Immunotherapeutic effects of IL-7 during a chronic viral infection in mice - PubMed (original) (raw)

Immunotherapeutic effects of IL-7 during a chronic viral infection in mice

Som G Nanjappa et al. Blood. 2011.

Abstract

Viral persistence during chronic viral infections is associated with a progressive loss of T-cell effector function called functional exhaustion. There is therefore a need to develop immunotherapies to remediate the functional deficits of T cells during these infections. We investigated the immunotherapeutic effects of IL-7 during chronic lymphocytic choriomeningitis virus infection in mice. Our results showed that the effects of IL-7 on T cells depend on the viral load, timing, and duration of treatment during the course of the infection. We document that the effectiveness of IL-7 was constrained by high viral load early in the infection, but treatment for at least 3 weeks during declining viral titers mitigated the programmed contraction of CD8 T cells, markedly enhanced the number of high-quality polyfunctional virus-specific CD8 T cells with a nonexhausted phenotype, and accelerated viral control. Mechanistically, the enhancement of CD8 T-cell responses by IL-7 was associated with increased proliferation and induction of Bcl-2, but not with altered levels of PD-1 or Cbl-b. In summary, our results strongly suggest that IL-7 therapy is a potential strategy to bolster the quality and quantity of T-cell responses in patients with chronic viral infections.

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Figures

Figure 1

Figure 1

Effect of IL-7 treatment during early contraction phase on the CD8 T-cell response. Cohorts of LCMV-Clone 13–infected mice were treated daily with either IL-7 or PBS between days 8 and 15 PI, as depicted by the shaded area (A). At days 8 (before IL-7 therapy), 16 (1 day after completion of therapy), and 40 (25 days after cessation of IL-7 therapy) PI, the numbers of naive (CD44lo) and activated (CD44hi) CD8 or CD4 T cells (B) and LCMV epitope-specific, IFNγ-producing CD8 or CD4 T cells (C) in IL-7- (●) or PBS (▴)-treated mice were quantified by flow cytometry. Data for each time point were obtained from 4-5 mice per group. *P ≤ .05; **P ≤ .005.

Figure 2

Figure 2

IL-7 therapy during the late contraction phase augments LCMV-specific T-cell responses. LCMV-Clone 13–infected mice were treated daily with either IL-7 or PBS between days 15 and 25 PI, as illustrated by the shaded area (A). At days 8, 26 (1 day after cessation of therapy), 45 (20 days after completion of IL-7 therapy), and 85 (60 days after IL-7 therapy) PI, CD8 and CD4 T-cell responses in the spleens of IL-7 (●)– or PBS (▴)–treated mice were quantified by flow cytometry. (B) The numbers of naive and activated CD8 or CD4 T cells. (C) LCMV epitope-specific CD8/CD4 T cells were quantified by intracellular staining for IFNγ. Data for each time point was obtained from 4-5 mice per group. *P ≤ .05; **P ≤ .005; ***P ≤ .001.

Figure 3

Figure 3

Extended duration of IL-7 therapy during clonal contraction enhances the LCMV-specific T-cell response. Cohorts of LCMV-Clone 13–infected mice were treated daily with either IL-7 or PBS between days 8 and 30 PI, as illustrated by the shaded area (A). At days 8, 31, 44, and 90 PI, LCMV-specific CD8 and CD4 T-cell responses were quantified by flow cytometry. (B) The kinetics of naive and activated CD8 or CD4 T cells in IL-7– and PBS–treated mice. (C) LCMV epitope-specific CD8 and CD4 T cells were quantified by staining for intracellular IFNγ. Data for each time point was obtained from an analysis of 4-5 IL-7 (●)– or PBS (▴)–treated mice and are representative of 2 experiments. *P ≤ .05; **P ≤ .005; ***P ≤ .001.

Figure 4

Figure 4

Extended duration of IL-7 treatment during the clonal contraction phase alters phenotypic attributes of LCMV-specific CD8 T cells. Mice were infected with LCMV-Clone 13 and treated with either IL-7 or PBS between days 8 and 30 PI, as described in Figure 3. At day 31 PI, splenocytes were stained with anti-CD8, anti-CD44, and Db/GP33 tetramers in combination with antibodies against KLRG-1, CD127, CD122, CD43, PD-1, and LAG-3 (A-C). Splenocytes were stained with anti-CD8, Db/GP33 tetramers, and antibodies against intracellular Bcl-2, Cbl-b, and Ki-67 molecules (D). Data were analyzed by flow cytometry, and the FACS plots are gated on tetramer-binding CD8 T cells. The numbers in panels A, C, and D are the mean fluorescence intensity (MFI) and/or percentages among tetramer-binding CD8 T cells. Data are from analysis of 4-5 IL-7–treated (black line) or PBS-treated (gray line) mice and are representative of 2 experiments. Stainings with anti–Cbl-b antibodies after incubation with the specific immunogenic Cbl-b peptide are shown as dotted lines. *P ≤ .05; **P ≤ .005; ***P ≤ .001.

Figure 5

Figure 5

Extended duration of IL-7 treatment during the clonal contraction phase results in durable enhancement of the quality of LCMV-specific CD8 T cells. Mice were infected with LCMV-Clone 13 and treated with either IL-7 (●) or PBS (▴) between days 8 and 30 PI, as described in Figure 3. At days 8, 31, 44, and 90 PI, LCMV-specific CD8− and CD4− T-cell responses in the spleen were assessed by flow cytometry. LCMV epitope–specific, triple cytokine (IFNγ, TNFα, and IL-2)–producing cells were enumerated by intracellular staining (A-B). (A) The percentages of triple cytokine–producing cells of epitope-specific CD8 or CD4 T cells at different days PI. (B) The total numbers of triple cytokine–producing epitope-specific CD8 or CD4 cells. *P ≤ .05; **P ≤ .005; ***P ≤ .001.

Figure 6

Figure 6

Extended duration of IL-7 treatment during the clonal contraction phase alters the phenotypic attributes of LCMV-specific CD8 T cells. Mice were infected with LCMV-Clone 13 and treated with either IL-7 or PBS between days 8 and 30 PI, as described in Figure 3. At day 90 PI, splenocytes were stained with anti-CD8, anti-CD44, anti-CD122, anti-CD127, anti-CD62L, anti-KLRG-1, anti–Cbl-b, anti-PD-1, and Db/GP33 tetramers (A-C). (D) At day 44 PI (14 days after cessation of IL-7 therapy), splenocytes were incubated with anti-CD107a (anti–LAMP-1) and DbGP33 tetramer and stimulated with LCMV-specific cognate peptide for 1 hour at 37°C. After incubation, cells were washed and stained with anti-CD8 antibody. Data were analyzed by flow cytometry, and FACS plots were gated on tetramer-binding CD8 T cells. The numbers in panels A and B are the mean fluorescence intensity (MFI) and/or percentages of tetramer-binding CD8 T cells. Data are from an analysis of 4-5 IL-7–treated (black line) or PBS-treated (gray line) mice. Stainings with anti–Cbl-b antibodies preincubated with the specific immunogenic Cbl-b peptide are shown as dotted lines. *P ≤ .05; **P ≤ .005; ***P ≤ .001.

Figure 7

Figure 7

Extended duration of IL-7 treatment after the clonal expansion phase promotes accelerated viral clearance. Mice were infected with LCMV-Clone 13 and treated with either IL-7 or PBS as described in Figure 3. At days 8, 31, 44, and 90 PI, the virus titers in tissues of IL-7–treated or PBS-treated mice were quantified by plaque assay. Panel A shows virus titers in serum, lungs, and liver at different days PI in PBS- or IL-7–treated mice, and panel B illustrates the overall kinetics of viral clearance.

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