Are llama antibodies going to be the key to finding a COVID-19 treatment?
A research team have isolated single-domain antibodies called VHHs from a llama affectionately known as Winter.
If there’s one quest every research institute and healthcare system in the world is currently occupied with, it’s to find the most appropriate and effective treatment and vaccine for COVID-19. The new coronavirus infection has infected millions across the globe and put billions of people at risk. If a recently published study is to be believed, the key to this treatment may lie with a llama with the right antibodies.
For those who don’t know, a llama is a domesticated camelid found and extensively used for transportation and agriculture in South America. A research team consisting of members from the University of Texas, the National Institutes of Health and Belgium’s Ghent University have isolated single-domain antibodies called VHHs from a llama affectionately known as Winter.
How llama antibodies might block COVID-19
Winter was immunized by the research team with prefusion-stabilised coronavirus spike or S proteins. Most coronaviruses use these spike proteins to bind to a patient’s cell receptors and spread to the rest of the body from there. The single-domain antibodies from four-year-old Winter were then observed to block viruses that contain these S proteins, including the SARS-CoV-2 virus which is currently wreaking havoc all over the world.
Also known as nanobodies, single-domain antibodies are antigen-binding fragments of the variable region of the heavy chain antibodies. In humans, an antibody molecule is made of two heavy chain and two light chain polypeptides (chains of amino acids). Both these chains have a fixed region (which does not change) and a variable region (which changes to fit the specific antigen). It is the variable region which has the antigen-binding fragment. Antigens are foreign substances against which our body mounts an immune response.
VHH antibodies are the single-domain antibodies present in camels and camelids like llamas. These nanobodies can also be isolated from cartilaginous fish, like VNAR from sharks, and are more useful than conventional antibodies as they are soluble, small in size and are more stable in various conditions.
What this study means in the long run
While these initial results look promising, the team is now going to begin preclinical trials on hamsters and primates, and then hopes to start human trials if these preclinical trials yield good results. They aim to create an antibody therapy which, unlike a vaccine, can be administered to patients who have already been infected and can lessen the severity of the disease as well as help quicken the recovery process.
The study also suggests that the single-domain antibodies isolated from llamas can also be used as reagents by researchers studying other viruses that cause diseases like MERS and SARS, and not just COVID-19. Reagents - often used interchangeably with reactants - are compounds that can cause a chemical reaction or can be used to check if a reaction occurs at all. In the context of COVID-19, reagents include inorganic solutions as well as enzymes, probes and primers which are used in testing kits as well as therapies. It is suspected that the world will face a shortage of reagents due to the pandemic, which - if these trials are successful - can be somewhat met with.
The research team’s current findings are available in the journal Cell as a pre-proof yet peer-reviewed paper.
For more information, read our article on Llama antibodies may bring us closer to a treatment for COVID-19.
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