An in vitro parasite Growth Inhibition Assay (GIA; also referred to as the Invasion Inhibition Assay, IIA) is one of the few widelyused biological assays that can measure the functional activity of antibodies against blood-stage malaria. While it is still controversial whether the activity measured by the GIA (IIA) reflects protective immunity induced by a vaccine, the assay has been used in preclinical and clinical studies as one of the immunological readouts. Not only anti-AMA1 antibodies induced by malaria infection [26, 27] , but also antibodies induced by AMA1 immunization in malaria naïve individuals show growth-inhibitory activity in the in vitro GIA [14, 16, 19, [21] [22] [23] .