Abstract
Antibody effector functions have been shown to be influenced by the structure of the Fc N-glycans. Here we studied the changes in plasma or serum IgG Fc N-glycosylation upon vaccination of 10 Caucasian adults and 10 African children. Serum/plasma IgG was purified by affinity chromatography prior to and at two time points after vaccination. Fc N-glycosylation profiles of individual IgG subclasses were determined for both total IgG and affinity-purified anti-vaccine IgG using a recently developed fast nanoliquid chromatography-electrospray ionization MS (LC-ESI-MS) method. While vaccination had no effect on the glycosylation of total IgG, anti-vaccine IgG showed increased levels of galactosylation and sialylation upon active immunization. Interestingly, the number of sialic acids per galactose increased during the vaccination time course, suggesting a distinct regulation of galactosylation and sialylation. In addition we observed a decrease in the level of IgG1 bisecting N-acetylglucosamine whereas no significant changes were observed for the level of fucosylation. Our data indicate that dependent on the vaccination time point the infectious agent will encounter IgGs with different glycosylation profiles, which are expected to influence the antibody effector functions relevant in immunity.
Highlights
Millions of individuals are vaccinated worldwide each year to stimulate the adaptive immune system to produce protective antibodies as well as T-cell responses against a variety of pathogens
The two light chains together with the N-terminal domains (VH and CH1) of the two heavy chains form the fragment antigen binding (Fab) moiety, whereas the fragment crystallizable (Fc) moiety is formed by the C-terminal domains (CH2 and CH3) of the two heavy chains
In vitro stimulation of B cells with the environmental factor all-trans retinoic acid resulted in the expression of IgG1 with decreased galactosylation within a time-range of several days, whereas increased galactosylation and reduced bisecting GlcNAc have been observed after stimulation with CpG oligodeoxynucleotide or interleukin 21 [9]
Summary
In a murine nephrotoxic serum nephritis model, total IgG sialylation has been shown to reduce drastically in mice pre-sensitized with sheep IgG and challenged with sheep anti-mouse glomerular basement membrane preparation compared with unimmunized controls [4]. Repeated immunization of male ICR mice with ovalbumin in physiological saline resulted in an increase of the fucose content on anti-ovalbumin IgG, whereas mannosylation, galactosylation, and sialylation were unaffected [11] These animal studies demonstrate that upon immunological challenge glycosylation of the produced antibodies differ. Because of the high sensitivity of the mass spectrometric detection it is possible to set up affinity-based microtitration well plate IgG capturing and purification assays as modifications of (commercially available) ELISAs and combine them successfully with IgG glycosylation profiling of glycopeptides [13] This allows glycan profiling at the level of antigen-specific IgG. On the basis of the known association of IgG glycosylation features with antibody efficacy in in vitro assays and animal models (4 – 6, 17–20), we expect that the specific IgG1 glycosylation features observed upon vaccination will influence antibody effector functions
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