Correlates of protective immunity following whole sporozoite vaccination against malaria.

Human infection with Plasmodium parasites remains a serious global health crisis, leading to more than 600,000 deaths annually. Currently, no licensed vaccine is available to alleviate this malaria disease burden and vaccination with the most advanced antimalarial vaccine candidate, RTS,S, provides limited protection that wanes over time. To date, the only vaccination strategy capable of inducing complete, long-lasting protection in human subjects is administration of attenuated whole sporozoites. Several approaches for vaccination with attenuated whole sporozoites have been clinically tested in humans and include vaccination with radiation or genetically attenuated sporozoites or with virulent sporozoites concurrent with administration of antimalarial drug cover. Rodent studies with these three attenuated whole sporozoite vaccination (WSV) approaches provide insights into the immune correlates of vaccine-induced protection. The majority of these studies have identified a critical role for liver-stage parasite-directed CD8 T cells in providing protection with possible contributions from Plasmodium-specific CD4 T cells or antibodies. Together, rodent and human vaccination studies with attenuated WSV may lead to an understanding of the correlates of protective immunity against malarial disease, and the development of new, highly efficacious vaccines.