Llama antibodies bind to coronavirus and stop the infection of cells

July, 3, 2020. Antibodies are proteins produced by the immune system to specifically bind pathogens. Once the cells of these pathogens are covered with antibodies, they can no longer bind to host cells to infect them. The coronavirus (SARS-CoV-2) needs a receptor on the human cell to infect it.

In order to deny the virus access to this receptor, research is being done to block the binding of the virus. Fortunately, we sometimes get some help from other animals, in this case the llama.

Special small antibodies

Animals within the family of camelids (Camelidae) such as camels, dromedaries, llamas, and alpacas have an unusual immune system. One of the features is that they make different types of antibodies than most mammals. Our antibodies consist of several protein parts that are linked together, while the camelids use much less of these parts. This makes their antibodies a lot smaller, which gives them different properties. The part of the antibody that binds to the pathogen is even a single part, that can be effective all on its own. These binding parts are so small that they can be produced separately in the lab, for example in yeast. We call these super small defenders nanobodies. An advantage of these nanobodies is that they can be administered in interesting ways, such as nebulized in an inhaler or nasal spray. This is a convenient way of administering antibodies when fighting respiratory infections such as the coronavirus . Now, instead of first encountering nose or lung cells, the virus first encounters a layer of antibodies.

Belgian llama

A group of Belgian scientists from the University of Ghent together with a group from the University of Texas at Austin set out to try and find one of these llama antibodies against the coronavirus. However, the true hero of this story is a four-year-old Belgian llama named Winter. Winter was already vaccinated against two other coronaviruses in 2016, the MERS virus (MERS-CoV) and the SARS virus (SARS-CoV-1). This yielded antibodies capable of inhibiting binding of the SARS virus to cultured cells. Because Winter's immune system had produced effective antibodies against two coronaviruses, and the current virus is very similar to SARS-CoV-1, he quickly came into view to play a role in the corona pandemic as well.

Linked antibodies

Because the vaccination program and the production of antibodies is a rather slow process, the researchers decided to first test the previously obtained antibodies against SARS and MERS on the new coronavirus. These antibodies had some effect on the binding capacity of the virus but were not yet very effective. Therefore, the researchers decided to link two antibodies together. This turned out to be a smart move, as the newly coupled antibodies prevented the virus from binding to cultured cells. A great result, thanks to Winter’s blood and a fair bit of hard lab-work. Future research will now have to show whether the antibodies can also inhibit or prevent an infection in practice. If this is successful, the next step might be to make nanobodies that have the same properties. Who knows, soon we might be inhaling antibodies from a llama produced in a yeast.