Dissection-independent production ofPlasmodiumsporozoites from whole mosquitoes
Blight J., Sala KA., Atcheson E., Kramer H., El-Turabi A., Real E., Dahalan FA., Bettencourt P., Dickinson-Craig E., Alves E., Salman AM., Janse CJ., Ashcroft FM., Hill AVS., Reyes-Sandoval A., Blagborough AM., Baum J.
Progress towards a protective vaccine against malaria remains slow. To date, only limited protection has been routinely achieved following immunisation with either whole-parasite (sporozoite) or subunit-based vaccines. One major roadblock to vaccine progress, and to pre-erythrocytic parasite biology in general, is the continued reliance on manual salivary gland dissection for sporozoite isolation from infected mosquitoes. Here, we report development of a multi-step method, based on batch processing of homogenised whole mosquitoes, slurry, and density-gradient filtration, which combined with free-flow electrophoresis rapidly produces a pure, infective sporozoite inoculum. Human-infectivePlasmodium falciparumand rodent-infectivePlasmodium bergheisporozoites produced in this way are two- to threefold more infective than salivary gland dissection sporozoites in in vitro hepatocyte infection assays. In an in vivo rodent malaria model, the sameP. bergheisporozoites confer sterile protection from mosquito-bite challenge when immunisation is delivered intravenously or 60–70% protection when delivered intramuscularly. By improving purity, infectivity, and immunogenicity, this method represents a key advancement in capacity to produce research-grade sporozoites, which should impact delivery of a whole-parasite based malaria vaccine at scale in the future.