Expression profiling of non-aflatoxigenic Aspergillus parasiticus mutants obtained by 5-azacytosine treatment or serial mycelial transfer

Aflatoxins are carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Previous studies found that repeated serial mycelial transfer or treatment of A. parasiticus with 5-azacytidine produced colonies with a fluffy phenotype and inability to produce aflatoxins. To understand how these treatments affect expression of genes involved in aflatoxin production and development, we carried out expressed sequence tag (EST)-based microarray assays to identify genes in treated clones that are differentially expressed compared to the wild-type. Expression of 183 genes was significantly dysregulated. Of these, 38 had at least two-fold or lower expression compared to the untreated control and only two had two-fold or higher expression. The most frequent change was downregulation of genes predicted to encode membrane-bound proteins. Based on this result we hypothesize that the treatments cause changes in the structure of cellular and organelle membranes that prevent normal development and aflatoxin biosynthesis.

The presence of 5-hydroxymethylcytosine at the gene promoter and not in the gene body negatively regulates gene expression

5-Hydroxymethylcytosine (5hmC) was recently described as a stable modification in mammalian DNA. 5hmC is formed by the enzymatic oxidation of 5-methylcytosine (5meC). Overwhelming evidence supports the notion that 5meC has a negative effect on transcription; however, only recently has the effect that 5hmC has on transcription begun to be studied. Using model substrates including the CMV(IE) promoter and a generic gene body we have directly assessed the effect that 5hmC, both at the promoter and in the gene body, has on in vitro gene transcription. We show that the presence of the 5hmC modifications strongly represses transcription. We also demonstrate that the inhibition of transcriptional activity is primarily due to the presence of 5hmC in the promoter and that 5hmC in the gene body has a minimal effect on transcription. Thus, we propose that the presence of 5hmC in promoter prevents the binding of essential transcription factors or recruits factors that repress transcription.

Local and systemic effects of intralaryngeal injection of cidofovir in a canine model

OBJECTIVE

The safety of intralaryngeal injection of cidofovir remains a concern. Our goal was to evaluate local and systemic effects of intralaryngeal injection of cidofovir.

STUDY DESIGN

Animal study using a canine model.

METHODS

Two groups of three young beagle dogs (6 vocal folds in each group) were used. Subepithelial vocal fold injections were performed in each group biweekly for 6 months with 0, 2.5, 5, 10, 20, and 37.5 mg cidofovir in a 0.5 mL volume. Direct laryngoscopy was performed at each injection interval. Complete blood cell count and renal parameters were measured at baseline and monthly thereafter. Histopathologic examination of the vocal folds was performed after the 6-month injection period in one group of animals and after an additional 6-month observation period in the second group.

RESULTS

Endomysial edema with muscle fiber separation and dose-dependent atrophy and scarring of the vocal folds was present. Onset of atrophy and scarring was observed after 3, 7, and 11 injections in the vocal folds injected with 37.5, 20, and 10 mg cidofovir, respectively. After the 6-month observation period, recovery of histologic abnormalities was complete in the low-dose (0, 2.5 mg) vocal folds, near complete in the intermediate-dose (5, 10 mg) vocal folds, and no apparent recovery was seen in the high-dose (20, 37.5 mg) vocal folds. Leukocyte count and renal parameters remained unchanged at up to 4.26 mg/kg body weight of systemic dose of cidofovir.

CONCLUSIONS

Intralaryngeal cidofovir leads to dose-dependent scarification of the vocal folds that appears irreversible at higher doses. Lower concentrations of this drug should be used in intralesional intralaryngeal use.

Expansion, reexpansion, and recall-like expansion of Vgamma2Vdelta2 T cells in smallpox vaccination and monkeypox virus infection

Little is known about the in vivo kinetics of T-cell responses in smallpox/monkeypox. We showed that macaque Vgamma2Vdelta2 T cells underwent 3-week-long expansion after smallpox vaccine immunization and displayed simple reexpansion in association with sterile anti-monkeypox virus (anti-MPV) immunity after MPV challenge. Virus-activated Vgamma2Vdelta2 T cells exhibited gamma interferon-producing effector function after phosphoantigen stimulation. Surprisingly, like alphabeta T cells, suboptimally primed Vgamma2Vdelta2 T cells in vaccinia virus/cidofovir-covaccinated macaques mounted major recall-like expansion after MPV challenge. Finally, Vgamma2Vdelta2 T cells localized in inflamed lung tissues for potential regulation. Our studies provide the first in vivo evidence that viruses, despite their inability to produce exogenous phosphoantigen, can induce expansion, reexpansion, and recall-like expansion of Vgamma2Vdelta2 T cells and stimulate their antimicrobial cytokine response.

Dideoxy fluoro-ketopyranosyl nucleosides as potent antiviral agents: synthesis and biological evaluation of 2,3- and 3,4-dideoxy-3-fluoro-4- and -2-keto-beta-d-glucopyranosyl derivatives of N(4)-benzoyl cytosine

The synthesis of the dideoxy fluoro ketopyranonucleoside analogues, 1-(2,3-dideoxy-3-fluoro-6-O-trityl-beta-d-glycero-hexopyranosyl-4-ulose)-N(4)-benzoyl cytosine (7a), 1-(3,4-dideoxy-3-fluoro-6-O-trityl-beta-d-glycero-hexopyranosyl-2-ulose)-N(4)-benzoyl cytosine (13a) and their detritylated analogues 8a and 14a, respectively, is described. Condensation of peracetylated 3-deoxy-3-fluoro-D-glucopyranose (1) with silylated N(4)-benzoyl cytosine, followed by selective deprotection and isopropylidenation afforded compound 2. Routine deoxygenation at position 2', followed by a deprotection-selective reprotection sequence afforded the partially tritylated dideoxy nucleoside of cytosine 6, which upon oxidation of the free hydroxyl group at the 4'-position, furnished the desired tritylated 2,3-dideoxy-3-fluoro ketonucleoside 7a in equilibrium with its hydrated form 7b. Compound 2 was the starting material for the synthesis of the dideoxy fluoro ketopyranonucleoside 13a. Similarly, several subsequent protection and deprotection steps as well as routine deoxygenation at position 4', followed by oxidation of the free hydroxyl group at the 2'-position of the partially tritylated dideoxy nucleoside 12, yielded the desired carbonyl compound 13a in equilibrium with its hydrated form 13b. Finally, trityl removal from 7a/b and 13a/b provided the unprotected 2,3-dideoxy-3-fluoro-4-keto and 3,4-dideoxy-3-fluoro-2-ketopyranonucleoside analogues 8a and 14a, in equilibrium with their gem-diol forms 8b and 14b. None of the compounds showed inhibitory activity against a wide variety of DNA and RNA viruses at subtoxic concentrations, except 7a/b that was highly efficient against rotavirus infection. Nucleoside 7a/b also exhibited cytostatic activity against cells of various cancers. BrdU-cell cycle analysis revealed that the mechanism of cytostatic activity may be related to a delay in G1/S phase and initiation of programmed cell death.

Novel anti-metastatic action of cidofovir mediated by inhibition of E6/E7, CXCR4 and Rho/ROCK signaling in HPV tumor cells

Cervical cancer is frequently associated with HPV infection. The expression of E6 and E7 HPV oncoproteins is a key factor in its carcinogenicity and might also influence its virulence, including metastatic conversion. The cellular mechanisms involved in metastatic spread remain elusive, but pro-adhesive receptors and their ligands, such as SDF-1α and CXCR4 are implicated. In the present study, we assessed the possible relationship between SDF-1α/CXCR4 signaling, E6/E7 status and the metastatic process. We found that SDF-1α stimulated the invasion of E6/E7-positive cancer cell lines (HeLa and TC-1) in Matrigel though CXCR4 and subsequent Rho/ROCK activation. In pulmonary metastatic foci generated by TC-1 cells IV injection a high proportion of cells expressed membrane-associated CXCR4. In both cases models (in vitro and in vivo) cell adhesion and invasion was abrogated by CXCR4 immunological blockade supporting a contribution of SDF-1α/CXCR4 to the metastatic process. E6 and E7 silencing using stable knock-down and the approved anti-viral agent, Cidofovir decreased CXCR4 gene expression as well as both, constitutive and SDF-1α-induced cell invasion. In addition, Cidofovir inhibited lung metastasis (both adhesion and invasion) supporting contribution of E6 and E7 oncoproteins to the metastatic process. Finally, potential signals activated downstream SDF-1α/CXCR4 and involved in lung homing of E6/E7-expressing tumor cells were investigated. The contribution of the Rho/ROCK pathway was suggested by the inhibitory effect triggered by Cidofovir and further confirmed using Y-27632 (a small molecule ROCK inhibitor). These data suggest a novel and highly translatable therapeutic approach to cervix cancer, by inhibition of adhesion and invasion of circulating HPV-positive tumor cells, using Cidofovir and/or ROCK inhibition.

Differential susceptibility of adenovirus clinical isolates to cidofovir and ribavirin is not related to species alone

BACKGROUND

We have previously reported that human adenovirus (HAdV) reference strains clearly show species-dependent resistance to ribavirin, whereas different species of HAdV are equally sensitive to cidofovir. All the serotypes tested were susceptible to cidofovir, whereas only serotypes from species C were sensitive to ribavirin. Here, we aimed to extend these investigations to clinical isolates.

METHODS

In vitro, we tested 126 isolates obtained from 65 patients included in a European survey of HAdV infection.

RESULTS

Among the 126 isolates tested, all presented cidofovir 50% inhibitory concentration (IC50) in the same range as the HAdV 5 reference strain. Regarding ribavirin, all isolates from species C (79 tested) showed an IC50 comparable with previously reported results for reference strains; however, 24/32, 2/6 and 3/3 tested isolates from species A, B and D, respectively, were shown to have a ribavirin IC50 comparable with the HAdV 5 reference strain (species C), contrary to previous observations for reference strains of the same species. Among patients who were treated with cidofovir for disseminated HAdV infection, > or = 4 sequential isolates could be obtained from 9 patients; no variation in cidofovir susceptibility could be detected.

CONCLUSIONS

Cidofovir is active in vitro in all HAdV clinical isolates. Ribavirin was revealed to be active on most HAdV isolates from species A, B and D, and in all isolates from species C. Finally, no resistance to cidofovir became apparent in sequential isolates obtained from treated patients.

Antiviral activity of cidofovir against telomerase-specific replication-selective oncolytic adenovirus, OBP-301 (Telomelysin)

We constructed a replication-competent oncolytic adenovirus, OBP-301 (Telomelysin), in which human telomerase reverse transcriptase (hTERT) promoter drives E1 genes. OBP-301 is currently being used in a phase-I clinical trial for various types of tumors. Under such conditions, anti-adenoviral agents should be available for safety use against OBP-301 since any adenoviral viremia could cause severe adverse effects. Cidofovir (CDV) is an acyclic nucleoside phosphonate that has a broad antiviral activity against DNA viruses. Here, we examined the antiviral effects of CDV against OBP-301. The in vitro cytopathic effects of OBP-301 were suppressed by CDV. Moreover, CDV decreased the adenoviral E1A gene copy number after OBP-301 infection. These results suggest that CDV is a potentially useful antiviral agent for OBP-301.

Virological pattern in plasma, peripheral blood mononuclear cells and liver tissue and clinical outcome in chronic hepatitis B and C virus coinfection

BACKGROUND

We aim to evaluate in chronic hepatitis B virus-hepatitis C virus (HBV-HCV) coinfection the interplay of these viruses in liver tissue, peripheral blood mononuclear cells (PBMC), and plasma and to analyze the effect on disease course and response to treatment.

METHODS

We enrolled 19 patients with chronic HBV-HCV coinfection, 20 with chronic HCV and 20 with chronic HBV infection at their first liver biopsy, all were naive for antiviral therapy. The patients' plasma, PBMC and liver biopsy samples were tested for HBV DNA and/or HCV RNA by real-time PCR, according to the presence/absence of hepatitis B surface antigen and antibodies against HCV in the serum.

RESULTS

Contemporary presence of HBV DNA and HCV RNA was rare in plasma (5.3% of cases) and PBMC (10.6%), but frequent in liver tissue (52.6%). Of 10 cases circulating only HCV RNA and treated with pegylated interferon (PEG-IFN) plus ribavirin for 12 months, two showed a sustained response, and eight cleared HCV RNA but became HBV-DNA-positive in plasma; these eight had detectable HBV DNA in liver at baseline. One patient, who was plasma HBV-DNA-positive/HCV-RNA-negative at baseline, showed a sustained response after 18 months of PEG-IFN treatment; another, who was plasma HBV-DNA/HCV-RNA-positive at baseline, cleared only HCV RNA during 12 months of PEG-IFN plus ribavirin treatment. Seven cases remained untreated.

CONCLUSION

Despite a reciprocal inhibition in plasma, HBV and HCV frequently coexist in liver tissue, a condition to be taken into consideration when deciding therapy.

Unsaturated fluoro-ketopyranosyl nucleosides: Synthesis and biological evaluation of 3-fluoro-4-keto-β-d-glucopyranosyl derivatives of N4-benzoyl cytosine and N6-benzoyl adenine

The protected beta-nucleosides 1-(2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-beta-d-glucopyranosyl)-N(4)-benzoyl cytosine (2a) and 9-(2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-beta-d-glucopyranosyl)-N(6)-benzoyl adenine (2b), were synthesized by the coupling of peracetylated 3-deoxy-3-fluoro-d-glucopyranose (1) with silylated N(4)-benzoyl cytosine and N(6)-benzoyl adenine, respectively. The nucleosides were deacetylated and several subsequent protection and deprotection steps afforded the partially acetylated nucleosides of cytosine 7a and adenine 7b, respectively. Finally, direct oxidation of the free hydroxyl group at 4'-position of 7a and 7b, and simultaneous elimination reaction of the beta-acetoxyl group, afforded the desired unsaturated 3-fluoro-4-keto-beta-d-glucopyranosyl derivatives. These newly synthesized compounds were evaluated for their potential antitumor and antiviral activities. Compared to 5FU, the newly synthesized derivatives showed to be more efficient as antitumor growth inhibitors and they exhibited direct antiviral effect toward rotavirus.

Clinical application of CpG-, non-CpG-, and antisense oligodeoxynucleotides as immunomodulators

Cytosine-phosphate-guanosine (CpG) motifs, found mainly in bacterial DNA, have immunostimulatory effects in humans and have offered new perspectives in the treatment of clinical conditions, including viral and bacterial infections, vaccination, allergy and asthma, and in antitumor therapy. Three classes of CpG-oligodeoxynucleotides (ODNs), CpG-A, -B, and -C, with distinct biological properties and which differ in their sequence and nucleotide backbone, have been characterized. Typically, CpG-ODNs bind to TLR9 in the endosomal compartment and initiate a signaling cascade that leads to activation of proinflammatory transcription factors such as NFkappaB. In addition, non-CpG-ODNs have been shown to modulate the immune system and, although these molecules are devoid of CpG motifs, their biological action appears to require a functional TLR9. In this review, advances in the clinical therapy and prevention of infectious diseases using ODNs, as well as the use of antisense ODNs that specifically target genes and control exaggerated immune responses, are discussed. In addition, an update of selected ODNs that have entered clinical trials is provided.

[In vitro acyclovir and cidofovir susceptibilities of human herpesvirus type 1 clinical isolates]

Infections with human herpesviruses types 1 and 2 (HHV-1 and HHV-2) are common worldwide and cause a wide range of signs and symptoms. Antiviral drugs, in particular aciclovir are used in therapy of herpetic infections. The aim of the study was determination of susceptibilities of HHV-1 isolates (n+46) for antiviral drugs (acyclovir and cidofovir) in vitro. Swabs taken from different lesions were used for infection of Vero cells and cythopathic effect was observed. Viruses from cell cultures with positive CPE were later identified with in-house PCR and efficacy of acyclovir and cidofovir in HHV-1 infected Vero cell monolayer cultures was tested by the yield reduction assay. Obtained data indicate, that aciclovir ID50 average value for HHV-1 clinical isolates was 0.74 microg/ml--the value about 10% greater then described in literature. Similarly in vitro analysis of sensitivity of viruses for cidofovir, shows that concentrating is over ten-fold higher in comparison for aciclovir.

Effects of cidofovir on a novel cell-based test system for recurrent respiratory papillomatosis

BACKGROUND

Cidofovir has been reported to have activity against human papillomavirus (HPV) type 16, but no laboratory studies have been performed on HPV type 6, the main cause of recurrent respiratory papillomatosis (RRP).

METHODS

HPV6b E6 cDNA-based C33A (non-HPV cervical carcinoma) cell line was produced. Two different doses of cidofovir were applied to parent C33A, C33AT6E6, and C33AT16E6 (HPV 16). Growth and flow cytometry analysis were performed.

RESULTS

Polymerase chain reaction confirmed HPV6 E6 expression in C33AT6E6 cells. High-dose cidofovir was found to be toxic to all cell lines. Low-dose exposure was found to be toxic to C33AT16E6 cells at 3 days, whereas C33A and C33AT6E6 showed minimal toxicity at 6 days and earlier recovery following drug withdrawal.

CONCLUSIONS

Cidofovir showed nonspecific toxicity against all 3 cell lines tested. HPV16 E6 expressing cells were more sensitive than parent or HPV6 E6 expressing cells. Cidofovir has no selective advantage for the RRP-related HPV6 E6 expressing cell line.

Atypical cytostatic mechanism of N-1-sulfonylcytosine derivatives determined by in vitro screening and computational analysis

We have previously shown that N-1-sulfonylpyrimidine derivatives have strong antiproliferative activity on human tumor cell lines, whereby 1-(p-toluenesulfonyl)cytosine showed good selectivity with regard to normal cells and was easily synthesized on a large scale. In the present work we have used an interdisciplinary approach to elucidate the compounds' mechanistic class. An augmented number of cell lines (11) has allowed a computational search for compounds with similar activity profiles and/or mechanistic class by integrating our data with the comprehensive DTP-NCI database. We applied supervised machine learning methodology (Random Forest classifier), which offers information complementary to unsupervised algorithms commonly used for analysis of cytostatic activity profiles, such as self-organizing maps. The computational results taken together with cell cycle perturbation and apoptosis analysis of the cell lines point to an unusual mechanism of cytostatic action, possibly a combination of nucleic acid antimetabolite activity and a novel molecular mechanism.

Activities of several classes of acyclic nucleoside phosphonates against camelpox virus replication in different cell culture models

Camelpox virus (CMLV) is the closest known virus to variola virus. Here we report on the anti-CMLV activities of several acyclic nucleoside phosphonates (ANPs) related to cidofovir [(S)-1-(3-hydroxy-2-phosphonomethoxypropyl)cytosine (HPMPC; Vistide)] against two CMLV strains, CML1 and CML14. Cytopathic effect (CPE) reduction assays performed with human embryonic lung fibroblast monolayers revealed the selectivities of the first two classes of ANPs (cHPMPA, HPMPDAP, and HPMPO-DAPy) and of the hexadecyloxyethyl ester of 1-{[(5S)-2-hydroxy-2-oxido-1,4,2-dioxaphosphinan-5-yl]methyl}-5-azacytosine (HDE-cHPMP-5-azaC), belonging to the newly synthesized ANPs, which are HPMP derivatives containing a 5-azacytosine moiety. The inhibitory activities of ANPs against both strains were also confirmed with primary human keratinocyte (PHK) monolayers, despite the higher toxicity of those molecules on growing PHKs. Virus yield assays confirmed the anti-CML1 and anti-CML14 efficacies of the compounds selected for the highest potencies in CPE reduction experiments. Ex vivo studies were performed with a 3-dimensional model of human skin, i.e., organotypic epithelial raft cultures of PHKs. It was ascertained by histological evaluation, as well as by virus yield assays, that CMLV replicated in the human skin equivalent. HPMPC and the newly synthesized ANPs proved to be effective at protecting the epithelial cells against CMLV-induced CPE. Moreover, in contrast to the toxicity on PHK monolayers, signs of toxicity in the differentiated epithelium were seen only at high ANP concentrations. Our results demonstrate that compounds belonging to the newly synthesized ANPs, in addition to cidofovir, represent promising candidates for the treatment of poxvirus infections.

Synergistic efficacy of the combination of ST-246 with CMX001 against orthopoxviruses

The combination of ST-246 and hexadecyloxypropyl-cidofovir or CMX001 was evaluated for synergistic activity in vitro against vaccinia virus and cowpox virus (CV) and in vivo against CV. In cell culture the combination was highly synergistic against both viruses, and the results suggested that combined treatment with these agents might offer superior efficacy in vivo. For animal models, ST-246 was administered orally with or without CMX001 to mice lethally infected with CV. Treatments began 1, 3, or 6 days postinfection using lower dosages than previously used for single-drug treatment. ST-246 was given at 10, 3, or 1 mg/kg of body weight with or without CMX001 at 3, 1, or 0.3 mg/kg to evaluate potential synergistic interactions. Treatment beginning 6 days post-viral inoculation with ST-246 alone only increased the mean day to death at 10 or 3 mg/kg but had no effect on survival. CMX001 alone also had no effect on survival. When the combination of the two drugs was begun 6 days after viral infection using various dosages of the two, a synergistic reduction in mortality was observed. No evidence of increased toxicity was noted with the combination either in vitro or in vivo. These results indicate that combinations of ST-246 and CMX001 are synergistic both in vitro and in vivo and suggest that combination therapy using ST-246 and CMX001 for treatment of orthopoxvirus disease in humans or animals may provide an additional benefit over the use of the two drugs by themselves.

Antiproliferative effects of sapacitabine (CYC682), a novel 2'-deoxycytidine-derivative, in human cancer cells

This study assessed the antiproliferative activity of sapacitabine (CYC682, CS-682) in a panel of 10 human cancer cell lines with varying degrees of resistance or sensitivity to the commonly used nucleoside analogues ara-C and gemcitabine. Growth inhibition studies using sapacitabine and CNDAC were performed in the panel of cell lines and compared with both nucleoside analogues and other anticancer compounds including oxaliplatin, doxorubicin, docetaxel and seliciclib. Sapacitabine displayed antiproliferative activity across a range of concentrations in a variety of cell lines, including those shown to be resistant to several anticancer drugs. Sapacitabine is biotransformed by plasma, gut and liver amidases into CNDAC and causes cell cycle arrest predominantly in the G(2)/M phase. No clear correlation was observed between sensitivity to sapacitabine and the expression of critical factors involved in resistance to nucleoside analogues such as deoxycytidine kinase (dCK), human equilibrative nucleoside transporter 1, cytosolic 5'-nucleotidase and DNA polymerase-alpha. However, sapacitabine showed cytotoxic activity against dCK-deficient L1210 cells indicating that in some cells, a dCK-independent mechanism of action may be involved. In addition, sapacitabine showed a synergistic effect when combined with gemcitabine and sequence-specific synergy with doxorubicin and oxaliplatin. Sapacitabine is therefore a good candidate for further evaluation in combination with currently used anticancer agents in tumour types with unmet needs.

In vivo imaging of cidofovir treatment of cowpox virus infection

Variola virus and other members of the genus Orthopoxviruses constitute a prominent bioterrorism and public health threat. Treatment with the anti-viral drug cidofovir inhibits replication of orthopoxviruses in vitro and in vivo. In this study, we visualized the effect of cidofovir on viral kinetics in orthopoxvirus infected mice by using whole-body fluorescence imaging (FI). We engineered a cowpox virus (CPV) expressing the enhanced green fluorescent protein (GFP). Single-step growth curves and calculated 50% lethal doses (LD(50)) of wild-type CPX (Wt-CPV) and GFP-expressing CPX (GFP-CPV) were comparable. Whole-body FI first detected GFP fluorescence in the mesenteric tissue of untreated animals on post-infection day (PID) 1. On PID 3 GFP signal was detected throughout the mesentery, in all abdominal organs by PID 5 and in most major organs, except for the heart and brain by PID 6. Infected animals treated with 25mg/kg of cidofovir also began showing signs of viral replication on PID 1, however, the fluorescent signal was limited only to discrete foci throughout the course of the infection. This work describes the first use of an established Orthopox model of infection to evaluate drug efficacy and track virus progression on a macroscopic level.

In vitro susceptibility of six isolates of equine herpesvirus 1 to acyclovir, ganciclovir, cidofovir, adefovir, PMEDAP and foscarnet

Equine herpesvirus 1 (EHV-1) is an important equine pathogen that causes respiratory disease, abortion, neonatal death and paralysis. Although vaccines are available, they are not fully protective and outbreaks of disease may occur in vaccinated herds. Therefore, there is an urgent need for effective antiviral treatment. For three abortigenic (94P247, 97P70 and 99P96) and three neuropathogenic isolates (97P82, 99P136 and 03P37), the effect of acyclovir, ganciclovir, cidofovir, adefovir, 9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine (PMEDAP) and foscarnet on plaque number was studied. Additionally, for isolate 97P70, the effect on plaque size was investigated. Ganciclovir was most potent in reducing plaque number, followed by PMEDAP and acyclovir. Adefovir and cidofovir were less effective and foscarnet was the least effective compound. There were no differences detected for acyclovir, ganciclovir, adefovir and PMEDAP between the abortigenic and neuropathogenic isolates. One abortigenic isolate (99P96) was more susceptible to cidofovir and two neuropathogenic isolates (99P136 and 03P37) were less susceptible to foscarnet. For isolate 97P70, all compounds resulted in a significant reduction of plaque size. The most remarkable effect was observed for cidofovir. It was 40-fold more effective in reducing plaque size than in reducing plaque number. In conclusion, ganciclovir was the most potent compound and therefore, may be a valuable candidate for the treatment of EHV-1 infections in horses. The antiviral effect of foscarnet on plaque number was highly dependent on the viral isolate tested. Therefore, it is no valuable antiviral for the treatment of herpesvirus-infections. Cidofovir, although less effective in reducing plaque number, had a strong effect on plaque size.

In Vitro Optimization of Non-Small Cell Lung Cancer Activity with Troxacitabine,l-1,3-Dioxolane-cytidine, Prodrugs

l-1,3-Dioxolane-cytidine, a potent anticancer agent against leukemia, has limited efficacy against solid tumors, perhaps due to its hydrophilicity. Herein, a library of prodrugs were synthesized to optimize in vitro antitumor activity against non-small cell lung cancer. N4-Substituted fatty acid amide prodrugs of 10-16 carbon chain length demonstrated significantly improved antitumor activity over l-1,3-dioxolane-cytidine. These in vitro results suggest that the in vivo therapeutic efficacy of l-1,3-dioxolane-cytidine against solid tumors may be improved with prodrug strategies.

Inhibitory activities of three classes of acyclic nucleoside phosphonates against murine polyomavirus and primate simian virus 40 strains

Murine polyomavirus and simian virus 40 were used to evaluate the potencies of the compounds of three classes of acyclic nucleoside phosphonates: (i) the original HPMP (3-hydroxy-2-phosphonomethoxypropyl) and PME (2-phosphonomethoxyethyl) derivatives, (ii) the 6-[2-(phosphonomethoxy)alkoxy]-2,4-diaminopyrimidine (DAPy) derivatives, and (iii) a new class of HPMP derivatives containing a 5-azacytosine moiety. The last class showed the highest activities and selectivities against both polyomaviruses.

Acyclic nucleoside phosphonates: Past, present and future

Twenty years following the description of the broad-spectrum antiviral activity of S-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine [(S)-HPMPA] [De Clercq E, Holý A, Rosenberg I, Sakuma T, Balzarini J, Maudgal PC. A novel selective broad-spectrum anti-DNA virus agent. Nature 1986;323:464-7], the acyclic nucleoside phosphonates have acquired a prominent therapeutic position: (i) cidofovir in the treatment of papilloma-, herpes-, adeno- and poxvirus infections, (ii) adefovir in the treatment of chronic hepatitis B virus (HBV) infections, and (iii) tenofovir in the treatment of human immunodeficiency virus (HIV) infections (AIDS). Although formally approved only for the treatment of human cytomegalovirus (HCMV) retinitis in AIDS patients, cidofovir has been used successfully in the treatment of various other DNA virus infections, particularly human papilloma virus (HPV)-associated lesions. Adefovir dipivoxil has become a standard therapy for HBV infections, especially when resistant to lamivudine. Tenofovir disoproxil fumarate (TDF) is the corner stone of the triple-drug (TDF, emtricitabine, and efavirenz) combination therapy for AIDS, and TDF, alone or combined with emtricitabine may in the future evolve to the standard therapy of hepatitis B. Guided by the results obtained with tenofovir in the prevention of parenteral, intravaginal and perinatal infections with simian immunodeficiency virus in monkeys, and the safety profile gathered with TDF in humans with AIDS over the past 5 years since TDF was licensed for clinical use, it should be further pursued for the pre- and post-exposure prophylaxis of HIV infections in humans. Meanwhile, new classes of both acyclic (i.e. PMPO-DAPy, PMEO-DAPy, HPMPO-DAPy) and cyclic nucleoside phosphonates (i.e. PMDTA, PMDTT, GS9148) have been accredited with an antiviral potency and selectivity similar to those of cidofovir, adefovir and/or tenofovir.