Aberrant methylation of the promoter, P2, and the first exon, E1, regions of the tumor suppressor gene RASSF1A have been associated with HCC, albeit with poor specificity. This study analyzed the methylation profiles of P1, P2, and E1 regions of the gene to identify the region of which methylation most specifically corresponds to HCC and to evaluate the potential of this methylated region as a biomarker in urine for HCC screening.
Endoplasmic reticulum (ER)-resident glucosidases I and II sequentially trim the three terminal glucose moieties on the N-linked glycans attached to nascent glycoproteins. These reactions are the first steps of N-linked glycan processing and are essential for proper folding and function of many glycoproteins. Because most of the viral envelope glycoproteins contain N-linked glycans, inhibition of ER glucosidases with derivatives of 1-deoxynojirimycin, i.e. iminosugars, efficiently disrupts the morphogenesis of a broad-spectrum of enveloped viruses. However, like viral envelope proteins, the cellular receptors of many viruses are also glycoproteins. It is, therefore, possible that inhibition of ER glucosidases not only compromises virion production, but may also disrupt expression and function of viral receptors and thus inhibit virus entry into host cells. Indeed, we demonstrated herein that iminosugar treatment altered the N-linked glycan structure of angiotensin-I converting enzyme 2 (ACE2), which did not affect its expression on cell surface and binding of severe acute respiratory syndrome coronavirus (SARS-CoV) spike glycoprotein. However, alteration of N-linked glycans of ACE2 impairs its ability to support the transduction of SARS-CoV and human coronavirus NL63 (HCoV-NL63) spike glycoprotein-pseudotyped lentiviral particles by disruption of the viral envelope protein triggered membrane fusion. Hence, in addition to reducing the production of infectious virions, inhibition of ER glucosidases also impairs the entry of selected viruses via a post receptor binding mechanism.
Sadat et al reported in the 2014 April 24 issue of New England Journal of Medicine that patients genetically deficient in the gene encoding mannosyl-oligosaccharide glucosidase (MOGS), also known as endoplasmic reticulum (ER) glucosidase I, manifested a severe hypogammaglobulinemia without clinical evidence of an infectious diathesis. This paradox phenomenon is, at least in part, because the impaired N-linked glycan processing of the patients compromises their ability to support efficient replication and cellular entry of viruses. This finding unambiguously validates ER glucosidases as valuable targets for antiviral agents against a broad-spectrum of enveloped viruses.
IFNs are a family of cytokines that are essential for the antiviral response in vertebrates. Not surprisingly, viruses have adapted to encode virulence factors to cope with the IFN response. Intriguingly, we show here that all three types of interferons, IFN-?, IFN-?, and IFN-?, efficiently promote infection by a human coronavirus, HCoV-OC43, one of the major etiological agents of common cold, through the induction of IFN-inducible transmembrane (IFITM) proteins. IFITMs typically exert their antiviral function by inhibiting the entry of a broad spectrum of viruses into their host cells, presumably by trapping and degrading invading virions within the endocytic compartments. In contrast, HCoV-OC43 uses IFN-induced human IFITM2 or IFITM3 as an entry factor to facilitate its infection of host cells. Reverse genetics analyses suggest that the structural motifs critical for the IFITM proteins' enhancement of HCoV-OC43 infection are distinct from those required for inhibiting infection by other viruses. We also present evidence showing that IFITM family members work as homo- and hetero-oligomers to modulate virus entry. The observed enhancement of HCoV-OC43 infection by IFNs may underlie the propensity of the virus to invade the lower respiratory tract under inflammatory conditions.
Virus infection of host cells is sensed by innate pattern recognition receptors (PRRs) and induces production of type I interferons (IFNs) and other inflammatory cytokines. These cytokines orchestrate the elimination of the viruses but are occasionally detrimental to the hosts. The outcomes and pathogenesis of viral infection are largely determined by the specific interaction between the viruses and their host cells. Therefore, compounds that either inhibit viral infection or modulate virus-induced cytokine response should be considered as candidates for managing virus infection. The aim of the study was to identify compounds in both categories, using a single cell-based assay. Our screening platform is a HEK293 cell-based reporter assay where the expression of a firefly luciferase is under the control of a human IFN-? promoter. We have demonstrated that infection of the reporter cell line with a panel of RNA viruses activated the reporter gene expression that correlates quantitatively with the levels of virus replication and progeny virus production, and could be inhibited in a dose-dependent manner by known antiviral compound or inhibitors of PRR signal transduction pathways. Using Dengue virus as an example, a pilot screening of a small molecule library consisting of 26,900 compounds proved the concept that the IFN-? promoter reporter assay can serve as a convenient high throughput screening platform for simultaneous discovery of antiviral and innate immune response modulating compounds. A representative antiviral compound from the pilot screening, 1-(6-ethoxybenzo[d]thiazol-2-yl)-3-(3-methoxyphenyl) urea, was demonstrated to specifically inhibit several viruses belonging to the family of flaviviridae.
Patients with inflammatory bowel disease have higher proportions of immunoglobulin G (IgG) antibodies lacking N-galactose, also called agalactosyl IgG, in their serum. Such agalactosyl IgGs have been associated with disease activity and the immunogenicity of biologics. The aim was to describe the relationship between circulating levels of a subset of agalactosyl IgGs (anti-?-Gal) and Crohns disease (CD) phenotypes.
Covalently closed circular DNA (cccDNA) of hepadnaviruses exists as an episomal minichromosome in the nucleus of infected hepatocyte and serves as the transcriptional template for viral mRNA synthesis. Elimination of cccDNA is the prerequisite for either a therapeutic cure or immunological resolution of HBV infection. Although accumulating evidence suggests that inflammatory cytokines-mediated cure of virally infected hepatocytes does occur and plays an essential role in the resolution of an acute HBV infection, the molecular mechanism by which the cytokines eliminate cccDNA and/or suppress its transcription remains elusive. This is largely due to the lack of convenient cell culture systems supporting efficient HBV infection and cccDNA formation to allow detailed molecular analyses. In this study, we took the advantage of a chicken hepatoma cell line that supports tetracycline-inducible duck hepatitis B virus (DHBV) replication and established an experimental condition mimicking the virally infected hepatocytes in which DHBV pregenomic (pg) RNA transcription and DNA replication are solely dependent on cccDNA. This cell culture system allowed us to demonstrate that cccDNA transcription required histone deacetylase activity and IFN-? induced a profound and long-lasting suppression of cccDNA transcription, which required protein synthesis and was associated with the reduction of acetylated histone H3 lysine 9 (H3K9) and 27 (H3K27) in cccDNA minichromosomes. Moreover, IFN-? treatment also induced a delayed response that appeared to accelerate the decay of cccDNA. Our studies have thus shed light on the molecular mechanism by which IFN-? noncytolytically controls hepadnavirus infection.
Chronic hepatitis B remains a substantial public health burden affecting approximately 350 million people worldwide, causing cirrhosis and liver cancer, and about 1 million people die each year from hepatitis B and its complications. Hepatitis B is caused by hepatitis B virus (HBV) infection. As an essential component of the viral life cycle, HBV covalently closed circular DNA (cccDNA) is synthesized and maintained at low copy numbers in the nucleus of infected hepatocytes, and serves as the transcription template for all viral RNAs. Therefore, cccDNA is responsible for the establishment of viral infection and persistence. The presence and longevity of cccDNA may also explain the limitations of current antiviral therapy for hepatitis B. Thus, understanding the mechanisms underlying cccDNA formation and regulation is critical in understanding the HBV pathogenesis and finding a cure for hepatitis B. Here we describe a protocol for HBV cccDNA extraction and detection in detail. The procedure includes two major steps: (1) HBV cccDNA extraction by Hirt protein-free DNA extraction method and (2) HBV cccDNA detection by Southern blot analysis. The method is straightforward and reliable for cccDNA assay with cell culture samples, and it is useful for both HBV molecular biology and antiviral research.
The zinc finger antiviral protein (ZAP) is a mammalian host restriction factor that inhibits the replication of a variety of RNA viruses, including retroviruses, alphaviruses and filoviruses, through interaction with the ZAP-responsive elements (ZRE) in viral RNA, and recruiting the exosome to degrade RNA substrate. Hepatitis B virus (HBV) is a pararetrovirus that replicates its genomic DNA via reverse transcription of a viral pregenomic (pg) RNA precursor. Here, we demonstrate that the two isoforms of human ZAP (hZAP-L and -S) inhibit HBV replication in human hepatocyte-derived cells through posttranscriptional down-regulation of viral pgRNA. Mechanistically, the zinc finger motif-containing N-terminus of hZAP is responsible for the reduction of HBV RNA, and the integrity of the four zinc finger motifs is essential for ZAP to bind to HBV RNA and fulfill its antiviral function. The ZRE sequences conferring the susceptibility of viral RNA to ZAP-mediated RNA decay were mapped to the terminal redundant region (nt 1820-1918) of HBV pgRNA. In agreement with its role as a host restriction factor and as an innate immune mediator for HBV infection, ZAP was upregulated in cultured primary human hepatocytes and hepatocyte-derived cells upon IFN-? treatment or IPS-1 activation, and in the livers of hepatitis B patients during immune active phase. Knock down of ZAP expression increased the level of HBV RNA and partially attenuated the antiviral effect elicited by IPS-1 in cell cultures. In summary, we demonstrated that ZAP is an intrinsic host antiviral factor with activity against HBV through down-regulation of viral RNA, and that ZAP plays a role in the innate control of HBV replication. Our findings thus shed light on virus-host interaction, viral pathogenesis, and antiviral approaches.
Endoplasmic reticulum (ER)-resident ?-glucosidases I and II sequentially trim the three terminal glucose moieties on N-linked glycans attached to nascent glycoproteins. These reactions are the first steps of N-linked glycan processing and are essential for proper folding and function of many glycoproteins. Because most viral envelope glycoproteins contain N-linked glycans, inhibition of ER ?-glucosidases with derivatives of 1-deoxynojirimycin (DNJ) or castanospermine (CAST), two well-studied pharmacophores of ?-glucosidase inhibitors, efficiently disrupts the morphogenesis of a broad spectrum of enveloped viruses. Moreover, both DNJ and CAST derivatives have been demonstrated to prevent the death of mice infected with several distinct flaviviruses and filoviruses and suppress the multiplication of several other species of viruses in infected animals. N-Butyl derivative of DNJ (NB-DNJ) and 6 O-bytanoyl prodrug of CAST (Bu-CAST) have been evaluated in human clinical trials for their antiviral activities against human immunodeficiency virus and hepatitis C virus, and there is an ongoing trial of treating dengue patients with Bu-CAST. This article summarizes the current status of ER ?-glucosidase-targeted antiviral therapy and proposes strategies for development of more efficacious and specific ER ?-glucosidase inhibitors as broad-spectrum, drug resistance-refractory antiviral therapeutics. These host function-targeted, broad-spectrum antiviral agents do not rely on time-consuming etiologic diagnosis, and should therefore be particularly promising in the management of viral hemorrhagic fever and respiratory tract viral infections, medical conditions that can be caused by many different enveloped RNA viruses, with a short window for medical intervention.
Chronic hepatitis B virus (HBV) infection, a serious public health problem leading to cirrhosis and hepatocellular carcinoma, is currently treated with either pegylated alpha interferon (pegIFN-?) or one of the five nucleos(t)ide analogue viral DNA polymerase inhibitors. However, neither pegIFN-? nor nucleos(t)ide analogues are capable of reliably curing the viral infection. In order to develop novel antiviral drugs against HBV, we established a cell-based screening assay by using an immortalized mouse hepatocyte-derived stable cell line supporting a high level of HBV replication in a tetracycline-inducible manner. Screening of a library consisting of 26,900 small molecules led to the discovery of a series of sulfamoylbenzamide (SBA) derivatives that significantly reduced the amount of cytoplasmic HBV DNA. Structure-activity relationship studies have thus far identified a group of fluorine-substituted SBAs with submicromolar antiviral activity against HBV in human hepatoma cells. Mechanistic analyses reveal that the compounds dose dependently inhibit the formation of pregenomic RNA (pgRNA)-containing nucleocapsids of HBV but not other animal hepadnaviruses, such as woodchuck hepatitis virus (WHV) and duck hepatitis B virus (DHBV). Moreover, heterologous genetic complementation studies of capsid protein, DNA polymerase, and pgRNA between HBV and WHV suggest that HBV capsid protein confers sensitivity to the SBAs. In summary, SBAs represent a novel chemical entity with superior activity and a unique antiviral mechanism and are thus warranted for further development as novel antiviral therapeutics for the treatment of chronic hepatitis B.
Hepatocellular carcinoma (HCC) is a primary cancer of the liver that is predominantly the result of infection with a hepatotropic virus such as hepatitis B virus or hepatitis C virus. As liver cancer is often asymptomatic, the development of sensitive noninvasive biomarkers is needed for early detection and improved survival.
Novel N-alkyldeoxynojirimycins (NADNJs) based on our previous lead 3 were designed, synthesized and tested in metabolic assays and in virus cultures. NADNJs containing terminal tertiary benzamide, sulfonamide, urea, and oxazolidinone moieties were discovered to have improved metabolic stability compared to 3, while maintaining submicromolar EC50 against BVDV and Tacaribe virus; and low cytotoxicity.
Hepatocellular carcinoma (HCC) is the third most common cause of cancer fatalities worldwide, with limited treatment options and five year survival rates of between <5 and 15%. To address this medical need, we conducted a screen of a drug-like small molecule library for HCC-selective cytotoxins. We report here the identification of a disubstituted aminothiazole termed HBF-0079, with remarkable selective toxicity for HCC-derived cell lines versus non-HCC liver lines and most other cancer lines. HBF-0079 caused irreversible growth arrest and apoptosis of the HCC lines Huh7, Hep3B, HepaRG as well as the hepatoblastoma line HepG2, with CC?? values from ?0.7-7.7 µM, while more than 45 µM was needed to achieve CC?? values for the immortalized normal hepatocyte lines THLE-2 and PH5CH. Of the sixty cancer lines from the National Cancer Institute panel, only five exhibited >50% growth inhibition by HBF-0079. In Huh7 cells, HBF-0079 induced cell cycle arrest in G1 and concomitant apoptosis, and its effects were irreversible after removal of the compound. These observations corroborate a loss of AKT phosphorylation at the mTORC2-targeted residue S473, with concurrent loss of phosphorylation of the mTORC1 targets SK6 and 4EBP1 in Huh7 but not PH5CH cells. Finally, growth of Hep3B-derived tumors in a murine xenograft model was significantly repressed by the compound through either systemic or intratumoral administration of formulated HBF-0079. The potential for development of this drug candidate is discussed.
There are now seven nucleoside/tide analogues, along with interferon-?, that are approved by the FDA for the management of chronic hepatitis B virus (HBV) infection, a disease affecting hundreds of millions of people worldwide. These medications, however, are limited in usefulness, and significant side effects and the emergence of viral escape mutants make the development of novel and updated therapeutics a pressing need in the treatment of HBV. With this in mind, a library containing 2000 compounds already known to be safe in both humans and mice with known mechanisms of action in mammalian cells were tested for the possibility of either antiviral activity against HBV or selective toxicity in HBV producing cell lines. A modified real-time immune-absorbance-polymerase chain reaction (IA-PCR) assay was developed for this screen, utilizing cells that produce and secrete intact HBV virions. In this procedure, viral particles are first captured by an anti-HBs antibody immobilized on a plate. The viral load is subsequently assessed by real-time PCR directly on captured particles. Using this assay, eight compounds were shown to consistently reduce the amount of secreted HBV viral particles in the culture medium under conditions that had no detectable impact on cell viability. Two compounds, proparacaine and chlorophyllide, were shown to reduce HBV levels 4- to 6-fold with an IC?? of 1 and 1.5 ?M, respectively, and were selected for further study. The identification of these compounds as promising antiviral drug candidates against HBV, despite a lack of previous recognition of HBV antiviral activity, supports the validity and utility of testing known compounds for "off-pathogen target" activity against HBV, and also validates this IA-PCR assay as an important tool for the detection of anti-viral activity against enveloped viruses.
Novel N-alkyldeoxynojirimycins (NADNJs) with two hydrophobic groups attached to a nitrogen linker on the alkyl chain were designed. A novel NADNJ containing a terminal tertiary carboxamide moiety was discovered that was a potent inhibitor against BVDV. Further optimization resulted in a structurally more stable lead compound 24 with a submicromolar EC50 against BVDV, Dengue, and Tacaribe; and low cytotoxicity.
Chronic hepatitis B can currently be medically managed with either pegylated interferon-alpha (pegIFN-?) or one of the five nucleos(t)ide analog Direct Acting Antivirals (DAAs) that inhibit the hepatitis B virus (HBV) DNA polymerase. While pegIFN-? is effective in approximately one-third of the treated patients, the polymerase inhibitors significantly reduce viral load in the vast majority of those treated. However, neither pegIFN-? nor nucleosi(t)de analogs are capable of reliably eliminating the virus and achieving a cure. Moreover, the interferons and polymerase inhibitors are recommended by US, European and Asian professional society practice guidelines for use in only a subset of those infected with HBV. This subset is the population with the greatest levels of circulating viral DNA and abnormal liver function. Although this is the population at the highest risk for cirrhosis and liver cancer, those who fall outside the treatment guidelines, with low levels of viral replication and normal serum ALTs, may also benefit from antiviral therapy. The questions are thus: are new classes of drugs needed to manage chronic hepatitis B? Is a cure possible? Is a cure even necessary? It is therefore important to define the meaning of a cure and determine what the goals of new therapies should be. In this article, we address those questions and propose two operational definitions of medically attainable cures. The first is a "functional cure" based on the clinical outcome, in which the patients life expectancy becomes the same as that of an individual who has resolved his HBV infection without therapy. Because such an outcome cannot be measured over the short term, we also define an "apparent virological cure," based on the stable off-drug suppression of HBV viremia and antigenemia and the normalization of ALTs and other laboratory tests. We suggest that such a virological cure should be the goal of future therapeutics in all patients with chronic hepatitis B. The extent to which a virological cure predicts a functional cure will only be determined by long-term follow-up.
Host cellular endoplasmic reticulum ?-glucosidases I and II are essential for the maturation of viral glycosylated envelope proteins that use the calnexin mediated folding pathway. Inhibition of these glycan processing enzymes leads to the misfolding and degradation of these viral glycoproteins and subsequent reduction in virion secretion. We previously reported that, CM-10-18, an imino sugar ?-glucosidase inhibitor, efficiently protected the lethality of dengue virus infection of mice. In the current study, through an extensive structure-activity relationship study, we have identified three CM-10-18 derivatives that demonstrated superior in vitro antiviral activity against representative viruses from four viral families causing hemorrhagic fever. Moreover, the three novel imino sugars significantly reduced the mortality of two of the most pathogenic hemorrhagic fever viruses, Marburg virus and Ebola virus, in mice. Our study thus proves the concept that imino sugars are promising drug candidates for the management of viral hemorrhagic fever caused by variety of viruses.
Using comparative glycoproteomics, we have previously identified a glycoprotein that is altered in both amount and glycosylation as a function of liver cirrhosis. The altered glycoprotein is an agalactosylated (G0) immunoglobulin G molecule (IgG) that recognizes the heterophilic alpha-gal epitope. Since the alpha gal epitope is found on gut enterobacteria, it has been hypothesized that anti-gal antibodies are generated as a result of increased bacterial exposure in patients with liver disease.
Serine protease inhibitor Kazal (SPIK) is an inflammatory protein whose levels are elevated in numerous cancers. However, the role of this protein in cancer development is unknown. We have recently found that SPIK suppresses serine protease-dependent cell apoptosis. Here, we report that anti-SPIK antibodies can co-immmunoprecipitate serine protease granzyme A (GzmA), a cytolytic granule secreted by cytotoxic T lymphocytes and natural killer cells during immune surveillance, and that SPIK suppresses GzmA-induced cell apoptosis. Deletion studies show that the C3-C4 region of SPIK is critical for this suppression. These studies suggest that over-expression of SPIK may prevent GzmA-mediated immune-killing, thereby establishing the tolerance of cancer cells to the bodys immune surveillance system. Suppression of over-expressed SPIK can restore the susceptibility of these cells to apoptotic death triggered by GzmA. This finding implies that it is possible to overcome tolerance of cancer cells to the bodys immune surveillance system and restore the GzmA-mediated immune-killing by suppressing the over-expression of SPIK.
Hypermethylation of the promoter of the tumor suppressor gene, adenomatous polyposis coli (APC), occurs in various malignancies, including hepatocellular carcinoma (HCC). However, reports on the specificity of the methylation of the APC gene for HCC have varied. To gain insight into how these variations occur, bisulfite PCR sequencing was performed to analyze the methylation status of both sense and antisense strands of the APC gene in samples of HCC tissue, matched adjacent non-HCC liver tissue, hepatitis, cirrhosis, and normal liver tissues. DNA derived from fetal liver and 12 nonhepatic normal tissue was also examined. These experiments revealed liver-specific, antisense strand-biased CpG methylation of the APC gene and suggested that, although methylation of the antisense strand of the APC gene exists in normal liver and other non-HCC disease liver tissue, methylation of the sense strand of the APC gene occurs predominantly in HCC. To determine the effect of the DNA strand on the specificity of the methylated APC gene as a biomarker for HCC detection, quantitative methylation-specific PCR assays for sense and antisense strand DNA were developed and performed on DNA isolated from HCC (n?=?58), matched adjacent non-HCC (n?=?58), cirrhosis (n?=?41), and hepatitis (n?=?39). Receiver operating characteristic curves were constructed. With the cutoff value set at the limit of detection, the specificity of sense and antisense strand methylation was 84% and 43%, respectively, and sensitivity was 67.2% and 72.4%, respectively. This result demonstrated that the identity of the methylated DNA strand impacted the specificity of APC for HCC detection. Interestingly, methylation of the sense strand of APC occurred in 40% of HCCs from patients with serum AFP levels less than 20 ng/mL, suggesting a potential role for APC as a biomarker to complement AFP in HCC screening.
Changes in glycosylation have long been associated with disease. While there are many methods to detect changes in glycosylation, plant derived lectins are often used to determine changes on specific proteins or molecules of interest. One change in glycosylation that has been observed by us and by others is a disease or antigen associated increase in fucosylation on N-linked glycans. To measure this change, the fucose binding Aleuria aurantia lectin (AAL) is often utilized in plate and solution based assays. AAL is a mushroom derived lectin that contains five fucose binding sites that preferentially bind fucose linked (?-1,3, ?-1,2, ?-,4, and ?-1,6) to N-acetyllactosamine related structures. Recently, several reports by us and by others have indicated that specific fucose linkages found on certain serum biomarker glycoproteins are more associated with disease than others. Taking a site-directed mutagenesis approach, we have created a set of recombinant AAL proteins that display altered binding affinities to different analytes containing various fucose linkages.
Hepatitis B e antigen (HBeAg) seroconversion is an important clinical and virological "landmark" during chronic hepatitis B virus (HBV) infection. Mutant viruses carrying the precore G1896A and/or the basal core promoter (BCP) A1762T/G1764A mutations are associated with HBeAg seroconversion. However, the exact role of these mutants in HBeAg seroconversion remains unclear, partly because the evolution of these mutant viruses before and after seroconversion has not been well studied.
The high levels of hepatitis B virus (HBV) surface antigen (HBsAg)-bearing subviral particles in the serum of chronically infected individuals play an important role in suppressing HBV-specific immune response and are only mildly affected by the current small molecule therapies. Thus, a therapy that specifically reduces HBsAg serum levels could be used in combination therapy with nucleos(t)ide drugs or permit therapeutic vaccination for the treatment of HBV infection. Herein, we report the design, synthesis, and evaluation of novel triazolo-pyrimidine inhibitors (1, 3, and 4) of HBsAg cellular secretion, with activity against drug-resistant HBV variants. Extensive SAR led to substantial improvements in the EC(50) of the parent compound, 5 (HBF-0259), with the best being 3c, with EC(50) = 1.4 ± 0.4 ?M, SI ? 36. The lead candidates, both 1a (PBHBV-001) and 3c (PBHBV-2-15), were well-tolerated in both normal and HBV-transgenic mice and exhibited acceptable pharmacokinetics and bioavailability in Sprague-Dawley rats.
Hepatitis B virus envelope glycoproteins Large (L), Middle (M) and Small (S) are targets of the host cellular immune system. The extent to which the host recognizes viral antigens presented by infected cells is believed to play a decisive role in determining if an infection will be resolved or become chronic. As with other antigens, HBV envelope polypeptides must be degraded, presumably by cellular proteasomes, to be presented by the MHC I pathway. We have used M as a model to study this process and determine how ER quality control monitors these foreign polymeric proteins and disposes of them through the ER-associated degradation (ERAD) pathway. Using both wild type and mutant HBV M protein, we found that unlike most ERAD substrates, which require ubiquitination for retrotranslocation and degradation, the HBV M protein, which only contains two lysine residues, can undergo rapid and complete, ubiquitin independent, proteasome dependent degradation. The utilization of this pathway had a functional consequence, since proteins degraded through it, were poorly presented via MHC I. To test the hypothesis that the level of ubiquitination, independent of protein degradation, controls the level of antigen presentation, we inserted two additional lysines into both the wild type and mutant M protein. Amazingly, while the addition of the lysine residues dramatically increased the level of ubiquitination, it did not alter the rate of degradation. However and remarkably, the increased ubiquitination was associated with a dramatic increase in the level of antigen presentation. In conclusion, using the HBV surface protein as a model, we have identified a novel ubiquitin independent degradation pathway and determined that this pathway can have implications for antigen presentation and potentially viral pathogenesis.
Hepatitis B virus (HBV) carrying the A1762T/G1764A double mutation in the basal core promoter (BCP) region is associated with HBe antigen seroconversion and increased risk of liver cirrhosis and hepatocellular carcinoma (HCC). Quantification of the mutant viruses may help in predicting the risk of HCC. However, the viral genome tends to have nucleotide polymorphism, which makes it difficult to design hybridization-based assays including real-time PCR. Ultrasensitive quantification of the mutant viruses at the early developmental stage is even more challenging, as the mutant is masked by excessive amounts of the wild-type (WT) viruses. In this study, we developed a selective inhibitory PCR (siPCR) using a locked nucleic acid-based PCR blocker to selectively inhibit the amplification of the WT viral DNA but not the mutant DNA. At the end of siPCR, the proportion of the mutant could be increased by about 10,000-fold, making the mutant more readily detectable by downstream applications such as real-time PCR and DNA sequencing. We also describe a primer-probe partial overlap approach which significantly simplified the melting curve patterns and minimized the influence of viral genome polymorphism on assay accuracy. Analysis of 62 patient samples showed a complete match of the melting curve patterns with the sequencing results. More than 97% of HBV BCP sequences in the GenBank database can be correctly identified by the melting curve analysis. The combination of siPCR and the SimpleProbe real-time PCR enabled mutant quantification in the presence of a 100,000-fold excess of the WT DNA.
Dengue virus infection causes diseases in people, ranging from the acute febrile illness dengue fever, to life-threatening dengue hemorrhagic fever/dengue shock syndrome. We previously reported that a host cellular ?-glucosidases I and II inhibitor, imino sugar CM-10-18, potently inhibited dengue virus replication in cultured cells, and significantly reduced viremia in dengue virus infected AG129 mice. In this report we show that CM-10-18 also significantly protects mice from death and/or disease progress in two mouse models of lethal dengue virus infection. Our results thus provide a strong support for the development of CM-10-18 or its derivatives as antiviral agents to treat servere dengue virus infections.
Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and the occurrence of HCC has more than doubled in the United States in the past decade. Early detection is considered key to reducing the mortality of HCC.
Golgi phosphoprotein 2 (GP73) is a type II Golgi protein, which was found on examination of the fucosylated proteome as a potential tumor marker for hepatocellular carcinoma (HCC). The serum levels of both total and fucosylated GP73 were increased in the sera of patients with HCC. Fucosylation is one of the most important oligosaccharide modifications involved in cancer and is catalyzed by ?1,6-fucosyltransferase (Fut8). In the present study, we investigated the effect of Fut8 overexpression on GP73 production in the human hepatoma cell line Hep3B. The Fut8 expression vector was transfected into Hep3B cells and the expression of GP73 was investigated by Western blotting and real-time PCR. Overexpression of Fut8 dramatically enhanced the expression of GP73 at the transcriptional level. Surprisingly, this effect was not dependent on cellular fucosylation. Overexpression of a mutant Fut8, which was unable to be localized to the Golgi, did not induce GP73 production, suggesting that the localization of Fut8 in the Golgi apparatus was important for the increase in GP73 expression. This is the first demonstration of GP73 regulation through overexpression of a glycosyltransferase, which may lead to Golgi stress.
Hepatocellular carcinoma (HCC) has a 5-year survival rate of <10% because it is difficult to diagnose early. Mutations in the TP53 gene are associated with approximately 50% of human cancers. A hotspot mutation, a G:C to T:A transversion at codon 249 (249T), may be a potential DNA marker for HCC screening because of its exclusive presence in HCC and its detection in the circulation of some patients with HCC. A locked nucleic acid clamp-mediated PCR assay, followed by melting curve analysis (using the SimpleProbe), was developed to detect the TP53 249T mutation. In this assay, the locked nucleic acid clamp suppressed 10(7) copies of wild-type templates and permitted detection of 249T-mutated template, with a sensitivity of 0.1% (1:1000) of the mutant/wild-type ratio, assessed by a reconstituted standard within 2 hours. With an amplicon size of 41 bp, it detects target DNA sequences in short fragmented DNA templates. The detected mutations were validated by DNA sequencing analysis. We then tested DNA isolated from urine samples of patients with HCC for p53 mutations and identified positive TP53 mutations in 9 of 17 samples. The possibility of using this novel TP53 249T assay to develop a urine or blood test for HCC screening is discussed.
Hepatitis B virus (HBV) precore G1896A mutation is associated with Hepatitis B e antigen (HBeAg) seroconversion. This mutation and the adjacent G1899A mutation also appear to associate with increased risk of hepatocellular carcinoma. Quantitative mutant dynamics may help determine the potential of these mutants as clinical biomarkers. However, a reliable method to quantify either mutant is not available, partly because the viral genome has polymorphisms in general and the precore mutations are complex.
?-Glucosidases I and II are endoplasmic reticulum-resident enzymes that are essential for N-linked glycan processing and subsequent proper folding of glycoproteins. In this report, we first demonstrate that downregulation of the expression of ?-glucosidase I, II, or both in Huh7.5 cells by small hairpin RNA technology inhibited the production of hepatitis C virus (HCV). In agreement with the essential role of ?-glucosidases in HCV envelope glycoprotein processing and folding, treatment of HCV-infected cells with a panel of imino sugar derivatives, which are competitive inhibitors of ?-glucosidases, did not affect intracellular HCV RNA replication and nonstructural protein expression but resulted in the inhibition of glycan processing and subsequent degradation of HCV E2 glycoprotein. As a consequence, HCV virion assembly and secretion were inhibited. In searching for imino sugars with better antiviral activity, we found that a novel imino sugar, PBDNJ0804, had a superior ability to inhibit HCV virion assembly and secretion. In summary, we demonstrated that glucosidases are important host factor-based antiviral targets for HCV infection. The low likelihood of drug-resistant virus emergence and potent antiviral efficacy of the novel glucosidase inhibitor hold promise for its development as a therapeutic agent for the treatment of chronic hepatitis C.
We screened ?2,200 compounds known to be safe in people for the ability to reduce the amount of virion-associated hepatitis B virus (HBV) DNA in the culture medium of producer cells. These efforts led to the discovery of an alkylated porphyrin, chlorophyllide, as the compound that achieved the greatest reduction in signal. Here we report that chlorophyllide directly and quantitatively disrupted HBV virions at micromolar concentrations, resulting in the loss of all detectable virion DNA, without detectably affecting cell viability or intracellular viral gene products. Chemophores of chlorophyllide were also tested. Chlorin e6, a metal-free chlorophyllide-like molecule, showed the strongest antiviral activity against HBV as well as profound antiviral effects on other enveloped viruses, such as hepatitis C virus (HCV), human immunodeficiency virus (HIV), dengue virus (DENV), Marburg virus (MARV), Tacaribe virus (TCRV), and Junin viruses (JUNV). Remarkably, chlorin e6 inactivated DENV at subnanomolar-level concentrations. However, the compound had no antiviral effect against encephalomyocarditis virus and adenovirus, suggesting that chlorin e6 may be less active or inactive against nonenveloped viruses. Although other porphyrin derivatives have been previously reported to possess antiviral activity, this is the first analysis of the biochemical impact of chlorophyllide and chlorin e6 against HBV and of the dramatic anti-infectivity impact upon DENV. The possible application of this family of compounds as antiviral agents, as microbicides and systemic virus neutralizing agents, is discussed.
Alpha interferon (IFN-?) is an approved medication for chronic hepatitis B. Gamma interferon (IFN-?) is a key mediator of host innate and adaptive antiviral immunity against hepatitis B virus (HBV) infection in vivo. In an effort to elucidate the antiviral mechanism of these cytokines, 37 IFN-stimulated genes (ISGs), which are highly inducible in hepatocytes, were tested for their ability to inhibit HBV replication upon overexpression in human hepatoma cells. One ISG candidate, indoleamine 2,3-dioxygenase (IDO), an IFN-?-induced enzyme catalyzing tryptophan degradation, efficiently reduced the level of intracellular HBV DNA without altering the steady-state level of viral RNA. Furthermore, expression of an enzymatically inactive IDO mutant did not inhibit HBV replication, and tryptophan supplementation in culture completely restored HBV replication in IDO-expressing cells, indicating that the antiviral effect elicited by IDO is mediated by tryptophan deprivation. Interestingly, IDO-mediated tryptophan deprivation preferentially inhibited viral protein translation and genome replication but did not significantly alter global cellular protein synthesis. Finally, tryptophan supplementation was able to completely restore HBV replication in IFN-?- but not IFN-?-treated cells, which strongly argues that IDO is the primary mediator of IFN-?-elicited antiviral response against HBV in human hepatocyte-derived cells.
Tetherin and IFITM3 are recently identified interferon-induced cellular proteins that restrict infections by retroviruses and filoviruses and of influenza virus and flaviviruses, respectively. In our efforts to further explore their antiviral activities against other viruses and determine their antiviral mechanisms, we found that the two antiviral proteins potently inhibit the infection of vesicular stomatitis virus (VSV), a prototype member of the Rhabdoviridae family. Taking advantage of this well-studied virus infection system, we show that although both tetherin and IFITM3 are plasma membrane proteins, tetherin inhibits virion particle release from infected cells, while IFITM3 disrupts an early event after endocytosis of virion particles but before primary transcription of incoming viral genomes. Furthermore, we demonstrate that both the N-terminal 21 amino acid residues and C-terminal transmembrane region of IFITM3 are required for its antiviral activity. Collectively, our work sheds light on the mechanisms by which tetherin and IFITM3 restrict infection with rhabdoviruses and possibly other pathogenic viruses.
Using polymerase chain reaction (PCR) and alkaline gel electrophoresis, the authors show that, compared with DNA derived from virions used to establish infection, herpes simplex virus DNA derived from quiescently infected rat pheochromocytoma (PC12) cells in culture accumulates alkaline-labile lesions. That is, compared with equivalent amounts of virion DNA, viral DNA from nerve growth factor-differentiated long-term infected cells in culture is consistently 3 to 10 times more refractory to amplification by PCR. Despite using equal mole amounts of DNA isolated from quiescently infected cells (determined by quantitative Southern blots), DNA from quiescently infected cells could not be detected by PCR under conditions in which the virion-derived DNA was easily detected. Refractoriness to PCR was confirmed by analysis with a ligation-mediated PCR technique. The refractoriness was not the result of genomic circularization. The refractoriness was, however, related to the time that the quiescently infected cells had been maintained in culture. The refractoriness to PCR was taken as an indication that the viral DNA was damaged. This hypothesis was confirmed by showing that viral DNA from quiescently infected PC12 cells accumulated alkaline-labile DNA lesions, as determined by alkaline gel electrophoresis. The phenomenon was not limited to tissue culture, because viral DNA derived from the ganglia of latently infected mice is also 3 to 10 times more refractory to amplification than are equivalent amounts of virion-derived genomes. Taken together, these results represent the first evidence that herpes simplex virus DNA is physically damaged as a function of long-term infection. Implications for viral reactivation and pathogenesis are discussed.
Cellular ?-glucosidases I and II are enzymes that sequentially trim the three terminal glucoses in the N-linked oligosaccharides of viral envelope glycoproteins. This process is essential for the proper folding of viral glycoproteins and subsequent assembly of many enveloped viruses, including dengue virus (DENV). Imino sugars are substrate mimics of ?-glucosidases I and II. In this report, we show that two oxygenated alkyl imino sugar derivatives, CM-9-78 and CM-10-18, are potent inhibitors of both ?-glucosidases I and II in vitro and in treated animals, and efficiently inhibit DENV infection of cultured human cells. Pharmacokinetic studies reveal that both compounds are well tolerated at doses up to 100mg/kg in rats and have favorable pharmacokinetic properties and bioavailability in mice. Moreover, we showed that oral administration of either CM-9-78 or CM-10-18 reduces the peak viremia of DENV in mice. Interestingly, while treatment of DENV infected mice with ribavirin alone did not reduce the viremia, combination therapy of ribavirin with sub-effective dose of CM-10-18 demonstrated a significantly enhanced antiviral activity, as indicated by a profound reduction of the viremia. Our findings thus suggest that combination therapy of two broad-spectrum antiviral agents may provide a practically useful approach for the treatment of DENV infection.
In this report, the possibility of pharmacologically altering the hepatitis B virus (HBV) epitopes presented by major histocompatibility complex class I on infected cells is demonstrated. The HBV middle envelope glycoprotein (MHBs) maturation appears to require calnexin-mediated folding. This interaction is dependent on glucosidases in the endoplasmic reticulum. Prevention of HBV envelope protein maturation in cultured cells through use of glucosidase inhibitors, such as 6-O-butanoyl castanospermine and N-nonyl deoxynorjirimycin, resulted in MHBs degradation by proteasomes. The de-N-glycosylation associated with polypeptide degradation was predicted to result in conversion of asparagine residues into aspartic acid residues. This prediction was confirmed by showing that peptides corresponding to the N-glycosylation sequons of MHBs, but with aspartic acid replacing asparagine, (1) can prime human cytotoxic T lymphocytes that recognize HBV-producing cells and (2) that the presentation of these envelope motifs by major histocompatibility complex class I is enhanced by incubation with glucosidase inhibitors. Moreover, although peripheral blood mononuclear cells isolated from woodchucks chronically infected with woodchuck hepatitis virus and vaccinated with woodchuck hepatitis virus surface antigen could be induced to recognize the natural MHBs asparagine-containing peptides, only cells isolated from animals treated with glucosidase inhibitor recognized the aspartic acid-containing peptides.
Alpha interferon (IFN-alpha) is an approved medication for chronic hepatitis B. Gamma interferon (IFN-gamma) is a key mediator of host antiviral immunity against hepatitis B virus (HBV) infection in vivo. However, the molecular mechanism by which these antiviral cytokines suppress HBV replication remains elusive. Using an immortalized murine hepatocyte (AML12)-derived cell line supporting tetracycline-inducible HBV replication, we show in this report that both IFN-alpha and IFN-gamma efficiently reduce the amount of intracellular HBV nucleocapsids. Furthermore, we provide evidence suggesting that the IFN-induced cellular antiviral response is able to distinguish and selectively accelerate the decay of HBV replication-competent nucleocapsids but not empty capsids in a proteasome-dependent manner. Our findings thus reveal a novel antiviral mechanism of IFNs and provide a basis for a better understanding of HBV pathobiology.
We previously reported increased levels of protein-linked fucosylation with the development of liver cancer and identified many of the proteins containing the altered glycan structures. One such protein is alpha-1-antitrypsin (A1AT). To advance these studies, we performed N-linked glycan analysis on the five major isoforms of A1AT and completed a comprehensive study of the glycosylation of A1AT found in healthy controls, patients with hepatitis C- (HCV) induced liver cirrhosis, and in patients infected with HCV with a diagnosis of hepatocellular carcinoma (HCC).
Interferons (IFNs) are key mediators of the host innate antiviral immune response. To identify IFN-stimulated genes (ISGs) that instigate an antiviral state against two medically important flaviviruses, West Nile virus (WNV) and dengue virus (DENV), we tested 36 ISGs that are commonly induced by IFN-alpha for antiviral activity against the two viruses. We discovered that five ISGs efficiently suppressed WNV and/or DENV infection when they were individually expressed in HEK293 cells. Mechanistic analyses revealed that two structurally related cell plasma membrane proteins, IFITM2 and IFITM3, disrupted early steps (entry and/or uncoating) of the viral infection. In contrast, three IFN-induced cellular enzymes, viperin, ISG20, and double-stranded-RNA-activated protein kinase, inhibited steps in viral proteins and/or RNA biosynthesis. Our results thus imply that the antiviral activity of IFN-alpha is collectively mediated by a panel of ISGs that disrupt multiple steps of the DENV and WNV life cycles.
Primary cancer of the liver, hepatocellular carcinoma (HCC), is an extremely deadly cancer, with very poor 5 year survivals, following diagnosis. The poor outcomes are believed to be due, in part, to the late times in which the cancers are usually first detected. Improved methods for early detection have thus become a top priority in the management of liver cancer. This Chapter reviews current methods of detection as well as leading new methods. Possible explanations as to why there are so many markers that are being discovered, but so few that make it to validation are discussed.
Hepatitis B and C viruses (HBV and HCV, respectively) are different and distinct viruses, but there are striking similarities in their disease potential. Infection by either virus can cause chronic hepatitis, liver cirrhosis, and ultimately, liver cancer, despite the fact that no pathogenetic mechanisms are known which are shared by the two viruses. Our recent studies have suggested that replication of either of these viruses upregulates a cellular protein called serine protease inhibitor Kazal (SPIK). Furthermore, the data have shown that cells containing HBV and HCV are more resistant to serine protease-dependent apoptotic death. Since our previous studies have shown that SPIK is an inhibitor of serine protease-dependent apoptosis, it is hypothesized that the upregulation of SPIK caused by HBV and HCV replication leads to cell resistance to apoptosis. The evasion of apoptotic death by infected cells results in persistent viral replication and constant liver inflammation, which leads to gradual accumulation of genetic changes and eventual development of cancer. These findings suggest a possibility by which HBV and HCV, two very different viruses, can share a common mechanism in provoking liver disease and cancer.
We hereby report two instances of dimorphic fungus cultivation in BacT/ALERT-based bacteriologic media, with the first such characterization of Blastomyces dermatitidis. From a patient with disseminated coccidioidomycosis, routine blood cultures incubated on the MB/BacT 3D Microbial Detection System generated a positive signal following 75 h of incubation. B. dermatitidis was isolated from a patient hospitalized with a four-week course of respiratory illness. Organism detection from respiratory specimens via the MB/BacT 3D Mycobacteria Detection System occurred 5 days sooner than the routine fungus culture. Etiologic agents of endemic mycoses may be isolated in bacteriologic media employed by continuous monitoring instrumentation.
Changes in glycosylation, most notably fucosylation, have been associated with the development of hepatocellular carcinoma (HCC). In this report, the levels of fucosylated kininogen (Fc-Kin) and fucosylated alpha-1-antitrypsin were analyzed individually and in combination with the currently used marker, alpha-fetoprotein, and a previously identified biomarker, Golgi protein 73 (GP73), for the ability to distinguish between a diagnosis of cirrhosis and HCC. This analysis was done on serum from 113 patients with cirrhosis and 164 serum samples from patients with cirrhosis plus HCC. The levels of Fc-Kin and fucosylated alpha-1-antitrypsin were significantly higher in patients with HCC compared with those with cirrhosis (P < 0.0001). Greatest performance was achieved through the combination of Fc-Kin, alpha-fetoprotein, and GP73, giving an optimal sensitivity of 95%, a specificity of 70%, and an area under the receiver operating characteristic of 0.94. In conclusion, the altered glycosylation of serum glycoproteins can act as potential biomarkers of primary HCC when used independently or in combination with other markers of HCC.
The expense inherent to molecular diagnostics may be an overriding concern for a variety of clinical laboratories in the development of PCR-based methicillin-resistant Staphylococcus aureus (MRSA) active surveillance programs. BD GeneOhm MRSA assay master mix was reconstituted, aliquoted into SmartCycler tubes in 25-microl volumes, and frozen at -70 degrees C. One hundred percent of archival nasal swab lysates yielded the expected PCR results when incubated in master mix frozen for 1, 2, 3, and 4 weeks. A 98.8% concordance of the final result was observed upon prospective PCR analysis of 320 clinical lysates utilizing freshly reconstituted master mix and 2-week-frozen master mix. Initial unresolved rates generated by frozen master mix and freshly reconstituted master mix differed by 1.6% (P = 0.16). Of 50 MRSA-positive lysates, the titers of 32 (64%) were determined to the same value upon initial tandem frozen master mix and freshly reconstituted master mix utilization; the titers of an additional 14 were determined to the same value upon repeat testing. Frozen master mix maintains potency for at least 4 weeks, facilitating detection of MRSA from nasal swab lysates, and may decrease the amount of unused reagent up to an average of 33%.
Changes in N-linked glycosylation are known to occur during the development of cancer. For example, we have previously reported changes in N-linked glycosylation that occur with the development of hepatocellular carcinoma (HCC) and, through the use of glycoproteomics, identified many of those proteins containing altered glycan structures. To advance these studies and further explore the glycoproteome, we performed N-linked glycan analysis from serum samples depleted of the major acute phase proteins, followed by targeted lectin extraction of those proteins containing changes in glycosylation. Using this method, changes in glycosylation, specifically increased amounts of core and outer arm fucosylation, were observed in the depleted samples. The identities of those proteins containing core and outer arm fucose were identified in the serum of patients with HCC. The usefulness of some of these proteins in the diagnosis of HCC was determined through the analysis of over 300 patient samples using a high-throughput plate based approach. Greatest performance was achieved with fucosylated hemopexin, which had an AUROC of 0.9515 with an optimal sensitivity of 92% and a specificity of 92%.
Type III interferons (IFN), IFN-lambda or IL-28/29, are new members of the IFN super-family. Except for using distinct receptors, type I and type III IFNs share the same major post receptor signaling components to activate the transcription of a similar set of IFN-stimulated genes (ISGs). To examine the antiviral effects of the new type IFNs against West Nile virus (WNV), we compared the antiviral effects of IFN-alpha and IFN-lambda on WNV virus-like particle (VLP) infection and replicon replication in Huh7.5 and Hela cells. The results revealed that (i) both types of IFNs could efficiently prevent the WNV infection, but IFN-alpha demonstrated a stronger antiviral efficacy; (ii) WNV genome replication in VLP-infected cells and replicon-containing cell lines could only be inhibited by IFN-alpha, but not IFN-lambda; (iii) in agreement with the observed antiviral effects, only IFN-lambda-induced activation of JAK-STAT signaling pathway and induction of ISG expression were completely inhibited in WNV replicon-containing cell lines, but IFN-alpha signal transduction was either unaffected or only partially inhibited in Huh7.5 or Hela cells by the virus. Hence, the differential inhibition of WNV on IFN-alpha and IFN-lambda signal transduction implies that the receptors of the two types of IFNs, but not the common post receptor signaling components, could be selectively targeted either directly by WNV nonstructural proteins or indirectly by the cellular responses induced by the virus infection to inhibit the signal transduction of the cytokines.
Inhibitors of alpha glucosidases prevent the trimming of oligosaccharides on certain nascent glycoproteins, including the hepatitis B virus MHBs envelope glycoprotein. MHBs proteins with untrimmed oligosaccharides do not interact with calnexin, increasing protein misfolding and subsequent degradation by proteasomes. As peptides loaded onto newly synthesized MHC class I complexes are predominantly derived from proteasomes, the possibility that glucosidase inhibition could increase presentation by MHC class I was determined. Using either a model epitope, or a natural MHBs epitope, it was demonstrated that glucosidase inhibitors enhanced presentation by MHC class I and promoted activation of antigen-specific CTLs, suggesting a pharmacologic approach to immune modulation.
The aminoglycoside, geneticin (G418), was recently shown to have antiviral activity against bovine viral diarrhea virus (BVDV). Since BVDV, dengue virus (DENV) and yellow fever virus (YFV) all belong to the Flaviviridae family, it seemed possible that a common step in their life cycle might be affected by this aminoglycoside. Here it is shown that geneticin prevented the cytopathic effect (CPE) resulting from DENV-2 infection of BHK cells, in a dose-dependent manner with an 50% effective concentration (EC(50)) value of 3+/-0.4microg/ml. Geneticin had no detectable effect on CPE caused by YFV in BHK cells. Geneticin also inhibited DENV-2 viral yield with an EC(50) value of 2+/-0.1microg/ml and an EC(90) value of 20+/-2microg/ml. With a CC(50) value of 165+/-5microg/ml, the selectivity index of anti-DENV activity of geneticin in BHK cells was established to be 66. Furthermore, 25microg/ml of geneticin nearly completely blocked plaque formation induced by DENV-2, but not YFV. In addition, geneticin, inhibited DENV-2 viral RNA replication and viral translation. Gentamicin, kanamycin, and the guanidinylated geneticin showed no anti-DENV activity. Neomycin and paromomycin demonstrated weak antiviral activity at high concentrations. Finally, aminoglycoside-3-phosphotransferase activity of neomycin-resistant gene abolished antiviral activity of geneticin.
Imino sugars, such as N-butyl-deoxynojirimycin and N-nonyl-deoxynojirimycin (NNDNJ), are glucose analogues that selectively inhibit cellular alpha-glucosidase I and II in the endoplasmic reticulum and exhibit antiviral activities against many types of enveloped viruses. Although these molecules have broad-spectrum antiviral activity, their development has been limited by a lack of efficacy and/or selectivity. We have previously reported that a DNJ derivative with a hydroxylated cyclohexyl side chain, called OSL-95II, has an antiviral efficacy similar to that of NNDNJ but significantly less toxicity. Building upon this observation, a family of imino sugar derivatives containing an oxygenated side chain and terminally restricted ring structures were synthesized and shown to have low cytotoxicity and superior antiviral activity against members of the Flaviviridae family, including bovine viral diarrhea virus, dengue virus (DENV), and West Nile virus. Of particular interest is that several of these novel imino sugar derivatives, such as PBDNJ0801, PBDNJ0803, and PBDNJ0804, potently inhibit DENV infection in vitro, with 90% effective concentration values at submicromolar concentrations and selectivity indices greater than 800. Therefore, these compounds represent the best in their class and may offer realistic candidates for the development of antiviral therapeutics against human DENV infections.
Recognition of virus infections by pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), retinoic acid-inducible gene I (RIG-I), and melanoma differentiation associated gene 5 (MDA5), activates signaling pathways, leading to the induction of inflammatory cytokines that limit viral replication. To determine the effects of PRR-mediated innate immune response on hepatitis B virus (HBV) replication, a 1.3mer HBV genome was cotransfected into HepG2 or Huh7 cells with plasmid expressing TLR adaptors, myeloid differentiation primary response gene 88 (MyD88), and TIR-domain-containing adaptor-inducing beta interferon (TRIF), or RIG-I/MDA5 adaptor, interferon promoter stimulator 1 (IPS-1). The results showed that expressing each of the three adaptors dramatically reduced the levels of HBV mRNA and DNA in both HepG2 and Huh7 cells. However, HBV replication was not significantly affected by treatment of HBV genome-transfected cells with culture media harvested from cells transfected with each of the three adaptors, indicating that the adaptor-induced antiviral response was predominantly mediated by intracellular factors rather than by secreted cytokines. Analyses of involved signaling pathways revealed that activation of NF-kappaB is required for all three adaptors to elicit antiviral response in both HepG2 and Huh7 cells. However, activation of interferon regulatory factor 3 is only essential for induction of antiviral response by IPS-1 in Huh7 cells, but not in HepG2 cells. Furthermore, our results suggest that besides NF-kappaB, additional signaling pathway(s) are required for TRIF to induce a maximum antiviral response against HBV. Knowing the molecular mechanisms by which PRR-mediated innate defense responses control HBV infections could potentially lead to the development of novel therapeutics that evoke the host cellular innate antiviral response to control HBV infections.
The 1762T/1764A double mutation of the hepatitis B virus (HBV) basal core promoter has been suggested to be a potential biomarker for hepatocellular carcinoma (HCC) among individuals with chronic HBV infection. In this study, a real-time PCR assay is established using the hybridization probes and an oligonucleotide clamp containing locked nucleic acids (LNAs). The LNA-containing oligonucleotide clamp specific for the wild type HBV is able to suppress the amplification of the wild type HBV templates. In addition, the clamp can inhibit the binding of the WT templates to the fluorescence probes thereby suppress the wild type HBV signals during the melting curve analyses. These effects facilitated the detection of HBV double mutation in the presence of 3000-fold excess of the wild type genome. Thus PCR amplification coupled with the melting curve analyses provides a quick, simple, and highly sensitive tool for the detection of this HBV double mutation.
We have previously identified several biomarkers of hepatocellular carcinoma (HCC). The levels of three of these biomarkers were analyzed individually and in combination with the currently used marker, alpha fetoprotein (AFP), for the ability to distinguish between a diagnosis of cirrhosis (n=113) and HCC (n=164). We have utilized several novel biostatistical tools, along with the inclusion of clinical factors such as age and gender, to determine if improved algorithms could be used to increase the probability of cancer detection. Using several of these methods, we are able to detect HCC in the background of cirrhosis with an AUC of at least 0.95. The use of clinical factors in combination with biomarker values to detect HCC is discussed.
The Golgi phosphoprotein GP73 is elevated in the circulation of individuals with a diagnosis of hepatocellular carcinoma. Its usefulness as a biomarker of HCC is questioned, since it has also been reported to be elevated in the circulation of people with liver cirrhosis. Regulation of GP73 by inflammatory cytokines is therefore of interest. The interleukin-6 (IL-6) family cytokines were tested for effects on GP73 mRNA and/or protein levels in human hepatoblastoma HepG2 cells. Levels of GP73 mRNA and protein were up-regulated in HepG2 cells following treatment with either proinflammatory cytokine IL-6 or the related cytokine oncostatin M (OSM). Induction required the shared receptor subunit gp130, and correlated with increased tyrosine phosphorylation of STAT3. Maximal cytokine-mediated induction was not observed in the presence of protein synthesis inhibitor cycloheximide, suggesting additional regulatory factors play an important role. ELISA measurement of GP73 and IL-6 levels in the sera of patients with pre-malignant liver disease revealed a significant correlation between circulating levels of the two proteins. Similarly, a sensitive ELISA assay was developed to measure circulating OSM. OSM levels were elevated 6-7 fold in sera from patients with either cirrhosis or HCC relative to controls without liver disease. Although there was an association between levels of GP73 and OSM in serum from people with liver cirrhosis, there was not a statistically significant correlation in HCC, suggesting that the role of the cytokines in determining circulating levels may be complex. To our knowledge, this is the first report of OSM elevation being associated with liver disease.
Pattern recognition receptor (PRR)-mediated innate immune responses play an essential role in defending the host from viral infections. Intriguingly, hepatitis B virus (HBV) has been shown to induce negligible innate immune responses during the early phase of infection. Whether this is due to the failure of the virus to activate PRRs or suppression of PRR signaling pathways by the virus remains controversial. However, a plethora of evidence suggests that HBV is sensitive to PRR ligand-induced antiviral responses. This review summarizes current understanding of the interaction between HBV and PRR-mediated host innate immunity, antiviral mechanisms of PRR responses against HBV and strategies to combat chronic HBV infection via induction of host innate antiviral responses.
Recognition of virus infection by innate pattern recognition receptors (PRRs), including membrane-associated toll-like receptors (TLR) and cytoplasmic RIG-I-like receptors (RLR), activates cascades of signal transduction pathways leading to production of type I interferons (IFN) and proinflammatory cytokines that orchestrate the elimination of the viruses. Although it has been demonstrated that PRR-mediated innate immunity plays an essential role in defending virus from infection, it also occasionally results in overwhelming production of proinflammatory cytokines that cause severe inflammation, blood vessel leakage and tissue damage. In our efforts to identify small molecules that selectively enhance PRR-mediated antiviral, but not the detrimental inflammatory response, we discovered a compound, RO 90-7501 (2-(4-Aminophenyl)-[2,5-bi-1H-benzimidazol]-5-amine), that significantly promoted both TLR3 and RLR ligand-induced IFN-? gene expression and antiviral response, most likely via selective activation of p38 mitogen-activated protein kinase (MAPK) pathway. Our results thus imply that pharmacological modulation of PRR signal transduction pathways in favor of the induction of a beneficial antiviral response can be a novel therapeutic strategy.
We have discovered an Aleuria Aurantia Lectin (AAL)-reactive immunoglobulin G (IgG) that naturally occurs in the circulation of rabbits and mice, following immune responses induced by various foreign antigens. AAL can specifically bind to fucose moieties on glycoproteins. However, most serum IgGs are poorly bound by AAL unless they are denatured or treated with glycosidase. In this study, using an immunogen-independent AAL-antibody microarray assay that we developed, we detected AAL-reactive IgG in the sera of all animals that had been immunized 1-2 weeks previously with various immunogens with and without adjuvants and developed immunogen-specific responses. All of these animals subsequently developed immunogen-specific immune responses. The kinetics of the production of AAL-reactive IgG in mice and rabbits were distinct from those of the immunogen-specific IgGs elicited in the same animals: they rose and fell within one to two weeks, and peaked between four to seven days after exposure, while immunogen-specific IgGs continued to rise during the same period. Mass spectrometric profiling of the Fc glycoforms of purified AAL-reactive IgGs indicates that these are mainly comprised of IgGs with core-fucosylated and either mono-or non-galactosylated Fc N-glycan structures. Our results suggest that AAL-reactive IgG could be a previously unrecognized IgG subset that is selectively produced at the onset of a humoral response.
During the course of human immunodeficiency virus type 1 (HIV-1) disease, the virus has been shown to effectively escape the immune response with the subsequent establishment of latent viral reservoirs in specific cell populations within the peripheral blood (PB) and associated lymphoid tissues, bone marrow (BM), brain, and potentially other end organs. HIV-1, along with hepatitis B and C viruses (HBV and HCV), are known to share similar routes of transmission, including intravenous drug use, blood transfusions, sexual intercourse, and perinatal exposure. Substance abuse, including the use of opioids and cocaine, is a significant risk factor for exposure to HIV-1 and the development of acquired immune deficiency syndrome, as well as HBV and HCV exposure, infection, and disease. Thus, coinfection with HIV-1 and HBV or HCV is common and may be impacted by chronic substance abuse during the course of disease. HIV- 1 impacts the natural course of HBV and HCV infection by accelerating the progression of HBV/HCV-associated liver disease toward end-stage cirrhosis and quantitative depletion of the CD4+ T-cell compartment. HBV or HCV coinfection with HIV-1 is also associated with increased mortality when compared to either infection alone. This review focuses on the impact of substance abuse and coinfection with HBV and HCV in the PB, BM, and brain on the HIV-1 pathogenic process as it relates to viral pathogenesis, disease progression, and the associated immune response during the course of this complex interplay. The impact of HIV-1 and substance abuse on hepatitis virus-induced disease is also a focal point.
Synthesis of the covalently closed circular (ccc) DNA is a critical, but not well-understood step in the life cycle of hepadnaviruses. Our previous studies favor a model that removal of genome-linked viral DNA polymerase occurs in the cytoplasm and the resulting deproteinized relaxed circular DNA (DP-rcDNA) is subsequently transported into the nucleus and converted into cccDNA. In support of this model, our current study showed that deproteinization of viral double-stranded linear (dsl) DNA also took place in the cytoplasm. Furthermore, we demonstrated that Ku80, a component of non-homologous end joining DNA repair pathway, was essential for synthesis of cccDNA from dslDNA, but not rcDNA. In an attempt to identify additional host factors regulating cccDNA biosynthesis, we found that the DP-rcDNA was produced in all tested cell lines that supported DHBV DNA replication, but cccDNA was only synthesized in the cell lines that accumulated high levels of DP-rcDNA, except for NCI-H322M and MDBK cells, which failed to synthesize cccDNA despite of the existence of nuclear DP-rcDNA. The results thus imply that while removal of the genome-linked viral DNA polymerase is most likely catalyzed by viral or ubiquitous host function(s), nuclear factors required for the conversion of DP-rcDNA into cccDNA and/or its maintenance are deficient in the above two cell lines, which could be useful tools for identification of the elusive host factors essential for cccDNA biosynthesis or maintenance.
We recently described the discovery of oxygenated N-alkyl deoxynojirimycin (DNJ) derivative 7 (CM-10-18) with antiviral activity against dengue virus (DENV) infection both in vitro and in vivo. This imino sugar was promising but had an EC(50) against DENV in BHK cells of 6.5 ?M, which limited its use in in vivo. Compound 7 presented structural opportunities for activity relationship analysis, which we exploited and report here. These structure-activity relationship studies led to analogues 2h, 2l, 3j, 3l, 3v, and 4b-4c with nanomolar antiviral activity (EC(50) = 0.3-0.5 ?M) against DENV infection, while maintaining low cytotoxicity (CC(50) > 500 ?M, SI > 1000). In male Sprague-Dawley rats, compound 3l was well tolerated at a dose up to 200 mg/kg and displayed desirable PK profiles, with significantly improved bioavailability (F = 92 ± 4%).
Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) plays a central role in viral infection and persistence and is the basis for viral rebound after the cessation of therapy, as well as the elusiveness of a cure even after extended treatment. Therefore, there is an urgent need for the development of novel therapeutic agents that directly target cccDNA formation and maintenance. By employing an innovative cell-based cccDNA assay in which secreted HBV e antigen is a cccDNA-dependent surrogate, we screened an in-house small-molecule library consisting of 85,000 drug-like compounds. Two structurally related disubstituted sulfonamides (DSS), termed CCC-0975 and CCC-0346, emerged and were confirmed as inhibitors of cccDNA production, with low micromolar 50% effective concentrations (EC(50)s) in cell culture. Further mechanistic studies demonstrated that DSS compound treatment neither directly inhibited HBV DNA replication in cell culture nor reduced viral polymerase activity in the in vitro endogenous polymerase assay but synchronously reduced the levels of HBV cccDNA and its putative precursor, deproteinized relaxed circular DNA (DP-rcDNA). However, DSS compounds did not promote the intracellular decay of HBV DP-rcDNA and cccDNA, suggesting that the compounds interfere primarily with rcDNA conversion into cccDNA. In addition, we demonstrated that CCC-0975 was able to reduce cccDNA biosynthesis in duck HBV-infected primary duck hepatocytes. This is the first attempt, to our knowledge, to identify small molecules that target cccDNA formation, and DSS compounds thus potentially serve as proof-of-concept drug candidates for development into therapeutics to eliminate cccDNA from chronic HBV infection.
In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that allows for the glycosylation profiling of specific proteins. Glycosylation of proteins is the most prevalent post-translational modification found on proteins, and leads diversified modifications of the physical, chemical, and biological properties of proteins. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases. However, current methods to study protein glycosylation typically are too complicated or expensive for use in most normal laboratory or clinical settings and a more practical method to study protein glycosylation is needed. The new protocol described in this study makes use of a chemically blocked antibody microarray with glycan-binding protein (GBP) detection and significantly reduces the time, cost, and lab equipment requirements needed to study protein glycosylation. In this method, multiple immobilized glycoprotein-specific antibodies are printed directly onto the microarray slides and the N-glycans on the antibodies are blocked. The blocked, immobilized glycoprotein-specific antibodies are able to capture and isolate glycoproteins from a complex sample that is applied directly onto the microarray slides. Glycan detection then can be performed by the application of biotinylated lectins and other GBPs to the microarray slide, while binding levels can be determined using Dylight 549-Streptavidin. Through the use of an antibody panel and probing with multiple biotinylated lectins, this method allows for an effective glycosylation profile of the different proteins found in a given human or animal sample to be developed.
Infection of permissive cells, in tissue culture, with herpes simplex virus (HSV) has been reported to induce host DNA damage repair responses that are necessary for efficient viral replication. However, direct repair of the damaged viral DNA has not, to our knowledge, been shown. In this report, we detect and determine the amount of damaged HSV-1 DNA, following introduction of experimentally damaged HSV genomes into tissue cultures of permissive Vero, NGF differentiated PC12 cells and primary rat neurons, using a method of detection introduced here. The results show that HSV-1 strain 17 DNA containing UV-induced DNA damage is efficiently repaired, in Vero, but not NGF differentiated PC12 cells. The primary rat neuronal cultures were capable of repairing the damaged viral DNA, but with much less efficiency than did the permissive Vero cells. Moreover, by conducting the experiments with either an inhibitor of the HSV polymerase (phosphonoacetic acid [PAA]) or with a replication defective DNA polymerase mutant virus, HP66, the results suggest that repair can occur in the absence of a functional viral polymerase, although polymerase function seems to enhance the efficiency of the repair, in a replication independent manner. The possible significance of varying cell type mediated repair of viral DNA to viral pathogenesis is discussed.
Hypermethylation of the glutathione S-transferase ? 1 (GSTP1) gene promoter region has been reported to be a potential biomarker to distinguish hepatocellular carcinoma (HCC) from other liver diseases. However, reports regarding how specific a marker it is have ranged from 100% to 0%. We hypothesized that, to a large extent, the variation of specificity depends on the location of the CpG sites analyzed. To test this hypothesis, we compared the methylation status of the GSTP1 promoter region of the DNA isolated from HCC, cirrhosis, hepatitis, and normal liver tissues by bisulfite-PCR sequencing. We found that the 5 region of the position -48 nt from the transcription start site of the GSTP1 gene is selectively methylated in HCC, whereas the 3 region is methylated in all liver tissues examined, including normal liver and the HCC tissue. Interestingly, when DNA derived from fetal liver and 11 nonhepatic normal tissue was also examined by bisulfite-PCR sequencing, we found that methylation of the 3 region of the promoter appeared to be liver-specific. A methylation-specific PCR assay targeting the 5 region of the promoter was developed and used to quantify the methylated GSTP1 gene in various diseased liver tissues including HCC. When we used an assay targeting the 3 region, we found that the methylation of the 5-end of the GSTP1 promoter was significantly more specific than that of the 3-end (97.1% vs. 60%, p<0.0001 by Fishers exact test) for distinguishing HCC (n?=?120) from hepatitis (n?=?35) and cirrhosis (n?=?35). Encouragingly, 33.8% of the AFP-negative HCC contained the methylated GSTP1 gene. This study clearly demonstrates the importance of the location of CpG site methylation for HCC specificity and how liver-specific DNA methylation should be considered when an epigenetic DNA marker is studied for detection of HCC.
Alterations in glycosylation have long been associated with the development of cancer. In the case of primary hepatocellular carcinoma (HCC), one alteration that has often been associated is increased amounts of fucose attached to the N-glycans of serum proteins secreted by the liver.
We demonstrated previously that urine contains low-molecular-weight (LMW) (<300 bp), circulation-derived DNA that can be used to detect cancer-specific mutations if a tumor is present. The goal of this study was to develop an assay to detect the colorectal cancer (CRC)-associated, circulation-derived, epigenetic DNA marker hypermethylated vimentin gene (mVIM) in the urine of patients with CRC. An artificial 18-nucleotide DNA sequence was tagged at the 5 end of the primers of the first PCR cycle to increase the amplicon size, which was then integrated into the primers of the second PCR cycle. A quantitative MethyLight PCR-based assay targeting a 39-nucleotide template was developed and used to quantify mVIM in CRC tissues and matched urine samples. mVIM was detected in 75% of LMW urine DNA samples from patients with CRC (n = 20) and in 10% of urine samples of control subjects with no known neoplasia (n = 20); 12 of 17 LMW urine DNA samples (71%) but only 2 of 17 high-molecular-weight urine DNA samples (12%) from patients with mVIM-positive tissues contained detectable mVIM, suggesting that the mVIM detected in LMW urine DNA is derived from the circulation. The detection of mVIM in urine was significantly associated with CRC compared with controls (P < 0.0001, by Fishers exact test). A potential urine test for CRC screening using epigenetic markers is discussed.
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