LAB LEAK ORIGIN OF COVID VIRUS GAINS CREDIBILITY IN AUSTRALIA STUDY

A study conducted by Australian scientists led by Dr. Nikolai Petrovsky, an endocrinologist from Flinders University, and published by Nature Scientific Reports last month has provided more arguments for the lab leak theory on the origins of the COVID-19 virus, Alexander Nazaryan reported for Yahoo News.

The paper, “In silico comparison of SARS-CoV-2 spike protein-ACE2 binding affinities across species and implications for virus origin,” noted that the coronavirus could have emerged from a laboratory and argued COVID-19 was fairly well developed in attacking humans and need not have passed on from bats to pangolins before the virions improved their capacity to attach to human ACE2 receptor genes.

Using computer models, Petrovsky and his co-authors set out to learn which animal the virus may have originated from before infecting humans. Proponents of the zoonotic spillover hypothesis believed that the pathogen known as SARS-CoV-2 originated in bats and then made the leap to humans, possibly through an unknown intermediate species.

The Australians modeled how the distinctive spike protein that protrudes from the surface of the coronavirus binds to a receptor called ACE2, found on the membranes of human and animal cells. Essentially, the researchers’ computer model tried to calculate how tightly the key that was the SARS-CoV-2 spike protein would fit into the ACE2 keyhole of different species: monkeys, snakes, mice, bats and, of course, humans, along with many others. If the spike protein had trouble binding to the ACE2 receptors in a species, that species wasn’t likely to be the source of the coronavirus.

Petrovsky and his co-authors all but ruled out the notion of a direct zoonotic spillover from bats to humans, without an intermediate species involved, because the virus that was believed to have begun circulating in China in late 2019 had a low binding affinity to the bat ACE2 receptor.

There was still the possibility that the virus had jumped from bats to another species before infecting humans, but none of the candidates the Australians tried seemed an especially good fit for that role. One popular suspect had been the pangolin, a scaly relative of the anteater that is both eaten in China and used in traditional Chinese medicine.

It performed well in the Australians’ computer models, with the coronavirus predicted to have the second-highest binding affinity for pangolin ACE2, after that of humans. Only this was a false lead in the search for the intermediate species, because the pangolin coronavirus does not resemble SARS-CoV-2. Crucially, it lacks a key genetic signature of SARS-CoV-2 called a furin cleavage site.

Also, pangolins are rare and, contrary to reports from early 2020, are not traded in the wildlife markets of Wuhan. Last month, a joint research team from Chinese and Western institutions published a survey of 47,381 different individual animals, from 38 species, sold at Wuhan markets between May 2017 and November 2019. During that time, not a single pangolin or bat was sold in the entire city.

The Australians, however, in addition to ruling out a number of species as potential intermediaries, found that the coronavirus hadn’t seemed to need an intermediate species in order to proliferate through the human population. Studying genomic data of human virus isolates from the very earliest stages of the pandemic in China, they saw that the coronavirus was already well adapted to infect humans, even at a stage where it is not thought to have infected more than a few hundred people in Hubei province.

Such quick and efficient adaptation to humans meant the virus may “have arisen from a recombination event that occurred in a laboratory handling coronaviruses,” wrote the Australian group, which along with Petrovsky and Winkler included Sakshi Piplani and Puneet Kumar Singh.

One of the other laboratories, the Wuhan branch of the Chinese Center for Disease Prevention and Control, is about a 20-minute walk from the Huanan Seafood Wholesale Market, where initial investigations focused.

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