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Aim: To determine the relationship between host immunity and the characteristics of viral infection or nucleoside analogues (NAs) themselves in patients with chronic hepatitis B (CHB) receiving NA therapy., Methods: Fifty-two hepatitis B envelope antigen (HBeAg) positive CHB patients were enrolled and divided equally into two groups. One group received telbivudine (LDT, 600 mg/d), and the other group received lamivudine (LAM, 100 mg/d). Clinical, virological and immunological parameters were assessed at the baseline and at 4, 12, 24, 36 and 48 wk., Results: Both groups achieved significant hepatitis B virus (HBV) replication inhibition and alanine aminotransferase normalization at 48 wk. At the baseline, compared to healthy controls, CHB patients had a lower circulating CD8 T cell frequency (29.44% ± 11.55% vs 37.17% ± 7.30%, P = 0.03) and higher frequencies of programmed death 1 positive CD8 T cells (PD-1+ CD8 T) (16.48% ± 10.82% vs 7.02% ± 3.62%, P = 0.0001) and CD4+ CD25+ FoxP3+ T regulatory cells (Tregs) (23.64% ± 9.38% vs 13.60% ± 6.06%, P = 0.001). On therapy, at the beginning 24 wk with the levels of hepatitis B virus deoxyribonucleic acid (HBV DNA) and HBeAg declining, the frequencies of PD-1+ CD8 T cells and Treg cells gradually and significantly declined at 12 and 24 wk in both therapy groups. At treatment week 4, patients treated with LDT had a lower frequency of PD-1+ CD8 T cells compared to patients treated with LAM (10.08% ± 6.83% vs 20.51% ± 20.96%, P = 0.02). The frequency of PD-1+ CD8 T cells in all of the CHB patients was significantly correlated with both the HBV DNA level (r = 0.45, P = 0.01) and HBeAg level (r = 0.47, P = 0.01) at treatment week 24, but the frequency of Treg cells was only significantly correlated with the HBeAg level (r = 0.44,P = 0.02). Furthermore, the ability of CD8 T cells to secrete pro-inflammatory cytokines was partially restored after 24 wk of therapy., Conclusion: NA-mediated HBV suppression could down-regulate the production of negative regulators of host immunity during the first 24 wk of therapy and could partially restore the ability of CD8 T cells to secrete pro-inflammatory cytokines. This immune modulating response may be correlated with the levels of both HBV DNA and HBeAg.

The majority of fluorescent nucleoside analogues used in nucleic acid studies have excitation maxima in the UV region and show very low fluorescence within oligonucleotides (ONs); hence, they cannot be utilised with certain fluorescence methods and for cell-based analysis. Here, we describe the synthesis, photophysical properties and incorporation of a highly emissive and environment-sensitive uridine analogue, derived by attaching a Lucifer chromophore (1,8-naphthalimide core) at the 5-position of uracil. The emissive nucleoside displays excitation and emission maxima in the visible region and exhibits high quantum yield. Importantly, when incorporated into ON duplexes it retains appreciable fluorescence efficiency and is sensitive to the neighbouring base environment. Notably, the nucleoside signals the presence of purine repeats in ON duplexes with an enhancement in fluorescence intensity, a property rarely displayed by other nucleoside analogues., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This review article considers 2'-labelled and 3'-labelled nucleosides, which are of great importance as positron emission tomography (PET) probes in clinical diagnostics and PET research. Although the radiochemical preparation of several [(18)F]-labelled nucleosides such as [(18)F]fluorothymidine or [(18)F](fluoroarabinofuranosyl)cytosine has been accomplished within the last two decades, a number of potentially interesting nucleoside-based biomarkers are not yet available for automated good manufacturing practice production due to the lack of fast and efficient synthetic methods for late-stage [(18)F]-introduction. In order to meet recent demands for new PET-based biomarkers in various clinical applications, appropriate precursors that can easily be fluorinated and deprotected need to be developed., (Copyright © 2014 John Wiley & Sons, Ltd.)

The flavin-dependent thymidylate synthase X (ThyX), rare in eukaryotes and completely absent in humans, is crucial in the metabolism of thymidine (a DNA precursor) in many microorganisms including several human pathogens. Conserved in mycobacteria, including Mycobacterium leprae, and Mycobacterium tuberculosis, it represents a prospective anti-mycobacterial therapeutic target. In a M. tuberculosis ThyX-enzyme inhibition assay, N-(3-(5-(2'-deoxyuridine-5'-phosphate))prop-2-ynyl)octanamide was reported to be the most potent and selective 5-substituted 2'-deoxyuridine monophosphate analogue. In this study, we masked the two charges at the phosphate moiety of this compound using our ProTide technology in order to increase its lipophilicity and then allow permeation through the complex mycobacterial cell wall. A series of N-(3-(5-(2'-deoxyuridine))prop-2-ynyl)octanamide phosphoroamidates were chemically synthesized and their biological activity as potential anti-tuberculars was evaluated. In addition to mycobacteria, several DNA viruses depend on ThyX for their DNA biosynthesis, thus these prodrugs were also screened for their antiviral properties., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Protease inhibitor (PI) monotherapy for treatment could avoid the adverse events, drug resistance, and additional costs associated with other antiretrovirals that are normally used, particularly the nucleoside analogues. PI monotherapy has mainly been compared with standard triple therapy in randomized clinical trials of patients who have HIV RNA suppression at screening and no history of virological failure., Methods: This review included 11 randomized clinical trials of darunavir/ritonavir (DRV/r) or lopinavir/ritonavir (LPV/r) monotherapy versus triple therapy in 1,267 patients with HIV RNA suppression at baseline who were studied between 48 and 144 weeks., Results: There was no clear difference in the risk of central nervous system (CNS) adverse events between PI monotherapy (either DRV/r or LPV/r) and standard triple drug treatment. There were 2 clinical trials - MONOI (DRV/r) and MOST (LPV/r) - that showed CNS symptoms and detectable HIV RNA levels in the cerebrospinal fluid in a small number of individuals taking PI monotherapy., Conclusions: There was no consistent evidence from the randomized trials currently available for an additional risk of HIV CNS disease during monotherapy with either LPV/r or DRV/r versus standard triple drug therapy. However, the information on CNS adverse events has not been reported using standardized definitions in the studies. In addition, few randomized studies included detailed analysis of neurocognitive function or detection of HIV RNA in the cerebrospinal fluid.

Novel C6-piperazine substituted purine nucleoside analogues (2-9) bearing a modified pyranose-like D ring of the 4-azasteroid moiety were efficiently synthesized through nucleophilic substitution at C6 position of the steroid-nucleoside precursors (1) with versatile piperazines. All newly-synthesized compounds were evaluated for their anticancer activity in vitro against Hela, PC-3 and MCF-7 cell lines. Among them, compounds 8b and 9b exhibited significant cytotoxicity on PC-3 cell lines., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Adenine nucleotides are involved in a variety of cellular metabolic processes, including nucleic acid synthesis and repair, formation of coenzymes, energy transfer, cell and ciliary motility, hormone secretion, gene expression regulation and ion-channel control. Adenylate kinases are abundant phosphotransferases that catalyze the interconversion of adenine nucleotides and thus regulate the adenine nucleotide ratios in different intracellular compartments. Nine different adenylate kinase isoenzymes have been identified and characterized so far in human tissues, named AK1 to AK9 according to their order of discovery. Adenylate kinases differ in molecular weight, tissue distribution, subcellular localization, substrate and phosphate donor specificity and kinetic properties. The preferred substrate and phosphate donor of all adenylate kinases are AMP and ATP respectively, but some members of the family can phosphorylate other substrates and use other phosphate donors. In addition to their nucleoside monophosphate kinase activity, adenylate kinases were found to possess nucleoside diphosphate kinase activity as they are able to phosphorylate both ribonucleoside and deoxyribonucleoside diphosphates to their corresponding triphosphates. Nucleoside analogues are structural analogues of natural nucleosides, used in the treatment of cancer and viral infections. They are inactive prodrugs that are dependent on intracellular phosphorylation to their pharmacologically active triphosphate form. Novel data presented in this review confirm the role of adenylate kinases in the activation of deoxyadenosine and deoxycytidine nucleoside analogues., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The standard of care for patients suffering cancer often includes treatment with nucleoside analogues (NAs). NAs are internalized by cell-specific nucleobase/nucleoside transporters and, after enzymatic activation (often one or more phosphorylation steps), interfere with cellular nucleo(s)(t)ide metabolism and DNA/RNA synthesis. Therefore, their efficacy is highly dependent on the expression and activity of nucleo(s)(t)ide-metabolizing enzymes, and alterations thereof (e.g. by down/upregulated expression or mutations) may change the susceptibility to NA-based therapy and/or confer drug resistance. Apart from host cell factors, several other variables including microbial presence may determine the metabolome (i.e. metabolite concentrations) of human tissues. Studying the diversity of microorganisms that are associated with the human body has already provided new insights in several diseases (e.g. diabetes and inflammatory bowel disease) and the metabolic exchange between tissues and their specific microbiota was found to affect the bioavailability and toxicity of certain anticancer drugs, including NAs. Several studies report a preferential colonization of tumor tissues with some mycoplasma species (mostly Mycoplasma hyorhinis). These prokaryotes are also a common source of cell culture contamination and alter the cytostatic activity of some NAs in vitro due to the expression of nucleoside-catabolizing enzymes. Mycoplasma infection may therefore bias experimental work with NAs, and their presence in the tumor microenvironment could be of significance when optimizing nucleoside-based cancer treatment.

Drug resistance and emergence of new pathogens highlight the need for developing new therapeutic agents. We focused on 2-oxonicotinonitrile (2-ONN) as derivative of the natural product 2-pyridinone.(1) Herein, we describe the synthesis of 2-ONNs bearing two aryl groups, which we coupled with organohalides, including three glycosyl bromides, to prepare the nucleoside analogues. Coupling occurred mostly at the 2-ONN ring nitrogen to give the aimed targets, and in a few cases, it happened at the 2-oxo position giving O-alkylation products. Free 2-ONNs and their acetylated nucleosides were tested against a number of viruses. The nucleoside analogue 2a(Ac) showed good anti SARS-CoV and anti influenza A (H₅N₁) activities. Additionally, 7b had good activity against Gram positive bacterium, Bacillis subtilis., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Changes in body fat distribution and bone mass in HIV-infected patients may be associated with long-term use of nucleoside reverse transcriptase inhibitors (NRTIs). The Monarch trial recruited 30 patients receiving non-nucleoside reverse transcriptase inhibitor or protease inhibitor-based highly active antiretroviral therapy, with HIV RNA <40 copies/mL. Patients were randomized to either darunavir/ritonavir 800/100 mg once daily monotherapy or darunavir/ritonavir 800/100 mg once daily + two NRTIs. Bone mass, peripheral lipoatrophy and central fat accumulation were assessed using dual-energy X-ray absorptiometry scanning, supplemented by computed tomography scans. Median age was 43 years, 77% were men. Visceral adipose tissue remained stable from baseline to Week 48 in the whole group (p = 0.261) with no significant difference between arms (p = 0.56). There was a significant reduction in insulin resistance (HOMA-IR, p = 0.013) over 48 weeks in the whole group, but not of body mass index (p = 0.24). In the darunavir/ritonavir monotherapy arm, there was a small but significant increase in both lumbar and femur bone mineral density at 48 weeks and was observed after correction for baseline values. The absolute change in lumbar bone mineral density at 48 weeks was more pronounced in the darunavir/ritonavir arm compared with the darunavir/ritonavir + 2NRTIs arm. In this study, discontinuing nucleoside analogues and switching to darunavir/ritonavir monotherapy was associated with a small but statistically significant increase in bone mineral density, but stable levels of limb fat and visceral adipose tissue.

The ultimate goal of therapy for hepatitis B virus (HBV) infection is to obtain a clinical benefit for the patient by reducing infection-related complications, including hepatocellular carcinoma (HCC). Two main types of antiviral agents have been approved to treat patients in the immune clearance phase: interferon (IFN) and nucleos(t)ide analogues (NAs). NAs are used in most HBeAg-positive chronic hepatitis B patients for several reasons. They are oral drugs that are taken once a day and can be prescribed to all chronic hepatitis B patients, even those with contraindications for IFN. The current first-line NA options, entecavir (ETV) and tenofovir (TDF), have minimal or no risk of long-term resistance, and the sustained virological response is achieved in almost 100% of adherent HBeAg-positive patients. Tolerance is excellent and the safety profile is good, whereas IFN can be associated with adverse events that affect the patients' quality of life. There is considerable evidence to show that NAs modify the natural history of chronic hepatitis B, and increasing evidence that they reduce the risk of developing HCC. The need for long-term, perhaps indefinite treatment in patients who do not achieve anti-HBe seroconversion is the main limitation of NAs, but this is offset by their excellent tolerance and safety profile., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The ultimate goals of treating chronic hepatitis B (CHB) is prevention of hepatocellular carcinoma (HCC) and hepatic decompensation. Since the advent of effective antiviral drugs that appeared during the past two decades, considerable advances have been made not only in controlling hepatitis B virus (HBV) infection, but also in preventing and reducing the incidence of liver cirrhosis and HCC. Furthermore, several recent studies have suggested the possibility of reducing the incidence of recurrent or new HCC in patients even after they have developed HCC. Currently, six medications are available for HBV treatment including, interferon and five nucleoside/nucleotide analogues. In this review, we will examine the antiviral drugs and the progresses that have been made with antiviral treatments in the field of CHB.

Objectives: Tenofovir may be associated with nephrotoxicity. Several studies have shown that an early increase in urinary neutrophil gelatinase-associated lipocalin (NGAL) may predict the occurrence of acute kidney injury. We investigated urine and plasma NGAL in patients on long-term treatment with nevirapine associated with either tenofovir/emtricitabine or abacavir/lamivudine., Patients and Methods: We studied 40 virologically controlled Caucasian patients on stable treatment (median >4 years) with tenofovir/emtricitabine + nevirapine (n = 20) or abacavir/lamivudine + nevirapine (n = 20), and no history of kidney disease, high blood pressure or diabetes. Plasma immunovirological parameters (NGAL and C-reactive protein) and urinary NGAL, β2-microglobulin and α1-microglobulin were measured during a routine clinical visit., Results: Median concentrations of NGAL were in the normal range, but were significantly higher in the abacavir/lamivudine group compared with the tenofovir/emtricitabine group both in the plasma, at 74.9 and 66.0 ng/mL (P = 0.032), respectively, and in the urine, at 36.1 and 12.8 ng/mL (P = 0.017), respectively., Conclusions: Plasma and urinary NGAL concentrations remained in the normal range in this long-term virologically controlld population without any overt renal disease. The usefulness of NGAL in detecting sub-clinical renal dysfunction appears to be very limited.

Objectives: The HIV reverse transcriptase (RT) mutation K65R confers resistance to nucleos(t)ide reverse transcriptase inhibitors (NRTIs). Here, analysing a large database, we report the selection of another rare K65E mutation in patients failing on NRTI-containing regimens., Methods: Clinical and virological characteristics of patients harbouring the K65E mutation were analysed using a large RT sequence database from treatment-experienced individuals. Structural analysis of the K65E RT mutant complex was performed by means of docking simulations. The replication capacity was assessed using viruses harbouring the K65E mutation introduced by site-directed mutagenesis (SDM) in pNL 4-3., Results: Overall, in 23 530 sequences from patients failing on antiretroviral therapy, the prevalence of substitutions at position K65 in RT was 2.4%. In addition to K65R (n = 395) and K65N (n = 9), another mutation, K65E, was found in 15 patients. In 11 out of 15 cases, tenofovir, abacavir, didanosine or stavudine were present at the time of K65E selection. The molecular recognition of RT containing K65E supports evidence for the role of this mutation in resistance to tenofovir. The SDM pNL4-3 K65E variant harboured a very low replicative capacity (5% versus wild-type)., Conclusions: We investigated the role of a novel rare NRTI mutation located at position Lys65 of RT (K65E), found in drug-experienced patients failing on NRTIs. The low frequency of this mutation is probably related to the high impairment of replicative capacity induced by this mutation. This study should have significant clinical implications, as these findings warn clinicians that other minor substitutions at Lys65 (such as K65E) play a role in NRTI resistance.

Hepatocellular carcinoma (HCC) develops in the context of environmental risk factors like chronic viral hepatitis, diabetes and alcohol exposure, often associated to an increased risk of cirrhosis. Antiviral treatments that are effective to counteract hepatitis B and C may also attenuate the risk of tumor development. However, since hepatitis B-related carcinogenesis is promoted independently of the onset of cirrhosis, such antiviral treatments as nucleo(t)side analogs can promote regression of cirrhosis, prevent clinical decompensation and variceal bleeding but not HCC. This means that in successfully treated patients with cirrhosis, HCC is often the consequence of their extended survival. In hepatitis C patients, a sustained virological response to interferon-based therapies can reduce the rate of HCC development, even in patients with cirrhosis who experience histological regression of their liver disease. Future therapies aimed at this endpoint in at risk populations should take into consideration pretreatment patient stratification for host, viral and environmental risk factors. In this context the recent discovery of single nucleotide polymorphisms involved in the immune system function and tumorigenesis, might permit enrollment of populations of patients enriched with HCC risk factors for targeted chemopreventive therapies. This could finally pave the way to personalized algorithms, as already seen in the diagnosis and treatment schemes for chemoprevention.

Background and Aims: We aimed to evaluate the effectiveness of nucleoside analogues such as Lamivudine, Adefovir,Entacavir, and Tenofovir in patients with chronic hepatitis B who failed to respond to interferon therapy and relapsed., Materials and Methods: We followed a total of 73 patients with hepatitis B in the hepatitis outpatient clinic in our hospital. The patients subsequently received nucleoside analogues therapy and their treatment data were evaluated retrospectively. The biochemical and virological response rates were evaluated at 3 and 12 months, and we compared these results with the results of treatment-naive patients., Results: There were 29 (39.7%) HbeAg-positive and 44 (60.3%) HbeAg-negative patients, and their mean age was 35.8 (±13.4) years. Of these patients, 33, 18, 13 and 9 received Entacavir, Tenofovir, Lamivudine, and Adefovir treatment,respectively. In HbeAg-negative patients, at 3 months the biochemical and virological response (early response) rates were observed to be 91% and 98%), and at 12 months the two rates were 93% and 73%, respectively. In HbeAg-positive patients, the biochemical and virological response rates at 3 months were 83% and 97%, and the rates at 12 months were 90% and 48%, respectively., Conclusions: In CHB therapy with treatment-resistent patients, nucleoside analogues may be preferable. There are disadvantages to nucleoside analogues, such as a risk of developing resistance during therapy, reduced HBeAg seroconversion compared to interferons, and the therapy's ambiguous duration. In our study, in HbeAg-negative patients who received nucleoside analogues, a lower biochemical response rate was detected in patients with 1 year of Lamivudine therapy compared to other therapies. For HbeAg-positive patients, the virological response rate was higher in 1 year of Tenofovir therapy than with other therapies.

Cyclization instead of O-phosphorylation is the result of the reaction of the antiviral nucleoside anologue 1 with highly reactive phosphorylating agents. The formation of the novel polycyclic compound 2 shows that 1 has the Z configuration, which is important for the antiviral activity of 1 and related compounds., (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)