Identification of HBsAg-specific antibodies from a mammalian cell displayed full-length human antibody library of healthy immunized donor

Hepatitis B immunoglobulin （HBIG） is important in the management of hepatitis B virus （HBV） infection. Aiming to develop recombinant monoclona# antibodies as an alternative to HBIG, we report the successful identification of HBV surface antigen （HBsAg）-specific antibodies from a full-length human antibody library displayed on mammalian cell surface. Using total RNA of peripheral blood mononuclear cells of a natively immunized donor as template, the antibody repertoire was amplified. Combining four-way ligation and the FIp recombinase-mediated integration （FIp-ln） system, we constructed a mammalian cell-based, fully human, full-length antibody display library in which each cell displayed only one kind of antibody molecule. By screening the cell library using fluorescence-activated cell sorting （FACS）, eight cell clones that displayed HBsAg-specific antibodies on cell surfaces were identified. DNA sequence analysis of the antibody genes revealed three unique antibodies. FACS data indicated that fluorescent strength of expression （FSE）, fluorescent strength of binding （FSB） and relative binding ability （RBA） were all different among them. These results demonstrated that by using our antibody mammalian display and screening platform, we can successfully identify antigen-specific antibodies from an immunized full-length antibody library. Therefore, this platform is very useful for the development of therapeutic antibodies.

HBsAg-specific CD8^(+)T cells as an indispensable trigger to induce murine hepatocellular carcinoma

Hepatitis B virus(HBV)-associated hepatocellular carcinoma(HCC)is mediated by an inappropriate attack by HBV-specific T cells in patients.However,this immunopathogenic process has not been clarified because of the lack of a suitable animal model.Here,we used immunocompetent Fah^(-/-)mice as the recipients in the adoptive transfer of HBsAg^(+)hepatocytes from HBs-Tg mice to replace the recipient hepatocytes(HBs-HepR).HBs-HepR mice exhitited persistent HBsAg expression with chronic hepatitis and eventually developed HCC with a prevalence of 100%.HBsAg-specific CD8^(+)T cells were generated and specifically and continuously induced hepatocyte apoptosis with progressive chronic inflammation,and the depletion of CD8^(+)T cells or their deficiency prevented HCC,which could then be reproduced by the transfer of HBsAg-specific CD8^(+)T cells.In summary,our results demonstrated that CD8^(+)T cells plays a critical role in HBsAg-driven inflammtion and HCC tumorigenesis.