Scientists have isolated a set of promising, tiny antibodies or nanobodies against the new coronavirus from the llama, some of which can prevent infection.
Preliminary results, published in the journal Scientific Reports, suggest that the nano body appears to work equally well in either liquid or aerosol form, suggesting that it could remain effective even after inhalation.
Researchers from the U.S. National Institutes of Health (NIH) said at least one of these nanobodies, called NIH-CoVnb-112, could prevent infections and detect virus particles by capturing the SARS-CoV-2 spike protein, which causes Covid- 19.
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“We hope that these anti-Covid-19 nanobodies could be very effective and versatile in fighting the coronavirus pandemic,” said David L. Brody, who is also a professor at the University of Uniform Services in Health Sciences.
Nanotelo is a special type of antibody that is naturally produced by the immune system of camels, a group of animals that includes camels, llamas and alpacas.
On average, these proteins are about a tenth the weight of most human antibodies, the researchers said.
This is because the nanobodies isolated in the lab are basically free-floating versions of the heavy chain protein arm tips, which form the backbone of a typical Y-shaped human IgG antibody, they said.
These tips play a critical role in defending the immune system by recognizing proteins on viruses, bacteria and other attackers, also known as antigens.
Because nanobodies are more stable, cheaper to produce, and easier to make than typical antibodies, an increasing number of researchers are using them for medical research.
Also read: New inhalable llama antibodies may help treat and prevent Covid-19: Study
Since the pandemic broke out, several researchers have produced llama nanobodies against the SARS-CoV-2 class of proteins that can be effective in preventing infections.
In the latest research, researchers used a slightly different strategy than others to find nanobodies that can work particularly well.
“SARS-CoV-2 protein acts like a key. It does so by opening the door to infections when it binds to a protein called the angiotensin 2 (ACE2) enzyme receptor, which is found on the surface of some cells,” he said. Thomas J Esparza, lead author of the study.
“We have developed a method that would isolate nanobodies that block infections by covering the teeth of protein classes that bind to and unlock the ACE2 receptor,” Esparza said.
The researchers immunized a llama called Cormac five times over 28 days with a purified version of the SARS-CoV-2 spike protein.
After testing hundreds of nanotels, they discovered that Cormac had produced 13 nanotels that could be strong candidates.
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Initial experiments suggested that one candidate, named NIH-CoVnb-112, could work very well, the researchers said.
In vitro studies have shown that this nanobody binds to the ACE2 receptor 2 to 10 times more strongly than nanobodies produced by other laboratories.
Other experiments suggest that the NIH nanobody adhered directly to the part that binds the ACE2 receptor protein class.
The team then demonstrated that the NIH-CoVnB-112 nanobody can be effective in preventing coronavirus infections.
To mimic the SARS-CoV-2 virus, the researchers genetically mutated the harmless “pseudovirus” so that it could use a protein class to infect cells that have human ACE2 receptors.
The researchers saw that the relatively low level of the NIH-CoVnb-112 nanobody prevents the pseudovirus from infecting these cells in Petri dishes.
They have shown that the nanobody is equally effective in preventing infections in Petri dishes when sprayed through a type of nebulizer or inhaler, often used to treat patients with asthma.