Several studies have already identified some of the causes responsible for the extreme virulence and infectivity of the current novel coronavirus. However, one piece of the puzzle was still missing. A piece that may have just been discovered.
Neuropilin 1, a transmembrane protein that gives viruses the ability to bind to cells, could be one of the factors responsible for the infectivity of the coronavirus in 2019.
Seventeen years ago, the SARS-CoV virus was first identified by researchers. It appeared in 2002 in Guangdong Province in southern China, affected 26 countries, and peaked the following year with 8,000 cases. Fortunately, it was quickly contained, and today sporadic outbreaks rarely occur mainly due to laboratory incidents or – possibly – naturally through transmission from animals to humans. The pandemic feared by researchers never happened, therefore. Until the end of last year, when a new form of the virus, SARS-CoV-2, appeared.
A more infectious virus
Unlike its predecessor, the 2019 coronavirus is particularly infectious, as evidenced by the 41.7 million cases registered worldwide, and virulent, since 1.142 million deaths have already been registered. The agents causing this development have been partially identified with the discovery of the Angiotensin-converting enzyme II (ACE2), which is believed to act as a receptor, gateway, and entry point of the coronavirus in the human body. However, this receptor, which is also compatible with the previous SARS-CoV virus, did not explain everything.
“The starting point of our study was to find out why SARS-CoV, a coronavirus that led to a much smaller outbreak in 2003, and SARS-CoV-2 spread so differently when using the same main ACE2 receptor,” explains Ravi Ojha, a virologist, and co-author of a study that may contain a new piece of the puzzle published in Science magazine. The researchers found the answer in the SARS-Cov-2 genome.
The genome study identified the sequences responsible for creating a network on the surface of the virus that can help it connect to tissue. “Unlike its old progenitor, the new coronavirus had acquired an ‘extra piece’ in its surface proteins, which are also found in many other devastating human viruses, including Ebola, HIV and highly pathogenic strains of avian flu, among others,” comments Olli Vapalahti, also a virologist. The culprit behind these dangerous hooks is the transmembrane protein neuropilin 1.
The use of monoclonal antibodies against pseudoviruses has confirmed that blocking neuropilin 1 makes it considerably more difficult to penetrate the cells. If we imagine ACE2 as the door lock to enter the cell, then neuropilin 1 may be the one that guides the virus to the door,” says co-author Giuseppe Balistreri. ACE2 is expressed in very small amounts in most cells. Therefore, it is not easy for the virus to find doors into which it can enter. Other factors such as neuropilin 1 can help the virus find its door. »