Background
Congenital disorders of glycosylation (CDGs) are genetic diseases caused by gene defects in glycan biosynthesis pathways, and there is an increasing number of patients diagnosed with CDGs. Because CDGs show many different clinical symptoms, their accurate clinical diagnosis is challenging. Recently, we have shown that liposome nanoparticles bearing the ALG1-CDG and PMM2-CDG biomarkers (a tetrasaccharide: Neu5Ac-α2,6-Gal-β1,4-GlcNAc-β1,4-GlcNAc) stimulate a moderate immune response, while the generated antibodies show relatively weak affinity maturation. Thus, mature antibodies with class switching to IgG are desired to develop high-affinity antibodies that may be applied in medical applications.
Results
In the present study, a liposome-based vaccine platform carrying a chemoenzymatic synthesized phytanyl-linked tetrasaccharide biomarker was optimized. The liposome nanoparticles were constructed by dioleoylphosphatidylcholine (DOPC) to improve the stability and immunogenicity of the vaccine, and adjuvanted with the NKT cell agonist PBS57 to generate high level of IgG antibodies. The results indicated that the reformulated liposomal vaccine stimulated a stronger immune response, and PBS57 successfully induce an antibody class switch to IgG. Further analyses of IgG antibodies elicited by liposome vaccines suggested their specific binding to tetrasaccharide biomarkers, which were mainly IgG2b isotypes.
Conclusions
Immunization with a liposome vaccine carrying a carbohydrate antigen and PBS57 stimulates high titers of CDG biomarker-specific IgG antibodies, thereby showing great potential as a platform to develop rapid diagnostic methods for ALG1-CDG and PMM2-CDG.
Graphical Abstract
Sialyl galactose (Sia-Gal) is one of the most abundant terminal motifs of oligosaccharides and is widely present in glycoconjugates and unconjugated glycans of animals. To investigate their function and biological roles, it is essential to obtain terminally structurally defined oligosaccharides. Herein, we describe a convenient and efficient strategy for the regioselective modification of glycans with terminal galactose (Gal) or Sia-Gal residues using immobilized enzymes. Galactosyltransferase (GalT) and sialyltransferase (ST) were encapsulated on the surface of yeast spores, which enabled facile assembly of diverse naturally occurring sialyl-galactosylated glycans, including human milk oligosaccharide, N-glycan biomarker, O-Man glycan, and O-GalNAc glycan. The utility of this strategy was further demonstrated by systematic construction of a panel of Core 2 O-GalNAc glycans.
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