Shanghai Medical College of Fudan University, Shanghai, China.
2
University Hospital Freiburg, Department of Internal Medicine II/Molecular Biology, Freiburg, Germany.
3
Inserm, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France.
4
Key Laboratory for Medical Virology, NHFPC, National Institute for Viral Disease Control and Prevention, China CDC, Beijing, China.
5
Inserm, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France; Université de Strasbourg, Strasbourg, France; Institut Hospitalo-Universitaire, Pôle 5 Hépato-digestif, Nouvel Hôpital Civil, Strasbourg, France.
6
Key Laboratory of Medical Molecular Virology, Ministry of Education and Ministry of Health, Shanghai Medical College of Fudan University, Shanghai, China. Electronic address: yongxiangwang@fudan.edu.cn.

Abstract

Hepatitis B virus (HBV) envelopes as well as empty subviral particles carry in their lipid membranes the small (S), middle (M), and large (L) surface proteins, collectively known as hepatitis B surface antigen (HBsAg). Due to their common S domain all three proteins share a surface-exposed hydrophilic antigenic loop (AGL) with a complex disulfide bridge-dependent structure. The AGL is critical for HBV infectivity and virion secretion, and thus represents a major target for neutralizing antibodies. Previously, a human monoclonal antibody (mAb) targeting a conformational epitope in the AGL, IgG12, exhibited 1000-fold higher neutralizing activity than hepatitis B immune globulin (HBIG). Here we designed a single-chain variable fragment (scFv) homolog of IgG12, G12-scFv, which could be efficiently produced in soluble form in the cytoplasm of E. coli SHuffle cells. Independent in vitro assays verified specific binding of G12-scFv to a conformational S epitope shared with IgG12. Despite 20-fold lower affinity, G12-scFv but not an irrelevant scFv potently neutralized HBV infection of susceptible hepatoma cells (IC50 = 1.8 nM). Strikingly, low concentrations of G12-scFv blocked virion secretion from HBV producing cells (IC50 = 1.25 nM) without disturbing intracellular viral replication, whereas extracellular HBsAg was reduced only at >100-fold higher though still nontoxic concentration. The inhibitory effects correlated with S binding specificity and presumably also G12-scFv internalization into cells. Together these data suggest G12-scFv as a highly specific yet easily accessible novel tool for basic, diagnostic, and possibly future therapeutic applications.

PMID:
30599174
DOI:
10.1016/j.antiviral.2018.12.019
[Indexed for MEDLINE]
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