2023-10-26 10:30:28
Nearly 4 years following the start of an unprecedented global health crisis, the coronavirus continues to make headlines. Researchers are trying to unravel all the mysteries of this virus, to better combat it. A new discovery was published today in the scientific journal Nature on the entry receptors of another coronavirus, the HKU1 virus. Explanations.
Seven coronaviruses capable of infecting humans
SARS-CoV2 is known throughout the world for his role in the Covid-19 pandemic. But this virus is not the only member of the coronavirus or Coronaviridae family. Among viruses, coronaviruses constitute a huge family of viruses, present in our daily environment. Studies carried out on coronaviruses have shown that at least 7 of them are capable of infecting humans, including the famous SARS-CoV2.
Among the coronaviruses capable of infecting humans, researchers distinguish two categories, the weakly pathogenic (with four representatives known to date, including the HKU1 virus) and highly pathogenic :
- Le SARS-CoV2, responsible for Covid-19;
- The SARS virus, severe acute respiratory syndrome;
- MERS-CoV, the Middle East respiratory syndrome virus.
Coronaviruses are the subject of intense research around the world to better understand how these viruses enter human cells and spread throughout the body.
What is the entry point for coronaviruses?
In this context, French researchers are studying how different coronaviruses enter human cells to infect them. Knowledge of these mechanisms is decisive for developing new preventive and therapeutic solutions. Recently, these researchers made an interesting discovery regarding the HKU1 coronavirus. This coronavirus is one of four low-pathogenic coronaviruses known to infect humans. It was first identified in 2005 in Hong Kong in an elderly person suffering from severe pneumonia.
The coronavirus HKU1 usually causes an upper respiratory tract infection: colds and other mild respiratory symptoms. More rarely, it can infect the bronchi and pulmonary alveoli, particularly in young children, the elderly and fragile subjects. This virus is very widespread and epidemiological studies estimate that 70% of children have been in contact with the HKU1 virus before the age of 6. Thus, a large majority of the world’s population has already encountered the HKU1 virus, like other low-pathogenic seasonal coronaviruses.
A different infection mechanism of SARS-CoV2
Like SARS-CoV2, the HKU1 virus is surrounded by an envelope containing, among other things, a Spike protein (the one targeted to develop vaccines once morest Covid-19). For the virus to infect cells, this protein must be split into its two subunits. In the case of SARS-CoV2, one of the subunits binds to a receptor on human cells, the other allows the fusion of viral and cellular membranes and the entry of the viral genome into the cell. For SARS-CoV2, the cellular receptor that serves as the gateway is the ACE2 receptor, but until now the HKU1 virus receptor was not known.
Using different techniques in vitro and in cell culture, French researchers have identified the cellular receptor for coronavirus HKU1, the enzyme TMPRSS2. This receptor has a strong affinity for the Spike protein of the HKU1 virus, but not for that of the SARS-CoV2 virus. In addition, the TMPRSS2 receptor plays a dual role: not only does it bind to the HKU1 virus, but it also triggers fusion with the virus and infection of the cell. The identification of the HKU1 coronavirus cellular receptor marks a new step in understanding the mechanisms used by coronaviruses to infect human cells. The presence of these receptors along the respiratory tree and their mode of action following binding to the Spike protein might explain why some coronaviruses are highly pathogenic, while others only cause common colds.
Estelle B., Doctor of Pharmacy
Sources
– New discovery on coronavirus entry receptors in human cells. Press release October 23, 2023.
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