Shirit Einav, MD

Abstract

Global health is threatened by emerging viruses, many of which lack approved therapies and effective vaccines, including dengue, Ebola, and Venezuelan equine encephalitis. We previously reported that AAK1 and GAK, two of the four members of the understudied Numb-associated kinases (NAK) family, control intracellular trafficking of RNA viruses. Nevertheless, the role of BIKE and STK16 in viral infection remained unknown. Here, we reveal a requirement for BIKE, but not STK-16, in dengue virus (DENV) infection. BIKE mediates both early (postinternalization) and late (assembly/egress) stages in the DENV life cycle, and this effect is mediated in part by phosphorylation of a threonine 156 (T156) residue in the mu subunit of the adaptor protein (AP) 2 complex. Pharmacological compounds with potent anti-BIKE activity, including the investigational anticancer drug 5Z-7-oxozeaenol and more selective inhibitors, suppress DENV infection both in vitro and ex vivo. BIKE overexpression reverses the antiviral activity, validating that the mechanism of antiviral action is, at least in part, mediated by BIKE. Lastly, 5Z-7-oxozeaenol exhibits antiviral activity against viruses from three unrelated RNA viral families with a high genetic barrier to resistance. These findings reveal regulation of poorly understood stages of the DENV life cycle via BIKE signaling and establish a proof-of-principle that pharmacological inhibition of BIKE can be potentially used as a broad-spectrum strategy against acute emerging viral infections.

View details for DOI 10.1016/j.antiviral.2020.104966

View details for PubMedID 33137362

Abstract

Screening a series of 4-anilinoquinolines and 4-anilinoquinazolines enabled identification of potent novel inhibitors of dengue virus (DENV). Preparation of focused 4-anilinoquinoline/quinazoline scaffold arrays led to the identification of a series of high potency 6-substituted bromine and iodine derivatives. The most potent compound 6-iodo-4-((3,4,5-trimethoxyphenyl)amino)quinoline-3-carbonitrile (47) inhibited DENV infection with an EC50=79nM. Crucially, these compounds showed very limited toxicity with CC50 values >10M in almost all cases. This new promising series provides an anchor point for further development to optimize compound properties.

View details for DOI 10.1016/j.bmcl.2020.127284

View details for PubMedID 32631507

Abstract

There is an urgent need for prognostic assays to predict progression to severe dengue infection, which is a major global threat. While the majority of symptomatic dengue patients experience an acute febrile illness, 5-20% progress to severe infection associated with significant morbidity and mortality. Early monitoring and administration of supportive care reduce mortality and clinically usable biomarkers to predict severe dengue are needed. Here, we review recent discoveries of gene sets, anti-dengue antibody properties, and inflammatory markers with potential utility as predictors of disease progression. Upon larger scale validation and development of affordable sample-to-answer technologies, some of these biomarkers may be utilized to develop the first prognostic assay for improving patient care and allocating healthcare resources more effectively in dengue endemic countries.

View details for DOI 10.1016/j.tim.2019.12.003

View details for PubMedID 31982232

Abstract

There is a large global unmet need for effective countermeasures to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19). The development of novel antiviral drugs is expensive and too slow to meet the immediate need. The repurposing of drugs that are approved or are under advanced clinical investigation provides a cost- and time-effective therapeutic solution. This review summarizes the major repurposed approaches that have been proposed or are already being studied in clinical trials for COVID-19. Among these approaches are drugs that aim to reduce SARS-CoV-2 replication by targeting either viral enzymatic functions or cellular factors required for the viral life cycle. Drugs that modulate the host immune response to SARS-CoV-2 infection by boosting it to enhance viral clearance or by suppressing it to prevent excessive inflammation and tissue injury represent another category. Lastly, we discuss means to discover repurposed drugs and the ongoing challenges associated with the off-label use of existing drugs in the context of the COVID-19 outbreak.

View details for DOI 10.1021/acsinfecdis.0c00343

View details for PubMedID 32687696

View details for PubMedCentralID PMC7416635

Abstract

Eliciting broadly neutralizing antibodies (bNAbs) against the four dengue virus serotypes (DENV1-4) that are spreading into new territories is an important goal of vaccine design. To define bNAb targets, we characterized 28 antibodies belonging to expanded and hypermutated clonal families identified by transcriptomic analysis of single plasmablasts from DENV-infected individuals. Among these, we identified J9 and J8, two somatically related bNAbs that potently neutralized DENV1-4. Mutagenesis studies showed that the major recognition determinants of these bNAbs are in E protein domain I, distinct from the only known class of human bNAbs against DENV with a well-defined epitope. B cell repertoire analysis from acute-phase peripheral blood suggested that J9 and J8 followed divergent somatic hypermutation pathways, and that a limited number of mutations was sufficient for neutralizing activity. Our study suggests multiple B cell evolutionary pathways leading to DENV bNAbs targeting a new epitope that can be exploited for vaccine design.

View details for DOI 10.7554/eLife.52384

View details for PubMedID 31820734

Abstract

Previously, we reported the discovery of 3,6-disubstituted isothiazolo[4,3-b]pyridines as potent and selective cyclin G-associated kinase (GAK) inhibitors with promising antiviral activity. In this manuscript, the structure-activity relationship study was expanded to synthesis of isothiazolo[4,3-b]pyridines with modifications of the pyridine moiety. This effort led to the discovery of an isothiazolo[4,3-b]pyridine derivative with a 3,4-dimethoxyphenyl residue at position 5 that displayed low nanomolar GAK binding affinity and antiviral activity against dengue virus.

View details for DOI 10.1016/j.bmc.2019.115188

View details for PubMedID 31757682

View details for DOI 10.1016/j.celrep.2019.01.033

View details for Web of Science ID 000456952400005

Abstract

The endosomal sorting complex required for transport (ESCRT) machinery comprises five complexes that act sequentially to recruit and cluster transmembrane cargo proteins (ESCRT-0), drive membrane curving (ESCRT-I and II), catalyze fission of cargo-containing vesicles (ESCRT-III and VPS/VTA1), and disassemble and recycle the ESCRT-III complex (VPS/VTA1). Since interactions between ESCRT components and cellular or microbial proteins are typically weak, transient, and involve membrane proteins, they are often difficult to study by standard technologies. Here, we describe the utility of high-throughput protein-fragment complementation assays based on the reconstitution of a split luciferase reporter to screen for interactions between any protein and a library of ESCRT proteins in mammalian cells and provide a detailed protocol for these assays.

View details for DOI 10.1007/978-1-4939-9492-2_21

View details for PubMedID 31250310

Abstract

There are currently no approved drugs for the treatment of emerging viral infections, such as dengue and Ebola. Adaptor-associated kinase 1 (AAK1) is a cellular serine-threonine protein kinase that functions as a key regulator of the clathrin-associated host adaptor proteins and regulates the intracellular trafficking of multiple unrelated RNA viruses. Moreover, AAK1 is overexpressed specifically in dengue virus-infected but not bystander cells. Because AAK1 is a promising antiviral drug target, we have embarked on an optimization campaign of a previously identified 7-azaindole analogue, yielding novel pyrrolo[2,3- b]pyridines with high AAK1 affinity. The optimized compounds demonstrate improved activity against dengue virus both in vitro and in human primary dendritic cells and the unrelated Ebola virus. These findings demonstrate that targeting cellular AAK1 may represent a promising broad-spectrum antiviral strategy.

View details for DOI 10.1021/acs.jmedchem.9b00136

View details for PubMedID 31136173

Abstract

Cyclin G-associated kinase (GAK) is a cellular regulator of the clathrin-associated host adaptor proteins AP-1 and AP-2, which regulates intracellular trafficking of dengue virus during early and late stages of the viral lifecycle. Previously, the discovery of isothiazolo[4,3-b]pyridines as potent and selective GAK inhibitors with promising antiviral activity was reported. In this manuscript, the synthesis of isothiazolo[4,3-b]pyridines with a carbon-linked substituent at position 3 is described by the application of regioselective Suzuki and Sonogashira coupling reactions. A derivative with a 3,4-dimethoxyphenyl residue at position 3 demonstrates low nanomolar binding affinity for GAK and antiviral activity against dengue virus. These findings reveal that appropriate substitution of a phenyl moiety at position 3 of the scaffold can improve GAK binding affinity.

View details for PubMedID 30529544

Abstract

Viruses are obligate intracellular pathogens that are dependent on cellular machineries for their replication. Recent technological breakthroughs have facilitated reliable identification of host factors required for viral infections and better characterization of the virus-host interplay. While these studies have revealed cellular machineries that are uniquely required by individual viruses, accumulating data also indicate the presence of broadly required mechanisms. Among these overlapping cellular functions are components of intracellular membrane trafficking pathways. Here, we review recent discoveries focused on how viruses exploit intracellular membrane trafficking pathways to promote various stages of their life cycle, with an emphasis on cellular factors that are usurped by a broad range of viruses. We describe broadly required components of the endocytic and secretory pathways, the Endosomal Sorting Complexes Required for Transport pathway, and the autophagy pathway. Identification of such overlapping host functions offers new opportunities to develop broad-spectrum host-targeted antiviral strategies.

View details for PubMedID 30043139

Abstract

The high cost of drug development and the narrow spectrum of coverage typically provided by direct-acting antivirals limit the scalability of this antiviral approach. This review summarizes progress and challenges in the repurposing of approved kinase inhibitors as host-targeted broad-spectrum antiviral therapies.

View details for PubMedID 29148875

Abstract

There is an urgent need for strategies to combat dengue virus (DENV) infection; a major global threat. We reported that the cellular kinases AAK1 and GAK regulate intracellular trafficking of multiple viruses and that sunitinib and erlotinib, approved anticancer drugs with potent activity against these kinases, protect DENV-infected mice from mortality. Nevertheless, further characterization of the therapeutic potential and underlying mechanism of this approach is required prior to clinical evaluation. Here, we demonstrate that sunitinib/erlotinib combination achieves sustained suppression of systemic infection at approved dose in DENV-infected IFN-/ and IFN- receptor-deficient mice. Nevertheless, treatment with these blood-brain barrier impermeable drugs delays, yet does not prevent, late-onset paralysis; a common manifestation in this immunodeficient mouse model but not in humans. Sunitinib and erlotinib treatment also demonstrates efficacy in human primary monocyte-derived dendritic cells. Additionally, DENV infection induces expression of AAK1 transcripts, but not GAK, via single-cell transcriptomics, and these kinases are important molecular targets underlying the anti-DENV effect of sunitinib and erlotinib. Lastly, sunitinib/erlotinib combination alters inflammatory cytokine responses in DENV-infected mice. These findings support feasibility of repurposing sunitinib/erlotinib combination as a host-targeted antiviral approach and contribute to understanding its mechanism of antiviral action.

View details for PubMedID 29753658

Abstract

There is a large, global unmet need for the development of countermeasures to combat intracellular pathogens. The development of novel antimicrobials is expensive and slow and typically focuses on selective inhibition of proteins encoded by a single pathogen, thereby providing a narrow spectrum of coverage. The repurposing of approved drugs targeting host functions required for microbial infections represents a promising alternative. This review summarizes progress and challenges in the repurposing of approved drugs as host-targeted broad-spectrum agents for the treatment of intracellular pathogens. These strategies include targeting both cellular factors required for infection by various viruses, intracellular bacteria, and/or protozoa as well as factors that modulate the host immune response to these microbial infections. The repurposed approach offers complementary means to develop therapeutics against existing and emerging intracellular microbial threats.

View details for PubMedID 29298032

Abstract

siRNA approaches have demonstrated promise in treating viral infections in animal models, but poor delivery limits clinical application. In this issue of Cell Host & Microbe, Beloor etal. (2018) report that nose-to-brain delivery of viral-targeted siRNA cures mice from West Nile virus encephalitis, with potential implications for human infection.

View details for PubMedID 29649437

Abstract

The high cost of drug development and the narrow spectrum of coverage typically provided by direct-acting antivirals limit the scalability of this antiviral approach. This review summarizes progress and challenges in the repurposing of approved kinase inhibitors as host-targeted broad-spectrum antiviral therapies.

View details for DOI 10.1089/dna.2017.4033

View details for PubMedCentralID PMC5804095

Abstract

The discovery of how a pathogen invades a cell requires one to determine which host cell receptors are exploited. This determination is a challenging problem because the receptor is invariably a membrane protein, which represents an Achilles heel in proteomics. We have developed a universal platform for high-throughput expression and interaction studies of membrane proteins by creating a microfluidic-based comprehensive human membrane protein array (MPA). The MPA is, to our knowledge, the first of its kind and offers a powerful alternative to conventional proteomics by enabling the simultaneous study of 2,100 membrane proteins. We characterized direct interactions of a whole nonenveloped virus (simian virus 40), as well as those of the hepatitis delta enveloped virus large form antigen, with candidate host receptors expressed on the MPA. Selected newly discovered membrane protein-pathogen interactions were validated by conventional methods, demonstrating that the MPA is an important tool for cellular receptor discovery and for understanding pathogen tropism.

View details for DOI 10.1073/pnas.1518698113

View details for Web of Science ID 000374393800043

View details for PubMedID 27044079

View details for PubMedCentralID PMC4843447

Abstract

Hepatitis C virus (HCV) is an oncogenic virus associated with the onset of hepatocellular carcinoma (HCC). The present study investigated the possible link between HCV infection and Netrin-1, a ligand for dependence receptors that sustains tumorigenesis, in particular in inflammation-associated tumors. We show that Netrin-1 expression is significantly elevated in HCV+ liver biopsies compared to hepatitis B virus (HBV+) and uninfected samples. Furthermore, Netrin-1 was upregulated in all histological stages of HCV+ hepatic lesions, from minimal liver fibrosis to cirrhosis and HCC, compared to histologically matched HCV- tissues. Both cirrhosis and HCV contributed to the induction of Netrin-1 expression, whereas anti-HCV treatment resulted in a reduction of Netrin-1 expression. In vitro, HCV increased the level and translation of Netrin-1 in a NS5A-La-related protein 1 (LARP1)-dependent fashion. Knockdown and forced expression experiments identified the receptor uncoordinated receptor-5 (UNC5A) as an antagonist of the Netrin-1 signal, though it did not affect the death of HCV-infected cells. Netrin-1 enhanced infectivity of HCV particles and promoted viral entry by increasing the activation and decreasing the recycling of the epidermal growth factor receptor (EGFR), a protein that is dysregulated in HCC. Netrin-1 and HCV are, therefore, reciprocal inducers in vitro and in patients, as seen from the increase in viral morphogenesis and viral entry, both phenomena converging toward an increase in the level of infectivity of HCV virions. This functional association involving a cancer-related virus and Netrin-1 argues for evaluating the implication of UNC5 receptor ligands in other oncogenic microbial species.

View details for DOI 10.1371/journal.pbio.1002421

View details for Web of Science ID 000373038200035

View details for PubMedCentralID PMC4816328

View details for DOI 10.1126/science.348.6242.1437-b

View details for PubMedID 26113710

Abstract

Cyclin-G associated kinase (GAK) emerged as a promising drug target for the treatment of viral infections. However, no potent and selective GAK inhibitors have been reported in the literature to date. This paper describes the discovery of isothiazolo[5,4-b]pyridines as selective GAK inhibitors, with the most potent congeners displaying low nanomolar binding affinity for GAK. Co-crystallization experiments revealed that these compounds behaved as classic type I ATP-competitive kinase inhibitors. In addition, we have demonstrated that these compounds exhibit a potent activity against hepatitis C virus (HCV) by inhibiting two temporally distinct steps in the HCV lifecycle (i.e. viral entry and assembly). Hence, these GAK inhibitors represent chemical probes to study GAK function in different disease areas where GAK has been implicated (including viral infection, cancer and Parkinson's disease).

View details for DOI 10.1021/jm501759m

View details for Web of Science ID 000353602200009

View details for PubMedID 25822739

Abstract

Isothiazolo[4,3-b]pyridines are known to be endowed with potent affinity for cyclin G associated kinase (GAK). In this paper, we expanded the structure-activity relationship study by broadening the structural variety at position 3 of the isothiazolo[4,3-b]pyridine scaffold. The most potent GAK ligands (displaying Kd values of less than 100 nM) within this series carry an alkoxy group at position 3 of the central scaffold. Unfortunately, these ligands display only modest antiviral activity against the hepatitis C virus.

View details for DOI 10.1039/c5md00229j

View details for Web of Science ID 000360639300011

View details for PubMedCentralID PMC4763718

Abstract

Chronic HCV infection has been implicated in the induction and maintenance of B-cell lymphomas. The strongest evidence for this comes from clinical observations of tumor regressions upon anti-viral treatments. Here we used multiple methods to test the hypothesis that the expansion of HCV-specific B cells gives rise to lymphomas. We obtained lymphoma tissues from HCV-infected lymphoma patients, including some that later regressed upon anti-viral treatments. We expressed the lymphoma B-cell receptors (BCRs) as soluble IgGs and membrane IgMs, and analyzed their reactivity with HCV proteins and with HCV virions. We confirmed previous reports that HCV-associated lymphomas use a restricted immunoglobulin variable region (V) gene repertoire. However, we found no evidence for their binding to the HCV antigens. We conclude that most lymphomas of HCV-infected patients do not arise from B cells aimed at eliminating the virus.

View details for DOI 10.1182/blood-2013-10-532895

View details for PubMedID 24449209

Abstract

Hepatitis C Virus (HCV) is a leading cause of liver disease and represents a significant public health challenge. Treatments for this disease are inadequate and improved antiviral therapies are necessary. Several such antivirals are in development, most of which target the well-characterized NS3 protease or the NS5B polymerase. In contrast, the nonstructural 4B (NS4B) protein, though essential for HCV RNA replication, has been the subject of few pharmacological studies. One of the functions ascribed to this protein is the ability to form intracellular membrane-associated foci (MAF), which are believed to be related to the sites of viral replication. Here, we report the identification of a small molecule that inhibits HCV replication and disrupts the organization of these MAF. Genetic analysis links the compound's mode of action to the NS4B gene product, and transient transfections of NS4B-GFP demonstrate that treatment with this compound can lead to the formation of novel elongated assemblies of NS4B. Furthermore, an in vitro dynamic light scattering assay provides evidence that the second amphipathic helix of NS4B may be the target of the drug. Our results demonstrate that this molecule represents a new potential class of HCV inhibitors and also provides us with a useful tool for studying the HCV life cycle.

View details for DOI 10.1016/j.antiviral.2010.03.013

View details for PubMedID 20363257

Abstract

We recently identified a compound, clemizole hydrochloride, that inhibits NS4B's RNA binding and hepatitis C virus (HCV) replication. Although significant, clemizole's antiviral effect is moderate (50% effective concentration of 8 microM against an HCV genotype 2a clone). We hypothesized that the combination of clemizole with other anti-HCV agents can increase the antiviral effect over that achieved with each drug alone and could also decrease the emergence of viral resistance.Luciferase reporter-linked HCV replication assays were used to study the antiviral effects of drug combinations that included clemizole. Data were analyzed using Loewe additivity and Bliss independence models for synergy, and resistance studies were performed using HCV colony formation assays.Clemizole's antiviral effect was highly synergistic with the HCV protease inhibitors SCH503034 and VX950, without toxicity. In contrast, combinations of clemizole with either interferon, ribavirin, or the nucleoside (NM283) and nonnucleoside (HCV796) HCV polymerase inhibitors were additive. Furthermore, combination of clemizole with SCH503034 decreased the frequency of drug-resistant mutants, compared with treatment with either drug alone. Finally, no cross-resistance to clemizole of SCH503034-resistant mutants (or vice versa) was observed.Clemizole can yield high-level synergy with the protease inhibitor class. Inclusion of clemizole in future anti-HCV cocktails can represent an attractive paradigm for increasing current virologic response rates.

View details for DOI 10.1086/653080

View details for Web of Science ID 000278322300008

View details for PubMedCentralID PMC3008401

Abstract

We recently identified a compound, clemizole hydrochloride, that inhibits NS4B's RNA binding and hepatitis C virus (HCV) replication. Although significant, clemizole's antiviral effect is moderate (50% effective concentration of 8 microM against an HCV genotype 2a clone). We hypothesized that the combination of clemizole with other anti-HCV agents can increase the antiviral effect over that achieved with each drug alone and could also decrease the emergence of viral resistance.Luciferase reporter-linked HCV replication assays were used to study the antiviral effects of drug combinations that included clemizole. Data were analyzed using Loewe additivity and Bliss independence models for synergy, and resistance studies were performed using HCV colony formation assays.Clemizole's antiviral effect was highly synergistic with the HCV protease inhibitors SCH503034 and VX950, without toxicity. In contrast, combinations of clemizole with either interferon, ribavirin, or the nucleoside (NM283) and nonnucleoside (HCV796) HCV polymerase inhibitors were additive. Furthermore, combination of clemizole with SCH503034 decreased the frequency of drug-resistant mutants, compared with treatment with either drug alone. Finally, no cross-resistance to clemizole of SCH503034-resistant mutants (or vice versa) was observed.Clemizole can yield high-level synergy with the protease inhibitor class. Inclusion of clemizole in future anti-HCV cocktails can represent an attractive paradigm for increasing current virologic response rates.

View details for DOI 10.1086/653080

View details for PubMedID 20486856

View details for PubMedCentralID PMC3008401

Abstract

We have used multiplexed high-throughput sequencing to characterize changes in small RNA populations that occur during viral infection in animal cells. Small RNA-based mechanisms such as RNA interference (RNAi) have been shown in plant and invertebrate systems to play a key role in host responses to viral infection. Although homologs of the key RNAi effector pathways are present in mammalian cells, and can launch an RNAi-mediated degradation of experimentally targeted mRNAs, any role for such responses in mammalian host-virus interactions remains to be characterized. Six different viruses were examined in 41 experimentally susceptible and resistant host systems. We identified virus-derived small RNAs (vsRNAs) from all six viruses, with total abundance varying from "vanishingly rare" (less than 0.1% of cellular small RNA) to highly abundant (comparable to abundant micro-RNAs "miRNAs"). In addition to the appearance of vsRNAs during infection, we saw a number of specific changes in host miRNA profiles. For several infection models investigated in more detail, the RNAi and Interferon pathways modulated the abundance of vsRNAs. We also found evidence for populations of vsRNAs that exist as duplexed siRNAs with zero to three nucleotide 3' overhangs. Using populations of cells carrying a Hepatitis C replicon, we observed strand-selective loading of siRNAs onto Argonaute complexes. These experiments define vsRNAs as one possible component of the interplay between animal viruses and their hosts.

View details for DOI 10.1371/journal.ppat.1000764

View details for PubMedID 20169186

Abstract

Hepatitis C virus (HCV) is an important cause of chronic liver disease and is complicated by hepatocellular carcinoma (HCC). Mechanisms whereby the virus promotes cellular transformation are poorly understood. We hypothesized that the guanosine triphosphatase activity encoded in the HCV NS4B protein's nucleotide binding motif (NBM) might play a role in the transformation process. Here we report that NS4B can transform NIH-3T3 cells, leading to tumor formation in vivo. This transformation was independent of co-transfection with activated Ha-ras. Detailed analyses of NS4B mutants revealed that this transforming activity could be progressively inhibited and completely abrogated by increasing genetic impairment of the NS4B nucleotide binding motif.NS4B has in vitro and in vivo tumorigenic potential, and the NS4B transforming activity is indeed mediated by its NBM. Moreover, our results suggest that pharmacological inhibition of the latter might inhibit not only HCV replication but also the associated HCC.

View details for DOI 10.1002/hep.22108

View details for PubMedID 18081150

Abstract

Like other viruses, productive hepatitis C virus (HCV) infection depends on certain critical host factors. We have recently shown that an interaction between HCV nonstructural protein NS5A and a host protein, TBC1D20, is necessary for efficient HCV replication. TBC1D20 contains a TBC (Tre-2, Bub2, and Cdc16) domain present in most known Rab GTPase-activating proteins (GAPs). The latter are master regulators of vesicular membrane transport, as they control the activity of membrane-associated Rab proteins. To better understand the role of the NS5A-TBC1D20 interaction in the HCV life cycle, we used a biochemical screen to identify the TBC1D20 Rab substrate. TBC1D20 was found to be the first known GAP for Rab1, which is implicated in the regulation of anterograde traffic between the endoplasmic reticulum and the Golgi complex. Mutation of amino acids implicated in Rab GTPase activation by other TBC domain-containing GAPs abrogated the ability of TBC1D20 to activate Rab1 GTPase. Overexpression of TBC1D20 blocked the transport of exogenous vesicular stomatitis virus G protein from the endoplasmic reticulum, validating the involvement of TBC1D20 in this pathway. Rab1 depletion significantly decreased HCV RNA levels, suggesting a role for Rab1 in HCV replication. These results highlight a novel mechanism by which viruses can hijack host cell machinery and suggest an attractive model whereby the NS5A-TBC1D20 interaction may promote viral membrane-associated RNA replication.

View details for DOI 10.1074/jbc.M705221200

View details for PubMedID 17901050

Abstract

Hepatitis C virus (HCV) is a major cause of viral hepatitis. There is no effective therapy for most patients. We have identified a nucleotide binding motif (NBM) in one of the virus's nonstructural proteins, NS4B. This structural motif binds and hydrolyzes GTP and is conserved across HCV isolates. Genetically disrupting the NBM impairs GTP binding and hydrolysis and dramatically inhibits HCV RNA replication. These results have exciting implications for the HCV life cycle and novel antiviral strategies.

View details for PubMedID 15452248

Abstract

Prenylation is a site-specific lipid modification of proteins. Although first described for a variety of cellular proteins, it has become apparent that viruses can also make use of this post-translational modification provided by their host cells. Depriving a virus access to prenylation can have dramatic effects on the targeted virus's life cycle. Selective pharmacological inhibitors of prenylating enzymes have been developed and shown to have potent antiviral effects in both in vitro and in vivo systems. Because prenylation inhibitors target a host cell function, are available in oral form and are surprisingly well tolerated in human trials, these compounds represent an attractive new class of antiviral agents with potential for broad-spectrum activity. After a brief outline of host cell prenylation pathways, we review below the development of prenylation inhibition as an antiviral strategy applied to a prototype target, hepatitis delta virus (HDV), and discuss the potential application of prenylation inhibitors to a broad range of other viruses.

View details for DOI 10.1093/jac/dkg490

View details for PubMedID 14613953

Abstract

The prevalence of chronic hepatitis C virus (HCV) infection among various groups of immunosuppressed patients is high. These groups include patients co-infected with human immunodeficiency virus (HIV), recipients of organ transplants, and those with hypogammaglobulinemia. The liver disease in the immunosuppressed host is typically severe with an unusually rapid progression to cirrhosis. This is somewhat paradoxical, as the classical model for HCV-induced liver disease assumes that cell-mediated immune responses induce liver injury. It is likely that a combination of viral-related factors and host-related factors plays a role in this accelerated natural history of HCV. Data are accumulating in immunocompromised hosts that address the immunopathogenesis of liver injury, although there are still fundamental gaps in our understanding of this process. In this review, we will focus on our current understanding of the mechanisms of liver injury and how it relates to the accelerated liver disease progression in immunocompromised hosts.

View details for PubMedID 12220245

Abstract

The role of complement C3 in mediating systemic lupus erythematosus (SLE) was examined using a double-knockout C3(null)C4(null) Fas (CD95)-deficient mouse model. Results from this study reveal significant lymphadenopathy, splenomegaly, elevated titers of anti-nuclear Abs and anti-dsDNA Abs, an increased number of anti-dsDNA-producing cells in ELISPOT assay, as well as severe glomerulonephritis in the double-deficient mice. Based on these clinical, serological, and histological parameters, we find that autoimmune disease in the double-knockout group is similar in severity to that in C4(null) lpr mice, but not to that in C3(null) lpr mice. The development of severe SLE in the absence of both classical and alternative complement pathways suggests that it is the absence of C4, and not the presence of C3, that is critical in SLE pathogenesis. Thus, complement C4 provides an important protective role against the development of SLE.

View details for Web of Science ID 000173429300010

View details for PubMedID 11801636