Figure 2.

Memory B-cell (mBC) responses in control unvaccinated volunteers receiving controlled human malaria infection (CHMI). Antigen-specific mBC-derived antigen-secreting cells (ASC) per million cultured peripheral blood mononuclear cells (PBMC) were quantified for the (a) 19 kDa C-terminus of merozoite surface protein 1 (MSP1₁₉) and (b) apical membrane antigen 1 (AMA1 antigens in malaria-naive unvaccinated control volunteers before (dC−1) and following a single CHMI (dC+35 and dC+90). The mBC-derived ASC as a % of total IgG⁺ ASC for MSP1₁₉ are also shown (c). Data are presented as dot plots showing individual and median responses. Time-points were compared using Friedman Test, with Dunn's post-test, *P < 0·05, **P < 0·01, and ***P < 0·001. (d) Correlation at dC+35 between MSP1₁₉-specific mBC-derived ASC per million cultured PBMC and anti-MSP1₁₉ ELISA units; (e) MSP1₁₉-specific mBC-derived ASC per million cultured PBMC and duration of blood-stage parasite exposure; and (f) anti-MSP1₁₉ ELISA units and duration of blood-stage parasite exposure. Spearman rank correlation coefficient and P-values are shown (n = 17). Blood-stage exposure was calculated as the number of days from dC+6·5, the predicted time-point of first blood-stage parasitaemia, to time-point of diagnosis. Data are presented and pooled from three separate CHMI trials: MAL034A (closed diamonds, n = 6), MAL034B (closed circles, n = 6) and VAC039 (open circles, n = 5).