Enhancement of Baculoviruses' Insecticidal Potency by Expression of Synergistic Anti-Insect Scorpion Toxins

The extensive use or non-specific, hazardous, chemical insecticides demands the development of "healthier" alternative means for pest control. Insect-specific, baculoviruses expressing anti-insect toxin genes (from mites or scorpions) demonstrated in laboratory assays and field trials enhanced insecticidal activity and provided some protection from lepidopterous larvae to agricultural plantations. To utilize recombinant baculoviruses as commercial biopesticides in row crop agriculture, further increase in their speed of kill should be achieved and the reduction in crop damage should be comparable to the levels obtained with organic insecticides (the problem). In this project we developed strategies to improve further the efficacy of recombinant baculoviruses which included: I) Synergism among baculoviruses expressing different anti-insect toxins: a) Synergism among two complementary anti-insect scorpion neurotoxins each expressed by a separate recombinant baculovirus, both regulated by the same or a different viral promoter. b) Synergism among two complementary anti-insect scorpion neurotoxins expressed by the same recombinant virus, both regulated by the same or a different viral promoter respectively. The above included two classes of pharmacologically complementary toxins: i) toxins with strictly anti-insect selectivity (excitatory and depressant); ii) toxins with preferential anti-insect activity (anti-insect alpha toxins). c) Synergism among wild type viruses, recombinant baculoviruses and chemicals (insecticides and phytochemicals) II) Identification of more potent toxins against lepidopterous pests for their expression by baculoviruses. Our approach was based on the synergistic effect displayed by the combined application of pairs of anti-insect toxins to blowfly and lepidopterous larvae that resulted in 5 fold increase in their insecticidal activity without apparent increase in their anti-mammal toxicity (toxins LqhIT2 and LqhaIT, LqhIT2 and AaIT, and LqhaIT and AaIT (1). Thus, we developed new concepts and produced a "second generation" of recombinant baculoviruses with enhanced potencies and speeds of kill comparable to classical insecticides. These achievements contribute to make these biopesticides a viable alternative to minimize the use of hazardous chemicals in pest control. Also, our project contributed new tools and model systems to advance the study of insect sodium channels.