Zoonoses are diseases that are transmissible across difference species. Glycosylation is fundamental for this inter-species transmission and host-pathogen co-evolution. It is well established that pathogen strategies for infection require recognition of host species glyco-epitopes, adhesion and invasion into the host tissue. In consequence, there has been a constant evolutionary pressure controlling the interplay between evolution of pathogen glycan binding proteins such as hemagglutinins and its corresponding host glycosylation and vice versa. However, to date the glyco-epitope niche across Class Vertebrata is still largely undefined thereby limiting our ability to understand and systematically investigate the extant of cross-species transmission potential of zoonotic diseases.
Serum/plasma contains the largest dynamic range of easily accessible, species-specific glycoproteins including important immunity associated circulatory proteins such as Immunoglobulins (Igs). Hence, it provides an archive of species-specific pathophysiological glyco-information. The major Igs existing across the members of the Class vertebrata (such as IgG in mammals, IgY in birds and reptiles, the primordial IgNARs in sharks) is intriguingly diverse signifying host-pathogen co-evolution.
We have laid the foundation for a novel database to systematically curate glycan diversity existing in vertebrate serum/plasma and their corresponding Igs. We have enriched the major Immunoglobulin component of all our vertebrate candidates. We have been systematically mapping the glycome in vertebrate serum/plasma and their corresponding Igs by applying an orthogonal set of different N- and O-glycomics approaches (Porous Graphitised Carbon nano-Liquid Chromatography coupled to ESI MS/MS [PGC nano-LC ESI MS/MS], MALDI TOF MS) including separate arrays for capturing sialic acid diversity (HPLC of DMB-labelled sialic acids). We have hitherto accomplished mapping the serum/plasma N- and O- glycome of 35 different vertebrate species spanning 21 mammals, 6 birds, 5 reptiles and 3 fish with at least one corresponding individuals per species. With a well-established PGC based chromatographic system in our lab, we could differentiate the intensity variation of sialic acid linkage based on the retention time of glycans. The same was verified on the MALDI TOF MS by derivatising the glycans by ethyl esterification which gave a distinct m/z peak for α2-6 and α2-3 linked sialic acids.
Higher incidence of α-Gal epitopes was witnessed in Green sea turtles and predominantly Neu5Ac associated mono, disialylated glycans in birds. The same glycomic pattern was observed in Chicken IgY enriched from the corresponding serum. The results are organised as a species-based heat map and the profound difference and similarities in vertebrate serum/plasma glycan expression is registered.