Keele Research Repository

Malaria, the leading cause of death due to vector-borne disease. is responsible for around 250 million cases and 1 million deaths annually, mostly in sub-Saharan Africa where Anopheles gambiae is the major vector.
Novel approaches to malaria control include theoretical use of transgenic mosquitoes to suppress or replace wild type populations. Generation of mosquitoes carrying either a conditional lethal gene (RIDL), or one encoding a molecule able to kill malaria parasites, is a key component of this strategy. Detailed genetic and physiological knowledge of transgenic mosquitoes is important for epidemiological models to accurately determine the outcome of putative field releases. This includes testing the potential for post-integration remobilisation of transgenes in the host genome and testing the reproductive fitness of transgenic mosquitoes in comparison to wild type.
Complex plasmids, designed to create both RIDL strains and strains within which piggyBac remobilisation could be tested, were injected into the Keele strain of An. gambiae. Ultimately, although microinjection techniques were optimised and efficiencies improved over time, generation of such transgenic strains was unsuccessful.
A previously established transgenic strain (EVida3), expressing the Vida3 peptide which is active against ookinete stages of Plasmodium, was subsequently investigated with respect to multiple feeding and relative fitness.
Multiple feeding experiments indicate that complex interactions take place between Vida3 and the natural immune system when mosquitoes are infected with the murine malaria P. yoelii nigeriensis. Vida3 production appears to impact on parasite intensity and mosquito fecundity in both positive and negative ways dependent on factors such as gonotrophic cycle and parasite-stage. Analysis of three life-table fitness parameters, comparing EVida3 hemizygotes to the KIL wild type laboratory strain, indicate no fitness cost associated with transgene presence or expression. Analysis of a further two parameters indicates a possible fitness cost associated with inbreeding rather than transgenesis alone.