Consistent Safety and Infectivity in Sporozoite Challenge Model of Plasmodium vivax in Malaria-Naive Human Volunteers
NAVAL MEDICAL RESEARCH CENTER SILVER SPRING MD MALARIA PROGRAM
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A safe and reproducible Plasmodium vivax infectious challenge method is required to evaluate the efficacy of malaria vaccine candidates. Seventeen healthy Duffy and five Duffy - subjects were randomly allocated into three A-C groups and were exposed to the bites of 2-4 Anopheles albimanus mosquitoes infected with Plasmodium vivax derived from three donors. Duffy - subjects were included as controls for each group. Clinical manifestations of malaria and parasitemia were monitored beginning 7 days post-challenge. All Duffy volunteers developed patent malaria infection within 16 days after challenge. Prepatent period determined by thick smear, was longer for Group A median 14.5 d than for Groups B and C median 10 deach. Infected volunteers recovered rapidly after treatment with no serious adverse events. The bite of as low as two P. vivax-infected mosquitoes provides safe and reliable infections in malaria-naive volunteers, suitable for assessing antimalarial and vaccine efficacy trials.