An international research team led by the University of Bonn (Germany) has developed novel antibody fragments against the SARS-CoV-2 virus. They stated that these “nanobodies” are significantly smaller than the classic antibodies.
Due to their nano size, these nanobodies can dig deeper into the tissues and be produced easily in large quantities, the authors of the study noted.
The researchers combined the nanobodies into potentially particularly effective molecules. These attack different parts of the virus simultaneously. The approach could prevent the pathogen from evading the active agent through mutations.
Researchers across the world are experimenting with antibodies that have the potential to treat coronavirus. The outgoing United States President was treated using the same approach. He was injected with large quantities of antibodies that can fight the coronavirus infection.
However, the antibodies used to treat him have a complex structure. Hence, they could not penetrate deep into the tissue and lead to unwanted complications. Moreover, producing antibodies is difficult and time-consuming. They are therefore probably not suitable for widespread use.
“We focus on another group of molecules, the nanobodies. Nanobodies are antibody fragments that are so simple that they can be produced by bacteria or yeast, which is less expensive.”
Dr Florian Schmidt, Head of Emmy Noether group, Institute of Innate Immunity, University of Bonn
Schmidt explained: “We first injected a surface protein of the coronavirus into an alpaca and a llama. Their immune system then produces mainly antibodies directed against this virus. In addition to complex normal antibodies, llamas and alpacas also produce a simpler antibody variant that can serve as the basis for nanobodies.”
A few weeks later, the researchers took a blood sample from the animals, from which they extracted the genetic information of produced antibodies.
“Altogether we obtained dozens of nanobodies, which we then analyzed further,” said lead author Dr Paul-Albert König, head of the Core Facility Nanobodies at the Medical Faculty of the University of Bonn.
Four molecules proved to be effective against the pathogen in cell cultures. “Using X-ray structures and electron microscopy analyses, we were furthermore able to show how they interact with the spike protein of the virus,” König noted.
“Nanobodies also appear to trigger this structural change before the virus encounters its target cell – an unexpected and novel mode of action. The change is likely to be irreversible; the virus is therefore no longer able to bind to host cells and infect them,” König added.
The findings of the study are published in the journal Science.