Endotoxin Stimulates Liver Macrophages To Release Mediators That Inhibit an Early Step in Hepadnavirus Replication

Abstract

Hepadnaviruses are known to be sensitive to various extracellular mediators. Therefore, bacterial endotoxin, which induces the secretion of proinflammatory mediators in the liver, was studied for its effect on hepadnavirus infection in vitro using the duck hepatitis B virus (DHBV) model. In initial experiments, endotoxin was shown to inhibit DHBV replication in primary duck hepatocyte cultures prepared by standard collagenase perfusion. As a primary endotoxin target, hepatic nonparenchymal cells (NPC) contaminating primary hepatocyte cultures, and among these probably macrophages (Kupffer cells), were identified to secrete polypeptide mediators into the cell culture medium. When added during DHBV infection, these mediators elicited the principal antiviral effect in a dose-dependent fashion. On the molecular level, they inhibited accumulation of viral proteins as well as amplification of the nuclear extrachromosomal DHBV DNA templates. In hepatocytes with an established DHBV infection, DHBV protein and progeny virus production was inhibited while the levels of established nuclear DHBV DNA templates and viral transcripts remained unaffected. Finally, in hepatocytes infected with a replication-deficient recombinant DHBV-green fluorescent protein (GFP) virus, the endotoxininduced mediators markedly reduced GFP expression from chimeric DHBV-GFP transcripts, indicating that the major effect is at a level of translation of viral RNAs. Taken together, the data obtained demonstrate that antiviral mediators, and among these the cytokines alpha interferon (IFN-␣) and IFN-␥, are released from hepatic NPC, most probably liver macrophages, upon endotoxin stimulation; furthermore, these mediators act at a posttranscriptional step of hepadnavirus replication.

Liver-specific expression of interferon γ following adenoviral gene transfer controls hepatitis B virus replication in mice

“…In contrast, the amount of the HBV transgene, which serves as a transcription template to initiate HBV replication, as well as HBV transcripts remained unaffected, indicating that HBV replication is blocked by IFNg at a posttranscriptional step. 48,49 Low doses of Dox (0.3 mg/ml) were sufficient to induce IFNg expression and to block HBV replication, and even 10-fold higher doses (3 mg/ ml) had no additional effects. Since the addition of Dox to the drinking water was the only difference between mice in the 'on' and in the 'off' state, and since a treatment with Dox alone had no effect on HBV replication, the drastic effect on HBV replication was clearly due to IFNg expression.…”

Avian hepatitis B viruses: Molecular and cellular biology, phylogenesis, and host tropism

“…It has been shown that the addition of lipopolysaccharides (LPS, endotoxin) to PDH cultures inhibited DHBV replication efficiently [98] . This was due to the release of interferon alpha and gamma from non-parenchymal cells (i.e.…”

Dendritic cells take up viral antigens but do not support the early steps of hepatitis B virus infection

“…To be able to clearly distinguish between adsorption or unspecific uptake of HBV and infection of DC by HBV, we took advantage of recently developed HBVbased vectors. 17 Recombinant HBV allow us to unambiguously assay the early steps of HBV infection 18 because of their ability to express luciferase after successful uptake and nuclear transport. 19 In addition, we investigated the formation of nuclear HBV cccDNA after infection with wild-type HBV.…”