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Tang X, Wang P, Shen Y, Song X, Benghezal M, Marshall BJ, Tang H, Li H. Lipopolysaccharide O-antigen profiles of Helicobacter pylori strains from Southwest China. BMC Microbiol 2023; 23:360. [PMID: 37993791 PMCID: PMC10664510 DOI: 10.1186/s12866-023-03116-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 11/08/2023] [Indexed: 11/24/2023] Open
Abstract
BACKGROUND Helicobacter pylori lipopolysaccharide (LPS) structures vary among strains of different geographic origin. The aim of this study was to characterize the LPS O-antigen profiles of H. pylori strains isolated from Southwest China, and to further analyze the association of Lewis antigen expression with clinical outcomes and antibiotic resistance. RESULTS A total of 71 H. pylori isolates from Southwest China were included for LPS profiling by silver staining and Western blotting after SDS-PAGE electrophoresis. We demonstrated that all the clinical isolates had the conserved lipid A and core-oligosaccharide, whereas the O-antigen domains varied significantly among the isolates. Compared with the common presence of the glucan/heptan moiety in LPS O-antigen structure of European strains, the clinical isolates in this study appeared to lack the glucan/heptan moiety. The expression frequency of Lex, Ley, Lea, and Leb was 66.2% (47/71), 84.5% (60/71), 56.3% (40/71), and 31.0% (22/71), respectively. In total, the expression of type II Lex and/or Ley was observed in 69 (97.2%) isolates, while type I Lea and/or Leb were expressed in 49 (69.0%) isolates. No association of Lewis antigen expression with clinical outcomes or with antibiotic resistance was observed. CONCLUSIONS H. pylori strains from Southwest China tend to produce heptan-deficient LPS and are more likely to express type I Lewis antigens as compared with Western strains. This may suggest that H. pylori evolves to change its LPS structure for adaptation to different hosts.
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Affiliation(s)
- Xiaoqiong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Peng Wang
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases &, Department of Orthognathic and TMJ Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Yalin Shen
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Xiaona Song
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Mohammed Benghezal
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Barry J Marshall
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Helicobacter Pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Hong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
| | - Hong Li
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
- Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
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2
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Moulton KD, Adewale AP, Carol HA, Mikami SA, Dube DH. Metabolic Glycan Labeling-Based Screen to Identify Bacterial Glycosylation Genes. ACS Infect Dis 2020; 6:3247-3259. [PMID: 33186014 PMCID: PMC7808405 DOI: 10.1021/acsinfecdis.0c00612] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bacterial cell surface glycans are quintessential drug targets due to their critical role in colonization of the host, pathogen survival, and immune evasion. The dense cell envelope glycocalyx contains distinctive monosaccharides that are stitched together into higher order glycans to yield exclusively bacterial structures that are critical for strain fitness and pathogenesis. However, the systematic study and inhibition of bacterial glycosylation enzymes remains challenging. Bacteria produce glycans containing rare sugars refractory to traditional glycan analysis, complicating the study of bacterial glycans and the identification of their biosynthesis machinery. To ease the study of bacterial glycans in the absence of detailed structural information, we used metabolic glycan labeling to detect changes in glycan biosynthesis. Here, we screened wild-type versus mutant strains of the gastric pathogen Helicobacter pylori, ultimately permitting the identification of genes involved in glycoprotein and lipopolysaccharide biosynthesis. Our findings provide the first evidence that H. pylori protein glycosylation proceeds via a lipid carrier-mediated pathway that overlaps with lipopolysaccharide biosynthesis. Protein glycosylation mutants displayed fitness defects consistent with those induced by small molecule glycosylation inhibitors. Broadly, our results suggest a facile approach to screen for bacterial glycosylation genes and gain insight into their biosynthesis and functional importance, even in the absence of glycan structural information.
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Affiliation(s)
- Karen D. Moulton
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Adedunmola P. Adewale
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Hallie A. Carol
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Sage A. Mikami
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Danielle H. Dube
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
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3
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Zhang X, Sheng W, Li K, Rong Y, Wu Q, Meng Q, Kong Y, Chen M. Substrate specificity of the galactokinase from the human gut symbiont Akkermansia muciniphila ATCC BAA-835. Enzyme Microb Technol 2020; 139:109568. [PMID: 32732027 DOI: 10.1016/j.enzmictec.2020.109568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/02/2020] [Accepted: 04/03/2020] [Indexed: 11/16/2022]
Abstract
Galactokinases, which catalyze the phosphorylation of galactose and possible other monosaccharides, can provide an activated sugar donor to synthesize sugar-containing molecules. In this study, a novel galactokinase from human gut symbiont Akkermansia muciniphila ATCC BAA-835 (GalKAmu) was expressed and characterized. GalKAmu displayed broad substrate tolerance, with catalytic activity towards Gal (100 %), GalN (100 %), GalA (20.2 %), Glc (52.5 %), GlcNAc (15.5 %), Xyl (<5%), ManNAc (58 %), ManF (37.4 %) and l-Glc (80 %). Most interestingly, this was the first GalK isoform which can tolerate ManNAc. Thus, our characterization of GalKAmu broadens the substrate selection of galactokinases.
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Affiliation(s)
- Xunlian Zhang
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China
| | - Weihao Sheng
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China
| | - Kun Li
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China
| | - Yongheng Rong
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China
| | - Qizheng Wu
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China
| | - Qingyun Meng
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China
| | - Yun Kong
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China.
| | - Min Chen
- The State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Qingdao, Shandong, 266237, China.
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4
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Li H, Marceau M, Yang T, Liao T, Tang X, Hu R, Xie Y, Tang H, Tay A, Shi Y, Shen Y, Yang T, Pi X, Lamichhane B, Luo Y, Debowski AW, Nilsson HO, Haslam SM, Mulloy B, Dell A, Stubbs KA, Marshall BJ, Benghezal M. East-Asian Helicobacter pylori strains synthesize heptan-deficient lipopolysaccharide. PLoS Genet 2019; 15:e1008497. [PMID: 31747390 PMCID: PMC6892558 DOI: 10.1371/journal.pgen.1008497] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 12/04/2019] [Accepted: 10/28/2019] [Indexed: 02/05/2023] Open
Abstract
The lipopolysaccharide O-antigen structure expressed by the European Helicobacter pylori model strain G27 encompasses a trisaccharide, an intervening glucan-heptan and distal Lewis antigens that promote immune escape. However, several gaps still remain in the corresponding biosynthetic pathway. Here, systematic mutagenesis of glycosyltransferase genes in G27 combined with lipopolysaccharide structural analysis, uncovered HP0102 as the trisaccharide fucosyltransferase, HP1283 as the heptan transferase, and HP1578 as the GlcNAc transferase that initiates the synthesis of Lewis antigens onto the heptan motif. Comparative genomic analysis of G27 lipopolysaccharide biosynthetic genes in strains of different ethnic origin revealed that East-Asian strains lack the HP1283/HP1578 genes but contain an additional copy of HP1105 and JHP0562. Further correlation of different lipopolysaccharide structures with corresponding gene contents led us to propose that the second copy of HP1105 and the JHP0562 may function as the GlcNAc and Gal transferase, respectively, to initiate synthesis of the Lewis antigen onto the Glc-Trio-Core in East-Asian strains lacking the HP1283/HP1578 genes. In view of the high gastric cancer rate in East Asia, the absence of the HP1283/HP1578 genes in East-Asian H. pylori strains warrants future studies addressing the role of the lipopolysaccharide heptan in pathogenesis.
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Affiliation(s)
- Hong Li
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Michael Marceau
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 8204—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Tiandi Yang
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Tingting Liao
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Xiaoqiong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Renwei Hu
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, China
| | - Yan Xie
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, China
| | - Hong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Alfred Tay
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Ying Shi
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yalin Shen
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Tiankuo Yang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Xuenan Pi
- Precision Medicine Key Laboratory of Sichuan Province & Precision Medicine Center, West China Hospital, Sichuan University, Chengdu, China
| | - Binit Lamichhane
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Yong Luo
- Key Laboratory of Geoscience Spatial Information Technology, Ministry of Land and Resources of the P.R.China, Chengdu University of Technology
| | - Aleksandra W. Debowski
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
- School of Molecular Sciences, University of Western Australia, Crawley, Australia
| | - Hans-Olof Nilsson
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Stuart M. Haslam
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Barbara Mulloy
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Anne Dell
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Keith A. Stubbs
- School of Molecular Sciences, University of Western Australia, Crawley, Australia
| | - Barry J. Marshall
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
- Ondek Pty Ltd, Rushcutters Bay, New South Wales, Australia
| | - Mohammed Benghezal
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
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5
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Pathogen Colonization Resistance in the Gut and Its Manipulation for Improved Health. THE AMERICAN JOURNAL OF PATHOLOGY 2019; 189:1300-1310. [PMID: 31100210 DOI: 10.1016/j.ajpath.2019.03.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/15/2019] [Accepted: 03/05/2019] [Indexed: 02/07/2023]
Abstract
Mammals have coevolved with a large community of symbiotic, commensal, and some potentially pathogenic microbes. The trillions of bacteria and hundreds of species in our guts form a relatively stable community that resists invasion by outsiders, including pathogens. This powerful protective force is referred to as colonization resistance. We discuss the variety of proposed or demonstrated mechanisms that can mediate colonization resistance and some potential ways to manipulate them for improved human health. Instances in which certain bacterial pathogens can overcome colonization resistance are also discussed.
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6
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Host Determinants of Expression of the Helicobacter pylori BabA Adhesin. Sci Rep 2017; 7:46499. [PMID: 28418004 PMCID: PMC5394467 DOI: 10.1038/srep46499] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 03/17/2017] [Indexed: 12/19/2022] Open
Abstract
Expression of the Helicobacter pylori blood group antigen binding adhesin A (BabA) is more common in strains isolated from patients with peptic ulcer disease or gastric cancer, rather than asymptomatic colonization. Here we used mouse models to examine host determinants that affect H. pylori BabA expression. BabA expression was lost by phase variation as frequently in WT mice as in RAG2−/− mice that do not have functional B or T cells, and in MyD88−/−, TLR2−/− and TLR4−/− mice that are defective in toll like receptor signaling. The presence of other bacteria had no effect on BabA expression as shown by infection of germ free mice. Moreover, loss of BabA expression was not dependent on Leb expression or the capacity of BabA to bind Leb. Surprisingly, gender was the host determinant most associated with loss of BabA expression, which was maintained to a greater extent in male mice and was associated with greater bacterial load. These results suggest the possibility that loss of BabA expression is not driven by adaptive immunity or toll-like receptor signaling, and that BabA may have other, unrecognized functions in addition to serving as an adhesin that binds Leb.
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7
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Bagheri N, Azadegan-Dehkordi F, Rafieian-Kopaei M, Rahimian G, Asadi-Samani M, Shirzad H. Clinical relevance of Helicobacter pylori virulence factors in Iranian patients with gastrointestinal diseases. Microb Pathog 2016; 100:154-162. [PMID: 27666510 DOI: 10.1016/j.micpath.2016.09.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 09/21/2016] [Accepted: 09/21/2016] [Indexed: 12/21/2022]
Abstract
Helicobacter pylori (H. pylori) usually colonizes the gastric mucosa of more than 50% of the human population, causing an infection that may appear in early childhood and can persist for life. H. pylori is suggested as the main cause of peptic ulcer and chronic gastritis. It is also associated with gastric cancer. Its severity and symptoms depend on environmental factors, host susceptibility and bacterial components, which allow H. pylori to switch between commensalism and pathogenicity. H. pylori is genetically highly variable, and the variability which affects H. pylori virulence factors might be useful in identifying the strains with different degrees of pathogenicity. The geographic distribution of distinct H. pylori genotypes is largely unknown and should be established. The prevalence of more pathogenic genotypes in certain areas may have important epidemiological consequences. It also might be associated with the severity of H. pylori related diseases in such regions. Given that Iran is located in the Middle East and Asian populations have revealed high levels of gastric cancer, it is of clinical interest to clarify the potential of H. pylori virulence markers in predicting the associated clinical outcomes. In this review, clinical relevance of adhesion molecules and significant virulence factors of H. pylori in Iranian patients with gastrointestinal diseases are discussed in comparison to other countries.
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Affiliation(s)
- Nader Bagheri
- Cellular and Molecular Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran; Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | | | | | - Ghorbanali Rahimian
- Department of Internal Medicine, Shahrekord University of Medical Sciences, Shahrekord, Iran
| | - Majid Asadi-Samani
- Medical Plants Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran
| | - Hedaytollah Shirzad
- Cellular and Molecular Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran.
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8
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Maldonado RF, Sá-Correia I, Valvano MA. Lipopolysaccharide modification in Gram-negative bacteria during chronic infection. FEMS Microbiol Rev 2016; 40:480-93. [PMID: 27075488 PMCID: PMC4931227 DOI: 10.1093/femsre/fuw007] [Citation(s) in RCA: 372] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 08/23/2015] [Accepted: 03/10/2016] [Indexed: 12/16/2022] Open
Abstract
The Gram-negative bacterial lipopolysaccharide (LPS) is a major component of the outer membrane that plays a key role in host-pathogen interactions with the innate immune system. During infection, bacteria are exposed to a host environment that is typically dominated by inflammatory cells and soluble factors, including antibiotics, which provide cues about regulation of gene expression. Bacterial adaptive changes including modulation of LPS synthesis and structure are a conserved theme in infections, irrespective of the type or bacteria or the site of infection. In general, these changes result in immune system evasion, persisting inflammation and increased antimicrobial resistance. Here, we review the modifications of LPS structure and biosynthetic pathways that occur upon adaptation of model opportunistic pathogens (Pseudomonas aeruginosa, Burkholderia cepacia complex bacteria, Helicobacter pylori and Salmonella enterica) to chronic infection in respiratory and gastrointestinal sites. We also discuss the molecular mechanisms of these variations and their role in the host-pathogen interaction.
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Affiliation(s)
- Rita F. Maldonado
- Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon 1049-001, Portugal
| | - Isabel Sá-Correia
- Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon 1049-001, Portugal
| | - Miguel A. Valvano
- Department of Microbiology and Immunology, University of Western Ontario, London, ON N6A 5C1, Canada
- Centre for Infection and Immunity, Queen's University Belfast, Belfast BT9 7BL, UK
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9
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Tytgat HLP, de Vos WM. Sugar Coating the Envelope: Glycoconjugates for Microbe-Host Crosstalk. Trends Microbiol 2016; 24:853-861. [PMID: 27374775 DOI: 10.1016/j.tim.2016.06.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 05/31/2016] [Accepted: 06/09/2016] [Indexed: 12/14/2022]
Abstract
Tremendous progress has been made on mapping the mainly bacterial members of the human intestinal microbiota. Knowledge on what is out there, or rather what is inside, needs to be complemented with insight on how these bacteria interact with their biotic environment. Bacterial glycoconjugates, that is, the collection of all glycan-modified molecules, are ideal modulators of such interactions. Their enormous versatility and diversity results in a species-specific glycan barcode, providing a range of ligands for host interaction. Recent reports on the functional importance of glycosylation of important bacterial ligands in beneficial and pathogenic species underpin this. Glycoconjugates, and glycoproteins in particular, are an underappreciated, potentially crucial, factor in understanding bacteria-host interactions of old friends and foes.
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Affiliation(s)
- Hanne L P Tytgat
- Laboratory of Microbiology, Wageningen University, 6708 WE Wageningen, The Netherlands; Institute of Microbiology, Swiss Federal Institute of Technology, ETH Zurich, 8093 Zurich, Switzerland
| | - Willem M de Vos
- Laboratory of Microbiology, Wageningen University, 6708 WE Wageningen, The Netherlands; Faculty of Medicine, Immunobiology Research Program, Department of Bacteriology and Immunology, University of Helsinki, 00290 Helsinki, Finland.
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10
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Pickard JM, Chervonsky AV. Intestinal fucose as a mediator of host-microbe symbiosis. THE JOURNAL OF IMMUNOLOGY 2015; 194:5588-93. [PMID: 26048966 DOI: 10.4049/jimmunol.1500395] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Fucose is an L-configuration sugar found abundantly in the mammalian gut. It has long been known to be induced there by the presence of bacteria, but only recently have some of the molecular mechanisms behind this process been uncovered. New work suggests that fucose can have a protective role in both gut-centered and systemic infection and inflammation. This review highlights recent studies showing that, in addition to acting as a food source for beneficial gut symbionts, host fucose can suppress the virulence of pathogens and pathobionts. The relevance of gut fucosylation to human diseases also is discussed.
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Affiliation(s)
- Joseph M Pickard
- Department of Pathology and Committee on Immunology, The University of Chicago, Chicago, IL 60637
| | - Alexander V Chervonsky
- Department of Pathology and Committee on Immunology, The University of Chicago, Chicago, IL 60637
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11
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The Prevalence of Helicobacter pylori Virulence Factors in Bhutan, Vietnam, and Myanmar Is Related to Gastric Cancer Incidence. BIOMED RESEARCH INTERNATIONAL 2015; 2015:830813. [PMID: 26090448 PMCID: PMC4450262 DOI: 10.1155/2015/830813] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/26/2015] [Accepted: 01/31/2015] [Indexed: 12/24/2022]
Abstract
Gastric cancer is a significant health problem in Asia. Although the prevalence of Helicobacter pylori infection is similar in Bhutan, Vietnam, and Myanmar, the incidence of gastric cancer is highest in Bhutan, followed by Vietnam and Myanmar. We hypothesized that H. pylori virulence factors contribute to the differences. The status of cagA, vacA, jhp0562, and β-(1,3)galT(jhp0563) was examined in 371 H. pylori-infected patients from Bhutan, Vietnam, and Myanmar. Each virulence factor could not explain the difference of the incidence of gastric cancer. However, the prevalence of quadruple-positive for cagA, vacA s1, vacA m1, and jhp0562-positive/β-(1,3)galT-negative was significantly higher in Bhutan than in Vietnam and Myanmar and correlated with gastric cancer incidence. Moreover, gastritis-staging scores measured by histology of gastric mucosa were significantly higher in quadruple-positive strains. We suggest that the cagA, vacA s1, vacA m1, and jhp0562-positive/β-(1,3)galT-negative genotype may play a role in the development of gastric cancer.
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12
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Rhee KH, Park JS, Cho MJ. Helicobacter pylori: bacterial strategy for incipient stage and persistent colonization in human gastric niches. Yonsei Med J 2014; 55:1453-66. [PMID: 25323880 PMCID: PMC4205683 DOI: 10.3349/ymj.2014.55.6.1453] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Helicobacter pylori (H. pylori) undergoes decades long colonization of the gastric mucosa of half the population in the world to produce acute and chronic gastritis at the beginning of infection, progressing to more severe disorders, including peptic ulcer disease and gastric cancer. Prolonged carriage of H. pylori is the most crucial factor for the pathogenesis of gastric maladies. Bacterial persistence in the gastric mucosa depends on bacterial factors as well as host factors. Herein, the host and bacterial components responsible for the incipient stages of H. pylori infection are reviewed and discussed. Bacterial adhesion and adaptation is presented to explain the persistence of H. pylori colonization in the gastric mucosa, in which bacterial evasion of host defense systems and genomic diversity are included.
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Affiliation(s)
- Kwang-Ho Rhee
- Department of Microbiology, Gyeongsang National University College of Medicine, Research Institute of Life Science, Gyeongsang National University, Jinju, Korea
| | - Jin-Sik Park
- Department of Microbiology, Gyeongsang National University College of Medicine, Research Institute of Life Science, Gyeongsang National University, Jinju, Korea
| | - Myung-Je Cho
- Department of Microbiology, Gyeongsang National University College of Medicine, Research Institute of Life Science, Gyeongsang National University, Jinju, Korea.
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13
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Rubin EJ, Trent MS. Colonize, evade, flourish: how glyco-conjugates promote virulence of Helicobacter pylori. Gut Microbes 2013; 4:439-53. [PMID: 23859890 PMCID: PMC3928157 DOI: 10.4161/gmic.25721] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Helicobacter pylori is an adapted gastric pathogen that colonizes the human stomach, causing severe gastritis and gastric cancer. A hallmark of infection is the ability of this organism to evade detection by the human immune system. H. pylori has evolved a number of features to achieve this, many of which involve glyco-conjugates including the lipopolysaccharide, peptidoglycan layer, glycoproteins, and glucosylated cholesterol. These major bacterial components possess unique features from those of other gram-negative organisms, including differences in structure, assembly, and modification. These defining characteristics of H. pylori glycobiology help the pathogen establish a long-lived infection by providing camouflage, modulating the host immune response, and promoting virulence mechanisms. In this way, glyco-conjugates are essential for H. pylori pathogenicity and survival, allowing it to carve out a niche in the formidable environment of the human stomach.
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Affiliation(s)
- Erica J Rubin
- Institute for Cellular and Molecular Biology; The University of Texas at Austin; Austin, TX USA
| | - M Stephen Trent
- Institute for Cellular and Molecular Biology; The University of Texas at Austin; Austin, TX USA,Department of Molecular Biosciences; The University of Texas at Austin; Austin, TX USA,Correspondence to: M Stephen Trent,
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Altman E, Chandan V, Harrison BA, Panayotopoulou EG, Roma-Giannikou E, Li J, Sgouras DN. Helicobacter pylori isolates from Greek children express type 2 and type 1 Lewis and α1,6-glucan antigens in conjunction with a functional type IV secretion system. J Med Microbiol 2012; 61:559-566. [DOI: 10.1099/jmm.0.038729-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Eleonora Altman
- Institute for Biological Sciences, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
| | - Vandana Chandan
- Institute for Biological Sciences, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
| | - Blair A. Harrison
- Institute for Biological Sciences, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
| | | | | | - Jianjun Li
- Institute for Biological Sciences, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
| | - Dionyssios N. Sgouras
- Laboratory of Medical Microbiology, Hellenic Pasteur Institute, Athens 11521, Greece
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15
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Novel functions for glycosyltransferases Jhp0562 and GalT in Lewis antigen synthesis and variation in Helicobacter pylori. Infect Immun 2012; 80:1593-605. [PMID: 22290141 DOI: 10.1128/iai.00032-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Lewis (Le) antigens are fucosylated oligosaccharides present in the Helicobacter pylori lipopolysaccharide. Expression of these antigens is believed to be important for H. pylori colonization, since Le antigens also are expressed on the gastric epithelia in humans. A galactosyltransferase encoded by β-(1,3)galT is essential for production of type 1 (Le(a) and Le(b)) antigens. The upstream gene jhp0562, which is present in many but not all H. pylori strains, is homologous to β-(1,3)galT but is of unknown function. Because H. pylori demonstrates extensive intragenomic recombination, we hypothesized that these two genes could undergo DNA rearrangement. A PCR screen and subsequent sequence analyses revealed that the two genes can recombine at both the 5' and 3' ends. Chimeric β-(1,3)galT-like alleles can restore function in a β-(1,3)galT null mutant, but neither native nor recombinant jhp0562 can. Mutagenesis of jhp0562 revealed that it is essential for synthesis of both type 1 and type 2 Le antigens. Transcriptional analyses of both loci showed β-(1,3)galT expression in all wild-type (WT) and mutant strains tested, whereas jhp0562 was not expressed in jhp0562 null mutants, as expected. Since jhp0562 unexpectedly displayed functions in both type 1 and type 2 Le synthesis, we asked whether galT, part of the type 2 synthesis pathway, had analogous functions in type 1 synthesis. Mutagenesis and complementation analysis confirmed that galT is essential for Le(b) production. In total, these results demonstrate that galT and jhp0562 have functions that cross the expected Le synthesis pathways and that jhp0562 provides a substrate for intragenomic recombination to generate diverse Le synthesis enzymes.
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16
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Pohl MA, Zhang W, Shah SN, Sanabria-Valentín EL, Perez-Perez GI, Blaser MJ. Genotypic and phenotypic variation of Lewis antigen expression in geographically diverse Helicobacter pylori isolates. Helicobacter 2011; 16:475-81. [PMID: 22059399 PMCID: PMC3228314 DOI: 10.1111/j.1523-5378.2011.00897.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND Helicobacter pylori are a persistent colonizer of the human gastric mucosa, which can lead to the development of peptic ulcer disease and gastric adenocarcinomas. However, H. pylori can asymptomatically colonize a host for years. One factor that has been hypothesized to contribute to such persistence is the production of Lewis (Le) antigens in the lipopolysaccharide layer of the bacterial outer membrane as a form of molecular mimicry, because humans also express these antigens on their gastric mucosa. Humans and H. pylori both are polymorphic for Le expression, which is driven in H. pylori by variation at the Le synthesis loci. In this report, we sought to characterize Le genotypic and phenotypic variation in geographically diverse H. pylori isolates. MATERIALS AND METHODS From patients undergoing endoscopy in 29 countries, we determined Le phenotypes of 78 H. pylori strains and performed genotyping of the galT and β-(1,3)galT loci in 113 H. pylori strains. RESULTS Le antigen phenotyping revealed a significant (p < .0001) association between type 1 (Le(a) and Le(b) ) expression and strains of East Asian origin. Genotyping revealed a significant correlation between strain origin and the size of the promoter region upstream of the Le synthesis gene, galT (p < .0001). CONCLUSION These results indicate that the heterogeneity of human Le phenotypes is reflected in their H. pylori colonizing strains and suggest new loci that can be studied to assess the variation of Le expression.
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Affiliation(s)
- Mary Ann Pohl
- Department of Medicine, New York University School of Medicine, New York, NY, USA.
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17
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Matsuda M, Shiota S, Matsunari O, Watada M, Murakami K, Fujioka T, Yamaoka Y. Prevalence of two homologous genes encoding glycosyltransferases of Helicobacter pylori in the United States and Japan. J Gastroenterol Hepatol 2011; 26:1451-6. [PMID: 21592227 PMCID: PMC3166395 DOI: 10.1111/j.1440-1746.2011.06779.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND AND AIM jhp0562 and β-(1,3)galT (jhp0563) of Helicobacter pylori have been suggested as novel virulent factors; however, the clinical associations and functions of these genes remain unclear. We examined the prevalence of jhp0562, β-(1,3)galT, and cagA in the United States (US) and Japanese populations. METHODS A total of 308 strains (171 from the US and 137 from Japan) were examined for the status of jhp0562, β-(1,3)galT, and cagA by polymerase chain reaction. RESULTS There were significant differences in the status of jhp0562, β-(1,3)galT and cagA between the US and Japanese populations (P < 0.001). In the US, the prevalence of β-(1,3)galT was significantly lower in strains isolated from patients with duodenal ulcer (DU) or gastric ulcer (GU) than those with gastritis (47.8% and 32.1% vs 72.0%, P < 0.01), and the absence of β-(1,3)galT was an independent factor discriminating DU and GU from gastritis (adjusted odds ratios, 4.21 and 8.52; 95% confidence intervals, 1.75 to 10.12 and 2.76 to 26.33, respectively). In the US, the prevalence of the jhp0562-positive/β-(1,3)galT-negative genotype was significantly higher in strains from DU and GU patients than in those from gastritis patients (50.0%, 67.9%, and 24.4%, P < 0.01) and the cagA status was significantly correlated with that of jhp0562 and inversely correlated with that of β-(1,3)galT. In contrast, the prevalence of these three genes was not significantly different in Japan. CONCLUSIONS jhp0562 or β-(1,3)galT can be used to discriminate peptic ulcers from gastritis in the US, but not in Japan.
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Affiliation(s)
- Miyuki Matsuda
- Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan
| | - Seiji Shiota
- Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan,Department of General Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan
| | - Osamu Matsunari
- Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan,Department of General Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan
| | - Masahide Watada
- Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan,Department of General Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan
| | - Kazunari Murakami
- Department of General Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan
| | - Toshio Fujioka
- Department of General Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan
| | - Yoshio Yamaoka
- Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama-machi, Yufu-City, Oita 879-5593, Japan,Department of Medicine-Gastroenterology, Baylor College of Medicine and Michael E. DeBakey Veterans Affairs Medical Center, 2002 Holcombe Blvd. Houston, Texas 77030, United States
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18
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Abstract
The immune response to Helicobacter pylori entails both innate effectors and a complex mix of Th1, Th17, and Treg adaptive immune responses. The clinical outcome of infection may well depend to a large degree on the relative balance of these responses. Vaccination with a wide range of antigens, adjuvants, and delivery routes can produce statistically significant reductions in H. pylori colonization levels in mice, though rarely sterilizing immunity. Whether similar reductions in bacterial load can be achieved in humans, and whether they would be clinically significant, is still unclear. However, progress in understanding the role of Th1, Th17, and most recently Treg cells in protection against H. pylori infection provides reason for optimism.
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Affiliation(s)
- Anne Müller
- Institute of Molecular Cancer Research, University of Zürich, Winterthurerstr 190, 8057 Zurich, Switzerland.
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19
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Helicobacter pylori and gastric cancer: factors that modulate disease risk. Clin Microbiol Rev 2010; 23:713-39. [PMID: 20930071 DOI: 10.1128/cmr.00011-10] [Citation(s) in RCA: 916] [Impact Index Per Article: 65.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Helicobacter pylori is a gastric pathogen that colonizes approximately 50% of the world's population. Infection with H. pylori causes chronic inflammation and significantly increases the risk of developing duodenal and gastric ulcer disease and gastric cancer. Infection with H. pylori is the strongest known risk factor for gastric cancer, which is the second leading cause of cancer-related deaths worldwide. Once H. pylori colonizes the gastric environment, it persists for the lifetime of the host, suggesting that the host immune response is ineffective in clearing this bacterium. In this review, we discuss the host immune response and examine other host factors that increase the pathogenic potential of this bacterium, including host polymorphisms, alterations to the apical-junctional complex, and the effects of environmental factors. In addition to host effects and responses, H. pylori strains are genetically diverse. We discuss the main virulence determinants in H. pylori strains and the correlation between these and the diverse clinical outcomes following H. pylori infection. Since H. pylori inhibits the gastric epithelium of half of the world, it is crucial that we continue to gain understanding of host and microbial factors that increase the risk of developing more severe clinical outcomes.
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20
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Abstract
Helicobacter pylori infections are thought to eventually lead to symptoms as a result of the long-lasting interactions between the bacterium and its host. Mechanisms that allow this bacterium to cause a life-long infection involve modulation of both the immune response and host cellular processes. Last year many novel findings that improve our knowledge on how H. pylori virulence factors interact with the host were reported, but because of space limitations we can only discuss a limited number of these studies. Among those are studies on the genetic variation of genes encoding outer membrane proteins and the mimicry of host antigens, factors that alter host-cell metabolism and factors that modulate the host's immune response.
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Affiliation(s)
- Daniela Basso
- Department of Laboratory Medicine, University-Hospital of Padova, Via Giustiniani 2, Padua, Italy.
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21
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Clinical relevance and diversity of two homologous genes encoding glycosyltransferases in Helicobacter pylori. J Clin Microbiol 2010; 48:2885-91. [PMID: 20554820 DOI: 10.1128/jcm.00401-10] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Helicobacter pylori is known to be a major cause of peptic ulceration. The jhp0562 gene, encoding a glycosyltransferase involved in the synthesis of the lipopolysaccharide, was associated with peptic ulcer disease (PUD) in children. The beta-(1,3)-galactosyltransferase [beta-(1,3)GalT] gene (jhp0563), involved in Lewis (Le) antigen expression, is highly similar to jhp0562. The clinical significance and diversity of both genes were examined by PCR and sequencing of clinical strains (n = 117) isolated from children with PUD (n = 57) and nonulcer dyspepsia (NUD; n = 60). The prevalence of the jhp0562 gene was significantly higher in strains with a more-virulent profile (strains positive for the cag pathogenicity island [PAI], vacA sl allele, babA, homB, phase-variable gene oipA "on" [i.e., functional], and hopQ I allele). The distribution of genotypes according to clinical outcome showed that the presence of jhp0562 represented one of the greatest risks for the development of PUD. Moreover, the triple-positive genotype for the cag PAI, jhp0562, and homB provided the best discriminatory model for distinguishing PUD and NUD outcomes in children. Sequence and in vitro expression analyses of jhp0562 showed the presence of a complete open reading frame, while the beta-(1,3)GalT gene was shown to be a phase-variable gene. The regular presence of jhp0562 in strains with a truncated beta-(1,3)GalT gene suggests that jhp0562 may also be implicated in the regulation of Le antigen expression. Overall, the results of this study suggest that the jhp0562 gene is of great clinical relevance, being a useful comarker for severe H. pylori-related disease and contributing to host adaptation.
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22
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Abstract
Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.
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23
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Abstract
Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.
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Affiliation(s)
- D Brent Polk
- Department of Pediatrics, University of Southern California, Los Angeles, CA 10027, USA
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24
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Abstract
Microbial pathogens contribute to the development of more than 1 million cases of cancer per year. Gastric adenocarcinoma is the second leading cause of cancer-related death in the world, and gastritis induced by Helicobacter pylori is the strongest known risk factor for this malignancy. H. pylori colonizes the stomach for years, not days or weeks, as is usually the case for bacterial pathogens and it always induces inflammation; however, only a fraction of colonized individuals ever develop disease. Identification of mechanisms through which H. pylori co-opts host defenses to facilitate its own persistence will not only improve diagnostic and therapeutic modalities, but may also provide insights into other diseases that arise within the context of long-term pathogen-initiated inflammatory states, such as chronic viral hepatitis and hepatocellular carcinoma.
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Affiliation(s)
- Dawn A Israel
- Department of Medicine; Division of Gastroenterology; Vanderbilt University Medical Center; Nashville, TN USA
| | - Richard M Peek
- Department of Medicine; Division of Gastroenterology; Vanderbilt University Medical Center; Nashville, TN USA,Department of Cancer Biology; Vanderbilt University Medical Center; Nashville, TN USA,Department of Veterans Affairs Medical Center; Nashville, TN USA
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25
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Peterson DA, Jimenez Cardona RA. Specificity of the Adaptive Immune Response to the Gut Microbiota. Adv Immunol 2010; 107:71-107. [DOI: 10.1016/b978-0-12-381300-8.00003-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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