Let us study viruses and the role of sialic acids in their first step of reproduction, the attachment to cells. We begin our study with the help of the "Earth's virology course", created by Vincent Racaniello, with David Tuller and Gertrud U. Rey. The first virus that we will study is that of influenza A. Actually, "Earth's virology course" is a proper starting point for learning the mechanisms the virus uses to attach and enter the host cells. In the case of the influenza virus, its spike protein is used to attach the virion to sialic acid receptors of the host cells. Then we will consider coronaviruses, with the help of literature about the role of sialic acids in their attachment by means of spike proteins. In fact, there are seven human coronavirus, and they use sialic acid or angiotensin-converting enzyme 2 (ACE2) or other receptors or a combination of them. We can find in literature that Sars-Cov-2 virus can use sialic acid too for the attachment to cells, but its main target is considered the ACE2 receptor.

See please the new version, with more references --- The study in 10.1021/acscentsci.0c00855 used a glyco-nanoparticle platform, discovering that N-acetyl neuraminic acid has affinity toward the SARS-COV-2 spike glycoprotein, that is a glycan-binding function. However, a recent study, 10.1016/j.scib.2021.01.010, which has investigated the binding of the spikes of the virus by means of micro-arrays, tells that no binding with sialic acid residues was detected. All the tested protein molecules can bind to heparan sulfate glycans (as in 10.1016/j.cell.2020.09.033) in a sulfation-dependent manner. PLEASE, see the new version for more details.