Abstract:
The vision of a malaria-free world is threatened by antimalarial drug resistance. For malaria elimination to be achieved, drug combinations should have dual action: cure infection and block transmission of the Plasmodium parasite between the human host and mosquito vector. Furthermore, such dual action drugs should lower the risk of resistance development and prolong the therapeutic lifespan of antimalarials. New antimalarial drugs need to comply to a set guideline from the Medicines for Malaria Venture with regards to the types of molecules [target candidate profiles (TCP)] and the combination of medicines being developed. Therefore, knowing a compound’s activity towards a specific stage of the parasite, in other words its TCP, is important for drug development. However, due to the parasite’s complex life cycle, each stage of the parasite currently requires a different biochemical platform to assay compounds for activity against that particular life cycle state. This does introduce assay readout variability and complicates standardisation of drug assays. This study, therefore, aimed to generate a constitutive luciferase-expressing P. falciparum line that can be used to develop a single assay platform for all life cycle stages of the parasite. By using gene expression profiling, we identified several constitutively expressed genes throughout the life cycle of P. falciparum. The promoters of these genes were used to generate transgenic lines in which a robust luciferase reporter is strongly expressed under control of these promoters. Two transgenic lines were successfully generated and allowed luciferase expression under control of promoters for histone H3 and nuclear assembly protein (NF54H3 and NF54nap). Whilst NF54H3 could be used to effectively determine antiplasmodial activity for compounds towards the asexual stages, this line was compromised to the extent that it was not able to produce gametocytes. By contrast, NF54nap produced both asexual parasites and gametocytes and was used to evaluate drug activity for both these stages on a single luciferase reporter assay platform. As a result, the line generated here enables a single platform to delineate the TCP of compounds and identify novel compounds that are active against multiple stages or that show selective activity towards a specific stage of the parasite. This data contributes to a novel avenue in antimalarial drug discovery, thereby supporting malaria elimination strategies.
