Asthma is a chronic inflammatory disease of the airways characterized by variable airway obstruction and airway hyperresponsiveness (AHR). The T regulatory (Treg) cell subset is critically important for the regulation of immune responses. Adoptive transfer of Treg cells has been shown to be sufficient for the suppression of airway inflammation in experimental allergic asthma. Intervention strategies aimed at expanding the Treg cell population locally in the airways of sensitized individuals are therefore of high interest as a potential therapeutic treatment for allergic airway disease. Here, we aim to test whether long-term suppression of asthma manifestations can be achieved by locally expanding the Treg cell subset via intranasal administration of a TLR-2 agonist. To model therapeutic intervention aimed at expanding the endogenous Treg population in a sensitized host, we challenged OVA-sensitized mice by OVA inhalation with concomitant intranasal instillation of the TLR-2 agonist Pam3Cys, followed by an additional series of OVA challenges. Pam3Cys treatment induced an acute but transient aggravation of asthma manifestations, followed by a reduction or loss of AHR to methacholine, depending on the time between Pam3Cys treatment and OVA challenges. In addition, Pam3Cys-treatment induced significant reductions of eosinophils and increased numbers of Treg cells in the lung infiltrates. Our data show that, despite having adverse acute effects, TLR2 agonist treatment as a therapeutic intervention induces an expansion of the Treg cell population in the lungs and results in long-term protection against manifestation of allergic asthma upon subsequent allergen provocation. Our data indicate that local expansion of Tregs in allergic airway disease is an interesting therapeutic approach that warrants further investigation.
References
[1]
Kearley J, Robinson DS, Lloyd CM (2008) CD4+CD25+ regulatory T cells reverse established allergic airway inflammation and prevent airway remodeling. J Allergy Clin Immunol 122: 617–624.
[2]
Lewkowich IP, Herman NS, Schleifer KW, Dance MP, Chen BL, et al. (2005) CD4+CD25+ T cells protect against experimentally induced asthma and alter pulmonary dendritic cell phenotype and function. J Exp Med 202: 1549–1561.
[3]
Jaffar Z, Sivakuru T, Roberts K (2004) CD4+CD25+ T cells regulate airway eosinophilic inflammation by modulating the Th2 cell phenotype. J Immunol 172: 3842–3849.
[4]
Xystrakis E, Urry Z, Hawrylowicz CM (2007) Regulatory T cell therapy as individualized medicine for asthma and allergy. Curr Opin Allergy Clin Immunol 7: 535–541.
[5]
Ryanna K, Stratigou V, Safinia N, Hawrylowicz C (2009) Regulatory T cells in bronchial asthma. Allergy 64: 335–347.
[6]
Sutmuller RP, den Brok MH, Kramer M, Bennink EJ, Toonen LW, et al. (2006) Toll-like receptor 2 controls expansion and function of regulatory T cells. J Clin Invest 116: 485–494.
[7]
Iwasaki A, Medzhitov R (2004) Toll-like receptor control of the adaptive immune responses. Nat Immunol 5: 987–995.
[8]
Lien E, Sellati TJ, Yoshimura A, Flo TH, Rawadi G, et al. (1999) Toll-like receptor 2 functions as a pattern recognition receptor for diverse bacterial products. J Biol Chem 274: 33419–33425.
[9]
Wang Q, McLoughlin RM, Cobb BA, Charrel-Dennis M, Zaleski KJ, et al. (2006) A bacterial carbohydrate links innate and adaptive responses through toll-like receptor 2. J Exp Med 203: 2853–2863.
[10]
Ouabed A, Hubert FX, Chabannes D, Gautreau L, Heslan M, et al. (2008) Differential control of T regulatory cell proliferation and suppressive activity by mature plasmacytoid versus conventional spleen dendritic cells. J Immunol 180: 5862–5870.
[11]
Chen W, Liang X, Peterson AJ, Munn DH, Blazar BR (2008) The indoleamine 2,3-dioxygenase pathway is essential for human plasmacytoid dendritic cell-induced adaptive T regulatory cell generation. J Immunol 181: 5396–5404.
[12]
Liu G, Zhao Y (2007) Toll-like receptors and immune regulation: Their direct and indirect modulation on regulatory CD4+ CD25+ T cells. Immunology 122: 149–156.
[13]
Sutmuller RP, Morgan ME, Netea MG, Grauer O, Adema GJ (2006) Toll-like receptors on regulatory T cells: Expanding immune regulation. Trends Immunol 27: 387–393.
[14]
Caramalho I, Lopes-Carvalho T, Ostler D, Zelenay S, Haury M, et al. (2003) Regulatory T cells selectively express toll-like receptors and are activated by lipopolysaccharide. J Exp Med 197: 403–411.
[15]
Crellin NK, Garcia RV, Hadisfar O, Allan SE, Steiner TS, et al. (2005) Human CD4+ T cells express TLR5 and its ligand flagellin enhances the suppressive capacity and expression of FOXP3 in CD4+CD25+ T regulatory cells. J Immunol 175: 8051–8059.
[16]
Peng G, Guo Z, Kiniwa Y, Voo KS, Peng W, et al. (2005) Toll-like receptor 8-mediated reversal of CD4+ regulatory T cell function. Science 309: 1380–1384.
[17]
Liu H, Komai-Koma M, Xu D, Liew FY (2006) Toll-like receptor 2 signaling modulates the functions of CD4+ CD25+ regulatory T cells. Proc Natl Acad Sci U S A 103: 7048–7053.
[18]
Armstrong L, Medford AR, Uppington KM, Robertson J, Witherden IR, et al. (2004) Expression of functional toll-like receptor-2 and -4 on alveolar epithelial cells. Am J Respir Cell Mol Biol 31: 241–245.
[19]
Chen Q, Davidson TS, Huter EN, Shevach EM (2009) Engagement of TLR2 does not reverse the suppressor function of mouse regulatory T cells, but promotes their survival. J Immunol 183: 4458–4466.
[20]
Inman MD (2010) Trends and recommendations in studies of mouse airway function. Clin Exp Allergy 40: 524–527.
[21]
Burchell JT, Wikstrom ME, Stumbles PA, Sly PD, Turner DJ (2009) Attenuation of allergen-induced airway hyperresponsiveness is mediated by airway regulatory T cells. Am J Physiol Lung Cell Mol Physiol 296: L307–L319.
[22]
Cabanski M, Steinmuller M, Marsh LM, Surdziel E, Seeger W, et al. (2008) PKR regulates TLR2/TLR4-dependent signaling in murine alveolar macrophages. Am J Respir Cell Mol Biol 38: 26–31.
[23]
Muir A, Soong G, Sokol S, Reddy B, Gomez MI, et al. (2004) Toll-like receptors in normal and cystic fibrosis airway epithelial cells. Am J Respir Cell Mol Biol 30: 777–783.
[24]
Ueno K, Koga T, Kato K, Golenbock DT, Gendler SJ, et al. (2008) MUC1 mucin is a negative regulator of toll-like receptor signaling. Am J Respir Cell Mol Biol 38: 263–268.
[25]
Gomez MI, Prince A (2008) Airway epithelial cell signaling in response to bacterial pathogens. Pediatr Pulmonol 43: 11–19.
[26]
Chun J, Prince A (2009) TLR2-induced calpain cleavage of epithelial junctional proteins facilitates leukocyte transmigration. Cell Host Microbe 5: 47–58.
[27]
Issa R, Sorrentino R, Sukkar MB, Sriskandan S, Chung KF, et al. (2008) Differential regulation of CCL-11/eotaxin-1 and CXCL-8/IL-8 by gram-positive and gram-negative bacteria in human airway smooth muscle cells. Respir Res 9 (1465–993): 30.
[28]
Wong CK, Cheung PF, Ip WK, Lam CW (2007) Intracellular signaling mechanisms regulating toll-like receptor-mediated activation of eosinophils. Am J Respir Cell Mol Biol 37: 85–96.
[29]
Agrawal S, Agrawal A, Doughty B, Gerwitz A, Blenis J, et al. (2003) Cutting edge: Different toll-like receptor agonists instruct dendritic cells to induce distinct th responses via differential modulation of extracellular signal-regulated kinase-mitogen-activated protein kinase and c-fos. J Immunol 171: 4984–4989.
[30]
Dillon S, Agrawal A, van DT, Landreth G, McCauley L, et al. (2004) A toll-like receptor 2 ligand stimulates Th2 responses in vivo, via induction of extracellular signal-regulated kinase mitogen-activated protein kinase and c-fos in dendritic cells. J Immunol 172: 4733–4743.
[31]
Boudousquie C, Pellaton C, Barbier N, Spertini F (2009) CD4+CD25+ T cell depletion impairs tolerance induction in a murine model of asthma. Clin Exp Allergy 39: 1415–1426.
[32]
Maazi H, Shirinbak S, Willart M, Hammad HM, Cabanski M, et al. (2012) Contribution of regulatory T cells to alleviation of experimental allergic asthma after specific immunotherapy. Clin Exp Allergy 42: 1519–1528.
[33]
Baru AM, Ganesh V, Krishnaswamy JK, Hesse C, Untucht C, et al. (2012) Absence of Foxp3+ regulatory T cells during allergen provocation does not exacerbate murine allergic airway inflammation. PLoS One 7: e47102.
[34]
Fuchs B, Braun A (2008) Modulation of asthma and allergy by addressing toll-like receptor 2. J Occup Med Toxicol 3 Suppl 1S5.
[35]
Redecke V, Hacker H, Datta SK, Fermin A, Pitha PM, et al. (2004) Cutting edge: Activation of toll-like receptor 2 induces a Th2 immune response and promotes experimental asthma. J Immunol 172: 2739–2743.
[36]
Patel M, Xu D, Kewin P, Choo-Kang B, McSharry C, et al. (2005) TLR2 agonist ameliorates established allergic airway inflammation by promoting Th1 response and not via regulatory T cells. J Immunol 174: 7558–7563.
[37]
Motta AC, Vissers JL, Gras R, Van Esch BC, Van Oosterhout AJ, et al. (2009) GITR signaling potentiates airway hyperresponsiveness by enhancing Th2 cell activity in a mouse model of asthma. Respir Res 10: 93.
[38]
Luhrmann A, Tschernig T, Pabst R, Niewiesk S (2005) Improved intranasal immunization with live-attenuated measles virus after co-inoculation of the lipopeptide MALP-2. Vaccine 23: 4721–4726.
[39]
Nawijn MC, Piavaux BJ, Jeurink PV, Gras R, Reinders MA, et al. (2011) Identification of the mhc region as an asthma susceptibility locus in recombinant congenic mice. Am J Respir Cell Mol Biol 45: 295–303.
[40]
Shirinbak S, Taher YA, Maazi H, Gras R, van Esch BC, et al. (2010) Suppression of Th2-driven airway inflammation by allergen immunotherapy is independent of B cell and ig responses in mice. J Immunol 185: 3857–3865.
