Tiny antibodies produced by llamas may be effective against COVID-19

As the fight against COVID-19 continues, scientists have turned to an unlikely source for a potentially effective treatment: tiny antibodies naturally generated by llamas.

While the world has welcomed the news of multiple vaccines against COVID-19, the search for effective treatments for those who get the virus is ongoing. Now scientists are looking at what might be a similar source: a South American llama.

Researchers are using Ultrabright X-rays of the Advanced Photon Source (APS), User Resource of the U.S. Department of Energy (DOE) at Argonne National Laboratory at DOE, to aid in the detection of llama antibodies naturally generated to be potentially effective therapies against SARS- CoV-2, the virus that causes COVID-19. Antibodies are natural defenses of the immune system against infections, and when removed from blood, they can be used to design medicines and vaccines.

Lalamas naturally generate these nanobodies in high yield, and they weave into the pockets on the surface of proteins that receive antibodies of larger size. “

Jason McLellan, University of Texas, Austin

“We have obtained over 50 llama antibodies with several proteins of SARS-CoV-2,” said Andrzej Joachimiak, director of the Center for Structural Biology (SBC) at the APS and co-director of the Center for Structural Genomics of Infectious Diseases . (Researchers at the APS will not work with the live virus, but with crystals grown from symbolic proteins.)

These antibodies are part of an ongoing collaboration with several partners, including researchers at the National Institutes of Health (NIH) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), Joachimiak said , and are tested using the APS to see if they fight off the virus infection.

While it may come as a surprise that scientists are turning to llamas, there is a good reason for it.

Lalamas belong to a group of mammals called camelids, a group that also includes camels and alpacas. Thanks to a quirk of nature, camelids produce a specific type of antibody against disease. These antibodies, often called nanobodies, are about half the size of the antibodies that humans make. They are also very durable and easy for scientists to handle.

This genetic burial, which causes camelids like llamas to produce these smaller antibodies with single protein chains, was discovered by accident in the late 1980s by scientists in Belgium. Since then, scientists have been working with camelid nanobodies to create cures against a number of diseases with great success. Their small size allows them to bind to areas of viral proteins that larger antibodies cannot absorb, preventing these proteins from binding to cells.

“Lalamas naturally generate these nanobodies in high yield, and they weave into the pockets on the surface of proteins that do not receive larger-sized antibodies,” said Jason McLellan, associate professor at the University of Texas at Austin.

McLellan has years of experience working with camelid nanobodies. He and his graduate student Daniel Wrapp, along with Xavier Saelens group in Belgium, on remote nanobodies that have been shown to be effective against respiratory syncytial virus (RSV) and two coronaviruses: severe respiratory syndrome (SARS) and respiratory syndrome Middle East (MERS).

When the genetic sequence of SARS-CoV-2 was released in January 2020, McLellan, Wrapp and Saelens quickly worked to test for any of the antibodies they had previously isolated. against the original SARS-CoV (taken from a Belgian llama called Winter) they could also bind and neutralize SARS-CoV-2.

They found that one of these nanobodies, which they identified as using SBC beamlines at the APS, may be effective against SARS-CoV-2. McLellan said this nanobody – known as VHH72 – is now being developed as a treatment for COVID-19. He and Wrapp received the Golden Goose 2020 Award for this research.

MacLellan will tell you that although his results were good, his hopes were slightly higher.

“We were looking for one strong antibody that neutralized all coronaviruses,” he said. “We put the vaccine in Winter hoping to get that same nanobody. And we may have found it, but we didn’t eliminate it.”

Separating these tiny nanobodies is difficult, since the body generates a large number of them and only a small fraction is expected to fight a particular virus. That is exactly the problem that Yi Shi, a professor of cell biology at the University of Pittsburgh, is trying to solve.

In a paper published in Science, Shi and his colleagues unveiled a new advanced large-scale spectroscopy method for analyzing these nanobodies from llama blood samples. The result, according to Shi and research assistant Yufei Xiang (the paper ‘s lead author), is a large set of nanobodies that bind well to the SARS-CoV-2 virus.

“This is thousands of times better than the conventional technology, especially in its select buildings,” Shi said. “We want nanobodies that bind tightly to SARS-CoV-2, and with this approach we get a drug-quality nanobody that is up to 10,000 times more powerful.”

Similar to McLellan’s research, Shi’s experiment began with a llama, this one named Wally because he resembles (and therefore shares a name with) his black Labrador. The Wally vaccine team challenged SARS-CoV-2, waited two months to generate nanobodies, and then Xiang used their new method to study, identify and quantify the nanobodies. They ended up with 10 million nanobody series.

These nanobodies can sit at room temperature for six weeks, and are small enough to be aerosolized, meaning that devices designed from them can be injected directly into the lungs. instead of moving through the bloodstream. To test the effectiveness of the nanobodies, Cheng Zhang, an assistant professor at the University of Pittsburgh, examined the structures of the nanobodies linked to the SARS-CoV-2 virus at the National Institute of General Medical Sciences and National Institute Structural Biology Facility. Cancer (GM / CA) at the APS.

“With this method we can discover thousands of unique, ultrahigh-affinity nanobodies for specific antigen binding,” Shi said. “These nanobodies may or may not provide treatment for COVID-19, but the technology used to differentiate them will be important in the future.”

Recently, a team of scientists led by the University of Bonn in Germany described recently discovered nanobodies that bind to SARS-CoV-2 and potentially inhibit what is known as “mutational escape.” That is the ability of a virus to avoid immune responses by inactivation, and there would be a treatment that would prevent the virus from protecting against recurrence.

This research team combined several nanobodies into molecules that attack different parts of the virus at the same time, helping to prevent virus mutations from reducing therapeutic efficacy. These nanobodies were extracted from llama and alpaca vaccinated against the SARS-CoV-2 virus, and out of several million candidates they ended up with four effective molecules.

Ian Wilson, professor of structural biology at the Scripps Research Institute in California, led the team that conducted GM / CA X-ray isolation studies at the APS to determine the structures of these molecules linked to the virus.

“From crystal structures tested from data collected at APS and Stanford Synchrotron Radiation Lightsource (SSRL), we were able to identify the binding sites of the nanobodies on the SARS-CoV-2 receptor binding domain,” Wilson said . “The X-ray structural information, along with cryo-electron microscopy data, was used to help design even more potent multivitamin antibodies to prevent COVID-19 infection. The X-ray structural work made it easier with immediate access to the APS. “

Only time (and further testing) will determine whether the different nanobodies translate into effective treatments against COVID-19. But if they do, we’ll have the lovable llama to thank for it.