Distinct core glycan and -glycoform utilization of SARS-CoV-2 Omicron variant Spike protein RBD revealed by top-down mass spectrometry

• Published in: Chemical science (Cambridge) Vol. 13; no. 36; pp. 1944 - 1949
• Main Authors: Roberts, David S, Mann, Morgan, Li, Brad H, Kim, Donguk, Braiser, Allan R, Jin, Song, Ge, Ying
• Format: Journal Article
• Published: 21.09.2022
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d2sc02132c

The SARS-CoV-2 Omicron (B.1.1.529) variant possesses numerous spike (S) mutations particularly in the S receptor-binding domain (S-RBD) that significantly improve transmissibility and evasion of neutralizing antibodies. But exactly how the mutations in the Omicron variant enhance viral escape from immunological protection remains to be understood. The S-RBD remains the principal target for neutralizing antibodies and therapeutics, thus new structural insights into the Omicron S-RBD and characterization of the post-translational glycosylation changes can inform rational design of vaccines and therapeutics. Here we report the molecular variations and O -glycoform changes of the Omicron S-RBD variant as compared to wild-type (WA1/2020) and Delta (B.1.617.2) variants using high-resolution top-down mass spectrometry (MS). A novel O -glycosite (Thr376) unique to the Omicron variant is identified. Moreover, we have directly quantified the Core 1 and Core 2 O -glycan structures and characterized the O -glycoform structural heterogeneity of the three variants. Our findings reveal high resolution detail of Omicron O -glycoforms and their utilization to provide direct molecular evidence of proteoform alterations in the Omicron variant which could shed light on how this variant escapes immunological protection. Top-down mass spectrometry reveals O -glycoform structural changes in the SARS-CoV-2 Omicron variant. Resolving the mutations and post-translational alterations can inform strategies for designing variant-directed diagnostics and therapeutics.