| Budget Amount *help |
¥3,640,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥240,000)
Fiscal Year 2007: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2006: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
In this study, we tried to identify the novel anti-hepatitis B virus (HBV) defense mechanisms in the infected hepatocytes, and the following results were obtained. We first established a culture model of a hepatoma-derived cell line that supports the infection and replication of HBV. For this purpose, HepG2 cells were exposed to 2% DMSO in the presence or absence of 4% PEG and subsequently examined for their susceptibility to HBV infection using the HBV-DNA positive serum of HBV asymptomatic careers. We found that DMSO alone did not enhance the HBV infection of HepG2 cells. However, treatment with DMSO plus PEG resulted in a marked enhancement of HBV replication in HepG2 cells, indicating that DMSO administered with PEG renders HepG2 cells susceptible to infection by HBV that originates from the sera of HBV-infected patients, and allows the replication of this virus. Using this in vitro infection model, we analyzed the expression profiles of various genes in HBV-infected hepatocytes, and identified APOBEC3G as a HBV infection-inducible host gene. To investigate the anti-HBV activity of APOBEC3G, we tested whether APOBEC3G inhibits viral replication in HepG2 cells infected with serum-derived HBV. We detected substantial levels of HBV DNA synthesis in the control HepG2 cells seven days after infection with HBV. In contrast, cells expressing either exogenous wild-type or mutant APOBEC3G had levels of HBV DNA significantly lower than those of the control cells. Moreover, a number of DNA mutations were detected in HBV genomes derived from cells that expressed APOBEC3G. Taken together, these data indicate that the anti-HBV activity of APOBEC3G might be attributable to two different mechanisms : an inhibitory effect on HBV DNA synthesis, and an editing activity that generates DNA mutations in the viral genome.
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