Whole genome transcriptome profiling of P. falciparum sexually comitted ring stage parasite from malaria patient's peripheral blood

Malaria is spread by the transmission of sexual stage parasites, called gametocytes. However, with Plasmodium falciparum, gametocytes can only be detected in peripheral blood when they are mature and transmissible to a mosquito, which complicates control efforts. Here, we identify the set of genes overexpressed in patient blood samples with high levels of gametocyte-committed ring stage parasites. Expression of all 18 genes was regulated by transcription factor AP2-G, which is required for gametocytogenesis. We selected three genes, not expressed in mature gametocytes, to develop as biomarkers. All three biomarkers were validated in vitro using 6 different parasite lines and an algorithm developed that predicted gametocyte production in ex vivo samples and volunteer infection studies. The biomarkers were also sensitive enough to monitor gametocyte production in asymptomatic P. falciparum carriers allowing early detection and treatment of infectious reservoirs, as well as the in vivo analysis of factors that modulate sexual conversion. We selected a subset of High and Low gametocyte conversion rate (GCR) blood samples (GCR>5.5% and 0%, respectively) collected on day zero (D0) prior to treatment (n=8 each group) in the 2016 study cohort for transcriptome analysis. Samples with High and Low GCR also had high and low transcript levels of mature gametocyte specific genes pfs25 and pfs230 in D8 ex vivo parasite RNA, respectively. For control, we have included parasite lines that produces high (NF54 with shield, NF54 without shield and C9 with shield) or low to no gametocytes (C9 without shield and RCM47).