Bound by infection: identifying how COVID-19 interacts with cells

Two international studies have shed light on why the virus that causes COVID-19 is so infectious compared to other SARS viruses.

University of Queensland researchers collaborated with colleagues in the United Kingdom and Europe on the studies, which also showed a way to potentially prevent the virus from infecting cells.

The SARS-CoV-2 virus uses a protein called Spike to enter host cells by binding to a receptor on human cells, called ACE2, and using it like a doorway to get in.

In a new study published in Science, Dr Giuseppe Balistreri of the University of Helsinki in Finland and Professor Mikael Simons of the Technical University of Munich in Germany collaborated with UQ researchers to show that the virus can also enter cells using another receptor, called neuropilin.

Working with Professor Frederic Meunier from UQ’s Queensland Brain Institute, they discovered that the neuropilin receptor, NRP1, is found on a variety of human cells, including those in the upper airways, which could explain why SARS-CoV-2 is more infectious and more extensively invasive than similar viruses.

Dr Balistreri said the fact that antibodies blocking NRP1 are able to block infection by 40 per cent strongly suggested that this pathway is key for the virus’ infectivity.

Professor Meunier said there was very little doubt that SARS-CoV-2 affects our brain cells and the long-term consequences are not yet known.

“The discovery that NRP1 binds to Spike opens the door to in-depth research into the virus’ neurotropism – its ability to infect nerve tissue – as well as new therapeutic avenues.”

Meanwhile, on another study also published in the same issue of Science, Dr Yohei Yamauchi and Professor Peter Cullen from the University of Bristol worked with other UQ researchers to investigate the interaction between the virus and this receptor.

Dr Kai-En (Kevin) Chen and Professor Brett Collins from UQ’s Institute for Molecular Bioscience were able to show exactly how the virus binds to a host cell by modelling the site where they interact.

“We now know that in addition to the already known ACE2 receptor, the Spike binds to a second receptor on the host cells called neuropilin,” Professor Collins said.

“We used X-ray crystallography to see the structure of proteins at the atomic level and visualise the binding sites at a spectacular level of detail.”

The University of Bristol team looked at the effect of disrupting the binding between the virus and cells.

“We discovered that by blocking the virus protein from attaching to cells, it was possible to reduce the infection rate of the virus,” Dr Yamauchi said.

“If we can make a drug that blocks the virus from binding to cells, this has potential as a new therapy for treating COVID-19.”

The sequence in the COVID-19-causing SARS-CoV-2 virus that binds to the receptor is found in other pathogenic human viruses such as Ebola and HIV-1, but not in SARS-CoV.

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