IMMEDIATE-EARLY BACULOVIRUS VECTORS FOR FOREIGN GENE-EXPRESSION IN TRANSFORMED OR INFECTED INSECT CELLS

Baculovirus expression vectors are used routinely for foreign gene exp ression and are under intense development as improved biological pesti cides. Conventional baculovirus expression vectors are recombinant vir uses that can express a foreign gene in insect cells under the control of the polyhedrin promoter, which provides high-level transcription d uring the very late phase of infection. For some applications, includi ng foreign glycoprotein production and insect pest control, it might b e advantageous to have baculovirus vectors that could express foreign gene products in uninfected cells or earlier after infection. To fulfi ll this need, we have constructed a new set of plasmids that can be us ed to clone and express foreign genes under the control of a baculovir us iel promoter, which is active in uninfected insect cells and throug hout infection. We used a subset of these new plasmids to isolate reco mbinant baculoviruses containing various foreign genes and compared ex pression of these genes by the resulting immediate-early baculovirus v ectors and by conventional baculovirus vectors. As expected, the immed iate-early vectors began to express each foreign gene earlier in infec tion but, by 36-48 h postinfection, the conventional vectors had produ ced more of each foreign protein. Conventional baculovirus vectors als o produced more enzymatic activity from two different procaryotic gene s than the immediate-early baculovirus vectors. However, immediate-ear ly vectors produced as much or more enzymatic activity from two differ ent eucaryotic genes encoding secretory pathway proteins than the conv entional vectors, even at 48 h postinfection. Hence, this report descr ibes a new set of plasmids that can be used to clone and express forei gn genes under the control of the baculovirus iel promoter and suggest s that immediate-early baculovirus vectors might be as useful as conve ntional baculovirus expression vectors for producing biologically acti ve eucaryotic secretory pathway proteins. (C) 1996 Academic Press, Inc .