Abstract
Viral protein glycosylation represents a successful strategy employed by the parasite to take advantage of host–cell machinery for modification of its own proteins. The resulting glycans have unneglectable roles in viral infection and immune response. The spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which presents on the surface of matured virion and mediates viral entry into the host, also undergoes extensive glycosylation to shield it from the human defense system. It is believed that the ongoing COVID-19 pandemic with more than 90,000,000 infections and 1,900,000 deaths is partly due to its successful glycosylation strategy. On the other hand, while glycan patches on S protein have been reported to shield the host immune response by masking “nonself” viral peptides with “self-glycans,” the epitopes are also important in eliciting neutralizing antibodies. In this review, we will summarize the roles of S protein glycans in mediating virus–receptor interactions, and in antibody production, as well as indications for vaccine development.
Highlights
Since its first emergence in December 2019, it only took several months before the novel coronavirus disease 2019 (COVID-19), a severe respiratory illness, was declared as a pandemic by the World Health Organization
The causative agent was identified to be a member of Betacoronavirus and termed as SARS-CoV-2 (Coronaviridae Study Group of the International Committee on Taxonomy of Viruses, 2020)
It has been reported that S of SARS-CoV-2 contains a furin cleavage site, which contains multiple basic amino acids (PRRAR) and can be cleaved into two functional subunits: S1 subunit, which is responsible for binding to cellular receptor; and S2 subunit, which functions to fuse the viral and cellular membranes (Hoffmann et al, 2020; Walls et al, 2020; Xia et al, 2020)
Summary
Since its first emergence in December 2019, it only took several months before the novel coronavirus disease 2019 (COVID-19), a severe respiratory illness, was declared as a pandemic by the World Health Organization (https://www.who.int/docs/default-source/coronaviruse/situation-reports/ 20200311-sitrep-51-covid-19.pdf?sfvrsn 1ba62e57_10). The spike protein (S) of coronavirus, which forms large protrusions from the virus surface and gives the virus the appearance of having crowns, mediates virus entry into host cells (Hu et al, 2020; Cui et al, 2019; Hasöksüz et al, 2020; Virology, 1968). Different from bacteria, in which glycans are encoded by the bacterial genome and are treated as “nonself” epitopes by corresponding hosts, viruses take advantage of host cell machinery for glycosylation and generally are decorated with the “self”-glycans. These “self”-glycans are generally thought to be a strategy to escape the host immune response (Wang, 2020). We will mainly focus on the glycosylation of S protein
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