Genetically Modified Aedes aegypti for the Control of Dengue Transmission

Genetics-based vector control strategies based on population replacement are being developed for mosquito-borne diseases including dengue. Population replacement requires controlled sex- and tissue-specific expression of effector genes and development of a drive system to introgress the effector genes in wild mosquito populations. Female mosquito salivary glands are critical sites for expression of effector genes as they play a crucial role in virus transmission. Transcriptome analyses of Aedes aegypti discovered that the 30K genes are expressed exclusively and in great abundance in the salivary glands of adult females. Blast searches of the genome revealed that there are three 30K genes in Ae. aegypti, all present on the same supercontig. Two of these genes, 30K a and 30K b, are separated by a 263 bp intergenic region and are transcribed divergently. Orthology of the 30K genes in the mosquito species was established and the 5' upstream region was scanned for conserved regulatory motifs but no conserved motifs were found. Based on the genomic sequence and Expressed Sequence Tags (EST) data available for the 30K a and b genes, the 5' and 3' untranslated regions (UTRs) of the genes were identified. The functional characterization of the putative bidirectional promoter and control elements was performed in transgenic Ae. Aegypti. The cis-regulatory sequences of the 30K a and 30K b genes were used to express simultaneously an enhanced green fluorescent protein (EGFP) reporter and an anti-dengue effector gene, Mnp, in the salivary glands of female mosquitoes. The expression of the effector gene in female salivary glands resulted in reduced prevalence and mean intensities of virus infection in salivary glands and saliva. Efforts to develop a transposon based gene drive system were made by testing the remobilization potential of three different class II transposable elements Mos1 mariner, Osmar5 and mPing in Ae. aegypti. No remobilization of Mos1 was detected in transgenic females expressing Mos1 transposase in the germ cells. Interplasmid mobility assays for Osmar5 and mPing performed in Ae. aegypti embryos also indicated no movement.