Transgenesis and conditional lethality in Aedes albopictus

Abstract

The Asian tiger mosquito Aedes albopictus (Skuse) is a vector of several arboviruses including dengue and chikungunya. This highly invasive species originates from Southeast Asia and has spread across the world in the last 30 years. It is now established in Europe, North and South America, Africa, the Middle East and the Caribbean. In the absence of vaccine or antiviral drugs, efficient mosquito control strategies are crucial. Conventional control methods have so far failed to adequately control Ae. albopictus. Using germline transformation technology, a technique known as Release of Insects carrying a Dominant Lethal (RIDL) proposes to enhance the sterile insect technique by replacing irradiation with inherited dominant lethal genes. While this technology has recently shown some success in the field against the yellow fever mosquito, Aedes aegypti (L.), it remains to be implemented against Ae. albopictus. This thesis presents the development and application of gene transfer and site-specific integration technologies in Ae. albopictus, as well as the creation of tetracycline-repressible, female-specific flightless lines for vector control based on the RIDL method. Germline transformation and site-specific integration were performed using the piggyBac transposon and the ФC31 system, respectively. Ae. albopictus RIDL strains showing a conditional female-specific flightless phenotype were created using both the Ae. aegypti and the Ae. albopictus Actin-4 regulatory regions. Conditionality was provided by the ‘Tet-Off’ system, which is suppressed in the presence of tetracycline (and suitable analogues). One of these strains was assessed for attributes relevant to a RIDL control programme. Specific tailoring of the RIDL transgene with alternative transactivator elements was investigated using the ФC31 system. The work presented in this thesis lays the foundations for the application of the RIDL strategy to Ae. albopictus, an innovative vector-control method offering a promising alternative for efficient control of this highly invasive insect.