title: Colony morphology variation of Burkholderia pseudomallei is associated with antigenic variation and O-polysaccharide modification.
abstract: Burkholderia pseudomallei is a CDC tier 1 select agent that causes melioidosis, a severe disease in humans and animals. Persistent infections are common, and there is currently no vaccine available. Lipopolysaccharide (LPS) is a potential vaccine candidate. B. pseudomallei expresses three serologically distinct LPS types. The predominant O-polysaccharide (OPS) is an unbranched heteropolymer with repeating d-glucose and 6-deoxy-l-talose residues in which the 6-deoxy-l-talose residues are variably replaced with O-acetyl and O-methyl modifications. We observed that primary clinical B. pseudomallei isolates with mucoid and nonmucoid colony morphologies from the same sample expressed different antigenic types distinguishable using an LPS-specific monoclonal antibody (MAb). MAb-reactive (nonmucoid) and nonreactive (mucoid) strains from the same patient exhibited identical LPS banding patterns by silver staining and indistinguishable genotypes. We hypothesized that LPS antigenic variation reflected modification of the OPS moieties. Mutagenesis of three genes involved in LPS synthesis was performed in B. pseudomallei K96243. Loss of MAb reactivity was observed in both wbiA (encoding a 2-O-acetyltransferase) and wbiD (putative methyl transferase) mutants. The structural characteristics of the OPS moieties from isogenic nonmucoid strain 4095a and mucoid strain 4095c were further investigated. Utilizing nuclear magnetic resonance (NMR) spectroscopy, we found that B. pseudomallei 4095a and 4095c OPS antigens exhibited substitution patterns that differed from the prototypic OPS structure. Specifically, 4095a lacked 4-O-acetylation, while 4095c lacked both 4-O-acetylation and 2-O-methylation. Our studies indicate that B. pseudomallei OPS undergoes antigenic variation and suggest that the 9D5 MAb recognizes a conformational epitope that is influenced by both O-acetyl and O-methyl substitution patterns.
authors.affiliation: Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Chanthiwa
authors.initials: C
authors.lastname: Wikraiphat
authors.affiliation: Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Natnaree
authors.initials: N
authors.lastname: Saiprom
authors.affiliation: Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Sarunporn
authors.initials: S
authors.lastname: Tandhavanant
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Heiss
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA.
authors.forename: Parastoo
authors.initials: P
authors.lastname: Azadi
authors.affiliation: Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Gumphol
authors.initials: G
authors.lastname: Wongsuvan
authors.affiliation: Department of Tropical Medicine, Medical Microbiology and Pharmacology, University of Hawaii, Honolulu, Hawaii, USA.
authors.forename: Apichai
authors.initials: A
authors.lastname: Tuanyok
authors.affiliation: Pathogen Genomics, The Wellcome Trust Sanger Institute, Cambridge, United Kingdom.
authors.forename: Matthew T G
authors.initials: MT
authors.lastname: Holden
authors.affiliation: Department of Microbiology and Immunology, University of South Alabama, Mobile, Alabama, USA.
authors.forename: Mary N
authors.initials: MN
authors.lastname: Burtnick
authors.affiliation: Department of Microbiology and Immunology, University of South Alabama, Mobile, Alabama, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Brett
authors.affiliation: Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Peacock
authors.affiliation: Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand narisara@tropmedres.ac.
authors.forename: Narisara
authors.initials: N
authors.lastname: Chantratita
mesh_terms: D000907:Antibodies, Bacterial / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D000940:Antigenic Variation; D016957:Burkholderia pseudomallei / Q000737:chemistry / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008554:Melioidosis / Q000382:microbiology; D019081:O Antigens / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D019081:O Antigens