To do that Sars-Cov-2-Virus, that the disease COVID-19 triggers, there are still many puzzles after more than half a year. We now largely know how it spreads and what it can do to the body. How to avoid the virus spreading in the body in the first place is what scientists around the world are researching at full speed. An international team from Germany, Switzerland and the USA has come a big step closer to answering this question.

The scientists were able to prove that the LY6E protein, a protein that is produced by the human immune system and can strongly inhibit coronaviruses, can also prevent Sars-Cov-2 from causing an infection. “This provides information on possible treatment strategies,” says Prof. Dr. Stephanie Pfänder from the Molecular and Medical Virology Department of the Ruhr University Bochum (RUB), first author of the study LY6E impairs coronavirus fusion and confers immune control of viral disease, which the team published in the journal Nature Microbiology.

Bad with flu, good against corona viruses

The American researcher Prof. Dr. John Schoggins and Prof. Dr. Charles Rice discovered some time ago that the LY6E protein plays a role in various diseases and, for example, increases the infectivity of influenza-causing influenza viruses. Research into genes that inhibit coronaviruses has now led to the discovery that “LY6E has the opposite effect on coronaviruses compared to flu viruses: it has a strong inhibitory effect on them,” says Pfänder.

Further studies would have shown “that the protein exerted this inhibitory effect on all corona viruses tested, including the pathogens of Sars and Mers and Sars-Cov-2, the trigger of Covid-19”. Tests with different cell cultures have shown that LY6E affects the ability of the virus to unite with the host cells in the body. “If the virus cannot fuse with these cells, it cannot trigger an infection,” explains last author Prof. Dr. Volker Thiel from the University of Bern.

Stephanie Pfänder looks for genes that inhibit corona viruses. © RUB, Marquard

Evidence in the animal model

Experiments at the Southwestern Medical Center at the University of Texas have shown that “the mouse variant of the protein called Ly6e is crucial for protecting immune cells from infections”. Without Ly6e, immune cells such as dendritic cells and B cells would be more susceptible to infection, and the number would decrease dramatically, the researchers write. Mice without Ly6e in immune cells were very susceptible to and died from even a mouse coronavirus, which is usually not fatal.

The mouse coronavirus used in the experiment is “clearly” different from the Sars Cov-2 virus and does not cause respiratory disease but hepatitis. However, it is still useful to understand basic concepts of coronavirus replication and immune responses in a living animal.

“Our study brings new insights into how important these antiviral genes are for controlling virus infection and for an adequate immune response against the virus,” the authors emphasize. “Because LY6E is a naturally occurring human protein, we hope that this knowledge can help develop therapies that could one day be used to treat coronavirus infections.” A therapeutic approach that mimics the mechanism of action of LY6E, could represent a first line of defense against new types of coronavirus infections.

Stephanie Pfänder was funded by the European Commission as part of a Marie Skłodowska Curie Fellowship.