Elimination of Hepatitis C Virus from Hepatocytes by a Selective Activation of Therapeutic Molecules

To eliminate hepatitis C virus (HCV) from infected hepatocytes, we generated two therapeutic molecules specifically activated in cells infected with HCV. A dominant active mutant of interferon (IFN) regulatory factor 7 (IRF7) and a negative regulator of HCV replication, VAP-C (Vesicle-associated membrane protein-associated protein subtype C), were fused with the C-terminal region of IPS-1 (IFNβ promoter stimulator-1), which includes an HCV protease cleavage site that was modified to be localized on the ER membrane, and designated cIRF7 and cVAP-C, respectively. In cells expressing the HCV protease, cIRF7 was cleaved and the processed fragment was migrated into the nucleus, where it activated various IFN promoters, including promoters of IFNα6, IFNβ, and IFN stimulated response element. Activation of the IFN promoters and suppression of viral RNA replication were observed in the HCV replicon cells and in cells infected with the JFH1 strain of HCV (HCVcc) by expression of cIRF7. Suppression of viral RNA replication was observed even in the IFN-resistant replicon cells by the expression of cIRF7. Expression of the cVAP-C also resulted in suppression of HCV replication in both the replicon and HCVcc infected cells. These results suggest that delivery of the therapeutic molecules into the liver of hepatitis C patients, followed by selective activation of the molecules in HCV-infected hepatocytes, is a feasible method for eliminating HCV

Broad action of Hsp90 as a host chaperone required for viral replication

Viruses are intracellular pathogens responsible for a vast number of human diseases. Due to their small genome size, viruses rely primarily on the biosynthetic apparatus of the host for their replication. Recent work has shown that the molecular chaperone Hsp90 is nearly universally required for viral protein homeostasis. As observed for many endogenous cellular proteins, numerous different viral proteins have been shown to require Hsp90 for their folding, assembly, and maturation. Importantly, the unique characteristics of viral replication cause viruses to be hypersensitive to Hsp90 inhibition, thus providing a novel therapeutic avenue for the development of broad-spectrum antiviral drugs. The major developments in this emerging field are hereby discussed. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).Work in the Frydman lab is supported by NIH grant GM56433. S.T. acknowledges support of grants-in-aid from the Naito Foundation and the Uehara Memorial Foundation.Peer reviewe

Broad action of Hsp90 as a host chaperone required for viral replication

Viruses are intracellular pathogens responsible for a vast number of human diseases. Due to their small genome size, viruses rely primarily on the biosynthetic apparatus of the host for their replication. Recent work has shown that the molecular chaperone Hsp90 is nearly universally required for viral protein homeostasis. As observed for many endogenous cellular proteins, numerous different viral proteins have been shown to require Hsp90 for their folding, assembly, and maturation. Importantly, the unique characteristics of viral replication cause viruses to be hypersensitive to Hsp90 inhibition, thus providing a novel therapeutic avenue for the development of broad-spectrum antiviral drugs. The major developments in this emerging field are hereby discussed. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).Work in the Frydman lab is supported by NIH grant GM56433. S.T. acknowledges support of grants-in-aid from the Naito Foundation and the Uehara Memorial Foundation.Peer reviewe

Human Butyrate-Induced Transcript 1 Interacts with Hepatitis C Virus NS5A and Regulates Viral Replication▿

Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) is required for the replication of the viral genome and is involved in several host signaling pathways. To gain further insight into the functional role of NS5A in HCV replication, we screened human cDNA libraries by a yeast two-hybrid system using NS5A as the bait and identified human butyrate-induced transcript 1 (hB-ind1) as a novel NS5A-binding protein. Endogenously and exogenously expressed hB-ind1 was coimmunoprecipitated with NS5A of various genotypes through the coiled-coil domain of hB-ind1. The small interfering RNA (siRNA)-mediated knockdown of hB-ind1 in human hepatoma cell lines suppressed the replication of HCV RNA replicons and the production of infectious particles of HCV genotype 2a strain JFH1. Furthermore, these reductions were canceled by the expression of an siRNA-resistant hB-ind1 mutant. Among the NS5A-binding host proteins involved in HCV replication, hB-ind1 exhibited binding with FKBP8, and hB-ind1 interacted with Hsp90 through the FxxW motif in its N-terminal p23 homology domain. The impairment of the replication of HCV RNA replicons and of the production of infectious particles of JFH1 virus in the hB-ind1 knockdown cell lines was not reversed by the expression of an siRNA-resistant hB-ind1 mutant in which the FxxW motif was replaced by AxxA. These results suggest that hB-ind1 plays a crucial role in HCV RNA replication and the propagation of JFH1 virus through interaction with viral and host proteins

Principles of dengue virus evolvability derived from genotype-fitness maps in human and mosquito cells.

Dengue virus (DENV) cycles between mosquito and mammalian hosts. To examine how DENV populations adapt to these different host environments, we used serial passage in human and mosquito cell lines and estimated fitness effects for all single-nucleotide variants in these populations using ultra-deep sequencing. This allowed us to determine the contributions of beneficial and deleterious mutations to the collective fitness of the population. Our analysis revealed that the continuous influx of a large burden of deleterious mutations counterbalances the effect of rare, host-specific beneficial mutations to shape the path of adaptation. Beneficial mutations preferentially map to intrinsically disordered domains in the viral proteome and cluster to defined regions in the genome. These phenotypically redundant adaptive alleles may facilitate host-specific DENV adaptation. Importantly, the evolutionary constraints described in our simple system mirror trends observed across DENV and Zika strains, indicating it recapitulates key biophysical and biological constraints shaping long-term viral evolution

Principles of dengue virus evolvability derived from genotype-fitness maps in human and mosquito cells.

Dengue virus (DENV) cycles between mosquito and mammalian hosts. To examine how DENV populations adapt to these different host environments, we used serial passage in human and mosquito cell lines and estimated fitness effects for all single-nucleotide variants in these populations using ultra-deep sequencing. This allowed us to determine the contributions of beneficial and deleterious mutations to the collective fitness of the population. Our analysis revealed that the continuous influx of a large burden of deleterious mutations counterbalances the effect of rare, host-specific beneficial mutations to shape the path of adaptation. Beneficial mutations preferentially map to intrinsically disordered domains in the viral proteome and cluster to defined regions in the genome. These phenotypically redundant adaptive alleles may facilitate host-specific DENV adaptation. Importantly, the evolutionary constraints described in our simple system mirror trends observed across DENV and Zika strains, indicating it recapitulates key biophysical and biological constraints shaping long-term viral evolution

Involvement of cyclophilin B in the replication of Japanese encephalitis virus

AbstractJapanese encephalitis virus (JEV) is a mosquito-borne RNA virus that belongs to the Flaviviridae family. In this study, we have examined the effect of cyclosporin A (CsA) on the propagation of JEV. CsA exhibited potent anti-JEV activity in various mammalian cell lines through the inhibition of CypB. The propagation of JEV was impaired in the CypB-knockdown cells and this reduction was cancelled by the expression of wild-type but not of peptidylprolyl cis-trans isomerase (PPIase)-deficient CypB, indicating that PPIase activity of CypB is critical for JEV propagation. Infection of pseudotype viruses bearing JEV envelope proteins was not impaired by the knockdown of CypB, suggesting that CypB participates in the replication but not in the entry of JEV. CypB was colocalized and immunoprecipitated with JEV NS4A in infected cells. These results suggest that CypB plays a crucial role in the replication of JEV through an interaction with NS4A

Hepatitis C virus NS5A protein promotes the lysosomal degradation of diacylglycerol O-acyltransferase 1 (DGAT1) via endosomal microautophagy

Many viruses often use a protein degradation system (e.g., the ubiquitin-proteasome pathway or lysosome pathway) to modulate viral propagation and viral pathogenesis. We reported that hepatitis C virus (HCV) infection promotes the lysosomal degradation of hepatocyte nuclear factor-1α (HNF-1α) via chaperone-mediated autophagy (CMA) through an NS5A-mediated association of HNF-1α with cellular chaperone heat shock cognate 70 kDa (HSC70) protein. HSC70 binds to the pentapeptide KFERQ motif (also known as a CMA-targeting motif) on HNF-1α protein and promotes the lysosomal degradation of HNF-1α. The KFERQ motif plays a crucial role in the two lysosomal degradation pathways, CMA and endosomal microautophagy (eMI). Herein, we searched for a novel substrate of HCV-induced lysosomal degradation by examining the NS5A-interacting proteins that carry the KFERQ motif. We identified diacylglycerol O-acyltransferase 1 (DGAT1), which is a key factor for HCV particle formation, as a candidate substrate for HCV-induced lysosomal degradation pathway. The region spanning from amino acids 149–153 of DGAT1 protein matches the rule for the KFERQ motif. DGAT1 protein was co-immunoprecipitated with HSC70, whereas DGAT1 Q149A mutant was not co-immunoprecipitated with HSC70, suggesting that the KFERQ motif is responsible for the interaction between DGAT1 and HSC70. Knockdown of LAMP-2A protein in HCV J6/JFH1-infected cells did not recover DGAT1 protein, whereas knockdown of VPS4B recovered the level of DGAT1 protein, suggesting that DGAT1 is degraded via eMI. These findings lead us to propose that HCV NS5A protein facilitates the recruitment of HSC70 to DGAT1, thereby promoting the lysosomal degradation of DGAT1 via eMI. Abbreviations 3-MA: 3-methyladenine; aa: amino acids; AH: amphipathic helix; BSA: bovine serum albumin; CMA: chaperone-mediated autophagy; DAAs: direct-acting antiviral; DGAT1: diacylglycerol O-acyltransferase 1; DMSO: dimethyl sulfoxide; EL: extracellular lumen; eMI: endosomal microautophagy; ESCRT: endosomal sorting complex required for transport; HA: hemagglutinin; HCV: hepatitis C virus; HNF-1α: hepatocyte nuclear factor-1α; HRP: horseradish peroxidase; HSC70: heat shock cognate 70 kDa protein; IB: immunoblotting; IL: intracellular lumen; IP: immunoprecipitation; LAMP-2A: lysosome-associated membrane protein type 2A; LCS: low-complexity sequences; mAb: monoclonal antibody; MOI: multiplicity of infection; MVB: multivesicular bodies; NS: nonstructural protein; pAb: polyclonal antibody; PBS: phosphate-buffered saline; PCR: polymerase chain reaction; PLA: proximity ligation assay; PS: phosphatidylserine; RT: room temperature; TM: transmembrane; TSG: tumor susceptibility gene; VPS4A: vacuolar protein sorting-associated protein 4A; VPS4B: vacuolar protein sorting-associated protein 4

Acquisition of Complement Resistance through Incorporation of CD55/Decay-Accelerating Factor into Viral Particles Bearing Baculovirus GP64 ▿

A major obstacle to gene transduction by viral vectors is inactivation by human complement in vivo. One way to overcome this is to incorporate complement regulatory proteins, such as CD55/decay accelerating factor (DAF), into viral particles. Lentivirus vectors pseudotyped with the baculovirus envelope protein GP64 have been shown to acquire more potent resistance to serum inactivation and longer transgene expression than those pseudotyped with the vesicular stomatitis virus (VSV) envelope protein G. However, the molecular mechanisms underlying resistance to serum inactivation in pseudotype particles bearing the GP64 have not been precisely elucidated. In this study, we generated pseudotype and recombinant VSVs bearing the GP64. Recombinant VSVs generated in human cell lines exhibited the incorporation of human DAF in viral particles and were resistant to serum inactivation, whereas those generated in insect cells exhibited no incorporation of human DAF and were sensitive to complement inactivation. The GP64 and human DAF were detected on the detergent-resistant membrane and were coprecipitated by immunoprecipitation analysis. A pseudotype VSV bearing GP64 produced in human DAF knockdown cells reduced resistance to serum inactivation. In contrast, recombinant baculoviruses generated in insect cells expressing human DAF or carrying the human DAF gene exhibited resistance to complement inactivation. These results suggest that the incorporation of human DAF into viral particles by interacting with baculovirus GP64 is involved in the acquisition of resistance to serum inactivation