Hepatitis study hits upon clue

Virus's attack on body surprises

Staff WriterJune 21, 2011 

  • Hepatitis C is a chronic disease caused by a virus that attacks the liver. The infection often doesn't cause any symptoms for years - or even decades - and many patients never know they've been infected until the virus causes permanent damage. Very few patients are able to defeat the virus on their own. There is no vaccine.

    Hepatitis A is a short-livedliver infection caused by a very similar virus. Symptoms are usually mild, and patients nearly always recover on their own. There is a vaccine.

— Researchers working to understand the destructive liver disease hepatitis C have made an unexpected discovery that could someday help defeat it.

The virus that causes hepatitis C, long thought to sneak around our bodies' front-line defenses to cause chronic illness, doesn't dodge some of our body's defenses nearly as well as its cousin, hepatitis A.

Since our immune system always beats hepatitis A but rarely beats hepatitis C, this was surprising news for scientists, who expected hepatitis C to be better at slipping past every defense.

"Nobody understands how hepatitis C becomes a chronic infection," says Dr. Stanley Lemon, professor of microbiology and immunology and a member of UNC-Chapel Hill's Lineberger Comprehensive Cancer Center and the Center for Translational Immunology. Lemon collaborated with a team from several institutions to try to unravel the mystery, and their findings were published Monday in the Proceedings of the National Academy of Sciences.

Left untreated, hepatitis C eventually causes liver scarring and can even lead to cancer. But the hepatitis C virus can lurk in the body for many years before doing its damage.

"It's a very quiet infection," says Dr. Andrew Muir, clinical director of hepatology at Duke, who was not connected with the study.

Hepatitis C's stealth makes it tricky to diagnose and treat. Because many patients never feel ill, they never get tested for the disease. After diagnosis, treatment is a brutal regimen of therapy that can drag on for months. The first drugs to target the virus, one of which Muir helped to test, were approved by the FDA in May.

To point the way for further treatments - or even prevention - Lemon collaborated with researchers from several institutions to compare the immune system's initial response to hepatitis C with its response to the easily defeated hepatitis A virus.

Lemon likens the immune system's first response to a burglar alarm. First, a patient's body must detect an infection, using a set of tools that are like the alarm's motion detector. The detector then sends a signal that tells the body to start fighting the infection.

Researchers knew that hepatitis C was sneaky enough to disrupt the signal between the detector and the alarm. "It's just like the burglar got into the house and cut the wire," Lemon says.

They didn't expect, though, that hepatitis A could do this, too. In fact, hepatitis A makes an even better burglar than hepatitis C, even though it causes the milder disease.

So where does this surprising result leave researchers? It tells them that there must be some other way hepatitis C evades our immune system, Lemon says. Figuring out what's not the answer is an important step toward figuring out what is.

And anything that improves understanding of hepatitis C, both Lemon and Muir say, might one day help patients who suffer from the disease.

helen.chappell@newsobserver.com or 919-829-8983

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