Malaria sporozoite in-vitro production

Decreases the cost, time, and improves the feasibility of producing parasite stages used for vaccine development, drug screening, and basic biological research pertaining to a complex agent of human disease

Medical & Biotechnology

Malaria infects hundreds of millions of people every year, which results in significant sickness and death. The only approved vaccine for malaria is RTS,S (Mosquirix), which requires four injections and has relatively low effectiveness.

Several approaches to developing a more effective vaccine are centered on the sporozoite – the parasite life stage ejected by mosquitos during a bite. The sporozoites used in vaccine development are isolated from dissected salivary glands of aseptically grown mosquitoes. This current method of sporozoite production is technically difficult, expensive, time-consuming, and labor intensive. The ability to produce the sporozoites in vitro would quicken the pace in producing live attenuated malaria vaccine candidates by completely by-passing the mosquito stage of parasite development.

To meet this need, Army researchers have developed a simple, scalable method for in vitro development of a infective-stage malaria parasite without using a live insect or insect cells. The technique isolates gametocytes from a maintained P. falciparum human erythrocytes culture, enriching the gametocyte culture, maturing the gametocytes, and progressing them to sporozoites by exflagellation initiated by addition of xanthurenic acid (XA). XA is a gametocyte activating factor produced in the mosquito midgut and known to induce fertilization.

This method generates insect-free, in vitro-grown, Plasmodium sporozoites that have never been exposed to an insect or an insect cell. The isolated, infectious, metabolically active sporozoites can identify the parasite stage-specific surface markers, gene expression, protein-protein interactions and other elements of parasite biology that have remained difficult to determine because these lifecycle stages have previously only been reliably produced inside the natural mosquito vector.

Beyond vaccine development, sporozoites produced from this method could be used in diagnostic assays, as well as to provide kits for malaria screening and confirmatory antibody tests.

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