Looking under the skin: the first steps in malarial infection and immunity.

Malaria, which is caused by Plasmodium spp., starts with an asymptomatic phase, during which sporozoites, the parasite form that is injected into the skin by a mosquito, develop into merozoites, the form that infects erythrocytes. This pre-erythrocytic phase is still the most enigmatic in the parasite life cycle, but has long been recognized as an attractive vaccination target. In this Review, we present what has been learned in recent years about the natural history of the pre-erythrocytic stages, mainly using intravital imaging in rodents. We also consider how this new knowledge is in turn changing our understanding of the immune response mounted by the host against the pre-erythrocytic forms.