Unusually small antibodies found in the blood of llamas are the inspiration behind one of the latest weapons against Covid-19. Scientists have identified a synthetic mini-antibody that is capable of blocking SARS-CoV-2, the virus that causes Covid-19, from binding to human cells and invading tissues.
The synthetic mini-antibodies are based on a unique type of small antibody called nanobodies that can be found in the blood of Camelids, the family of animals that includes camels, llamas, alpacas, and vicuñas. Nanobodies are around one-tenth of the size of a conventional antibody found in other mammals and have proved to be a promising agent against viruses thanks to their size and versatility. Most interestingly, research from earlier this year also showed that nanobodies from a llama are capable of binding to SARS-CoV-2, halting the virus from invading a cell.
Fortunately, scientists don’t always have to drain these nanobodies straight out of the llama’s blood, with new technology allowing researchers to select synthetic nanobodies, called sybodies, with relative ease. In a new study, reported in Nature Communications, researchers from the European Molecular Biology Laboratory Hamburg in Germany sifted through a recently developed library of sybodies and attempted to pinpoint those that target the spike protein of SARS-CoV-2.
One of the sybodies — called Sb23 — was found to show notable promise. Using a technique to detail nanoscale objects called small-angle X-ray scattering, they observed how Sb23 interacts with the receptor-binding domains of viruses. They tested out how Sb23 performed against a virus that had been modified to carry the SARS-CoV-2 spike protein on its surface, the key the virus uses to enter a host cell. Crucially, Sb23 successfully deactivated the modified virus in vitro.
Of course, deactivating a modified virus in a petri dish is a very different task to conquering a SARS-CoV-2 infection in the human body. However, the researchers achieved this research in just under three weeks thanks to their synthetic nanobody library. This new study, they believe, highlights that big steps in the research of nanobodies can now be achieved in a relatively short space of time, helping to pave the way towards developing more nanobody-based drugs against diseases, not least including Covid-19.
“This methodology is an attempt to minimize the overwhelming impact that SARS-CoV-2 is having on the healthcare systems and to prepare for future pandemics. Thus, the R&D community can act in a prompter way for the development of efficient medication,” the researchers conclude in their paper.
“Here we demonstrate that it is possible to select highly specific binders with neutralizing activity against SARS-CoV-2 from a synthetic nanobody library in a timeframe of only 2–3 weeks. The traditional generation of nanobodies requires at least 6 weeks for the Llama immunization and a total of 3-4 months for the entire selection approach.”