岡本 宏明

A 56-year-old man receiving immunosuppressive therapy with methotrexate (MTX) for a T-cell lymphoproliferative disorder developed acute hepatitis caused by hepatitis E virus (HEV). Persistent HEV viremia was observed, and the patient was diagnosed with chronic HEV infection based on the continued presence of HEV RNA in both serum (106-107 copies/mL) and feces (~ 109 copies/mL in 15% suspensions) 6 months after the initial infection. A 12-week course of ribavirin (RBV) therapy, combined with gradual tapering of MTX, resulted in undetectable HEV RNA levels in serum and feces at the end of the RBV treatment. However, 6 months after completion of RBV therapy and MTX cessation, HEV RNA reappeared at low levels in serum (10 copies/mL) and feces (~ 103 copies/mL in 15% suspensions). This low-level viremia persisted for approximately 4 months without any clinical symptoms or additional treatment. Eventually, HEV RNA became spontaneously undetectable in both serum and feces, and the patient was considered cured based on sustained HEV RNA negativity 1129 days after the onset of hepatitis. This case highlights the importance of extended follow-up-beyond the standard 6 months-when assessing the viral clearance in HEV-infected patients following antiviral therapy.

Hepatitis A virus (HAV) infection sometimes results in the occurrence of acute liver failure and acute-on-chronic liver failure (ACLF), which is often fatal, especially in patients with diabetes mellitus or elderly individuals. ACLF is observed in patients with cirrhosis who occasionally have zinc deficiency. However, effective drugs for hepatitis A are currently unavailable. Glucose-regulated protein 78 (GRP78) is an antiviral agent that has been reported to prevent HAV replication. The effects of zinc acetate on HAV HA11-1299 genotype IIIA replication and changes in GRP78 levels in human hepatocytes with or without HAV infection were examined. Zinc acetate inhibited HAV HA11-1299 genotype IIIA replication in both Huh7 and GL37 cells. Zinc acetate also inhibited HAV replication in both low- and high-glucose media. Zinc acetate increased the expression of GRP78, in response to HAV replication. The combination of zinc acetate with ribavirin led to greater suppression of both HAV HA11-1299 genotype IIIA and HAV HM175/18f genotype IB replication in Huh7 cells than that of ribavirin alone. In conclusion, zinc acetate inhibits HAV replication in accompany with the elevation of GRP78 expression without causing cellular toxicity. Zinc compounds may be useful for the treatment of ACLF caused by HAV infection.

Hepatitis E virus (HEV) infection is an emerging infectious disease. HEV-1 and HEV-2 infect humans through contaminated water and foods, mainly in developing countries. HEV-3 and HEV-4 also infect humans through contaminated food and are thought to be zoonotic infections occurring in both developing and developed countries. A vaccine for hepatitis E is licensed in only limited countries. The inactivation of infectious HEV is very important to ensure the safety of drinking water and foods. HEV-3 and HEV-4 RNA have been detected in some pig liver products, and it is possible that these foods may represent an infectious source of HEV. In this article, previous publications on the heat inactivation and heat stability of HEV are collected, and we discuss the present assessment of the heat inactivation of HEV. The thermal stability of HEV infection in cell culture systems and pig bioassays has been demonstrated, while the efficacy of the method of thermal inactivation using plasma products has not yet been established. Here, we propose that the treatment of HEV-contaminated foods at 95 °C for 10 min is one of the safest options for the inactivation of HEV.

Hepatitis E virus (HEV) is a positive-sense, single-stranded RNA virus that poses a significant public health risk, yet its study is hindered by the complexity of conventional RNA-based reverse genetics systems. These systems require multiple steps, including genome cloning, in vitro transcription, and capping, making them labor-intensive and susceptible to RNA degradation. In this study, we developed a single-step, plasmid-based HEV expression system that enabled direct intracellular transcription of the full-length HEV genome under a cytomegalovirus immediate-early (CMV-IE) promoter. The viral genome was flanked by hammerhead (HH) and hepatitis delta virus (HDV) ribozymes to ensure precise self-cleavage and the generation of authentic 5' and 3' termini. This system successfully supported HEV genome replication, viral protein expression, and progeny virion production at levels comparable to those obtained using in vitro-transcribed, capped HEV RNA. Additionally, a genetic marker introduced into the plasmid construct was stably retained in progeny virions, demonstrating the feasibility of targeted genetic modifications. However, plasmid-derived HEV exhibited delayed replication kinetics, likely due to the absence of an immediate 5' cap. Attempts to enhance capping efficiency through co-expression of the vaccinia virus capping enzyme failed to improve HEV replication, suggesting that alternative strategies, such as optimizing the promoter design for capping, may be required. This plasmid-based HEV reverse genetics system simplifies the study of HEV replication and pathogenesis and provides a versatile platform for the genetic engineering of the HEV genome.

To cure hepatitis B virus (HBV) infection, it is essential to elucidate the function of hepatocyte host factors in regulating the viral life cycle. Signaling and transcription activator of transcription (STAT)1 play important roles in immune responses, but STAT1-independent pathways have also been shown to have important biological reactivity. Using an in vitro HBV infection assay system, the current study aimed to investigate the STAT1-independent host factors that contribute to the control of viral infection by comprehensive functional screening. The in vitro HBV infection system was established using primary human hepatocytes (PXB cells) infected with HBV derived from a plasmid containing the 1.3-mer HBV genome. Comprehensive functional studies were performed using small interfering RNA (siRNA) and vector transfection and analyzed using microarrays. Knockdown of STAT1 increased viral products in HBV-transfected HepG2 cells, but decreased in HBV-infected PXB cells. RNA microarray was performed using HBV-infected PXB cells with STAT1 knockdown. Fumarylacetoacetate hydrolase (FAH) was extracted by siRNA of genes in PXB cells altered by STAT1 knockdown. Transfection of FAH inhibited HBV replication. Dimethyl fumarate (DMF), the methyl ester of FAH metabolite, showed antiviral effects by inducing autophagy and anti-HBV-related genes. Independently of STAT1, FAH was identified as a host factor that contributes to the control of viral infection, and its metabolite, DMF, exhibited antiviral activity. These results suggest that the novel host factor FAH and its metabolites may be an innovative therapeutic strategy to control the HBV life cycle.