Control of temporal activation of hepatitis C virus-induced interferon response by domain 2 of nonstructural protein 5A.

Background & Aims: Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) is a multifunctional protein playing a crucial role in diverse steps of the viral replication cycle and perturbing multiple host cell pathways. We showed previously that removal of a region in domain 2 (D2) of NS5A (mutant NS5A(D2Δ)) is dispensable for viral replication in hepatoma cell lines. By using a mouse model and immune-competent cell systems, we studied the role of D2 in controlling the innate immune response.

Persistence of HCV in quiescent hepatic cells under conditions of an interferon-induced antiviral response.

Background & Aims: Hepatitis C virus (HCV) is a common cause of chronic liver disease. Many patients do not clear the viral infection; little is known about the mechanisms of HCV persistence or the frequent failure of interferon (IFN) to eliminate it. Better culture systems are needed to study viral replication in quiescent liver cells.

Interleukin-32: a new proinflammatory cytokine involved in hepatitis C virus-related liver inflammation and fibrosis.

Unlabelled: Interleukin 32 (IL-32) is a recently described proinflammatory cytokine that activates p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB), thereby inducing proinflammatory cytokines such as IL-1β and tumor necrosis factor alpha (TNF-α). We investigated the role of IL-32 in patients with chronic hepatitis C virus (HCV) infection. Steady-state hepatic messenger RNA (mRNA) levels of IL-32 were determined in a cohort of 90 subjects; anti-IL-32 staining was used in a second cohort of 132 consecutive untreated chronic HCV patients.

Classical swine fever virus can remain virulent after specific elimination of the interferon regulatory factor 3-degrading function of Npro.

Pestiviruses prevent alpha/beta interferon (IFN-alpha/beta) production by promoting proteasomal degradation of interferon regulatory factor 3 (IRF3) by means of the viral N(pro) nonstructural protein. N(pro) is also an autoprotease, and its amino-terminal coding sequence is involved in translation initiation. We previously showed with classical swine fever virus (CSFV) that deletion of the entire N(pro) gene resulted in attenuation in pigs.

Nonstructural proteins NS2-3 and NS4A of classical swine fever virus: essential features for infectious particle formation.

The nonstructural protein NS2-3 of pestiviruses undergoes tightly regulated processing. For bovine viral diarrhea virus it was shown that uncleaved NS2-3 is required for infectious particle formation while cleaved NS3 is essential for genome replication. To further investigate the functions of NS2-3 and NS4A in the pestivirus life cycle, we established T7 RNA polymerase-dependent trans-complementation for p7-NS2-3-4A of classical swine fever virus (CSFV).

Classical swine fever virus Npro interacts with interferon regulatory factor 3 and induces its proteasomal degradation.

Viruses have evolved a multitude of strategies to subvert the innate immune system by interfering with components of the alpha/beta interferon (IFN-alpha/beta) induction and signaling pathway. It is well established that the pestiviruses prevent IFN-alpha/beta induction in their primary target cells, such as epitheloidal and endothelial cells, macrophages, and conventional dendritic cells, a phenotype mediated by the viral protein N(pro). Central players in the IFN-alpha/beta induction cascade are interferon regulatory factor 3 (IRF3) and IRF7.

Classical swine fever virus replicon particles lacking the Erns gene: a potential marker vaccine for intradermal application.

Classical swine fever virus replicon particles (CSF-VRP) deficient for E(rns) were evaluated as a non-transmissible marker vaccine. A cDNA clone of CSFV strain Alfort/187 was used to obtain a replication-competent mutant genome (replicon) lacking the sequence encoding the 227 amino acids of the glycoprotein E(rns) (A187delE(rns)). For packaging of A187delE(rns) into virus particles, porcine kidney cell lines constitutively expressing E(rns) of CSFV were established.

Role of double-stranded RNA and Npro of classical swine fever virus in the activation of monocyte-derived dendritic cells.

Classical swine fever virus (CSFV) is a noncytopathogenic (ncp) positive-sense RNA virus that replicates in myeloid cells including macrophages and dendritic cells (DC). The virus does not induce type I interferon (IFN-alpha/beta), which in macrophages has been related to the presence of the viral Npro gene. In the present work, the role of viral double-stranded (ds)RNA and Npro in the virus-host cell interaction has been analyzed.

N(pro) of classical swine fever virus is an antagonist of double-stranded RNA-mediated apoptosis and IFN-alpha/beta induction.

Classical swine fever virus (CSFV) protects cells from double-stranded (ds) RNA-mediated apoptosis and IFN-alpha/beta induction. This phenotype is lost when CSFV lacks N(pro) (DeltaN(pro) CSFV). In the present study, we demonstrate that N(pro) counteracts dsRNA-mediated apoptosis and IFN-alpha/beta induction independently of other CSFV elements.