Wolbachia strain wMelPop reduces longevity of its Drosophila melanogaster host and halves lifespan when introduced into the mosquito Aedes aegypti. We show that wMelPop induces upregulation of the mosquito innate immune system and that its presence inhibits the development of filarial nematodes in the mosquito. These data suggest that wMelPop could be used in the global effort to eliminate lymphatic filariasis, and possibly the control of other mosquito-borne parasites where immune preactivation inhibits their development. The cost of constitutive immune upregulation may contribute to the life-shortening phenotype.Wolbachia pipientis is a maternally inherited intracellular bacterium of invertebrates, capable of spreading itself through populations by reproductive manipulation such as cytoplasmic incompatibility (CI). The strain wMelPop or 'popcorn', unusually, reduces longevity of its Drosophila melanogaster host (1) and has been shown to also halve lifespan when the mosquito Aedes aegypti was stably transinfected (2). The wMelPop life-shortening phenotype offers the prospect of a novel disease control system by potentially skewing the population structure toward younger individuals. Vectorial capacity is particularly sensitive to mosquito age because mosquito-borne pathogens require an extrinsic incubation period between ingestion and transmission that is long compared to mean lifespan in the field, such that only older mosquitoes within a population are potentially infective. wMelPop was also found to be inherited at high rates and to induce strong cytoplasmic incompatibility (CI) in Ae. aegypti, providing a reproductive advantage to infected females. The wMelPop strain should be capable of spread through populations despite the reduction in mean lifespan, because the reproduction of older individuals makes a relatively small contribution to the next generation (2-6).We compared host gene expression using whole genome microarrays in genetically identical Ae. aegypti lines infected and uninfected with wMelPop (7) to examine the mechanism underlying the life-shortening phenotype. Of 199 gene transcripts upregulated by more than a twofold threshold, 78 had putative immune-related functions (Fig. 1, table S2). These included genes that encode seventeen CLIP domain serine proteases, nine FREPs (fibrinogen-related proteins), six cecropins, four TEPs (Thio-ester containing proteins), three defensins, three PPOs (prophenoloxidases), two lysozymes, two PGRPs (peptidoglycan recognition proteins), two GNBPs (Gram negative binding proteins), and the NF-κB transcription factor Rel2. At higher levels of fold upregulation, effector genes, particularly cecropins and other antimicrobial peptides, dominate the list (Fig. 1, table S2). Five immune-related genes (primarily of regulatory predicted function) were downregulated below the twofold threshold (table S2).* To whom correspondence should be addressed. steven.sinkins@zoo.ox.ac.uk. Quantitative RT-PCR (qRT-PCR) experiments, with mosquitoes at two and fifteen days pos...

The over-replicating wMelPop strain of the endosymbiont Wolbachia pipientis has recently been shown to be capable of inducing immune upregulation and inhibition of pathogen transmission in Aedes aegypti mosquitoes. In order to examine whether comparable effects would be seen in the malaria vector Anopheles gambiae, transient somatic infections of wMelPop were created by intrathoracic inoculation. Upregulation of six selected immune genes was observed compared to controls, at least two of which (LRIM1 and TEP1) influence the development of malaria parasites. A stably infected An. gambiae cell line also showed increased expression of malaria-related immune genes. Highly significant reductions in Plasmodium infection intensity were observed in the wMelPop-infected cohort, and using gene knockdown, evidence for the role of TEP1 in this phenotype was obtained. Comparing the levels of upregulation in somatic and stably inherited wMelPop infections in Ae. aegypti revealed that levels of upregulation were lower in the somatic infections than in the stably transinfected line; inhibition of development of Brugia filarial nematodes was nevertheless observed in the somatic wMelPop infected females. Thus we consider that the effects observed in An. gambiae are also likely to be more pronounced if stably inherited wMelPop transinfections can be created, and that somatic infections of Wolbachia provide a useful model for examining effects on pathogen development or dissemination. The data are discussed with respect to the comparative effects on malaria vectorial capacity of life shortening and direct inhibition of Plasmodium development that can be produced by Wolbachia.

The Toll receptor was originally identified as an indispensable molecule for Drosophila embryonic development and subsequently as an essential component of innate immunity from insects to humans. Although in Drosophila the Easter protease processes the pro-Spätzle protein to generate the Toll ligand during development, the identification of the protease responsible for pro-Spätzle processing during the immune response has remained elusive for a decade. Here, we report a protease, called Spätzle-processing enzyme (SPE), required for Toll-dependent antimicrobial response. Flies with reduced SPE expression show no noticeable pro-Spätzle processing and become highly susceptible to microbial infection. Furthermore, activated SPE can rescue ventral and lateral development in embryos lacking Easter, showing the functional homology between SPE and Easter. These results imply that a single ligand/receptor-mediated signaling event can be utilized for different biological processes, such as immunity and development, by recruiting similar ligand-processing proteases with distinct activation modes.