Targeting of an Expressed Insect Selective Neurotoxin by its Recombinant Baculovirus: Pharmacokinetic and Pharmacodynamic Aspects

Objectives: 1) Clarification of the mode of potentiation of an expressed insect selective neurotoxin (AaIT) by its recombinant baculovirus. 2) In vitro formation and/or modification of neuroactive polypeptides for the design of new improved recombinant baculoviruses. Results: 1) A combined utilization of bioassays, LM-cytochemistry, the highly resolutive EM immunogold and electrical recording from the CNS of baculovirus and AaIT - expressing – recombinant baculovirus infected larvae it has been shown that the recombinant virus potentiates the effect of the toxin. Potentiation is achieved through its continuous expression in the infected tracheal epithelia thus providing a: a) Local supply of freshly produced toxin in the vicinity of its traget sites; b) Translocation of the expressed toxin to the insect CNS. The latter exposes the recombinant toxin to new, critical, target sites which are inaccessible through the natural route of scorpion envenomation. 2) Subjecting a recombinant AaIT toxin to a newly designed system of random mutagenesis results in large numbers of new AaIT genes with amino acid substitutions. The new or modified toxin genes were inserted into a linear BmNPV expressed in silkworm cell culture and assayed on blowfly and silkworm larvae. Thus a system for mass formation and screening of neuroactive agents was developed. Contribution to agriculture: 1) Demonstration of the insecticidal mechanism, capacity and utility of the combination of neuroactive polypeptides and recombinant pathogens. 2) Development of a simple in vitro system for the formation and selection of new neuroactive polypeptides.