How do you find out how a virus that is invisible to the naked eye gets into the body, which cells attack it first and why? And in the shortest possible time, because life could depend on a lot of people.
A team of a good dozen researchers decided on an elegant genetic engineering method. It constructed a green fluorescent variant of the new corona virus and was able to observe in experiments that Sars-CoV-2 primarily infected the nasal mucosa before it affected the throat and finally the lungs.
Much more doors to the cells in the nasal mucosa
And the researchers also immediately found out what the reason is: Apparently the viruses prefer certain “cilia-carrying” cells in the nasal mucosa, because they have a particularly high concentration of the ACE2 receptor in the cell membrane, which the viruses use as a gateway into the cells use. The research team led by Yixuan Hou, Richard Boucher and Ralph Baric from the University of North Carolina at Chapel Hill is now reporting in the journal “Cell”.
[Das Coronavirus benutzt den Menschen, um sich zu vermehren. Diese visuelle Reise zeigt, wie das funktioniert – und warum es krank macht.]
After multiplication in the cilia cells, the viruses apparently end up in small droplets of mucus that are transported to the throat and deeper regions of the lungs when inhaled. There they also infect the cells there, even though they have less ACE2 in the cell membrane, the researchers say. This is in agreement with the course of the disease observed so far, according to which the upper and lower organs of respiration are initially infected and produce high viral loads.
To get the results, Hous Team used different “elegant” methods, according to the director of infectious diseases at Regensburg University Hospital, Bernd Salzberger, to get the results. On the one hand, it inserted the blueprint for the green fluorescent protein (GFP) into the virus genome.
This protein is then produced together with the other virus components in the infected cell. If these cells are irradiated with light of a certain wavelength, GFP glows greenish – making the virus indirectly visible. The researchers were able to observe in which of the many different airway tissues – from the nose to the throat and the bronchi down to the alveoli – the viruses prefer to dock: the nasal mucosa.
This fits in with the discovery that certain cells in this mucous membrane, the cilia cells equipped with cilia, offer the virus a particularly large number of entry points: a high concentration of ACE2 receptors. The team observed this with a second, very precise detection method for ACE2 production.
[Moreonthesubject:[MehrzumThema:What You Should Know About the Drosten Study Debate – Top Questions and Answers]
This suggests that Sars-CoV-2’s nasal mucosa is more easily infected than other airway tissues. At least that is “more plausible than a direct infection of the bronchial mucosa,” says Salzberger. “However, this does not and cannot be concluded that a direct infection of the lungs does not also occur.”
“The path of the virus is definitely via the respiratory tract”
Wolfgang Kummer from the Institute of Anatomy and Cell Biology at the University of Gießen is somewhat more cautious about the work. Although it is “important for the specialized world”, it is not evidence of an infection that begins in the nose and slowly spreads with the inhalation air into the alveoli.
There are still some inconsistencies – as you would not expect from such rapid research into the novel virus – says Kummer. Not all of the research results of the research group agree with the thesis that the amount of ACE2 receptors decreases continuously from the nasal mucosa down to the alveoli.
[Alle aktuellen Entwicklungen in Folge der Coronavirus-Pandemie finden Sie hier in unserem Newsblog. Über die Entwicklungen speziell in Berlin halten wir Sie an dieser Stelle auf dem Laufenden.]
And according to another study, published in the same journal “Cell”, it is not the cilia-bearing cells in the nasal mucosa but the mucus-producing cells that have the highest amount of ACE2 in the cell membrane. There must be reworked.
Incidentally, the result of the study does not change the previous recommendations on how to prevent a Sars-CoV-2 infection, says Salzberger, that is, about distance and wearing protective masks. “The path of the virus is in any case via the respiratory tract.” But perhaps the new knowledge that the nasal mucosa is the preferred target of the virus will rethink all those people who prefer to wear their protective mask under the nose on the subway or bus . (with smc)
–
