Exploiting glycosylation against COVID-19

Lead Research Organisation: Liverpool School of Tropical Medicine
Department Name: Vector Biology


In this project, we aim to expand our understanding on and exploit the essentiality of protein N-glycosylation for the control of SARS-CoV-2 transmission. N-glycosylation is the most common eukaryotic post-translational modification of proteins; it plays important roles, including protein folding and targeting as well as cell function. All SARS-CoV-2 proteins are predicted to be N-glycosylated, specially the surface homotrimeric Spike protein, which has been confirmed to have 22 N-glycans per monomer and whose structures have been recently determined. It is well known from similar coronaviruses (e.g., SARS-CoV, M-CoV) that surface glycans are important to modulate binding to the host receptor ACE2, and to reduce the accessibility of neutralising antibodies by hindering immunogenic epitopes. Although a lot of information has been obtained on the glycan structures of the Spike protein, to our knowledge, few functional studies on SARS-CoV-2 glycosylation have been performed so far. We hypothesise that interrupting the glycosylation of SARS-CoV-2 and/or host proteins will prevent viral infection and also render the virus more susceptible to the human immune system. We will do this using mainly two approaches: 1) by pharmacological inhibition of the N-glycosylation machinery and 2) by mutagenising specific N-glycan sequons on the virus Spike protein. We intend to translate the generated data into novel glycan-based therapeutics including repurposed glycosylation inhibitors to treat the disease. Our studies may also generate attenuated vaccine strains to prevent COVID-19 transmission.


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Description The overarching aim of this project was to understand the essentiality of protein glycosylation for SARS-CoV-2 infection, and to determine whether this knowledge could be exploited to develop new therapeutic strategies against COVID-19. The project has successfully achieved its goal by obtaining the following key findings (results published in Casas-Sanchez et al. 2022 mBio; and in several manuscripts currently in preparation):

i) Protein N-glycosylation is essential for SARS-CoV-2 infection, as inhibition of the host N-glycosylation pathway using either chemical (inhibitor drugs) or genetic (interference RNA) methods successfully reduced or even blocked the development of the infection in human lung cells in vitro. Preliminary data (under analysis) suggests these effects are also observed in vivo using glycosylation inhibitors in a humanised mouse model.

ii) Specific SARS-CoV-2 Spike N-glycans are essential for cell invasion, as the enzymatic removal of such glycans leads to the complete loss of virion infectivity. A proportion of virions produced in the presence of inhibited glycosylation renders non-infective due to significant changes in these glycans.

iii) Virions produced in the presence of inhibited glycosylation, which remain infective, are more susceptible to neutralisation by vaccine-derived antibodies.
In summary, by altering and/or inhibiting protein N-glycosylation using a broad variety of methods (e.g., glycosylation inhibitors), SARS-CoV-2 infection is reduced, and fewer resulting virions can be neutralised by lower titres of vaccine-derived antibodies. These findings open the door to further exploring the use of glycosylation inhibitors (including FDA-approved drugs) and other innovative glycan-targeting strategies (e.g., enzymatic nanobody-targeted deglycosylation) to tackle COVID-19, including future SARS-CoV-2 variants of concern and coronaviruses.
Exploitation Route We will seek more funding in order to test in animal models the efficacy of our repurposed drugs against a SARS-CoV-2 infections.
Sectors Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

Description We have successfully identified protein glycosylation, one of the most common modifications of both human and viral proteins, as a promising molecular target to combat SARS-CoV-2 infections. Our research has demonstrated that protein glycosylation plays a crucial role in the development of the infection, as inhibiting it using specific drugs - including some already approved to treat unrelated human diseases - leads to a reduction or complete block of the infection. We have also identified specific virus glycosylation sites that can be targeted to render the virus unable to infect cells. Moreover, our studies have shown that viruses produced in cells treated with such drugs are more susceptible to be neutralised by antibodies produced by vaccinated individuals. These important findings suggest that therapeutic strategies targeting glycosylation, such as these drugs, could be used as COVID-19 therapeutics. This is due to the dual activity of these drugs in reducing the expansion of the infection and enhancing the effectiveness of vaccines, even against new variants of concern.
First Year Of Impact 2023
Sector Healthcare