Figure 6.

Soluble PD-L1 ectodomain co-expression enhances Env-specific immune responses. (A) Percentage of CD4+ T cells producing IFNγ after in vitro stimulation with HIV Env T helper peptide (measured by intracellular cytokine staining) in mice two weeks after immunization. Shown are mean values with SEM (n = 6) and significant differences between groups (one-way ANOVA analyses followed by Tukey’s multiple comparison test; * p < 0.05). (B) Frequency of regulatory T cells in the spleen of BALB/c mice 20 weeks after boosting. Shown are mean values with SEM of 18 animals from three independent experiments and significant differences between groups (one-way ANOVA analyses followed by Tukey’s multiple comparison test; * p < 0.05). (C) Quantitative Env-specific IgG2a antibody responses in the sera of BALB/c mice over a time-period of 18 weeks. Shown are mean values with SEM of 18 animals from three independent experiments and significant differences between groups (one-way ANOVA analyses followed by Tukey’s multiple comparison test; * p < 0.05). (D) Antibody subtype patterns of Env-immunized mice two (week 6) and 14 weeks (week 18) after the prime-booster immunization regimen. The ring size represents the overall antibody response. Shown are the mean percentages (n = 6) of each subtype based on the overall antibody response of a representative experiment (from three independent experiments). Each subtype was analyzed by ELISA with identical amounts of HRP-conjugated anti-mouse IgG1 (blue), IgG2a (red), IgG2b (gray), and IgG3 (black) antibodies.