J Clin Invest 2020 Feb 11. Epub 2020 Feb 11.
Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, Heston, Australia.
Background: Interventions that interrupt Plasmodium vivax transmission or eliminate dormant P. vivax liver-stage parasites will be essential for malaria elimination. Development of these interventions has been hindered by the lack of P. vivax in vitro culture and could be accelerated by a safe and reproducible clinical model in malaria-naïve individuals.
Method: Healthy, malaria-naïve adults were enrolled in two studies to assess the safety and infectivity and transmissibility of a new P. vivax isolate. Participants (Study 1; n=2, Study 2; n=24) were inoculated with P. vivax-infected red blood cells to initiate infection, and were treated with artemether-lumefantrine (Study 1) or chloroquine (Study 2). Primary endpoints were safety and infectivity of the new isolate. In Study 2, transmission to mosquitoes was also evaluated using mosquito feeding assays, and sporozoite viability was assessed using in vitro cultured hepatocytes.
Results: Parasitaemia and gametocytemia developed in all participants and was cleared by antimalarial treatment. Adverse events were mostly mild or moderate and none were serious. Participants were infectious to Anopheles mosquitoes at peak gametocytemia 69% (11/16). Mosquito infection rates reached 97% following membrane feeding with gametocyte-enriched blood, and sporozoites developed into liver-stage schizonts in culture.
Conclusion: We have demonstrated the safe, reproducible, and efficient transmission of P. vivax gametocytes from humans to mosquitoes, and have established an experimental model that will accelerate the development of interventions targeting multiple stages of the P. vivax life cycle.
Trial Registration: ACTRN12614000930684 and ACTRN12616000174482.
Funding: (Australian) NHMRC Program Grant: 1132975 (Study 1). Bill & Melinda Gates Foundation (OPP1111147) (Study 2).