Identification of correlates of protection for infectious diseases including malaria is a major challenge and has become one of the main obstacles in developing effective vaccines.
Plasmodium infections are responsible for millions of cases of malaria and ∼1 million deaths annually.
The infection by the malaria parasite of its mammalian host is initiated by the asexual reproduction of the parasite within the host hepatocyte.
Clinical manifestations of malaria and parasitemia were monitored beginning 7 days post-challenge. All Duffy (+) volunteers developed patent malaria infection within 16 days after challenge.
There are ongoing efforts to develop a vaccine based on this system. Attenuation of sporozoites may be achieved via irradiation, genetic modification, or through the use of drugs targeting the blood stage parasite.
An ideal vaccine for malaria would target all stages of the parasite life cycle, and thereby prevent infection, severe disease and transmission.
Malaria parasites undergo two rounding-up transformations in their life cycle: the ookinete-to-oocyst transformation in the mosquito midgut, and the sporozoite-to-EEF (exo-erythrocytic form) differentiation in the host hepatocyte.
Successful establishment of a Plasmodium vivax sporozoite challenge model in humans is described. In conclusion, malaria-naive volunteers can be safely and reproducibly infected with bites of 2–10 An. albimanus mosquitoes carrying P. vivax sporozoites. This challenge method is suitable for vaccine and anti-malarial drug testing.