Chemoprophylaxis and Plasmodium Falciparum NF54 Sporozoite Immunization Challenged by Heterologous Infection

Malaria, a disease caused by the parasite Plasmodium, is one of the world's major infectious diseases. With approximately 627.000 deaths a year, it is both a chief cause of morbidity and mortality as well as a significant contribution to ongoing poverty in endemic countries. Ultimately, the key to malaria control, and hopefully eradication, would be an effective vaccine. Though a number of vaccine-candidates have entered the pipeline of pre-clinical and clinical development, they have yet to achieve the level of efficacy necessary for effective malaria prevention. It has been shown previously that if healthy human volunteers taking chloroquine chemoprophylaxis are repeatedly exposed to Plasmodium parasites through the bites of infected mosquitoes, they are fully protected against a later challenge infection with a 'homologous' (genetically similar) Plasmodium parasite. This process is known as ChemoProphylaxis and Sporozoites, or CPS-immunization. One of the obstacles to developing an effective vaccine is the genetic heterogeneity of malaria parasites. To further consider the development of whole-parasite based vaccines against malaria and in order to better understand the protective immunity induced by CPS-immunization, it is essential to investigate whether heterologous protection against genetically diverse (heterologous) P. falciparum clones can be induced. This is a single center, randomized, double-blind study to determine whether healthy volunteers immunized with P. falciparum NF54 parasites under chloroquine prophylaxis are protected against a challenge infection with the genetically distinct NF135.C10 or NF166.C8 P. falciparum clones.