Development of Recombinant Infectious Hepatitis E Virus Harboring the nanoKAZ Gene and Its Application in Drug Screening.

Hepatitis E virus (HEV) is a quasi-enveloped virus with a single-stranded positive-sense RNA genome belonging to the family Hepeviridae. Studies of the molecular aspects of HEV and drug screening have benefited from the discovery of bioluminescent reporter genes. However, the stability of large foreign genes is difficult to maintain after insertion into the viral genome. Currently, ribavirin is used to treat HEV-infected patients who require antiviral therapy. This has several major drawbacks. Thus, the development of novel anti-HEV drugs is of great importance. We developed a system consisting of recombinant infectious HEV harboring a small luciferase gene (nanoKAZ) in the hypervariable region (HVR) of the open reading frame 1 (ORF1) (HEV-nanoKAZ). It replicated efficiently in cultured cells, was genetically stable, and had morphological characteristics similar to those of the parental virus. Both membrane-associated (eHEV-nanoKAZ) and membrane-unassociated (neHEV-nanoKAZ) particles were infectious. HEV particles circulating in the bloodstream and attaching to hepatocytes in HEV-infected patients are membrane-associated; thus, eHEV-nanoKAZ was applied in drug screening. The eHEV-nanoKAZ system covers at least the inhibitor of HEV entry and inhibitor of HEV RNA replication. Four drugs with anti-HEV activity were identified. Their effectiveness in cultured cells was confirmed in naive and HEV-producing PLC/PRF/5 cells. Two hit drugs (azithromycin and ritonavir) strongly inhibited HEV production in culture supernatants, as well as intracellular expression of ORF2 protein, and may therefore be candidate novel anti-HEV drugs. The HEV-nanoKAZ system was developed and applied in drug screening and is expected to be useful for investigating the HEV life cycle. IMPORTANCE Bioluminescent reporter viruses are essential tools in molecular virological research. They have been widely used to investigate viral life cycles and in the development of antiviral drugs. For drug screening, the use of a bioluminescent reporter virus helps shorten the time required to perform the assay. A system, consisting of recombinant infectious HEV harboring the nanoKAZ gene in the HVR of ORF1 (HEV-nanoKAZ), was developed in this study and was successfully applied to drug screening in which four hit drugs with anti-HEV activity were identified. The results of this study provide evidence supporting the use of this system in more variable HEV studies. In addition, both forms of viral particles (eHEV-nanoKAZ and neHEV-nanoKAZ) are infectious, which will enable their application in HEV studies requiring both forms of viral particles, such as in the investigation of unknown HEV receptors and the elucidation of host factors important for HEV entry.

Hypoxia-induced des-gamma-carboxy prothrombin production in hepatocellular carcinoma.

Des-gamma-carboxy prothrombin (DCP) is an established HCC tumor marker, but the precise mechanism of its production is still unclear. Recently, we demonstrated that cytoskeletal changes during epithelial-to-fibroblastoid conversion (EFC) or epithelial mesenchymal transition (EMT) induced by chemicals plays a critical mechanistic role in DCP production via impairment in vitamin K uptake. Our proposed mechanism of DCP production is consistent with substantial clinical evidence. Supplementary vitamin K2 analogues reduced serum DCP levels in hepatocellular carcinoma (HCC) patients. HCC patients with high serum DCP are associated with vascular invasion, metastasis and tumor recurrence. On the other hand, hypoxia has been reported to induce EMT or cytoskeletal changes. Therefore, we examined whether hypoxia induced DCP production during EFC or EMT in HCC cells. Indeed, hypoxic stimulation induced hepatoma cell lines (HepG2 or PLC/PRF/5 cells) to undergo EFC or EMT and these cells produced DCP. Immunofluorescence study demonstrated that hypoxic stimulation impaired labeled low-density lipoprotein uptake, which was a surrogate for vitamin K uptake. In addition, fine filamentous actin network, which has crucial role for clathrin-mediated endocytosis of vitamin K, was disrupted in DCP producing cells by hypoxic stimulation. Thus, hypoxic stimulation induced HCC cells to produce DCP in the same mechanism as chemicals. Furthermore, immunohistochemical study using surgically resected HCC samples showed that a positive staining of nuclear hypoxia inducible factor (HIF)-1alpha was more frequently observed in HCC cells with stronger staining intensity of DCP. Importantly, clinical observations that DCP as an HCC tumor marker was more useful in larger tumors, which is likely to be exposed with hypoxia during tumor development, support our results.

Fulminant sepsis due to anaerobic bacterial infection in immuno-compromised state.

We experienced two autopsy cases of fulminant sepsis due to anaerobes. Case 1: A 67-year-old female with uncontrolled diabetes mellitus (DM) was admitted to a hospital because of sudden onset of mid-abdominal pain. She was diagnosed with infectious colitis and given a laxative and an enema. However, 9h later, her blood pressure suddenly dropped with metabolic acidosis, and she died 20 h after admission. Autopsy revealed massive pneumohemia and a dark-brown colored mucosal surface from the terminal ileum to the sigmoid colon. Histopathological findings were compatible with marginal ischemic colitis. Anaerobes were positive in blood culture. Case 2: A 53-year-old male with alcoholic liver cirrhosis (LC) was found dead in his room. He had been alive 24 h before the discovery, but postmortem changes appeared to accelerate more rapidly than usual cases. Autopsy revealed severe LC with muddy ascites and many Gram-negative rods in several organs. These cases suggest the possibility of sepsis as causes of death, especially in immuno-compromised hosts when unexplained putrefactive changes are seen on forensic autopsy.

An autopsy case of fulminant sepsis due to pneumatosis cystoides intestinalis.

A 67-year-old female with uncontrolled diabetes mellitus (DM) was admitted to a hospital because of sudden onset of mid-abdominal pain. Laboratory data only showed mild elevation of white blood cell counts. She was diagnosed as constipation, and given laxative and enema. However, 9 h after the admission, her blood pressure suddenly went down with developing of metabolic acidosis, and died 20 h after the admission. Forensic autopsy revealed massive pneumohemia in the venous system. Edematous dark-brown colored lesions of mucosal surface were discontinuously observed from terminal ileum to sigmoid colon with bloody ascites. Histopathological findings showed gas cysts and lymphoid cell infiltration within colonic submucosa compatible with pneumatosis cystoides intestinalis (PCI). Anaerobes were positive in blood culture. From the clinical and histological findings, we hypothesized that PCI initially occurred, and intestinal bacterias invaded into vessels through broken mucosal barrier and developed fulminant sepsis. In recent years, anaerobic bacteremia has reemerged as a significant clinical problem due to the increasing number of patients with complex underlying disease such as malignancy, liver cirrhosis, DM and so on. In forensic autopsy anaerobic infection should be considered particularly in immuno-compromised hosts and total judgment from findings would be essential.

Impairment of clathrin-mediated endocytosis via cytoskeletal change by epithelial to fibroblastoid conversion in HepG2 cells: a possible mechanism of des-gamma-carboxy prothrombin production in hepatocellular carcinoma.

Des-gamma-carboxy prothrombin (DCP) has been well established as a hepatocellular carcinoma (HCC) tumor marker. However, the precise mechanism by which HCC cells produce DCP remains unknown. Importantly, DCP is not specific for HCC. For example, vitamin K-deficiency or ingestion of a vitamin K antagonist (warfarin) also leads to DCP production. In addition, supplementary administration of vitamin K2 analogues to HCC patients has led to reduce serum DCP levels. From these observations, we hypothesize that DCP might be produced from HCC cells with functional impairment of vitamin K uptake. Because, as previously reported, the down-regulation of E-cadherin or high serum DCP in HCC patients is associated with a high risk of vascular invasion, intra-hepatic metastasis and tumor recurrence, we examined if HCC cells might produce DCP by epithelial to fibroblastoid conversion (EFC) in vitro. HepG2 cells were induced EFC by tumor promoter, 12-O-tetracanoylphorbol-13-acetate (TPA). DCP production was observed in HepG2 cells that had lost E-cadherin expression in a TPA-dose-dependent manner. The DCP production was inhibited by introducing additional vitamin K2 into the treated cells. In addition, LDL uptake as a surrogate of vitamin K uptake was significantly impaired in TPA-treated HepG2 cells. The cells with impairment of LDL uptake produced DCP. Fat soluble vitamins are taken up into cells through clathrin-mediated endocytosis, in which the dynamic polymerization of F-actin plays a crucial role. We found that HepG2 cells with F-actin rearrangement produced DCP. In addition, latrunculin A, an actin depolymerizer, induced naïve HepG2 cells to produce DCP, confirming that impairment of F-actin polymerization is a key mechanism of DCP production. We showed in vitro that cytoskeletal filament change by EFC is crucial for DCP production in HepG2 cells.