Figure 5. Transfer of DENV-primed CD8⁺ T cells prevents ADE and reduces viral load after al-UV-DENV2-priming.

A) AG129 mice were infected with 5×10⁸ GE DENV2 and 8 days later the percentage of CD8⁺ T cells staining positive for CD107a (marker of degranulation) was determined by FACS after in vitro restimulation with the DENV peptide NS4B_99–107.

B) The functionality of DENV2-primed CD8⁺ T cells was assessed by in vivo cytotoxicity assay: equal numbers of naïve splenocytes labeled with the DENV peptide NS4B_99–107 (CFSE^hi target cells) and unlabeled splenocytes (CFSE^lo marker cells) were transferred in naïve or infected recipient mice (infection as in A). The target:marker ratio was determined by FACS in the spleen of recipient mice 15 hours after transfer.

C) AG129 mice were primed with al-UV-DENV2 on days −14 and −5 (or not primed) and challenged on day 0 with 5×10⁸ GE DENV2 i.v. On day −1, some mice received 5×10⁷ CD8⁺ T cells from mice infected with 5×10⁸ GE DENV2 seven days earlier. Viral RNA titers were measured on day 3 post-challenge in the liver.

For A, B and C, each symbol represents one mouse n=4–6; experiment A has been repeated twice with similar results. Samples with DENV RNA content under the detection limit are depicted in grey and have no numerical value. For statistical analysis, the value of the detection limit was attributed to samples under the detection limit in order to calculate the p-value.