A Purdue University-led research team has figured out how to disable a part of the SARS virus responsible for hiding it from the immune system; a critical step in developing a vaccine against the deadly disease.
"This is a first step toward creating a weakened and safe virus for use in an attenuated live vaccine," said Mesecar, Purdue's Walther Professor of Cancer Structural Biology and professor of biological sciences and chemistry. "This also could serve as a molecular roadmap for performing similar studies on other coronaviruses, like MERS, because this enzyme appears to be common to all viruses within this family."
Mesecar and his team captured the molecular structure of a key SARS enzyme, papain-like protease, and revealed how it strips a host cell of the proteins ubiquitin and ISG15, which are involved in triggering an immune response.
"With most viruses, when a cell is infected it sends out an alarm triggering an immune response that fights the infection, but successful viruses are able to trick the immune system," Mesecar said. "By clipping off these two proteins, SARS short circuits the host cell's signaling pathways and prevents it from alerting the immune system to its presence. By removing these proteins, the enzyme serves as a biological cloaking system for the SARS virus that allows it to live and replicate undetected."
The disruption in its natural signaling pathways also causes an infected cell to miscommunicate with the cells around it, which leads to a response that eventually kills those cells, he said.
"Some treatments prevent a virus from replicating and stop further infection, but that doesn't necessarily prevent a harmful reaction to the virus," Mesecar said. "Sometimes it is the confusion in cellular communication that makes a virus lethal."