Research Theme :Analyses of Molecular Mechanisms of Viral Diseases

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The contribution of blood transfusion and blood products to modern medicine is of immeasurable importance; however, patients are constantly exposed to infectious diseases or immunological side effects through these measures. A typical example of such an event is infection by hepatitis C virus (HCV). Recent data shows that there are very large numbers of patients suffering from hepatitis C infection worldwide; indeed, more than 2 million cases of HCV infection are currently reported in Japan. In addition, a clear correlation between HCV infection and the development of hepatocellular carcinoma has been reported. Therefore, it is critical to develop prophylaxis to prevent the onset of disease in HCV carriers. A significant bottleneck in HCV research is the lack of robust and reliable cell culture system that is capable of facilitating efficient viral replication. In this research project, our goal is to achieve the following objectives.

1) Determination of the entry and signal receptors for HCV

Previous research has indicated the existence of protein receptor(s) which facilitates HCV pseudotype infection on the surface of human liver cells. Cloning such receptor molecules from hepatic cells is our next target. Furthermore, recent studies suggest that HCV proteins may influence the activation of the innate immune system, suppress the activation of the adaptive immune system, and cause persistent infection. We utilize HCV pseudotype virus and Toll-like receptor (TLR) knockout mice, developed by Dr. S. Akira, and analyze the interactions between HCV envelope proteins (E1 and E2) and TLRs.

2) Analysis of the relationship between HCV core protein and hepatic carcinogenesis

HCV core protein plays a crucial role in viral particle assembly and in regulating various host functions, which results in initiation of hepatocellular carcinoma. We have previously reported that the core protein specifically binds to PA28?, a proteasome activator, and we now aim to analyze carcinogenesis mediated by the interaction between proteasomes and viral proteins.

3) Analysis of HCV maturation

We have found a specific binding between HCV core protein and cytoplasmic domain of E1. We will determine the mechanisms of interaction of core and E1 proteins and virion assembly. 4) Development of novel viral vectors

Gene expression technology is a powerful tool for investigating viruses which do not propagate in culture cells, including HCV. Baculovirus has been thought to infect only arthropods; however, recent studies showed that it can infect mammals and express foreign genes. In addition, we have demonstrated that baculovirus genome elicits innate immunity through TLR9. We plan to develop unique gene delivery and vaccine vectors utilizing this feature of baculovirus, and explore their application in the merging field of microbiology and immunology.

Research Theme: Investigations of the entry receptor and signal receptor for HCV and analysis of HCV-mediated hepatic carcinogenesis, specifically in terms of the interaction between proteasomes and viral proteins. Furthermore, we aim to elucidate the mechanism of HCV maturation by focusing on the viral interaction with E1 protein. Finally, our aim is to develop novel baculo virus vectors, and explore a wide spectrum of their application in the merging field of microbiology and immunology.