In a new study, researchers found antibodies derived from llamas have been shown to neutralize the SARS-CoV-2 virus in lab tests.
They hope the antibodies – known as nanobodies due to their small size – could eventually be developed as a treatment for patients with severe COVID-19.
The research was conducted by a team from Oxford University and elsewhere.
Llamas, camels, and alpacas naturally produce quantities of small antibodies with a simpler structure, that can be turned into nanobodies.
The team engineered their new nanobodies using a collection of antibodies taken from llama blood cells.
They have shown that the nanobodies bind tightly to the spike protein of the SARS-CoV-2 virus, blocking it from entering human cells and stopping infection.
Using advanced imaging with X-rays and electrons, the team also identified that the nanobodies bind to the spike protein in a new and different way to other antibodies already discovered.
There is currently no cure or vaccine for COVID-19. However, transfusion of critically ill patients with serum from convalescing individuals, which contain human antibodies against the virus, has been shown to greatly improve clinical outcomes.
This process, known as passive immunization, has been used for over 100 years, but it is not straightforward to identify the right individuals with the right antibodies and to give such a blood product safely.
A lab-based product that can be made on-demand would have considerable advantages and could be used earlier in the disease where it is likely to be more effective.
The team says these nanobodies have the potential to be used in a similar way to convalescent serum, effectively stopping the progression of the virus in patients who are ill.
They were able to combine one of the nanobodies with a human antibody and show the combination was even more powerful than either alone.
Combinations are particularly useful since the virus has to change multiple things at the same time to escape; this is very hard for the virus to do.
The nanobodies also have potential as a powerful diagnostic.
The team started from a lab-based library of llama antibodies. They are now screening antibodies from Fifi, one of the ‘Franklin llamas’ based at the University of Reading, taken after she was immunized with harmless purified virus proteins.
One author of the study is Professor James Naismith, Director of The Rosalind Franklin Institute and Professor of Structural Biology at Oxford University.
The study is published in Nature Structural & Molecular Biology.
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