Malaria causes an estimated 500 million clinical cases and up to 2.7 million deaths annually, is responsible for a loss of greater than 1% of GDP in Africa annually, and is a serious concern for travelers and military personnel. Sanaria's goal is to develop and commercialize an attenuated Plasmodium falciparum sporozoite vaccine for two primary markets with a potential for > $1 billion annual revenues; 1) Travelers from the developed world and 2) Infants and young children in the developing world. In limited trials, this type of immunization has been shown to protect greater than 90% of human volunteers against experimental P. falciparum challenge, protect for greater than 10 months after last immunization, and protect against heterologous challenge. No other experimental malaria vaccine under development has been shown to approach these performance characteristics. Heretofore it has been considered impractical to develop such a vaccine, in large part because volunteers have been immunized by the bite of infected mosquitoes, and mice by intravenous (IV) administration of sporozoites. All findings in humans with irradiated sporozoites have been anticipated by studies in mice with rodent malaria, and Sanaria has recently demonstrated an effective and practical method to deliver irradiated sporozoites that does not require IV administration in a mouse model. Extensive discussions with the Food and Drug Administration staff indicate that, (1) Sanaria's approach is consistent with regulatory standards, but that (2) an acceptable vaccine will have to be aseptic, and relatively free of contamination by salivary gland proteins and other material. To develop the process to produce such sporozoites in this project we will develop an optimal method to, 1) Surface sterilize A. stephensi mosquito eggs, 2) Rear A. stephensi mosquitoes from aseptic eggs to aseptic, robust adults under sterile culture conditions, 3) Produce aseptic, infectious P. yoelii and then P. falciparum sporozoites in aseptic A. stephensi mosquitoes, and 4) Produce and characterize homogeneously purified, aseptic, infectious P. yoelii and then P. falciparum sporozoites from dissected salivary glands. Because the infectivity of P. yoelii sporozoites can be assessed in vivo by intravenous injection into mice, and the infectivityof P. falciparum sporozoites can only be assessed in vitro in hepatocyte cultures, initial experiments will be conducted with P. yoelii, and after methods are established in P. yoelii, studies will be done with P. falciparum. At the conclusion of this SBIR we will have established a method and a process for producing P. falciparum sporozoites that can be used in the production of a vaccine that meets standards acceptable to the Food and Drug Administration for human use under an investigational new drug (IND) application in a Phase I/lla clinical trial.
