Development of a highly sensitive and specific intact proviral DNA assay for HIV-1 subtype B and C

INTRODUCTION

HIV reservoir quantification is essential for evaluation of HIV curative strategies and may provide valuable insights about reservoir dynamics during antiretroviral therapy. The Intact Proviral DNA Assay (IPDA) provides the unique opportunity to quantify the intact and defective reservoir. The current IPDA is optimized for HIV-1 subtype B, the dominant subtype in resource-rich settings. However, subtype C is dominant in Sub-Saharan Africa, jointly accounting for around 60% of the pandemic. We developed an assay capable of quantifying intact and defective proviral HIV-1 DNA of subtype B and C.

METHODS

Primer and probe sequences were strategically positioned at conserved regions in psi and env and adapted to subtype B&C. In silico analysis of 752 subtype B and 697 subtype C near-full length genome sequences (nFGS) was performed to predict  the specificity and sensitivity. Gblocks were used to determine the limit of blank (LoB), limit of detection (LoD), and different annealing temperatures were tested to address impact of sequence variability.

RESULTS

The in silico analysis showed that the HIV-1 B&C IPDA correctly identified 100% of the intact subtype B, and 86% of the subtype C sequences. In contrast, the original IPDA identified 86% and 12% of these subtype B and C sequences as intact. Furthermore, the HIV-1 B&C IPDA correctly identified hypermutated (87% and 88%) and other defective sequences (73% and 66%) for subtype B and C with comparable specificity as the original IPDA for subtype B (59% and 63%). Subtype B cis-acting sequences were more frequently identified as intact by the HIV-1 B&C IPDA compared to the original IPDA (39% and 2%). The LoB for intact proviral DNA copies was 0, and the LoD for intact proviral DNA copies was 6 (> 95% certainty) at 60 °C. Quantification of 2-6 copies can be performed with > 80% certainty. Lowering the annealing temperature to 55 °C slightly lowered the specificity but prevented exclusion of samples with single mutations in the primer/probe region.

CONCLUSIONS

We developed a robust and sensitive assay for the quantification of intact and defective HIV-1 subtype B and C proviral DNA, making this a suitable tool to monitor the impact of (large-scale) curative interventions.

eBooks: A Novel Approach to Education and Training Offering Savings and Resources

eBooks can be an essential tool in bringing in technology-enriched education, just-in-time resources, and enduring material for staff in the health care setting. eBooks provide the most relevant information and can serve as the central hub for links to important documents, such as policies and/or video demonstrations. The use of eBooks will improve training and educational efficiency and can result in cost savings and improvements in standardized clinical practice. [J Contin Educ Nurs. 2023;54(9):394-397.].

Abstract 1758: Discovery of novel potent and selective inhibitors of PRMT5 with anti-tumor activity in hepatocellular carcinoma and lung pre-clinical models

Protein arginine methyltransferase-5 (PRMT5) regulates many essential biological processes by catalyzing the symmetric di-methylation of arginine (sDMA) on a variety of histones and non-histone proteins. PRMT5 activity is dysregulated across many hematological and solid tumor and its overexpression is associated with poor patient prognosis. PRMT5 is also often overexpressed in cancer cells. Genetic and pharmacological inactivation have confirmed the importance of PRMT5 activity to the survival of many cancer cells, including hepatocellular carcinoma (HCC) and non-small cell lung cancer (NSCLC). Thus, inhibiting PRTMT5 activity has emerged as an attractive therapeutic strategy in oncology.

We used structure-based drug design to identify novel small molecule inhibitors of PRMT5. ALG-070005, ALG-070043 and ALG-070017 inhibited PRMT5 enzymatic activity in biochemical assays with half-maximal inhibitory concentrations (IC50s) values between 50-150 pM and showed high selectivity against a panel of six other PRMTs. In HepG2 cells (HCC), ALG-070005, ALG-070043 and ALG-070017 potently decreased sDMA levels and inhibited cell proliferation with IC50 values of 1, 3, and 0.2 nM, respectively. These compounds also exhibited similar antiproliferative activity in A549 NSCLC cells. The three novel PRMT5 inhibitors demonstrated favorable ADME/PK profiles with exposure levels in target organs well above IC50 values, even 24 hours after dosing. When dosed orally in mice, these Aligos compounds inhibited tumor growth in HCC and NSCLC xenograft models, with concomitant inhibition of sDMA in the tumor.

In conclusion, we identified and characterized novel potent and selective inhibitors of PRMT5 with antiproliferative effects in various preclinical models of HCC and lung cancers. These drug candidates also have a broad therapeutic potential in oncology beyond HCC and lung cancer.

Citation Format: Francois Gonzalvez, Koen Vandyck, Yannick Debing, Kusum Gupta, Dinah Misner, Qingling Zhang, Jyanwei Liu, Antitsa Stoycheva, Sarah Stevens, Julian Symons, Leonid Beigelman, Pierre Raboisson, Jerome Deval. Discovery of novel potent and selective inhibitors of PRMT5 with anti-tumor activity in hepatocellular carcinoma and lung pre-clinical models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1758.

MICRODOSIMETRIC MEASUREMENT OF SECONDARY RADIATION IN THE PASSIVE SCATTERED PROTON THERAPY ROOM OF iTHEMBA LABS USING A TISSUE-EQUIVALENT PROPORTIONAL COUNTER

Measurements of the dose equivalent at different distances from the isocenter of the proton therapy center at iThemba LABS were previously performed with a tissue-equivalent proportional counter (TEPC). These measurements showed that the scattered radiation levels were one or two orders of magnitude higher in comparison to other passive scattering delivery systems. In order to reduce these radiation levels, additional shielding was installed shortly after the measurements were done. Therefore, the aim of this work is to quantify and assess the reduction of the secondary doses delivered in the proton therapy room at iThemba LABS after the installation of the additional shielding. This has been performed by measuring microdosimetric spectra with a TEPC at 11 locations around the isocenter when a clinical modulated beam of 200 MeV proton was impinging onto a water phantom placed at the isocenter.

SOI microdosimetry and modified MKM for evaluation of relative biological effectiveness for a passive proton therapy radiation field

With more patients receiving external beam radiation therapy with protons, it becomes increasingly important to refine the clinical understanding of the relative biological effectiveness (RBE) for dose delivered during treatment. Treatment planning systems used in clinics typically implement a constant RBE of 1.1 for proton fields irrespective of their highly heterogeneous linear energy transfer (LET). Quality assurance tools that can measure beam characteristics and quantify or be indicative of biological outcomes become necessary in the transition towards more sophisticated RBE weighted treatment planning and for verification of the Monte Carlo and analytical based models they use. In this study the RBE for the CHO-K1 cell line in a passively delivered clinical proton spread out Bragg peak (SOBP) is determined both in vitro and using a silicon-on-insulator (SOI) microdosimetry method paired with the modified microdosimetric kinetic model. The RBE along the central axis of a SOBP with 2 Gy delivered at the middle of the treatment field was found to vary between 1.11-1.98 and the RBE for 10% cell survival between 1.07-1.58 with a 250 kVp x-ray reference radiation and between 1.19-2.34 and 0.95-1.41, respectively, for a Co60 reference. Good agreement was found between RBE values calculated from the SOI-microdosimetry-MKM approach and in vitro. A strong correlation between proton lineal energy and RBE was observed particularly in the distal end and falloff of the SOBP.

An experimental demonstration of a new type of proton computed tomography using a novel silicon tracking detector

PURPOSE

Radiography and tomography using proton beams promise benefit to image guidance and treatment planning for proton therapy. A novel proton tracking detector is described and experimental demonstrations at a therapy facility are reported. A new type of proton CT reconstructing relative "scattering power" rather than "stopping power" is also demonstrated. Notably, this new type of imaging does not require the measurement of the residual energies of the protons.

METHODS

A large area, silicon microstrip tracker with high spatial and temporal resolution has been developed by the Proton Radiotherapy Verification and Dosimetry Applications consortium and commissioned using beams of protons at iThemba LABS, Medical Radiation Department, South Africa. The tracker comprises twelve planes of silicon developed using technology from high energy physics with each plane having an active area of ∼10 × 10 cm segmented into 2048 microstrips. The tracker is organized into four separate units each containing three detectors at 60° to one another creating an x-u-v coordinate system. Pairs of tracking units are used to reconstruct vertices for protons entering and exiting a phantom containing tissue equivalent inserts. By measuring the position and direction of each proton before and after the phantom, the nonlinear path for each proton through an object can be reconstructed.

RESULTS

Experimental results are reported for tracking the path of protons with initial energies of 125 and 191 MeV. A spherical phantom of 75 mm diameter was imaged by positioning it between the entrance and exit detectors of the tracker. Positions and directions of individual protons were used to create angular distributions and 2D fluence maps of the beam. These results were acquired for 36 equally spaced projections spanning 180°, allowing, for the first time, an experimental CT image based upon the relative scattering power of protons to be reconstructed.

CONCLUSIONS

Successful tracking of protons through a thick target (phantom) has demonstrated that the tracker discussed in this paper can provide the precise directional information needed to perform proton radiography and tomography. When synchronized with a range telescope, this could enable the reconstruction of proton CT images of stopping power. Furthermore, by measuring the deflection of many protons through a phantom, it was demonstrated that it is possible to reconstruct a new kind of CT image (scattering power) based upon this tracking information alone.

Clinical outcome of maraviroc-containing therapy in heavily pre-treated HIV-1-infected patients

Available data on the use of maraviroc (MVC) in clinical settings are limited. In this cohort study, the clinical outcomes of HIV-1-infected patients treated with MVC were analysed and the predictive values of different tropism assays were compared. Baseline viral tropism was assessed and compared by phenotypic (Trofile and MT-2) and genotypic assays. Virological and immunological responses were evaluated. In total, 62 predominantly extensively pre-treated patients started MVC [median GSS 2.0 (IQR 2.0-2.5)]. Tropism assays were performed on baseline samples of 58 patients (93.5%). Thirty-two samples (80.0%) were classified as R5 by Trofile, 41 (80.4%) by genotypic tropism test (GTT) and 17 (81.0%) by MT-2. At least two types of tropism assay were performed on samples from 39 patients, whereas in 15 patients all three assays were performed (concordance 84.8-94.1%). Plasma HIV-RNA was <50 copies/mL in 82.1%, 85.0% and 68.8% of patients after 12, 24 and 36 months, respectively; median CD4 cell increase was 199 (IQR 108-283), 291 (IQR 187-413) and 234 (IQR 106-444)cells/μL. The predictive values of different tropism assays were comparably high: at Month 24, 92.9% (Trofile and GTT) and 100.0% (MT-2) of patients had plasma HIV-RNA <50 copies/mL. Three patients stopped MVC treatment because of suspected side effects. Five patients died during follow-up. In this heavily pre-treated cohort, treatment with MVC was well tolerated and resulted in good immunological and virological responses. Results generated by the different tropism assays correlated well with each other and had a high predictive value.

Uncertainty and anxiety in the cancer of unknown primary patient journey: a multiperspective qualitative study

BACKGROUND

Patients with cancer of unknown primary (CUP) have metastatic malignant disease without an identifiable primary site; it is the fourth most common cause of cancer death.

OBJECTIVES

To explore patients' informal and professional carers' experiences of CUP to inform development of evidence-based, patient-centred care.

METHODS

Qualitative study involving development of multiple exploratory case studies, each comprising a patient and nominated informal and professional carers, with contextual data extracted from medical records.

RESULTS

17 CUP patients, 14 informal and 13 professional carers participated in the study. Two inter-related themes distinct to CUP emerged: uncertainty and continuity of care. In the absence of a primary diagnosis, patients and informal carers experienced uncertainty regarding prognosis, possible recurrence and the primary's hereditary potential. Professional carers experienced difficulty communicating uncertainty to patients, ambiguity in deciding optimal treatment plans in the absence of trial data and a test or treat dilemma: when to discontinue seeking the primary and start treatment. Common problems with care continuity were amplified for CUP patients relating to coordination, accountability and timeliness of care. The remit of multidisciplinary teams (MDTs) often excluded CUP, leading to "MDT tennis" where patients were "bounced" between MDTs.

CONCLUSIONS

The experience of those with CUP is distinctive and it can serve to amplify some of the issues encountered by people with cancer. The clinical uncertainties related to CUP compound existing shortcomings in continuity of care, increasing the likelihood of a disrupted patient journey. However, while little can be done to overcome uncertainty, more could be done to address issues regarding continuity of care.

Patient-led training on patient safety: a pilot study to test the feasibility and acceptability of an educational intervention

BACKGROUND

Training in patient safety is an important element of medical education. Most educational interventions on patient safety training adopt a 'health-professional lens' with limited consideration on the impact of safety lapses on the patient and their families and little or no involvement of patients in the design or delivery of the training.

AIMS

This paper describes a pilot study to test the feasibility and acceptability of implementing a patient-led educational intervention to facilitate safety training amongst newly qualified doctors.

METHOD

Patients and/or carers who had experienced harm during their care shared narratives of their stories with trainees; this was followed by a focused discussion on patient safety issues exploring the causes and consequences of safety incidents and lessons to be learned from these.

RESULTS

The intervention, which will be further tested in an NIHR-funded randomised controlled trial (RCT), was successfully implemented into an existing training programme and found acceptance amongst the patients and trainees.

CONCLUSION

The pilot study proved to be a useful step in refining the intervention for the RCT including identifying appropriate outcome measures and highlighting organisational issues.

Efficacy and safety of an attenuated live QX-like infectious bronchitis virus strain as a vaccine for chickens

The attenuation of infectious bronchitis (IB) QX-like virus strain L1148 is described. The virus was passaged multiple times in embryonated specific pathogen free (SPF) chicken eggs, and at different passage levels samples were tested for safety for the respiratory tract and kidneys in 1-day-old SPF chickens. There was a clear decrease in pathogenicity for the respiratory tract and kidneys when the virus had undergone a large number of passages. Passage level 80 was investigated for safety for the reproductive tract in 1-day-old and 7-day-old SPF chickens. In 1-day-old chickens, 12.5% of the vaccinated birds had macroscopic lesions. No lesions were observed if the chickens had been vaccinated at 7 days of age. Passage level 80 was investigated for its ability to spread from vaccinated to non-vaccinated chickens and for dissemination in the body. The virus was able to spread from vaccinated chickens to groups of non-vaccinated chickens, and in the vaccinated birds the virus was found frequently in oro-pharyngeal and cloacal swabs. A fragment of the hypervariable region of the S1 protein of passage level 80 was sequenced and revealed nucleotide changes resulting in two amino acid substitutions. Passage level 80 was given additional passages to levels 82 and 85. Both passage levels were tested for efficacy in SPF chickens and passage level 85 was tested for efficacy in commercial chickens with maternally derived antibodies (MDA) against a challenge with QX-like strain IB D388. In both SPF chickens and chickens with MDA, the vaccines based on strain IB L1148 were efficacious against challenge.

Midrapidity antiproton-to-proton ratio in pp collisons at sqrt[s]=0.9 and 7 TeV measured by the ALICE experiment

The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at sqrt[s]=0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45<p_{t}<1.05  GeV/c and rapidity |y|<0.5. The ratio is measured to be R_{|y|<0.5}=0.957±0.006(stat)±0.014(syst) at 0.9 TeV and R_{|y|<0.5}=0.991±0.005(stat)±0.014(syst) at 7 TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.

Development of novel therapies for hepatitis C

The current standard of care for the treatment of hepatitis C virus (HCV) infection is a combination of pegylated IFN and ribavirin (Peg-IFN/RBV). Because of the adverse effects associated with both IFN and ribavirin and because Peg-IFN/RBV provides only about a 45-50% sustained virological response (SVR, undetectable HCV RNA for greater than 24 weeks after cessation of therapy) in genotype 1-infected individuals, there is a need for more potent anti-HCV compounds with fewer adverse effects. The twenty-first International Conference on Antiviral Research held in May 2009 in Miami Beach, Florida, featured a special session focused on novel targets for HCV therapy. The session included presentations by world-renowned experts in HCV virology and covered a diverse array of potential targets for the development of new classes of HCV therapies. This review contains concise summaries of discussed topics that included the innate immune response, virus entry, the NS2 protease, the NS3 helicase, NS4B, and NS5A. Each presenter discussed the current knowledge of these targets and provided examples of recent scientific breakthroughs that are enhancing our understanding of these targets. As our understanding of the role of these novel anti-HCV targets increases so will our ability to discover new, more safe and effective anti-HCV therapies.

Modulation of alpha interferon anti-hepatitis C virus activity by ISG15

ISG15 has recently been reported to possess antiviral properties against viruses, both in vivo and in vitro. Knock-down of ISG15 gene expression by small interfering RNA followed by alpha interferon (IFN-α) treatment in Huh-7 cells resulted in an increased phenotypic sensitivity to IFN-α, as determined by measuring hepatitis C virus (HCV) RNA replication inhibition in stably transfected HCV replicon cells and in cells infected with genotype 1a HCVcc (infectious HCV). This IFN-α-specific effect, which was not observed with IFN-γ, correlated with an increase in expression of the IFN-α-inducible genes IFI6, IFITM3, OAS1 and MX1, whereas the expression of the non-IFN-α-inducible genes PTBP-1 and JAK1 remained unchanged. It has previously been reported that, unlike ISG15 knock-down, increased sensitivity to IFN-α after knock-down of USP18 occurs through the prolonged phosphorylation of STAT-1. Combination knock-down of ISG15 and USP18 resulted in a moderate increase in IFN-α-inducible gene expression compared with single ISG15 or USP18 knock-down. Furthermore, the phenotype of increased gene expression after ISG15 knock-down and IFN-α treatment was also observed in non-hepatic cell lines A549 and HeLa. Taken together, these results reveal a novel function for ISG15 in the regulation of the IFN-α pathway and its antiviral effect.

A European multi‐center trial investigating the anti‐restenotic effect of intravascular sonotherapy after stenting of de novo lesions (EUROSPAH: EUROpean Sonotherapy Prevention of Arterial Hyperplasia)

BACKGROUND

Intravascular sonotherapy (IST) reduces neointimal hyperplasia post-stenting in animal studies. Euro-SPAH is a multi-center, double blind, randomized trial investigating the efficacy of IST to reduce in-stent late loss.

METHODS

Patients with angina or silent ischaemia with stented de novo lesions were randomised to sham or IST. The sample size had a 90% power to detect a late loss difference of 0.21 mm at 6 months. The secondary endpoints were MACE at 1, 6, 12 months and neo-intimal hyperplasia on IVUS at 6 months.

RESULTS

At 23 sites in Europe, 403 patients were randomized, with successful treatment with sham or IST in 95.6%. There were no significant differences between the groups in terms of baseline demographics or lesion characteristics. Angiographic follow-up was obtained in 89%. In-stent late loss was not significantly different. The restenosis rate at 6 months was 23% in the IST group versus 25% in the sham group. The IVUS measurements confirm the absence of effect of IST on neointimal hyperplasia. At one year, the event-free survival did not significantly differ between the two groups.

CONCLUSION

The use of sonotherapy following stent implantation in de novo lesions does not reduce intra-stent neointimal hyperplasia, or effect the angiographic restenosis rate compared to sham treatment.

Characterization of the metabolic activation of hepatitis C virus nucleoside inhibitor beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) and identification of a novel active 5'-triphosphate species

beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) is a potent inhibitor of hepatitis C virus (HCV) replication in the subgenomic HCV replicon system, and its corresponding 5'-triphosphate is a potent inhibitor of the HCV RNA polymerase in vitro. In this study the formation of PSI-6130-triphosphate was characterized in primary human hepatocytes. PSI-6130 and its 5'-phosphorylated derivatives were identified, and the intracellular concentrations were determined. In addition, the deaminated derivative of PSI-6130, beta-d-2'-deoxy-2'-fluoro-2'-C-methyluridine (RO2433, PSI-6026) and its corresponding phosphorylated metabolites were identified in human hepatocytes after incubation with PSI-6130. The formation of the 5'-triphosphate (TP) of PSI-6130 (PSI-6130-TP) and RO2433 (RO2433-TP) increased with time and reached steady state levels at 48 h. The formation of both PSI-6130-TP and RO2433-TP demonstrated a linear relationship with the extracellular concentrations of PSI-6130 up to 100 mum, suggesting a high capacity of human hepatocytes to generate the two triphosphates. The mean half-lives of PSI-6130-TP and RO2433-TP were 4.7 and 38 h, respectively. RO2433-TP also inhibited RNA synthesis by the native HCV replicase isolated from HCV replicon cells and the recombinant HCV polymerase NS5B with potencies comparable with those of PSI-6130-TP. Incorporation of RO2433-5'-monophosphate (MP) into nascent RNA by NS5B led to chain termination similar to that of PSI-6130-MP. These results demonstrate that PSI-6130 is metabolized to two pharmacologically active species in primary human hepatocytes.

Design, synthesis, and antiviral properties of 4'-substituted ribonucleosides as inhibitors of hepatitis C virus replication: the discovery of R1479

A series of 4'-substituted ribonucleoside derivatives has been prepared and evaluated for inhibition of hepatitis C virus (HCV) RNA replication in cell culture. The most potent and non-cytotoxic derivative was compound 28 (4'-azidocytidine, R1479) with an IC(50) of 1.28 microM in the HCV replicon system. The triphosphate of compound 28 was prepared and shown to be an inhibitor of RNA synthesis mediated by NS5B (IC(50)=320 nM), the RNA polymerase encoded by HCV. Data on related analogues have been used to generate some preliminary requirements for activity within this series of nucleosides.

Fitness costs limit escape from cytotoxic T lymphocytes by influenza A viruses

The use of cytotoxic T lymphocyte (CTL)-inducing vaccines could afford both homo- and heterosubtypic immunity. However, amino acid variation in CTL epitopes associated with escape from CTL-mediated immunity might undermine the use of these vaccines. To assess the impact of amino acid substitutions in highly conserved epitopes on viral fitness and recognition by specific CTL, we performed a mutational analysis of various CTL epitopes. Our findings indicated that fitness costs limited variation in functionally constrained epitopes, especially at anchor residues.

Biodegradable-polymer-based, paclitaxel-eluting Infinnium stent: 9-Month clinical and angiographic follow-up results from the SIMPLE II prospective multi-centre registry study

BACKGROUND

SIMPLE II was a multi-centre, prospective registry study aimed at investigating the safety and efficacy of the Infinnium (Sahajanand Medical Technologies Pvt. Ltd, India) paclitaxel-eluting stent for the treatment of single de novo lesions in the native coronary arteries.

METHODS

One hundred and three patients with symptomatic coronary artery disease were treated for single de novo native coronary artery lesions using the Infinnium stent (paclitaxel concentration 1.4 mcg/mm2 released over 48 days) in a multi-centre, prospective study performed on 3 continents (Asia, Europe and South America). The primary safety endpoint was major adverse cardiac events at 30 days (MACE 30d) and efficacy was assessed by in-stent binary restenosis as measured by quantitative coronary angiography (QCA) at six-month follow-up. A clinical follow-up was scheduled at nine months.

RESULTS

The mean patient age was 58.5 years; 70.9% were males; 43.7% had unstable angina and 38.8% previous myocardial infarction. Risk factors included hypertension in 62.1%, hypercholesterolemia in 52.4%, current smoking in 32.0% and diabetes in 28.2%. Stent implantation was successful in all patients, with more than one stent being implanted in 9 patients (8.7%). Hierarchical MACE 30d was 2.9%. At nine months, 101 patients had clinical follow-up (1 patient had died and 1 refused). There was one death (1.0%), one Q-wave myocardial infarction (Q MI) (1.0%), three non-Q MIs (2.9%), one clinically-driven target lesion Coronary Artery Bypass Grafting (CABG) (1.0%), and one clinically-driven target lesion repeat percutaneous coronary intervention (re-PCI) (1.0%). The overall event-free rate at nine months was 93.2%. QCA revealed in-stent and in-segment late loss of 0.38+/-0.49 mm and 0.18+/-0.46 mm, resulting in binary restenosis rates of 7.3% and 8.3%, respectively. There was one case of late stent thrombosis in the patient experiencing the Q MI and subsequent re-PCI.

CONCLUSIONS

The Infinnium paclitaxel-eluting stent appears to be safe and efficacious for the treatment of single de novo lesions in coronary arteries in a patient population with symptomatic coronary artery disease (CAD).

Selection and characterization of replicon variants dually resistant to thumb- and palm-binding nonnucleoside polymerase inhibitors of the hepatitis C virus

Multiple nonnucleoside inhibitor binding sites have been identified within the hepatitis C virus (HCV) polymerase, including in the palm and thumb domains. After a single treatment with a thumb site inhibitor (thiophene-2-carboxylic acid NNI-1), resistant HCV replicon variants emerged that contained mutations at residues Leu419, Met423, and Ile482 in the polymerase thumb domain. Binding studies using wild-type (WT) and mutant enzymes and structure-based modeling showed that the mechanism of resistance is through the reduced binding of the inhibitor to the mutant enzymes. Combined treatment with a thumb- and a palm-binding polymerase inhibitor had a dramatic impact on the number of replicon colonies able to replicate in the presence of both inhibitors. A more exact characterization through molecular cloning showed that 97.7% of replicons contained amino acid substitutions that conferred resistance to either of the inhibitors. Of those, 65% contained simultaneously multiple amino acid substitutions that conferred resistance to both inhibitors. Double-mutant replicons Met414Leu and Met423Thr were predominantly selected, which showed reduced replication capacity compared to the WT replicon. These findings demonstrate the selection of replicon variants dually resistant to two NS5B polymerase inhibitors binding to different sites of the enzyme. Additionally, these findings provide initial insights into the in vitro mutational threshold of the HCV NS5B polymerase and the potential impact of viral fitness on the selection of multiple-resistant mutants.

In vitro selected Con1 subgenomic replicons resistant to 2'-C-methyl-cytidine or to R1479 show lack of cross resistance

The HCV polymerase is an attractive target for the development of new and specific anti-HCV drugs. Herein, the characterization of the inhibitory effect of 2'-C-Methyl-Cytidine shows that it is a potent inhibitor of both genotype 1b and 1a HCV replicon replication, both of laboratory-optimized as well as of NS5B clinical isolates-chimera replicons. The corresponding 5'-triphosphate derivative is a potent inhibitor of native HCV replicase isolated from replicon cells and of the recombinant genotype 1b and 1a HCV polymerase-mediated RNA synthesis. Resistance to 2'-C-Methyl-Cytidine was mapped to amino acid substitution S282T in the NS5B coding region. Cross-resistance was observed to 2'-C-Methyl-Adenosine but not to interferon alpha-2a, to non-nucleoside HCV polymerase inhibitors or to R1479, a new and potent nucleoside inhibitor of NS5B polymerase. In vitro studies mapped resistance to R1479 to amino acid substitutions S96T and S96T/N142T of the NS5B polymerase. These mutations did not confer resistance to 2-C-Methyl-Cytidine, thus confirming the lack of cross-resistance between these two HCV inhibitors. These data will allow the optimization of new polymerase inhibitors and their use in combination therapy.

The novel nucleoside analog R1479 (4'-azidocytidine) is a potent inhibitor of NS5B-dependent RNA synthesis and hepatitis C virus replication in cell culture

Hepatitis C virus (HCV) polymerase activity is essential for HCV replication. Targeted screening of nucleoside analogs identified R1479 (4'-azidocytidine) as a specific inhibitor of HCV replication in the HCV subgenomic replicon system (IC(50) = 1.28 microM) with similar potency compared with 2'-C-methylcytidine (IC(50) = 1.13 microM). R1479 showed no effect on cell viability or proliferation of HCV replicon or Huh-7 cells at concentrations up to 2 mM. HCV replicon RNA could be fully cleared from replicon cells after prolonged incubation with R1479. The corresponding 5'-triphosphate derivative (R1479-TP) is a potent inhibitor of native HCV replicase isolated from replicon cells and of recombinant HCV polymerase (NS5B)-mediated RNA synthesis activity. R1479-TP inhibited RNA synthesis as a CTP-competitive inhibitor with a K(i) of 40 nM. On an HCV RNA-derived template substrate (complementary internal ribosome entry site), R1479-TP showed similar potency of NS5B inhibition compared with 3'-dCTP. R1479-TP was incorporated into nascent RNA by HCV polymerase and reduced further elongation with similar efficiency compared with 3'-dCTP under the reaction conditions. The S282T point mutation in the coding sequence of NS5B confers resistance to inhibition by 2'-C-MeATP and other 2'-methyl-nucleotides. In contrast, the S282T mutation did not confer cross-resistance to R1479.

Functional constraints of influenza A virus epitopes limit escape from cytotoxic T lymphocytes

Viruses can exploit a variety of strategies to evade immune surveillance by cytotoxic T lymphocytes (CTL), including the acquisition of mutations in CTL epitopes. Also for influenza A viruses a number of amino acid substitutions in the nucleoprotein (NP) have been associated with escape from CTL. However, other previously identified influenza A virus CTL epitopes are highly conserved, including the immunodominant HLA-A*0201-restricted epitope from the matrix protein, M1(58-66). We hypothesized that functional constraints were responsible for the conserved nature of influenza A virus CTL epitopes, limiting escape from CTL. To assess the impact of amino acid substitutions in conserved epitopes on viral fitness and recognition by specific CTL, we performed a mutational analysis of CTL epitopes. Both alanine replacements and more conservative substitutions were introduced at various positions of different influenza A virus CTL epitopes. Alanine replacements for each of the nine amino acids of the M1(58-66) epitope were tolerated to various extents, except for the anchor residue at the second position. Substitution of anchor residues in other influenza A virus CTL epitopes also affected viral fitness. Viable mutant viruses were used in CTL recognition experiments. The results are discussed in the light of the possibility of influenza viruses to escape from specific CTL. It was speculated that functional constraints limit variation in certain epitopes, especially at anchor residues, explaining the conserved nature of these epitopes.