Evaluation of Reproducibility of a Sporozoite Challenge Model for Plasmodium Vivax in Human Volunteers

Detailed Summary

The study is a randomized open label clinical trial to verify the reproducibility of a sporozoite challenge model for Plasmodium vivax in humans. The verification of the reproducibility of such a model will make it possible to evaluate the efficacy of candidate P. vivax vaccines in Phase 2a trials. The study is divided into two successive steps: Step A Parasite Blood Donation: Volunteers will be recruited passively from a group of patients who present with active P. vivax infection and accept to donate infected blood. Samples of P. vivax infected blood will be collected and will be screened for infectious diseases, according to standard blood bank procedures. Colonized Anopheles albimanus mosquitoes will be fed with this blood using a Membrane Feeding Assay (MFA). Sixteen (16) days after, selected positive mosquito batches will be used for step B. Step B Challenge: After informed consent signature, a total of 18 healthy volunteers will be randomly allocated to Groups 1, 2 and 3, of 6 volunteers each and will be challenged with the bite of 3±1, P. vivax infected mosquitoes. Each group will be exposed to a different isolated parasite. Volunteers will be closely monitored post infection, and will be treated as soon as blood infection becomes patent as ascertained by microscopic examination of thick blood smears (TBS). Comparison of data obtained in the three different groups will be used to determine reproducibility of challenge model. Primary objective: To demonstrate that naïve human volunteers can be safely and reproducibly infected by the bite of An. albimanus mosquitoes carrying P. vivax sporozoites in their salivary glands. Secondary objective: To determine the influence of the type of parasite isolated on reproducibility and safety of the challenge model with P. vivax in human volunteers Hypothesis:It is possible to safely develop a reproducible P. vivax infection in human volunteers using P. vivax experimentally infected An. albimanus mosquitoes.

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