Evaluation of immunostimulatory activities of synthetic mannose-containing structures mimicking the β-(1->2)-linked cell wall mannans of Candida albicans

Abstract

Immunostimulatory properties of synthetic structures mimicking the β-(1→2)-linked mannans of Candida albicans were evaluated in vitro. Contrary to earlier observations, tumor necrosis factor (TNF) production was not detected after stimulation with mannotetraose in mouse macrophages. Divalent disaccharide 1,4-bis(α-D-mannopyranosyloxy)butane induced TNF and some molecules induced low levels of gamma interferon (IFN-γ) in human peripheral blood mononuclear cells (PBMC).

Fig 1

(A) Structures of the β-(1→2)-linked mannosides mannobiose (1), mannotriose (2), and mannotetraose (3). (B) TNF production (mean and standard error of the mean [SEM]) from mouse macrophage cell lineage J774.2 as measured with Luminex after stimulation with compound 3 (○) and mild-acid-hydrolyzed Candida albicans mannan (●). (C) Inductions of IFN-γ secretion in PBMC by compounds 1 (■), 2 (▲), and 3 (○). IFN-γ responses were measured either as mRNA expression in PBMC with TaqMan or as IFN-γ production by PBMC measured with Luminex after stimulation with at least two concentrations of the compounds. Fold changes in the IFN-γ responses (mean and SEM) compared to that in the unstimulated culture are shown on the y axis.

Fig 2

(A) Structures of the β-(1→2)-linked mannoglycosides cyclohexyl β-d-mannopyranosyl-(1→2)-α-d-mannopyranoside (4), methyl β-d-mannopyranosyl-(1→2)-α-d-mannopyranoside (5), and methyl β-d-mannopyranosyl-(1→2)-β-d-mannopyranosyl-(1→2)-α-d-mannopyranoside (6). (B) IFN-γ responses in PBMC after stimulation with compounds 4 (○), 5 (■), and 6 (▲). IFN-γ responses were measured either as mRNA expression in PBMC with TaqMan or as IFN-γ production by PBMC measured with Luminex. Fold changes in the IFN-γ responses compared to that in the unstimulated culture (mean and SEM) are shown on the y axis.

Fig 3

(A) Glucose-containing structures of methyl 2-acetamido-2-deoxy-β-d-glucopyranosyl-(1→2)-α-d-mannopyranoside (7), methyl β-d-glucopyranosyl-(1→2)-α-d-mannopyranoside (8), and methyl β-d-glucopyranosyl-(1→2)-β-d-mannopyranosyl-(1→2)-α-d-mannopyranoside (9). (B) Induction of IFN-γ secretion in PBMC after stimulation with compounds 7 (○), 8 (■), and 9 (▲). IFN-γ responses were measured as mRNA expression in PBMC with TaqMan. Fold changes in the IFN-γ expression (mean and SEM) compared to that in the unstimulated culture are shown on the y axis.

Fig 4

(A) Divalent structures of 1,4-bis(α-d-mannopyranosyloxy)butane (10), 1,4-bis(2-O-β-d-mannopyranosyl-(1→2)-α-d-mannopyranosyloxy)butane (11), 1,4-bis(cyclohexyl 2-O-α-d-mannopyranosyl)butane (12), 1,4-bis(2-O-d-mannopyranose)butane (13), 1,4-bis(2-O-β-d-mannopyranosyl-(1→2)-d-mannopyranose)butane (14), and 1,4-bis(methyl-α-d-mannopyranosyl-(2→1)-2-O-β-d-glucopyranosyl)butane (15). (B) Fold increases in PBMC cytokine production after divalent oligosaccharide stimulations. Production of IFN-γ, IL-4, TNF, and IL-10 was measured (mean and SEM) with Luminex at 72 h after stimulations with various concentrations of the divalent saccharide compounds 10 (♢), 11 (■), 12 (△), 13 (○), 14 (▲), and 15 (●).