CD8(+) T cells mediate viral clearance and disease pathogenesis during acute hepatitis B virus infection

Abstract

Although the CD4(+)- and CD8(+)-T-cell responses to the hepatitis B virus (HBV) are thought to be crucial for the control of HBV infection, the relative contribution of each T-cell subset as an effector of viral clearance is not known. To examine this question, we monitored the course of HBV infection in control, CD4-depleted, and CD8-depleted chimpanzees. Our results demonstrate that CD8(+) cells are the main effector cells responsible for viral clearance and disease pathogenesis during acute HBV infection, and they suggest that viral clearance is mediated by both noncytolytic and cytolytic effector functions of the CD8(+)-T-cell response.

FIG. 1.

Course of acute HBV infection in chimpanzees after experimental inoculation with HBV in the presence or absence of CD4⁺ and CD8⁺ cells. All animals were inoculated with 10⁸ GE of HBV intravenously in week 0 and with a monoclonal antibody (see below) in week 6. (A) Chimpanzee (Ch.) 1627 was injected with irrelevant control antibody (Ab). (B) Chimpanzee 1615 was injected with a CD4-specific monoclonal antibody. (C) Chimpanzee 1620 was injected with a CD8-specific monoclonal antibody. Intrahepatic HBV DNA (black triangles) is expressed as a percentage (%max) of the corresponding peak HBV DNA levels in the liver of each animal. sALT activity (black squares) is expressed in units per liter. HBcAg-positive hepatocytes are expressed as a percentage of the total number of hepatocytes. The number of CD3⁺ CD4⁺ or CD3⁺ CD8⁺ T cells is expressed as a percentage of the total number of CD3⁺ T cells in the peripheral blood. Vertical arrows indicate the time of antibody treatment.

FIG. 2.

Intrahepatic cytokine profile and HBV-specific T-cell responses during acute HBV infection in control chimpanzee (Ch.) 1627. (A) The courses of intrahepatic HBV DNA and sALT activity during acute infection are displayed as described in the legend to Fig. 1, except for the intrahepatic HBV DNA content, which is displayed on a logarithmic scale in this figure and in Fig. 3 and 4 in order to facilitate comparison of the duration of the infection in the 3 animals. (B) Total RNA isolated from liver biopsy samples was analyzed for the expression of CD3, IFN-γ, and L32 by an RNase protection assay. The L32 signals reflect the amount of RNA used in the assay. (C) The intrahepatic CD4⁺-T-cell response to HBcAg is expressed as the SI. (D) The intrahepatic CD8⁺-T-cell response is shown as the percentage of intrahepatic CD8⁺ cells that produce IFN-γ after stimulation with autologous EBV B cells that were infected with recombinant vaccinia viruses expressing the HBV core, polymerase, and large envelope proteins after subtraction of their responsiveness to the same B cells infected by wild-type vaccinia virus. The vertical arrow indicates control antibody (Ab) treatment.

FIG. 3.

Intrahepatic cytokine profile and HBV-specific T-cell responses during acute HBV infection and CD4 depletion in chimpanzee (Ch.) 1615. (A) The courses of intrahepatic HBV DNA and sALT activity during acute infection and CD4 depletion are displayed as described in the legend to Fig. 2A. (B) Analysis of intrahepatic CD3, IFN-γ, and L32 expression. (C) The intrahepatic CD4⁺-T-cell response to HBcAg during acute infection and CD4 depletion. (D) Intrahepatic CD8⁺-T-cell responses during acute infection and CD4 depletion. See the legend to Fig. 2 for all other details. Ab, antibody.

FIG. 4.

Intrahepatic cytokine profile and HBV-specific T-cell responses during acute HBV infection and CD8 depletion in chimpanzee (Ch.) 1620. (A) The courses of intrahepatic HBV DNA and sALT activity during acute infection and CD8 depletion are displayed as described in the legend to Fig. 2A. (B) Analysis of intrahepatic CD3, IFN-γ, and L32 expression. (C) The intrahepatic CD4⁺-T-cell response to HBcAg during acute infection and CD8 depletion. (D) Intrahepatic CD8⁺-T-cell responses during acute infection and CD8 depletion. See the legend to Fig. 2 for all other details. Ab, antibody.