Pre-erythrocytic Stage Antigen Discovery for Malaria Vaccine Development

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DESCRIPTION (provided by applicant): The development of an effective malaria vaccine is a high global health priority. Malaria is the most burdensome parasitic disease of man, exacting an estimated toll of 863,000 deaths and 243 million clinical cases per year. There is an urgent need for a safe and effective malaria vaccine. An abundance of data in rodents, non-human primates and humans indicate the existence of protective antigens in whole organism malaria vaccines that induce T cells which target the pre-erythrocytic stages of the malaria parasite. However, the specific antigen targets of this protective immunity are not known. Our overall goal is to identify novel, highly protective, pre-erythrocytic antigens for malaria vaccine development. Our hypothesis is that the pre- erythrocytic P. yoelii antigens that are the targets of protective cell responses induced by immunization with highly protective regimens of live sporozoites under chloroquine prophylaxis will induce robust and protective immune responses in mice when delivered by adenovectors; and that the corresponding P. falciparum orthologues will be good candidate antigens for malaria vaccine development. We propose a rational and systematic approach to identify these novel highly protective, pre-erythrocytic antigens. We have already developed an array of adenovectors that express 300 of the most highly expressed pre-erythrocytic P. yoelii antigens, and will screen this array to identify antigens that recall robust T cell responses from mice immunized with live sporozoites under chloroquine prophylaxis (Specific Aim 1). Adenovectors from the array that recall the strongest T cell responses will be purified and evaluated for their ability to induce protective immune responses in mice (Specific Aim 2). Transitioning to preclinical development, we will build hexon-modified Ad5 vectors expressing the P. falciparum orthologues of the three most protective antigens and evaluate their capacity to induce T cell and antibody responses in mice (Specific Aim 3). Success in achievement of these aims will advance three new pre-erythrocytic antigens to malaria vaccine development.