title: Immunoproteomic Analysis of Antibody Responses to Extracellular Proteins of Candida albicans Revealing the Importance of Glycosylation for Antigen Recognition.
abstract: During infection, the human pathogenic fungus Candida albicans undergoes a yeast-to-hypha transition, secretes numerous proteins for invasion of host tissues, and modulates the host's immune response. Little is known about the interplay of C. albicans secreted proteins and the host adaptive immune system. Here, we applied a combined 2D gel- and LC-MS/MS-based approach for the characterization of C. albicans extracellular proteins during the yeast-to-hypha transition, which led to a comprehensive C. albicans secretome map. The serological responses to C. albicans extracellular proteins were investigated by a 2D-immunoblotting approach combined with MS for protein identification. On the basis of the screening of sera from candidemia and three groups of noncandidemia patients, a core set of 19 immunodominant antibodies against secreted proteins of C. albicans was identified, seven of which represent potential diagnostic markers for candidemia (Xog1, Lip4, Asc1, Met6, Tsa1, Tpi1, and Prx1). Intriguingly, some secreted, strongly glycosylated protein antigens showed high cross-reactivity with sera from noncandidemia control groups. Enzymatic deglycosylation of proteins secreted from hyphae significantly impaired sera antibody recognition. Furthermore, deglycosylation of the recombinantly produced, secreted aspartyl protease Sap6 confirmed a significant contribution of glycan epitopes to the recognition of Sap6 by antibodies in patient's sera.
authors.forename: Ting
authors.initials: T
authors.lastname: Luo
authors.forename: Thomas
authors.initials: T
authors.lastname: Krüger
authors.forename: Uwe
authors.initials: U
authors.lastname: Knüpfer
authors.forename: Lydia
authors.initials: L
authors.lastname: Kasper
authors.affiliation: Department of Mass spectrometry/Proteomics, Max-Planck-Institute for Chemical Ecology , 07745 Jena, Germany.
authors.forename: Natalie
authors.initials: N
authors.lastname: Wielsch
authors.affiliation: Institute of Microbiology, Friedrich Schiller University Jena , 07743 Jena, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hube
authors.forename: Andreas
authors.initials: A
authors.lastname: Kortgen
authors.forename: Michael
authors.initials: M
authors.lastname: Bauer
authors.forename: Evangelos J
authors.initials: EJ
authors.lastname: Giamarellos-Bourboulis
authors.forename: George
authors.initials: G
authors.lastname: Dimopoulos
authors.affiliation: Institute of Microbiology, Friedrich Schiller University Jena , 07743 Jena, Germany.
authors.forename: Axel A
authors.initials: AA
authors.lastname: Brakhage
authors.affiliation: Institute of Microbiology, Friedrich Schiller University Jena , 07743 Jena, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Kniemeyer
mesh_terms: D000906:Antibodies / Q000032:analysis; D000937:Antigen-Antibody Reactions / Q000276:immunology*; D016282:Aspartic Acid Endopeptidases / Q000737:chemistry / Q000276:immunology; D002176:Candida albicans / Q000737:chemistry / Q000276:immunology* / Q000472:pathogenicity; D002853:Chromatography, Liquid; D005656:Fungal Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D006031:Glycosylation; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D025301:Hyphae / Q000737:chemistry*; D011134:Polysaccharides / Q000276:immunology; D040901:Proteomics / Q000379:methods*; D053719:Tandem Mass Spectrometry
chemical_list: D000906:Antibodies; D005656:Fungal Proteins; D011134:Polysaccharides; D016282:Aspartic Acid Endopeptidases; C582621:SAP6 protein, Candida albicans
keywords: Candida albicans; SERPA; antigens; extracellular proteins; glycosylation; immunoproteomics; secretome; yeast-to-hypha transition