Figure 7

Determination of the ADE potential of antibodies elicited by DENV E-based tetravalent VLP vaccines in BALB/c mice. (a) Groups (n = 12) of AG129 mice were challenged with a sub-lethal dose of DENV-2 S221 (V) or fully-neutralised ICs generated in vitro by incubating the same sub-lethal dose with mAb 4G2 (V + 4G2 ICs), ‘anti-T-mVLP’ antiserum (V + α-T-mVLP ICs),’ anti-B-mVLP mix’ antiserum (V + α-B-mVLP ICs), ‘anti-M-VLP mix’ antiserum (V + α-M-VLP ICs) or anti-DENV-2 S221 antiserum (V + α-DENV-2 S221 ICs) and monitored for survival for a period of 3 weeks. Survival of the ‘V’ (p = 0.0009), V + α-T-mVLP ICs (p = 0.0009), V + α-B-mVLP ICs (p = 0.0009) and V + α-M-VLP ICs (p = 0.0009) groups were significantly higher compared to the survival in the ‘V + 4G2’ group, based on the Mantel-Cox test of significance. Mortality in the ‘V + α-DENV-2 S221 ICs’ group was not significantly different from that in the ‘V + 4G2’ group (p = 0.0555, Mantel-Cox test). Survival curves of multiple groups at 100% have been slightly displaced to avoid superimposition and make them visible. (b) A subset of AG129 mice (n = 3) from the ‘V’, ‘V + 4G2 ICs’, ‘V + α-T-mVLP ICs’ and the ‘V + α-DENV-2 S221 ICs’ were assessed for vascular leakage, in small (S. Int) and large intestines (L. Int), at 4 days post-IC inoculation by Evans blue staining assay. Data are depicted as fold-change in dye-staining with reference to a negative control (NC) group of AG129 mice which did not receive any treatment. A fold-change of 1 corresponds to basal vascular leakage equivalent to the NC group. (c) A second subset of AG129 mice (n = 3) from the same four groups listed in panel ‘b’ were euthanised 4 days after IC inoculation for the preparation of S. Int and L. Int tissue extracts followed by determination of TNF-α. (d) Determination of IL-6 in the same extracts prepared in panel ‘c’. In panels ‘c’ and ‘d’ NC refers to a negative control group of AG129 mice which did not receive any treatment. Statistically very significant and significant differences (un-paired t test) in panels ‘b-d’ are indicated by red and black asterisks, respectively; ns: not significant.