Trial to Evaluate the Safety, Immunogenicity, and Efficacy of Malaria Infection in Malaria Naïve Adults

This is a study designed to assess the safety, tolerability, immunogenicity, and protective efficacy of 2 heterologous prime-boost vaccine regimens in healthy, malaria naïve adults. The study will include 2 vaccine groups and an infectivity control (IC) group consisting of non-immunized subjects. Subjects to be immunized will be randomly assigned to one of two vaccine groups. Approximately 4 weeks after administration of the boosting immunization the vaccinated groups and the IC group will participate in CHMI wherein subjects will be exposed to the bites of 5 Anopheles stephensi mosquitoes carrying infectious Pf sporozoites within a controlled clinical environment. Protection will be determined by the examination of thick blood smears through 28 days post-CHMI and by retrospective PCR analysis for the presence of blood stage parasites. All groups will be enrolled and evaluated in one cohort. Due to a limit in the number of subjects who can undergo malaria challenge at the facility in one day, CHMI will be conducted over two days. Group 1 (2-antigen): 3 doses at 4 week intervals (Week 0, 4, and 8) of DNA prime with D-C + D-A at 2 mg total (1 mg per construct) per dose as two 1 mL IM injections of the blended D-CA, one in each arm, via Biojector 2000 needle-free injection device or an equivalent disposable syringe needle-free injection device. This will be followed after 16 weeks (Week 24) by 1 dose of ChAd63-C + ChAd63-A boost, at a total dose of 1 x 1011 virus particles (vp) (5 x 1010 vp/construct) as a single IM injection of 0.65mL, using a needle and syringe. Group 2 (3-antigen): 3 doses at 4 week intervals (Week 0, 4, and 8) of DNA prime with D-C + D-A + D-T at 3 mg total (1 mg per construct) per dose as two 1 mL intramuscular (IM) injections of the blended D-CAT, one in each arm, via Biojector 2000 needle-free injection device or an equivalent disposable syringe needle-freeinjection device. This will be followed after 16 weeks (Week 24) by 1 dose of ChAd63-C + ChAd63-A + ChAd63-T boost, at a total dose of 1.5 x 1011 vp (5 x 1010 vp/construct) as a single IM injection of 1.0mL, using a needle and syringe.