Use of early baculovirus promoters for continuous expression and efficient processing of foreign gene products in stably transformed lepidopteran cells.

Baculoviruses are currently used as vectors for the transient high-level expression of foreign gene products in insect cells. In this study, we demonstrate that baculoviruses can also be made to continuously express a foreign gene product by using the promoter from IE1, an immediate early viral gene, to produce stably-transformed insect cells. This approach gave levels of foreign gene expression lower than those usually obtained with the lytic baculovirus expression vector system. Expression, however, was continuous and stable, and a complex human glycoprotein (tissue plasminogen activator) was processed more efficiently. We conclude that stable transformation is a feasible approach for baculovirus-mediated foreign gene expression in lepidopteran cells, particularly for products that are relatively poorly-expressed and/or processed in lytically infected cells.