Extended Data Fig. 2: Invasion process across Dantu genotype groups studied by time-lapse video microscopy.
From: Red blood cell tension protects against severe malaria in the Dantu blood group
a, The force of RBC detachment from a merozoite was measured using optical tweezers across genotype groups. RBCs attached to merozoites were pulled using optical traps, and the adhesive forces at the merozoite–RBC interface were quantified by evaluating the elastic morphological response of the RBCs as they resisted merozoite detachment. Means and standard deviations (s.d.) are shown in Supplementary Table 3. Six biologically independent samples per genotype group were tested, obtaining 21 events for non-Dantu individuals, 19 for Dantu heterozygotes, and 24 for Dantu homozygotes. The experimentalist was blinded to the RBC genotype group. The median is indicated by the middle red line in the boxplots, with the 25th and 75th percentiles indicated by the tops and bottoms of each plot, and the total data range shown by whiskers. If the median is not centred in the box, it shows sample skewness. Pairwise comparisons between genotype groups were performed using the two-sided Mann–Whitney U-test. b, The degree to which merozoites deformed RBCs during invasion is given by a simplified four-point deformation scale (0, 1, 2 and 3), with 3 indicating the most extreme degree of deformation achieved10. The degree of deformation was compared across genotype groups with no significant difference noticed, and between successful and failed invasions. The percentage of RBCs undergoing strong deformations (score 2/3) is substantially higher in the case of successful invasions, while RBCs that were contacted but not invaded experience weak deformations (score 0/1). Data are from 155 cells for non-Dantu individuals, 191 for Dantu heterozygotes, and 233 for Dantu homozygotes. Numbers of successfully invaded cells are 53 for non-Dantu, 43 for Dantu heterozygote, and 41 for Dantu homozygote. The visual assessment was made with blinded data by two different experimentalists. c, Successful invasions are usually followed by a reversible echinocyte phase that lasts between 5 min and 11 min31, until the recovery of newly infected RBC biconcave shape. The duration of echinocytosis here is in agreement with the literature and not significantly different across genotype groups; data from 53 cells non-Dantu, 43 Dantu heterozygotes and 41 Dantu homozygotes.
