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The high prevalence of the disease caused by hepatitis C virus (HCV) and the limited efficacy of interferon-based therapies have stimulated the search for safer and more effective drugs. The development of inhibitors of the HCV NS5B RNA polymerase represents a promising strategy for identifying novel anti-HCV therapeutics. However, the high genetic...
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Context 1
... major advance in the understanding of the NS5B polymerase was provided by the resolution of the three- dimensional structures of several truncated forms of the apoenzyme and of complexes with nucleotides or RNA templates (Adachi et al., 2002;Ago et al., 1999;Bressanelli et al., 2002;Bressanelli et al., 1999;Lesburg et al., 1999;O'Farrell et al., 2003). The NS5B has the canonical 'right hand' shape, with the characteristic fingers, palm and thumb sub-domains ( Figure 2). Similarly to other RdRps, the HCV polymerase has a compact shape due to the pres- ence of two extended loops -the fingertips -that connect the fingers and thumb domains and completely encircle the active site cavity, to which the RNA template and the nucleoside triphosphate (NTP) substrates have access through two positively charged tunnels (Bressanelli et al., 2002). ...
Context 2
... substitution of Pro156 with either Ser or Leu, or substitution of Gly152 with Glu were found to selectively confer resistance to [8] (Table 1). Pro156 and Gly152 are located in the Λ2 fingertips loop, within the NS5B RdRp active site channel, in line with the notion that dihydroxypyrimidine carboxylates directly target the enzyme active site (Figure 2). Molecular modelling data suggest that the Λ2 loop is in close contact with the speci- ficity portion of [8] but not with its metal chelating portion, thus explaining how mutations in this region may confer resistance without affecting the enzyme catalytic center. ...
Context 3
... B C replication defect imposed by Pro495 substitutions. Pro495 is located in the thumb domain of NS5B ( Figure 2) and is conserved across natural HCV strains, suggesting a func- tional role for this residue. X-ray crystallographic data indi- cated that Pro495 is a key residue involved in the interaction with a non-catalytic GTP molecule on NS5B (Bressanelli et al., 2002). ...
Context 4
... biochemical assays, only the M414T mutant enzyme demonstrated clear resistance to inhibition, while the enzymes containing the H95R, C451R and G558R mutations had no or marginal changes in their sensitivity to inhibition. This discrepancy, together with the observation that the mutated amino acids lie in different regions of the polymerase (Figure 2), suggested the exis- tence of multiple mechanisms of resistance and provided a first indirect clue towards identification of the benzothiadi- azines binding site on the enzyme. Indeed, only the mutant M414T enzyme lost the ability to interact with benzothia- diazines in a direct binding assay, indicating that only for this mutant was resistance due to reduced affinity for the inhibitor and suggesting that Met414 might be part of the inhibitor binding site. ...
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Citations
... Viral infections are a huge burden to humans, animals and plants. A good number of human diseases do not respond effectively to current antiviral agents and some lack effective therapeutics (Tomei et al., 2005). In addition, other factors include antiviral resistance (Hulgan and Haas, 2006), drug intolerability or inability of patients to procure available antiviral agents due to their exorbitant prices (Lemoine et al., 2013). ...
Major pandemics and seasonal epidemics that have ravaged the world in the past and even at present, are mostly caused by RNA viruses. This has necessitated the need for continuous research to identify important natural products, with antiviral potentials, which can be harnessed for use in the prevention and treatment of viral infections. This study therefore, evaluated the antiviral property of Curcuma longa on two important RNA viruses of public health importance, namely polio and measles viruses. Extraction of active ingredients from turmeric rhizomes was done with the use of Analar grade methanol and concentrated using rotary evaporator. Polio and measles viruses were isolated from their respective vaccines using Reed-Muench method. Infective doses of the viruses and toxicity profile of extract were determined. Confluent Vero cells were inoculated with the viruses at different dilutions of the extract, incubated and observed for 7 days. Methanol extract of Curcuma longa inhibited polio virus at the maximum non-toxic concentration (MNTC) of 0.031μg μL-1 and inhibitory concentration (IC50) of 0.067 μg μL-1 with selectivity index of 2.16. Inhibition by the extract was observed prior to infection with the viruses. Phytochemical analysis of the extract showed presence of terpenes, saponins, alkaloids, flavonoids, tannins, cardiac glycosides and phenol as the bioactive phytochemicals. This study has shown that curcuma longa has potent inhibitory activity, hence can be harnessed in the development of an effective antiviral agent against polio and measles viruses.
... These inhibitors accomplish their NS5B inhibition through different molecular mechanisms [11]. NIs can competitively bind to the natural nucleoside triphosphate substrates in the NS5B active site and exert an inhibitory effect on HCV polymerase through the obligate or non-obligate chain termination [12]. However, one general worry is that the NIs can be antagonistic when used together with Ribavirin [13], making them less viable candidates for such a combination therapy [14,15]. ...
... It gives good results with genotype 1 patients who did not respond to the dual drug therapy [9,21]. IDX-184 is another 2' modified nucleotide (Methylated at 2' position of the ribose of guanosine nucleotide) that was under clinical trials (phase IIb) but was halted in 2012 due to cardiac side effects reported for a related regimen [9,16,[23][24]. ...
Background:
IDX-184 is a guanosine derivative having a potent inhibitory performance against HCV NS5b polymerase.
Objective:
to test three different groups of 2'C - modified analogues of guanosine nucleotide against HCV polymerase.
Method:
Using combined Quantitative Structure-Activity Relationships (QSAR) and molecular docking, the suggested compounds are studied.
Results:
Examining the docked structures of the compounds with experimentally solved NS5b structure (PDB ID: 2XI3) revealed that most of the compounds have the same mode of interaction as that of guanosine nucleotide and hence, NS5b inhibition is possible.
Conclusion:
It is revealed that sixteen modifications have a better binding affinity to NS5b compared to guanosine. In addition, seven more compounds are better in NS5b binding compared to the approved drug, sofosbuvir, and the compound under clinical trials, IDX-184. Hence, these compounds could be a potent HCV NS5b inhibitors.
... First third of the polyprotein encode the viral structural proteins and contain interior or capsid protein (C) and the cover glycoprotein's p7, E1 and E2. and nonstructural proteins, programmed via the C-terminal two-thirds of the polyprotein, take part in diverse function in virus gathering and replication of RNA [29]. The major function of C protein is supposed to exist the creation of viral capsid, although the appearance of this protein have been account to contain pleiotropic special effects in mammalian cells, with transcriptional tone, modification of the lipid metabolism and sound effects on apoptosis [30]. E1 and E2 are chief viral glycoprotein's, out as of the viral polyprotein by the stroke of host-cell indication peptidases. ...
... NS4B is a fundamental covering protein hold a nucleotide obligatory sphere inside its cytosolic area. NS4B appearance within cells of mammalian bring distinguishing membranous vesicles -the covering web -which are supposed to subsist the place of duplication of virus [30]. ...
t is estimated that around more than 2% of the population of world is suffering with hepatitis C virus and death cases because of cirrhosis and liver cancer is more than 350000. The load and epidemiology of HCV infection is different in the different parts of the world. It vary with country particular prevalence range from <1% - >10%. In comparison with USA and other urbanized countries the spread of infection in poor countries commonly outcome of contact to infected blood in society settings and healthcare centers.HCV management programs must be country specific which may be different by background and rank of economic progress. Worldwide HCV is a main cause of liver disease and in future it would be a major cause of morbidity and mortality. The
complication related to the geographic allocation of HCV infection and its linked risk factor increases its progression. No vaccine is available for HCV and no later than
exposure for HCV prophylaxis, so the focal point of most important escaping work must
be secure supply of blood, protected management care and people who use drug decrease the number of those people in developing countries.
Key words: Hepatitis, Genome, Treatment, Epidemiology.
... Finding the new and effective antiviral compound is required because of lack of effective therapeutics for most of viral diseases, rise of antiviral drug resistance, and expensive antiviral therapies (Lemoine et al., 2013;Tomei et al., 2005). Plants are of particular interest to scientists as they are a rich source of phytochemicals with different biological activities, including antiviral activities (Jassim and Naji, 2003). ...
Curcumin, also known as Indian solid gold, is an age-old antimicrobial drug used in day-to-day activities by people of South-East Asian countries. It is very unfortunate that curcumin, which was used as general antiseptic and specialized treatments against common infections, is not widely available in the pharmaceutical stores. The principal reason behind this misery is the poor bioavailability of curcumin. In this chapter, we review the potential antimicrobial activity of curcumin, its oral bioavailability challenges and the efforts undertaken by researchers so far to overcome this problem. Finally, we would like to bring it to general consideration, strategies required in the future to make curcumin a marketable drug using advancements in nanotechnology.
... HCV NS5b is an interesting target for antiviral therapy with limited side effects. It was the subject of extensive trails to design both nucleoside and non-nucleoside inhibitors [15,16]. Different studies discussed various potential sites of HCV NS5b: Thumb pocket-I (Pro495, Pro496, Val499), Thumb pocket-II (Leu419, Met423), Palm pocket-I (Asn411, Met414, Tyr448) and the active site (Ser282) [17][18][19][20][21][22][23][24]. ...
A theoretical study has been carried out to interpret and support experimental findings regarding inhibition mechanism of HCV NS5b. Twenty-five HCV NS5b inhibitors were docked by QM-Polarized Ligand Docking (QPLD) technique. The comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods were used to derive 3D-QSAR models for the selected inhibitors. The CoMFA and CoMSIA models show good cross-validated (Q2) and non-cross-validated (R2) coefficients for the suggested inhibitors of 0.43, 0.98 and 0.65, 0.99, respectively. The inhibition mechanism was explored and validated. Details of the interactions between the inhibitors and HCV NS5b are given in terms of steric, electrostatic, hydrophobic, hydrogen bonding fields. Enhancing potency via substitutions at positions, which were explored based on these parameters. A good correlation was found between 3D-QSAR and docking results.
... Substitutions at proline 495 are signature drug resistance mutations for the thumb 1 NS5B inhibitors (17,(19)(20)(21) and have been previously observed under BMS-791325 selection both in vitro in replicon cultures (15,16) and in vivo in virologic rebound samples from patients receiving BMS-791325 in combination with IFN-␣/ RBV (22). Additional substitutions in NS5B, such as A421V and L392I, have been identified under sustained clinical or in vitro selective pressure of BMS-791325 (15,16,22), but the significance of the transient V494A variant observed here in a single patient under single-dose selection is difficult to assess. ...
BMS-791325 is a non-nucleoside inhibitor of hepatitis C virus (HCV) NS5B polymerase with low nanomolar potency against genotypes 1a (EC50 3 nM) and 1b (EC50 7 nM) in vitro. BMS-791325 safety, pharmacokinetics, and antiviral activity were evaluated in a double-blind, placebo-controlled single ascending dose study (clinicaltrials.gov ID: NCT00664625) in 24 patients (interferon-naïve and -experienced) with chronic HCV genotype 1 infection, randomized (5:1) to receive a single dose of BMS-791325 (100, 300, 600, 900 mg) or placebo. The prevalence and phenotype of HCV variants at baseline and specific post-treatment time points were assessed. Antiviral activity was observed in all cohorts, with a mean HCV RNA decline ≈2.5 log10 copies/mL observed 24 hours after a single 300-mg dose. Mean plasma half-life among cohorts was 7-9 hours; individual 24-hour levels exceeded the protein-adjusted EC90 for genotype 1 at all doses. BMS-791325 was generally well tolerated, with no serious adverse events or discontinuations. Enrichment for resistance variants was not observed at 100-600 mg. At 900 mg, variants (P495L/S) associated with BMS-791325 resistance in vitro were transiently observed in one patient, concurrent with an observed HCV RNA decline of 3.4 log10 IU/mL, but were replaced with wild type by 48 hours. Single doses of BMS-791325 were well tolerated; demonstrated rapid, substantial, and exposure-related antiviral activity; displayed dose-related increases in exposure; and showed viral kinetic and pharmacokinetic profiles supportive of once- or twice-daily dosing. These results support its further development in combination with other direct-acting antivirals for HCV genotype 1 infection.
... In vitro selection of BMS-791325 resistance variants at NS5B amino acid 495 (proline) is also typical of thumb site 1 inhibitors (27,48,(54)(55)(56). The substitutions observed (P495A/S/L/T) con-ferred variable levels of resistance in GT 1a and 1b replicons, with the lowest (12-and 14-fold, respectively) observed for P495A and the highest (67-and 44-fold, respectively) observed for P495S. ...
BMS-791325 is an allosteric inhibitor that binds to thumb site 1 of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase.
BMS-791325 inhibits recombinant NS5B proteins from HCV genotypes 1, 3, 4, and 5 at 50% inhibitory concentrations (IC50) below 28 nM. In cell culture, BMS-791325 inhibited replication of HCV subgenomic replicons representing genotypes 1a and
1b at 50% effective concentrations (EC50s) of 3 nM and 6 nM, respectively, with similar (3 to 18 nM) values for genotypes 3a, 4a, and 5a. Potency against genotype
6a showed more variability (9 to 125 nM), and activity was weaker against genotype 2 (EC50, 87 to 925 nM). Specificity was demonstrated by the absence of activity (EC50s of >4 μM) against a panel of mammalian viruses, and cytotoxic concentrations (50%) were >3,000-fold above the HCV EC50. Resistance substitutions selected by BMS-791325 in genotype 1 replicons mostly mapped to a single site, NS5B amino acid
495 (P495A/S/L/T). Additive or synergistic activity was observed in combination studies using BMS-791325 with alfa interferon
plus ribavirin, inhibitors of NS3 protease or NS5A, and other classes of NS5B inhibitor (palm site 2-binding or nucleoside
analogs). Plasma and liver exposures in vivo in several animal species indicated that BMS-791325 has a hepatotropic disposition (liver-to-plasma ratios ranging from 1.6-
to 60-fold across species). Twenty-four hours postdose, liver exposures across all species tested were ≥10-fold above the
inhibitor EC50s observed with HCV genotype 1 replicons. These findings support the evaluation of BMS-791325 in combination regimens for
the treatment of HCV. Phase 3 studies are ongoing.
... Lack of effective therapeutics for the most of viral diseases, emergence of antiviral drug resistance, and high cost of some antiviral therapies necessitate finding new effective antiviral compounds [56,57]. Additionally, the existing antiviral therapies are not always well-tolerated or quite effective and satisfactory [58]. ...
Curcuma longa L. (Zingiberaceae family) and its polyphenolic compound curcumin have been subjected to a variety of antimicrobial investigations due to extensive traditional uses and low side effects. Antimicrobial activities for curcumin and rhizome extract of C. longa against different bacteria, viruses, fungi, and parasites have been reported. The promising results for antimicrobial activity of curcumin made it a good candidate to enhance the inhibitory effect of existing antimicrobial agents through synergism. Indeed, different investigations have been done to increase the antimicrobial activity of curcumin, including synthesis of different chemical derivatives to increase its water solubility as well ass cell up take of curcumin. This review aims to summarize previous antimicrobial studies of curcumin towards its application in the future studies as a natural antimicrobial agent.
... Currently, no vaccines exist for HCV and the treatment regime of interferon-α and ribavirin is poorly tolerated, costly, and only effective in approximately 50% of patients. Recent trials of drugs that inhibit viral enzymes have been disappointing because of the rapid development of resistance by the virus (2)(3)(4) . Due to the high variability in HCV genotypes, new treatments in all likelihood will require combinations drugs targeted to multiple viral proteins in order to minimize the development of resistance. ...
Hepatitis C virus (HCV) protein p7 plays an important role in the assembly and release of mature virus particles. This small 63-residue membrane protein has been shown to induce channel activity, which may contribute to its functions. p7 is highly conserved throughout the entire range of HCV genotypes, which contributes to making p7 a potential target for antiviral drugs. The secondary structure of p7 from the J4 genotype and the tilt angles of the helices within bilayers have been previously characterized by nuclear magnetic resonance (NMR). Here we describe the three-dimensional structure of p7 in short chain phospholipid (1,2-dihexanoyl-sn-glycero-3-phosphocholine) micelles, which provide a reasonably effective membrane-mimicking environment that is compatible with solution NMR experiments. Using a combination of chemical shifts, residual dipolar couplings, and PREs, we determined the structure of p7 using an implicit membrane potential combining both CS-Rosetta decoys and Xplor-NIH refinement. The final set of structures has a backbone root-mean-square deviation of 2.18 Å. Molecular dynamics simulations in NAMD indicate that several side chain interactions might be taking place and that these could affect the dynamics of the protein. In addition to probing the dynamics of p7, we evaluated several drug–protein and protein–protein interactions. Established channel-blocking compounds such as amantadine, hexamethylene amiloride, and long alkyl chain iminosugar derivatives inhibit the ion channel activity of p7. It has also been shown that the protein interacts with HCV nonstructural protein 2 at the endoplasmic reticulum and that this interaction may be important for the infectivity of the virus. Changes in the chemical shift frequencies of solution NMR spectra identify the residues taking part in these interactions.
