bluuebunny/crossref_metadata_2025 huggingface dataset:
Human T-cell Lymphotropic Viruses: Review and Prospects for Antiviral Therapy
Authors: Palker T. J.
Published: May 2015

The human T-cell lymphotropic viruses types I and II (HTLV-I, II) pose challenges to researchers and clinicians who seek to unveil mechanisms of viral transformation and pathogenesis. HTLV-I infection in humans is associated with a wide array of primary and secondary diseases ranging from mild immunosuppression to adult T-cell leukaemia/lymphoma and HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a neurological degenerative syndrome. As retroviruses, HTLV-I and II share similar replicative cycles with human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome. However, in contrast to HIV-I which destroys CD4+ T cells, HTLV-I and II can preferentially transform a CD4+ T-cell subset to an unrestricted growth state.

HTLV-I and II, along with simian T-lymphotropic virus (STLV) and bovine leukaemia virus (BLV), form a phylogenetic group which is distinct from ungulate, non-human primate and human lentiviruses such as visna, simian immunodeficiency virus (SIV), and human immunodeficiency viruses types 1 and 2. The proviral genome of HTLV-I is flanked at the 5′ and 3′ ends by long terminal repeats (LTR) and is further subdivided into structural gag and env genes, a pro gene encoding an aspartyl protease, a pol gene which encodes reverse transcriptase and endonuclease, and the regulatory gene elements tax and rex. Regions within the LTR contain recognition sites for cellular proteins and the tax gene product that collectively promote viral expression. Tax-mediated activation of cellular genes involved in growth and differentiation is suspected to play a dominant role in the leukaemogenic process associated with HTLV-I infection. Differential rex-regulated splicing of viral message gives rise to transcripts encoding the polyprotein precursor gag-pro-pol (unspliced), envelope (single spliced), or tax/rex (doubly spliced). The 100nm HTLV virion contains an electron-dense core surrounding a divalent-single stranded DNA genome. This core is in turn enclosed by concentric shells of matrix protein and an outer lipid bilayer, the latter acquired as the virus buds from the surface of the infected cell. Envelope glycoproteins associated with the outside of this lipid bilayer can interact with viral receptors on cells and mediate virus entry. Antiviral strategies have been directed at inhibiting viral entry into cells (sulphated and non-sulphated polysaccharides, vaccines), blocking of viral replication (AZT, suramin), intracellular immunization (transdominant repression of rex), and elimination of virus infected cells (IL-2 receptor-directed toxins). Serological screening of the blood supply and curtailing breast feeding of children by HTLV-I + mothers have likely had a major impact in preventing HTLV-I infection.
The Enzymatic Synthesis and Anti-HIV Activity of 9-β-D-2-Deoxy and 9-β-D-2′,3′-Dideoxynucleossdes of 2-Aminopurine
Authors: Hicks N. , Hutchinson D. W. , Mahmood N. , Hay A. J.
Published: May 2015

The 9-β-D-2′-deoxy and 9-β-D-2′,3′-dideoxyribonucleosides of 2-aminopurine have been prepared using crude nucleoside N-deoxyribosyltransferases (E.C. 2.4.2.6) from Lactobacillus leichmannii in the presence of 10% ethylene glycol to inhibit degradation of the product nucleosides. The 2′,3′-dideoxynucleoside of 2-aminopurine is an inhibitor of the replication of HIV-1, HIV-2, and SIV with EC50 values in the range 8–100 μM depending on the cell line used and has low in vitro toxicity at its effective concentrations.
Synergistic Inhibition of Human Immunodeficiency Virus Type 1 in vitro by Interferon Alpha and Coumermycin A1
Authors: Tachedjian G. , Tyssen D. , Jardine D. , Locarnini S. , Birch C.
Published: May 2015

Interferon alpha, either leukocyte derived or the recombinant form, and the DNA gyrase inhibitor coumermycin A1 both inhibited human immunodeficiency virus type 1 (HIV) replication in vitro. We have found that combinations of these two agents synergistically inhibited HIV replication in human peripheral blood leucocytes (PBL). Significant inhibition was detected when both virion-associated reverse transcriptase activity and p24 levels were used as markers of replication. Mathematical analysis of data using the procedure of Chou and Chou (1987) produced combination indices of less than 1.0 for most effect levels at several combination ratios. Synergy was also evident when the classical isobologram technique was used for data analysis. Synergistic drug interactions were observed at concentrations not associated with cytotoxicity or anti-proliferative effects, and were seen at concentrations achievable in vivo.
Synthesis and Evaluation of Anti-Rhinovirus 1B Activity of Oxazolinyl-Isoflavans and -3(2H)-Isoflavenes
Authors: Desideri N. , Conti C. , Sestili I. , Tomao P. , Stein M. L. , Orsi N.
Published: May 2015

Oxazolinyl-isoflavans and −3(2H)-isoflavenes, substituted or not with a chlorine atom, were synthesized in order to compare their anti-rhinovirus activity with that of previously studied analogous compounds.

The activity of the oxazolines and of the esters and acids, which are intermediates in the synthesis, was studied in vitro against rhinovirus serotype 1B infection in HeLa cells. The ability of various non cytotoxic concentrations to interfere with the development of the viral cytopathic effect and plaque formation was examined.

All the tested compounds exerted a significant antiviral activity, and most of them were as active as some representative compounds of the oxazolinyl-phenoxyalkylisoxazole (WIN) series. 6-Oxazolinylisoflavan (VI) appeared to be the most interesting compound due to its high activity and therapeutic index. Among the substituted isoflavans and isoflavenes tested so far, the intermediate compound 6-chloro-3 (2H)-isoflavene-4′-carboxylic acid (XIX) was unexpectedly the most potent inhibitor of rhinovirus 1B plaque formation.
Prospects for Antiviral Chemotherapy in Veterinary Medicine: 1. Feline Virus Diseases
Authors: Rollinson E. A.
Published: May 2015

This paper, which is published in two parts, reviews the literature pertaining to antiviral chemotherapy of viruses of veterinary importance. While early reports in the 1970s referred to the chemotherapy of a number of different RNA and DNA viruses, there was considerable focus in the 1980s, initially on herpesviruses and latterly on retroviruses, particularly in cats. Details are given of the successful treatments of FeLV and FIV, which have been used as animal models for HIV therapy. The high costs of developing and registering a new chemical entity, especially for food species, in which extensive toxicity/residue data are required, is the main reason why specific antiviral compounds are not currently available for veterinary use, although some non-specific immune modulators are now emerging. Concurrent availability of appropriate diagnostic tools is a prerequisite for successful veterinary antiviral chemotherapy, as is a greater understanding of the pathogenesis of virus infections in animals and the development of more sophisticated means of drug delivery, appropriate to both food animal species and companion animals. Additionally, antiviral agents are valuable as research tools per se, as opposed to solely as chemotherapeutic agents.
5-Alkynyl Pyrimidine Nucleosides as Potent Selective Inhibitors of Varicella-Zoster Virus
Authors: Rahim S. G. , Trevidi N. , Selway J. , Darby G. , Collins P. , Powell K. L. , Purifoy D. J. M.
Published: May 2015

A series of 5-alkynyl substituted 2′-deoxyuridine and β-D-arabinofuranosyluracil nucleosides were synthesized and evaluated for in vitro activity against varicella-zoster virus (VZV). Three promising analogues, 1-(β-D-arabinofuranosyl)-5-ethynyluracil (EYaraU), 2′-deoxy-5-prop-1-ynyluridine (PYdU) and 1-(β-D-arabinof uranosyl)-5-prop-1-ynyluracil (PYaraU) had potent activity against eight strains of VZV with IC50 values averaging 1 μM. This activity was selective for VZV as the compounds were significantly less active against herpes simplex viruses (HSV) and human cytomegalovirus (HCMV) in contrast to 2′-deoxy-5-ethynyluridine (EYdU) which is highly active against all three viruses. The ability of these compounds to inhibit the growth of Vera or MRC-5 cells was over 2 orders of magnitude less than their antiviral activity (CC50 in Vero cells 350 μM for EYaraU and >500 μM for PYdU and PYaraU and >500 μM for all 3 compounds in MRC-5 cells). Direct comparative studies showed these compounds to be more potent and more selective than acyclovir (ACV).
Prospects for Antiviral Chemotherapy in Veterinary Medicine: 2. Avian, Piscine, Canine, Porcine, Bovine and Equine Virus Diseases
Authors: Rollinson E. A.
Published: May 2015

This paper, which is published in two parts, reviews the literature pertaining to antiviral chemotherapy of viruses of veterinary importance. While early reports in the 1970s referred to the chemotherapy of a number of different RNA and DNA viruses, there was considerable focus in the 1980s, initially on herpesviruses and latterly on retroviruses, and particularly in cats. Details are given of the successful treatments of FeLV and FIV, which have been used as animal models for HIV therapy. Therapy of equine, canine, bovine, porcine, avian, and fish diseases is also considered. The high costs of developing and registering a new chemical entity, especially for food species in which extensive toxicity/residue data are required, is the main reason why specific antiviral compounds are not currently available for veterinary use, although some non-specific immune modulators are now emerging. Concurrent availability of appropriate diagnostic tools is a prerequisite for successful veterinary antiviral chemotherapy, as is a greater understanding of the pathogenesis of virus infections in animals and the development of more sophisticated means of drug delivery, appropriate to both food animal species and companion animals (dogs, cats, and horses). Additionally, antiviral agents are valuable as research tools per se, as opposed to solely as chemotherapeutic agents. Part 1 covers the feline virus diseases, while part 2 includes the other viruses of veterinary importance, in dogs, horses, cattle, pigs, birds, and fish.
Ganciclovir Treatment of Murine Cytomegalovirus Infection in Mice Immunosuppressed by Prior Infection with Friend Leukaemia Virus
Authors: Smee D. F. , Pease A. , Burger R. A. , Huffman J. H. , Morrey J. D. , Okleberry K. M. , Noble R. L. , Sidwell R. W.
Published: May 2015

Since many of the severe cytomegalovirus infections in humans occur in individuals immunosuppressed by the human immunodeficiency virus, we developed an analogous murine model for studying this disease. BALB/c mice infected with the Friend retrovirus complex (FV) were immunosuppressed (i.e., exhibited reduced spleen-cell mitogenic responses and natural killer cell activity) by 21 days after FV inoculation. Challenge with murine cytomegalovirus (MCMV) at that time led to mortality at doses generally non-lethal to normal mice. Superinfection of FV-infected mice with MCMV reduced spleen cell FV infectious centres and splenomegaly, and extended the lives of mice surviving the MCMV infection. Once-daily ganciclovir treatments of 12.5,25, and 50 mg kg−1 given to dually-infected mice for 5 days starting 24 h after MCMV inoculation resulted in 90–100% survival at 14 days (relative to MCMV inoculation) compared to 15% survival in the placebo group. By 70 days, survival in the drug-treated and placebo groups were 0–5%, these deaths being attributed to FV disease. Ganciclovir treatments reduced MCMV titres in spleen, liver, and kidney during treatment (day 4 of the infection), but lung and salivary gland titres rose between days 7 and 13 in surviving animals. Improved concanavalin A-induced mitogenic responses were noted on day 4 in mice treated with 25 and 50 mg kg−1. These results indicate that the FV/MCMV dual infection in mice can be used as a model for evaluating antiviral agents. Because of the complex nature of the interaction between FV and MCMV, the model may be more appropriate for advanced studies of well-defined viral inhibitors than for routine screening of potential new compounds.
Anti-Human Immunodeficiency Virus (HIV) Activity of the Novel Antiviral Antibiotic Quartromicins which Enhance Inhibitory Effect of 3′-azido-2′,3′-dideoxythymidine (AZT) in vitro
Authors: Tanabe-Tochikura A. , Nakashima H. , Murakami T. , Tenmyo O. , Oki T. , Yamamoto N.
Published: May 2015

Novel antiviral antibiotic quartromicins A1 and D1, isolated from Amycolatopsis orientalis, significantly inhibited human immunodeficiency virus (HIV)-induced cytopathic effect and virus specific antigen expression at concentrations of 25–100 μg ml−1 In MT-4 cells infected with HTLV-IIIB. The reverse transcriptase activity of disrupted HTLV-IIIB particles, recombinant HIV-1 enzyme, and purified avian myeloblastosis virus (AMV) enzyme were also significantly inhibited by quartromicins A1 and D1. The combined antiviral effect of quartromicin A1 and AZT on the replication of HIV in MT-4 cells was also examined. Quartromicin A1 synergistically enhanced the inhibitory effect of AZT as revealed by HIV-specific antigen expression.
Synthesis and anti-HIV Activity of a Series of 2-Indolinones and Related Analogues
Authors: Smallheer J. M. , Otto M. J. , Amaral-Ly C. A. , Earl R. A. , Myers M. J. , Pennev P. , Montefiori D. C. , Wuonola M. A.
Published: May 2015

A novel series of 2-indolinones with in vitro anti-HIV (human immunodeficiency virus) activity is described. Two structurally related compounds, 1, 3,3-(4- N-methyl-1,2,5,6-tetrahydropyridylmethyl)-1- phenyl-2-indolinone, and 2, its 4- N-methylpiperidinylmethyl analogue (Fig. 1), formed the basis of a structure-activity study. The synthesis of approximately 50 analogues and their respective activities vs. HIV are presented. Both 1 and 2 were effective inhibitors of HIV(IIIb) in cell protection assays with IC90 values of 4.4 and 14.9μM (2.2 and 7.9μg ml−1), respectively. In the same concentration range, 1 and 2 also inhibit syncytia formation. These compounds represent a novel class of anti-HIV agents which appear to act by inhibiting virus-dependent cell fusion.
Antiviral Agents of Plant Origin. Antiherpetic Activity of Acacetin
Authors: Hayashi K. , Hayashi T. , Arisawa M. , Morita N.
Published: May 2015

The effect of acacetin isolated from Scoparia dulcis and several related flavonoids on herpes simplex virus type 1 (HSV-1) was studied in vitro by the method of plaque yield reduction. Among these compounds, acacetin was shown to be the most potent agent and caused dose-dependent inhibition of virus replication. Acacetin had a weak virucidal activity at higher concentrations. Analysis of early events following infection showed that attachment of the virus to host cells and penetration were unaffected by acacetin. Acacetin was found to exert strong inhibition of protein synthesis in virus-infected cells but not in uninfected cells. The transcription of immediate-early genes and translation of their transcripts were in particular almost stopped by acacetin even at a lower concentration. These selective effects can be attributed mainly to the antiviral activity of acacetin.
Alpha-Cyclodextrin Sulphate, an anti-HIV Agent, Retains its Antiviral Effect in the Presence of Hydrocortisol Phosphate
Authors: Pitha J. , Anand R.
Published: May 2015

Cyclodextrin sulphates alpha (a) and beta (b) were found to be inhibitors of replication of human immunodeficiency virus (HIV-1) in phytohaemagglutinin (PHA)-stimulated human peripheral blood mononuclear cells (PBMC); the same cells were also stimulated to proliferate (Anand et al., 1990). B-Cyclodextrin sulphate was also found to stimulate another, more complex, cell proliferation-neovascularization process in rabbit cornea (Folkman et al., 1989). Since the process of neovascularization is generally associated with progression of tumour growth and other pathologies, it is obvious that its stimulation by an antiviral compound may be a serious side effect. Nevertheless endotoxin-induced neovascularization can be suppressed by simultaneous treatment with b-cyclodextrin sulphate and glucocorticoids (Folkman et al., 1989). The same co-treatment may possibly be used to improve antiviral action of cyclodextrin sulphates, but such a combination therapy may not be free of complications. Glucocorticoids also affect the stability of various cellular membranes. Treatment of cells in vitro by glucocorticoids is known to stabilize their lysozymes. Glucocorticoids affect both the proliferative capacity of the cells (Cristofalo, 1972) and cytopathic effects of rabies viral infection. Furthermore, it has been reported that the cytopathic effects of rabies and of yellow fever viruses were inhibited while those of the polio virus were only mildly affected (Hannoun et al., 1965). Consequently, in this work we evaluated effects of a glucocorticoid and of glucocorticoid-a-cyclodextrin sulphate combination on HIV-1 replication.
Phosphoramidate Derivatives of AZT as Inhibitors of HIV: Studies on the Carboxyl Terminus
Authors: McGuigan C. , Pathirana R. N. , Choi S. S.-M. , Kinchington D. , O'Connor T. J.
Published: May 2015

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridate chemistry. These materials carry carboxy-protected, amino acids, and are designed to act as membrane-soluble prodrugs of the bio-active free nucleotides. In vitro evaluation revealed the compounds to have a pronounced, selective antiviral activity. In particular, variation in the carboxy terminus region is studied. For alkyl phosphates small changes in the structure of the amino ester lead to marked changes in biological activity. However, for analogous aryl phosphates there is little dependence on the structure of the ester. This suggests a different mechanism of action for these two categories of phosphate prodrug.
Antisense Nucleic Acids — Prospects for Antiviral Intervention
Authors: Tonkinson J. L. , Stein C. A.
Published: May 2015

Antisense oligodeoxynucleotides are a promising new class of antiviral agent. Because they bind in a sequence-specific manner to complementary regions of mRNA, oligos can inhibit gene expression in a sequence-specific manner. The ‘antisense’ approach has been used successfully to block cellular expression and replication of several viruses including Human Immunodeficiency Virus-1 (HIV-1), and Herpes Simplex Virus (HSV). However, the antiviral effect of oligodeoxynucleotides is not limited to sequence-specific inhibition of gene expression. Non sequence-specific effects are frequently observed, presumably as a result of their properties as polyanions. Occasionally (e.g. for HIV-1) these non sequence-specific effects are also therapeutic. The prospects for antisense oligodeoxynucleotide therapy for viral disease are discussed.
Inhibition of HIV Infection by Caffeoylquinic Acid Derivatives
Authors: Mahmood N. , Moore P. S. , De Tommasi N. , De Simone F. , Colman S. , Hay A. J. , Pizza C.
Published: May 2015

The caffeoylquinic acids 3,4,5-tri-O-caffeoylquinic acid (1) and 4,5-di-O-caffeoylquinic acid (2), as well as caffeic acid (4) and synapoic acid (5) were isolated from the plant Securidaka longipedunculata (polygalaceae). 1 exhibited a greater selective inhibition of HIV replication than 2 which had an anti-HIV activity similar to that of 3,4,5-tri-O-galloylquinic acid (3), isolated from Guiera senegalensis (combretaceae); 4 and 5 were ineffective and the structurally related compound rosmarinic acid (6) had only slight anti-HIV activity. Studies of the actions of these compounds suggest that inhibition of the viral reverse transcriptase in vitro is non-specific and that they act by specific binding to gp120 which prevents its interaction with CD4 on T-lymphocytes and thus inactivates virus infectivity.
Synergistic Inhibition of Primary Isolates of Human Immunodeficiency Virus Type 1 by Combinations of 3′-Fluoro-3′-Deoxythymidine and 2′,3′-Dideoxyinosine
Authors: Cox S. W. , Albert J. , Aperia K. , Wahren B.
Published: May 2015

We examined the antiviral effect against human immunodeficiency virus type 1 of 3′-fluoro-3′-deoxythymidine and 2′,3′-dideoxyinosine, both alone and in combination. Primary isolates of human immunodeficiency virus were used directly after isolation on peripheral blood mononuclear cells, without culturing on established cell lines, in order to maintain close similarity to the clinical situation. All isolates were synergistically inhibited by combinations of the drugs, though their susceptibility to the separate drugs varied. The selectivity indices of the combinations were similar to that of the individual drugs. The synergistic combination of 3′-fluoro-3′-deoxythymidine and 2′,3′-dideoxyinosine appears promising for the treatment of human immunodeficiency virus infection and deserves further investigation.
Effect of Ribavirin on Hela Cells Expressing E. coli Xanthine-Guanine Phosphoribosyl Transferase
Authors: Andersen D. O. , Murray B. K. , North J. A.
Published: May 2015

HeLa cells expressing the E. coli gene Ecogpt and cultured with xanthine were extremely resistant to antiproliferation by mycophenolic acid, but were only partially resistant to the effects of ribavirin. Nucleotide analyses of these transfected cells, and the parental HeLa cells, demonstrated an association between the GTP/ribavirin triphosphate ratio and virus yield reductions.
Brain Targeting of anti-HIV Nucleosides: Ether Prodrugs of 3′-Azido-2′,3′-Dideoxyuridine (AZdU) and 3′-Azido-3′-Deoxythymidine (AZT)
Authors: Doshi K. J. , Islam Q. , Gallo J. M. , Boudinot F. D. , Hsieh L. , Qin Y. , Schinazi R. F. , Chu C. K.
Published: May 2015

In an effort to increase the brain delivery of anti-HIV nucleosides, 5-0-benzyl and glucose derivatives of 3′-azido-2′,3′-dideoxyuridine (AZdU or CS-87) and 3′-azido-3′-deoxythymidine (AZT) were synthesized. In vitro stability and pharmacokinetic studies in mice were conducted with benzyl AZdU (BzlAZdU), benzyl AZT (BzlAZT), and glucose AZdU (GAZdU) prodrugs. In vitro studies indicated that the prodrugs were stable in phosphate buffer (pH 7.4), human serum and mouse serum. In mouse brain homogenate, the degradation half-lives for BzlAZdU, BzlAZT, and GAZdU were 1.66, 2.06, and 0.98 h, respectively, and in liver homogenate the degradation half-lives were 0.49, 0.29, and 1.97h, respectively. Following intravenous administration of BzlAZdU, BzlAZT, or GAZdU to mice, prodrug and parent drug concentrations were measured in serum and brain by HPLC, and pharmacokinetic parameters determined. The brain:serum area under the concentration time-curve (AUC) ratio, a parameter indicative of prodrug uptake into brain, was 0.55 for BzlAZdU and 0.56 for BzlAZT, compared to 0.05–0.08 when the parent drugs AZdU and AZT were administered intravenously. GAZdU had poor brain penetration, achieving brain concentrations of only 5% of the serum concentrations. Parent drug concentrations in brain were, for the most part, not detected after administration of any of the prodrugs. Consistent with in vitro data, it is apparent that the prodrugs were converted to metabolites other than the parent drug species.
Effect of G-CSF and M-CSF on the in vitro Toxicity Associated with Zidovudine in Normal Human Bone Marrow Haematopoietic Progenitor Stem Cells
Authors: Gallicchio V. S. , Hughes N. K.
Published: May 2015

Zidovudine, the antiviral drug used in the treatment of acquired immunodeficiency syndrome (AIDS), causes toxicity to the haematopoietic system. Although use of the haematopoietic growth factors, GM-CSF and erythropoietin have been investigated in clinical trials to modulate antiviral toxicity, there is scant data which supports their ability to ameliorate zidovudine induced toxicity on haematopoietic progenitor cells when combined in vitro. We describe here the results of studies designed to evaluate the capacity of additional haematopoietic factors such as granulocyte-colony stimulating factor (G-CSF) and macrophage-colony stimulating factor (M-CSF) to modulate zidovudine-induced toxicity on G-CSF and M-CSF dependent-colony formation in the presence or absence of zidovudine in vitro. These factors were also studied combined with erythropoietin in culture for the early erythroid progenitor BFU-E using adherent, T-cell, depleted normal human bone marrow cells in the presence or absence of zidovudine. In the presence of zidovudine at the concentration producing 50% inhibition of G- and M-CSF dependent colony formation, (5 × 10−5M), dose-escalation of either G-CSF or M-CSF failed to ameliorate zidovudine toxicity. However, in the presence of zidovudine at the concentration that produces 50% inhibition of BFU-E (5 × 10−9M), and optimal erythropoietin (1 unit ml−1), G-CSF ameliorated zidovudine inhibition of BFU-E, which was not observed with M-CSF. In the presence of erythropoietin, G-CSF increased significantly normal BFU-E. These studies indicate that G-CSF may be useful in ameliorating zidovudine-induced anaemia and suggest G-CSF may act as a synergistic factor to enhance erythropoietin to support the growth of erythroid progenitors in conditions where erythropoitin is ineffective.
In vitro Selection of Human Immunodeficiency Virus Type 1 Resistant to Ro 31-8959 Proteinase Inhibitor
Authors: Dianzani F. , Antonelli G. , Turriziani O. , Riva E. , Dong G. , Bellarosa D.
Published: May 2015

Human immunodeficiency virus type I (HIV-1) resistant to the proteinase inhibitor Ro 31–8959 has been obtained by growing HIV-IIIB in C8166 cell cultures in the presence of inhibitory concentrations of the drug.

Ro 31-8959-resistant HIV-1 obtained after five passages in the presence of the drug was capable of replicating, as measured by infectious virus yield, in the presence of concentrations of Ro 31-8959 able to inhibit completely the replication of the parental HIV-IIIB.

Cloning of the Ro 31–8959-resistant viral preparations revealed that a number of different strains of HIV-1 with various degrees of sensitivity to Ro 31–8959 emerged during propagation of HIV-IIIB in C8166 cells in the presence of the drug. The most resistant strain shows an ID50 value of 21.8 nM that is 13.2 fold higher than the value observed in HIV-IIIB infected C8166 cells.
Protective Effect of Carrageenan against Murine Cytomegalovirus Infection in Mice
Authors: Hamasuna R. , Eizuru Y. , Shishime Y. , Minamishima Y.
Published: May 2015

The protective effect of iota-carrageenan (CAR) was evaluated against murine cytomegalovirus (MCMV) infection in mice. Female ICR mice were challenged intraperitoneally (i.p.) with 3 LD50 of salivary gland-passaged MCMV. More than 0.5 mg of CAR showed a protective effect on mice only when CAR was administered i.p. and then MCMV was inoculated i.p. The protective effect of CAR was evidenced by an increase in plaque-forming unit per LD50 and a decrease in the titre of infectious viruses in the target organs. Neither a virucidal nor a virustatic effect on MCMV was evidenced for CAR. The protective effect of CAR seemed to be host-mediated.

Pretreatment of mice with CAR augmented natural killer (NK) activity of the spleen cells without elevating the serum interferon level. However, administration of anti-asialo GM1 antibody did not nullify the inhibitory effect of CAR on virus replication in the target organs. MCMV infection induced leukopenia including neutropenia and lymphopenia in saline-treated mice. Pretreatment with CAR protected mice from those signs, except for slight lymphopenia. Administration of cyclophosphamide induced severe leukopenia including neutropenia and lymphopenia even in CAR-treated mice. Under such conditions, the protective effect of CAR against MCMV infection was abrogated by cyclophosphamide. Thus, the protective effect of CAR seems to be non-NK-mediated.
Synthesis and Antiviral Activity of 9-alkoxypurines: New 9-(hydroxyalkoxy) Derivatives of Guanine and 8-methylguanine
Authors: Bailey S. , Harnden M. R. , Shanks C. T.
Published: May 2015

A number of 9-(hydroxyalkoxy) derivatives of guanine (27a-h and 27l-n) and of 8-methylguanine (27i-k) have been synthesized and evaluated as antiviral agents against herpes viruses (HSV-1, HSV-2, VZV) and visna virus, a lentivirus. The synthesis Involved reaction of hydroxyl-protected derivatives of hydroxyalkoxy-amines (6a-m) with 4,6-dichloro-2,5-diformamidopy-rimidine (24) followed by cyclization of the resultant 6-alkoxyaminopyrimidines (25a-m) to either guanine derivatives (27a-h and 27l-n) or 8-methylguanine derivatives (27i-k). Modest antiviral activity was seen with 27b, 27c, 27f, 27i and 271 against the herpesvirus and with 27e and 27m against visna virus. Only 27e showed any cytotoxicity in MRC-5 cells at concentrations ≤400μM.
Antiviral Activity of a Keggin Polyoxotungstate PM-19 against Herpes Simplex Virus in Mice
Authors: Ikeda S. , Nishiya S. , Yamamoto A. , Yamase T. , Nishimura C. , De Clercq E.
Published: May 2015

The in vivo activity of the Keggin polyoxotungstate PM-19 [K7(PTi2W10O40)·6H2O] was investigated against herpes simplex virus type 2 (HSV-2) in ddY mice. A single dose of PM-19 at 100mg kg−1administered intraperitoneally (i.p.) immediately after i.p. infection of ddY mice with HSV-2 offered 92% protection against an otherwise lethal HSV-2 infection. PM-19 was less or not effective if given by any route other than the i.p. route. When repeated doses of PM-19 were administered i.p. on day 0 (immediately after infection) and day 1 and 2 after infection, it proved protective over a dosage range of 0.1-50 mg kg−1day−1, its ED50 (50% effective dose, based on the number of survivors) being 0.25 mg kg−1day−1. Under these conditions, ACV was not effective even at doses up to 100 mg kg−1day−1.
Discovery of a Drug Lead Employing a Peptide Library: Inhibition of HIV-1 Tat and Viral Replication by the Tripeptide YPG-NH2
Authors: Coffen D. L. , Huang T.-N. , Ramer S. E. , West R. C. , Connell E. V. , Schutt A. D. , Hsu M.-C.
Published: May 2015

A library of the 8000 tripeptides derivable from coded amino acids was prepared in 20 sets of 400 using solid phase synthesis on a benzhydrylamine resin. The peptide mixtures, as C-terminal amides, were screened for inhibition of secreted alkaline phosphatase expression in a cellular (COS) system wherein a transfected SeAP gene construct was under control of the HIV-1 LTR promoter, activated by the product of a cotransfected HIV Tat gene construct. Thus, YPG-NH2 was discovered as an inhibitor of HIV-1 Tat function and then shown to block HIV replication in a CD4+ T-cell line (CEM) with IC50 = 35μM.
Synthesis, Oral Bioavailability and in vivo Activity of Acetal Derivatives of the Selective Antiherpesvirus Agent 9-(3-hydroxypropoxy) Guanine (BRL 44385)
Authors: Harnden M. R. , Ashton R. J. , Boyd M. R. , Jennings L. J. , Sutton D. , Wyatt P. G.
Published: May 2015

Acyclic acetal derivatives of the selective antiherpesvirus agent 9-(3-hydroxypropoxy) guanine (BRL44385) and of its 2-aminopurine congener (BRL46720) have been prepared and evaluated in mice for oral delivery of BRL 44385. Guanine derivatives (6 a-c) were prepared via Mitsunobu condensation of an alcohol with a 9-hydroxy-6-methoxypurine (Harnden and Wyatt, 1990). Synthesis of derivatives of 2-aminopurine (10 a-d) was achieved by hydrogenolysis of 9-alkoxy-6-chloropurines, which were obtained either by reaction of an alkoxyamine with 4,6-dichloro-2,5-diformamidopyrimidine and subsequent ring closure or by Mitsunobu condensation of an alcohol with a 6-chloro-9-hydroxypurine. Following oral administration, 2-amino-9-[3-(iso-propoxymethyl)propoxy]-purine (10b, BRL 55792) was very well absorbed and provided high and prolonged concentrations of BRL44385 in the blood. In a cutaneous HSV-1 infection in the ear pinna of mice, orally dosed BRL 55792 was at least 3-fold more potent than both BRL44385 and Acyclovir in reduction of lesion severity.
Inhibition of the Cellular Rev Response and HIV-1 Replication by 8-Alkyl-2-(4-pyridyl)pyrido[2,3-d pyrimidin-5(8H)-Ones
Authors: Ciccarelli R. B. , Winter L. A. , Lorenz R. , Harris A. L. , Crawford A. C. , Bailey T. R. , Singh B. , Hammarskjöld M.-L. , Rekosh D. , Hughes J. V.
Published: May 2015

A high-capacity, 96-well plate assay in COS-1 cells was developed to screen for inhibitors of the essential HIV-1 Rev response. The assay used Rev-induced expression and cell excretion of the p24 protein from the HIV-1 gagpol gene as a readout. Co-expression of β-galactosidase was used as a specificity control. Using this assay as a drug discovery screen, the authors discovered a series of 8-alkyl-2-(4-pyridyl)pyrido[2,3- d]pyrimidin-5(8 H)-ones that inhibited the primary Rev response in COS-1 cells with IC50s in the range 2-20 μm. These compounds also inhibited HIV-1 strain IIIB replication in human H9 cells (T-cell lymphoma) with IC50s in the same concentration range. Limited structural information suggests that alkyl substituent on N(8) influences potency of this series. These compounds might be the first reported small-molecule inhibitors of HIV-1 replication which act by inhibiting the essential Rev response; further studies in T-cells are in progress to confirm this hypothesis.
Inhibition of Influenza Virus A/WSN Replication by Serine Protease Inhibitors and anti-Protease Antibodies
Authors: Someya A. , Tanaka N. , Okuyama A.
Published: May 2015

The serine protease inhibitors, aprotinin and 6-amidino-2-naphthyl-p-guanidinobenzoate (Futhan), showed striking antiviral activity in the plaque assay of the canine kidney (MDCK) cell-WSN strain system. Anti-cathepsin B IgG antibody/showed the greatest inhibitory effect on plaque formation, followed by anti-factor X antibody and then anti-plasminogen antibody. Anti-cathepsin B antibody inhibited the proteolytic cleavage of haemagglutinin (HA). These results suggest that a serine protease-like enzyme and the other protein that binds to anti-cathepsin B antibody may be involved in the process of WSN HA cleavage on the membrane surface of MDCK cells.
Inhibition of Thymidylate Synthetase Activity Induced in Varicella-Zoster Virus Infected Cells by (E)-5-(2-bromovinyl)-2′-deoxyuridine
Authors: Yokota T. , Konno K. , Shigeta S.
Published: May 2015

The authors investigated the effect' of thymidylate synthetase (TS) on the antivariclllazoster virus (VZV) activity of ( E)5-(2-bromovinyl)-2′-deoxyuridine (BVDU). TS catalyses the conversion of deoxyuridylate (dUMP) to thymidylate (dTMP) and is a key enzyme in pyrimidine biosynthesis, providing the only source of dTMP synthesized de novo in mammalian cells. VZV encodes a specialized viral form of TS. TS activity in cells infected with VZV (TIO-VZV and TK−-VZV) increased proportionally with focus formation. From kinetic analysis using the Michaelis-Menten equation, the authors determined a Km value of 6.6μm for dUMP of TS induced in VZV-infected cells and a corresponding value from mock-infected cells of only 2.8μm. BVDU inhibited the induction of TS activity in TK+-VZV-infected cells at concentrations under ×10−3μm, but did not inhibit TS activity of TK−-VZV- or mock-infected cells at concentrations as high as 10μm. Inhibitory activity of BVDU against TS induced in TK+-VZV-infected cells appears to occur when BVDU is phosphorylated to BVDU monophosphate by viral pyrimidine kinase. These results suggest that the selective inhibitory action of BVDU on VZV replication depends on a specific interaction with both viral TK and TS. 5-Bromodeoxyuridine and 5-iododeoxyuridine inhibited TS activities induced in both VZV (TK+, TK−) and mock-infected cells. Other antiherpes compounds [i.e. 1-β-D-arabinofuranosyl- E-5-(2-bromovinyl)uracil, 9- 2-hydroxyethoxymethyl)-guanine, arabinosyladenine, and others] did not inhibit TS activity in VZV-infected cells at concentrations Of 10μm.
Synthesis and Structure Activity Relationships of a Series of Penicillin-Derived Pseudosymmetric Inhibitors of HIV-1 Proteinase
Authors: Humber D. C. , Bamford M. J. , Bethell R. C. , Cammack N. , Orr D. C. , Storer R. , Weingarten G. G. , Wyatt P. G.
Published: May 2015

The synthesis from penicillin G of a series of potent pseudosymmetric inhibitors 11 a-k of HIV-1 proteinase is described. The 2-pyridyl substituted compounds 11a and 11j showed improved antiviral activity compared to their C2-symmetric counterparts 3 and 4.
Studies on Orally Available Inhibitors of HIV Protease. Peptidyl Aldehydes and Trifluoromethyl Ketones
Authors: Hodge C. N. , Aldrich P. E. , Fernandez C. H. , Otto M. J. , Rayner M. M. , Wong Y. N. , Erickson-Viitanen S.
Published: May 2015

Low-molecular-weight peptidyl aldehyde inhibitors of HIV protease that reach in vivo plasma concentrations after oral administration substantiailly in excess of the antiviral IC90 are described. We also report efforts to improve the potency and stability of these compounds that culminated in a series of peptidyl trifluoromethyl ketones with increased potency but decreased bioavailability.
Human Brain Tumour Cell Lines as Cell Substrate to Demonstrate Sensitivity/Resistance of Herpes Simplex Virus Types 1 and 2 to Nucleoside Analogues
Authors: Andrei G. , Snoeck R. , De Clercq E.
Published: May 2015

Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) grow in vitro in a broad range of human and animal cells. Here we describe the activity of several nucleoside and nucleotide analogues against HSV-1 and HSV-2 in human brain-tumour-derived cells. Of the compounds tested, ( E)-5-(2′-bromovinyl)-2′-deoxyuridine (BVDU) proved to be the most potent inhibitor of the wild-type, thymidine-kinase-positive (TK+) HSV-1. In contrast to BVDU, acyclovir and ganciclovir, which were virtually inactive against TK− HSV-1, the two acyclic nucleoside phosphonates ( S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and ( S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) were equally active against TK+ and TK− HSV-1 strains. Depending on the brain tumour cell line used, differences in virus-drug sensitivity varied up to 30-fold. Upon passage of the virus in the brain tumour cell lines in the presence of the compounds, virus resistance developed rapidly to BVDU, acyclovir and foscarnet but not to HPMPC. Furthermore, the HSV-1 mutant that had become resistant to BVDU, acyclovir or foscarnet remained as sensitive to HPMPC and HPMPA as did the wild-type HSV-1 (KOS strain).
Dipyridamole Potentiates the Activity of Various Acyclic Nucleoside Phosphonates against Varicella-Zoster Virus, Herpes Simplex Virus and Human Cytomegalovirus
Authors: Snoeck R. , Andrei G. , Balzarini J. , Reymen D. , De Clercq E.
Published: May 2015

Dypiridamole (DPM) is widely used in the treatment of cardiovascular diseases as a coronary vasodilator and inhibitor of platelet aggregation. Phosphonylmethoxyethyl (PME) and 3-hydroxy-2-phosphonylmethoxypropyl (HPMP) derivatives of purines and pyrimidines are potent and selective inhibitors of varicella-zoster virus (VZV), herpes simplex virus (HSV) and human cytomegalovirus (HCMV). We have found that DPM markedly potentiates the antiviral effects of the PME derivatives of adenine (PMEA) and 2,6-diaminopurine (PMEDAP), and of the HPMP derivatives of adenine (HPMPA), 3-deazaadenine (HPMPc3A) and cyclic HPMPA (cHPMPA). This was reflected by a significant decrease in the 50% inhibitory concentration of the acyclic nucleoside phosphonates for VZV-, HSV- and HCMV-induced cytopathic effect or plaque formation. DPM did not enhance the activity of vidarabine, acyclovir or ganciclovir. These results were confirmed by virus yield assays (for HSV and HCMV) and flow cytometry (for VZV).
[Melle4]Cyclosporin, a Novel Natural Cyclosporin with anti-HIV Activity: Structural Elucidation, Biosynthesis and Biological Properties
Authors: Traber R. , Kobel H. , Loosli H.-R. , Senn H. , Rosenwirth B. , Lawen A.
Published: May 2015

From fermentations of Tolypocladium niveum supplemented with D-threonine, a novel natural cyclosporin, [Melle4]cyclosporin, was isolated. Its structural elucidation is based on amino acid analysis and spectroscopic data; the amino acid sequence was deduced from two-dimensional NMR investigations applied to the iso-derivative of [Melle4]cyclosporin which, in contrast to the natural product, is present as one homogenous conformation in solution. We show that one of the four N-methyl-L-leucine units of cyclosporin A, namely that in position 4, is replaced by N-methyl-L-isoleucine. The putative mechanism by which D-threonine induces in vivo biosynthesis of [Melle4]cyclosporin is discussed. In vitro biosynthesis of [Melle4]cyclosporin was achieved using the previously described enzymatic system [Lawen and Traber (1993) J Biol Chem268: 20452–20465], thereby demonstrating the high affinity of cyclosporin synthetase for isoleucine in position 4.

In a long series of cyclosporins obtained by in vitro and in vivo biosynthesis, [Melle4]cyclosporin represents the first example that is devoid of immunosuppressive efficacy while retaining strong binding to cyclophilin. It exerts potent in vitro anti-HIV-1 activity.
Antiviral Portrait Series: 4. Polysuifates as Inhibitors of HIV and Other Enveloped Viruses
Authors: Witvrouw M. , Desmyter J. , De Clercq E.
Published: May 2015

Polysulfates are highly potent and selective inhibitors of the in vitro replication of HIV and other enveloped viruses. They not only inhibit the cytopathic effect of HIV, but also prevent HIV-induced syncytium (giant cell) formation. They also act synergistically with other anti-HIV drugs. The anti-HIV activity of polysulfates is a result of their shielding of the positively charged sites in the V3 loop of the viral envelope glycoprotein gp120. When polysulfates were administered intravenously to rabbits, their half-life was approximately 2h. Although they are very poorly absorbed following oral administration, they can be made orally bioavailable with the appropriate chemical modifications. Also, polysulfates may lose (much of) their anticoagulant activity upon chemical modification without giving up their anti-HIV activity. Their efficacy in the therapy and/or prophylaxis of retroviral infections remains to be demonstrated both in animal models and in humans.
Fluorinated Analogues of the p17/p24 Sequence Incorporating 3-fluoro and 3,3-difluoro Phenylalanines as Potential Inhibitors of HIV Protease
Authors: Frogier P. R. T. , Tran T. T. , Viani S. , Condom R. , Guedj R.
Published: May 2015

The synthesis and activity of a series of fluorinated peptide analogues of the p17/p24 sequence incorporating 3-fluoro and 3,3-difluoro phenylananines at the P1 position of the scissile bond are described. It was hoped that these might act as potent inhibitors of HIV protease. In fact, none of the compounds studied displayed any anti-HIV activity in vitro. This may be attributed to poor cell penetration of the compounds and metabolic cleavage of their peptide bonds.
Synthesis, and Some Properties of, Amphiphilic Dinucleoside Phosphate Derivatives of 3′-azido-2′,3′-dideoxythymidine (AZT)
Authors: Schott H. , Häussler M. P. , Gowland P. , Horber D. H. , Schwendener R. A.
Published: May 2015

N4-hexadecyl-5′-0-(4-monomethoxytrityl)-2′-deoxycytidine-3′-hydrogenphosphate was reacted with 3′-azido-2′,3′-dideoxythymidine (AZT) according to the hydrogenphosphate method to yield N4-hexadecyl-2′-deoxycytidylyl-(3′-5)-3′-azido-2′,3′-dideoxythymidine. N4-palmitoyl-5′-O-(4-monomethoxytrityl)-2′-deoxycytidine-3′-(2-chlorophenyl)-phosphate was condensed to AZT using the triester method to give N4-palmitoyl-2′-deoxycytidylyl-(3′-5′)-3,-azido-2′,3′-dideoxythymidine. Both dinucleosidephosphates have amphiphilic properties and represent a new class of AZT derivatives in which the polar AZT-5′-monophosphate is masked with lipophilic deoxycytidine residues of variable stability. The AZT derivatives are water soluble, by forming micelles, and as a result of their amphiphilic nature, they can be incorporated into the lipid membranes of liposomes. In contrast to the micellar drug preparations, the liposomal formulations were shown to exert no lytic activity on human erythrocytes. Both AZT derivatives have anti HIV-1 activity in vitro.
Intracellular Metabolism of 3′-azido-3′-deoxythymidine and 2′,3′-dideoxyinosine in Combination in the Absence and Presence of Ribavirin
Authors: Palmer S. , Cox S.
Published: May 2015

We examined the intracellular phosphorylation of 3′-azido-3′-deoxythymidine (AZT) and 2′,3′-dideoxyinosine (ddl) and the effects on rNTP and dNTP pools when AZT and ddl were incubated separately and in combination in lymphocytes. We also compared the effect of adding ribavirin (RBV) to the two-drug combination of AZT + ddl. AZT and ddl, used singly or in combination, had no effect on the dNTP pools of CEM lymphoblastoid cells. Neither did the combination of AZT + ddl have any effect on the rNTP pools. RBV, a known inhibitor of IMP dehydrogenase, caused a decrease in GTP and an increase in dTTP whether incubated alone or with the drug combination of AZT + ddl. The addition of AZT + ddl therefore did not alter the effects of RBV upon cellular nucleotide pools. AZT was phosphorylated to a much greater extent than ddl. The activation of ddl to ddA-TP was increased 2-fold in the presence of AZT, whereas AZT phosphorylation was unchanged when combined with ddl. This increase in ddl activation may explain in part the synergistic antiviral activity of the combination of AZT + ddl. The increased activation was not due to increased phosphorylation of ddl resulting from IMP dehydrogenase inhibition. The addition of 10 μm RBV to the two-drug combination of AZT + ddl did not change the intracellular phosphorylation of AZT or ddl. The activation of ddl to ddA-TP, when combined with AZT, appeared to be maximal and could not be further increased by addition of RBV to this combination.
A Comparative Study of the in vitro and in vivo Antiviral Activities of Acyclovir and Penciclovir
Authors: Ertl P. , Snowden W. , Lowe D. , Miller W. , Collins P. , Littler E.
Published: May 2015

The antiviral properties of the compounds acyclovir (ACV) and penciclovir (PCV) have been compared in a number of in vitro and in vivo assays. In vitro, both compounds had good activity against herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV), although ACV showed statistically significant superiority. In addition, ACV had greater activity against herpes simplex virus type 2 (HSV-2), human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV). We examined the effect of time of addition and removal of ACV and PCV under a variety of conditions and found similar results with the two compounds under most conditions. However, at a high multiplicity of infection, when all of the cells would be expected to be synchronously expressing large amounts of the viral thymidine kinase, short exposures to PCV appeared to be superior to similar exposures to ACV. In the HSV-1 zosteriform mouse model there was no significant difference between the activities of ACV and PCV, or its prodrug famciclovir (FCV), in once- or twice-daily treatment. The possible significance of these results and those previously reported on the activity of the compounds in humans is discussed.
In vitro Inhibitory Effects of Combinations of anti-Influenza Agents
Authors: Madren L. K. , Shipman C. , Hayden F. G.
Published: May 2015

To assess the possible interactions among candidate anti-influenza agents, dual combinations of rimantadine, ribavirin, 2′-deoxy-2′-fluoroguanosine (2-FDG) and 4-guanidino-Neu5Ac2en (GG167) were tested against clinical isolates of influenza A H3N2 and H1N1 subtype viruses in MDCK cells by ELISA. Each of the dual combinations showed additive effects, except for the combination of 2-FDG and ribavirin which was synergistic against the influenza A (H1N1) virus. However, this combination also showed enhanced cytotoxicity. In this assay system, influenza agents with differing mechanisms of antiviral interaction interacted in an additive fashion with respect to inhibition of viral replication.