Figure 4.

Magnitude of T cell responses to specific vaccine components. T cell responses were measured by intracellular cytokine staining (ICS) assay to detect interferon (IFN)–γ and/or interleukin-2 and by IFN-γ enzyme-linked immunospot (ELISpot) assay for all placebo and vaccine recipients. A, Median magnitudes of peptide pool–specific responses, shown as a percentage of total CD4⁺ or CD8⁺ T cells for the ICS assay (scale 0–0.1) and as the no. of spot-forming cells per 10⁶ peripheral-blood mononuclear cells (PBMCs) for the ELISpot assay (scale 0–150), for all subjects, by dose group. The time course for each subject is shown by study week on the X-axis; arrows along the top of the graph designate time points for immunizations (study weeks 0, 4, and 8). Within each of the 24 boxes, the entire time course of the study is represented. Each column shows the responses to a peptide pool representing the respective vaccine antigens (EnvA, EnvB, EnvC, Gag, Nef, and Pol). Each row represents a dose cohort (placebo recipients, 2-mg recipients, 4-mg recipients, and 8-mg recipients). Red bars represent CD4⁺ T cell responses as measured by ICS assay, green bars represent CD8⁺ T cell responses as measured by ICS assay, and blue bars represent CD4⁺ or CD8⁺ T cell responses as measured by ELISpot assay. Time points without samples for analysis are represented by asterisks. B, Magnitudes of specific T cell responses to a peptide pool for EnvA at study week 12, by dose group. EnvA-specific responses are shown for each subject as measured by 3 assays; shown are the percentages of CD4⁺ or CD8⁺ T cells producing cytokine as measured by ICS assay and the no. of spot-forming cells per 10⁶ PBMCs as measured by ELISpot assay. The left plot shows EnvA-specific CD4⁺ T cell responses, the middle plot shows EnvA-specific CD8⁺ T cell responses, and the right plot shows EnvA-specific CD4⁺ or CD8⁺ responses. The box plots indicate the median, 25th, and 75th percentiles for each dose level, and the error bars show the 5th and 95th percentiles. The horizontal dashed line on each plot indicates the laboratory threshold of positivity for each assay (for the ICS assay, 0.0241% for CD4⁺ T cells and 0.0445% for CD8⁺ T cells; for the ELISpot assay, 50 sfc/10⁶ PBMCs).