Daily Archives: May 29, 2020
Both viruses remove marker molecules on the surface of an infected cell that are used by the immune system to identify invaders, the researchers said in a non-peer reviewed paper posted on preprint website bioRxiv.org on Sunday. They warned that this commonality could mean Sars-CoV-2, the clinical name for the virus, could be around for some time, like HIV.
Virologist Zhang Hui and a team from Sun Yat-sen University in Guangzhou also said their discovery added weight to clinical observations that the coronavirus was showing “some characteristics of viruses causing chronic infection”.
Their research involved collecting killer T cells from five patients who had recently recovered from Covid-19, the disease caused by the virus. Those immune cells are generated by people after they are infected with Sars-CoV-2 – their job is to find and destroy the virus.
The molecule is an identification tag usually present in the membrane of a healthy cell, or in sick cells infected by other coronaviruses such as severe acute respiratory syndrome, or Sars. It changes with infections, alerting the immune system whether a cell is healthy or infected by a virus. HIV uses the same strategy – MHC molecules are also absent in cells infected with that virus. “In contrast, Sars does not make use of this function,” Zhang said.
The coronavirus removes these markers by producing a protein known as ORF8, which binds with MHC molecules, then pulls them inside the infected cell and destroys them, the researchers said. ORF8 is known to play an important role in viral replication, and most commercial test kits target this gene to detect viral loads in nose or oral swabs.
While drugs being used to treat Covid-19 patients mainly targeted enzymes or structural proteins needed for viral replication, Zhang and his team suggested compounds be developed “specifically targeting the impairment of MHC by ORF8, and therefore enhancing immune surveillance for Sars-CoV-2 infection”.