Coronavirus is ‘uniquely adapted to infect humans’

Published by The Mail on Sunday (24th May, 2020)

A team of scientists has produced evidence that the pandemic virus is ‘uniquely adapted to infect humans’, raising fresh questions over whether its origins were natural or could have occurred in a laboratory.

Professor Nikolai Petrovsky, a top vaccine researcher who headed the Australian team, said the virus was ‘not typical of a normal zoonotic [animal to human] infection’ since it appeared with the ‘exceptional’ ability to enter human bodies from day one.

He said the virus should have emerged from an animal through ‘a freak event of nature’ but the possibility that it had leaked from a laboratory could not be ruled out.

Petrovsky, professor of medicine at Flinders University in Adelaide, runs a biotech research unit that will start human trials for a Covid-19 vaccine next month. ‘I haven’t seen a zoonotic virus that has behaved in this way before,’ he said.

He told The Mail on Sunday that new viruses crossing over from animals normally strengthen as they adapt to human hosts, but for unexplained reasons, this new coronavirus seems perfectly adapted to infect humans without the need to evolve.

He pointed to the ‘coincidence’ that the most closely related known viruses were being studied in a laboratory in Wuhan, the Chinese city where the pandemic erupted, and insisted that the possibility of a leak, however remote, should not be ignored in the search for its origin.

‘The implications may not be good for scientists or global politics, but just because the answers might cause problems, we can’t run away from them,’ he added. ‘There is currently no evidence of a leak but enough circumstantial data to concern us. It remains a possibility until it is ruled out.’

Prof Petrovsky has gone further than any other expert in raising the idea that the virus escaped from one of two laboratories researching bat viruses in Wuhan.

Richard Ebright, one of the world’s top biosecurity experts, also told this newspaper that the odds of this new virus containing such unusual features and occurring naturally were ‘possible – but improbable’.

Ebright, professor of chemical biology at Rutgers University, in New Jersey, said scientists at the Wuhan Institute of Virology were creating chimeric coronaviruses (new hybrid micro-organisms) and seeking funding to test their ability to infect human cells while using procedures that leave no sign of human manipulation.

Asked about the chance of a leak, he replied: ‘There definitely is a possibility. But there is no basis to say a high probability.’

Last week, the MoS revealed details of a key study challenging China’s claims that the pandemic emerged from a Wuhan animal market in December. The researchers were ‘surprised’ to find the virus ‘already pre-adapted to human transmission’, contrasting its stability with another coronavirus that evolved rapidly as it spread around the planet during the 2002-04 SARS epidemic.

Their findings are backed by the Australian team’s study into the ‘spike protein’ that binds Sars-CoV-2 – the new strain of coronavirus that causes disease – to cells in human bodies. The research, posted on Cornell University’s website but not yet peer-reviewed, used computer modelling to test the spike protein’s ability to bind to humans and 12 possible animal hosts.

It found the ability to bind to human cells far exceeded its ability in other species. ‘This indicates Sars-CoV-2 is a highly adapted human pathogen,’ it said, ‘raising questions as to whether it arose in nature by a rare chance event or whether its origins lie elsewhere.’

Prof Petrovsky said it seemed ‘very unusual’ for an ‘exquisitely human adaptive virus’ to have suddenly crossed from an animal host to humans last year.

‘This is either a remarkable coincidence or a sign of human intervention,’ he said. ‘It is possible the virus was a fluke event and it turns out humans were the perfect host.

‘But we don’t have evidence for this because no one has found this virus in an intermediate host animal [for example pangolin] yet. No one can say a laboratory leak is not a possibility.’

He claimed that scientists were reluctant to discuss the possibility of botched lab experiments or leaks since any backlash could lead to research restrictions and threaten crucial research. However, he added, it was vital to discover the source of the virus.

Prof Petrovsky said that if Sars-CoV-2 was a natural event, another related virus could erupt again from the same source with even more devastating consequences. ‘Next time, it could have far worse mortality rates,’ he warned.

He also highlighted the ‘furin cleavage site’, which allows the spike protein to bind to cells in human tissues including the lungs, liver and small intestines.

Previous studies have noted the efficiency of this cleavage method, which does not exist in the most similar coronaviruses – although researchers in 2009 modified the SARS virus to introduce a furin cleavage site in a similar position to Sars-CoV-2 and found this increased the infectivity of the virus.

In the latest study published on Friday, three German scientists highlighted how this cleavage site was essential for the infection of human lung cells. One US expert in biomedical sciences, who did not wish to be named, said there was no direct evidence to support the idea that the virus was engineered or leaked from a lab, although ‘the location of the acquired furin mutation is quite surprising’.

Another leading research scientist said a member of his team ‘went a bit pale when he looked at this’.

A paper earlier this year by Yong-Zhen Zhang, the Chinese diseases expert who published the first genome sequence for Sars-CoV-2, said this was ‘arguably the most important’ difference between the new virus and its closest known relative, which was derived from a bat by Wuhan researchers.

Simon Wain-Hobson, a virologist at the Pasteur Institute in Paris, said the ‘body of evidence’ suggested this was a natural virus. ‘You would see signatures if this was an engineered virus and I don’t see any evidence that it is engineered,’ he said.

Last week Chinese health officials confirmed they had ordered some labs to destroy samples of the coronavirus to ensure work was not being carried out in units that did not meet global biosafety rules.

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