Combining transgenesis with paratransgenesis to fight malaria

Abstract

Malaria is among the deadliest infectious diseases and Plasmodium, the causative agent, needs to complete a complex development cycle in its vector mosquito for transmission to occur. Two promising strategies to curb 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. Using the Q-system to drive gene expression, we engineered mosquitoes to produce and secrete two effectors - scorpine and the MP2 peptide - into the mosquito gut and salivary glands. We also engineered Serratia, a commensal bacterium capable to spread through mosquito populations, to secrete the same two effectors into the mosquito gut. Whereas both mosquito-based and bacteria-based approaches strongly reduced the oocyst and sporozoite intensity, a substantially stronger reduction of P. falciparum development was achieved when transgenesis and paratransgenesis were combined. Most importantly, transmission of P. berghei from infected to naive mice was maximally inhibited by the combination of the two approaches. Combining these two strategies promise to become a powerful approach to combat malaria. SignificanceMalaria kills hundreds of thousand persons yearly. Clearly, new approaches are needed to fight this disease. Two promising approaches are based on the concept of genetically modifying the mosquito to make it a poor vector for the parasite: 1) transgenesis (engineering the mosquito to deliver anti-malarial compounds) and 2) paratransgenesis (engineering mosquito symbiotic bacteria to deliver anti-malarial compounds). The key questions addressed by this manuscript are: which of the two is the most promising approach? And because transgenesis and paratransgenesis are not mutually exclusive, would the combination of both be the most effective strategy? Our results argue for the combination of the two, showing the additive impact that these two strategies may have in controlling malaria transmission in the field.