The SARS-CoV-2 coronavirus, the etiologic agent of
COVID-19, uses its spike (S)
glycoprotein anchored in the viral membrane to enter host cells. The S
glycoprotein is the major target for
neutralizing antibodies elicited by natural
infection and by
vaccines. Approximately 35% of the SARS-CoV-2 S
glycoprotein consists of
carbohydrate, which can influence virus infectivity and susceptibility to antibody inhibition. We found that virus-like particles produced by coexpression of SARS-CoV-2 S, M, E and N
proteins contained spike
glycoproteins that were extensively modified by complex
carbohydrates. We used a
fucose-selective
lectin to enrich the Golgi-resident fraction of a wild-type SARS-CoV-2 S
glycoprotein trimer, and determined its glycosylation and
disulfide bond profile. Compared with soluble or solubilized S
glycoproteins modified to prevent proteolytic cleavage and to retain a prefusion conformation, more of the wild-type S
glycoprotein N-linked
glycans are processed to complex forms. Even Asn 234, a significant percentage of which is decorated by high-
mannose glycans on soluble and virion S trimers, is predominantly modified in the Golgi by processed
glycans. Three incompletely occupied sites of O-linked glycosylation were detected. Viruses pseudotyped with natural variants of the
serine/
threonine residues implicated in O-linked glycosylation were generally infectious and exhibited sensitivity to neutralization by soluble ACE2 and convalescent
antisera comparable to that of the wild-type virus. Unlike other natural
cysteine variants, a Cys15Phe (C15F) mutant retained partial, but unstable, infectivity. These findings enhance our understanding of the Golgi processing of the native SARS-CoV-2 S
glycoprotein carbohydrates and could assist the design of interventions.