The stagnation of our fight against malaria in recent years, mainly due to the development of mosquito insecticide resistance, argues for the urgent development of new weapons. The dramatic evolution of molecular tools in the last few decades led to a better understanding of parasite-mosquito interactions and coalesced in the development of novel tools namely, mosquito transgenesis and paratransgenesis.Here we provide a historical view of the development of these new tools and point to some remaining challenges for their implementation in the field.

Plasmodium parasites are reliant on the Apicomplexan AP2 (ApiAP2) transcription factor family to regulate gene expression programs. The AP2 DNA binding domains have no homology to the human or mosquito hosts, making them potential drug targets. Using an in-silico screen to dock thousands of small molecules into the crystal structure of the AP2-EXP (Pf3D7_1466400) AP2 domain (PDB:3IGM), we identified compounds that interact with this domain. Four compounds were found to compete for DNA binding with AP2-EXP and at least one additional ApiAP2 protein. Our top ApiAP2 competitor compound perturbs the transcriptome of P. falciparum trophozoites and results in a decrease in abundance of log2 fold change > 2 for 50% (46/93) of AP2-EXP target genes identified. Additionally, two ApiAP2 competitor compounds have anti- Plasmodium activity against P. berghei mosquito stage parasites. In summary, we describe a novel set of antimalarial compounds that are targeted against the ApiAP2 family of proteins. These compounds may be used for future chemical genetic interrogation of ApiAP2 proteins or serve as starting points for a new class of antimalarial therapeutics.

Malaria is among the deadliest infectious diseases. Two promising strategies to curb parasite transmission are transgenesis, consisting of genetically engineering mosquitoes to express anti-malarial effector molecules and paratransgenesis, consisting of introducing into the mosquito, commensal bacteria engineered to express anti-malarial effector molecules. Although both approaches restrict parasite development in the mosquito, it is not known how their effectiveness compares. Here we provide an in-depth assessment of transgenesis and paratransgenesis and evaluate the combination of the two approaches. We engineered mosquitoes and Serratia, a commensal bacterium capable to spread through mosquito populations, to produce and secrete two effectors – scorpine and the MP2 peptide. Whereas the mosquito- and bacteria-based approaches reduced parasite load, a substantially stronger reduction was achieved when they were combined. Most importantly, transmission from infected to naïve mice was maximally inhibited by the combination of the two approaches. This combination promises to become a powerful approach to combat malaria.

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