Scientists have isolated a number of promising, tiny antibodies or nanobodies against the novel coronavirus from a llama, some of which may help prevent infection. Preliminary results, published in the journal Scientific Reports, suggest that the nanobody appears to work equally well in liquid or aerosol form, suggesting that it might remain effective after inhalation.
Researchers at the National Institutes of Health (NIH) in the US said at least one of these nanobodies, called NIH-CoVnb-112, could prevent infection and detect virus particles by grabbing the spike proteins from SARS-CoV-2 . what causes COVID-19.
“We hope these anti-COVID-19 nanobodies will be highly effective and versatile in fighting the coronavirus pandemic,” said David L. Brody, who is also a professor at Uniformed Services University of Health Sciences.
A nanobody is a special type of antibody that is naturally produced by the immune system of camelids, 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 lab-isolated nanobodies are essentially free-floating versions of the arms of the tips of heavy chain proteins that form the backbone of a typical Y-shaped human IgG antibody.
These tips play a vital role in the immune system’s defense by detecting proteins on viruses, bacteria, and other invaders, also known as antigens.
Because nanobodies are more stable, cheaper to manufacture, and easier to engineer than typical antibodies, a growing number of researchers have used them for medical research.
Since the outbreak of the pandemic, several researchers have made llama nanobodies against the SARS-CoV-2 spike protein, which may be effective in preventing infection.
In the most recent study, the researchers used a slightly different strategy than others to find nanobodies that might work particularly well.
“The SARS-CoV-2 spike protein acts like a key. It opens the door to infection when it binds to a protein called the angiotensin converting enzyme-2 (ACE2) receptor and acts on the Surface of some cells is located, “he said Thomas J Esparza, lead author of the study.
“We developed a method to isolate nanobodies that block infection by covering the teeth of the spike protein that binds to and unlocks the ACE2 receptor,” Esparza said.
The researchers immunized a llama named Cormac five times over 28 days with a purified version of the SARS-CoV-2 spike protein.
After testing hundreds of nanobodies, they found that Cormac produced 13 nanobodies that could be strong candidates.
Initial experiments indicated that a candidate named NIH-CoVnb-112 could work very well, the researchers said.
Test-tube studies showed that this nanobody was two to ten times more strongly bound to the ACE2 receptor than nanobodies made by other laboratories.
Other experiments indicated that the NIH nanobody adhered directly to the ACE2 receptor binding part of the spike protein.
The team then showed that the NIH-CoVnB-112 nanobody can effectively prevent coronavirus infections.
To mimic the SARS-CoV-2 virus, the researchers genetically mutated a harmless “pseudovirus” so that it could use the spike protein to infect cells with human ACE2 receptors.
The researchers saw that relatively low levels of the NIH CoVnb-112 nanobodies prevented the pseudovirus from infecting these cells in Petri dishes.
They showed that the nanobody was equally effective in preventing infections in Petri dishes when sprayed through a nebulizer or inhaler, which is often used to treat asthma patients.
ALSO READ | Immunity induced by the COVID-19 vaccine is intended to protect against new variants: Moderna