Context. Immature gametocytes are sequestered in the deep vasculature while mature gametocytes circulate in the peripheral blood. Mature gametocytes are thus exposed to the fine mechanical sensing displayed by the human spleen, which constantly filters circulating RBC and retains those that are altered. We have developed two experimental models to analyze this process: the ex-vivo perfusion of human spleens and the filtration of RBC through layers of microspheres (“microsphiltration”). Microsphiltration mimics the mechanical sensing of RBC by the human spleen. Immature gametocytes are retained in microsphilters while mature gametocytes can flow through. We propose that membrane remodeling occurs that transforms stiff stage IV immature gametocytes into deformable stage V gametocytes, and we have identified a parasite protein family (Pf mg/fam ) that could be involved in this process.
Project goal, objectives and critical milestones. Our first working hypothesis is that a compound decreasing the deformability of mature gametocytes will induce their clearance by the spleen, thereby sequestering them away from Anopheles and blocking parasite transmission. To confirm the relevance of this hypothesis, we will show the retention of mature gametocytes with altered deformability in microsphilters and in human spleens. Our second hypothesis is that microsphiltration can be adapted to Medium Throughput Screening (MTS). To prove this method feasible we will pour the microspheres into microplates, use vacuum to filter gametocytes through the microsphere layers, and determine the technical parameters associated with the appropriate retention rates of RBC infected with asexual and sexual stages.
Our ultimate goal is to identify compounds inducing mechanical alterations of mature gametocytes thereby triggering their clearance by the spleen, a novel transmission-blocking strategy that will help the Foundation progress toward the eradication of malaria.