Strain-specific immunity induced by immunization with pre-erythrocytic stages of Plasmodium chabaudi

Abstract

One of the most promising approaches in the efforts to produce a malaria vaccine involves the use of attenuated whole sporozoite immunizations. Attenuation may be achieved by the use of genetic modification, irradiation, chemical attenuation, or by the contemporaneous administration of antimalarial drugs that target only the erythrocytic stages of the parasite. Most research to date has focused on the efficacy of these approaches upon challenge with parasites homologous to those used for the initial immunizations. We, as have others, have previously shown that a component of the immunity achieved against the erythrocytic stages of the rodent malaria parasite Plasmodium chabaudi chabaudi is strain-specific, with a stronger immune response targeting the immunizing strain than genetically distinct strains. Here, we show that the immunity induced by infection with the pre-erythrocytic stages of these parasites, achieved via inoculation of sporozoites contemporaneously with mefloquine, also has a strain-specific component.

Figure 1

Course of parasitaemia in challenge infections with Plasmodium chabaudi chabaudi in groups of mice twice immunized by sporozoite infection under a mefloquine cover with CB (solid lines) or AJ (light dotted lines) sporozoites of P. c. chabaudi and in mock-immunized control mice (heavy dashed lines). Cumulative proportion of parasitized red blood cells throughout the infections is shown in the bar chart insets. The challenge infections were with sporozoites of CB (Panel a) and AJ (b), and with blood-stage parasites of CB (c) and AJ (d). Error bars indicate one standard error above and below the mean.