Super New Drug? U.S. Scientists Develop Anti-Coronavirus Sprays in Experiments

While the world is waiting for a vaccine to control the COVID-19 pandemic, scientists at the University of California, San Francisco have devised a new method to stop the spread of the SARS-CoV-2 virus that causes the disease.

Led by graduate student Michael Schoof at the University of California, San Francisco, a research team designed a fully synthetic, manufacturable molecule that can limit the key SARS-CoV-2 mechanism that allows the virus to infect our cells.

According to a new paper, experiments with live viruses have shown that this molecule is one of the most effective SARS-CoV-2 antiviral drugs discovered so far. The paper is now available on the preprint server bioRxiv.

In an aerosol that the researchers call 'AeroNabs', these molecules can be self-administered through a nasal spray or inhaler.

Used once a day, AeroNabs can provide strong and reliable protection against SARS-CoV-2 until a vaccine appears. The research team is actively discussing with business partners to strengthen the production and clinical testing of AeroNabs. If these tests are successful, the scientists’ goal is to make AeroNabs widely available as an inexpensive over-the-counter drug to prevent and treat COVID-19'.

'We believe that AeroNabs is a molecular form of personal protective equipment that can be used as an important stopgap measure. It is much more effective than wearable personal protective equipment until the new coronavirus vaccine provides a more durable solution.' AeroNabs Said Peter Walter, co-inventor, professor of biochemistry and biophysics at the University of California, San Francisco, and researcher at the Howard Hughes Medical Institute.

Walter also said that AeroNabs may be a longer-lasting line of defense against COVID-19 for those who cannot obtain or do not respond to the SARS-CoV-2 vaccine.

'We have assembled an incredible team of talented biochemists, cell biologists, virologists and structural biologists to make this project from start to finish in just a few months," Schoof said that he is a member of Walter Labs and a co-inventor of AeroNabs.

Although designed entirely in the laboratory, AeroNabs was inspired by nanobodies, which are antibody-like immune proteins naturally found in llamas, camels and related animals.

Since Nanobodies were discovered in a laboratory in Belgium in the late 1980s, the unique properties of Nanobodies have attracted the interest of scientists all over the world.

'Although they function much like antibodies in the human immune system, Nanobodies will provide some unique advantages in effective therapies against SARS-CoV-2," explained Aashish Manglik, MD and Assistant Professor of medicinal chemistry, who often Nanobodies are used as tools when studying the structure and function of proteins that send and receive signals through cell membranes.

For example, nanobodies are an order of magnitude smaller than human antibodies, which makes them easier to manipulate and modify in the laboratory. Their small size and relatively simple structure also make them much more stable than other mammalian antibodies.

In addition, unlike human antibodies, nanobodies can be easily and cheaply produced on a large scale : Scientists implant genes containing molecular blueprints into E. coli or yeast, and then convert these microorganisms into high-yield nanobody factories.

For decades, the same method has been safely used to produce insulin in large quantities.

But as Manglik pointed out, 'Nanobodies are just our starting point. Although they are attractive in themselves, we think they can be improved through protein engineering. This ultimately led to the development of AeroNabs.'

SARS-CoV-2 relies on its so-called S protein to infect cells. These S proteins protrude on the surface of the virus and present a coronal appearance when viewed under an electron microscope. So the virus family including SARS-CoV-2 is named 'coronavirus'.

However, S proteins are more than just a decoration, they are the key to getting viruses into our cells. Like a retractable tool, the S protein can switch from a closed inactive state to an open active state.

When any one of the about 25 S proteins of the virus particle is activated, the 3 'receptor binding domains' (RBDs) of this S protein will be exposed and ready to interact with ACE2 (a type in human lung and airway cells). Receptors found in) binding.

Through the lock key between the ACE2 receptor and the S protein RBD, the virus enters the cell and then transforms the new host into a new coronavirus producer.

Researchers believe that if they can find nanobodies that block the S protein-ACE2 interaction, they can prevent the virus from infecting cells. In order to find effective candidate materials, the scientists analyzed the recently developed library of more than 2 billion synthetic nano antibodies in the Manglik laboratory.

In successive rounds of testing, scientists have implemented increasingly stringent standards to eliminate weak or ineffective candidates. In the end, they obtained 21 Nanobodies, which can prevent a modified S protein from interacting with ACE2 interacts.

Further experiments, including the use of cryo-electron microscopy to observe the interface between the nanoparticles and the S protein, showed that the most effective nanoparticles blocked the interaction between the S protein and ace2 by strongly attaching themselves directly to the RBDs of the S protein.

These nanobodies function a bit like a sheath that covers the RBD 'key' and prevents it from being inserted into the ACE2 'lock'.

With these findings, researchers still need to prove that these Nanobodies can prevent real viruses from infecting cells. Dr. Veronica Rezelj, a virologist in the laboratory of Dr. Marco Vignuzzi of the Pasteur Institute in Paris, tested the three most promising Nanobodies against live SARS-CoV-2 and found that these Nanobodies are very effective, even at very low doses It can also prevent infection.
However, the most effective of these nanobodies is not only the sheath on the RBDs, but also like a molecular mousetrap that can suppress the S protein in a closed, inactive state, which adds an extra layer of protection against S protein. The interaction with ACE2 leads to infection.

Then, scientists used a variety of ways to transform this dual-acting nanobody into a more effective antiviral drug. In a set of experiments, they mutated every amino acid of the Nanobody in contact with the S protein to find two specific changes that increased the potency by 500 times.
In another set of experiments, they designed a molecular chain that can connect three Nanobodies together.

As mentioned above, each S protein has three RBDs, any of which can attach to ACE2, allowing the virus to enter the cell. The triple nanobody designed by the researchers can ensure that if one nanobody is attached to the RBD, the other two will also attach to the remaining RBD.
They found that this triple nanobody is 200,000 times more effective than a single nanobody.
Walter said that when they used the results of these two changes to connect three powerful mutant nanobodies together, the results were 'out of the chart'.

'It is very effective, beyond our ability to measure its effectiveness.'

The three-part nanobody of this super-superstructure forms the basis of AeroNabs.
In the last set of experiments, the researchers performed a series of stress tests on three-part nanobodies, exposed them to high temperatures, turned them into storage-resistant powders, and made aerosols.

Each process is extremely destructive to most proteins, but scientists have confirmed that due to the inherent stability of Nanobodies, the antiviral efficacy of aerosols has not decreased, indicating that AeroNabs is an effective SARS-CoV-2 Antiviral drugs can be actually used through storage-stable inhalers or nasal sprays.

'It's not just that we think AeroNabs is an amazing technology,' Manglik said.

'Our team is in discussions with potential business partners interested in manufacturing and selling AeroNabs, and we hope to start human trials soon.'

'If AeroNabs prove to be as effective as we expected, they may help reshape the course of the global pandemic.'

Reference

https://www.sciencedaily.com/releases/2020/08/200811234951.htm