Abstract
BackgroundSignificant progress has been recently achieved in the development of Plasmodium vivax challenge infections in humans, which are essential for vaccine and drug testing. With the goal of accelerating clinical development of malaria vaccines, the outcome of infections experimentally induced in naïve and semi-immune volunteers by infected mosquito bites was compared.MethodsSeven malaria-naïve and nine semi-immune Colombian adults (n = 16) were subjected to the bites of 2–4 P. vivax sporozoite-infected Anopheles mosquitoes. Parasitemia levels, malaria clinical manifestations, and immune responses were assessed and compared.ResultsAll volunteers developed infections as confirmed by microscopy and RT-qPCR. No significant difference in the pre-patent period (mean 12.5 and 12.8 days for malaria-naïve and malaria-exposed, respectively) was observed but naïve volunteers developed classical malaria signs and symptoms, while semi-immune volunteers displayed minor or no symptoms at the day of diagnosis. A malaria-naïve volunteer developed a transient low submicroscopic parasitemia that cured spontaneously. Infection induced an increase in specific antibody levels in both groups.ConclusionSporozoite infectious challenge was safe and reproducible in semi-immune and naïve volunteers. This model will provide information for simultaneous comparison of the protective efficacy of P. vivax vaccines in naïve and semi-immune volunteers under controlled conditions and would accelerate P. vivax vaccine development.Trial Registrationclinicaltrials.gov NCT01585077
Highlights
Despite multiple technical and financial constraints for Plasmodium vivax malaria research, significant efforts have been invested and progress has been achieved towards development of an effective P. vivax vaccine
P. vivax CS-derived subunit vaccine formulations based on Long Synthetic Peptides (LSP) formulated in Montanide adjuvant have been shown to be safe, well-tolerated
Good Clinical Practices [23] and the protocol was approved by Institutional Review Boards (IRB) of the Malaria Vaccine and
Summary
Despite multiple technical and financial constraints for Plasmodium vivax malaria research, significant efforts have been invested and progress has been achieved towards development of an effective P. vivax vaccine. Pvs protein [3,4], have reached clinical development and have been tested in Phase I vaccine trials. Successful efforts are being made on the discovery of novel P. vivax antigens that could be proposed for vaccine development [9]. As with P. falciparum, the P. vivax CS protein is among the most promising vaccine candidates. Significant progress has been recently achieved in the development of Plasmodium vivax challenge infections in humans, which are essential for vaccine and drug testing. With the goal of accelerating clinical development of malaria vaccines, the outcome of infections experimentally induced in naıve and semi-immune volunteers by infected mosquito bites was compared
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