Intrahepatic Infiltrating NK and CD8 T Cells Cause Liver Cell Death in Different Phases of Dengue Virus Infection

Elevated liver enzyme level is an outstanding feature in patients with dengue. However, the pathogenic mechanism of liver injury has not been clearly demonstrated. In this study, employing a mouse model we aimed to investigate the immunopathogenic mechanism of dengue liver injury. Immunocompetent C57BL/6 mice were infected intravenously with dengue virus strain 16681. Infected mice had transient viremia, detectable viral capsid gene and cleaved caspase 3 in the liver. In the mean time, NK cell and T cell infiltrations peaked at days 1 and 5, respectively. Neutralizing CXCL10 or depletion of Asialo GM1(+) cells reduced cleaved caspase 3 and TUNEL(+) cells in the liver at day 1 after infection. CD8(+) T cells infiltrated into the liver at later time point and at which time intrahepatic leukocytes (IHL) exhibited cytotoxicity against DENV-infected targets. Cleaved caspase 3 and TUNEL(+) cells were diminished in mice with TCRβ deficiency and in those depleted of CD8(+) T cells, respectively, at day 5 after infection. Moreover, intrahepatic CD8(+) T cells were like their splenic counterparts recognized DENV NS4B(99-107) peptide. Together, these results show that infiltrating NK and CD8(+) T cells cause liver cell death. While NK cells were responsible for cell death at early time point of infection, CD8(+) T cells were for later. CD8(+) T cells that recognize NS4B(99-107) constitute at least one of the major intrahepatic cytotoxic CD8(+) T cell populations.