Insect-borne diseases kill more humans than all other diseases combined. Existing strategies for limiting the spread of such diseases are helping, but it is clear that complete eradication of some of the most deadly diseases ? especially malaria ? is going to require additional approaches. The goal of this project is to test strategies to block insect-borne disease transmission by intervening at the level of the insect vector, preventing transmission of disease-causing parasites and viruses by causing the timely death of the adult female mosquito salivary gland (SG). A current limitation for studies attempting to manipulate the SG ? a gateway organ for transmitting malaria and other insect borne diseases - is that almost nothing is known about SG development, function or homeostasis in any insect outside Drosophila. The molecules involved in specifying, building or specializing mosquito SGs are largely unknown. The proposed study begins with learning the consequences of RNAi knock-down of three Anopheles gambiae transcription factor (TF) genes whose Drosophila orthologues have key roles in Drosophila SG development, function and survival. We ask if TF gene knockdown affects SG survival or morphology, or the ability of infective malaria sporozoites to invade the SGs and to be transmitted in the saliva. In the second aim, we create null and tissue-specific mutations in the Anopheles gambiae sage gene, which encodes a SG-specific TF whose Drosophila orthologue is required for SG survival and expression of SG-specific cargo genes. We ask how complete loss of sage affects viability, fecundity and SG morphology. We ask if loss of sage affects sporozoite SG invasion and sporozoite counts in saliva. We also determine if SG-specific loss of sage following a blood meal leads to similar outcomes. Finally, to learn how well our SG-centric approach to limiting disease transmission works in general, we ask if RNAi knockdown of the sage orthologue in Aedes aegypti affects the SG and its ability to transmit Dengue virus.
Malaria is an infectious disease that affects hundreds of millions of people each year, killing hundreds of thousands, mostly children under the age of five. The disease is caused by a parasite that spends part of its lifespan in humans and the other part in mosquitoes. In this proposal we test genetic-based approaches for destroying the mosquito salivary gland ? an organ essential for parasite transmission ? as part of a longer-term strategy for preventing mosquitoes from spreading the disease from one person to another.
