西辻 裕紀

Hepatitis B virus (HBV) infection remains a major global health challenge. While sodium taurocholate co-transporting polypeptide (NTCP) is the primary receptor for HBV entry, the molecular mechanisms regulating NTCP-mediated viral entry remain incompletely understood. Here, we identified CD46 as a crucial regulatory factor for NTCP membrane expression. We found that CD46 interacted with NTCP in cis at the plasma membrane through proximity-based labeling screening. The depletion of CD46 significantly reduced cell-surface NTCP levels and HBV infection in hepatocytes. Anti-CD46 monoclonal antibodies, particularly clone E4.3, inhibited HBV infection by triggering NTCP internalization from the plasma membrane to intracellular vesicles. The antiviral effect of CD46 antibodies was also confirmed in primary human hepatocytes. Our study reveals a previously unknown mechanism regulating NTCP-mediated HBV entry and suggests CD46 as a potential therapeutic target for HBV infection.

Hepatitis B virus (HBV) infection is a major global health burden worldwide despite the availability of an effective vaccine and effective anti-HBV drugs. The currently approved anti-HBV drugs-i.e., nucleos(t)ide analogues and pegylated interferon α-can effectively suppress HBV replication, but rarely achieve a functional cure. Accordingly, new anti-HBV agents targeting different aspects of the HBV life cycle are needed. In this study, we screened for anti-HBV agents using the recombinant HBV expressing NanoLuc (NL) reporter gene (HBV/NL) and our original synthetic heterocyclic compound library. As a result, we identified a synthetic bile acid derivative, SO-145, as a potential novel anti-HBV agent, and investigated its effects in several cellular models of HBV. Treatment of HepG2-NTCP-C4 cells with SO-145 suppressed their NL activity following infection with HBV/NL. SO-145 suppressed HBV replication in PXB-cells infected with HBV genotype D, but did not show any inhibitory effect on HBV replication in Hep38.7-Tet cells. These results suggest that SO-145 specifically inhibits the early phase of the HBV life cycle. In other experiments, SO-145 was also shown to inhibit hepatitis D virus infection. Immunofluorescence analysis using fluorescent-labeled preS1 peptide revealed that SO-145 does not inhibit the preS1 attachment to the NTCP, but does markedly inhibit the HBV/preS1 internalization. Moreover, SO-145 does not inhibit the bile acid uptake facilitated by NTCP. Further mechanistic analysis suggested that SO-145 interferes with the NTCP oligomerization. Taken together, these results suggest that SO-145 inhibits HBV entry into hepatocytes by interfering with the NTCP oligomerization.

BACKGROUND AND AIMS: HBV leads to severe liver diseases, such as cirrhosis and HCC. Identification of host factors that regulate HBV replication can provide new therapeutic targets. The discovery of sodium taurocholate cotransporting polypeptide (NTCP) as an HBV entry receptor has enabled the establishment of hepatic cell lines for analyzing HBV infection and propagation. Using this new system, studies aimed at identifying host factors that regulate HBV propagation have increased. APPROACH AND RESULTS: We established an HBV-based-reporter gene expression system that mimics HBV replication from transcription to virus egress. Using this approach, we screened 1827 Food and Drug Administration-approved compounds and identified glycogen synthase kinase 3 (GSK3)alpha/beta inhibitors, including AZD1080, CHIR-98014, CHIR-98021, BIO, and AZD2858, as anti-HBV compounds. These compounds suppressed HBeAg and HBsAg production in HBV-infected human primary hepatocytes. Proteome analysis revealed that GSK3alpha/beta phosphorylated forkhead box K1/2 (FOXK1/2)s. A double-knockout of FOXK1/2 in HBV-infected HepG2-NTCP cells reduced HBeAg and HBsAg production. The rescue of FOXK2 expression, but not FOXK1 expression, in FOXK1/2-double-knockout cells restored HBeAg and HBsAg production. Importantly, phosphorylation of FOXK2 at Ser 424 is required for GSK3alpha/beta-mediated HBeAg and HBsAg production. We observed the binding of FOXK2 to HBV DNA in HepG2-NTCP cells. CONCLUSIONS: Our recombinant HBV-based screening system enables the discovery of new targets. Using our approach, we identified GSK3 inhibitors as potential anti-HBV agents.

Although antimicrobial peptides have been shown to inactivate viruses through disruption of their viral envelopes, clinical use of such peptides has been hampered by a number of factors, especially their enzymatically unstable structures. To overcome the shortcomings of antimicrobial peptides, peptoids (sequence-specific N-substituted glycine oligomers) mimicking antimicrobial peptides have been developed. We aimed to demonstrate the antiviral effects of antimicrobial peptoids against hepatitis B virus (HBV) in cell culture. The anti-HBV activity of antimicrobial peptoids was screened and evaluated in an infection system involving the HBV reporter virus and HepG2.2.15-derived HBV. By screening with the HBV reporter virus infection system, three (TM1, TM4, and TM19) of 12 peptoids were identified as reducing the infectivity of HBV, though they did not alter the production levels of HBs antigen in cell culture. These peptoids were not cytotoxic at the evaluated concentrations. Among these peptoids, TM19 was confirmed to reduce HBV infection most potently in a HepG2.2.15-derived HBV infection system that closely demonstrates authentic HBV infection. In cell culture, the most effective administration of TM19 was virus treatment at the infection step, but the reduction in HBV infectivity by pre-treatment or post-treatment of cells with TM19 was minimal. The disrupting effect of TM19 targeting infectious viral particles was clarified in iodixanol density gradient analysis. In conclusion, the peptoid TM19 was identified as a potent inhibitor of HBV. This peptoid prevents HBV infection by disrupting viral particles and is a candidate for a new class of anti-HBV reagents.