Fig. 6: CD4⁺CXCR5⁺ T cell populations increase after repetitive CHMI and T follicular helper cells (Tfh) correlate with CXCL13 levels.

PBMC from each participant collected 7 days after treatment (DRx+7) on each CHMI were analyzed by flow cytometry without exogenous stimulation. All six participants that completed the mock CHMI were included in the flow cytometry analysis (C1 n = 6, C2 n = 6, C3 n = 5, C4 n = 4), but the participant with a low CD3 + CD4 + T cell count was excluded from the percent calculations (C1 n = 5, C2 n = 5, C3 n = 4, C4 n = 3). A The percent of CXCR5 positive CD3 + CD4 + T cells, CD3 + CD4 + CCR7-CD45RO+ (effector memory) and CD3 + CD4 + CCR7 + CD45RO+ (central memory) T cells detected on DRx+7 of each CHMI is shown. Mean values +/− standard error of the mean (SEM) are indicated for each time point. Statistical differences were determined using Dunnett’s multiple comparisons test between CHMI 1 and CHMI 2-4. Data that did not pass the normality test was first logarithmically transformed to conform to normality and then tested for significance. All P values are two-sided. B The logarithm of plasma CXCL13 levels (pg/ml) on DRx for each participant for each CHMI is plotted against the number (upper graph) or percent (lower graph) of (CD3 + CD4 + CD45RO + CXCR5 + PD-1+ (Tfh)) cells detected in the DRx+7 PBMC sample from the corresponding participant at the corresponding CHMI. Correlation analysis was determined using Spearman’s rank correlation and listed in each panel (rho = correlation coefficient and p = P value). C The mean value +/− SEM of CXCL13 (pg/ml) in plasma with anti-CSP IgG levels above or below 0.5 OD 410 nm on D1, D6, D8, DRx and DRx+7 for all 4 CHMI is shown. Statistical differences were determined using Mann–Whitney test and all P values are two-sided. Source data are provided as a Source Data file.