An infection with Sars-CoV-2 does not make everyone sick. A team of researchers from the University of Sydney is able to identify the substance that forms the immune barrier. It also helps with other pathogens. On this basis, effective drugs are conceivable in the future.
Researchers have discovered a substance in the lungs that inhibits Sars-CoV-2 from docking to human cells. The team led by Professor Greg Neely from the Charles Perkins Center at the University of Sydney identified the special protein and named it LRRC15. For the researchers, it is conceivable that a high concentration of LRRC15 restricts the mobility of Sars-CoV-2 to such an extent that people do not contract the virus. If this can be confirmed in further studies, then the mystery of Covid-19 immunity would be solved.
For the study, the team first used a specific genomics method to examine human cells for proteins to which the coronavirus can bind. This is how they came across the receptor protein LRRC15. This is found in the lungs of people who have died from Covid-19 or other diseases. However, the research team found no evidence of LRRC15 in people who had no viral infections. They therefore assume that this receptor protein forms a new part of the immune barrier that helps protect against severe Covid-19 infection and at the same time activates the body's antiviral response.
The researchers assume that either not enough LRRC15 or that it was not produced in time by the body to keep the infection in check. "If we look at the lungs of patients who have died from Covid, there is a lot of this protein," Neely said, according to The Guardian. "But we couldn't look at the lungs of patients who survived Covid because lung biopsy is not that easy to do in living people. But we are very confident that survivors have more of this protein than those who died from Covid are." LRRC15 is normally highly expressed in tissues that form important immune barriers such as the placenta, skin and various lymphatic vessels.
In a previous study by London scientists examining blood samples for LRRC15, researchers concluded that the protein in the blood was lower in patients with severe Covid-19 than in those with mild Covid. This finding supports the theory of the research teams in Sydney. "Our data suggest that higher LRRC15 levels mean that people have less severe disease," Neely is quoted as saying.
"The fact that there is this natural immune receptor that we didn't know that lines our lungs and blocks and controls viruses is insanely interesting." LRRC15 acts a bit like molecular Velcro, attaching itself to the tip of the virus and then pulling it away from target cell types," explains Dr Lipin Loo, who was also involved in the study.
The findings could be used in the future to develop drugs with a broad spectrum of action against various viral pathogens. But until then, more research needs to be done. The results of the study were published in the current journal "PLOS Biology".
