No abstract

Hepatitis B virus (HBV)infection is a major health concern worldwide. To prevent HBV-related mortality, elimination of viral proteins is considered the ultimate goal of HBV treatment; however, currently available nucleos(t)ide analogs rarely achieve this goal, as viral transcription from episomal viral covalently closed circular DNA (cccDNA) is not prevented. HBV regulatory protein X was recently found to target the protein structural maintenance of chromosomes 5/6 (Smc5/6) for ubiquitination and degradation by DDB1-CUL4-ROC1 E3 ligase, resulting in enhanced viral transcription from cccDNA. This ubiquitin-dependent proteasomal pathway requires an additional ubiquitinlike protein for activation, neuronal precursor cell-expressed developmentally down-regulated protein 8 (NEDD8). Here, we show that pevonedistat, a NEDD8-activating enzyme inhibitor, works efficiently as an antiviral agent. Pevonedistat significantly restored Smc5/6 protein levels and suppressed viral transcription and protein production in the HBV minicircle system in in vitro HBV replication models and in human primary hepatocytes infected naturally with HBV. Conclusion: These results indicate that pevonedistat is a promising compound to treat chronic HBV infection. (Hepatology 2019;69:1903-1915).

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MICA/B proteins are expressed on the surface of various types of stressed cells, including cancer cells. Cytotoxic lymphocytes expressing natural killer group 2D (NKG2D) receptor recognize MICA/B and eliminate the cells. However, cancer cells evade such immune recognition by inducing proteolytic shedding of MICA/B proteins. Therefore, preventing the shedding of MICA/B proteins could enhance antitumor immunity. Here, by screening a protease inhibitor library, we found that the fatty-acid amide hydrolase (FAAH) inhibitor, URB597, suppresses the shedding of MICA/B. URB597 significantly reduced the soluble MICA level in culture medium and increased the MICA level on the surface of cancer cells. The effect was indirect, being mediated by increased expression of tissue inhibitor of metalloproteinases 3 (TIMP3). Knockdown of TIMP3 expression reversed the effect of URB597, confirming that TIMP3 is required for the MICA shedding inhibition by URB597. In contrast, FAAH overexpression reduced TIMP3 expression and the cell-surface MICA level and increased the soluble MICA level. These results suggest that inhibition of FAAH could prevent human cancer cell evasion of immune-mediated clearance.

Although nucleos(t)ide analogs and interferons suppress hepatitis B virus (HBV) replication, they must be taken continuously and have a low response rate. Therefore, therapeutics for HBV with novel modes of action are needed. Humanized virus-suppressing factor (hzVSF) is a monoclonal antibody against vimentin that exhibits broad-spectrum antiviral activity. Here, hzVSF significantly inhibited HBV infection. Although hzVSF inhibited HBV RNA production, it did not affect viral transcription from minicircle DNA mimicking covalently closed circular DNA. Additionally, hzVSF did not inhibit viral protein or DNA release from infected cells. Rather, hzVSF inhibited the cell entry of viral preS1 peptides, possibly by altering intracellular vimentin localization, which is important for HBV cell entry. These results suggest that hzVSF has therapeutic potential for HBV infection with a novel mode of action.