FURTHER DEVELOPMENT OF A RECOMBINANT BACULOVIRUS INSECTICIDE EXPRESSING THE ENZYME JUVENILE-HORMONE ESTERASE FROM HELIOTHIS-VIRESCENS

The speed of action of baculovirus insecticides may be enhanced by insertion of genes encoding enzymes, hormones or toxins into the viral genome. The coding sequence for juvenile hormone esterase (JHE) of Heliothis virescens was inserted into a baculovirus to produce the recombinant virus AcUW2-(B).JHE which produces polyhedra. These polyhedra are essential for viability of viral insecticides in the field and increase oral infectivity. This virus was purified by a new, rapid method. JHE expression by AcUW2 (B).JHE in larvae of Trichoplusia ni was twice the maximum naturally occurring JHE activity in the haemolymph of H. virescens seen during the final larval stadium. Significantly more JHE activity (130 nm substrate hydrolysed/min/ml) was expressed in vitro in spinner culture than by the polyhedrin negative virus expressing JHE. In vitro studies revealed that the viral promoter for the p10 protein gene used for expression of JHE in AcUW2 (B).JHE is active 4 h before the polyhedrin gene promoter used in the polyhedrin negative virus. These observations illustrate the use of JHE as a soluble, exported reporter enzyme for use in baculovirus studies. The recombinant virus AcUW2 (B).JHE was slightly faster acting than the recombinant control virus AcUW2 (B).lacZ, but did not improve LT50, LD50 values or reduce weight gain of infected larvae, compared to the wild type control virus. Implications for the involvement of JHE in physiological regulation of metamorphosis, and for use in recombinant baculoviruses as insecticides are considered.