Fig. 2.

Enhancement of humoral and cellular response to S1 protein immunization by adjuvants is specific. B6 (WT) mice were immunized with priming on day 0 and two booster doses, each at two-week intervals. Mice were immunized with S1 protein alone, or co-delivered with Alum, IL-12 and GM-CSF, or IL-15 and TLR-Ls in DOTAP. Serum samples were collected at day 45 post-immunization and subjected to ELISAs for individual peptides from S1 and RBD proteins, with responses shown as a heat map (A). Spleen cells collected at day 200 post-immunization were stimulated ex vivo with pooled groups of peptides from S1 and RBD proteins for 6 h before staining for intracellular production of IFNγ by total CD8⁺ T cells (B) was assessed. (C) Representative flow cytometry dot plot of RBD-tetramer⁺ and IFNγ⁺ CD8⁺ T cells deriving from spleens of naïve mice or mice immunized with S1 protein co-delivered with IL-15 and TLR-Ls and ex vivo exposed to pool 3 for 6 h. (D) Graphed individual values. The data are represented as the mean ± SEM and represent 2 independent experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001 determined using an unpaired two-tailed Student’s t-test.