Oral Ingestion of Transgenic RIDL Ae. aegypti Larvae Has No Negative Effect on Two Predator Toxorhynchites Species

Abstract

Dengue is the most important mosquito-borne viral disease. No specific treatment or vaccine is currently available; traditional vector control methods can rarely achieve adequate control. Recently, the RIDL (Release of Insect carrying Dominant Lethality) approach has been developed, based on the sterile insect technique, in which genetically engineered ‘sterile’ homozygous RIDL male insects are released to mate wild females; the offspring inherit a copy of the RIDL construct and die. A RIDL strain of the dengue mosquito, Aedes aegypti, OX513A, expresses a fluorescent marker gene for identification (DsRed2) and a protein (tTAV) that causes the offspring to die. We examined whether these proteins could adversely affect predators that may feed on the insect. Aedes aegypti is a peri-domestic mosquito that typically breeds in small, rain-water-filled containers and has no specific predators. Toxorhynchites larvae feed on small aquatic organisms and are easily reared in the laboratory where they can be fed exclusively on mosquito larvae. To evaluate the effect of a predator feeding on a diet of RIDL insects, OX513A Ae. aegypti larvae were fed to two different species of Toxorhynchites (Tx. splendens and Tx. amboinensis) and effects on life table parameters of all life stages were compared to being fed on wild type larvae. No significant negative effect was observed on any life table parameter studied; this outcome and the benign nature of the expressed proteins (tTAV and DsRed2) indicate that Ae. aegypti OX513A RIDL strain is unlikely to have any adverse effects on predators in the environment.

Exposure to genetically engineered olive fly (Bactrocera oleae) has no negative impact on three non-target organisms

“…Our results are in agreement with previously published data on safety of genetically engineered mosquitoes carrying similar transgenes and their exposure to non-target organisms 9 . Importantly, the DsRed2 marker gene and its protein have been widely used in a variety of species, including insects, without any adverse effect 30 .…”

“…In mosquitoes, the tTAV expression system is repressed by tetracycline, but the corresponding mRNA has been shown to be expressed in the absence of the antibiotic 31 . In that previous study, no adverse effects were detected in Toxorhynchites’ development fed with mosquito larvae reared either in the presence or absence of tetracycline 9 .…”

“…The assessment of the environmental impact of genetically engineered insects is an important safety aspect and a prerequisite for their commercialization as vector/pest control agents 9 . Risk of exposure to non-target organisms could occur through parasitizing the B .…”

Biological Control Strategies for Mosquito Vectors of Arboviruses

“…amboinensis on transgenic lines of Ae. aegypti did not show any significant difference in longevity, which supports the continuous use of the Toxorhynchites species for biological control in combination with the use of transgenic mosquitoes [32]. Similar conclusions were drawn from the evaluation of the predatory behavior of Tx.…”

Bicistronic expression and differential localization of proteins in insect cells andDrosophila suzukiiusing picornaviral 2A peptides

“…This universal effector would also reduce the effort required to test transgenes for potential detrimental effects on human health or the environment. Furthermore, DsRed is an excellent candidate because it is widely used as a marker in plants, vertebrates, and invertebrates [52][53][54][55][56][57] but is not known to be toxic following oral administration, as shown by the analysis of predators feeding on mosquito larvae expressing a DsRed transgene [58]. It is also stable under laboratory and field conditions, making it a reliable candidate marker for SIT programs [59,60].…”