Insights into Anopheles coluzzii immune responses to different infection loads of Plasmodium falciparum ookinetes

The activation of the Anopheles coluzzii innate immune system is crucial for Plasmodium falciparum development and survival within the vector, as well as for facilitating its subsequent transmission to humans. Any modulation or impairment of this immune response can impact the parasite ability to complete its lifecycle within the mosquito and thus affect transmission to the human host. In this study, we investigated variations in the expression of mosquito immune-related genes in response to different intensities of P. falciparum infection, as assessed at the ookinete stage. Specifically, we employed RNA-seq analysis to compare the immune responses of An. coluzzii mosquitoes at 12, 24, and 36 hours post-infection (hpi) in condition of low and high parasite loads during the ookinete invasion of the mosquito midgut. This iterative timeframe allowed us to capture the dynamic changes that occur in the mosquito immune system as the infection progresses. Our findings revealed striking differences between the two conditions. Mosquitoes harboring low parasite loads displayed a strong upregulation of immune-related genes, suggesting that they mount a more robust immune response compared to those with higher parasitic loads.