The United States and European countries have become the epicenter of the new crown epidemic.
It can be seen that the virus is
regardless of nationality. If you do not protect it properly, the virus will
ruthlessly plunder.
In addition to protection factors, recent studies have shown
that neocoronavirus may have more than one receptor. Receptors are highly
expressed in white people, which may cause white people to be more susceptible
to infection.
SARS coronavirus has three receptors, and so can new coronavirus
Recently, the Guoshuai Cai team at the University of South
Carolina posted a paper on the preprint website Preprint. The results of
this study suggest that smokers, the elderly, and white people may be more
susceptible to the new crown virus.
Based on 80% homology between the new crown virus and SARS
virus, and the two viruses have similar receptor domains, this suggests that
the new crown virus and SARS virus may enter human cells through a common
receptor.
Previous studies have shown that in addition to the ACE2
receptor, there are two other receptors that are involved in the entry of SARS
coronavirus into human cells, namely the DC-SIGN and L-SIGN receptors.
We already know very well that the new coronavirus can enter
our human cells through the ACE2 receptor, and little research has been done on
the other two receptors.
DC-SIGN and L-SIGN are homologous C-type lectin receptors,
capable of recognizing the carbon chain structure of viral glycoproteins, and
playing an important role in virus capture, anchoring of host cells and
large-scale reproduction in humans.
DC-SIGN is expressed on the surface of dendritic cells, and
L-SIGN is expressed on the endothelial cells of sinusoids and lymph nodes.
Previous studies have shown that DC-SIGN is an independent
receptor and can cooperate with the ACE2 receptor to endorse SARS coronavirus
into cells.
L-SIGN is also a potential receptor for SARS coronavirus and
a double-edged sword. After L-SIGN internalizes the virus, it degrades the
virus in a proteasome-dependent manner.
Smokers, older people, and whites may be more susceptible
The authors of the paper analyzed the expression of ACE2,
DC-SIGN and L-SIGN receptors in lung tissues of different populations using
information from known databases.
The analysis found that there was no significant difference
in expression of ACE-2 receptors between Caucasians and Asians. However, other
problems were found in the study.
ACE2 and DC-SIGN expression levels are higher in the lungs of
smokers, especially those who have smoked.
DC-SIGN has a higher expression level in the elderly
population over 60 years old, and the expression level has nothing to do with
gender.
In addition, the expression of L-SIGN gene in the lungs of
Caucasians (whites) was higher than that of Asians, suggesting that whites are
more susceptible to the new coronavirus.
The data from these laboratories have some agreement with
clinical data, and current research shows that smokers and the elderly have a
higher mortality rate after new coronary pneumonia infection.
Researchers speculate that upregulation of ACE2 in alveolar
cells in smokers may lead to increased susceptibility to new crown virus.
Dendritic cells are immune cells of our body. DC-SIGN of dendritic
cells is up-regulated, which makes it easier for viruses to enter host cells.
At the same time, smoking-activated dendritic cells and the activation of the
immune system may further lead to the occurrence of cytokine storms (immune
storms) in critically ill patients.
In the elderly over 60 years old, the expression of DC-SIGN
receptors increases, and the functions of organs and immune systems decrease.
On the basis of the susceptibility of new crown virus, it is also easy to
develop into severe diseases.
Based on these data, the authors concluded that elderly
people over 60 years, smokers (or people who have smoked), and white people are
more likely to be infected with the new crown virus, and the DC-SIGN of immune
cells is affected. Body upregulation is more likely to induce a cytokine storm.
What's wrong with this research?
The entire study has a small amount of data, and the lung
specimens are from lung cancer patients. It is not clear whether similar
conclusions can be drawn from normal healthy people.
The most important defect, the entire experiment was
speculated based on previous studies of SARS corona virus, and it can be
determined that the ACE2 receptor is the receptor of the new coronavirus.
Whether DC-SIGN and L-SIGN are truly receptors for new
coronaviruses, no data are available at this time.
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