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ABSTRACT: Bacillus thuringiensis Cry toxins are useful bioinsecticides that have been successfully used for the control of several vectors of parasitic diseases. Cry toxins are well known for their specificity, safety to vertebrates (including humans) and for their low environmental impact due to their biodegradability. The main drawback of the Cry toxins is that, in many cases there is no known toxin active against the insects that represent a threat or a health problem. In this work we tested the hypothesis that in vitro evolution of Cry toxins and their selection using phage display technology could represent a useful strategy for developing novel insecticides active against non-target insects.
Using a Cry toxin mutant library derived from the lepidopteran-active Cry1Aa13 toxin we selected several clones with high affinity to the intestinal proteins of Aedes aegypti, insect vector for viral diseases such as Dengue fever, Yellow fever and other parasites such as filaria. The selected mutants showed a completely different amino acid sequence in the loop2 of the domain II compared with the lepidopteran-active wild type protein. These toxins could potentially be active against this target insect, which is not a natural target of Cry1Aa13 since binding to epithelial cell proteins is the first step required for Cry toxin activity.
The in vitro selected phage showing high affinity for proteins in the guts of A. aegypti were analyzed, and their sequences compared with wild type Cry toxin and natural occurring toxins active against this mosquito.
XII Congreso Ibérico de parasitología., Zaragoza, Spain; 01/2011
