Nature Structural & Molecular Biology on July 13, 2020.
The research team hopes the antibodies, called nanobodies because of their very small size, could eventually be developed into a treatment for people suffering from severe Covid-19, reports
Llamas, camels, and alpacas are members of the
biological family Camelidae, or more commonly called camelids. They all naturally produce quantities of small antibodies with a simpler structure, that can be turned into nanobodies.
Unlike other antibodies,
camelid antibodies lack a light chain and are composed of two identical heavy chains. Because of this unique structure, these antibodies have been researched for use in a number of scientific and therapeutic fields – such as in vivo cellular imaging and antibody therapeutics in cancer therapy.
The team started out by engineering their new nanobodies from a lab-based library, but antibodies from a live llama, Fifi, are being used for screening now. Fifi is one of the “Franklin llamas” based at the University of Reading, who has been immunized with harmless purified virus proteins, according to the
Interestingly, Fifi’s immune system has produced different antibodies from those already identified. However, this will enable the researchers to develop a “cocktail of nanobodies” to be tested against the virus.
There is no cure or vaccine for COVID-19. But critically ill patients have been given transfusions of serum from convalesced individuals, which contain human antibodies against the virus. This has been shown to greatly improve clinical outcomes. This type of therapy is called
passive immunization and has been used for over 100 years.
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. This is exactly what the researchers are hoping to accomplish.
Professor James Naismith, Director of The Rosalind Franklin Institute and Professor of Structural Biology at Oxford University said: “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. We 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.”