A new path used by the Sars-Cov-2 virus to enter the human cell has been discovered, in addition to the one already known from the Ace2 receptor: it is the sialic acid receptor, present in the tissues of the upper respiratory tract and used for the same purpose also by the virus Once entered, to replicate it uses different proteins including some in common with the HIV virus. Two studies by the Italian Institute of Technology on Arxiv indicate this. The discovery opens up new hypotheses about its contagiousness and possible drugs to use. The Sapienza University of Rome has collaborated in the studies, which have not yet passed the scrutiny of the scientific community.
"We have developed a new predictive model to understand how proteins on the surface of the virus interact with human receptors," explains Giancarlo Ruocco, director of the IIT center in Rome. Here the researchers analyzed the interactions of the Spike protein, with which the virus locks on the Ace2 receptor (the same one targeted by sartan and anti-hypertensive drugs), and compared its ability to remain linked to it. Surprisingly, this ability was much lower than that of the Sars virus.
Hence the idea of looking for a second receptor involved. "We have thus discovered that to enter the cell - continues Ruocco - the Sars-Cov-2 virus also uses sialic acid, present in the upper respiratory tract and also used by the coronavirus responsible for MERS". Now we will have to understand if the different mortality and infectivity of Covid-19 can depend on these two ways of entry. "This could clarify - he notes - why there are so many asymptomatic cases, but this is only a hypothesis that needs to be confirmed, as well as the results of the study".
The other research, coordinated by Gian Gaetano Tartaglia of the IIT of Genoa, found that the part of the Spike protein that interacts with the sialic acid receptor changes a lot between the various virus strains, which could explain the great differences of Virus behavior observed in different populations. He also studied how the virus acts once inside the cell to reproduce. "We have thus seen that in addition to using some proteins already known and in common with other viruses, there are other specific ones. Of the latter, a dozen are shared with the HIV virus," explains Tartaglia. The suggestion of the researchers is therefore "to try to use, among the antivirals developed in recent years for HIV, those that act in a targeted way on these proteins - he concludes - Even in this case the data must be confirmed, and we hope that this our publication is a scientific word of mouth and sends us useful comments to understand ".