An in vitro assay to measure antibody-mediated inhibition of P. berghei sporozoite invasion against P. falciparum antigens
Rodríguez-Galán A., Salman AM., Bowyer G., Collins KA., Longley RJ., Brod F., Ulaszewska M., Ewer KJ., Janse CJ., Khan SM., Hafalla JC., Hill AVS., Spencer AJ.
AbstractA large research effort is currently underway to find an effective and affordable malaria vaccine. Tools that enable the rapid evaluation of protective immune responses are essential to vaccine development as they can provide selection criteria to rank order vaccine candidates. In this study we have revisited the Inhibition of Sporozoite Invasion (ISI) assay to assess the ability of antibodies to inhibit sporozoite infection of hepatocytes. By using GFP expressing sporozoites of the rodent parasiteP.bergheiwe are able to robustly quantify parasite infection of hepatocyte cell lines by flow cytometry. In conjunction with recently produced transgenicP.bergheiparasites that expressP.falciparumsporozoite antigens, we have been able to use this assay to measure antibody mediated inhibition of sporozoite invasion against one of the lead malaria antigensP.falciparumCSP. By combining chimeric rodent parasites expressingP.falciparumantigens and a flow cytometric readout of infection, we are able to robustly assess vaccine-induced antibodies, from mice, rhesus macaques and human clinical trials, for their functional ability to block sporozoite invasion of hepatocytes.