Researchers Identify Human Protein That May Explain Why SARS-CoV-2 Is Highly Infectious

A creative rendition of SARS-CoV-2 virus particles with its spike proteins shown in red. NIAID/CC BY 2.0

Scientists have made an important discovery that could explain why SARS-CoV-2, the coronavirus that causes Covid-19, is so fiendishly infectious. Not only does the breakthrough help add to our understanding of the virus, it could also be used to develop a new anti-viral treatment to battle against Covid-19. 

It’s all to do with the spike protein of the virus and its interactions with a protein on the surface of human cells called neuropilin-1. Spike proteins studded on the outside surface of the virus target and fuse with the host cell in the first phase of infection. Once attached, the virus hacks into the cell and releases its genetic material, hijacking the host cell's machinery to create multiple copies of itself. Most viral infections work in this way, however, it appears that SARS-CoV-2 is exceptionally skilled at this invasion process. 

It's already known that SARS-CoV-2 gets access to the human cells via a receptor called ACE2. Now, researchers have found a secondary receptor that the SARS-CoV-2 uses to infect cells – neuropilin-1 – which contains a number of features that help to explain why the virus is so infectious and able to spread quickly between human cells.

In a study published in the journal Science, research led by Professor Peter Cullen, Dr Yohei Yamauchi, and Dr Boris Simonetti from the University of Bristol in the UK has shown how SARS-CoV-2 uses neuropilin-1 to recognize and fuse to the surface of human cells. 

“In looking at the sequence of the SARS-CoV-2 Spike protein, we were struck by the presence of a small sequence of amino acids that appeared to mimic a protein sequence found in human proteins which interact with neuropilin-1,” they explained in a statement“This led us to propose a simple hypothesis: could the Spike protein of SARS-CoV-2 associate with neuropilin-1 to aid viral infection of human cells?”

“Excitingly, in applying a range of structural and biochemical approaches we have been able to establish that the spike protein of SARS-CoV-2 does indeed bind to neuropilin-1,” the authors said.

Based on this observation, they suggest that SARS-CoV-2 effectively “tricks” the neuropilin-1 protein. Since the sequence of amino acids on SARS-CoV-2 looks a lot like other normal human proteins, neuropilin-1 is more likely to let the intruder into the cell. 

The findings echo research from scientists at the Technical University of Munich in Germany and the University of Helsinki in Finland, which also found that neuropilin-1 plays an important role in the cell entry of SARS-CoV-2, though it is yet to be peer-reviewed. 

The discovery could be used to develop promising anti-viral therapeutics against Covid-19. Armed with the new knowledge, the researchers have developed a potential anti-viral treatment that could, in theory, dramatically reduce the viral infectivity of SARS-Cov-2. 

“By using monoclonal antibodies – lab-created proteins that resemble naturally occurring antibodies – or a selective drug that blocks the interaction we have been able to reduce SARS-CoV-2’s ability to infect human cells,” the team explained. “This serves to highlight the potential therapeutic value of our discovery in the fight against Covid-19.

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