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Immunoproteomic analysis of antibody responses to extracellular proteins of Candida albicans in serum of candidemia patients revealed glycosylation effects on protein antigen recognition

ABSTRACT: During infection the yeast Candida albicans undergoes a yeast-to-hyphal transition and secretes numerous proteins required for the invasion and damage of host tissues and the modulation of the host immune responses. Still little is known about the interplay of Candida albicans secreted proteins and the host adaptive immune system. For the characterization of the extracellular proteins of C. albicans and their ability to trigger a serological response in candidemia patients we applied 2D gel electrophoresis and LC-MS/MS-based approaches. These analyses identified the secretion of 101 different proteins from C. albicans yeast cells and 410 proteins from hyphal cells. Morphology-dependent changes of the secretome were mostly associated with proteins involved in cell wall organization, general stress response and the interplay with host immune cells. Our immunoproteomics workflow for the identification of secreted C. albicans protein antigens revealed a core set of 20 immunodominant specific anti- C. albicans protein antibodies. However, some secreted protein antigens showed cross-reactivity with sera from control groups without Candida infection. Glycoprotein staining of C. albicans hyphal secretome demonstrated that some secreted proteins are strongly glycosylated. Enzymatic deglycosylation of secreted proteins uncovered a significant contribution of glycan epitopes to the recognition of the secreted aspartyl protease Sap6 by IgG antibodies from patient sera.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Candida Albicans (yeast)

SUBMITTER: Thomas Krueger

LAB HEAD: Olaf Kniemeyer

PROVIDER: PXD003201 | Pride | 2022-03-03

REPOSITORIES: Pride

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Project description:Candida albicans is an opportunistic pathogen and a commensal fungus of the mucosa from many healthy patients. Invasive candidiasis (IC) has high levels of morbidity and mortality that are attributed to some extent to the difficulty in its early diagnosis. Diverse and immunogenic proteins with roles such as virulence and immune evasion are secreted by this pathogen. Immunoproteomics is an important technique for the assessment of antibody reactivities to immunogenic proteins and our group previously developed an algorithm to predict the clinical outcome in IC patients. With the ultimate purpose of discovering new biomarkers of IC, immunoproteomics was applied for the analysis of the serological response to hyphal C. albicans extracellular proteins. Gel-free proteomic analysis was performed by LC-MS/MS for the detection of the secreted proteins and 301 proteins were identified. As expected, gene ontology analysis in cellular component showed enrichment in proteins from extracellular region, cell wall, cell surface, cell periphery and intracellular region. Importantly, 46.5% of the intracellular proteins identified were also annotated in extracellular region. Furthermore, from the extracellular proteins identified here, 44 proteins were previously found to be immunogenic against human sera. To carry out immunoproteomic analysis, secreted proteins were separated by two-dimensional gel electrophoresis, electroblotted onto nitrocellulose membranes, and tested by Western blotting with three distinct pools of human sera: P1 (12 IC patients), P2 (11 patients with Candida infection associated with catheters) and P3 (11 patients without IC). A higher reactivity pattern was observed in P1 and P2 in comparison with P3. So far, Glx3 was immunogenic to P1 and P2 but not to P3. Eno1, Pgk1 and Pra1 were found to be more immunoreactive to both P1 and P2 than to the P3. This approach will contribute to a better and faster diagnosis of this life-threatening fungal infection.

			Action	DRS
	HyphaeBR1a.mgf	Mgf
	HyphaeBR1a.mzid.gz	Mzid
	HyphaeBR1a.raw	Raw
	HyphaeBR1b.mgf	Mgf
	HyphaeBR1b.mzid.gz	Mzid

Dataset Information

Immunoproteomic analysis of antibody responses to extracellular proteins of Candida albicans in serum of candidemia patients revealed glycosylation effects on protein antigen recognition

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