Viruses need to attach to cells to infect them, and they do this by binding to specific receptors on the cell. If a virus can’t attach, it can’t infect. Some receptors are very specific to an individual animal species, while some are more general. These differences in receptor binding explain why some viruses only infect one species (or cell type) while others can infect more. Therefore, understanding how a virus attaches to cells can help us figure out what types of cells and what species it can infect.
A newly published study in the Journal of Virology investigated this concept for the COVID-19 virus, based on knowledge obtained from the related SARS virus (Wan et al. Receptor recognition by novel coronavirus from Wuhan: an analysis based on decade-long structural studies of SARS. J Virol 2020). They looked a specific viral protein (spike protein) of the COVID-19 virus, and the cell receptor (angiotensin converting enzyme 2 (ACE2)) that SARS uses as its binding site to invade cells. Their analysis “confidently predicts” that the COVID-19 virus also uses ACE2 as its receptor. They also predict that a single genetic mutation at one location in the virus’ genome could significantly enhance its ability to bind, and that surveillance for this mutation should be performed.
There’s also an animal side here, in the vein of what I’ve been talking about for a while. This study predicts that the COVID-19 virus can bind to ACE2 in pigs, ferret, cats and some non-human primates with similar efficiency as it does in people.
That’s why I’ve been pushing to make sure infected or quarantined individuals are kept away from animals, and that investigation of their contacts and exposures includes animals. The potential susceptibility of cats is obviously a concern given their commonness as pets and the close interaction many people have with their cats. Pigs could be an even worse issue. If pigs could be infected and shed the virus, and it got into the commercial pig population, it would potentially be an even worse issue. As with SARS, mice and rats are likely resistant to infection – that’s good from the standpoint of them not being reservoirs in the wild, but it also means they can’t be used for experimental study (as these are the most common lab animal species).
I assume there will be lots more to come about this virus and how it works.