Entry point for hepatitis C infection identified

A molecule embedded in the membrane of human liver cells that aids in cholesterol absorption also allows the entry of hepatitis C virus, the first step in hepatitis C infection, according to research at the University of Illinois at Chicago College of Medicine.

The cholesterol receptor offers a promising new target for anti-viral therapy, for which an approved drug may already exist, say the researchers, whose findings were reported online in advance of publication in Nature Medicine.

An estimated 4.1 million Americans are infected with hepatitis C virus, or HCV, which attacks the liver and leads to inflammation, according to the National Institutes of Health. Most people have no symptoms initially and may not know they have the infection until liver damage shows up decades later during routine medical tests.

Previous studies showed that cholesterol was somehow involved in HCV infection. The UIC researchers suspected that a receptor called NPC1L1, known to help maintain cholesterol balance might also be transporting the virus into the cell.

The receptor is common in the gut of many species - but is found on liver cells only in humans and chimpanzees, says Susan Uprichard, assistant professor in medicine and microbiology and immunology and principal investigator in the study. These primates, she said, are the only animals that can be infected by HCV.

Uprichard and her coworkers showed that knocking down or blocking access to the NPC1L1 receptor prevented the virus from entering and infecting cells.

Bruno Sainz, Jr., UIC postdoctoral research associate in medicine and first author of the paper, said because the receptor is involved in cholesterol metabolism it was already well-studied. A drug that "specifically and uniquely targets NPC1L1" already exists and is approved for use to lower cholesterol levels, he said.

Hepatitis C infection facts

HCV is one of several viruses that cause hepatitis (inflammation of the liver).

Up to 85% of individuals who are initially (acutely) infected with HCV will fail to eliminate the virus and will become chronically infected.

HCV is spread most commonly through inadvertent exposure to infected blood. Intravenous drug abuse is the most common mode of transmission. The risk of acquiring HCV through sexual contact is low.

Generally, patients do not develop symptoms of chronic infection with HCV until they have extensive scarring of the liver (cirrhosis). Some individuals, however, may have fatigue and other non-specific symptoms in the absence of cirrhosis. A minority of patients with HCV have symptoms from organs outside of the liver.

In the U.S., Infection with HCV is the most common cause of chronic hepatitis and the most common reason for liver transplantation.