The nanovaccine DEX(OVA+LPS) induces profound activation of antigen-specific CD8⁺ T cells <i>in vivo.</i>

<p>C57BL/6 mice received CFSE-labeled, OVA-specific OT-I T cells (10⁷) <i>i.v.</i> Two days later, groups of mice (each five animals) were either left untreated or were immunized with OVA (4 µg per mouse), LPS (4 µg), and DEX particle formulations (each 200 µl) as indicated. (A) On day 5, the frequencies of proliferating CD8⁺CD45.1⁺Vα2⁺ OT-I cells were determined in spleen cell suspensions by flow cytometry. (B) In the same experiments, the frequencies of IFNγ⁺ OT-I T cells were assessed by flow cytometry. (A,B) Data represent mean±SEM of two independent experiments each. The frequencies of proliferating and IFN-γ producing CD8⁺ OT-I T cells in either group were signifiantly higher than in the non-immunized control group. Other statistical significant differences between groups are indicated (*p<0.05, **p<0.01, ***p<0.001). (C) On day 4 after immunization, mice were injected with CFSE^low target cells (loaded with OVA_257–264) and CFSE^high control cells (each 10⁷ cells) derived from syngeneic Ly-5.1⁺ mice. 4 h later, splenocytes were isolated and frequencies of CFSE-labeled cell populations were assessed by flow cytometry. Upper panel: Data represent mean±SEM of two independent experiments. Statistical significant differences between groups are indicated (*p<0.05, **p<0.01). Lower panel: Frequencies of Ly-5.1⁺ target cells (CFSE^low) and control cells (CFSE^high) in spleen cell suspensions derived from one mouse of either group are shown as histograms. Graphs are representative of two independent experiments.