Gastroenterology. 2011 Aug;141(2):686-95, 695.e1. Epub 2011 May 18.

Delayed induction, not impaired recruitment, of specific CD8⁺ T cells causes the late onset of acute hepatitis C.

Shin EC, Park SH, Demino M, Nascimbeni M, Mihalik K, Major M, Veerapu NS, Heller T, Feinstone SM, Rice CM, Rehermann B.

Source

Immunology Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA.

Abstract

BACKGROUND & AIMS:

Hepatitis C virus (HCV) infection is characterized by lack of immune-mediated liver injury despite a high level of HCV replication during the incubation phase, which lasts about 8 weeks. We investigated whether this results from delayed recruitment of HCV-specific T cells and whether it facilitates HCV persistence.

METHODS:

Six chimpanzees were infected with HCV; blood and liver samples were collected for 28 weeks and analyzed for immune cells and chemokines.

RESULTS:

Two chimpanzees developed self-limited infections, whereas the remaining 4 developed chronic infections. Levels of the chemokines CXCL10, CXCL11, CCL4, and CCL5 increased in blood and liver samples from all chimpanzees within 1 month of HCV infection. Chemokine induction correlated with intrahepatic type I interferon (IFN) responses in vivo and was blocked by neutralizing antibodies against IFN-β in vitro. Despite the early-stage induction of chemokines, the intrahepatic lymphocytic infiltrate started to increase no earlier than 8 weeks after HCV infection, when HCV-specific, tetramer-positive CD8(+) T cells appeared in the circulation. The HCV-specific CD8(+) T cells expressed chemokine receptors when they were initially detected in blood samples, so they could be recruited to the liver as soon as they entered the circulation.

CONCLUSIONS:

Chemokines are induced during early stages of HCV infection, which requires a type I IFN-mediated response. The delayed onset of acute hepatitis does not result from delayed recruitment of HCV-specific T cells, but could instead be related to a primary delay in the induction of HCV-specific T cells. Divergent outcomes occur without evident differences in chemokine induction and T-cell recruitment.