A gene that helps the spread of the coronavirus among people, apparently, reduces the infectivity of the virus the same bat. To such conclusion came in the United States a new government study, which may cast doubt on the theory that the virus originated in a Chinese laboratory.
Virus raTG13 detected in the litter podkovonos bats in a cave in the southwest of China, is considered the closest relative of the new coronavirus genes with similarity of more than 96 percent. The biggest difference between them are the spikes or proteins that bind the virus with the host cell.
It tells the Hong Kong newspaper South China Morning Post, in the laboratory for control of vector-borne viral diseases Control on control of products and medicines USA (FDA) in Maryland Dr. Tony Wang and his colleagues conducted an experiment to find out what happens to raTG13, if they would give him a surge similar to the surge of coronavirus Sars-CoV-2, which causes the disease COVID-19.
Representatives of the US administration, including President Donald trump and Secretary of state Mike Pompeo, theorized that the outbreak COVID-19 could take its start in a laboratory in Wuhan, where scientists studied the virus bat raTG13.
Dr. Wang refused to comment on this theory, but said his work was focused on research that could only happen in a laboratory.
“In nature there is no evidence that there is a bat virus that contains the insertion of a PRRA”, – he told the South China Morning Post.
PRRA is an insertion of four amino acids in the genome of the coronavirus, which can cause small but significant changes in the structure spinovogo protein. With a new spike structure can easily be cleaved, and this can allow the viral shell more efficiently merge with the cell membrane of human.
Scientists have discovered similar structures in other very contagious pathogens such as human immunodeficiency virus (HIV), but not in the fashion industry.
Dr. van and his colleagues have created pseudovirus based on HIV, which contained spickovy protein of coronavirus bat with insert PRRA. Pseudovirus is a modified virus that can infect cells, but is safer to handle than a real virus, because it replicates only once.
Scientists from the FDA noted that the new spickovy protein splits easier, but it negatively affects the ability of pseudovirus to penetrate the host cell. The researchers tested it on cells from different potential hosts, including a bat and pangolin, and the results were the same.
For example, in cells of human lungs, the infectivity decreased in hundreds times in comparison with cells bearing natural spikes of the virus to the bat, they said in their presenteranno article published on Tuesday biorxiv.org. These results were “surprising,” scientists say.
The origin of the coronavirus Sars-CoV-2 still remains a mystery. Although research scientists from around the world gave a lot of evidence against the conspiracy theory that the strain was created by man, remains a question – who was the intermediate host of the virus.
The wide genetic gap suggests that the coronavirus might have been separated from their relatives at bats, including raTG13, years or even decades ago, but what happened between this and the current global pandemic, remains the missing link.
Study FDA found a clue that may help to bring the response to the step. Of the animals on which it was tested, insert PRRA could increase the ability of the bat virus to infect cells only in mice. This opened the possibility that the mouse could be an intermediate host, but many studies, including the FDA, found that human coronavirus, despite the fact that it is able to infect many animals, can infect mice.
Researchers in the US have not yet found an explanation for these seemingly contradictory results, but agreed with the consensus in the global research community that the virus could have existed long before, as was discovered in China at the end of December. “Sars-CoV-2 could adapt to humans before the outbreak in Wuhan, China”, – the document says.