DCLV prime/DCLV boost in combination with PD-L1 blockade broadened the profile of vaccine-specific T cell responses. Spleen cells harvested from DCLV/DCLV + αPD-L1, DCLV/DCLV + isotype, or the control group of BALB/c mice were pooled, stimulated in vitro with one of peptide pools for 18–24 hours, and assayed by IFN-γ ELISPOT. (a) Distribution of 123 15-mer peptides spanning the entire HIV-1 clade B Gag sequence into 23 pools (P1–P23) (left). Positively reactive peptide pools of DCLV/DCLV + αPD-L1 (coloring) and DCLV/DCLV + isotype (shading) groups are indicated (left) and summarized (right). (b) Number of spot-forming cells (SFC) produced by stimulation with each of the 23 pools. A peptide pool was regarded as a positive group when its ELISPOT readout was five times higher than the mean readout of the control group. Each group consisted of four mice. P values were calculated using one-way Anova followed by a Bonferroni nonparametric posttest (ns, not significant; *P < 0.05; **P < 0.01; ***P < 0.001). The data are representative of two independent experiments. DCLV, dendritic cell-directed lentiviral vector; ELISPOT, enzyme-linked immunosorbent spot; HIV, human immunodeficiency virus; PBS, phosphate-buffered saline; PD-L1, programmed death 1 ligand.