Antibodies found in llamas could prove to be useful in the treatment of COVID-19, an international team of scientists has said.
The researchers have engineered a new antibody, a type of protein produced by animal immune systems that defends against foreign invaders, which binds tightly to a key protein on the novel coronavirus SARS-CoV-2, according to a study accepted for publication in the journal Cell.
The team, led by Jason McLellan from the Department of Molecular Biosciences at The University of Texas at Austin (UTA,) created the novel antibody by linking together two copies of a special kind of antibody found in llamas.
Coronaviruses are covered in distinctive “spikes,” special proteins that enable the virus to break into host cells. In initial laboratory experiments, the scientists found that the novel antibody was effective in stopping a “pseudotyped” version of the SARS-CoV-2 virus from infecting cells in a culture.
This pseudotyped virus is a virus particle that has been engineered to display copies of the SARS-CoV-2 spike protein on its surface.
“This is one of the first antibodies known to neutralize SARS-CoV-2,” McLellan said in a statement.
The inspiration for the latest study came from tests conducted on a 4-year-old llama named “Winter” that is currently living on a farm in the Belgian countryside.
In 2016, before the pandemic began, the researchers were conducting research into two other coronaviruses, SARS-CoV-1 and MERS-CoV, which cause the diseases severe acute respiratory syndrome coronavirus (SARS) and Middle East respiratory syndrome (MERS) respectively.
During this research, the team injected Winter with pseudotyped versions of both SARS-CoV-1 and MERS-CoV over a period of six weeks, inducing an immune response in the llama’s body.
Llamas and other camelids, such as alpacas, produce a special kind of antibody known collectively as “single-domain” antibodies. After taking blood samples from Winter, the team, found that one of these single-domain antibodies, known as VHH-72, bound tightly to the spike proteins on SARS-CoV-1 and prevented it from infecting cells in a culture.
“That was exciting to me because I’d been working on this for years,” Daniel Wrapp, a co-first-author of the paper from UTA, said in the statement. “But there wasn’t a big need for a coronavirus treatment then. This was just basic research. Now, this can potentially have some translational implications, too.”
Stock image: Two llamas looking directly at the camera.
After the outbreak of the COVID-19 pandemic, the team wondered whether VHH-72 would also be effective against SARS-CoV-2. Initial tests revealed that it did bind to the spike proteins of the virus, however, only weakly.
As a result, the scientists joined together two copies of the antibody, in an attempt to help it bind more effectively to the SARS-CoV-2 spikes. According to the team, the newly engineered antibody is the first known to neutralize both SARS-CoV-1 and SARS-CoV-2.
The next step, the researchers say, is to conduct studies in animals in order to further assess the impact of these antibodies on SARS-CoV-2. Eventually, they hope to be able to develop a treatment based on these antibodies that could be administered soon after infection.
“With antibody therapies, you’re directly giving somebody the protective antibodies and so, immediately after treatment, they should be protected. The antibodies could also be used to treat somebody who is already sick to lessen the severity of the disease,” McLellan said.
Nevertheless, it is important to note that this approach is still at a very early stage of development and must be tested extensively in animals and humans before it can be established whether or not it will be effective in the treatment of COVID-19.