Clinical Trial to Evaluate the Safety and Immunogenicity in Age De-Escalation of Direct Venous Inoculation of a Plasmodium Falciparum Sporozoite Vaccine in Tanzanian Adults, Children, and Infants

Brief Summary

Detailed Description

This is a single center trial to assess the safety, tolerability and immunogenicity of PfSPZ Vaccine administered by direct venous inoculation (DVI) to healthy Tanzanian adults, adolescents, and children and infants. 105 healthy male and female; adults, adolescents, children and infant volunteers, aged from 6 months to 45 years, who live in the Bagamoyo Township will be enrolled based on pre-defined inclusion and exclusion criteria implemented according to international ethical standards. The safety and tolerability of PfSPZ Vaccine administered as three doses of either 9.0x10\^5 PfSPZ or 1.8x10\^6 PfSPZ to healthy Tanzanian adults, adolescents, and children 6 years of age or older; and three doses of 4.5x10\^5 PfSPZ or 9.0x10\^5 PfSPZ to healthy Tanzanian children 1 to 5 years of age and infants 6 to 11 months of age, in each case compared to NS controls, will be evaluated. In addition, as an exploratory objective, controlled human malaria infection (CHMI) will be used to assess efficacy in adults three weeks following immunization. Study Design: This is a single center trial with ten groups (Groups 1a/b: ages 18-45; Group 2a/b: ages 11-17; Group 3a/b: ages 6-10; Group 4a/b: ages 1-5; and Group 5b/c: ages 6months-11 months) each with 6 subjects receiving PfSPZ Vaccine and 3 subjects receiving NS and an eleventh smaller group (Group 5a: ages 6months-11months) with 3 subjects receiving PfSPZ Vaccine; two of these groups (Group 1a/b) contain adult volunteers and will have infectivity controls (CHMI 1 and 2) each having 3 subjects, after the vaccination phase of the study. The adult volunteers will undergo CHMI 3 weeks after the last immunization. For the first immunization, two volunteers (out of six) in Group 1a will receive 9x10\^5 of PfSPZ Vaccine by DVI as sentinels, to demonstrate safety and tolerability. At the same time, one (out of three) corresponding control volunteers will receive NS, in order to maintain blinding. Approximately 24 hours later, provided criteria for calling an ad hoc SMC meeting are not met, the remaining four volunteers in Group 1a will also receive a 9x10\^5 PfSPZ dose of the vaccine and the remaining two placebo recipients will receive NS. After review of at least +14 days post vaccination safety data for Group 1a by the SMC, if there are no significant safety concerns, two volunteers (out of six) in Group 1b will receive 1.8x10\^6 PfSPZ, and two volunteers (out of six) in each of the Groups 2a and 3a will receive 9x10\^5 PfSPZ, of the PfSPZ Vaccine, to demonstrate safety and tolerability, and each of these sentinel groups will be joined by one corresponding NS control in order to maintain blinding. Approximately 24 hours later, provided criteria for calling an ad hoc SMC meeting are not met, the remaining four volunteers in Group 1b will receive 1.8x10\^6 PfSPZ and the remaining four volunteers in each of Groups 2a and 3a will receive 9x10\^5 PfSPZ of the PfSPZ Vaccine, and the remaining placebo recipients will receive NS. After review of at least +14 days post vaccination safety data for Groups 1b, 2a and 3a by the SMC, if there are no significant safety concerns, two volunteers (out of six) in each of the Groups 2b and 3b will receive 1.8x10\^6 PfSPZ, those in Group 4a will receive 4.5x10\^5 PfSPZ and all 3 volunteers in Group 5a will receive 2.7x10\^5 PfSPZ of PfSPZ Vaccine, to demonstrate safety and tolerability, and each of the sentinel groups (two volunteers from Groups 2b, 3b and 4a) will be joined by one NS control in order to maintain blinding. Approximately 24 hours later, provided criteria for calling an ad hoc SMC meeting are not met, the remaining four volunteers in Groups 2b, 3b and 4a will receive their appropriate dose of PfSPZ Vaccine (1.8x10\^6 PfSPZ, 1.8x10\^6 PfSPZ, and 4.5x10\^5 PfSPZ, respectively), and the placebo recipients will receive NS. Escalation from the small group of infants, (Group 5a, n=3) receiving a single dose of 2.7x10\^5 PfSPZ, to the full group (Group 5b, n=6) receiving three doses of 4.5x10\^5 PfSPZ, will proceed without SMC review if criteria for calling an ad hoc SMC meeting are not met. However, if the criteria are met, an ad hoc SMC meeting will be called to review the data, and dose escalation to 4.5x10\^5 PfSPZ will be postponed until the recommendations of the SMC are available. The interval between the 2.7x10\^5 PfSPZ small group and the 4.5x10\^5 PfSPZ larger group will be a minimum of three days. After review of at least +14 days post vaccination, safety data for Groups 2b, 3b, 4a, 5a and 5b by the SMC, if there are no significant safety concerns, two volunteers (out of six) in each of the Groups 4b and 5c will receive 9x10\^5 PfSPZ, to demonstrate safety and tolerability. At the same time, one (out of three) corresponding control volunteers will receive NS, in order to maintain blinding. Approximately 24 hours later, provided criteria for calling an ad hoc SMC meeting are not met, the remaining four volunteers in Group 4b and 5c will receive 9x10\^5 PfSPZ dose of the vaccine, and the placebo recipients will receive NS.

Primary Outcomes

Secondary Outcomes

• Inhibitory Capacity of Volunteer Sera against in vitro Sporozoite Invasion of Hepatocytes(Post first immunization uptil 56 days post-CHMI or 56 days post-3rd immunization)
• Quantitation of cellular immune responses against Pf proteins in volunteers(Post first immunization uptil 56 days post-CHMI or 56 days post-3rd immunization)
• Level of Antibodies against Pf proteins in volunteer sera(Post first immunization uptil 56 days post-CHMI or 56 days post-3rd immunization)
• Whole genome expression profiles of volunteer(Post first immunization uptil 56 days post-CHMI or 56 days post-3rd immunization)