• New strain appears to be more readily transmitted from human to human than Sars, Texas researchers find
  • Further studies needed to explore human host cells’ role in spread between people, the report says
An electron microscope image shows the coronavirus emerging from the surface of cells. Photo: Handout

The deadly new coronavirus is up to 20 times more likely to bind to human cell receptors and cause infection than severe acute respiratory syndrome (Sars), a new study by researchers at the University of Texas at Austin has found.

The novel coronavirus and Sars share the same functional host-cell receptor, called angiotensin-converting enzyme 2 (ACE2).

The report, published on the website bioRxiv on Saturday, said the new coronavirus had around 10 to 20-fold higher affinity " the degree to which a substance tends to combine with another " for human ACE2 compared with Sars.

But the researchers added that further studies were needed to explore the human host-cell receptor's role in helping the new virus to spread from person to person.

"Compared with SARS-CoV, 2019-nCoV appears to be more readily transmitted from human to human," the report of the study said. "The high affinity of 2019-nCoV S for human ACE2 may contribute to the apparent ease with which 2019-nCoV can spread from human to human."

The disease caused by the new coronavirus, which the World Health Organisation (WHO) has named Covid-19, has killed more than 1,800 people and infected over 70,000 worldwide.

The number of Covid-19 deaths is more than double the global figure of 813 attributed by the WHO to the Sars epidemic of 2002-03.

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The new study found that although the novel coronavirus' receptor-binding domain (RBD) had a relatively similar structure to that of Sars, it did not have appreciable binding to three published Sars RBD-specific monoclonal antibodies (mAbs), which are copies of one type of antibody used to neutralise pathogens.

The researchers said this suggested antibody cross-reactivity " the extent to which different antigens appear similar to the immune system " may be limited between the two virus RBDs, meaning Sars-directed mAbs will not necessarily work against the new virus.

Instead, they identified the spike protein of coronaviruses, which is essential to gain entry into host cells during the infection process, as the most important target for vaccines, therapeutic antibodies and diagnostics.

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"Due to the indispensable function of the (spike) protein it represents a vulnerable target for antibody-mediated neutralisation," the report said. "Knowing the atomic-level structure of the spike will support precision vaccine design and discovery of antivirals, facilitating medical countermeasure development."

The WHO has declared the outbreak a global public health emergency, making it the sixth incident to date to warrant that designation.

There are currently no specific treatments for the novel coronavirus but the WHO director general Tedros Adhanom Ghebreyesus said last week that the first vaccine may be available in 18 months.

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