To date, the ongoing pandemic of COVID-19, caused by the emergence of the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) has resulted in more than a million infections and tens of thousands deaths, calling for immediate attention towards coronavirus research.

Coronaviruses are single-stranded RNA viruses that contain 4 structural proteins: the membrane (M), envelope (E), spike (S) and nucleocapsid (N) proteins. The spike protein is a trimeric transmembrane protein with N-linked glycosylation that has a vital role in the process of viral entry and fusion to the host cell, using the ACE2 protein as the receptor to enter the cells.

The role of glycosylation

The protruding N-linked glycosylation from the trimeric protein surface looks like a crown under the microscope giving it the name, coronavirus. The high level of glycosylation on the S proteins masks the actual protein surface, which prevents the access of antibodies that can neutralize it, helping the virus escape the immune system.

It has become increasingly clear that, like with many other viruses, glycosylation plays a key role in the infection of coronaviruses. This has drawn the interest of researchers to lectins, which are natural glyco-affinity proteins.

Lectins recognize and bind to specific glycan structures displayed on glycoproteins and other glycosylated biomolecules, making them an attractive research, and potentially therapeutic, tool for understanding and treating a viral infection.

Lectins can prevent viral entry

Plant-derived lectins with affinity for mannose have been found to be a potent inhibitor for the replication of SARS coronavirus. This antiviral activity is due to their binding to viral envelope glycans, which prevents entry of the virus into cells.

Additionally, lectins with affinity for mannose and N-acetylglucosamine (GlcNAc) glycans, have been identified as potential therapeutic agents in the prevention of viral transmission in HIV and coronaviruses (SARS-CoV and MERS-CoV). Keyaerts and Ritchie et al. showed that mannose-binding lectins interfere with this entry process by binding to the high-mannose type N-glycans of SARS-CoV of the spike, thereby preventing viral attachment to the host cell.

Similarly, GlycoSeLect´s Recombinant Prokaryotic Lectins, or RPLs, have shown good binding to the envelope protein of human immunodeficiency virus HIV (GlycoSelect – presentation at the NIH workshop, 26th April 2019).

Impactful coronavirus research

The evidence suggests that the glycosylation of the viral proteins cannot be overlooked and should be considered carefully while designing therapeutics. We believe that for conducting impactful research on coronaviruses, lectin proteins that recognize unique glycans could play a big role in virus analytics, vaccine purification and could also be considered as antiviral therapeutics.

To learn more about GlycoSeLect’s RPL lectins and their applications click here.