Baculovirus-mediated expression of bacterial genes in dipteran and mammalian cells.

A recombinant baculovirus containing the Escherichia coli chloramphenicol acetyltransferase (CAT) gene under the control of the Rous sarcoma virus long terminal repeat promoter and the E. coli beta-galactosidase gene under the control of the very late baculoviral polyhedrin promoter was used to determine if Autographa californica nuclear polyhedrosis virus, a baculovirus of Lepidoptera, can enter and express viral DNA in dipteran (Drosophila sp.) and mammalian (Mus sp.) cells that are considered refractory to baculovirus replication. Following infection, CAT gene expression was observed in both dipteran and mammalian cells, but expression in the mammalian cell line was less than 0.05% of that observed in either dipteran or lepidopteran cells. Although the level of CAT gene expression was similar in permissive lepidopteran and nonpermissive dipteran cells, expression of beta-galactosidase activity from the late polyhedrin promoter in dipteran or mammalian cells was less than 0.3% of the levels observed in lepidopteran cells. These results indicate that foreign gene expression in nonpermissive cells is promoter dependent and that late viral gene expression is restricted in these cells. The Rous sarcoma virus long terminal repeat allows substantial CAT gene expression in both a D. melanogaster cell line and Aedes aegypti midgut cells. Baculovirus DNA undergoes a limited number of replications in Drosophila cells. The results are relevant to baculovirus host range, the safety of baculoviruses as pesticides, and the development of baculovirus pesticides with expanded host ranges.