A molecular "on-off" switch that controls immune system response to viruses has been identified by researchers at the University of Texas Southwestern Medical Center at Dallas.

They found that when the hepatitis C virus enters the human body, the virus switches on immune system defenses. But the virus can turn off those defenses by manipulating the interactions of certain cellular proteins called RIG-1 and LGP2.

This same "on-off" switch controls immune system response against many kinds of viruses, and the switch may offer a new target for new drugs to fight viruses, the researchers said.

"This knowledge will help us design drugs that mimic the viral effects on these proteins to either activate a host's immune response or shut it down, " study senior author Dr. Michael Gale, an associate professor of microbiology, said in a prepared statement.

"This holds great potential in developing new disease therapies, because the tactics employed by hepatitis C to trigger immune response are similar to those employed by other viruses such as West Nile, influenza and the common cold, " Gale said.