An all-in-one pipeline for thein vitrodiscovery andin vivotesting ofPlasmodium falciparummalaria transmission blocking drugs

Abstract

Elimination and eradication of malaria will depend on new drugs with potent activity againstPlasmodium falciparummature stage V gametocytes, the only stages able to infect the mosquito vector for onward parasite transmission. The identification of molecules active against these quiescent stages is difficult due to the specific biology of gametocyte maturation and challenges linked to their cultivationin vitro. Furthermore, the antimalarial drug development pipeline lacks a suitable animal model for evaluating the transmission-blocking potential of promising lead compounds and preclinical and clinical drug candidatesin vivo. Here, we established a transmission-blocking drug discovery and development platform based on transgenicP. falciparumparasites engineered to produce large numbers of pure stage V gametocytes expressing a red-shifted firefly luciferase as reporter for cellular viability. This NF54/iGP1_RE9Hulg8line facilitated the development of a highly efficient and robustin vitroscreening assay for the identification of stage V gametocytocidal compounds. Importantly, by infecting humanized NODscidIL2Rγnullmice with pure NF54/iGP1_RE9Hulg8stage V gametocytes, we also established a preclinicalP. falciparum in vivotransmission model. Using whole animal bioluminescence imaging and quantification of gametocyte densities over a period of 14 days, we assessed the gametocyte killing and clearance kineticsin vivoof antimalarial reference drugs as well as five clinical drug candidates and identified markedly different pharmacodynamic response profiles. Furthermore, we successfully integrated this mouse model with mosquito feeding assays and thus firmly established a valuable tool for the systematicin vivoevaluation of gametocytocidal and transmission-blocking drug efficacy.One sentence summaryWe applied robust new assays for gametocytocidal drug discovery andin vivoefficacy testing using a humanized mouse model for malaria transmission