Expression of functional recombinant antibody molecules in insect cell expression systems

Recombinant single-chain variable-fragment molecules (scFv) were constructe d from a cell line expressing a monoclonal antibody against African cassava mosaic virus (ACMV) and expressed in Escherichia coli. DNA sequences that encoded the scFv were manipulated to allow scFv expression in insect cell l ines. A recombinant baculovirus containing the scFv cDNA was constructed an d large amounts of scFv were produced in each of three insect cell lines in fected with the baculovirus. However, the scFv were not secreted into the m edium by any of the cell lines despite the scFv having been linked to a hon eybee melittin leader sequence. The same scFv cDNA construct was introduced into Drosophila DS2 cells and a stable recombinant cell line was obtained that produced scFv that was secreted into the medium. Culture medium contai ning the scFv was used directly in enzyme-linked immunosorbent assay (ELISA ) tests to detect ACMV in plant tissues. Another construct that encoded the CK domain of human IgG was fused to the C-terminus of the scFv that was pr oduced and expressed in Drosophila cells. This scFv derivative also accumul ated in the medium and was more active in ELISA than scFv lacking the C kap pa domain. (C) 2000 Academic Press.