A new study claims to have found a molecular signature that would reveal a laboratory origin for SARS-CoV-2, the virus that causes the Covid pandemic-19. The authors first found out what kind of mark a virus from the coronavirus family would have on its genetic material when manipulated in the laboratory. They later found that the novel coronavirus of the pandemic bears the mark and concluded from this that it “is an anomaly, more likely a product of synthetic genome assembly rather than natural evolution.”
The genetic material of viruses, like ours, is a long molecule (called DNA or RNA) that stores information in the sequence of its building blocks called nucleotides. In order to change genetic information, such as that which makes the virus more or less infectious in humans, it is necessary to change the order of the sequence of these blocks, which are of four types. For years, one of the most used techniques to do this type of genetic engineering in viruses is based on enzymes, which are smaller molecules capable of initiating or accelerating chemical reactions. Specifically, restriction enzymes are used, originating from bacteria.
Restriction enzymes are like scissors that cut the genetic material, but only at specific places called restriction sites, short sequences of nucleotides in a palindrome (a palindrome is a word or phrase read the same way in reverse, such as “egg” and “the grass is bitter” — nucleotides are represented with the letters ATCG). In short, restriction sites are cut-off points. With the cuts, scientists can remove or insert nucleotide sequences to alter the virus.
The molecular clue
There are more than 07 years ago virologists use restriction enzymes, along with other techniques, to assemble the genome (complete genetic material) of coronaviruses. In the case of these viruses, the genetic material has about 30 a thousand nucleotides linked together. It is broken down with the enzymes into five to eight pieces, each with less than 8,000 of these blocks. For assembly, the scientists modify the restriction sites, which are different from those normally found in wild coronaviruses. In addition to modifying, they can insert or remove sites. This is the laboratory manipulation mark that the authors found in the novel Covid-19 coronavirus-19.
The study authors calculated what random distributions of cutoffs exist in viruses not modified in the laboratory, and the size of the fragments of genetic material that would leave if treated with specific types of restriction enzyme. They also observed how the cuts and the size of the pieces are in viruses already manipulated in the laboratory and related to the pandemic virus, such as a virus that causes Middle East respiratory syndrome (MERS) modified according to the criteria described in an article by 2013.
The sites modified by the scientists occur at more regular intervals than the wild ones, to facilitate the assembly work. These clipping intervals delimit patches that are shorter than expected in nature. The Covid virus has as its largest fragment after enzymatic treatment a stretch with 25% of the total extension of its genome. Under the same treatment, wild viruses typically have as their largest fragment the equivalent of 43% of their genome. The probability of finding a wild coronavirus with the same pattern as SARS-CoV-2 is only 1%. Taking into account other types of enzymes and their cut-off points, this probability is reduced to 0,07%.
In addition to having these patterns, SARS-CoV-2 does not have “inconvenient” cutoffs for searching in the same places that its closest relatives have, a sign that they have been removed. In the analysis of mutations (changes in nucleotides) involving the two most closely related viruses known, one of which only exists in a database of the Wuhan Institute of Virology, the authors show that the new coronavirus has a pattern that is also very unlikely to have emerged from purely natural way. The institute claims that this related virus was extracted from bat feces and that the sample has run out.
Not the only molecular clue
As Gazeta do Povo reported in a pioneering way (and still lonely in Brazil) in November
, there is another sign of laboratory modification of SARS-CoV-2: the suspected presence of a molecular structure called the “furin cleavage site”, whose artificial insertion into viruses is known in the scientific literature, and which is absent in the closest relatives of the virus found in nature, such as the one mentioned above (in addition to the relative extracted from feces), found in Laos.
An NGO acted as an intermediary for research funds between the US government and the Wuhan Institute of Virology, located in the Chinese city where the first Covid outbreak occurred 19. Documents revealed that the president of this NGO asked for money from Darpa, a defense research promotion agency, to insert furin cleavage site in laboratory coronaviruses. The grant was denied.
The new study relies on indirect clues that have not yet been subjected to peer review. The authors are Valentin Bruttel, from the University of Clinics, Würzburg, Germany; Alex Washburne, from the US biotechnology company Selva Analytics; and Antonius VanDongen, from Duke University, in the United States.