Late-acting dominant lethal genetic systems and mosquito control

BACKGROUND: Reduction or elimination of vector populations will tend to reduce or eliminate transmission of vector-borne diseases. One potential method for environmentally-friendly, species-specific population control is the Sterile Insect Technique (SIT). SIT has not been widely used against insect disease vectors such as mosquitoes, in part because of various practical difficulties in rearing, sterilization and distribution. Additionally, vector populations with strong density-dependent effects will tend to be resistant to SIT-based control as the population-reducing effect of induced sterility will tend to be offset by reduced density-dependent mortality. RESULTS: We investigated by mathematical modeling the effect of manipulating the stage of development at which death occurs (lethal phase) in an SIT program against a density-dependence-limited insect population. We found late-acting lethality to be considerably more effective than early-acting lethality. No such strains of a vector insect have been described, so as a proof-of-principle we constructed a strain of the principal vector of the dengue and yellow fever viruses, Aedes (Stegomyia) aegypti, with the necessary properties of dominant, repressible, highly penetrant, late-acting lethality. CONCLUSION: Conventional SIT induces early-acting (embryonic) lethality, but genetic methods potentially allow the lethal phase to be tailored to the program. For insects with strong density-dependence, we show that lethality after the density-dependent phase would be a considerable improvement over conventional methods. For density-dependent parameters estimated from field data for Aedes aegypti, the critical release ratio for population elimination is modeled to be 27% to 540% greater for early-acting rather than late-acting lethality. Our success in developing a mosquito strain with the key features that the modeling indicated were desirable demonstrates the feasibility of this approach for improved SIT for disease control

Engineering Sciences Supporting Regenerative BioMedicine: Recent Accom-­ plishments

International audienceWe here report recent developments where engineering sciences and mechanics, the basis for reliable design, construction, and maintenance in civil and mechanical engineer-­ ing, have been successfully adapted and trans-­ ferred to the needs of regenerative biomedicine. Thereby, our key target is fracture safety of bony organs and scaffold-­organ compounds.The basis for our safety assessment is a mathematical model for the multiscale ("nano-to-macro") mechanics of bone tissues across the entire vertebrate anial kingdom. This model traces the fracture of bone tissues, donw to sliding phenomena between nanocrystals, and nreaking molecules [4].Besides from setting new standards also in the field of theoretical mechanics itself [7] these mathematical developments, always accompanied by cutting edge experimental activities [6], have paved the way towards computer-aided design of bonestissue engineering systems, as exemplified through a clinically approved hydroxyapatite granule system for dental tissue engineering [9-10]. Such novel methods can also be straightforwardly coupled to valuable information from Computed Tomography: By means of appropriate merging of continuun micromechanics and X-Ray physics, the compositional and mechanical characteristics of the matter found within each and every voxel can be revealved. In this context, we recently deciphered the role of bone anisotropy in assessing biting deformations [5], the resorption properties of TCP biomaterial scaffolds [3], the load carrying behaviorof glass-ceramic scaffolds [8], the safety factor of human vertebrae, and of the aforementioned hydroxyapatite globules under physiological loading [1-2]