Molecular analysis of Plasmodium falciparum and human genetic variants

Plasmodium falciparum, the only Plasmodium species responsible for life-threatening malaria in humans, has been one of the strongest selective forces acting on Homo sapiens over the last 10,000 years. Extensive evidence demonstrates the role of malaria in shaping human genetic adaptations; however, the impact of the human genetic background on parasite transmissibility from humans to mosquitoes remains poorly understood. Several studies have shown that carriers of hemoglobin variants, such as hemoglobin C (HbC) and hemoglobin S (HbS), are less susceptible to severe malaria compared to individuals with the wild-type genotype. Paradoxically, these variants have also been associated with increased gametocyte carriage—the sexual stages of the parasite responsible for transmission—which potentially enhances malaria transmission. Similarly, glucose-6-phosphate dehydrogenase (G6PD) deficiency has been linked to altered susceptibility to severe malaria and to higher levels of parasite sexual stages. In this study, we focus on malaria transmission by conducting molecular analyses of mosquitoes, which represent a unique biological interface containing genetic information from the parasite, the human host, and the mosquito vector. This integrated approach enables the simultaneous investigation of parasite infection, human blood meal composition, and mosquito-related factors that influence transmission dynamics. Specifically, our objectives are: (i) the identification and quantification of P. falciparum ookinete stages in field- collected Anopheles mosquitoes fed on human hosts; (ii) the detection of human features within the mosquito blood meal, including host sex and the presence of genetic variants prevalent in sub-Saharan Africa, such as HbC, HbS, and G6PD deficiency (e.g., G6PDA−); and (iii) the correlation of these human features with parasite ookinete load in infected mosquitoes, to assess their contribution to malaria transmission. Overall, this work aims to develop and apply sensitive molecular tools based on the analysis of single infected mosquitoes to elucidate the relationships between human host conditions and P. falciparum transmission. By improving our understanding of how human genetic factors influence parasite development within the mosquito, this study may contribute to a more comprehensive view of malaria transmission biology and support the development of targeted control strategies.