Intrahepatic Expression of Genes Affiliated with Innate and Adaptive Immune Responses Immediately after Invasion and during Acute Infection with Woodchuck Hepadnavirus

Abstract

The importance of effective immune responses in recovery from acute hepadnaviral hepatitis has been demonstrated. However, there is no conclusive delineation of virological and immunological events occurring in the liver immediately after hepadnavirus invasion and during the preacute phase of infection. These very early events might be of primary importance in determining the recovery or progression to chronic hepatitis and the intrinsic hepadnaviral propensity to persist. In this study, applying the woodchuck model of acute hepatitis B, the hepatic kinetics of hepadnavirus replication and activation of genes encoding cytokines, cytotoxicity effectors, and immune cell markers were quantified in sequential liver biopsies collected from 1 h postinoculation onward by sensitive real-time cDNA amplification assays. The results revealed that hepadnavirus replication is established in the liver as early as 1 hour after infection. In 3 to 6 h, significantly augmented intrahepatic transcription of gamma interferon and interleukin-12 were evident, suggesting activation of antigen-presenting cells. In 48 to 72 h, NK and NKT cells were activated and virus replication was transiently but significantly reduced, implying that this early innate response is at least partially successful in limiting virus propagation. Nonetheless, T cells were activated 4 to 5 weeks later when hepatitis became histologically evident. Collectively, our data demonstrate that virus replication is initiated and the innate response activated in the liver soon after exposure to a liver-pathogenic dose of hepadnavirus. Nevertheless, this response is unable to prompt a timely adaptive T-cell response, in contrast to infections caused by other viral pathogens.

Mechanism of inhibiting type I interferon induction by hepatitis B virus X protein

“…Despite the importance of innate immunity in controlling invading pathogens and relaying signals to the adaptive immune system, it seems to be silent in acutely HBV-infected chimpanzees (Wieland et al, 2004), which are partially attributable to specific replication strategy of HBV (Wieland and Chisari, 2005). Nonetheless, the lack of early intrahepatic antiviral genes induction may be peculiar to chimpanzee models, because NK and NKT cells are activated within 72 h after infection of woodchuck with WHV (woodchuck hepatitis virus), and results in transient suppression of viral replication (Guy et al, 2008). Moreover, IL-15 level and activation of NK and NKT cells are elevated during incubation phase of natural HBV infection, but tend to decline at the peak of viraemia, implying that HBV could counteract innate immune response (Dunn et al, 2009;Fisicaro et al, 2009).…”

Primary Occult Hepadnavirus Infection Induces Virus-Specific T-Cell and Aberrant Cytokine Responses in the Absence of Antiviral Antibody Reactivity in the Woodchuck Model of Hepatitis B Virus Infection

“…Moreover, upregulated hepatic expression of IFN-␥ and TNF-␣ was found to precede HBV-specific T-cell responses and was accompanied by a decrease in HBV replication in the liver in chimpanzees, suggesting that activation of the local innate immunity is, at least partially, successful in limiting virus propagation in acute infection (9,74). Also, in our recent study analyzing the expression profiles of the genes affiliated with intrahepatic immune responses in woodchucks immediately after inoculation with a liver-pathogenic dose of WHV, evidence of very early augmented transcription of the genes indicative of activation of APCs, NK cells, and NK T cells were found (25). However, this early innate response was transient and unable to prompt a virus-specific T-cell response in a timely manner, conversely to infections induced by many other viral pathogens.…”

“…Liver samples collected by biopsy or autopsy were stored at Ϫ80°C until RNA isolation with Trizol reagent. After collection of all experimental samples, RNA was extracted simultaneously and reversely transcribed to cDNA as reported previously (24,25). The expression of woodchuck IFN-␣, IFN-␥, TNF-␣, IL-2, IL-4, IL-10, and IL-12 was quantified using the equivalent of 50 ng of total RNA and woodchuck gene-specific primer pairs as reported in recent works from this laboratory (24,25).…”

“…Sequential liver and PBMC samples collected prior to inoculation with WHV and after challenge with virus were evaluated for the expression of selected cytokine and immune cell marker genes by real-time reverse transcription-PCR (RT-PCR) using a LightCycler (Roche Diagnostics, Mannheim, Germany) (24,25). In the case of PBMC, 5 ϫ 10 5 to 1 ϫ 10 6 freshly isolated cells were suspended in 1 ml of Trizol reagent (Invitrogen) and stored at Ϫ20°C.…”

NK Cells Help Induce Anti–Hepatitis B Virus CD8+ T Cell Immunity in Mice

“…Regarding activating receptors, liver biopsies from woodchucks infected with a hepatitis virus showed upregulation of NKp46 (58). An increase in the frequency of activated NKG2D-expressing NK cells was observed at a very early stage of HBV infection (12).…”