Takashi Kimura

HBx protein is indispensable for development of viraemia in human hepatocyte chimeric mice.

The non-structural X protein, HBx, of hepatitis B virus (HBV) is assumed to play an important role in HBV replication. Woodchuck hepatitis virus X protein is indispensable for virus replication, but the duck hepatitis B virus X protein is not. In this study, we investigated whether the HBx protein is indispensable for HBV replication in vivo using human hepatocyte chimeric mice. HBx-deficient (HBx-def) HBV was generated in HepG2 cells by transfection with an overlength HBV genome. Human hepatocyte chimeric mice were infected with HBx-def HBV with or without hepatic HBx expression by hydrodynamic injection of HBx expression plasmids. Serum virus levels and HBV sequences were determined with mice sera. The generated HBx-def HBV peaked in the sucrose density gradient at points equivalent to the generated HBV wild type and the virus in a patients serum. HBx-def HBV-injected mice developed measurable viraemia only in continuously HBx-expressed liver. HBV DNA in the mouse serum increased up to 9 log(10) copies ml(-1) and the viraemia persisted for more than 2 months. Strikingly, all revertant viruses had nucleotide substitutions that enabled the virus to produce the HBx protein. It was concluded that the HBx protein is indispensable for HBV replication and could be a target for antiviral therapy.

Establishment of an infectious genotype 1b hepatitis C virus clone in human hepatocyte chimeric mice.

The establishment of clonal infection of hepatitis C virus (HCV) in a small-animal model is important for the analysis of HCV virology. A previous study developed models of molecularly cloned genotype 1a and 2a HCV infection using human hepatocyte-transplanted chimeric mice. This study developed a new model of molecularly cloned genotype 1b HCV infection. A full-length genotype 1b HCV genome, HCV-KT9, was cloned from a serum sample from a patient with severe acute hepatitis. The chimeric mice were inoculated intrahepatically with in vitro-transcribed HCV-KT9 RNA. Inoculated mice developed viraemia at 2 weeks post-infection, and this persisted for more than 6 weeks. Passage experiments indicated that the sera of these mice contained infectious HCV. Interestingly, a similar clone, HCV-KT1, in which the poly(U/UC) tract was 29 nt shorter than in HCV-KT9, showed poorer in vivo infectivity and replication ability. An in vitro study showed that no virus was produced in the culture medium from HCV-KT9-transfected cells. In conclusion, this study developed a genetically engineered genotype 1b HCV-infected mouse. This mouse model will be useful for the study of HCV virology, particularly the mechanism underlying the variable resistance of HCV genotypes to interferon therapy.

G to A hypermutation of TT virus

APOBEC3 proteins function as part of innate antiviral immunity and induce G to A hypermutation in retroviruses and hepatitis B virus (HBV) genomes. Whether APOBEC3 proteins affect viruses that replicate without a reverse transcription step is unknown. TT virus (TTV), known to present in serum of healthy individuals and HBV carriers, has a single-stranded circular DNA genome and replicates without reverse transcription. In this study, we examined 67 blood samples obtained from healthy individuals and HBV carriers and observed G to A hypermutation of genomes of TTV in both healthy individuals and HBV carriers. During ALT flare-up in HBV carriers, G to A hypermutation of HBV increased, but TTV genomes significantly decreased in number and hypermutated TTV genomes became undetectable. Our results show that hypermutated TTV exist in healthy individuals and HBV carriers and that TTV genomes were susceptible to immune reaction directed to HBV by interacting with APOBEC3 proteins.

G-to-A Hypermutation in Hepatitis B Virus (HBV) and Clinical Course of Patients with Chronic HBV Infection

BACKGROUND The apolipoprotein B messenger RNA editing enzyme, catalytic polypeptide-like family of cytidine deaminases induce G-to-A hypermutation in hepatitis B virus (HBV) genomes and play a role in innate antiviral immunity. The clinical relevance of this protein family is unknown. METHODS We analyzed 33 instances in which 17 patients with chronic HBV infection experienced >2 increases of >100 IU/L in alanine aminotransferase (ALT) level; we used a quantitative differential DNA denaturation polymerase chain reaction assay to quantify the hypermutated HBV genomes observed during 21 of these 33 increases in ALT level. RESULTS Of the 9 increases in ALT level that involved a >5-fold increase (relative to basal levels) in the number of hypermutated genomes observed, 8 were associated with a >2-log reduction in plasma HBV DNA level. In contrast, a corresponding decrease in plasma HBV DNA level was observed for only 1 of the 12 increases in ALT level that did not involve an increase in the number of hypermutated genomes ( P<.001). Hepatitis B e antigen clearance was often observed in patients who experienced an increase in the number of hypermutated genomes. Interferon treatment induced hypermutation in HBV genomes in an animal model. However, there was no apparent increase in the number of hypermutated genomes among the majority of patients who received interferon therapy, probably because the number of hypermutated genomes had already increased prior to the initiation of therapy. CONCLUSION Our results suggest that a marked increase in the number of hypermutated genomes represents a strong immunological host response against the virus and is predictive of hepatitis B e antigen clearance and plasma HBV DNA level reduction.

A Variational Sum-Rule Approach to Collective Excitations of a Trapped Bose-Einstein Condensate.

It is found that combining an excitation-energy sum rule with Fetters trial wave function gives almost exact low-lying collective-mode frequencies of a trapped Bose-Einstein condensate at zero temperature.

The first Japanese case of COACH syndrome

COACH syndrome is a disorder characterized by hypoplasia of cerebellar vermis, oligophrenia, congenital ataxia, coloboma and hepatic fibrosis, and 21 cases have been reported to date. Here we describe the first Japanese case of COACH syndrome, who was diagnosed at the age of 37 years and never progressed to liver failure. The patient was found to have delayed developmental milestones at the age of 5 months and mental retardation at the age of 7 years. She had been treated for hepatopathy of unknown origin from the age of 22 years. She was admitted to Hiroshima University Hospital at the age of 37 years after the identification of esophageal varices on a routine upper endoscopy. Computed tomography of the abdomen revealed portal hypertension and splenomegaly, and liver biopsy showed liver fibrosis. In addition, she had coordination disorder and dysarthria. Brain magnetic resonance images revealed hypoplasia of cerebellar vermis. The final diagnosis was COACH syndrome. She underwent endoscopic injection sclerotherapy for esophageal varices. From that point until her death from ovarian cancer at the age of 41 years, the liver function tests were stable without an episode of hematemesis. Physicians should be aware of COACH syndrome when they examine young patients who present with hepatopathy, portal hypertension of unknown origin and cerebellar ataxia.