Scientist revives ‘lab-origin theory’, says old bat virus may be backbone
The natural origin theory was first reported by Nature Medicine in a paper on March 17, in which researchers said the virus had a 96% resemblance with a coronavirus found in bats, called the RaTG13.Updated: Sep 16, 2020 05:31 IST
The Sars-Cov-2 virus, which causes Covid-19, shows signs that are not usual for a naturally evolved pathogen, a group of researchers have contended, reigniting theories that the virus may have been developed in a lab – a notion that scientists and public health officials have rejected on several occasions.
The claim was made in a paper uploaded by Li-Meng Yan, who specialised in virology and immunology at the Hong Kong School of Public Health before she moved to the United States where she is believed to be seeking refuge.
“SARS-CoV-2 shows biological characteristics that are inconsistent with a naturally occurring, zoonotic virus. In this report, we describe the genomic, structural, medical, and literature evidence, which, when considered together, strongly contradicts the natural origin theory,” said the paper, which is yet to be peer-reviewed.
The natural origin theory was first reported by Nature Medicine in a paper on March 17, in which researchers said the virus had a 96% resemblance with a coronavirus found in bats, called the RaTG13.
Yan and her colleagues contend that there are growing doubts over the natural existence of this bat coronavirus, and that the Sars-Cov-2 instead has strong overlaps with two other bat coronaviruses: the ZC45 and ZXC211.
“The evidence shows that SARS-CoV-2 should be a laboratory product created by using bat coronaviruses ZC45 and/or ZXC21 as a template and/or backbone,” the report said.
The researchers add three hypotheses to support their contention that the virus could be a lab creation, calling it also “a demonstration of how SARS-CoV-2 could be conveniently created in a laboratory in a short period of time using available materials and well-documented techniques”.
The first of these, the researchers say, is history of coronaviruses ZC45 and ZXC21, both of which were discovered by military laboratories – one in the Third Military Medical University (Chongqing, China) and the other in Research Institute for Medicine of Nanjing Command (Nanjing, China).
The second has to do with a component of the virus known as the receptor-binding motif (RBM) within the spike protein, the portion of the virus that hooks onto a target cell. The RBM “resembles that of SARS-CoV from the 2003 epidemic in a suspicious manner. Genomic evidence suggests that the RBM has been genetically manipulated,” they said.
The third has to do with another feature of the spike protein called the furin cleavage, which, the team said has been established to “greatly enhance viral infectivity and cell tropism”. “This cleavage site is completely absent in this particular class of coronaviruses found in nature. In addition, rare codons associated with this additional sequence suggest the strong possibility that this furin-cleavage site is not the product of natural evolution and could have been inserted into the SARS-CoV-2 genome artificially by techniques other than simple serial passage or multi-strain recombination events inside co-infected tissue cultures or animals,” they said.
Scientists are yet to comment on these claims in a paper.
Yan, in an interview a British talk show earlier this week, alleged there was a cover-up of the virus’s origins. “I decided to report this development to my supervisor, who is also a World Health Organization (WHO) consultant. There was no response from the WHO and my supervisor. Everyone warned me that do not cross the right line and keep silence or else I would be made to disappear,” she said.