Case Report: Successful Sporozoite Challenge Model in Human Volunteers with Plasmodium vivax Strain Derived from Human Donors
NAVAL MEDICAL RESEARCH CENTER SILVER SPRING MD
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Successful establishment of a Plasmodium vivax sporozoite challenge model in humans is described. Eighteen healthy adult, malaria-na ve volunteers were randomly allocated to Groups A-C and exposed to 3 1, 6 1, and 9 1 bites of Anopheles albimanus mosquitoes infected with P. vivax , respectively. Seventeen volunteers developed signs and symptoms consistent with malaria, and geometric mean prepatent periods of 11.1 days 9.3-11 for Group A 10.8 days 9.811.9 for Group B and 10.6 days 8.7-12.4 for Group C, with no statistically significant difference among groups Kruskal-Wallis, P 0.70. One volunteer exposed to eight mosquito bites did not develop a parasitemia. No differences in parasite density were observed and all individuals successfully recovered after anti-malarial treatment. None of the volunteers developed parasite relapses within an 18-month follow-up. In conclusion, malaria-naive volunteers can be safely and reproducibly infected with bites of 2-10 An. albimanus mosquitoes carrying P. vivax sporozoites. This challenge method is suitable for vaccine and anti-malarial drug testing.
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