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The mosquito Culex quinquefasciatus poses a significant threat to human and veterinary health as a primary vector of West Nile virus (WNV), the filarial worm Wuchereria bancrofti, and an avian malaria parasite. Comparative phylogenomics revealed an expanded canonical C. quinquefasciatus immune gene repertoire compared with those of Aedes aegypti and Anopheles gambiae. Transcriptomic analysis of C. quinquefasciatus genes responsive to WNV, W. bancrofti and non-native bacteria facilitated an unprecedented meta-analysis of 25 vector-pathogen interactions involving arboviruses, filarial worms, bacteria and malaria parasites, revealing common and distinct responses to these pathogen types in three mosquito genera. Our findings provide support for the hypothesis that mosquito-borne pathogens have evolved to evade innate immune responses in three vector mosquito species of major medical importance.

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The mosquito (Aedes aegypti) vitellogenin receptor (AaVgR) is a large membrane-bound protein (214 kDa when linearized) that mediates internalization of vitellogenin, the major yolk-protein precursor, by oocytes during egg development. We have cloned and sequenced two cDNA fragments encompassing the entire coding region of AaVgR mRNA, to our knowledge the first insect VgR sequence to be reported. The 7.3-kb AaVgR mRNA is present only in female germ-line cells and is abundant in previtellogenic oocytes, suggesting that the AaVgR gene is expressed early in oocyte differentiation. The deduced amino acid sequence predicts a 202.7-kDa protein before posttranslational processing. The AaVgR is a member of the low density lipoprotein receptor superfamily, sharing significant homology with the chicken (Gallus gallus) VgR and particularly the Drosophila melanogaster yolk protein receptor, in spite of a very different ligand for the latter. Distance-based phylogenetic analyses suggest that the insect VgRIyolk protein receptor lineage and the vertebrate VgR/low density lipoprotein receptor lineage diverged before the bifurcation of nematode and deuterostome lines.The developing embryo of an oviparous animal draws practically all of its requisite nutrients from a cache of proteins, lipids, and carbohydrates stored within the egg as yolk. Yolkprotein precursors are synthesized extraovarially and transported to the developing egg where they are specifically recognized and bound by membrane-spanning cell-surface receptors. Receptor-ligand complexes accumulate in clathrincoated pits, which pinch-off into the cytoplasm, a fundamental process ubiquitous among cells for internalizing macromolecules referred to as receptor-mediated endocytosis (1, 2). The insect oocyte provides an excellent system for studying receptor-mediated endocytosis because of the high intensity of protein uptake. Mosquitoes are especially useful models in this regard, because a tightly regulated series of physiological events associated with egg maturation is synchronized across all primary oocytes by a blood meal.In the yellow fever mosquito Aedes aegypti (Aa), oocyte size increases more than 300-fold within 36 h of a blood meal (3), largely through the specific accumulation of the major yolkprotein precursor vitellogenin (AaVg). This impressive biological feat depends on the proper interaction ofAaVg with its receptor (AaVgR) on the oocyte surface. In addition to its exceptional value as a model for studying receptor-mediated endocytosis, this system is also a promising target for future novel control strategies. For example, interruption of the receptor-ligand interaction would block egg development, and theAaVgR could serve as a target for an antimosquito vaccine (4). A prerequisite to successful manipulation of this system is a thorough understanding of the proteins involved: their structures, interactions, regulation, and expression. Meaningful progress on all of these fronts hinges on knowledge of the primary structures of both AaVg, which we r...

Progress in molecular genetics makes possible the development of alternative disease control strategies that target the competence of mosquitoes to transmit pathogens. We tested the regulatory region of the vitellogenin (Vg) gene of Aedes aegypti for its ability to express potential antipathogen factors in transgenic mosquitoes. Hermes-mediated transformation was used to integrate a 2.1-kb Vg-promoter fragment driving the expression of the Defensin A (DefA) coding region, one of the major insect immune factors. PCR amplification of genomic DNA and Southern blot analyses, carried out through the 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 meal. 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 transgenic defensin were accumulated in the hemolymph of bloodfed female mosquitoes, persisting for 20 -22 days after a single blood feeding. Purified transgenic defensin showed antibacterial activity comparable to that of defensin isolated from bacterially challenged control mosquitoes. Thus, we have been able to engineer the genetically stable transgenic mosquito with an element of systemic immunity, which is activated through the blood meal-triggered cascade rather than by infection. This work represents a significant step toward the development of molecular genetic approaches to the control of vector competence in pathogen transmission.