The innate recognition of fungi by leukocytes is mediated by pattern recognition receptors (PRR), such as Dectin-1, and is thought to occur at the cell surface triggering intracellular signalling cascades which lead to the induction of protective host responses. In the lung, this recognition is aided by surfactant which also serves to maintain the balance between inflammation and pulmonary function, although the underlying mechanisms are unknown. Here we have explored pulmonary innate recognition of a variety of fungal particles, including zymosan, Candida albicans and Aspergillus fumigatus, and demonstrate that opsonisation with surfactant components can limit inflammation by reducing host-cell fungal interactions. However, we found that this opsonisation does not contribute directly to innate fungal recognition and that this process is mediated through non-opsonic PRRs, including Dectin-1. Moreover, we found that pulmonary inflammatory responses to resting Aspergillus conidia were initiated by these PRRs in acidified phagolysosomes, following the uptake of fungal particles by leukocytes. Our data therefore provides crucial new insights into the mechanisms by which surfactant can maintain pulmonary function in the face of microbial challenge, and defines the phagolysosome as a novel intracellular compartment involved in the innate sensing of extracellular pathogens in the lung.
References
[1]
Brown GD (2011) Innate Antifungal Immunity: The Key Role of Phagocytes. Annu Rev Immunol 29: 1–21.
[2]
Drummond RA, Brown GD (2011) The role of Dectin-1 in the host defence against fungal infections. Curr Opin Microbiol.
[3]
Werner JL, Metz AE, Horn D, Schoeb TR, Hewitt MM, et al. (2009) Requisite role for the dectin-1 beta-glucan receptor in pulmonary defense against Aspergillus fumigatus. J Immunol 182: 4938–4946.
[4]
Medzhitov R (2007) Recognition of microorganisms and activation of the immune response. Nature 449: 819–826.
[5]
Wright JR (2005) Immunoregulatory functions of surfactant proteins. Nat Rev Immunol 5: 58–68.
Shepherd VL (2002) Distinct roles for lung collectins in pulmonary host defense. Am J Respir Cell Mol Biol 26: 257–260.
[8]
Gardai SJ, Xiao YQ, Dickinson M, Nick JA, Voelker DR, et al. (2003) By binding SIRPalpha or calreticulin/CD91, lung collectins act as dual function surveillance molecules to suppress or enhance inflammation. Cell 115: 13–23.
[9]
Brown GD (2006) Dectin-1: a signalling non-TLR pattern-recognition receptor. Nat Rev Immunol 6: 33–43.
[10]
Pastva AM, Wright JR, Williams KL (2007) Immunomodulatory roles of surfactant proteins A and D: implications in lung disease. Proc Am Thorac Soc 4: 252–257.
[11]
Allen MJ, Voelker DR, Mason RJ (2001) Interactions of surfactant proteins A and D with Saccharomyces cerevisiae and Aspergillus fumigatus. Infect Immun 69: 2037–2044.
[12]
Lekkala M, LeVine AM, Linke MJ, Crouch EC, Linders B, et al. (2006) Effect of lung surfactant collectins on bronchoalveolar macrophage interaction with Blastomyces dermatitidis: inhibition of tumor necrosis factor alpha production by surfactant protein D. Infect Immun 74: 4549–4556.
[13]
Taylor PR, Tsoni SV, Willment JA, Dennehy KM, Rosas M, et al. (2007) Dectin-1 is required for beta-glucan recognition and control of fungal infection. Nat Immunol 8: 31–38.
[14]
Dagenais TR, Keller NP (2009) Pathogenesis of Aspergillus fumigatus in Invasive Aspergillosis. Clin Microbiol Rev 22: 447–465.
[15]
Madan T, Eggleton P, Kishore U, Strong P, Aggrawal SS, et al. (1997) Binding of pulmonary surfactant proteins A and D to Aspergillus fumigatus conidia enhances phagocytosis and killing by human neutrophils and alveolar macrophages. Infect Immun 65: 3171–3179.
[16]
Steele C, Rapaka RR, Metz A, Pop SM, Williams DL, et al. (2005) The Beta-Glucan Receptor Dectin-1 Recognizes Specific Morphologies of Aspergillus fumigatus. PLoS Pathog 1: e42.
[17]
Luther K, Torosantucci A, Brakhage AA, Heesemann J, Ebel F (2007) Phagocytosis of Aspergillus fumigatus conidia by murine macrophages involves recognition by the dectin-1 beta-glucan receptor and Toll-like receptor 2. Cell Microbiol 9: 368–381.
[18]
Madan T, Reid KB, Clark H, Singh M, Nayak A, et al. (2010) Susceptibility of mice genetically deficient in SP-A or SP-D gene to invasive pulmonary aspergillosis. Mol Immunol 47: 1923–1930.
[19]
Asmus MJ, Barros MD, Liang J, Chesrown SE, Hendeles L (2001) Pulmonary function response to EDTA, an additive in nebulized bronchodilators. J Allergy Clin Immunol 107: 68–72.
[20]
Evans SE (2010) Coping with Candida infections. Proc Am Thorac Soc 7: 197–203.
[21]
van Rozendaal BA, van Spriel AB, van De Winkel JG, Haagsman HP (2000) Role of pulmonary surfactant protein D in innate defense against Candida albicans. J Infect Dis 182: 917–922.
[22]
Kelly MM, McNagny K, Williams DL, van Rooijen N, Maxwell L, et al. (2008) The lung responds to zymosan in a unique manner independent of toll-like receptors, complement, and dectin-1. Am J Respir Cell Mol Biol 38: 227–238.
[23]
Underhill DM (2003) Macrophage recognition of zymosan particles. J Endotoxin Res 9: 176–180.
[24]
Robinson MJ, Osorio F, Rosas M, Freitas RP, Schweighoffer E, et al. (2009) Dectin-2 is a Syk-coupled pattern recognition receptor crucial for Th17 responses to fungal infection. J Exp Med 206: 2037–2051.
[25]
Aimanianda V, Bayry J, Bozza S, Kniemeyer O, Perruccio K, et al. (2009) Surface hydrophobin prevents immune recognition of airborne fungal spores. Nature 460: 1117–1121.
[26]
Hohl TM, Van Epps HL, Rivera A, Morgan LA, Chen PL, et al. (2005) Aspergillus fumigatus Triggers Inflammatory Responses by Stage-Specific beta-Glucan Display. PLoS Pathog 1: e30.
[27]
Philippe B, Ibrahim-Granet O, Prevost MC, Gougerot-Pocidalo MA, Sanchez Perez M, et al. (2003) Killing of Aspergillus fumigatus by alveolar macrophages is mediated by reactive oxidant intermediates. Infect Immun 71: 3034–3042.
[28]
Hernanz-Falcon P, Joffre O, Williams DL, Reis e Sousa C (2009) Internalization of Dectin-1 terminates induction of inflammatory responses. Eur J Immunol 39: 507–513.
[29]
Ibrahim-Granet O, Philippe B, Boleti H, Boisvieux-Ulrich E, Grenet D, et al. (2003) Phagocytosis and intracellular fate of Aspergillus fumigatus conidia in alveolar macrophages. Infect Immun 71: 891–903.
[30]
Thywissen A, Heinekamp T, Dahse HM, Schmaler-Ripcke J, Nietzsche S, et al. (2011) Conidial Dihydroxynaphthalene Melanin of the Human Pathogenic Fungus Aspergillus fumigatus Interferes with the Host Endocytosis Pathway. Front Microbiol 2: 96.
[31]
Blander JM, Medzhitov R (2004) Regulation of phagosome maturation by signals from toll-like receptors. Science 304: 1014–1018.
[32]
Heinsbroek SE, Taylor PR, Martinez FO, Martinez-Pomares L, Brown GD, et al. (2008) Stage-specific sampling by pattern recognition receptors during Candida albicans phagocytosis. PLoS Pathog 4: e1000218.
[33]
Flannagan RS, Cosio G, Grinstein S (2009) Antimicrobial mechanisms of phagocytes and bacterial evasion strategies. Nature Reviews Microbiology 7: 355–366.
[34]
Dennehy KM, Ferwerda G, Faro-Trindade I, Pyz E, Willment JA, et al. (2008) Syk kinase is required for collaborative cytokine production induced through Dectin-1 and Toll-like receptors. Eur J Immunol 38: 500–506.
[35]
Gringhuis SI, den Dunnen J, Litjens M, van der Vlist M, Wevers B, et al. (2009) Dectin-1 directs T helper cell differentiation by controlling noncanonical NF-kappaB activation through Raf-1 and Syk. Nat Immunol.
[36]
Gross O, Gewies A, Finger K, Schafer M, Sparwasser T, et al. (2006) Card9 controls a non-TLR signalling pathway for innate anti-fungal immunity. Nature 442: 651–656.
[37]
Goodridge HS, Shimada T, Wolf AJ, Hsu YM, Becker CA, et al. (2009) Differential use of CARD9 by Dectin-1 in macrophages and dendritic cells. J Immunol 182: 1146–1154.
[38]
Brown GD, Herre J, Williams DL, Willment JA, Marshall ASJ, et al. (2003) Dectin-1 mediates the biological effects of beta-glucan. J Exp Med 197: 1119–1124.
[39]
Brown GD, Taylor PR, Reid DM, Willment JA, Williams DL, et al. (2002) Dectin-1 is a major beta-glucan receptor on macrophages. J Exp Med 296: 407–412.
[40]
Crouch E, Wright JR (2001) Surfactant proteins a and d and pulmonary host defense. Annu Rev Physiol 63: 521–554.
[41]
Haagsman HP, Hogenkamp A, van Eijk M, Veldhuizen EJ (2008) Surfactant collectins and innate immunity. Neonatology 93: 288–294.
[42]
Kishore U, Reid KB (2007) Collectins and Pentraxins. In: Brown G, Netea M, editors. Immunology of fungal infections. Dordrecht: Springer. pp. 151–176.
[43]
Allen MJ, Harbeck R, Smith B, Voelker DR, Mason RJ (1999) Binding of rat and human surfactant proteins A and D to Aspergillus fumigatus conidia. Infect Immun 67: 4563–4569.
[44]
Singh M, Madan T, Waters P, Sonar S, Singh SK, et al. (2009) Therapeutic effects of recombinant forms of full-length and truncated human surfactant protein D in a murine model of invasive pulmonary aspergillosis. Mol Immunol 46: 2363–2369.
[45]
Yamasaki S, Matsumoto M, Takeuchi O, Matsuzawa T, Ishikawa E, et al. (2009) C-type lectin Mincle is an activating receptor for pathogenic fungus, Malassezia. Proc Natl Acad Sci U S A 106: 1897–1902.
[46]
Ewald SE, Lee BL, Lau L, Wickliffe KE, Shi GP, et al. (2008) The ectodomain of Toll-like receptor 9 is cleaved to generate a functional receptor. Nature 456: 658–662.
[47]
Ramirez-Ortiz ZG, Specht CA, Wang JP, Lee CK, Bartholomeu DC, et al. (2008) Toll-like receptor 9-dependent immune activation by unmethylated CpG motifs in Aspergillus fumigatus DNA. Infect Immun 76: 2123–2129.
[48]
Kasperkovitz PV, Cardenas ML, Vyas JM (2010) TLR9 is actively recruited to Aspergillus fumigatus phagosomes and requires the N-terminal proteolytic cleavage domain for proper intracellular trafficking. J Immunol 185: 7614–7622.
[49]
Ip WK, Sokolovska A, Charriere GM, Boyer L, Dejardin S, et al. (2010) Phagocytosis and phagosome acidification are required for pathogen processing and MyD88-dependent responses to Staphylococcus aureus. J Immunol 184: 7071–7081.
[50]
Shimada T, Park BG, Wolf AJ, Brikos C, Goodridge HS, et al. (2010) Staphylococcus aureus evades lysozyme-based peptidoglycan digestion that links phagocytosis, inflammasome activation, and IL-1beta secretion. Cell Host Microbe 7: 38–49.
[51]
Maxeiner JH, Karwot R, Hausding M, Sauer KA, Scholtes P, et al. (2007) A method to enable the investigation of murine bronchial immune cells, their cytokines and mediators. Nat Protoc 2: 105–112.
[52]
Stokes RW, Thorson LM, Speert DP (1998) Nonopsonic and opsonic association of Mycobacterium tuberculosis with resident alveolar macrophages is inefficient. J Immunol 160: 5514–5521.
[53]
Taylor PR, Brown GD, Geldhof AB, Martinez-Pomares L, Gordon S (2003) Pattern recognition receptors and differentiation antigens define murine myeloid cell heterogeneity ex vivo. Eur J Immunol 33: 2090–2097.
[54]
Tsoni SV, Kerrigan AM, Marakalala MJ, Srinivasan N, Duffield M, et al. (2009) Complement C3 plays an essential role in the control of opportunistic fungal infections. Infect Immun 77: 3679–3685.
[55]
Fernandez-Mora E, Polidori M, Luhrmann A, Schaible UE, Haas A (2005) Maturation of Rhodococcus equi-containing vacuoles is arrested after completion of the early endosome stage. Traffic 6: 635–653.
[56]
Graham LM, Tsoni SV, Willment JA, Williams DL, Taylor PR, et al. (2006) Soluble Dectin-1 as a tool to detect beta-glucans. J Immunol Methods 314: 164–169.
