2. 6 Immunization with Scd KO sporozoites protects against malaria
Immunizations with sporozoites that arrest in the liver elicit a long-term protective host response and protect against infectious sporozoite challenge (Duffy, 2022). To study preerythrocytic protection induced by Scd KO parasites, groups of C57BL/6 mice were intravenously injected with three doses of sporozoites at intervals of two weeks and challenged with infectious sporozoites 10 days post-last immunization. All immunized mice remained blood stage negative after immunization, again demonstrating the lack of breakthrough blood stage infection. We found that all the mice injected with uninfected salivary gland debris developed blood-stage parasitemia, whereas mice immunized with Scd KO sporozoites were completely protected (Table 3). We further challenged the protected mice 120 days after the last immunization, and they remained protected (Table 3). These results demonstrate that immunization with Scd KO sporozoites induces preerythrocytic immunity and protects against malaria.