Binding of HBsAg-specific pentamers on CD8+ T cells in a subject injected with 100 μg IMP321. PBMC from a naïve HLA-A2+ volunteer collected at baseline, on D57 and D85 were thawed and cultured with two HLA-A2-restricted HBsAg peptides in the presence of IL-2 for 10 days. Fresh autologous PBMC loaded with the two peptides were added to the culture for the second round of stimulation, and the culture was maintained for another 10 days. Cells were then incubated with two HBsAg peptides/HLA-A2 pentamers, washed and stained with CD3, CD4, CD8, CD14 specific antibodies. Percentage of CD3+CD8+ cells stained by the pentamers was analysed by flow cytometry after exclusion of CD14+cells. Dot plots showing the binding of HBsAg-pentamers on CD8+ T cells on D1 (Panel A) and D57 (Panel B) after two rounds of stimulation and on D85 after one round of stimulation are presented.