A heterodimeric 60 kDa lectin was isolated from the ground bean ( Vigna sesquipedalis cv ground bean). Its hemagglutinating activity was inhibited by polygalacturonic acid and not by galacturonic acid and other simple monosaccharides. Ground bean lectin exhibited mitogenic activity on murine splenocytes, reduced the viability of hepatoma and leukemia cells, and exerted an inhibitory activity toward HIV-1 reverse transcriptase. / A homodimeric 30-kDa glucose/mannose-specific lectin was purified from emperor banana. In contrast to Con A, the mitogenic activity of emperor banana lectin (EBL) toward mouse splenocytes but not its NO stimulatory effect toward mouse macrophages could be abrogated by 200 mM glucose. It also inhibited proliferation of tumor cells and inhibited HIV-1 reverse transcriptase. / A homodimeric 60-kDa lectin with specificity toward mannose, glucose and rhamnose and substantial N-terminal sequence to Concanavalin A has been isolated from Canavalia gladiata legumes. In contrast to Con A, the mitogenic activity of knife bean lectin toward mouse splenocytes but not its antiproliferative activity toward tumor cells could be abrogated by 200 mM glucose. The lectin inhibited HIV-1 reverse transcriptase, but did not exhibit antifungal activity. / A homotetrameric 120-kDa agglutinin was isolated from haricot bean seeds. It manifested a weaker mitogenic activity than concanavalin A toward mouse splenocytes and exhibited antiproliferative activity toward several tumor cell lines. / A plant defensin-like peptide, with a molecular mass around 6-kDa, was purified from the seeds of Chinese lima beans (Phaseolus lunatus L. ). Phld exerted an antifungal activity and an antibacterial action. Phld could reduce the activity of HIV-1 reverse transcriptase and inhibit translation in a cell-free rabbit reticulocyte lysate system. (Abstract shortened by UMI.) / Defense proteins are produced by a wide range of organisms including mammals, insects, plants, fungi and bacteria. In this study, focus was placed on 2 kinds of defense proteins in plants, namely, lectins/hemagglutinins and defensin-like peptides/defensins. Three lectins, one hemagglutinin (i.e. lectin whose hemagglutinating activity cannot be inhibited by simple saccharides), one defensin and two defensin-like peptides were isolated from 5 species of plants. The isolation procedure included different chromatographic techniques, involving ion exchange chromatography, affinity chromatography and gel filtration. / Wong Ho. / "August 2005." / Adviser: Tzi Bun Ng. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3785. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. i-xxvii). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 133-154). Also available online.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2009. / Härtill 3 uppsatser.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 133-154). Also available in print.

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

No description available.

Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 108-130).

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Submitted by Programa de Pós-graduação em Biotecnologia (mebiotec.ufba@gmail.com) on 2017-04-04T13:24:02Z No. of bitstreams: 1 Dissertação Final- WILIAN OLIVEIRA.pdf: 1510952 bytes, checksum: 9058b21042c585177d09b07cc902395e (MD5) / Approved for entry into archive by Delba Rosa (delba@ufba.br) on 2017-07-06T12:57:28Z (GMT) No. of bitstreams: 1 Dissertação Final- WILIAN OLIVEIRA.pdf: 1510952 bytes, checksum: 9058b21042c585177d09b07cc902395e (MD5) / Made available in DSpace on 2017-07-06T12:57:28Z (GMT). No. of bitstreams: 1 Dissertação Final- WILIAN OLIVEIRA.pdf: 1510952 bytes, checksum: 9058b21042c585177d09b07cc902395e (MD5) / CAPES / Lectinas são proteínas que se ligam especificamente a resíduos de açúcar e estão envolvidas no processo de reconhecimento celular e sinalização em diversas vias metabólicas. O objetivo deste estudo foi isolar, purificar e investigar a atividade biológica das lectinas de Crotalaria spectabilis R. quanto a sua capacidade de hemaglutinação e aglutinação das linhagens bacterianas: Leptospira biflexa e L. interrogans. Para extração das proteínas, as sementes foram moídas e suas células lisadas em solução NaCl 0,15 M. Após essa etapa, as proteínas foram precipitadas com acetona e sulfato de amônio, dialisadas, liofilizadas e purificadas por cromatografia de filtração e troca iônica. A quantificação proteica foi realizada pelo método de Bradford e o perfil eletroforético obtido por SDS-PAGE. Para testar a atividade biológica das lectinas foram utilizados ensaios de hemaglutinação bem como de aglutinação das linhagens bacterianas. Em nossos resultados, o método de precipitação proteica por acetona resultou em maior extração quando comparado ao método por sulfato de amônio. A lectina de C. spectabilis R. apresentou um peso molecular de 30 kDa e os ensaios de hemaglutinação foram positivos para a proteína. Assim, concluimos que nas sementes de C. spectabilis R. existem lectinas com capacidade de reconhecer receptores presentes na membrana de eritrócitos humanos e promover aglutinação celular. Por fim, as lectinas da planta C. spectabilis R. também foram capazes de aglutinar L. interrogans e L. biflexa, sendo esta reposta mais acentuada na linhagem patogênica. / Lectins are proteins that bind carbohydrate residues with affinity and are involved in the process of cell recognition and signaling in different metabolic pathways. The aim of this study was to isolate, purify and investigate the biological activity of the Crotalaria spectabilis R. lectins in terms of hemagglutination and agglutination capacity of the bacterial strains: Leptospira biflexa and L. interrogans. For protein extraction, the seeds were milled and their cells lysed in 0,15 M NaCl solution. After this step, the proteins were precipitated with acetone and ammonium sulfate, dialyzed, lyophilized and purified by filtration chromatography and ion exchange, respectively. Protein quantification was performed by the Bradford method and the electrophoretic profile by SDS-PAGE. For testing the biological activities of lectins, hemagglutination assays were used as well agglutination of the bacterial strains. In our results, protein precipitation method by acetone resulted in higher yield when compared to ammonium sulfate. The C. spectabilis R. lectin presented a molecular weight of 30 kDa and the hemagglutination assays were positives for the protein. Thus, we conclude that in the C. spectabilis R. seeds there are lectins with capacity to recognize receptors present in the human erythrocytes membrane and to promote cell agglutination. At last, the seed lectin C. spectabilis R. was also able to agglutinate L. interrogans and L. biflexa, this response being stronger in the pathogenic strain.

by Luk Choi Wan. / Thesis submitted in: November 2005. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 125-132). / Abstracts in English and Chinese. / Abstract --- p.iv / 摘要 --- p.vi / Acknowledgements --- p.viii / Tabel of contents --- p.x / List of Figures --- p.xii / List of Tables --- p.xiv / List of Abbreviations --- p.xv / List of Abbreviations --- p.xv / Chapter Chapter One --- Literature review --- p.1 / Chapter 1.1 --- General introduction --- p.1 / Chapter 1.2 --- General aspects of plant lectins --- p.4 / Chapter 1.3 --- Monocot mannose-binding lectins --- p.5 / Chapter 1.3.1 --- General introduction --- p.5 / Chapter 1.3.2 --- Sugar specificity --- p.6 / Chapter 1.3.3 --- Isolation and purification --- p.7 / Chapter 1.3.4 --- Molecular cloning --- p.9 / Chapter 1.3.5 --- Molecular structure and modifications --- p.10 / Chapter 1.3.6 --- Molecular evolution --- p.12 / Chapter 1.3.7 --- Transformation --- p.12 / Chapter 1.3.8 --- Physiological roles --- p.14 / Chapter 1.3.9 --- Application --- p.19 / Chapter 1.4 --- Dendrobium nobile --- p.31 / Chapter 1.4.1 --- Background --- p.31 / Chapter 1.4.2 --- Chemical analysis --- p.32 / Chapter Chapter Two --- Biological activities of a mannose-binding lectin isolated from Dendrobium mobile --- p.33 / Chapter 2.1 --- Introduction --- p.33 / Chapter 2.2 --- Materials and methods --- p.35 / Chapter 2.2.1 --- Mannose-binding lectin from D. nobile --- p.35 / Chapter 2.3 --- Biological activities of mannose-binding lectin from D. nobile --- p.36 / Chapter 2.3.1 --- Hemagglutinating activity --- p.36 / Chapter 2.3.2 --- In vitro anti-proliferative assay --- p.37 / Chapter 2.3.3 --- In vitro antiviral assay --- p.40 / Chapter 2.3.4 --- Statistical Analysis --- p.42 / Chapter 2.4 --- Results --- p.43 / Chapter 2.4.1 --- Physiochemical properties of D. nobile lectins --- p.43 / Chapter 2.4.2 --- Cytotoxicity to cancer cell lines --- p.53 / Chapter 2.4.3 --- Antiviral activity --- p.59 / Chapter 2.5 --- Discussion --- p.60 / Chapter Chapter Three --- Molecular cloning of lectin gene of Dendrobium nobile --- p.65 / Chapter 3.1 --- Introduction --- p.65 / Chapter 3.2 --- Methods --- p.67 / Chapter 3.2.1 --- RNA extraction --- p.67 / Chapter 3.2.2 --- RT-PCR synthesis of D. nobile lectin cDNA --- p.68 / Chapter 3.2.3 --- RACE of D. nobile agglutinin gene --- p.69 / Chapter 3.2.4 --- Generation of DNL full-length lectin gene sequence --- p.70 / Chapter 3.2.5 --- Cloning and sequencing of PCR product --- p.71 / Chapter 3.2.6 --- Data analyses --- p.72 / Chapter 3.2.7 --- Synthesis of single-stranded DIG-labeled DNA probe --- p.74 / Chapter 3.2.8 --- Northern blot analysis --- p.74 / Chapter 3.2.9 --- Genomic DNA extraction --- p.75 / Chapter 3.2.10 --- Southern blot analysis --- p.76 / Chapter 3.2.11 --- Expression of DNL in E. coli --- p.76 / Chapter 3.2.12 --- Western blot analysis --- p.78 / Chapter 3.3 --- Results --- p.80 / Chapter 3.3.1 --- Isolation and characterization of DNL gene --- p.80 / Chapter 3.3.2 --- Sequence analysis of DNL --- p.89 / Chapter 3.2.3 --- Secondary and tertiary structure --- p.96 / Chapter 3.2.4 --- Southern blot analysis --- p.99 / Chapter 3.2.5 --- Northern blot analysis --- p.99 / Chapter 3.2.6 --- Expression of fusion protein in E.coli --- p.102 / Chapter 3.4 --- Discussion --- p.104 / Chapter Chapter Four --- General Discussion --- p.110 / Chapter 4.1 --- General discussion --- p.110 / Chapter 4.2 --- Isolation and Characterization of monocot mannose-binding lectin of D. nobile --- p.111 / Chapter 4.3 --- Molecular cloning of monocot mannose-binding lectin of D. nobile --- p.115 / Chapter 4.4 --- Further investigations --- p.122 / Chapter Chapter Five --- Conclusion --- p.124 / References: --- p.125 / Appendix --- p.133