Synthetic Nanobodies Prevent SARS-CoV-2 Infection

Team of researchers University of California San Francisco Can create a powerful nasal spray or inhaler to provide a high degree of protection against the severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The report is currently bioRvix*Preprint server.

Amid the pandemic of coronavirus disease 2019 (COVID-19), which has killed more than 751,000 people worldwide, UCSF researchers have been able to significantly block the entry of viruses into human cells. We have developed an aerosol formulation. The researchers named the formulation “AeroNabs.”

UCSF researchers believed that finding a nanobody that interferes with the interaction of spikes with ACE2 would prevent the virus from infecting cells. Photo by Noah Berger

Thoughts behind the study

This study was inspired by immune mediators like antibodies called nanobodies found in camels such as llamas and camels. Nanobodies function much like antibodies in the human immune system, but are significantly smaller in size and less structurally complex than antibodies. Due to these unique features, Nanobodies are extremely stable in nature and can be easily modified in the lab. This makes them potential candidates for biotechnology-based research.

Identification of powerful nanobodies

Researchers chose SARS-CoV-2 Spike protein As an important target for identifying candidate Nanobodies. The spike protein is located on the surface of the virus and contains three receptor binding domains (RBDs). The transition of the spike protein from the inactive closed state to the active open state activates RBD and interacts with angiotensin converting enzyme 2 (ACE2).

The RBD-ACE2 interaction is the key to SARS-CoV-2 entering human cells, infecting them and continuing their life cycle. To break the chain of infection, the researchers sought to identify Nanobodies that could actually block this interaction.

Using a yeast surface-displayed library containing more than two billion synthetic Nanobodies, researchers conducted rigorous research to identify the most potent and effective candidates for developing aerosol formulations. It was This identified 21 Nanobodies with the desired effects.

Study of effectiveness of Nanobody

To investigate the mechanism of action of Nanobodies, researchers conducted experiments using cryo-electron microscopy, in which candidate Nanobodies directly interact with the spike protein RBD, thereby inhibiting the RBD-ACE2 interaction. I observed.

To confirm Effectiveness of Nanobodies in the real world, virologist Veronica Rezi, a virologist at the Pasteur Institute in Paris, has experimented with the three most powerful nanobodies, and the SARS-CoV-2 in which these nanobodies live are human cells. It has been found to be extremely effective in preventing infection with. These Nanobodies showed powerful effects even at very low doses.

In addition, the researchers found that one of three strong candidates, Nanobodies, could bind to spike proteins even in an inactive conformation where RBD was in an inaccessible down state and could not interact with ACE2. .. This provides an additional level of protection against viral entry into human cells.

Researchers conducted a series of experiments on the concept of selecting this particular Nanobody to create a more potent antiviral formulation. First, we sequentially mutated every amino acid in the Nanobody involved in the binding of the spike protein, and identified two specific changes that increased the effectiveness of the Nanobody by a factor of 500. Next, we adopted a bioengineering approach to link the three Nanobodies to form a molecular chain. This Nanobody triplet was created with the concept that when one Nanobody binds only one spike protein RBD, the other two can bind the rest of the RBDs. In this way, reliable protection is guaranteed. As expected, researchers have observed that nanobody triplets are 200,000 times more effective than single nanobodies alone.

Development of “AeroNabs”

Finally, the researchers conducted a series of stress tests that included exposing the Nanobody triplets to high temperatures, converting them into dry powders, and aerosolizing (aerosol forming). Although these stress tests can cause significant damage to most compounds, the triplets of Nanobodies were successful in maintaining their antiviral effects in aerosolized form, and due to the unique properties of Nanobodies, various stresses were observed. It turned out to be stable enough to hold the element.

The results show that “AeroNabs,” which contains aerosolized Nanobodies, functions as a powerful antiviral formulation that can be easily administered via an inhaler or nasal spray. In a COVID-19 pandemic, where the entire scientific community is fully devoted to vaccine production, this aerosol-based formulation can offer strong protection against the deadly SARS-CoV-2 virus.

Due to the inherent stability of Nanobodies, there was no loss of antiviral efficacy in the aerosolized form. This suggests that AeroNabs is a potent SARS-CoV-2 antiviral drug that may be practical to administer via a shelf stable inhaler or nasal spray. Photo by Noah Berger

The research team is currently discussing with commercial partners to conduct human clinical trials and large-scale production of AeroNabs. If all goes well, the researchers believe that this preparation can be used as an effective preventive or early therapeutic intervention to prevent a pandemic. They also believe that “AeroNabs” could be an effective alternative for individuals who do not respond or have access to the SARS-CoV-2 vaccine.

*Important Notices

bioRxiv It publishes preliminary non-peer reviewed scientific reports and should not be considered conclusive and should not guide clinical practice/health-related behaviors or be treated as established information.