Fig. 5: ROS generated in blood phagocytes by IP-opsonized merozoites is associated with protection from febrile malaria.

PBLs incubated with merozoites opsonized with plasma samples (108 Ghanaian and 121 Indian cohorts) were analysed for DCF signal and isoluminol signal quantification. Study participants were classified into susceptible and protected individuals (Ghanaian: n = 63 and 45, respectively and Indian: n = 48 and 73, respectively) based on their febrile malaria status. The DCF signal of susceptible and protected Ghanaian and Indian cohorts (a, c, respectively) were compared in neutrophils (blue) and monocytes (red). Moreover, isoluminol signal (AUC) in PBLs was compared between susceptible and protected cohorts (a, c, black). Left y-axis (a, c) shows the median fluorescence intensity (MFI) of neutrophils and monocytes DCF signal. Right y-axis (a, c) shows the area under the curve (AUC) of the PBLs isoluminol signal. Ghanaian and Indian cohorts (b, d, respectively) were categorized into two equal groups based on the median DCF signal, and to calculate the risk of suffering from febrile malaria during the follow-up period, the Cox-regression model was used to compare the high group with the low group (reference group). Values represent age-adjusted (circles), age-plus monocytes DCF (mono)-adjusted (square), and age-plus neutrophils DCF (neu)-adjusted (triangles) hazard ratios at 95% confidence intervals. P values were determined by Mann–Whitney tests.