bluuebunny/crossref_metadata_2025 huggingface dataset:
PAMAM Dendrimers and Branched Polyethyleneglycol (Nanoparticles) Prodrugs of (-)-β-D-(2R, 4R)-dioxolane-thymine (DOT) and Their Anti-HIV Activity
Authors: Liang Yuzeng , Narayanasamy Janarthanan , Rapp Kim L , Schinazi Raymond F , Chu Chung K
Published: March 2015

The synthesis, characterization, anti-HIV activity and cytotoxicity of dendrimers of (–)-β-D-(2 R,4 R)-dioxolane-thymine (DOT) and polyethylene glycol (PEG)–DOT conjugates are described. Dendrimers in this study were polyamidoamine (PAMAM) generation 2.0, 3.0, 5.0 and 6.0, along with 8.0-branched PEG with a molecular weight of 40 kDa. DOT was attached to PAMAM dendrimers or branched PEG via ester or phosphate groups. Size exclusion chromatography was used to purify the dendrimers and PEG conjugates, which were characterized by NMR and MALDI—TOF mass spectrometry. The synthesized PAMAM dendrimers and PEG conjugates were evaluated for anti-HIV activity against HIV-1LAI in primary human peripheral blood mononuclear cells (PBMCs) and cytotoxicity in PBMCs, CEM and Vero cells. PAMAM dendrimers of DOT with ester linkages and particularly phosphate linkers showed an increase in anti-HIV potency in comparison with DOT alone (140- and 56-fold, respectively). Unfortunately, the PAMAM dendrimers also exhibited increased cytotoxicity. Anti-HIV activity of PEG—DOT conjugates was found to be lower than that of DOT.
The Benzamide Derivative N-[1-(7-tert-Butyl-1H-indol-3-ylmethyl)-2-(4-cyclopropanecarbonyl-3-methyl-piperazin-1-yl)-2-oxo-ethyl]-4-nitro-benzamide (SP-10) Reduces HIV-1 Infectivity in Vitro by Modifying Actin Dynamics
Authors: Xu Jing , Lecanu Laurent , Tan Matthew , Yao Wenguo , Greeson Janet , Papadopoulos Vassilios
Published: March 2015

Current treatments for patients infected with HIV are suboptimal. There is a need for new HIV therapies that act through different mechanisms than current treatments. We investigated the in vitro efficacy, safety and mechanism of action of the benzamide derivative N-[1-(7-tert-Butyl-1H-indol-3-ylmethyl)-2-(4-cyclopropanecarbonyl-3-methyl-piperazin-1-yl)-2-oxo-ethyl]-4-nitro-benzamide (SP-10), a potential new HIV treatment. When HIV-1-responsive engineered HeLa cells were pre-incubated for 48 h with either SP-10 or zidovudine (AZT), SP-10 was able to inhibit viral replication at much lower concentrations (IC50=0.036 nM) than AZT (IC50=27.4 nM). In contrast to AZT, SP-10 also inhibited replication of the multidrug-resistant HIV-1 strain MDR-769 in the HeLa cell model. In co-incubation experiments, SP-10 also inhibited the CCR5-sensitive HIV-1 BaL virus replication in human peripheral blood mononuclear cells. SP-10 displayed very low toxicity compared with current antiviral treatments. Confocal laser scanning microscopy and immunoprecipitation studies showed that SP-10 reduced the expression of CD4 and CCR5 on the surface of the host cell. SP-10 also reduced the level of gp120 binding to the cell surface. Confocal laser scanning microscopy studies showed that SP-10 blocked the formation of actin filaments (F-actin) and altered actin accumulation near the cell surface. These promising results suggest that SP-10 has a novel mechanism of action that enables effective inhibition of HIV-1 binding and cell entry. Further development of SP-10 as a new HIV treatment appears warranted.
Novel HIV Integrase Inhibitors with Anti-HIV Activity: Insights into Integrase Inhibition from Docking Studies
Authors: Cox Arthur G , Nair Vasu
Published: March 2015

The mechanism of integrase is generally accepted to be dependant on the presence of two divalent metal ions in the active site. However, the only available crystal structures of HIV-1 integrase contain either one or no metal ions, hampering structure-based design studies of integrase inhibitors. For this reason, a two-metal ion model of integrase was constructed. This model was used for computational docking studies with novel diketoacid integrase inhibitors containing pyrimidine nucleobase scaffolds. The docking protocol allowed for some steric contact between the ligand and protein during docking simulations, which implicitly accounted for potential conformational changes in the protein as a result of binding viral DNA or the ligand. The results suggest that the aromatic rings in these diketo acids bind to regions close to the viral DNA and may interfere with mobility of a vital catalytic loop. The docking data also suggest that the ligand can be prevented from adopting a favourable conformation by changes in the relative orientation of its diketo side-chain and aromatic rings. The docked pose of each of the active compounds coordinated both of the metal ions present in the active site of integrase through the diketo acid functionality of these compounds. This result is more consistent with theoretical data on inhibitor mechanism, and thus recommends this docking approach over rigid use of one-metal ion models derived from current crystal structures of integrase.
The Threat of Avian Influenza H5N1: ‘Do We Have the Tools for the Job?’
Authors: Oxford John , Lambkin-Williams Robert , Mann Alex
Published: March 2015

For the first time in human history virologists have the knowledge about the avian origin of pandemic influenza A viruses. Furthermore, in the last two decades a new class of anti influenza drugs, the neuraminidase inhibitors (NIs), has been developed from an academic discovery to a series of antiviral drugs to be used in the clinic. At present vaccinologists are producing influenza A (H5N1) vaccines to be stockpiled alongside the NIs to combat the first wave of an anticipated influenza pandemic. Studies from the 1918 infection calamity, the Spanish influenza, and the succeeding pandemics of 1957 and 1968, all caused by avian influenza A viruses, have shown how quickly such a virus can mutate to become less virulent (starting with 50% case fatality) and more infectious. Such a mutation cluster could lead to a rapid increase in world deaths, currently 170, to many millions. However there are optimistic analyses: judicious and swift application of NIs, vaccine and hygiene to an outbreak epicentre, most likely in South-East Asia, could break the chain of transmission.
Mechanism of Action of (-)-(2R,4R)-1-(2-hydroxymethyl-1,3-dioxolan-4-yl)thymine as an anti-HIV agent
Authors: Murakami Eisuke , Bao Haiying , Basavapathruni Aravind , Bailey Christopher M , Du Jinfa , Steuer Holly M Micolochick , Niu Congrong , Whitaker Tony , Anderson Karen S , Otto Michael J , Furman Phillip A
Published: March 2015

(-)-(2 R,4 R)-1-(2-Hydroxymethyl-1,3-dioxolan-4-yl)thymine (DOT) is a thymidine analogue that has potent in vitro activity against wild-type and nucleoside reverse transcriptase inhibitor (NRTI)-resistant HIV. For nucleoside analogues to inhibit viral replication, they must be metabolized to the active triphosphate, which inhibits the viral reverse transcriptase (RT). Using purified enzymes, the kinetics of DOT phosphorylation, inhibition of wild-type and drug-resistant HIV-1 reverse transcriptase activity, and excision of DOT-5′-monophosphate (DOT-MP) from a chain-terminated primer were examined. DOT was phosphorylated by human thymidine kinase-1 (TK-1) but not by other pyrimidine nucleoside kinases, including the mitochondrial thymidine kinase (TK-2). Resistance to NRTIs involves decreased binding/incorporation and/or increased excision of the chain-terminating NRTI. RTs containing the D67N/K70R/T215Y/K219Q or T69S-SS/T215Y mutations show enhanced removal of DOT-MP from terminated primer as well as approximately fourfold decreased binding/incorporation. The Q151M and K65R mutations appear to cause decreased inhibition by DOT-TP. However, both the K65R and Q151M mutations show decreased excision, which would confer greater stability on the terminated primer. These opposing mechanisms could offset the overall resistance profile and susceptibility. Little or no resistance was observed with the enzymes harbouring mutations resistant to lamivudine (M184V) and non-nucleoside RT inhibitors (K103N).
Kinetics of Inhibition of HIV Type 1 Reverse Transcriptase-Bearing NRTI-associated Mutations by Apricitabine Triphosphate
Authors: Frankel Fernando A , Coutsinos Dimitrios , Xu Hongtao , Wainberg Mark A
Published: March 2015

We wished to investigate the effects of various mutations in HIV-1 reverse transcriptase (RT) on biochemical inhibition by the active form of a novel nucleoside termed apricitabine. Accordingly, we studied the efficiency of chain-termination mediated by apricitabine triphosphate (TP) in cell-free assays that used either recombinant wild-type or mutated RTs. We also performed steady-state-kinetics and primer-unblocking assays. Subtype C RTs were also analysed. The results showed that the K65R mutation in RT caused reductions in the efficiency of chain-termination of apricitabine-TP by increasing its Ki. However, K65R did not affect rates of primer unblocking for apricitabine-TP. No significant differences were found between subtype C and subtype B RTs with regard to any of the parameters studied. Other mutations such as M184V, L74V and K103N had no effect on the efficiency of chain termination by apricitabine-TP. Thus, the mechanism of reduced susceptibility to apricitabine of viruses containing K65R in RT seems to be mediated exclusively through a reduction in binding or incorporation of apricitabine-TP. Unlike some other nucleoside analogues, increased excision of incorporated apricitabine does not seem to be a cause of resistance to apricitabine.
Anticytomegalovirus Activity of Pristimerin, a Triterpenoid Quinone Methide Isolated from Maytenus Heterophylla (Eckl. & Zeyh.)
Authors: Murayama Tsugiya , Eizuru Yoshito , Yamada Rie , Sadanari Hidetaka , Matsubara Keiko , Rukung Geoffrey , Tolo Festus M , Mungai Geoffrey M , Kofi-Tsekpo Mawuli
Published: March 2015

We examined the anticytomegalovirus properties of four compounds: pristimerin, the pristimerin analogue, lupeol and 2-acetylphenol-1-β-D-glucopyranosyl (1→6)-β-D-xylpyranoside (acetophenol glycoside), isolated from Maytenus heterophylla, a Kenyan medicinal plant. The effects were studied on human cytomegalovirus (HCMV) replication in the human embryonic fibroblast cell line, MRC-5. In a viral plaque-reduction assay, pristimerin showed dose-dependent inhibitory properties with a 50% inhibitory concentration of 0.53 µg/ml (selective index=27.9). The cells treated with pristimerin inhibited the cytopathic effects in HCMV-infected cells. Moreover, pristimerin suppressed viral replication without affecting the cell growth. Pristimerin inhibited the synthesis of viral DNA but had no virucidal effect on cell-free HCMV. Furthermore, Western blot analysis demonstrated that pristimerin decreased the amount of immediate early (IE) antigen (especially IE2) expression in the infected cells. These results suggest that pristimerin is a unique compound with potential anti-HCMV activity.
Nitroimidazoles Part 6. Synthesis, Structure and in Vitro anti-HIV Activity of New 5-substituted Piperazinyl-4-nitroimidazole Derivatives
Authors: Al-Masoudi Najim A , Al-Soud Yaseen A , De Clercq Erik , Pannecouque Christophe
Published: March 2015

2-Amino-1-[4-(1-benzyl-2-ethyl-4-nitro-1 H-imidazol-5-yl)piperazin-1-yl]ethanone [6] was prepared from 1-(1-benzyl-2-ethyl-4-nitro-1 H-imidazol-5-yl) piperazine [3]. A series of new 2-oxoethyl-arylamide [9,10] and 2-oxoethyl-arylsulphonamide [11–14] derivatives were synthesized from [6] with the aim of developing new non-nucleoside reverse transcriptase inhibitors. Alternatively, the amine [17] was synthesized from [3] via the phthalimide derivative [16]. The arylsulphonamide derivatives [18–23] and the arylamide analogues [24–26] were synthesized from [17]. The compounds were evaluated for their anti-HIV-1 and anti-HIV-2 activity in MT-4 cells.
2′-C-Methyl Branched Pyrimidine Ribonucleoside Analogues: Potent Inhibitors of RNA Virus Replication
Authors: Benzaria Samira , Bardiot Dorothée , Bouisset Tony , Counor Clément , Rabeson Céline , Pierra Claire , Storer Richard , Loi Anna Giulia , Cadeddu Alessandra , Mura Massimo , Musiu Chiara , Liuzzi Michel , Loddo Roberta , Bergelson Svetlana , Bichko Vadim , Bridges Edward , Cretton-Scott Erika , Mao John , Sommadossi Jean-Pierre , Seifer Maria , Standring David , Tausek Michele , Gosselin Gilles , La Colla Paolo
Published: March 2015

RNA viruses are the agents of numerous widespread and often severe diseases. Their unique RNA-dependent RNA polymerase (RDRP) is essential for replication and, thus, constitutes a valid target for the development of selective chemotherapeutic agents. In this regard, we have investigated sugar-modified ribonucleoside analogues as potential inhibitors of the RDRP. Title compounds retain ‘natural’ pyrimidine bases, but possess a β-methyl substituent at the 2′-position of the D- or L-ribose moiety. Evaluation against a broad range of RNA viruses, either single-stranded positive (ssRNA), single-stranded negative (ssRNA−) or double-stranded (dsRNA), revealed potent activities for D-2′- C-methyl-cytidine and -uridine against ssRNA+, and dsRNA viruses. None of the L-enantiomers were active. Moreover, the 5′-triphosphates of the active D-enantiomers were found to inhibit the bovine virus diarrhoea virus polymerase. Thus, the 2′-methyl branching of natural pyrimidine ribonucleosides transforms physiological molecules into potent, broad-spectrum antiviral agents that merit further development.
The Structure-Activity Relationships of 2,4(1H,3H)-pyrimidinedione Derivatives as potent HIV type 1 and type 2 inhibitors
Authors: Buckheit Robert W , Hartman Tracy L , Watson Karen M , Kwon Ho Seok , Lee Sun Hwan , Lee Jae Woong , Kang Dong Wook , Chung Sun Gan , Cho Eui Hwan
Published: March 2015

Since the discovery of the 2,4 (1 H,3 H)-pyrimidinediones as potent non-nucleoside inhibitors of the HIV-1 reverse transcriptase (RT) this class of compounds has yielded a number of N-1 acyclic substituted pyrimidinediones with substantial antiviral activity, which is highly dependent upon their molecular fit into the binding pocket common to this inhibitory class. We have specifically examined the structure activity relationships of compounds with chemical modification made by substituting homocyclic rather than acyclic moieties at N-1 of the pyrimidinedione. Seventy-four compounds were synthesized and evaluated for antiviral activity against HIV-1 and HIV-2. The homocyclic modifications resulted in compounds with significant activity against both HIV-1 and HIV-2, suggesting these compounds represent a new class of non-nucleoside RT inhibitors. The structure-activity relationship (SAR) evaluations indicated that cyclopropyl, phenyl and 1- or 3-cyclopenten-1-yl substitutions at the N-1 of the pyrimidinedione, the addition of a methyl linker between the cyclic moiety and the N-1 and the addition of a benzoyl group at the C-6 of the pyrimidinedione had the greatest contribution to antiviral activity. Five pyrimidinedione analogues with therapeutic indexes (TIs)>450,000 and a specific analogue (1-cyclopropylmethyl-5-isopropyl-6-(3,5-dimethylbenzoyl)-2,4(1 H,3 H)-pyrimidinedione), which exhibited a TI of >2,000,000, were identified. None of the analogues were cytotoxic to target cells at the highest in vitro test concentration, which is the upper limit of compound solubility of the analogues in aqueous solution. Thus, we have identified a series of pyrimidinediones with substantially improved antiviral efficacy and range of action and with significantly reduced cellular cytotoxicity.
Isothiazole Derivatives as Antiviral Agents
Authors: Garozzo Adriana , Cutri Christian CC , Pannecouque Christophe , Castro Angelo , Guerrera Francesco , De Clercq Erik
Published: March 2015

We recently described the synthesis and antiviral activity of the compounds 5-phenyl-3-(4-cyano-5-phenylisothiazol-3-yl) disulphanyl-4-isothiazole-carbonitrile and S-(4-cyano-5-phenylisothiazol-3-yl)- O-ethyl thiocarbonate, which were found to be effective against both HIV-1 (IIIB) and HIV-2 (ROD). We have now evaluated these compounds against both RNA and DNA viruses, obtaining high selectivity indexes for poliovirus 1 (SI: 223 and 828, respectively) and Echovirus 9 (SI: 334 and 200, respectively). In our previous studies, 3-methylthio-5-(4- OBn-phenyl)-4-isothiazolecarbo-nitrile was found to exhibit a broad spectrum of action against picornaviruses, we therefore selected this compound and S-(4-cyano-5-phenylisothiazol-3-yl)- O-ethyl thiocarbonate as the model for the synthesis of a new isothiazole derivative, S-[4-cyano-5-(4- OBn-phenyl)isothiazol-3-yl]- O-ethyl thiocarbonate. This compound was evaluated against picornaviruses, measles virus, HIV-1 (IIIB) and HIV-2 (ROD), and some DNA viruses (adenovirus type 2 and herpes simplex virus type 1). The compound was shown to be active against rhinoviruses 2, 39, 86 and 89, Coxsackie B1 and measles virus.
Profound Anti-HIV-1 Activity of DAPTA in Monocytes/macrophages and Inhibition of CCR5-mediated Apoptosis in Neuronal Cells
Authors: Pollicita Michela , Ruff Michael R , Pert Candace B , Polianova Maria T , Schols Dominique , Ranazzi Alessandro , Perno Carlo-Federico , Aquaro Stefano
Published: March 2015

Monocytes/macrophages (M/M) are strategic reservoirs of HIV-1, spreading the virus to other cells and inducing apoptosis in T-lymphocytes, astrocytes and neurons. M/M are commonly infected by R5 HIV-1 strains, which use the chemokine receptor CCR5. D-Ala-peptide T-amide (DAPTA), or Peptide T, named for its high threonine content (ASTTTNYT), is a synthetic peptide comprised of eight amino acids (185–192) of the gp120 V2 region and functions as a viral entry inhibitor by targeting selectively CCR5. The anti-HIV-1 activity of DAPTA was evaluated in M/M infected with R5 HIV-1 strains. DAPTA at 10−9M inhibited HIV-1 replication in M/M by >90%. PCR analysis of viral cDNA in M/M showed that DAPTA blocks HIV entry and in this way prevents HIV-1 infection. Moreover, DAPTA acts as a strong inhibitor and was more active than the non-peptidic CCR5 antagonist TAK-779 in inhibiting apoptosis (mediated by R5 HIV-1 strains produced and released by infected M/M) on a neuroblastoma cell line. Our results suggest that antiviral compounds which interfere with receptor mechanisms such as CCR5 could be important, either alone or in combination with other antiretroviral treatments, in preventing HIV infection in the central nervous system and the consequential neuronal damage that leads to neuronal AIDS.
Development of a Population Simulation Model for HIV Monotherapy Virological Outcomes Using Lamivudine
Authors: Hurwitz Selwyn J , Asif Ghazia , Schinazi Raymond F
Published: March 2015

Current highly active antiretroviral therapy (HAART) requires the use of combinations of three drugs to minimize the early emergence of drug-resistant HIV strains. Therefore, long-term monotherapy data with new agents are unavailable. However, the development of computer models for Monte-Carlotype simulations of antiviral monotherapy, which incorporate HIV infection dynamic distributions from previously studied populations, together with pharmacokinetics and pharmacodynamic parameters of the new agent, could serve as an important tool. The nucleoside lamivudine (3TC) was used as a representative drug to standardize an improved pharmacodynamic and infection dynamic monotherapy model. 3TC plasma concentration versus time profiles was used to drive the cellular accumulation of 3TC-triphosphate (TP) in primary human lymphocytes in the model, over a 16 week period. The fraction of HIV reverse transcription inhibited was calculated using the median inhibitory concentration and intracellular 3TC-TP levels. Virus loads and activated CD4+T-cell counts were generated for 2,200 theoretical individuals and compared with the outcomes of an actual 3TC monotherapy trial at the same dose. Pharmacokinetic variance alone did not account for the interindividual HIV-load variability. However, selection of appropriate distributions of the various pharmacokinetic and infection dynamics parameters produced a similar range of virus load reductions to actual observations. Therefore, once parameter and variance distributions are standardized, this modelling approach could be helpful in planning clinical trials and predicting the antiviral contribution of each agent in a HAART modality.
Herpes Simplex Virus Helicase—Primase Inhibitors: Recent Findings from the Study of Drug Resistance Mutations
Authors: Biswas Subhajit , Field Hugh J
Published: March 2015

After several decades during which nucleoside analogues (especially acyclovir and penciclovir and their prodrugs) have benefited many patients suffering from herpes simplex virus (HSV) infections, the discovery of the helicase-primase inhibitors (HPIs) represents an interesting new approach. Although antiviral resistance has not been a major problem for nucleoside analogues in immunocompetent patients, the problem of acyclovir resistance in immunocompromised patients is well documented. Several HPIs are extremely potent antiviral compounds and may, therefore, offer an important alternative therapy in these patients. The potential for synergy, not just for the inhibition of virus replication but also to delay the appearance of drug-resistant virus, needs to be thoroughly investigated. The study of resistance to HPIs has been important towards understanding the mechanism of action of these compounds and confirming the target function. However, during the course of our studies on HPI resistance, we have made a number of interesting observations that may be relevant to their clinical use. This article draws attention to the major observations on HPI resistance reported by others and to our own recently published observations that have extended this expanding area of antiviral research.
Antiviral Activities and Phosphorylation of 5-halo-2'-Deoxyuridines and N-Methanocarbathymidine in Cells Infected with Vaccinia Virus
Authors: Smee Donald F , Humphreys Daniel E , Hurst Brett L , Barnard Dale L
Published: March 2015

Background:

The antipoxviral activities and phosphorylation of N-methanocarbathymidine ([ N]-MCT) and four 5-halo-2'-deoxyuridines, namely 5-fluoro- (FdU), 5-chloro- (CldU), 5-bromo- (BrdU), and 5-iodo- (IdU) derivatives, were explored.

Methods:

Antiviral activities and nucleoside metabolism were determined in C127I mouse, LLC-MK2 monkey, and A549 human cells infected with thymidine-kinase-containing and -deficient (TK+and TK−) vaccinia (WR strain) viruses.

Results:

The antiviral potencies of CldU, BrdU and IdU were increased 16–26-fold in LLC-MK2 cells infected with TK+compared with TK−virus infections, but enhancement of activity was much less in the other cell lines. ( N)-MCT was nearly equally active against TK+and TK−viruses in the three cell lines. Antiviral activity of FdU was associated with cytotoxicity. Uninfected and infected cells metabolized compounds to mono-, di- and triphosphates. The thymidine, BrdU and IdU triphosphate levels were higher in C127I and LLC-MK2 cells infected with TK+than with TK−virus. ( N)-MCT monophosphate levels were much higher in TK+virus-infected cells, but without corresponding increases in ( N)-MCT triphosphate. Furthermore, TK+virus infections did not appreciably alter ( N)-MCT triphosphate levels in other mouse (L929), monkey (MA-104 and Vero) and human cell lines (A549). Antiviral potency of the compounds was greater in C127I than in LLC-MK2 cells, yet lower intracellular triphosphate levels were found in C127I cells.

Conclusion:

We conclude that viral TK plays an important role in increasing the antiviral potencies of these compounds in some cell lines, but minimally in others. These findings may have implications in treating infected animals with compounds that are dependent upon poxvirus TK for their activation, because viral TK activity may vary greatly due to cell type.
Combinations of 2'-C-Methylcytidine Analogues with Interferon-α2b and Triple Combination with Ribavirin in the Hepatitis C Virus Replicon System
Authors: Bassit Leda , Grier Jason , Bennett Matthew , Schinazi Raymond F
Published: March 2015

Background:

Hepatitis C virus (HCV) polymerase is an essential enzyme for HCV replication and has multiple inhibitor binding sites making it a major target for antiviral intervention. It is apparent that no single drug can inhibit HCV replication in humans. Hence, combinations of nucleoside analogues β-D-2'- C-methylcytidine (2'- C-MeC; NM-107) or β-D-2'-deoxy-2'-fluoro-2'- C-methylcytidine (2'-F- C-MeC; PSI-6130) with interferon-α2b (IFN-α2b) or triple combination with ribavirin (RBV) were evaluated.

Methods:

Huh-7 cells containing the self-replicating subgenomic HCV replicon (Clone B) were used for drug combination studies. After drug treatment for 5 days, total cellular RNA was then extracted and both ribosomal RNA and HCV replicon RNA were amplified in a single-step multiplex real-time PCR assay. Drug interaction analyses were performed using the CalcuSyn program.

Results:

Double combinations of 2'- C-MeC or 2'-F- C-MeC with IFN-α2b at all ratios tested had weighted average combination index (CIwt) values <1 indicating synergistic inhibition of HCV replication in the replicon system. For the triple combinations of IFN-α2b plus RBV with either 2'- C-MeC or 2'-F- C-MeC, the CIwt values at 1:1:1 ratio tested were 0.5 and 0.8, respectively, indicating synergistic antiviral effects. No apparent cytotoxicity effects were observed with any of the combinations tested.

Conclusion:

These promising in vitro data warrant clinical investigation of the nucleosides analogues such as 2'- C-MeC or 2'-F- C-MeC in their prodrug forms, together with IFN-α2b and RBV, for successful treatment of HCV infections.
Antiviral Activity of Geneticin against Bovine Viral Diarrhoea Virus
Authors: Birk Alexander V , Dubovi Edward J , Zhang Xianchao , Szeto Hazel H
Published: March 2015

Background:

Aminoglycoside G418 is commonly used to generate stable replicons for RNA viruses, such as hepatitis C virus, West Nile virus, and bovine viral diarrhoea virus (BVDV). This precludes testing G418's own antiviral activities against those viruses. Here, we report antiviral activity of G418 against BVDV.

Methods:

Cell viability and virus yield reduction assays were used to investigate antiviral effects of G418 against BVDV. The expression of viral proteins and RNA were determined by western blot and real-time quantitive PCR, respectively.

Results:

We demonstrated that G418 (50% cytotoxicity concentration of 400 µg/ml) improved cell viability of Madin-Darby bovine kidney cells infected with a cytopathic strain of BVDV (NADL) in a dose-dependent manner with 50% effective concentration of 4 µg/ml. Interestingly, close structural analogues with known properties as translation inhibitors similar to G418 — kanamycin and gentamicin — had no antiviral activity against BVDV. In addition, G418 inhibits virus yield of two different strains of BVDV (NADL and NY-1) without affecting viral RNA replication and translation or viral NS3 protein processing.

Conclusion:

Our data indicate that antiviral activity of G418 could result from interference with either the assembly or release of active virus, rather than the regulation of viral translation and replication. Thus, we propose the use of chemical analogues of G418 as antiviral therapeutics for treatment of viral diseases associated with the Flaviviridae family, such as hepatitis C virus, dengue virus, yellow fever virus, West Nile virus and others.
Synthesis and Evaluation of N-Substituted Acridones as Antiviral Agents against Haemorrhagic Fever Viruses
Authors: Sepúlveda Claudia S , Fascio Mirta L , Mazzucco Maria B , Palacios Maite L Docampo , Pellón Rolando F , García Cybele C , D'Accorso Norma B , Damonte Elsa B
Published: March 2015

Background:

In the present study, a series of N-substituted acridone derivatives was synthesized and evaluated against two haemorrhagic fever viruses (HFV).

Methods:

Compounds were tested against Junin virus (JUNV), an arenavirus agent of Argentine haemorrhagic fever, and dengue virus (DENV), a flavivirus agent of the most prevalent arthropod-borne viral disease in humans.

Results:

Among tested compounds, two N-allyl acridones (derivatives 3c and 3f) elicited a potent and selective antiviral activity against JUNV (strain IV4454) and DENV-2 (strain NGC) with 50% effective concentration values between 2.5 and 5.5 µM, as determined by virus yield inhibition. No cytotoxicity was detected at concentrations up to 1,000 µM, resulting in selectivity indices > 181.8–400.0. Both acridones were effective against a wide spectrum of arenaviruses and the four serotypes of DENV. Furthermore, 3c and 3f failed to inactivate virus before cell infection as well as to induce a refractory state by cell pretreatment, indicating that the inhibitory effect was exerted through a blockade in virus multiplication during the infectious process.

Conclusion:

These data are the first demonstration that acridone derivatives have a potent antiviral activity that block in vitro multiplication of HFV belonging to Arenaviridae and Flaviviridae, such as JUNV and DENV.
Progress in the Discovery of Compounds Inhibiting Orthopoxviruses in Animal Models
Authors: Smee Donald F
Published: March 2015

Surrogate animal models must be used for testing antiviral agents against variola (smallpox) virus infections. Once developed, these compounds can be stockpiled for use in the event of a bioterrorist incident involving either variola or monkeypox virus, or used to treat an occasional serious orthopoxvirus infection, such as disseminated vaccinia complication following expo-sure to the live virus vaccine. Recently, considerable progress has been made in the discovery of novel anti-viral agents found active against orthopoxviruses in vivo. This includes the development of new animal models or refinement of existing ones for compound efficacy testing. Current mouse models employ ectromelia, cowpox and vaccinia (WR and IHD strains) viruses with respiratory (lung) or tail lesion infections commonly studied. Rabbitpox and vaccinia (WR strain) viruses are available for rabbit infections. Monkeypox and variola viruses are used for infecting monkeys. This review describes these and other animal models, and covers compounds found active in vivo from 2003 to date. Cidofovir, known to be active against orthopox virus infections prior to 2003, has been studied extensively over recent years. New compounds showing promise are orally active inhibitors of orthopoxvirus infections that include ether lipid prodrugs of cidofovir and ( S)-HPMPA, ST-246, N-meth-anocarbathymidine ( N-MCT) and SRI 21950 (a 4'-thio derivative of iododeoxyuridine). Another compound with high activity but requiring parenteral administration is HPMPO-DAPy. Further development of these compounds is warranted.
Binding Modes of Two Novel Non-Nucleoside Reverse Transcriptase Inhibitors, YM-215389 and YM-228855, to HIV Type-1 Reverse Transcriptase
Authors: Kodama Eiichi , Orita Masaya , Masuda Naoyuki , Yamamoto Osamu , Fujii Masahiro , Ohgami Tetsuro , Kageyama Shunji , Ohta Mitsuaki , Hatta Toshifumi , Inoue Hiroshi , Suzuki Hiroshi , Sudo Kenji , Shimizu Yasuaki , Matsuoka Masao
Published: March 2015

Background:

YM-215389 and YM-228855 are thiazolidenebenzenesulfonamide (TBS) derivatives and novel non-nucleoside reverse transcriptase inhibitors (NNRTIs) that inhibit not only wild-type, but also the K103N- and Y181C-substituted reverse transcriptase (RT) of HIV type-1 (HIV-1).

Methods:

To characterize the binding modes of the TBS derivatives in detail, the anti-HIV-1 activities of YM-215389 and YM-228855 against various NNRTI-resistant clones were examined. Docking studies with HIV-1 RT were also performed.

Results:

YM-215389, which effectively inhibits various NNRTI-resistant clones, interacted with L100, K103, V106 and Y318 through the benzene ring and with E138, V179, Y181, Y188 and W229 through the thiazole ring. A single amino acid substitution confers only moderate resistance to YM-215389; indeed, four amino acid substitutions (V106L, V108I, E138K and L214F) were necessary for high- level resistance. Although the activity of YM-228855, a derivative of YM-215389 that has two bulky and rigid cyano-moieties on the benzene ring, was 10x more potent against HIV-1 than YM-215389, its anti-HIV-1 activity was readily reduced with single substitutions as with Y181I and K103N.

Conclusions:

These results provide structural information for optimizing the TBS derivatives in an attempt to construct ideal NNRTIs that maintain anti-HIV-1 activity to various HIV-1 variants.
The Future of HIV Microbicides: Challenges and Opportunities
Authors: Garg Anita B , Nuttall Jeremy , Romano Joseph
Published: March 2015

HIV microbicides are topical, self-administered products aimed at preventing or reducing HIV infection in women and may represent the most promising strategy for combating the HIV/AIDS epidemic at the present time. Although a safe and effective microbicide has yet to be identified, all products tested in Phase III trials to date have been vaginal gels containing non-specific compounds with modest potency that had to be applied close to the time of sexual intercourse. Issues regarding these early generation products were further complicated by widely publicized cases of halted efficacy trials. However, as a result of each of these challenges, new information and essential lessons have emerged for the field. These lessons have resulted in a meaningful increase in microbicide development efforts focusing on compounds with highly potent and HIV-specific mechanisms of action, combination products, novel formulations, and carefully designed pharmacokinetic and pharmacodynamic evaluations, all of which are reasons for renewed confidence that a safe and effective microbicide is achievable.
Thiopurine Analogue Inhibitors of Severe Acute Respiratory Syndrome-Coronavirus Papain-Like Protease, a Deubiquitinating and deISGylating Enzyme
Authors: Chen Xin , Chou Chi-Yuan , Chang Gu-Gang
Published: March 2015

In the search for effective therapeutics against severe acute respiratory syndrome (SARS), 6-mercaptopurine (6MP) and 6-thioguanine (6TG) were found to be specific inhibitors for the SARS—coronavirus (CoV) papain-like protease (PLpro), a cysteine protease with deubiquitinating and deISGylating activity. 6MP and 6TG have long been used in cancer chemotherapy for treatment of acute lymphoblastic or myeloblastic leukaemia. Development and optimization of 6MP and 6TG will not only be important for anti-viral studies, but also for further elucidating the biological functions of cellular deubiquitinating enzymes (DUBs) and deISGylating enzymes. So far, several crystal structures of cellular DUBs have been solved. Structure comparison has been carried out to search for DUBs with a similar structure to that of PLpro, and we have tried to dock 6MP and 6TG into these DUBs to investigate the potential use of 6MP and 6TG as cellular DUB inhibitors. The best docking score and binding energy for 6MP and 6TG is against ubiquitin-specific protease (USP)14, suggesting that 6MP and 6TG are potential inhibitors of USP14. Finding new usages for old drugs will speed up the process of drug discovery and substantially reduce the cost of drug development.
HIV Dynamics and Integrase Inhibitors
Authors: Murray John M
Published: March 2015

The integrase inhibitor (INI) raltegravir has shown promising results in clinical trials to date, reducing second phase HIV RNA levels by 70% in comparison with standard regimens. These trial results have been limited by the 50 copies/ml detection limit of the HIV RNA assay and have not investigated the effect of an INI regimen on levels of latently infected cells.

Mathematical models that duplicated previous raltegravir results were extended to estimate effects of an INI regimen on HIV RNA beyond second phase and on HIV DNA levels. Depending on assumptions underlying later phase HIV RNA generation and its interaction with latently infected cells, HIV RNA in later phases can be lower or show no difference with an INI, and similarly for HIV DNA. If latent infection is maintained by differentiation of stem cells with integrated HIV DNA, then an INI regimen will eventually have no added benefit. Other hypotheses that allow ongoing replication predict continually lower HIV RNA levels with an INI regimen, but this differential effect need not translate to a reduction in latent infection.

Investigation of HIV RNA and HIV DNA levels with an INI will provide better understanding of how these components are generated and maintained under antiretroviral therapy.
Novel Compounds for the Treatment of HIV Type-1 Infection
Authors: Stellbrink Hans-Jüurgen
Published: March 2015

Despite the recent licensure of several new antiretroviral compounds, there is still a need to develop additional agents. Problems with antiviral activity, tolerability, ease of administration, extent of cross-resistance and pharmacokinetic as well as pharmacodynamic interactions still represent important obstacles to life-long control of HIV type-1 replication by highly active anti-retroviral therapy. Several compounds stem from the same classes as currently available drugs: apricitabine and elvucitabine (nucleoside reverse transcriptase inhibitors), rilpivirine (non-nucleoside reverse transcriptase inhibitor), vicriviroc and INCB009471 (CCR5 inhibitors) and elvitegravir (integrase inhibitor). The potential of other compounds with new modes of action is less clear. Currently, maturation inhibitors appear promising but for other drugs, obstacles to continued development, such as the need of parenteral application (that is, monoclonal antibodies) or toxicity (for example, immune modulating agents and pegylated interferon), are already apparent. For even more compounds in the preclinical development phase, an assessment of their possible clinical role is still premature. This review provides an overview and a summary of the current status of drug development in the field.
Synthesis and Antiviral Evaluation of 4'-alkoxy Analogues of 9-(β-D-xylofuranosyl)adenine
Authors: Kubota Yutaka , Ishizaki Nobuhide , Kaneda Yuri , Haraguchi Kazuhiro , Odanaka Yuki , Tanaka Hiromichi , Kato Nobuyuki , Baba Masanori , Balzarini Jan
Published: March 2015

Background:

Motivated by the reported biological activity of 9-(β-D-xylofuranosyl)adenine (xylo-A), the synthesis of its 4'-alkoxy analogues was carried out.

Methods:

The starting material 9-(3-deoxy-β-D-glycero-pento–3-enofuranosyl)adenine (1) was prepared from adenosine. Compound 1 was converted to the 2',5'-bis-0–(tert-butyldimethylsilyl) derivative (2) and then to the N6-pivaloyl derivative (3). When 3 was reacted with meta- chloroperbenzoic acid in the presence of a series of alcohols, the β-D-isomer of the respective 4'-alkoxy derivative was obtained exclusively in high yield. Deprotection of these products led to the isolation of the desired 4'alkoxy analogues (8a-I) of xylo-A.

Results:

Antiviral evaluation revealed that none of these analogues showed inhibitory activity against a wide variety of DNA and RNA viruses.

Conclusions:

We assume that conformational difference of the sugar moiety of 8a-1 from that of xylo-A could be attributable to their inactivity.
Mesoionic Heterocyclic Compounds as Candidate Messenger RNA Cap Analogue Inhibitors of the Influenza Virus RNA Polymerase Cap-Binding Activity
Authors: Mickleburgh Ian , Geng Feng , Tiley Laurence
Published: March 2015

Background:

An unusual feature of influenza viral messenger RNA (mRNA) synthesis is its dependence upon host cell mRNAs as a source of capped RNA primers. A crucial activity of the influenza polymerase is to steal these primers by binding and cleaving the caps from host mRNAs. The recent structural analysis of the cap-binding fragment of the influenza virus PB2 protein has highlighted the importance of the mesoionic properties of the N7-methylguanine (N7mG) component of the mRNA cap in this interaction.

Methods:

A series of mesoionic heterocycles with 5,6-fused ring systems analogous to the N7mG component of mRNA cap structures were synthesized and examined for the ability to inhibit the cap-binding activity of the influenza virus RNA polymerase complex using a bead-based in vitro cap-binding assay.

Results:

None of the compounds tested were able to significantly inhibit binding and subsequent endonucleolytic cleavage of a synthetic radiolabelled capped mRNA substrate by recombinant influenza virus polymerase in vitro.

Conclusions:

Compounds analogous to the mesoionic N7mG component of mRNA cap structures comprise a large class of potential inhibitors of the influenza virus polymerase. Although this preliminary assessment of a small group of related analogues was unsuccessful, further screening of this class of compounds is warranted.
Effect of Duration and Intensity of Ganciclovir Exposure on Lymphoblastoid Cell Toxicity
Authors: Janoly-Dumenil Audrey , Rouvet Isabelle , Bleyzac Nathalie , Bertrand Yves , Aulagner Gilles , Zabot Marie-Therese
Published: March 2015

Introduction:

Human cytomegalovirus infection is still a major complication after pediatric bone marrow transplantation and could be fatal in some cases. The toxicity of the drug in dividing transplanted haematopoietic cells combined with the suppression of cell growth caused by the virus remains a major problem in managing human cytomegalovirus infection.

Methods:

The aim of the current in vitro study was to evaluate the effect of the intensity (1–20 mg/l) and duration (1, 2, 7 or 14 days) of ganciclovir exposure on toxicity in B lymphoblastoid cells (using cell counting and viability measurements).

Results:

A correlation was found between the dose of ganciclovir exposure and a decrease in total cell number when duration exceeded 2 days (r2=0.92 and 0.93 after 7 and 14 days, respectively). High levels (20 mg/l) of ganciclovir were not more toxic than lowest levels (1 mg/l) for the shortest durations of ganciclovir exposure (1 and 2 days). Moreover, 50% cytotoxic concentrations markedly decreased with the duration of ganciclovir exposure (374–3 mg/l from 1 to 14 days respectively) after 14 days of culture.

Conclusions:

This in vitro study demonstrated for the first time that ganciclovir exhibited an in vitro duration-dependent toxicity on haematopoietic-derived cells when in vivo doses of the drug were used.
Treatment of Chronic Viral Hepatitis
Authors: Main J , McCarron B , Thomas HC
Published: March 2015

Interferon-α therapy has proved effective for up to 40% of patients with adult-acquired chronic hepatitis B virus (HBV) infection and for 20–25% of those with chronic hepatitis C virus (HCV) infection. Nucleoside analogues, such as lamivudine and famciclovir, are showing promise as antiviral agents for chronic HBV and the combination of interferon-α and ribavirin is proving to be successful therapy for 40–50% of patients with chronic HCV. In this article we review current therapy and discuss future strategies of the therapy of chronic viral hepatitis.
Regiospecific Synthesis and Anti-Human Immunodeficiency Virus Activity of Novel 5-Substituted N-Alkylcarbamoyl and N,N-Dialkyl Carbamoyl 1,2,3-Triazole-TSAO Analogues
Authors: Velázquez S , Alvarez R , Pérez C , Gago F , De Clercq E , Balzarini J , Camarasa M-J
Published: March 2015

Several 5- N-alkyl and 5- N,N-dialkylcarbamoyl substituted analogues of the anti-human immunodeficiency virus (HIV) type 1 lead compound[1-[2‘,5’-bis- O-( tert-butyldimethylsilyl)-β-D-ribofuranosyl]-5-( N,N-dimethylcarbamoyl)-1,2,3-triazole]-3‘-spiro-5“-(4”-amino-1“,2”-oxathiole-2“,2”-dioxide) have been prepared and evaluated as inhibitors of HIV-1 replication. A new regiospecific synthetic procedure is described. The compounds were prepared by cycloaddition of the appropriate glycosylazide to 2-oxo-alkylidentriphenyl-phosphoranes, followed by treatment with primary or secondary amines, to yield, exclusively, 5-substituted 1,2,3-triazole-TSAO analogues. Several 5-substituted 1,2,3-triazole-TSAO derivatives proved to be potent inhibitors of HIV-1 replication with higher antiviral selectivity than that of the parent TSAO prototype.
Oxysterols, but Not Cholesterol, Inhibit Human Immunodeficiency Virus Replication in Vitro
Authors: Moog C , Aubertin AM , Kirn A , Luu B
Published: March 2015

Oxysterols, oxygenated derivatives of cholesterol selected for their cytostatic activity and their inhibitory effect on cholesterol synthesis, have been investigated for their anti-human immunodeficiency virus (HIV) activity in vitro. The three oxysterols tested, 7β-hydroxycholesterol (7β-OHC), 25-hydroxycholesterol (25-OHC) and 7β,25-dihydroxycholesterol (7,25-OHC), inhibit viral replication at micromolar concentrations. The selectivity indexes for 7β-OHC and 25-OHC are quite modest (2 to 8) but reproducible; the dihydroxycholesterol 7,25-OHC exhibited antiviral properties at concentrations 13- to 25-fold lower than the highest concentration tested at which no toxicity was measurable. Oxysterols are naturally occurring compounds, and we speculate on their physiological relevance in HIV-infected individuals.
Characterization of Human Immunodeficiency Virus Type 1 Resistant to Modified Cyclodextrin Sulphate (mCDS71) in Vitro
Authors: Mori H , Otake T , Oishi I , Kurimura T
Published: March 2015

Drug resistance of human immunodeficiency virus type 1 (HIV) to modified cyclodextrin sulphate (mCDS71) has been analysed with respect to both the in vitro appearance of resistance to the compound and the mechanism of the acquisition of resistance. Resistant strains could be obtained in all three strains (NL432, KK-1 and A018) tested after serial passages in MT-4 cells with a gradual increase of the concentration of mCDS71. Cross-resistance both to mCDS71 and dextran sulphate 8000 was observed. As a result of sequencing analysis of the gp120 V3-C5 region of resistant strains, the mechanism of resistance can be explained in several ways: (i) substitution of sugar chain-binding amino acids, N and S; (ii) three to five amino acid deletion in V4 loop; and (iii) several mutations in V3 and V4 regions. The real cause of the resistance may be a combination of these three mechanisms. The results suggest that the target of mCDS71 is relatively widely distributed on the viral surface glycoprotein.
PMTI, a Broadly Active Unusual Single-Stranded Polyribonucleotide, Inhibits Human Immunodeficiency Virus Replication by Multiple Mechanisms
Authors: Buckheit Robert W , Lackman-Smith Carol , Snow Melinda J , Halliday Susan M , White E Lucile , Ross Larry J , Agrawal Vijai K , Broom Arthur D
Published: March 2015

Poly(1-methyl-6-thioinosinic acid), or PMTI, is a single-stranded polyribonucleotide and is the first homopolyribonucleotide devoid of Watson—Crick hydrogen bonding sites to show potent human immunodeficiency virus (HIV) inhibition. PMTI was found to be active when evaluated against a variety of low passage clinical HIV isolates in fresh human peripheral blood cells, including T cell-tropic and monocyte—macrophage-tropic viruses, syncytium-inducing and non-syncytium-inducing viruses and viruses representative of the various HIV-1 clades (A through F). The compound was active against HIV-2, all nucleoside and non-nucleoside reverse transcriptase (RT) inhibitor drug-resistant virus isolates tested and interacted with AZT or ddI to synergistically inhibit HIV infection. In biochemical inhibition assays, PMTI was determined to be a potent inhibitor of HIV-1 and HIV-2 RT, including RTs with mutations that engender resistance to nucleoside and non-nucleoside RT inhibitors. PMTI inhibited both the polymerase and RNase H activities of HIV RT. PMTI did not inhibit HIV-1 protease or integrase. Cell-based mechanism of action assays indicated that PMTI also interfered with early events in the entry of HIV into target cells. Furthermore, PMTI inhibited the fusion of gp120-expressing and CD4-expressing cells, but at concentrations approximately 1 log10 greater than those that inhibited virus entry. These results suggest that the homopolyribonucleotide PMTI blocks HIV replication in human cells at its earliest stages by multiple mechanisms, inhibition of virus entry and inhibition of RT.