Regulatory function of interferon-inducible 44-like for hepatitis B virus covalently closed circular DNA in primary human hepatocytes

Type I gamma phosphatidylinositol phosphate 5-kinase i5 controls cell sensitivity to interferon

The interferon signaling pathway is critical for host defense by serving diverse functions in both innate and adaptive immune responses. Here, we show that type I gamma phosphatidylinositol phosphate 5-kinase i5 (PIPKIγi5), an enzyme that synthesizes phosphatidylinositol-4,5-bisphosphate (PI4,5P2), controls the sensitivity to interferon in both human and mouse cells. PIPKIγi5 directly binds to the interferon-gamma (IFN-γ) downstream effector signal transducer and activator of transcription 1 (STAT1), which suppresses the STAT1 dimerization, IFN-γ-induced STAT1 nuclear translocation, and transcription of IFN-γ-responsive genes. Depletion of PIPKIγi5 significantly enhances IFN-γ signaling and strengthens an antiviral response. In addition, PIPKIγi5-synthesized PI4,5P2 can bind to STAT1 and promote the PIPKIγi5-STAT1 interaction. Similar to its interaction with STAT1, PIPKIγi5 is capable of interacting with other members of the STAT family, including STAT2 and STAT3, thereby suppressing the expression of genes mediated by these transcription factors. These findings identify the function of PIPKIγi5 in immune regulation.

Serum RNase L levels in patients with chronic hepatitis B virus infection

BACKGROUND/AIMS

Chronic hepatitis B virus (HBV) infection still poses a major threat to global health. Oligoadenylate synthetase-ribonuclease L (RNase L) antiviral pathway is one of interferon-induced antiviral effectors. The relationship between RNase L and HBV has never been investigated and we aim to examine the serum RNase L levels in patients with different stages of chronic HBV infection.

METHODS

The patients were enrolled from 1985 to 2000, who had been HBsAg positive for longer than 6 months, at the National Taiwan University Hospital. In total, 426 patients with chronic HBV infection were included in this study, including 135 inactive carriers, 148 cirrhosis, and 143 hepatocellular carcinoma (HCC) cases.

RESULTS

The RNase L levels increase as the disease severity increases. Higher RNase L levels were associated with higher HBV viral load, and the HBV-RNase L relationship was replaced by the disease severity status when adding disease status into the model. Compared with inactive carriers, the risk of liver cirrhosis was 60-fold (odds ratio = 60.8, 95% confidence interval = 3.49-1061) with the highest quintile of RNase L levels, after the adjustment of HBV DNA. The dose-response trend was statistically significant with quintiles and one increment of RNase L level in relation to liver cirrhosis. Similar results were found when HCC was compared with inactive carriers, while there was no association when compared between liver cirrhosis and HCC.

CONCLUSIONS

A positive relationship between serum RNase L and HBV viral titers or advanced disease status is uncovered in this study. Further investigation in this area may provide more details of an innate immune response for HBV and opportunity for novel therapeutic strategy.

Multiscale modeling of HBV infection integrating intra- and intercellular viral propagation to analyze extracellular viral markers

Chronic infection with hepatitis B virus (HBV) is caused by the persistence of closed circular DNA (cccDNA) in the nucleus of infected hepatocytes. Despite available therapeutic anti-HBV agents, eliminating the cccDNA remains challenging. Thus, quantifying and understanding the dynamics of cccDNA are essential for developing effective treatment strategies and new drugs. However, such study requires repeated liver biopsy to measure the intrahepatic cccDNA, which is basically not accepted because liver biopsy is potentially morbid and not common during hepatitis B treatment. We here aimed to develop a noninvasive method for quantifying cccDNA in the liver using surrogate markers in peripheral blood. We constructed a multiscale mathematical model that explicitly incorporates both intracellular and intercellular HBV infection processes. The model, based on age-structured partial differential equations, integrates experimental data from in vitro and in vivo investigations. By applying this model, we roughly predicted the amount and dynamics of intrahepatic cccDNA within a certain range using specific viral markers in serum samples, including HBV DNA, HBsAg, HBeAg, and HBcrAg. Our study represents a significant step towards advancing the understanding of chronic HBV infection. The noninvasive quantification of cccDNA using our proposed method holds promise for improving clinical analyses and treatment strategies. By comprehensively describing the interactions of all components involved in HBV infection, our multiscale mathematical model provides a valuable framework for further research and the development of targeted interventions.

The involvement of an interferon-induced protein 44-like (CgIFI44L) in the antiviral immune response of Crassostrea gigas

Interferon-stimulated genes (ISGs) encoding proteins are the essential executors of interferon (IFN) mediated antiviral defense. In the present study, an ISG member, interferon-induced protein 44-like (IFI44L) gene (designed as CgIFI44L-1) was identified from the Pacific oyster Crassostrea gigas. The ORF of CgIFI44L-1 cDNA was of 1437 bp encoding a polypeptide of 479 amino acids with a TLDc domain and an MMR_HSR1 domain. The mRNA transcripts of CgIFI44L-1 were detected in all the tested tissues with highest level in haemocytes, which was 15.78-fold of that in gonad (p < 0.001). Among the haemocytes, the CgIFI44L-1 protein was detected to be highly expressed in granulocytes with dominant distribution in cytoplasm. The mRNA expression level of CgIFI44L-1 in haemocytes was significantly induced by poly (I:C) stimulation, and the expression level peaked at 24 h, which was 24.24-fold (p < 0.0001) of that in control group. After the treatment with the recombinant protein of an oyster IFN-like protein (rCgIFNLP), the mRNA expression level of CgIFI44L-1 was significantly enhanced at 6 h, 12 h and 24 h, which was 2.67-fold (p < 0.001), 5.44-fold (p < 0.001) and 5.16-fold (p < 0.001) of that in control group, respectively. When the expressions of CgSTAT and CgIFNLP were knocked down by RNA interference (RNAi), the mRNA transcripts of CgIFI44L-1 were significantly down-regulated after poly (I:C) stimulation, which was 0.09-fold (p < 0.001) and 0.06-fold (p < 0.001) of those in EGFP group, respectively. These results suggested that CgIFI44L-1 was a conserved ISG in oyster, which was regulated by CgIFNLP and CgSTAT, and involved in the oyster antiviral immune response.