Developing Plasmodium vivax Resources for Liver Stage Study in the Peruvian Amazon Region

Area of Science:

• Malariology and Parasitology
• Drug Discovery and Development
• Tropical Medicine

Background:

• Developing new drugs and vaccines for malaria elimination requires targeting Plasmodium vivax exoerythrocytic forms.
• A robust in vitro culture system for P. vivax liver stages is currently lacking, hindering research.
• Studying exoerythrocytic forms necessitates access to fresh patient blood and specific mosquito vectors in endemic regions.

Purpose of the Study:

• To establish a field-accessible in vitro culture system for Plasmodium vivax exoerythrocytic forms (EEF) in a malaria-endemic region.
• To enable drug screening against P. vivax liver stages using locally sourced infected mosquitoes and patient samples.
• To overcome challenges associated with low parasitemia, mosquito vectorial capacity, and environmental conditions in field settings.

Main Methods:

• Utilized P. vivax sporozoites from naturally infected Anopheles darlingi mosquitoes, the primary vector in the Americas.
• Dissected salivary glands, purified sporozoites using Accudenz density gradient centrifugation, and infected HC04 liver cells.
• Implemented a novel antibiotic cocktail in tissue culture to prevent contamination in humid, non-sterile field conditions.

Main Results:

• Successfully cultured P. vivax exoerythrocytic forms (EEF) in vitro for up to 9 days, observing maturation into intrahepatocyte merosomes.
• Identified P. vivax EEF exhibiting resistance to atovaquone but sensitivity to the phosphatidylinositol 4-kinase inhibitor KDU691.
• Demonstrated the feasibility of a field-based P. vivax liver stage production process for drug discovery.

Conclusions:

• Developed a practical, field-based in vitro system for culturing P. vivax liver stages in the Amazon region.
• This system facilitates drug discovery and experimentation on P. vivax liver stages using viable sporozoites from local vectors.
• The findings support the development of essential resources for P. vivax malaria elimination efforts in endemic areas.