Engineering blood meal-activated systemic immunity in the yellow fever mosquito, Aedes aegypti

Progress in molecular genetics makes possible the development of alternativ e disease control strategies that target the competence of mosquitoes to tr ansmit pathogens. We tested the regulatory region of the vitellogenin (Vg) gene of Aedes aegypti for its ability to express potential antipathogen fac tors in transgenic mosquitoes. Hermes-mediated transformation was used to i ntegrate a 2.1-kb Vg-promoter fragment driving the expression of the Defens in A (DefA) coding region, one of the major insect immune factors. PCR ampl ification of genomic DNA and Southern blot analyses, carried out through th e ninth generation, showed that the Vg-DefA transgene insertion was stable. The Vg-DefA transgene was strongly activated in the fat body by a blood me al. The mRNA levels reached a maximum at 24-h postblood meal, corresponding to the peak expression time of the endogenous Vg gene. High levels of tran sgenic defensin were accumulated in the hemolymph of bloodfed female mosqui toes, persisting for 20-22 days after a single blood feeding. Purified tran sgenic defensin showed antibacterial activity comparable to that of defensi n isolated from bacterially challenged control mosquitoes. Thus, we have be en able to engineer the genetically stable transgenic mosquito with an elem ent of systemic immunity, which is activated through the blood meal-trigger ed cascade rather than by infection. This work rep resents a significant st ep toward the development of molecular genetic approaches to the control of vector competence in pathogen transmission.