Was the Covid-19 virus created in the laboratory?-Remains a mystery

 How did the cleavage site of furin in the covid-19 virus S-protein come about?

(Disclaimer: -

The following preliminary scientific reports have not been extensively reviewed and, therefore, should not be considered conclusive or behavioral guidance or established information related to medical practice/health.)

Called by SARS-CoV-2 (2019-nCoV and HCoV-191), this new novel virus belongs to the rapid spread, of the genus of B betacoronavirus (CoV). It has now caused a global outbreak of coronavirus disease (COVID-19).

It is speculated that a unique furin cleavage site (FCS) in S- (spike) protein that is not present in other hereditary B βCOVs such as SARS-CoV, may be responsible for its high infectivity and proliferation. Is this site natural? Or artificial?

A coronavirus (CoV) infects the target cell through cytoplasmic or endosomal membrane fusion. Whichever path it chooses, the final step in virus entry involves releasing RNA into the cytoplasm for replication. Therefore, the fusion capacity of CoV-S is a leading indicator of the infectious potential of the Covid-19 related virus.

S (Spike) - The protein consists of the S1 receptor-binding subunit and the S2 fusion subunit. CoV-S must be primed by cleavage at the S1 / S2 site and S2 ′ site, in order for it to open the cell by inducing the furin protease enzyme in the human cell.

There is no report yet to prove this hypothesis experimentally.

Corona virus-2 (SARS-CoV-2), which causes the acute respiratory syndrome of the current coronavirus infection 2019 (COVID-19), contains a mysterious new addition of four amino acids (PRRA) unique across the S1 / S2 border. FCS is a genetic mutation that does not normally occur between spike protein (S) in any SARS-CoV and other related coronaviruses.

That is the FCS genetic interpolation of the furin cleavage site. It is not present between the spike protein (S) in any normal SARS-CoV and other related coronaviruses.

Before getting into these issues first let us know some basics in some basic molecular biology.

What is Protease?: -

Our body is made up of many cells. Many devices are located within those cells. They are essential for the growth of cells. Notable among these are protease-type enzymes.

Of these, the furin protease enzyme is the most important. This is the cell key. Nutrients from the blood use these keys to open the cells and go inside the cell and help in cell growth. Some viruses also use this key to infiltrate cells and destroy them.

They must have a system called Furin Cleavage Site (FCS) in their spike (S) protein to use this key stealthily. It is not present in natural coronaviruses. But how this new system got into this novel coronavirus-2, is a mystery.

In nature, there are four types of corona: alpha, beta, gamma, and delta (∝,β,γ,d). NCoV-SARS-2 is a novel coronavirus that is a mutant or strain of the beta type.

This site does not cite its precursors such as the NCoV-SARS mutant which caused the deadly SARS-1 disease in China. So that disease did not spread fast everywhere. Stopped with China. But how it got into the NCoV-2 strain that could have made this Covid-19 remains a mystery.

This research led to the discovery that furin protease may play a key role in facilitating the entry of SARS-CoV-2 into human cells.

Pathogenesis of the virus caused by furin

The role of furin in the dysfunction of pathogens was first identified by biochemical tests of anthrax toxin antigen (PA) and avian influenza virus hemagglutinin (HA).

This means that the furin cleavage site (FCS) can only be found for fast-spreading deadly viruses. But how it got into the Covid-19 virus alone remains a mystery when it does not exist among other natural coronaviruses, which cause a mild form of normal infection.

Following the anthrax infection, for example, the furuncle inside the cell is responsible for the cleavage of this toxin, which allows the toxin to penetrate into the cells, and the FCS in the virus, the furuncle site of FCS itself, is an important device that allows holes to form in the target cell membranes and eventually penetrate into the host (human) cells.

The cleavage of these glycoproteins, which are caused by furin, allows mature and fusogenic cells to form glycoproteins. Ebola Zire and Ivory Coast virus strains are found to have a consensual furin base in their cell envelope glycoprotein, which is similarly related to some cytotoxic activity of the highly dangerous Ebola virus.

Furin and coronaviruses

The structure of the SARS-CoV-2 virus is surrounded by trimeric (three-step) intramembrane spike (S) proteins, which have been shown to be important in the mechanism by which the virus penetrates human cells.

Within S protein there are two functional domains, one of which is the receptor-binding domain and the second is the power domain, which enables the second domain to ignite the receptor-binding domain (part) to attach to the phospholipid membrane of the viral host (human) cells.

A specific type of protease enzyme is usually involved in the fusion of viruses and cell membranes; however, the specific properties of this protease may differ between coronaviruses. For example, the S protein surrounding the Middle East Respiratory Syndrome (MERS) -Cov virus contains the cleavage site of furin, which promotes the virus' entry into cells.

In comparison, the S protein of the acute respiratory syndrome (SARS) -Cov virus molecule does not divide after attachment to a human cell, thus indicating that its division occurs after the virus has already entered the cell.

Furin and SARS-CoV-2

The binding of the S protein to the angiotensin-converting enzyme 2 (ACE2) has been confirmed as an important mechanism for the penetration of SARS-CoV-2 into human cells.

Studies on the S protein of SARS-CoV-2 have identified four unwanted furin cleavage sites in that.

Interestingly, furin protease enzymes are found in large quantities throughout the human respiratory tract, leading researchers to question whether SARS-CoV-S protein S can use its cleavage sites to rapidly divide epithelial cells in the human respiratory tract and cause more infection and pathogenesis.

The discovery of the furin cleavage sites also provides researchers with information on why SARS-CoV-2 is highly contagious in humans and how the virus was first transmitted from bats to humans.

A recent study developed a strain of SARS-CoV-2 that does not have the cleavage site of conventional furin. From their series of tests, they found that the strain was less contagious and could provide some further protection against the original SARS-CoV-2.

Finally, findings suggest that the cleavage site of furin in SARS-CoV-2 may play a key role in SARS-CoV-2 infection.

FURIN CLEAVAGE SITE-FCS: -

By this strain, the old SARS-1 virus spike glycoprotein has a furin cleavage site (FCS) attached with a new look. Furin is a serine protein that is widely expressed in human cells, splitting the SARS-CoV-2 spike at the interface of its two subunits. It is encoded in a gene on chromosome 15 in the nucleus of human cells.

Furin acts on substrates containing single or paired base residues when proteins are added to cells. The cleavage site of polybasic furosemide, which opens cells with the protease key of furin, is not commonly found in various proteins of many viruses, including beta coronavirus, Embecovirus, and Merbecovirus.

However, it is doubtful whether this site was uniquely, innovatively, or artificially inserted into the SARS-CoV-2 strain or strain of the Sarbecovirus lineage beta coronavirus.

The study was conducted using genetic data available at the National Center for Biotechnological Information (NCBI) databases to identify the origin of the furin split site.

What is Furin?

First identified in 1990, furin is a cellular cell enzyme. It is the key to the entry of many pro-protein molecules into the cell, from pathogens to growth factors, receptors, and matrix proteins that must enter the cell from the inside.

Like other endoproteases, the mechanism of action of furin is the hydrolysis of specific internal peptide bonds, peptides, and protein substrates called enzymatic hydrolysis (ENZYMATIC HYDROLYSIS).

The actions of furin play important roles in every stage of life, starting with the activation of pro-B-neuro growth factor (NGF) and allowing neurodevelopment during development and continuing into late life during amyloid dementia.

The ancestor of the same virus

At the genetic level, they identified three coronaviruses that are very similar to SARS-CoV-2. These are Pangolin-CoVs (2017, 2019), Bat-SARS-like (CoVZC45, CoVZXC21), and Bat RaTG13.

Three gene fingerprints were used to identify these matches, including the fingerprint 1, nsp2, and nsp3 genes in the orf1a RNA polymerase gene; The fingerprint 2, at the beginning of the S gene, contains the N-terminal domain and the receptor-binding domain (RBD), which mediates binding to the host cell receptor, the angiotensin-converting enzyme 2 (ACE2); And fingerprint 3, the orf8 gene.

These fingerprints differ only in the RNA level of the three closely related coronaviruses, but in the amino acids in the translated proteins, the sequences are similar to those of other surface viruses.

The division of these gene sequences indicates their common lineage, supported by other short sequence features, one deletion, and three insertions. All three strains show the same removal-insertion pattern at the same four different locations in the spike gene.

Spike genetic remodeling in a common ancestor

Analysis of the phylogeny of these three strains showed that the first difference was the pangolin coronavirus, with which the RatG13 virus was most closely related. However, when analyzing spike alone, there is a strong resemblance between pangolin CoV, RaTG13, and SARS-CoV-2.

This may indicate the occurrence of recombination events between Pangolin-CoV (2017) and RatG13 ancestors. Following this pangolin CoV was transferred to pangolin hosts.

Unique codons that encrypt arginine at the furin cleavage site

The furin cleavage site consists of four amino acids PRRA, which are encoded by 12 inserted nucleotides in the S gene. A characteristic feature of this site is an Arginine Doublet.

This insertion may have occurred by random insertion mutation, reconstruction, or laboratory insertion. The researchers say that the possibility of random insertion is very small to explain the origin of this nucleus.

Surprisingly, the CGGCGG codons that encode the two arginines of the twin in SARS-CoV-2 are not found in any of the furin sites in other viral proteins that are exposed by the virus.

Even in SARS-CoV-2, arginine is encoded by six codons, but only a minority of arginine residues are encoded by the CGG codon. Again, only two of the 42 arginines in the SARS-CoV-2 spike are encoded by this codon - which is the PRRA core.

For the restoration to occur, there must be a donor from another furin site and another virus. In the absence of a known virus containing this arginine duplicate coded by CGGCGG codons, researchers dismiss the reconstruction theory as the underlying mechanism for the emergence of PRRA in SARS-CoV-2.

Acquisition time

The second question is when this change occurred. It should be noted that the RaTG13 virus was isolated and isolated in the laboratory in 2013, after which the site was acquired, which may have paved the way for the current SARS-CoV-2 strain.

The first scenario is demonstrated by the detection of identical RBD mutations in bats and human viruses, obtained from two of the three O-linked glycans around the furin base. The two viruses show completely identical scenes around this site.

However, to add strength to this hypothesis, there is no significant evidence. RaTG13 sequences obtained in 2021 should be analyzed to determine if the furin site is derived from this virus, as well as the source of SARS-CoV-2 in the bat.

Conclusion

Researchers briefly describe this mysterious site as "a Furin site that changed the world":

These sources and analyses only show that the acquisition of the Polyphasic Furin Cleavage-site by SARS-CoV-2 is a "missing link" in our understanding of its evolutionary history, which can only be resolved by the discovery of new viruses.