Figure 6

Evaluation of the induction of DENV-nAbs by E-based tetravalent VLPs in BALB/c mice. Virus-neutralising activity of pooled (n = 6) antisera from mice immunised with (a) ‘M-VLP mix’, (b) ‘B-mVLP mix’ and (c) ‘T-mVLPs’ against WHO reference strains of DENV-1 (magenta), DENV-2 (green), DENV-3 (blue) and DENV-4 (black) as a function of serum dilution, determined using the FACS-based assay. The dashed horizontal line denotes 50% neutralisation of DENV infectivity. Data points represent mean (n = 6) values; the error bars represent SD. Tables above the graphs indicate nAb titres (FNT₅₀) calculated from the graphic data. Mann-Whitney test-derived p values for DENV-1 (p = 0.7962), DENV-2 (p = 0.6665), DENV-3 (p = 0.2973) and DENV-4 (p = 0.8633) did not reveal any statistically significant differences in nAb titres between ‘T-mVLP and ‘B-mVLP mix’ groups. Similarly FNT₅₀ titres between ‘T-mVLP’ and ‘M-VLP mix’ groups for DENV-1 (p = 0.5457), DENV-2 (p = 0.8633), DENV-3 (p = 0.6048) and DENV-4 (p = 0.7962) did not vary significantly based on Mann-Whitney test for significance. (d) Pooled immune sera from the T-mVLP group was pre-depleted of EDIII-specific Abs on immobilised MBP-EDIII proteins corresponding to the four DENV serotypes (1, 2, 3 & 4) before determination of residual virus neutralising activity. Data are expressed as percent residual geometric mean nAb titres with respect to those of corresponding controls, mock-depleted on immobilised MBP, taken as 100%. Error bars denote SD. Mock-depletion did not significantly affect the nAb titres specific to the four DENV serotypes compared to un-depleted immune sera (Supplementary Fig. S4).