Cell Research: The membrane fusion ability of the new coronavirus is superior

The global pandemic of new coronary pneumonia confirms the superior transmission of the new coronavirus (SARS-CoV-2). At present, scientists have found some explanations for the high lysofability of new coronary pneumonia from molecular levels and patientclinical performance. For example, the team at the University of Texas at Austin found that the affinity between angiotensin-conversion enzyme 2 (ACE2) and the new coronavirus was 10 to 20 times that of the SARS virus;

This is not the whole means of the new corona virus.

Today, the Fudan University School of Basic Medicine, Shanghai Public Health Clinical Center Land and Jiang Shibo team, together with the Chinese Academy of Sciences Biophysics Sun Fei and Zhu Wei team, as well as the Chinese Academy of Sciences Wuhan Virus Institute Shi Zhengli team, in the well-known journal “Cell Research” officially published important research results.

For the first time, they analyzed the crystal structure of the core domain of the new coronavirus protrusion protein (S) membrane, and found that there were several key amino acid variations compared to this part of the SARS virus, which resulted in the membrane fusion capacity of the new coronavirus being much stronger than that of the SARS virus. In other words, new coronaviruses enter cells more efficiently than SARS.

What’s more, they’ve also developed a lipopeptide drug that can effectively block membrane fusion caused by neo-coronaviruses, and can even be used to prevent viral infections by nasal administration.

Cell Research: The membrane fusion ability of the new coronavirus is superior

The cover of the paper

The new coronavirus, like its close relatives, relies on the S protein to identify and invade cells. The S protein is divided into Two sub-bases, S1 and S2, where s1’s receptor binding domain (RBD) is responsible for identifying ACE2 on the surface of human cells, completing the binding of the virus to the cell, and then the S2 subunit is responsible for completing the fusion of the virus envelope with the human cell membrane to complete the invasion process.

As we all know, there have been so many recent research on the combination of RBD and ACE2, and we’ve basically been very clear about how they fit together. But little is known about the fusion of neo-coronaviruses with cell membranes.

In fact, similar to other coronaviruses, there are two important conservative repeat amino acid sequences in the S2 sub-base of the new coronavirus: HR1 and HR2. The two of them will entangle together to form a spiral structure called 6-HB. Recent studies have shown that this 6-HB is the key to the fusion of the new coronavirus envelope with the cell membrane.

Cell Research: The membrane fusion ability of the new coronavirus is superior

New Coronavirus (Photo: NIAID-RML)

So is there any difference between 6-HB 6-HB of the new coronavirus and 6-HB of coronaviruses such as SARS? Is this membrane fusion process can also find the new coronavirus infection ability of the reason?

That’s the problem the research team is going to solve.

Their first step was to study the membrane fusion capabilities of the neo-coronavirus-mediated membrane. First let the live new coronavirus infect the cells directly. They saw a lot of conthiscinal presence in cultured cells.

What is a conjoined cell? It’s not a bag of eggs. It is a phenomenon in which infected cells merge with similar cells around them and form polynuclear macrocells.

Why is this so? Because, after the virus envelope merges with the cell membrane, those fusion proteins on the surface of the virus envelope remain on the cell membrane surface. In this way, under the guidance of the fusion protein, the cells merge and form a conjoined cell.

Cell Research: The membrane fusion ability of the new coronavirus is superior

Virus infection-mediated conjugations (photo source: viralzone.expasy.org)

In order to further explore the membrane fusion characteristics of the new coronavirus S protein. The researchers simply cloned the S-protein of the new coronavirus and integrated it into a cell line. In other words, the cell, which carries the S protein, has the membrane fusion capability of the new coronavirus. As a result, a cell-cell fusion system is built.

After cultivating cells that express S proteins and cells that express ACE2 under appropriate conditions for a period of time, the researchers found that if the S protein was a new coronavirus, it would appear to form conjoined cells;

Obviously, compared with SARS virus, the new coronavirus mediated membrane fusion capacity is stronger, and the efficiency of entering cells will be higher. And S-protein and ACE2 are necessary for new coronavirus fusion and entry into the virus.

Cell Research: The membrane fusion ability of the new coronavirus is superior

Study on the intersocytome of virus infection

Why is the membrane fusion ability of the new coronavirus stronger than SARS?

After comparing the amino acid sequences of HR1 and HR2 of the two S2 sub-s, it was found that the HR1 homologousness of the two was 92.6%, and the homologousness of HR2 was 100%. Specifically, HR1 has eight amino acids, which have the potential to enhance the interaction between HR1 and HR2 of the new coronavirus and stabilize the spatial structure of 6-HB.

At the same time, the researchers analyzed the X-ray crystal structure of 6-HB and the effect of THE DIFFERENCE in HR1 amino acids on 6-HB. The specific analysis process we will not repeat here, need to know the details of the friends themselves click on the end of the text “read the original text.”

Overall, the eight amino acid substitutions in the new coronavirus HR1 can enhance the interaction between the HR1 and HR2 domains to further stabilize the 6-HB structure, which may indeed lead to increased infection capacity of the new coronavirus.

Cell Research: The membrane fusion ability of the new coronavirus is superior

The difference between the new coronavirus and SARS virus HR1 and HR2, as well as the difference between the complex

Since the fusion skills of the S protein are also the key to the new coronavirus infection, it is a matter of course to use it as a target for drug development.

In fact, the previous land and Jiang Shibo team has developed a peptide drug EK1, which inhibits the fusion of human coronavirus membranes, and has initially confirmed that EK1 has some inhibition effect on membrane fusion mediated by the new coronavirus.

But now it seems that the problem is not so simple, the membrane fusion protein of the new coronavirus is very “hard”, EK1 also has to upgrade.

Fortunately, previous studies have shown that lipidization strategies can effectively improve the antiviral activity of fusion inhibitors. In that case, add some “oil” to EK1.

The researchers used polyglycol (PEG) to combine cholesterol (Chol) or palmitic acid (Palm) to the C end of EK1, and then began to optimize continuously, eventually getting an EK1C4 linked to cholesterol.

How powerful is this lipopeptide EK1C4? As a membrane fusion inhibitor for new coronavirus-infected cells, the IC50 of EK1C4 is 36.5nM, which is 67 times higher than EK1. Not only that, EK1C4 has a broad-spectrum effect on other people’s coronaviruses.

Cell Research: The membrane fusion ability of the new coronavirus is superior

The difference between 6-HB and SARS virus

At the end of the study, the researchers considered a very important issue: the new coronavirus is transmitted in people through respiratory infections. So is it possible for this EK1C4 to block this process and thus prevent infection?

Since there were no model mice suitable for the new coronavirus infection, the researchers did the study using another human coronavirus, HCoV-OC43.

They infected mice with HCoV-OC43 and then explored the potential for EK1C4 to prevent coronavirus infection through nasal administration.

The first was inthe nasal administration of 0.5 hours, 2 hours, 4 hours, 12 hours and 24 hours before infecting mice with HCoV-OC43. After 4 days of infection, all the mice in the control group died, while the survival rates of the mice given at different points in time were 100%, 100%, 100%, 83% and 0%, respectively. This indicates that EK1C4 has a preventive effect on HCoV-OC43 infection.

Subsequently, a study of 0.5 hours and 2 hours of nasal administration after HCoV-OC43 infection was conducted, with survival rates of 100% and 16.7% in both groups, respectively. This shows that EK1C4 is given as soon as possible after HCoV-OC43 infection, which has good therapeutic effect.

This phenomenon may be caused by HCoV-OC43 infecting the brains of mice quickly, but EK1C4 nasal administration fails to pass through the blood-brain barrier. Because the new coronavirus mainly infects the lungs, it is predicted that EK1C4 nasal administration has good prevention and treatment effect on the new coronavirus infection.

Cell Research: The membrane fusion ability of the new coronavirus is superior

Highly pathogenic viruses that have emerged in the last 100 years

At the end of the paper, the researchers concluded the advantages of EK1C4 over current nonspecific antiviral drugs.

First, the HIGHly conservative sequence of THE EK1C4-targeted HR1, they analyzed the recently published 103 new coronavirus genomes, both 1 hr and HR2 are homogenous at 100%. Therefore, the new coronavirus is not easy to develop resistance to EK1C4.

Second, EK1C4 may be able to prevent coronavirus infection by nasal administration. Therefore, it is easy to bring people who are in close contact with infected patients or high-risk groups.

Third, patients inhale EK1C4, or reduce the viral load of their lungs, thereby reducing acute lung damage caused by viral infections and reducing the chance of transmission of the virus to close contacts.

Fourth, since EK1C4 is a local administration, it is relatively safe, and peptide drugs are generally safer than chemicals.

Fifth, EK1C4 has broad-spectrum anti-coronavirus activity, so it is possible not only to treat and prevent new coronavirus infection, but also for other human coronavirus infection.

It has to be said that the results of this study are indeed very attractive. We are looking forward to the research team conducting relevant clinical studies and obtaining positive results in 2020, when we do not know where the new coronary pneumonia is going.

Come on.