Hepatitis C virus (HCV) infection often causes liver diseases, including fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Liver fibrosis is the outcome of the wound healing response to tissue damage caused by chronic HCV infection. This process is characterized by the excessive accumulation of extracellular matrix (ECM) proteins, such as collagen fibers secreted by activated hepatic stellate cells (HSCs). Activation of HSCs from the quiescent stage is mediated by different mechanisms, including pro-inflammatory cytokines and chemokines released from HCV-infected hepatocytes and liver macrophages. HCV infection modulates the expression of different microRNAs that can be transported and delivered to the HSCs via exosomes released from infected cells, also leading to the development of advanced disease pathogenesis. Although recent advancements in direct-acting antiviral (DAA) treatment can efficiently control viremia, there are very few treatment strategies available that can be effective at preventing pathogenesis in advanced liver fibrosis or cirrhosis in patients. Assessment of fibrosis is considered to be the major part of proper patient care and decision making in clinical practice. In this review, we highlighted the current knowledge of molecular mechanisms responsible for the progression of liver fibrosis in chronically HCV-infected patients, and currently available methods for evaluation of fibrosis in patients. A detailed understanding of these aspects at the molecular level may contribute to the development of new therapies targeting HCV-related liver fibrosis.

SARS-CoV-2 infection can cause cytokine storm and may overshoot immunity in humans; however, it remains to be determined whether virus-induced soluble mediators from infected cells are carried by exosomes as vehicles to distant organs and cause tissue damage in COVID-19 patients. We took an unbiased proteomic approach for analyses of exosomes isolated from plasma of healthy volunteers and COVID-19 patients. Our results revealed that tenascin-C (TNC) and fibrinogen-β (FGB) are highly abundant in exosomes from COVID-19 patients’ plasma compared with that of healthy normal controls. Since TNC and FGB stimulate pro-inflammatory cytokines via the Nuclear factor-κB (NF-κB) pathway, we examined the status of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and C–C motif chemokine ligand 5 (CCL5) expression upon exposure of hepatocytes to exosomes from COVID-19 patients and observed significant increase compared with that from healthy subjects. Together, our results demonstrate that TNC and FGB are transported through plasma exosomes and potentially trigger pro-inflammatory cytokine signaling in cells of distant organ.

SARS-CoV-2 infection causes cytokine storm and overshoot immunity in humans; however, it remains to be determined whether genetic material of SARS-CoV-2 and/or virus induced soluble mediators from lung epithelial cells as natural host are carried out by macrophages or other vehicles at distant organs causing tissue damage. We speculated that exosomes as extracellular vesicles are secreted from SARS-CoV-2 infected cells may transport messages to other cells of distant organs leading to pathogenic consequences. For this, we took an unbiased proteomic approach for analyses of exosomes isolated from plasma of healthy volunteers and SARS-CoV-2 infected patients. Our results revealed that tenascin-C (TNC) and fibrinogen-β (FGB) are highly abundant in exosomes from SARS-CoV-2 infected patient's plasma as compared to that of healthy normal controls. Since TNC and FGB stimulate pro-inflammatory cytokines via NF-kB pathway, we examined the status of TNF-a, IL-6 and CCL5 expression upon exposure of hepatocytes to exosomes from COVID-19 patients and observed significant increase when compared with that from healthy subjects. Together, our results demonstrated that soluble mediators, like TNC and FGB, are transported through plasma exosomes in SARS-CoV-2 infected patients and trigger pro-inflammatory cytokine expression in cells of distant organs in COVID-19 patients.

BaCKgRoUND aND aIMS: HCV often causes chronic infection in liver, cirrhosis, and, in some instances, HCC. HCV encodes several factors' those impair host genes for establishment of chronic infection. The long noncoding RNAs (lncRNAs) display diverse effects on biological regulations. However, their role in virus replication and underlying diseases is poorly understood. In this study, we have shown that HCV exploits lncRNA long intergenic nonprotein-coding RNA, p53 induced transcript (Linc-Pint) in hepatocytes for enhancement of lipogenesis. appRoaCH aND ReSUltS: We identified a lncRNA, Linc-Pint, which is significantly down-regulated in HCV-replicating hepatocytes and liver specimens from HCV infected patients. Using RNA pull-down proteomics, we identified serine/arginine protein specific kinase 2 (SRPK2) as an interacting partner of Linc-Pint. A subsequent study demonstrated that overexpression of Linc-Pint inhibits the expression of lipogenesis-related genes, such as fatty acid synthase and ATP-citrate lyase. We also observed that Linc-Pint significantly inhibits HCV replication. Furthermore, HCV-mediated enhanced lipogenesis can be controlled by exogenous Linc-Pint expression. Together, our results suggested that HCV-mediated down-regulation of Linc-Pint enhances lipogenesis favoring virus replication and liver disease progression. CoNClUSIoNS:We have shown that SRPK2 is a direct target of Linc-Pint and that depletion of SRPK2 inhibits lipogenesis. Our study contributes to the mechanistic understanding of the role of Linc-Pint in HCV-associated liver pathogenesis. (Hepatology 2021;74:41-54).

No abstract

Hepatitis B e-antigen negative (e(-)) chronic HBV infection (CHI) encompasses a heterogeneous clinical spectrum ranging from inactive carrier (IC) state to e(-) chronic hepatitis B (CHB), cirrhosis and hepatic decompensation. In the backdrop of dysfunctional virus-specific T cells, natural killer (NK) cells are emerging as innate effectors in CHI. We characterized CD3(-) CD56(+) NK cells in clinically well-defined, treatment-naive e(-) patients in IC, e(-)CHB or decompensated liver cirrhosis (LC) phase to appraise their role in disease progression. The NK cell frequencies increased progressively with disease severity (IC 8.2%, e(-)CHB 13.2% and LC 14.4%). Higher proportion of NK cells from LC/e(-)CHB expressed CD69, NKp46, NKp44, TRAIL and perforin, the last two being prominent features of CD56(bright) and CD56(dim) NK subsets, respectively. The frequencies of CD3(-) CD56(+) NK cells together with TRAIL(+) CD56(bright) and Perforin(+) CD56(dim) NK cells correlated positively with serum alanine transaminase levels in e(-)CHB/LC. K562 cell-stimulated NK cells from e(-)CHB/LC exhibited significantly greater degranulation but diminished interferon-γ production than IC. Further, Perforin(+) NK cell frequency inversely correlated with autologous CD4(+) T-cell count in e(-) patients and ligands of NK receptors were over-expressed in CD4(+) T cells from e(-)CHB/LC relative to IC. Co-culture of sorted CD56(dim) NK cells and CD4(+) T cells from e(-)CHB showed enhanced CD4(+) T-cell apoptosis, which was reduced by perforin inhibitor, concanamycin A, suggesting a possible perforin-dependent NK cell-mediated CD4(+) T-cell depletion. Moreover, greater incidence of perforin-expressing NK cells and decline in CD4(+) T cells were noticed intrahepatically in e(-)CHB than IC. Collectively, NK cells contribute to the progression of e(-)CHI by enhanced TRAIL- and perforin-dependent cytolytic activity and by restraining anti-viral immunity through reduced interferon-γ secretion and perforin-mediated CD4(+) T-cell lysis.

No abstract

An important driving force behind the sequence diversity of hepatitis B virus (HBV) is viral adaptation to host immune responses. To gain an insight into the impact of host immunity on genetic diversification and properties of HBV, we characterized HBV of genotype D from treatment-naive hepatitis B e antigen-positive (EP) and hepatitis B e antigen-negative (EN) patients with chronic hepatitis B (CHB), where HBV is under stronger immune pressure, with that of HBV derived from human immunodeficiency virus (HIV)/HBV-coinfected individuals, where HIV infection has significantly weakened the immune system. Full-length sequence analysis showed that HBV heterogeneity was most extensive in EN-CHB followed by EP-CHB and HIV/HBV coinfection. The relative magnitude of non-synonymous changes within B-cell epitopes was greater than that in T-cell epitopes of HBV open reading frames (ORFs) in both EP-CHB and EN-CHB. Nine amino acid substitutions were identified in B-cell epitopes and one in a T-cell epitope of HBV in EN-CHB, most of which resulted in altered hydrophobicities, as determined using the Kyte and Doolittle method, relative to wild-type residues found in HBV from the HIV-positive group. Additionally, 19 substitutions occurred at significantly higher frequencies in non-epitope regions of HBV ORF-P in EN-CHB than HIV/HBV-coinfected patients. In vitro replication assay demonstrated that the substitutions, particularly in reverse transcriptase and RNaseH domains of ORF-P, resulted in a decline in replication capacity of HBV. Hence, our results indicate that HBV adapts to increasing immune pressure through preferential mutations in B-cell epitopes and by replicative attenuation. The viral epitopes linked to immune response identified in this study bear important implications for future HBV vaccine studies.