A recombinant plasmid (pSVS dhfr) encoding the pre-S region and the S gene of human hepatitis B virus (HBV) and murine dihydrofolate reductase (DHFR) cDNA has been used for the transfection of Chinese hamster ovary (CHO) DHFR-cells. Selection of clones resistant to methotrexate has permitted amplification of HBV sequences and an increase in production of hepatitis B surface antigen (HBsAg).
The hepatitis B virus (HBV) envelope protein carrying the surface antigen (HBsAg) is assembled with cellular lipids in mammalian cells into empty viral envelopes. In a study to evaluate the capacity of such particles to present foreign peptide sequences in a biologically active form, in-phase insertions were created in the S gene encoding the major envelope protein. One of the sequences inserted was a synthetic DNA fragment encoding a poliovirus neutralization epitope. Mammalian cells expressing the modified gene secreted hybrid particles closely resembling authentic 22-nanometer HBsAg particles. These particles reacted with a poliovirus-specific monoclonal antibody and induced neutralizing antibodies against poliovirus. The results indicate that empty viral envelopes of HBV may provide a means for the presentation of peptide sequences and for their export from mammalian cells.
DNA from a human adult was fragmented by partial digestion with restriction endonuclease EcoRI and cloned in λ Charon 4A. Clone C15, with a human DNA insert of 17 × 103 bases, was identified as containg a gene for the fibroblast, interferon, interferon β1. Restriction mapping shows that this gene, located on a 1840‐base EcoRI fragment, is not interrupted by introns. Moreover, we show that this human genomic DNA fragment is able to direct the synthesis of active human interferon β1 in Escherichia coli. Interferon activity of up to 7 × 106 U/1 was recovered from phage lysates by chromatography on CiBacron blue–Sepharose, and had the same immunological properties and species specificity as interferon produced by human fibroblasts.
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