CHAPTER 23 - Baculoviruses for Foreign Gene Expression in Insect Cells

Abstract

The production of biologically active proteins from cloned eukaryotic genes requires expression of the genes in a eukaryotic cell for the protein to adopt the correct three-dimensional structure or for appropriate posttranslational modifications to occur. This chapter provides an overview on the use of baculoviruses for foreign gene expression in insect cells. Baculoviruses have been developed as helper-independent virus vectors for high-level expression of foreign genes in insect cells. The rapid adoption of these vector systems by university and industrial laboratories may be attributed to the ease, rapidity, and success in achieving substantial production of a variety of biologically active foreign proteins. Applications to date include the expression of mammalian growth factors, immune system modulators, and viral antigens for vaccine production, oncogenes, and gene regulatory proteins. The approach that is generally employed to construct a recombinant baculovirus for high-level foreign gene expression is to ligate a cDNA of the foreign gene into a plasmid DNA carrying a portion of the viral DNA so that the cDNA is under the control of a strong viral promoter known as the polyhedrin promoter. To obtain a recombinant baculovirus carrying this foreign gene, the recombinant plasmid is co-transfected with wild-type baculovirus DNA into permissive cells. Cell-mediated recombination, between homologous sequences of the viral and plasmid DNA, results in the replacement of the polyhedrin gene of wild-type viral DNA with plasmid sequences containing the foreign cDNA. The polyhedrin gene is nonessential for viral replication in cell culture so that recombinant viruses can be propagated in a helper-independent fashion.