N-Glycome Profile of the Spike Protein S1: Systemic and Comparative Analysis from Eleven Variants of SARS-CoV-2

The SARS-CoV-2 virus rapidly spread worldwide, threatening public health. Since it emerged, the scientific community has been engaged in the development of effective therapeutics and vaccines. The subunit S1 in the spike protein of SARS-CoV-2 mediates the viral entry into the host and is therefore one of the major research targets. The S1 protein is extensively glycosylated, and there is compelling evidence that glycans protect the virus' active site from the human defense system. Therefore, investigation of the S1 protein glycome alterations in the different virus variants will provide a view of the glycan evolution and its relationship with the virus pathogenesis. In this study, we explored the N-glycosylation expression of the S1 protein for eleven SARS-CoV-2 variants: five variants of concern (VOC), including alpha, beta, gamma, delta, and omicron, and six variants of interest (VOI), including epsilon, eta, iota, lambda, kappa, and mu. The results showed significant differences in the N-glycome abundance of all variants. The N-glycome of the VOC showed a large increase in the abundance of sialofucosylated glycans, with the greatest abundance in the omicron variant. In contrast, the results showed a large abundance of fucosylated glycans for most of the VOI. Two glycan compositions, GlcNAc₄,Hex₅,Fuc,NeuAc (4-5-1-1) and GlcNAc₆,Hex₈,Fuc,NeuAc (6-8-1-1), were the most abundant structures across all variants. We believe that our data will contribute to understanding the S1 protein's structural differences between SARS-CoV-2 mutations.