Cell-specific expression of enhanced green fluorescence protein under the control of neuropeptide gene promoters in the brain of the silkworm, Bombyx mori, using Bombyx mori nucleopolyhedrovirus-derived vectors.

Using the larvae of the silkworm, Bombyx mori, we examined the baculovirus expression vector system for the expression of the enhanced green fluorescence protein (EGFP) gene under the control of several gene promoters in vivo. To investigate the gene-delivery efficiency of the baculovirus into various larval tissues, we constructed two recombinant baculoviruses carrying the EGFP gene downstream of the Drosophila melanogaster hsp70 gene promoter from B. mori nucleopolyhedrovirus (BmNPV) and Autographa californica nucleopolyhedrovirus (AcNPV). After injection of these recombinant baculoviruses into newly ecdysed 5th instar larvae, hsp70::EGFP-BmNPV, but not hsp70::EGFP-AcNPV, caused intense expression of EGFP not only in various non-neural tissues, but also in the neural organs including the brain 5 days postinfection. To investigate the cell-specific expression in the brain, we constructed recombinant C4/B3::EGFP-BmNPV and PTTH::EGFP-BmNPV which carry the EGFP gene under the control of bombyxin B3 and prothoracicotropic hormone (PTTH) gene promoters, respectively. Injection of these recombinant baculoviruses caused specific expression of EGFP with a high gene-expression efficiency in the neurosecretory cells of the brain depending on the neurohormone gene promoters. Present results indicate that this in vivo gene-expression system mediated by the baculovirus can serve as an efficient system permitting gene delivery into neural tissues in insects.