How Llamas Wally and Winter Are Helping Scientists Find Effective COVID-19 Treatments

Llamas naturally generate antibodies smaller than humans – and easy for scientists to manipulate. Antibodies from llamas named Winter (center, looking to the left) and Wally are now used in the fight against COVID-19. Credit: Photo by Tim Coppens

X-rays from Argonne’s Advanced Photon Source turn llama antibodies into potential therapies.

While the world has welcomed the news of multiple COVID-19 vaccines, effective treatments are being sought for those who contract the virus. Now scientists are looking at what seems like an unlikely source: the South American llama.

Researchers are using the ultra-bright X-rays from the Advanced Photon Source, an accelerator at Argonne National Laboratory, to convert naturally generated llama antibodies into potentially effective therapies against COVID-19.

“We have received more than 50 llama antibodies with different proteins from SARS-CoV-2,” said University of Chicago professor and senior Argonne scientist Andrzej Joachimiak, director of the Structural Biology Center at the Advanced Photon Source and co-director of the centre. for structural genomics of infectious diseases.

These antibodies are part of ongoing collaborations with several partners, including researchers from the National Institutes of Health and the National Institute of Arthritis and Musculoskeletal and Skin Diseases, Joachimiak said, and will be analyzed to see if they fight the virus’s infectivity. .

The Advanced Photon Source is a powerful X-ray synchrotron at Argonne National Laboratory. Credit: Argonne National Laboratory

Camelids cures

While it may seem surprising that scientists are turning to llamas, there is very good reason for it.

Llamas belong to a group of mammals called camelids, a group that also includes camels and alpacas. Thanks to a peculiarity of nature, camelids produce a unique type of antibody against disease. These antibodies, often referred to as nanobodies, are about half the size of the antibodies produced by humans. They are also remarkably stable and easy to manipulate by scientists.

This genetic quirk, which causes camelids such as llamas to produce not only heavier antibodies with multiple protein chains, but these smaller ones with single protein chains, was accidentally discovered by scientists in Belgium in the late 1980s. Since then, scientists have worked with camelid nano bodies to develop treatments for a variety of diseases with great success.

“Llamas naturally generate these nanobodies in high yields, and they fit into the pockets on the surface of proteins that cannot be accessed by larger antibodies,” said Jason McLellan, associate professor at the University of Texas at Austin.

McLellan has years of experience working with camel-like nanobodies. He and his graduate student Daniel Wrapp, together with Xavier Saelens’ group in Belgium, have isolated nanobodies that have been shown to be effective against respiratory syncytial virus and two coronaviruses: severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).

When the genetic sequence of SARS-CoV-2 was released in January 2020, McLellan, Wrapp and Saelens worked quickly to test whether any of the antibodies they had previously isolated against the original SARS-CoV (from a Belgian llama named Winter ) can also bind and neutralize the virus. They found that one of these nanobodies, which they had characterized using the Structural Biology Center beamlines at the Advanced Photon Source, may be effective against SARS-CoV-2. McLellan said this nanobody – dubbed VHH72 – is now in development as a treatment for COVID-19. In 2020, he and Wrapp received a Golden Goose Prize for this research.

McLellan will tell you that while his results were good, his expectations were somewhat higher.

“We were looking for a powerful antibody that would neutralize all coronaviruses,” he said. ‘We immunized Winter in the hope of eliciting that one nanobody. And we may have provoked it, but we have not isolated it. “

Isolating these small nanobodies is difficult, as the body makes a huge amount of them and only a small part is intended to fight a particular virus. That’s exactly the problem Yi Shi, a professor of cell biology at the University of Pittsburgh, is trying to solve.

Assists from Wally and Winter

In a paper published in Science, Shi and his colleagues unveiled a new advanced mass spectroscopy method to extract those nanobodies from samples of llama blood. According to Shi and research assistant Yufei Xiang, the paper’s lead author, the result is a large array of nanobodies that bind well to the SARS-CoV-2 virus.

Wally, named after scientist Yi Shi’s black Labrador. Credit: Photo courtesy of the University of Pittsburgh

“This is thousands of times better than current technology, especially in terms of property selection,” said Shi. “We want nanobodies that bind tightly to SARS-CoV-2, and with this method we can get a drug-grade nanobody that is up to 10,000 times more powerful.”

As with McLellan’s research, Shi’s experiment began with a llama named Wally because he resembles (and therefore shares a name with) his black Labrador. The team immunized Wally against SARS-CoV-2 and waited two months for nanobodies to be generated, then Xiang used their new method to analyze, identify and quantify the nanobodies. They ended with 10 million nanobody sequences.

These nanobodies can remain at room temperature for six weeks and are so small that they can be nebulized, meaning they can be inhaled directly into the lungs instead of moving through the bloodstream.

To confirm the effectiveness of the nanobodies, Cheng Zhang, assistant professor at the University of Pittsburgh, determined structures of the nanobodies bound to the SARS-CoV-2 virus at the National Institute of General Medical Sciences and the National Cancer Institute Structural Biology Facility at the Advanced Photon Source.

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

Only time will tell whether the nanobodies will translate into effective treatments against COVID-19.

Recently, a team of scientists led from the University of Bonn in Germany reported newly discovered nanobodies that bind to SARS-CoV-2 and may prevent them from being called “mutational escape.” That’s the ability of a virus to avoid immune responses by mutating, and a treatment that prevents the virus from doing this would protect against reinfection.

This research team combined several nanobodies into molecules that attack different parts of the virus simultaneously to help prevent virus mutations from diminishing therapeutic effectiveness. These nanobodies came from a llama and an alpaca immunized against the SARS-CoV-2 virus, and from the millions of candidates, they were given four molecules that proved to be effective.

Ian Wilson, professor of structural biology at the Scripps Research Institute in California, led the team that conducted X-ray diffraction studies at GM / CA at the Advanced Photon Source to determine the structures of these molecules bound to the virus. (Researchers at the APS are not working with the living virus, but with crystals grown from simulated proteins.)

“From crystal structures determined from data collected at APS and the Stanford Synchrotron Radiation Lightsource, we were able to identify the binding sites of the nanobodies on the SARS-CoV-2 receptor binding domain,” said Wilson. “The structural X-ray information, combined with cryo-electron microscopy data, was used to design even more powerful multivalent antibodies to prevent COVID-19 infection. The X-ray structural work was greatly facilitated by immediate access to the advanced photon source. “

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

The Advanced Photon Source is a US Department of Energy Office of Science user facility operated by Argonne National Laboratory. Additional funding for bundle lines used for COVID-19 research at the APS is provided by the National Institutes of Health (NIH) and by the DOE Office of Science Biological and Environmental Research. The APS worked 10 percent more hours than usual in 2020 to support COVID-19 research, with the additional time supported by the DOE Office of Science through the National Virtual Biotechnology Laboratory, a consortium of national DOE laboratories focused on response to COVID -19 with funding provided by the Coronavirus CARES Act.