Lack of single protein results in persistent viral infection

Scientists from The Scripps Research Institute have shown a single protein can make the difference between an infection clearing out of the body or persisting for life. The results also show where the defects occur in the immune system without the protein and offer the possibility that targetting this signalling pathway could be beneficial for treatment of persistent viral infections in humans.

Currently hundreds of millions of people around the world are afflicted with persistent viral infections such as HIV, HCV, and HBV.

The new study was published in the June 14, 2012 issue of the journal Cell Host & Microbe.

In the new study, a team led by Scripps Research Professor Michael Oldstone showed what happened when a mouse engineered without the protein TLR7 was infected with lymphocytic choriomeningitis virus (LCMV), a virus employed to study the response of the immune system to microbes. While normal mice infected with a LCMV variant called Cl 13 could clear a persistent infection in 60 to 90 days, TLR7-deficient mice were unable to purge the infection throughout their lives.

''It is well known that RNA from many viruses, including influenza, HIV, and hepatitis C, induce signaling through TLR7,'' said Kevin Walsh, a research associate in Oldstone's lab and the first author of the study. ''We demonstrated that TLR7 plays a significant role in the generation of immune responses required to clear persistent LCMV infection.''

'Biological warfare'
In terms of the constant biological warfare between host and microbes, the body is not so much a temple as it is a medieval city. An infectious agent can invade through the skin or mucosa, essentially scaling the walls.