Combination of Genes May Enable Hepatitis C Recovery Without Treatment, Study Says
A specific gene combination may explain why 20% of people infected with hepatitis C are able to clear the infection from their bodies without treatment, according to a study published in the August 6 issue of Science, the AP/Las Vegas Sun reports. Three million people in the United States and 180 million people worldwide are chronically infected with hepatitis C, leaving them at risk for developing liver cancer or liver failure; 10,000 to 12,000 people in the United States die from hepatitis C annually (Neergaard, AP/Las Vegas Sun, 8/5). Approximately 300,000 HIV-positive people in the United States are co-infected with hepatitis C (Kaiser Daily HIV/AIDS Report, 7/30). Researchers from the University of Southampton in England and colleagues examined the DNA of 1,037 hepatitis C patients, 352 of whom had recovered without treatment. Previous studies of the virus in chimpanzees suggested that natural killer cells -- which attack viruses in the body -- are more active in animals that had recovered from hepatitis C infection. Inhibitory receptors called KIRs keep natural killer cells in check between infections so that they do not attack healthy tissue. When the body detects a viral infection, it activates the natural killer cells by inhibiting its KIRs, according to the AP/Sun.
The researchers found that a specific gene combination that controls one KIR receptor and the molecule attached to the receptor was twice as common in patients who recovered from infection. That specific KIR/molecule combination appears to be "weak" and more easily overcome by natural killer cells, according to co-author Dr. Chloe Thio of Johns Hopkins University, the AP/Sun reports. The genetic combination was found only in patients who may have received an "initial low dose" of hepatitis C virus through contaminated needles as opposed to infected blood from a transfusion. Infected blood from transfusions may be "too much for those patients' first-line defenses to handle," Thio said, according to the AP/Sun. Since 1992, the United States has routinely tested blood for hepatitis C, resulting in a decrease in new transfusion-related infections. Currently, the most common cause of hepatitis C infection is sharing needles. Although the findings will not "immediately benefit" hepatitis C patients, they may help in developing new treatments or a vaccine, according to the AP/Sun. In an accompanying Science "Perspective" piece, Dr. Peter Parham of the Department of Structural Biology at Stanford University's School of Medicine said that one type of leukemia is currently treated by releasing natural killer cells from a different KIR receptor and a similar strategy possibly could be developed to treat hepatitis C, the AP/Sun reports (AP/Las Vegas Sun, 8/5).