Figure 1.

Study design and simian immunodeficiency virus (SIV)-specific immune responses elicited by vaccination. (a) Immunization regimens. The long arrows represent vaccination and challenge time. The short arrows represent time of collection of rectal and vaginal pinches biopsies. Mamu-A*01⁺ animals in each group are identified with bold character. (b) p27 Gag and gp120 Env lymphoproliferative responses following MVA-SIV immunization (see (a) and arrows) of vaccinated macaques. The lines represent the average of the seven vaccinated animals. Intracellular cytokine staining on peripheral blood mononuclear cells (PBMCs) at week 55 (c) and 72 (d, e). Bars represent the average frequency of CD8⁺ and CD4⁺ T cells that produce interferon (IFN)-γ or interleukin (IL)-2. Values are expressed as percentage of cytokine-positive cells with background subtracted. (f) Immune response to SIV Gag measured by IFN-γ ELISPOT assay in fresh PBMCs following a stimulation with overlapping Gag and Env peptide pools. Data are expressed as number of spots per 10⁶ cells. The line represents the average and standard deviation for all the seven vaccinated (VACC) animals. (g) Frequency Gag181 tetramer⁺ CD8⁺ T-memory cells (line) central memory (CM=dark bars) or effectors (white bars) in blood. Line and bars represent the average±the standard deviation of the three Mamu-A*01⁺ animals in the vaccinated (VACC) group. (h) Expansion of central memory (T_CM) Gag181 tetramer ⁺ CD8⁺ T cells following infection with SIV_mac251 in the blood of vaccinated (n=3) and mock-vaccinated (n=2) macaques. T_CM are defined as CD28⁺/CD95⁺ CM9⁺ CD8 T cells. Bars represent the average of the frequency of T_CM within the tetramer-positive population±standard deviation. (i) Staining of purified mononuclear cells obtained from rectal mucosa biopsies with the CM9 tetramer. Raw data on central memory and effector memory CM9⁺ T cells in two vaccinated and two control macaques. Mean values of total memory CM9⁺ cells obtained from vaccinated macaques 902L, 906L and 314M and from control animals 224M and 300M (j). (k) Intracellular cytokine staining. Bars represent the average of the frequency of IL-2-producing CD8⁺ T cells following in vitro stimulation with gag, env, pol peptides in six vaccinated animals and four mock-vaccinated animals, at week 12 (left panel) and week 16 (right panel) after infection. For each animal the background frequency of cytokine production was subtracted from the positive samples prior calculation of the average.