Altered balance between Th17 and Th1 cells at mucosal sites predicts AIDS progression in simian immunodeficiency virus-infected macaques

Abstract

Loss of CD4(+) T cells in the gut is necessary but not sufficient to cause AIDS in animal models, raising the possibility that a differential loss of CD4(+) T-cell subtypes may be important. We found that CD4(+) T cells that produce interleukin (IL)-17, a recently identified lineage of effector CD4(+) T-helper cells, are infected by SIV(mac251)in vitro and in vivo, and are found at lower frequency at mucosal and systemic sites within a few weeks from infection. In highly viremic animals, Th1 cells predominates over Th17 T cells and the frequency of Th17 cells at mucosal sites is negatively correlated with plasma virus level. Because Th17 cells play a central role in innate and adaptive immune response to extracellular bacteria, our finding may explain the chronic enteropathy in human immunodeficiency virus (HIV) infection. Thus, therapeutic approaches that reconstitute an adequate balance between Th1 and Th17 may be beneficial in the treatment of HIV infection.

Figure 1

The frequency of CD3⁺CD4⁺ IL-17⁺ T cells is significantly higher in mucosal than systemic tissues of healthy macaques. (a) Distinct CD3⁺ CD4⁺ T-cell population produces IL-17 only after PMA/ionomycin stimulation. CD3⁺ CD4⁺ T cells were obtained from blood of a naïve macaque. Left panel: unstimulated; middle and right panels: PMA/ionomycin stimulation, cells stained with anti-IL-17 antibody and isotype control, respectively. (b) PBMCs were obtained from a naïve macaque and stimulated with or without PMA/ionomycin and costained with IL-17 and IFN-γ. Left panel: unstimulated; right panel: PMA/ionomycin stimulation. (c) Most CD3⁺ CD4⁺ IL-17⁺ T cells are CD25⁻ following stimulation with PMA and ionomycin. (d) Percentage of CD4⁺ IL-17⁺ T cells in systemic and mucosal sites with or without PMA and ionomycin treatment. (e, f) Mean percentages of CD3⁺ CD4⁺ IL-17⁺ T cells (e) and CD3⁺ CD4⁺ IFN-γ⁺ T cells (f) in tissues of healthy macaques. The number of samples analyzed for each tissue varied from four to nine. BAL, bronchial aveolar lavage; IFN, interferon; IL, interleukin; PBMC, peripheral blood mononuclear cell; PMA, phorbol 12-myristate 13-acetate.

Figure 2

CD4⁺ IL-17⁺ T cells are susceptible to SIV_mac251 infection in vitro and in vivo. (a) Viral production measured as p27 Gag in the supernatant of infected cultures by ELISA. (b) Viral production measured by intracellular staining for p27 Gag in infected and mock-infected cultures. (c) IFN-γ and IL-17 production within cells that express p27 Gag. (d) Phenotype of sorted CD4⁺ CD28⁺ CD95⁺ cytokine-producing cells. (e) Quantitation of SIV proviral DNA copies in sorted T-cell populations. IFN, interferon; IL, interleukin; SIV, simian immunodeficiency virus.

Figure 3

Altered balance between CD4 ⁺ IL-17⁺ and CD4⁺ IFN- γ⁺ T cells in primary SIV_mac251 infection. (a) Plasma virus levels in macaques following intrarectal infection with SIV_mac251. (b, c) Mean percentages (b) and absolute number (c) of CD4⁺ IL-17⁺ and CD4⁺ IFN-γ ⁺ T cells in PBMCs from naïve and infected macaques at 2 weeks from infection. The number of samples analyzed varied from four to nine. (d–g) Mean percentages of CD4 ⁺ IL-17 ⁺ and CD4 ⁺ IFN-γ ⁺ T cells in pooled lymph nodes (d), jejunum (e), colon (f), and rectum (g) from naïve and infected macaques at 2 weeks from infection. The number of samples analyzed for each tissue varied from four to nine. IFN, interferon; IL, interleukin; PBMC, peripheral blood mononuclear cell; SIV, simian immunodeficiency virus; *MamuA-01⁺.

Figure 4

Frequency of Th17 and Th1 cells in chronically infected macaques. (a, b) Mean percentages (a) and absolute number (b) of CD4⁺ IL-17⁺ and CD4⁺ IFN- γ⁺ T cells in PBMCs from naïve and chronically SIV-infected macaques. The number of samples analyzed varied from 4 to 11. (c–f) Mean percentages of CD4⁺ IL-17⁺ and CD4⁺ IFN-γ⁺ T cells in pooled lymph nodes (c), jejunum (d), colon (e), and rectum (f) from naïve and chronically SIV-infected macaques. The number of samples analyzed for each tissue varied from 4 to 18. (g–i) Mean percentages of CD4⁺ IL-17⁺ T cells in jejunum (g), colon (h), and rectum (i) of naïve macaques and macaques with plasma virus levels below (elite controllers) or above 50 copies per ml. IFN, interferon; IL, interleukin; PBMC, peripheral blood mononuclear cell; SIV, simian immunodeficiency virus.

Figure 5

Correlative analysis of virus plasma levels and percentages of CD4⁺ IL-17⁺ T cells at mucosal sites or plasma LPS levels in infected macaques. (a) The frequency of Th17 cells in jejunum, rectum, pooled lymph nodes, and PBMCs was related to plasma virus levels (in log values) in the infected macaques. (b) The frequency of Th1 cells in jejunum and PBMCs was related to plasma virus levels (in log values) in the infected macaques. (c) The level of LPS in plasma was related to the frequency of Th17 cells in blood or spleen. No significant correlation was found in any tissue tested. IFN, interferon; IL, interleukin; LPS, lipopolysaccharide; PBMC, peripheral blood mononuclear cell.