Human infections with influenza A virus (IAV) exhibit mild to severe clinical outcomes as a result of differential virus-host interactions. C-type lectin receptors (CLRs) are pattern recognition receptors that may sense carbohydrates, proteins, or lipids derived from infected hosts or the invading microbes including bacteria, viruses, fungi, or parasites. CLR-viral interaction may lead to increased viral entry and spread; furthermore, their interactions have been reported to trigger downstream signaling that further modulates host’s innate immune responses through the induction of pro-inflammatory cytokines. To date, DC-SIGN and DC-SIGNR have been shown to mediate IAV entry; however, the potential interactions between other human transmembrane CLRs with IAV have not yet been systematically investigated. We utilized lentiviral-based pseudoparticles expressing influenza hemagglutinin (HA) to examine the binding potential between HA and a panel of human CLRs expressed in soluble form. CLEC5A was identified as a potential interacting target with the HA proteins derived from a highly pathogenic avian H5N1 virus A/VN/1203/04 (VN1203) or a human seasonal H1N1 virus A/HK/54/98 (HK5498), albeit at different binding intensity. Applying siRNA gene silencing, we confirmed that CLEC5A did not enhance influenza entry in human monocytic U937 cells that constitutively express CLEC5A or in the lentiviral-transduced stable CHO and CHO-Lec2 cells that overly expressed CLEC5A. To investigate downstream signaling upon engagement of CLEC5A to influenza virus, M-CSF or GM-CSF differentiated human macrophages with high expression levels of CLEC5A and DAP12, a known adaptor protein for CLEC5A upon phosphorylation to initiate signal transduction, was subjected to CLEC5A siRNA gene silencing followed by infection with recombinant A/PR/8/34 virus expressing HA and NA derived from either VN1203 (H5N1) or HK5498 (H1N1) viruses. RG-PR8xVN1203HA,NA (H5N1) exhibited a higher infectivity and induced higher levels of pro-inflammatory cytokines (TNF-( and IFN-α) and chemokines (IP-10, MCP-1, MIG and MIP-1α) secretion in M-CSF or GM-CSF differentiated macrophages while compared to that of the RG-PR8xHK5498HA,NA (H1N1) virus. Knocking-down CLEC5A in macrophages led to a universal reduction of cytokines and chemokines secretion after infection with either the RG-PR8xVN1203HA,NA, RG-PR8xHK5498HA,NA, RG-A/VN/1203/04 (H5N1) or A/Shanghai/2/2014 (H7N9) viruses, suggesting that CLEC5A plays a role as cytokine and chemokine amplifier after influenza infection. Since DAP12 phosphorylation is known to activate downstream signaling via Spleen tyrosine kinase (Syk), pre-incubation of M-CSF macrophages with a Syk inhibitor (Bay 61-3606) also lead to a significant reduction of TNF-α and IP-10 in infected macrophages. A higher mortality was observed in CLEC5A-/- mice while compared to the wild-type C57BL/6 mice after challenged with a lethal dose of RG-A/VN/1203/04 (H5N1) influenza virus suggesting that CLEC5A as a host innate response amplifier play a protective role upon influenza infection. In conclusion, we have identified CLEC5A as a novel host factor for influenza pathogenesis by modulating host innate inflammatory response. / published_or_final_version / Public Health / Doctoral / Doctor of Philosophy

by Wang He-Xiang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 161-179). / ACKNOWLEDGEMENTS --- p.i / ABSTRACT --- p.ii / LIST OF CONTENTS --- p.v / LIST OF TABLES --- p.xi / LIST OF FIGURES --- p.xii / LIST OF ABBREVIATIONS --- p.xvi / Chapter CHAPTER 1. --- General Introduction --- p.1 / Chapter CHAPTER 2. --- Literature Review --- p.5 / Chapter 2.1. --- Lectins --- p.5 / Chapter 2.1.1. --- Aspects of lectins --- p.5 / Chapter 2.1.2. --- Isolation and purification of lectins --- p.8 / Chapter 2.1.3. --- Characteristics of lectins --- p.9 / Chapter 2.1.4. --- Effects of lectins on biological activities --- p.10 / Chapter 2.1.4.1. --- The role of lectins in plant defence --- p.11 / Chapter 2.1.4.2. --- The specificity of some legume lectins --- p.13 / Chapter 2.1.4.3. --- Some properties of animal lectins --- p.14 / Chapter 2.1.4.4. --- Hypotensive activity of the lectins --- p.18 / Chapter 2.1.4.5. --- Lectins in immunology --- p.20 / Chapter 2.2. --- Mushroom Lectins and Polysaccharides --- p.24 / Chapter 2.2.1. --- General aspects of mushroom lectins and polysaccharides --- p.24 / Chapter 2.2.2. --- Mushroom lectins --- p.25 / Chapter 2.2.2.1. --- Hericium erinaceum lectin --- p.26 / Chapter 2.2.2.2. --- Lactarius deterrimus lectin --- p.26 / Chapter 2.2.2.3. --- Laetiporus sulfureus lectin --- p.27 / Chapter 2.2.2.4. --- Grifola frondosa lectin --- p.28 / Chapter 2.2.2.5. --- Volvariella volvacea lectin --- p.28 / Chapter 2.2.2.6. --- Flammulina veltipes lectin --- p.29 / Chapter 2.2.2.7. --- Ischnoderma resinosum agglutinin --- p.31 / Chapter 2.2.2.8. --- Lectins from Agaricus spp --- p.31 / Chapter 2.2.3. --- Mushroom polysaccharides --- p.34 / Chapter 2.2.3.1. --- Lentinan --- p.35 / Chapter 2.2.3.2. --- "PSK (trade name, Krestin)" --- p.35 / Chapter 2.2.3.3. --- PSP (Polysaccharopeptide) --- p.37 / Chapter 2.2.3.4. --- PSPC (polysaccharide-peptide complex) --- p.38 / Chapter CHAPTER 3. --- Isolation and Characterization of Two Distinct Lectins from the Cultured Mycelium of the Edible Mushroom Tricholoma mongolicum --- p.44 / Chapter 3.1. --- Introduction --- p.44 / Chapter 3.2. --- Materials and Methods --- p.45 / Chapter 3.2.1. --- Strain and culture condition --- p.45 / Chapter 3.2.2. --- Extraction --- p.46 / Chapter 3.2.3. --- Purification --- p.46 / Chapter 3.2.4. --- Hemagglutination activity --- p.47 / Chapter 3.2.5. --- Test of hemagglutination inhibition by various carbohydrates --- p.47 / Chapter 3.2.6. --- MW estimation by gel filtration and SDS- PAGE --- p.48 / Chapter 3.2.7. --- Glycoprotein staining with PAS reagent --- p.49 / Chapter 3.2.8. --- Carbohydrate content --- p.49 / Chapter 3.2.9. --- Thermal stability --- p.49 / Chapter 3.2.10. --- pH stability --- p.49 / Chapter 3.2.11. --- Effect of cations --- p.50 / Chapter 3.2.12. --- Amino acid analysis --- p.50 / Chapter 3.2.13. --- Antiproliferative activity of lectins --- p.50 / Chapter 3.2.14. --- Statistics --- p.51 / Chapter 3.3. --- Results --- p.51 / Chapter 3.3.1. --- Extraction and purification --- p.51 / Chapter 3.3.2. --- General characteristics of lectins --- p.52 / Chapter 3.3.3. --- Antiproliferative activity of lectins --- p.54 / Chapter 3.4. --- Discussion --- p.55 / Chapter 3.5. --- Summary --- p.58 / Chapter CHAPTER 4. --- The Immunomodulatory and Antitumor Activities of Lectins from the Mushroom Tricholoma mongolicum --- p.79 / Chapter 4.1. --- Introduction --- p.79 / Chapter 4.2. --- Materials and Methods --- p.81 / Chapter 4.2.1. --- Lectins --- p.81 / Chapter 4.2.2. --- Animals --- p.81 / Chapter 4.2.3. --- Assay for antitumor activity --- p.81 / Chapter 4.2.4. --- Assessment of tumor growth and host survival after lectin treatment --- p.82 / Chapter 4.2.5. --- Mitogenic activity of lectins --- p.82 / Chapter 4.2.6. --- Production of nitrite ions in response to lectin treatment --- p.83 / Chapter 4.2.7. --- Preparation of concanavalin A-stimulated lymphokines --- p.84 / Chapter 4.2.8. --- Assay for macrophage activating factor --- p.85 / Chapter 4.2.9. --- Production of tumor necrosis factor (TNF) --- p.86 / Chapter 4.2.10. --- Bioassay for tumor necrosis factor --- p.86 / Chapter 4.2.11. --- Statistics --- p.87 / Chapter 4.3. --- Results --- p.87 / Chapter 4.3.1. --- Antitumor activity --- p.87 / Chapter 4.3.2. --- Assessment of tumor growth and host survival --- p.87 / Chapter 4.3.3. --- Mitogenic activity --- p.88 / Chapter 4.3.4. --- Production of nitrite ions --- p.89 / Chapter 4.3.5. --- Production of macrophage activating factor --- p.89 / Chapter 4.3.6. --- Tumor necrosis factor assay --- p.90 / Chapter 4.4. --- Discussion --- p.90 / Chapter 4.5. --- Summary --- p.94 / Chapter CHAPTER 5. --- Hypotensive and Vasorelaxing Activities of a Lectin (TML-1) from the Edible Mushroom Tricholoma mongolicum --- p.109 / Chapter 5.1. --- Introduction --- p.109 / Chapter 5.2. --- Materials and Methods --- p.111 / Chapter 5.2.1. --- Animals --- p.111 / Chapter 5.2.2. --- In vivo blood pressure measurement in rats --- p.112 / Chapter 5.2.3. --- Study employing blockade of autonomic ganglion transmission --- p.113 / Chapter 5.2.4. --- Study employing alpha-adrenergic blockade --- p.113 / Chapter 5.2.5. --- Study employing beta-adrenergic blockade --- p.114 / Chapter 5.2.6. --- Study employing cholinergic blockade --- p.114 / Chapter 5.2.7. --- Study employing histaminergic blockade --- p.114 / Chapter 5.2.8. --- Study employing inhibitor of the renin- angiotensin system --- p.115 / Chapter 5.2.9. --- Preparation of right atrium for in vitro studies --- p.115 / Chapter 5.2.10. --- Preparation of aorta for in vitro studies --- p.116 / Chapter 5.2.11. --- Adenosine receptor binding assays --- p.116 / Chapter 5.2.12. --- Effect of methylene blue on the hypotensive activity of TML-1 --- p.118 / Chapter 5.2.13. --- Statistics --- p.118 / Chapter 5.3. --- Results --- p.118 / Chapter 5.3.1. --- Blood pressure changes in vivo --- p.118 / Chapter 5.3.2. --- Pharmacological studies using receptor antagonists --- p.119 / Chapter 5.3.3. --- Adenosine receptor binding assay --- p.119 / Chapter 5.3.4. --- Effects on the right atrium in vitro --- p.120 / Chapter 5.3.5. --- Effect of TML-1 on vascular relaxation --- p.120 / Chapter 5.3.6. --- Effect of methylene blue on the hypotensive activity of TML-1 --- p.120 / Chapter 5.4. --- Discussion --- p.120 / Chapter 5.5. --- Summary --- p.123 / Chapter CHAPTER 6. --- A Polysaccharide-Peptide Complex with Immunoenhancing and Antitumor Activities from Cultured Mycelia of the Mushroom Tricholoma mongolicum --- p.134 / Chapter 6.1. --- Introduction --- p.134 / Chapter 6.2. --- Materials and Methods --- p.135 / Chapter 6.2.1. --- Extraction --- p.135 / Chapter 6.2.2. --- Purification --- p.135 / Chapter 6.2.3. --- PSP for purpose of comparison --- p.136 / Chapter 6.2.4. --- Polysaccharide and protein contents --- p.136 / Chapter 6.2.5. --- MW determination of F1 using gel filtration --- p.136 / Chapter 6.2.6. --- Animals --- p.136 / Chapter 6.2.7. --- Antiproliferative activity assay --- p.137 / Chapter 6.2.8. --- Mitogenic activity --- p.137 / Chapter 6.2.9. --- Production of nitrite ions --- p.138 / Chapter 6.2.10. --- Macrophage activating factor assay --- p.138 / Chapter 6.2.11. --- Antitumor activity assay --- p.139 / Chapter 6.2.12. --- Statistics --- p.139 / Chapter 6.3. --- Results --- p.140 / Chapter 6.3.1. --- Purification of polysaccharide-peptide complex --- p.140 / Chapter 6.3.2. --- Antiproliferative activity --- p.140 / Chapter 6.3.3. --- Mitogenic activity in vitro --- p.140 / Chapter 6.3.4. --- Molecular weight of Fl --- p.141 / Chapter 6.3.5. --- Mitogenic activity in vivo --- p.141 / Chapter 6.3.6. --- Production of nitrite ions --- p.141 / Chapter 6.3.7. --- Production of macrophage activating factor --- p.141 / Chapter 6.3.8. --- Antitumor activity in vivo --- p.142 / Chapter 6.4. --- Discussion --- p.142 / Chapter 6.5. --- Summary --- p.144 / GENERAL DISCUSSION --- p.155 / CONCLUSIONS --- p.158 / REFERENCES