Inhibition of human cytomegalovirus immediate-early gene expression by an antisense oligonucleotide complementary to immediate-early RNA

Mechanisms of Action of the US Food and Drug Administration-Approved Antisense Oligonucleotide Drugs

Antisense oligonucleotides (ASOs) are single stranded nucleic acids that target RNA. The US Food and Drug Administration has approved ASOs for several diseases. ASOs utilize three principal modes of action (MOA). The first MOA is initiated by base-pairing between the ASO and its target mRNA, followed by RNase H-dependent mRNA degradation. The second MOA is triggered by ASOs that occlude splice acceptor sites in pre-mRNAs leading to skipping of a mutation-bearing exon. The third MOA involves ASOs that sterically hinder mRNA function, often inhibiting translation. ASOs contain a variety of modifications to the sugar-phosphate backbone and bases that stabilize the ASO or render them resistant to RNase activity. RNase H-dependent ASOs include inotersen and eplontersen (for hereditary transthyretin amyloidosis), fomiversen (for opportunistic cytomegalovirus infection), mipomersen (for familial hypercholesterolemia), and tofersen [for amyotrophic lateral sclerosis (ALS)]. Splice modulating ASOs include nursinersen (for spinal muscular atrophy) and eteplirsen, golodirsen, viltolarsen, and casimersen (all for the treatment of Duchenne muscular dystrophy). In addition, a designer ASO, milasen, was used to treat a single individual afflicted with Batten disease. Since ASO design relies principally upon knowledge of mRNA sequence, the bench to bedside pipeline for ASOs is expedient compared with protein-directed drugs. [Graphical abstract available.].

Advancements in clinical RNA therapeutics: Present developments and prospective outlooks

RNA molecules have emerged as promising clinical therapeutics due to their ability to target "undruggable" proteins or molecules with high precision and minimal side effects. Nevertheless, the primary challenge in RNA therapeutics lies in rapid degradation and clearance from systemic circulation, the inability to traverse cell membranes, and the efficient intracellular delivery of bioactive RNA molecules. In this review, we explore the implications of RNAs in diseases and provide a chronological overview of the development of RNA therapeutics. Additionally, we summarize the technological advances in RNA-screening design, encompassing various RNA databases and design platforms. The paper then presents an update on FDA-approved RNA therapeutics and those currently undergoing clinical trials for various diseases, with a specific emphasis on RNA medicine and RNA vaccines.

RNA-based therapeutics: an overview and prospectus

The growing understanding of RNA functions and their crucial roles in diseases promotes the application of various RNAs to selectively function on hitherto "undruggable" proteins, transcripts and genes, thus potentially broadening the therapeutic targets. Several RNA-based medications have been approved for clinical use, while others are still under investigation or preclinical trials. Various techniques have been explored to promote RNA intracellular trafficking and metabolic stability, despite significant challenges in developing RNA-based therapeutics. In this review, the mechanisms of action, challenges, solutions, and clinical application of RNA-based therapeutics have been comprehensively summarized.

The Medicinal Chemistry of Artificial Nucleic Acids and Therapeutic Oligonucleotides

Nucleic acids play a central role in human biology, making them suitable and attractive tools for therapeutic applications. While conventional drugs generally target proteins and induce transient therapeutic effects, nucleic acid medicines can achieve long-lasting or curative effects by targeting the genetic bases of diseases. However, native oligonucleotides are characterized by low in vivo stability due to nuclease sensitivity and unfavourable physicochemical properties due to their polyanionic nature, which are obstacles to their therapeutic use. A myriad of synthetic oligonucleotides have been prepared in the last few decades and it has been shown that proper chemical modifications to either the nucleobase, the ribofuranose unit or the phosphate backbone can protect the nucleic acids from degradation, enable efficient cellular uptake and target localization ensuring the efficiency of the oligonucleotide-based therapy. In this review, we present a summary of structure and properties of artificial nucleic acids containing nucleobase, sugar or backbone modifications, and provide an overview of the structure and mechanism of action of approved oligonucleotide drugs including gene silencing agents, aptamers and mRNA vaccines.

Microbial Metabolites: The Emerging Hotspot of Antiviral Compounds as Potential Candidates to Avert Viral Pandemic Alike COVID-19

The present global COVID-19 pandemic caused by the noble pleomorphic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a vulnerable situation in the global healthcare and economy. In this pandemic situation, researchers all around the world are trying their level best to find suitable therapeutics from various sources to combat against the SARS-CoV-2. To date, numerous bioactive compounds from different sources have been tested to control many viral diseases. However, microbial metabolites are advantageous for drug development over metabolites from other sources. We herein retrieved and reviewed literatures from PubMed, Scopus and Google relevant to antiviral microbial metabolites by searching with the keywords "antiviral microbial metabolites," "microbial metabolite against virus," "microorganism with antiviral activity," "antiviral medicine from microbial metabolite," "antiviral bacterial metabolites," "antiviral fungal metabolites," "antiviral metabolites from microscopic algae' and so on. For the same purpose, the keywords "microbial metabolites against COVID-19 and SARS-CoV-2" and "plant metabolites against COVID-19 and SARS-CoV-2" were used. Only the full text literatures available in English and pertinent to the topic have been included and those which are not available as full text in English and pertinent to antiviral or anti-SARS-CoV-2 activity were excluded. In this review, we have accumulated microbial metabolites that can be used as antiviral agents against a broad range of viruses including SARS-CoV-2. Based on this concept, we have included 330 antiviral microbial metabolites so far available to date in the data bases and were previously isolated from fungi, bacteria and microalgae. The microbial source, chemical nature, targeted viruses, mechanism of actions and IC50/EC50 values of these metabolites are discussed although mechanisms of actions of many of them are not yet elucidated. Among these antiviral microbial metabolites, some compounds might be very potential against many other viruses including coronaviruses. However, these potential microbial metabolites need further research to be developed as effective antiviral drugs. This paper may provide the scientific community with the possible secret of microbial metabolites that could be an effective source of novel antiviral drugs to fight against many viruses including SARS-CoV-2 as well as the future viral pandemics.

Deliver the promise: RNAs as a new class of molecular entities for therapy and vaccination

The concepts of developing RNAs as new molecular entities for therapies have arisen again and again since the discoveries of antisense RNAs, direct RNA-protein interactions, functional noncoding RNAs, and RNA-directed gene editing. The feasibility was demonstrated with the development and utilization of synthetic RNA agents to selectively control target gene expression, modulate protein functions or alter the genome to manage diseases. Rather, RNAs are labile to degradation and cannot cross cell membrane barriers, making it hard to develop RNA medications. With the development of viable RNA technologies, such as chemistry and pharmaceutics, eight antisense oligonucleotides (ASOs) (fomivirsen, mipomersen, eteplirsen, nusinersen, inotersen, golodirsen, viltolarsen and casimersen), one aptamer (pegaptanib), and three small interfering RNAs (siRNAs) (patisiran, givosiran and lumasiran) have been approved by the United States Food and Drug Administration (FDA) for therapies, and two mRNA vaccines (BNT162b2 and mRNA-1273) under Emergency Use Authorization for the prevention of COVID-19. Therefore, RNAs have become a great addition to small molecules, proteins/antibodies, and cell-based modalities to improve the public health. In this article, we first summarize the general characteristics of therapeutic RNA agents, including chemistry, common delivery strategies, mechanisms of actions, and safety. By overviewing individual RNA medications and vaccines approved by the FDA and some agents under development, we illustrate the unique compositions and pharmacological actions of RNA products. A new era of RNA research and development will likely lead to commercialization of more RNA agents for medical use, expanding the range of therapeutic targets and increasing the diversity of molecular modalities.

Developing therapeutic approaches for twenty-first-century emerging infectious viral diseases

The twenty-first century has already recorded more than ten major epidemic or pandemic virus emergence events, including the ongoing and devastating coronavirus disease 2019 (COVID-19) pandemic. As viral disease emergence is expected to accelerate, these data dictate a need for proactive approaches to develop broadly active family-specific and cross-family therapeutics for use in future disease outbreaks. Emphasis should focus not only on the development of broad-spectrum small-molecule and antibody direct-acting antivirals, but also on host-factor therapeutics, including repurposing previously approved or in-pipeline drugs. Another new class of therapeutics with great antiviral therapeutic potential is RNA-based therapeutics. Rather than only focusing on known risks, dedicated efforts must be made toward pre-emptive research focused on outbreak-prone virus families, ultimately offering a strategy to shorten the gap between outbreak and response. Emphasis should also focus on orally available drugs for outpatient use, if possible, and on identifying combination therapies that combat viral and immune-mediated pathologies, extend the effectiveness of therapeutic windows and reduce drug resistance. While such an undertaking will require new vision, dedicated funding and private, federal and academic partnerships, this approach offers hope that global populations need never experience future pandemics such as COVID-19.

Pharmacokinetics and Proceedings in Clinical Application of Nucleic Acid Therapeutics

Oligonucleotide therapeutics are a novel promising class of drugs designed to specifically target either coding or non-coding RNA molecules to revolutionize treatment of various diseases. During preclinical development, investigations of the pharmacokinetic characteristics of these oligonucleotide-based drug candidates are essential. Oligonucleotides possess a long history of chemical modifications to enhance their stability and binding affinity, as well as reducing toxicity. Phosphorothioate backbone modifications of oligonucleotides were a hallmark of this development process that greatly enhanced plasma stability and protein binding of these agents. Modifications such as 2'-O-methylation further improved stability, while other modifications of the ribose, such as locked nucleic acid (LNA) modification, significantly increased binding affinity, potency, and tissue half-life. These attributes render oligonucleotide therapeutics able to regulate protein expression in both directions depending on the target RNA. Thus, a growing interest has emerged using these oligonucleotides in the treatment of neurodegenerative and cardiac disorders as well as cancer, since the deregulation of certain coding and non-coding RNAs plays a key role in the development of these diseases. Cutting edge research is being performed in the field of non-coding RNAs, identifying potential therapeutic targets, and developing novel oligonucleotide-based agents that outperform classical drugs. Some of these agents are either in clinical trials showing promising results or are already US Food and Drug Administration (FDA) approved, with more oligonucleotides being developed for therapeutic purposes. This is the advent of mechanism-based next-generation therapeutics for a wide range of diseases.

In vivo and in vitro studies of antisense oligonucleotides - a review

The potential of antisense oligonucleotides in gene silencing was discovered over 40 years ago, which resulted in the growing interest in their chemistry, mechanism of action, and metabolic pathways. This review summarizes the selected mechanisms of antisense drug action, as well as therapeutics which are to date approved by the Food and Drug Administration and European Medicines Agency. Moreover, bioanalytical methods used for ASO pharmacokinetics and metabolism studies are briefly summarized. Special attention is paid to the primary pharmacokinetic properties of the different chemistry classes of antisense oligonucleotides. Moreover, in vivo and in vitro metabolic pathways of these compounds are widely described with the emphasis on the different animal models as well as in vitro models, including tissues homogenates, enzyme solutions, and human liver microsomes.

Antisense antibacterial compounds

Extensive antibiotic use combined with poor historical drug stewardship practices have created a medical crisis in which once treatable bacterial infections are now increasingly unmanageable. To combat this, new antibiotics will need to be developed and safeguarded. An emerging class of antibiotics based upon nuclease-stable antisense technologies has proven valuable in preclinical testing against a variety of bacterial pathogens. This review describes the current state of development of antisense-based antibiotics, the mechanisms thus far employed by these compounds, and possible future avenues of research.

Human cytomegalovirus IE2 drives transcription initiation from a select subset of late infection viral promoters by host RNA polymerase II

Herpesvirus late promoters activate gene expression after viral DNA synthesis has begun. Alphaherpesviruses utilize a viral immediate-early protein to do this, whereas beta- and gammaherpesviruses primarily use a 6-member set of viral late-acting transcription factors (LTF) that are drawn to a TATT sequence in the late promoter. The betaherpesvirus, human cytomegalovirus (HCMV), produces three immediate-early 2 protein isoforms, IE2-86, IE2-60, IE2-40, late in infection, but whether they activate late viral promoters is unknown. Here, we quickly degrade the IE2 proteins in late infection using dTag methodology and analyze effects on transcription using customized PRO-Seq and computational methods combined with multiple validation methods. We discover that the IE2 proteins selectively drive RNA Pol II transcription initiation at a subset of viral early-late and late promoters common to different HCMV strains, but do not substantially affect Pol II transcription of the 9,942 expressed host genes. Most of the IE2-activated viral late infection promoters lack the TATT sequence bound by the HCMV UL87-encoded LTF. The HCMV TATT-binding protein is not mechanistically involved in late RNA expression from the IE2-activated TATT-less UL83 (pp65) promoter, as it is for the TATT-containing UL82 (pp71) promoter. While antecedent viral DNA synthesis is necessary for transcription from the late infection viral promoters, continued viral DNA synthesis is unnecessary. We conclude that in late infection the IE2 proteins target a distinct subset of HCMV early-late and late promoters for transcription initiation by RNA Pol II. Commencement of viral DNA replication renders the HCMV genome late promoters susceptible to late-acting viral transcription factors.

The herpesvirus subfamilies differ in the viral proteins used in generating the cascade of viral immediate-early, early, early-late, or late gene transcription. With the application of advanced technologies, we discovered that the betaherpesvirus, human cytomegalovirus, has evolved strategies analogous to those used by both alpha- and gammaherpesviruses to bring about RNA Pol II transcription from its late infection promoters. Like alphaherpesviruses, human cytomegalovirus purposes a pivotal immediate-early viral transcription factor to initiate transcription from early, early-late, and late viral promoters. However, the cytomegalovirus transcription factor only targets a select set of viral early-late and late promoters without appreciably affecting host promoters at late times. Most of these late infection viral promoters are structurally and mechanistically different from promoters activated by the 6-member viral transcription factor complex that is analogous to the transcription factor complex utilized by gammaherpesviruses. Human cytomegalovirus genome amplification must first take place, but need not continue, to enable the two different mechanisms of late viral promoter activation.

Chemical Development of Therapeutic Oligonucleotides

The development of several different chemical modifications of nucleic acids, with improved base-pairing affinity and specificity as well as increased resistance against nucleases, has been described. These new chemistries have allowed the synthesis of different types of therapeutic oligonucleotides. Here we discuss selected chemistries used in antisense oligonucleotide (ASO) applications (e.g., small interfering RNA (siRNA), RNase H activation, translational block, splice-switching, and also as aptamers). Recently approved oligonucleotide-based drugs are also presented briefly.

Bright and Early: Inhibiting Human Cytomegalovirus by Targeting Major Immediate-Early Gene Expression or Protein Function

The human cytomegalovirus (HCMV), one of eight human herpesviruses, establishes lifelong latent infections in most people worldwide. Primary or reactivated HCMV infections cause severe disease in immunosuppressed patients and congenital defects in children. There is no vaccine for HCMV, and the currently approved antivirals come with major limitations. Most approved HCMV antivirals target late molecular processes in the viral replication cycle including DNA replication and packaging. “Bright and early” events in HCMV infection have not been exploited for systemic prevention or treatment of disease. Initiation of HCMV replication depends on transcription from the viral major immediate-early (IE) gene. Alternative transcripts produced from this gene give rise to the IE1 and IE2 families of viral proteins, which localize to the host cell nucleus. The IE1 and IE2 proteins are believed to control all subsequent early and late events in HCMV replication, including reactivation from latency, in part by antagonizing intrinsic and innate immune responses. Here we provide an update on the regulation of major IE gene expression and the functions of IE1 and IE2 proteins. We will relate this insight to experimental approaches that target IE gene expression or protein function via molecular gene silencing and editing or small chemical inhibitors.

Development and Clinical Translation of Approved Gene Therapy Products for Genetic Disorders

The field of gene therapy is striving more than ever to define a path to the clinic and the market. Twenty gene therapy products have already been approved and over two thousand human gene therapy clinical trials have been reported worldwide. These advances raise great hope to treat devastating rare and inherited diseases as well as incurable illnesses. Understanding of the precise pathomechanisms of diseases as well as the development of efficient and specific gene targeting and delivery tools are revolutionizing the global market. Currently, human cancers and monogenic disorders are indications number one. The elevated prevalence of genetic disorders and cancers, clear gene manipulation guidelines and increasing financial support for gene therapy in clinical trials are major trends. Gene therapy is presently starting to become commercially profitable as a number of gene and cell-based gene therapy products have entered the market and the clinic. This article reviews the history and development of twenty approved human gene and cell-based gene therapy products that have been approved up-to-now in clinic and markets of mainly North America, Europe and Asia.

Inherited Retinal Disease Therapies Targeting Precursor Messenger Ribonucleic Acid

Inherited retinal diseases are an extremely diverse group of genetically and phenotypically heterogeneous conditions characterized by variable maturation of retinal development, impairment of photoreceptor cell function and gradual loss of photoreceptor cells and vision. Significant progress has been made over the last two decades in identifying the many genes implicated in inherited retinal diseases and developing novel therapies to address the underlying genetic defects. Approximately one-quarter of exonic mutations related to human inherited diseases are likely to induce aberrant splicing products, providing opportunities for the development of novel therapeutics that target splicing processes. The feasibility of antisense oligomer mediated splice intervention to treat inherited diseases has been demonstrated in vitro, in vivo and in clinical trials. In this review, we will discuss therapeutic approaches to treat inherited retinal disease, including strategies to correct splicing and modify exon selection at the level of pre-mRNA. The challenges of clinical translation of this class of emerging therapeutics will also be discussed.

Drug delivery system of therapeutic oligonucleotides

Therapeutic oligonucleotides are promising technologies. Nevertheless, improvement of their efficacy is an important issue. Introducing this drug delivery system (DDS) makes for a great enhancement for delivery of oligonucleotides to targeted tissue or cells. The strategy of DDS for therapeutic oligonucleotides is divided into four categories, A) single piece of oligonucleotide, B) oligonucleotide-ligand conjugate, C) oligonucleotide-polymer conjugate, and D) nanoparticle. In this review we will describe those basic concepts, especially for the technology of conjugating ligand. In addition, we developed a new technology, heteroduplex oligonucleotide (HDO), binding ligand-molecule to antisense oligonucleotide indirectly. We also outline α-tocopherol (a natural isomer of vitamin E) conjugated HDO.

Antisense Oligonucleotide Mediated Splice Correction of a Deep Intronic Mutation in OPA1

Inherited optic neuropathies (ION) present an important cause of blindness in the European working-age population. Recently we reported the discovery of four independent families with deep intronic mutations in the main inherited optic neuropathies gene OPA1. These deep intronic mutations cause mis-splicing of the OPA1 pre-messenger-RNA transcripts by creating cryptic acceptor splice sites. As a rescue strategy we sought to prevent mis-splicing of the mutant pre-messenger-RNA by applying 2'O-methyl-antisense oligonucleotides (AONs) with a full-length phosphorothioate backbone that target the cryptic acceptor splice sites and the predicted novel branch point created by the deep intronic mutations, respectively. Transfection of patient-derived primary fibroblasts with these AONs induced correct splicing of the mutant pre-messenger-RNA in a time and concentration dependent mode of action, as detected by pyrosequencing of informative heterozygous variants. The treatment showed strong rescue effects (~55%) using the cryptic acceptor splice sites targeting AON and moderate rescue (~16%) using the branch point targeting AON. The highest efficacy of Splice correction could be observed 4 days after treatment however, significant effects were still seen 14 days post-transfection. Western blot analysis revealed increased amounts of OPA1 protein with maximum amounts at ~3 days post-treatment. In summary, we provide the first mutation-specific in vitro rescue strategy for OPA1 deficiency using synthetic AONs.

Pre-mRNA mis-splicing of sarcomeric genes in heart failure

Pre-mRNA splicing is an important biological process that allows production of multiple proteins from a single gene in the genome, and mainly contributes to protein diversity in eukaryotic organisms. Alternative splicing is commonly governed by RNA binding proteins to meet the ever-changing demands of the cell. However, the mis-splicing may lead to human diseases. In the heart of human, mis-regulation of alternative splicing has been associated with heart failure. In this short review, we focus on alternative splicing of sarcomeric genes and review mis-splicing related heart failure with relatively well studied Sarcomeric genes and splicing mechanisms with identified regulatory factors. The perspective of alternative splicing based therapeutic strategies in heart failure has also been discussed.

A cellular high-throughput screening approach for therapeutic trans-cleaving ribozymes and RNAi against arbitrary mRNA disease targets

Major bottlenecks in development of therapeutic post transcriptional gene silencing (PTGS) agents (e.g. ribozymes, RNA interference, antisense) include the challenge of mapping rare accessible regions of the mRNA target that are open for annealing and cleavage, testing and optimization of agents in human cells to identify lead agents, testing for cellular toxicity, and preclinical evaluation in appropriate animal models of disease. Methods for rapid and reliable cellular testing of PTGS agents are needed to identify potent lead candidates for optimization. Our goal was to develop a means of rapid assessment of many RNA agents to identify a lead candidate for a given mRNA associated with a disease state. We developed a rapid human cell-based screening platform to test efficacy of hammerhead ribozyme (hhRz) or RNA interference (RNAi) constructs, using a model retinal degeneration target, human rod opsin (RHO) mRNA. The focus is on RNA Drug Discovery for diverse retinal degeneration targets. To validate the approach, candidate hhRzs were tested against NUH↓ cleavage sites (N = G,C,A,U; H = C,A,U) within the target mRNA of secreted alkaline phosphatase (SEAP), a model gene expression reporter, based upon in silico predictions of mRNA accessibility. HhRzs were embedded in a larger stable adenoviral VAI RNA scaffold for high cellular expression, cytoplasmic trafficking, and stability. Most hhRz expression plasmids exerted statistically significant knockdown of extracellular SEAP enzyme activity when readily assayed by a fluorescence enzyme assay intended for high throughput screening (HTS). Kinetics of PTGS knockdown of cellular targets is measureable in live cells with the SEAP reporter. The validated SEAP HTS platform was transposed to identify lead PTGS agents against a model hereditary retinal degeneration target, RHO mRNA. Two approaches were used to physically fuse the model retinal gene target mRNA to the SEAP reporter mRNA. The most expedient way to evaluate a large set of potential VAI-hhRz expression plasmids against diverse NUH↓ cleavage sites uses cultured human HEK293S cells stably expressing a dicistronic Target-IRES-SEAP target fusion mRNA. Broad utility of this rational RNA drug discovery approach is feasible for any ophthalmological disease-relevant mRNA targets and any disease mRNA targets in general. The approach will permit rank ordering of PTGS agents based on potency to identify a lead therapeutic compound for further optimization.

Oligonucleotide therapeutics: chemistry, delivery and clinical progress

Oligonucleotide therapeutics have the potential to become a third pillar of drug development after small molecules and protein therapeutics. However, the three approved oligonucleotide drugs over the past 17 years have not proven to be highly successful in a commercial sense. These trailblazer drugs have nonetheless laid the foundations for entire classes of drug candidates to follow. This review will examine further advances in chemistry that are earlier in the pipeline of oligonucleotide drug candidates. Finally, we consider the possible effect of delivery systems that may provide extra footholds to improve the potency and specificity of oligonucleotide drugs. Our overview focuses on strategies to imbue antisense oligonucleotides with more drug-like properties and their applicability to other nucleic acid therapeutics.

An update on the management and prevention of cytomegalovirus infection following allogeneic hematopoietic stem cell transplantation

ABSTRACT 

A significant progress has been made in deciphering critical aspects of the biology and immunology of CMV infection in the allogeneic stem cell transplantation setting. Genetic traits predisposing to active CMV infection and CMV end-organ disease have begun to be delineated. Reliable molecular assays for CMV DNA load quantitation in body fluids have been developed. Elucidation of immune mechanisms affording control of CMV infection will help to improve the management of active CMV infection. Finally, the advent of new CMV-specific antivirals and promising vaccine prototypes as well as the development of fine procedures for large-scale ex vivo generation of functional CMV-specific T cells for adoptive T cell transfer therapies will certainly minimize the negative impact of CMV on survival in these patients.

Immediate-Early (IE) gene regulation of cytomegalovirus: IE1- and pp71-mediated viral strategies against cellular defenses

Three crucial hurdles hinder studies on human cytomegalovirus (HCMV): strict species specificity, differences between in vivo and in vitro infection, and the complexity of gene regulation. Ever since the sequencing of the whole genome was first accomplished, functional studies on individual genes have been the mainstream in the CMV field. Gene regulation has therefore been elucidated in a more detailed fashion. However, viral gene regulation is largely controlled by both cellular and viral components. In other words, viral gene expression is determined by the virus-host interaction. Generally, cells respond to viral infection in a defensive pattern; at the same time, viruses try to counteract the cellular defense or else hide in the host (latency). Viruses evolve effective strategies against cellular defense in order to achieve replicative success. Whether or not they are successful, cellular defenses remain in the whole viral replication cycle: entry, immediate-early (IE) gene expression, early gene expression, DNA replication, late gene expression, and viral egress. Many viral strategies against cellular defense, and which occur in the immediate-early time of viral infection, have been documented. In this review, we will summarize the documented biological functions of IE1 and pp71 proteins, especially with regard to how they counteract cellular intrinsic defenses.

Chemistry, properties, and in vitro and in vivo applications of 2'-O-methoxyethyl-4'-thioRNA, a novel hybrid type of chemically modified RNA

We report the synthesis, properties, and in vitro and in vivo applications of 2'-O-methoxyethyl-4'-thioRNA (MOE-SRNA), a novel type of hybrid chemically modified RNA. In its hybridization with complementary RNA, MOE-SRNA showed a moderate improvement of Tm value (+3.4 °C relative to an RNA:RNA duplex). However, the results of a comprehensive comparison of the nuclease stability of MOE-SRNA relative to 2'-O-methoxyethylRNA (MOERNA), 2'-O-methyl-4'-thioRNA (Me-SRNA), 2'-O-methylRNA (MeRNA), 4'-thioRNA (SRNA), and natural RNA revealed that MOE-SRNA had the highest stability (t1/2 >48 h in human plasma). Because of the favorable properties of MOE-SRNA, we evaluated its in vitro and in vivo potencies as an anti-microRNA oligonucleotide against miR-21. Although the in vitro potency of MOE-SRNA was moderate, its in vivo potency was significant for the suppression of tumor growth (similar to that of MOERNA).

Advances in targeted delivery of small interfering RNA using simple bioconjugates

INTRODUCTION

Development of drugs based on RNA interference by small interfering RNA (siRNA) has been progressing slowly due to a number of challenges associated with the in vivo behavior of siRNA. A central problem is controlling siRNA delivery to specific cell types. Here, we review existing literature on one type of strategy for solving the issue of cell-specific delivery of siRNA, namely delivering the siRNA as part of simple bioconjugate constructs.

AREAS COVERED

This review presents current experience from strategies aimed at targeting siRNA to specific cell types, by associating the siRNA with a targeting moiety, in a simple bioconjugate construct. We discuss the use of different types of targeting moieties, as well as the different conjugation strategies employed for preparing these bioconjugate constructs that deliver the siRNA to target cells. We focus especially on the in-built or passive functionalities associated with each strategy, in order to identify key elements of successful siRNA delivery strategies with potential for further exploration.

EXPERT OPINION

By evaluating the current literature on this subject, we identify strategies and concepts that are suitable for future studies, to enable the development of highly efficient simple bioconjugates for targeted siRNA delivery with therapeutic application.

Identification of cellular proteins that interact with human cytomegalovirus immediate-early protein 1 by protein array assay

Human cytomegalovirus (HCMV) gene expression during infection is characterized as a sequential process including immediate-early (IE), early (E), and late (L)-stage gene expression. The most abundantly expressed gene at the IE stage of infection is the major IE (MIE) gene that produces IE1 and IE2. IE1 has been the focus of study because it is an important protein, not only for viral gene expression but also for viral replication. It is believed that IE1 plays important roles in viral gene regulation by interacting with cellular proteins. In the current study, we performed protein array assays and identified 83 cellular proteins that interact with IE1. Among them, seven are RNA-binding proteins that are important in RNA processing; more than half are nuclear proteins that are involved in gene regulations. Tumorigenesis-related proteins are also found to interact with IE1, implying that the role of IE1 in tumorigenesis might need to be reevaluated. Unexpectedly, cytoplasmic proteins, such as Golgi autoantigen and GGA1 (both related to the Golgi trafficking protein), are also found to be associated with IE1. We also employed a coimmunoprecipitation assay to test the interactions of IE1 and some of the proteins identified in the protein array assays and confirmed that the results from the protein array assays are reliable. Many of the proteins identified by the protein array assay have not been previously reported. Therefore, the functions of the IE1-protein interactions need to be further explored in the future.

RNA interference-mediated targeting of human cytomegalovirus immediate-early or early gene products inhibits viral replication with differential effects on cellular functions

Viral drug toxicity, resistance, and an increasing immunosuppressed population warrant continued research into new avenues for limiting diseases associated with human cytomegalovirus (HCMV). In this study, a small interfering RNA (siRNA), siX3, was designed to target coding sequences within shared exon 3 of UL123 and UL122 transcripts encoding IE1 and IE2 immediate-early proteins of HCMV. Pretreatment of cells with siX3 reduced the levels of viral protein expression, DNA replication, and progeny virus production compared to control siRNA. Two siRNAs against UL54 and overlapping transcripts (UL55-57) were compared to siX3 in HCMV infection and were also found to be effective at inhibiting HCMV replication. Further investigation into the effects of the siRNAs on viral replication showed that pretreatment with each of the siRNAs resulted in an inhibition in the formation of mature replication compartments. The ability of these siRNAs to prevent or reduce certain cytopathic effects associated with HCMV infection was also examined. Infected cells pretreated with siX3, but not siUL54, retained promyelocytic leukemia (PML) protein in cellular PML bodies, an essential component of this host intrinsic antiviral defense. DNA damage response proteins, which are localized in nuclear viral replication compartments, were reduced in the siX3- and siUL54-treated cells. siX3, but not siUL54, prevented DNA damage response signaling early after infection. Therapeutic efficacy was demonstrated by treating cells with siRNAs after HCMV replication had commenced. Together, these findings suggest that siRNAs targeting exon 3 of the major IE genes or the UL54-57 transcripts be further studied for their potential development into anti-HCMV therapeutics.

Variables and strategies in development of therapeutic post-transcriptional gene silencing agents

Post-transcriptional gene silencing (PTGS) agents such as ribozymes, RNAi and antisense have substantial potential for gene therapy of human retinal degenerations. These technologies are used to knockdown a specific target RNA and its cognate protein. The disease target mRNA may be a mutant mRNA causing an autosomal dominant retinal degeneration or a normal mRNA that is overexpressed in certain diseases. All PTGS technologies depend upon the initial critical annealing event of the PTGS ligand to the target RNA. This event requires that the PTGS agent is in a conformational state able to support hybridization and that the target have a large and accessible single-stranded platform to allow rapid annealing, although such platforms are rare. We address the biocomplexity that currently limits PTGS therapeutic development with particular emphasis on biophysical variables that influence cellular performance. We address the different strategies that can be used for development of PTGS agents intended for therapeutic translation. These issues apply generally to the development of PTGS agents for retinal, ocular, or systemic diseases. This review should assist the interested reader to rapidly appreciate critical variables in PTGS development and facilitate initial design and testing of such agents against new targets of clinical interest.

Early inhibitors of human cytomegalovirus: state-of-art and therapeutic perspectives

Human cytomegalovirus (HCMV) infection is associated with severe morbidity and mortality in immunocompromised individuals, mainly transplant recipients and AIDS patients, and is the most frequent cause of congenital malformations in newborn children. To date, few drugs are licensed for the treatment of HCMV infections, most of which target the viral DNA polymerase and suffer from many drawbacks, including long-term toxicity, low potency, and poor bioavailability. In addition, the emergence of drug-resistant viral strains is becoming an increasing problem for disease management. Finally, none of the current anti-HCMV drugs have been approved for the treatment of congenital infections. For all these reasons, there is still a strong need for new anti-HCMV drugs with novel mechanisms of action. The first events of the virus replication cycle, including attachment, entry, immediate-early gene expression, and immediate-early functions—in particular that of Immediate-Early 2 protein—represent attractive targets for the development of novel antiviral compounds. Such inhibitors would block not only the expression of viral immediate-early proteins, which play a key role in the pathogenesis of HCMV infection, but also the host immunomodulation and the changes to cell physiology induced by the first events of virus infection. This review describes the current knowledge on the initial phases of HCMV replication, their validation as potential novel antiviral targets, and the development of compounds that block such processes.

Rapid, cell-based toxicity screen of potentially therapeutic post-transcriptional gene silencing agents

Post-transcriptional gene silencing (PTGS) agents such as antisense, ribozymes and RNA interference (RNAi) have great potential as therapeutics for a variety of eye diseases including retinal and macular degenerations, glaucoma, corneal degenerations, inflammatory and viral conditions. Despite their great potential and over thirty years of academic and corporate research only a single PTGS agent is currently approved for human therapy for a single disease. Substantial challenges exist to achieving both efficacious and safe PTGS agents. Efficacy, as measured in specific target mRNA and protein knockdown, depends upon a number of complex factors including the identification of rare regions of target mRNA accessibility, cellular co-localization of the PTGS agent in sufficient concentration with the target mRNA, and stability of the PTGS agent in the target cells in which it is delivered or expressed. Safety is commonly measured by lack of cytotoxicity or other deleterious cellular responses in cells in which the PTGS agent is delivered or expressed. To relieve major bottlenecks in RNA drug discovery novel, efficient, inexpensive, and rapid tools are needed to facilitate lead identification of the most efficacious PTGS agent, rational optimization of efficacy of the lead agent, and lead agent safety determinations. We have developed a technological platform using cell culture expression systems that permits lead identification and efficacy optimization of PTGS agents against arbitrary disease target mRNAs under relatively high throughput conditions. Here, we extend the technology platform to include PTGS safety determinations in cultured human cells that are expected to represent the common cellular housekeeping microenvironment. We developed a high throughput screening (HTS) cytotoxicity assay in 96-well plate format based around the SYTOX Green dye which is excluded from healthy viable cells and becomes substantially fluorescent only after entering cells and binding to nuclear DNA. In this format we can test a number of PTGS agents for cellular toxicity relative to control elements. We also developed an HTS 96-well plate assay that allows us to assess the impact of any given PTGS agent on stimulating a variety of common cellular stress signaling pathways (e.g. CRE, SRE, AP-1, NFκB, Myc, and NFAT) that could indicate possible deleterious effects of PTGS agents either dependent or independent of base pairing complementarity with target mRNAs. To this end we exploited the secreted alkaline phosphatase (SEAP) Pathway Profiling System where the expression of the secreted reporter protein is coupled to transcriptional activation of a variety of promoter elements involved in common cell signaling pathways. We found that a variety of lead hammerhead ribozyme (hhRz) and short hairpin (shRNA) expression constructs did not exert cytotoxicity in human cells when driven by highly active RNA Pol-III promoters. We also found that most of the cell signaling pathways tested (CRE, SRE, Myc, and NFAT) did not significantly couple through upregulation to expression of the set of PTGS agents tested. AP-1 and NFκB upregulation both appear to couple to the expression of some PTGS agents which likely reflect the known properties of these pathways to be stimulated by abundant small structured RNAs.

Specific regulation of point-mutated K-ras-immortalized cell proliferation by a photodynamic antisense strategy

It has been reported that point mutations in genes are responsible for various cancers, and the selective regulation of gene expression is an important factor in developing new types of anticancer drugs. To develop effective drugs for the regulation of point-mutated genes, we focused on photoreactive antisense oligonucleotides. Previously, we reported that photoreactive oligonucleotides containing 2'-O-psoralenylmethoxyethyl adenosine (2'-Ps-eom) showed drastic photoreactivity in a strictly sequence-specific manner. Here, we demonstrated the specific gene regulatory effects of 2'-Ps-eom on [(12)Val]K-ras mutant (GGT --> GTT). Photo-cross-linking between target mRNAs and 2'-Ps-eom was sequence-specific, and the effect was UVA irradiation-dependent. Furthermore, 2'-Ps-eom was able to inhibit K-ras-immortalized cell proliferation (K12V) but not Vco cells that have the wild-type K-ras gene. These results suggest that the 2'-Ps-eom will be a powerful nucleic acid drug to inhibit the expression of disease-causing point mutation genes, and has great therapeutic potential in the treatment of cancer.

Optical melting measurements of nucleic acid thermodynamics

Optical melting experiments provide measurements of thermodynamic parameters for nucleic acids. These thermodynamic parameters are widely used in RNA structure prediction programs and DNA primer design software. This review briefly summarizes the theory and underlying assumptions of the method and provides practical details for instrument calibration, experimental design, and data interpretation.

New cell-based indicator assays for the detection of human cytomegalovirus infection and screening of inhibitors of viral immediate-early 2 protein activity

AIMS

Expression of early (E) genes of human cytomegalovirus (HCMV) is stimulated cooperatively by the activities of host cell transcription factors and the viral immediate-early 2 (IE2) protein. Taking advantage of the IE2-dependent inducibility of E gene promoters, in this study, we generated cell-based assays in which the expression of the enhanced green fluorescence protein (EGFP) reporter gene was driven by the UL54 or UL112/113 E promoters.

METHODS AND RESULTS

Cell clones derived from a stably transfected human cell line permissive to HCMV replication showed a specific and inducible dose- and time-dependent EGFP response to HCMV infection. The sensitivity of these indicator cells for detecting infectious particles of clinical isolates of HCMV was comparable to that of a conventional plaque assay. The HCMV-induced EGFP expression was completely prevented by treatment of indicator cells with fomivirsen, an antisense oligodeoxynucleotide designed to block IE2 expression, and this inhibitory activity was also observed when the IE2 protein alone was constitutively expressed in EGFP indicator cells.

CONCLUSIONS

The EGFP-based cell assays have proved to be a rapid, sensitive, quantitative and specific system for detection of HCMV and selection of antivirals.

SIGNIFICANCE AND IMPACT OF THE STUDY

These new cell-based assays can be exploited as functional assays to detect infectious HCMV particles, as well as to screen antiviral compounds that interfere with IE2 activity.

A proviral role for CpG in cytomegalovirus infection

TLR9-dependent signaling in plasmacytoid dendritic cells is a key contributor to innate immune defense to mouse CMV infection. We aimed to study the expression and potential contribution of TLR9 signaling in human CMV (HCMV) infection of primary fibroblasts. HCMV infection strongly induced TLR9 expression in two of three fibroblast types tested. Furthermore, the TLR9 ligand CpG-B induced a strong proviral effect when added shortly after HCMV infection, enhancing virus production and cell viability. However, not all CpG classes displayed proviral activity, and this correlated with their IFN-beta-inducing ability. The proviral effect of CpG-B correlated completely with concurrent viral up-regulation of TLR9 in fibroblasts. Importantly, the timing of CpG addition was a critical parameter; in striking contrast to the proviral effect, CpG addition at the time of infection blocked viral uptake and nearly abolished HCMV production. The contrasting and time-dependent effects of CpG on HCMV infectivity reveal a complex interplay between CpG, TLR9, and HCMV infection. Additionally, the data suggest a potentially harmful role for CpG in the promotion of HCMV infection.

Advances in antisense oligonucleotide development for target identification, validation, and as novel therapeutics

Antisense oligonucleotides (As-ODNs) are single stranded, synthetically prepared strands of deoxynucleotide sequences, usually 18–21 nucleotides in length, complementary to the mRNA sequence of the target gene. As-ODNs are able to selectively bind cognate mRNA sequences by sequence-specific hybridization. This results in cleavage or disablement of the mRNA and, thus, inhibits the expression of the target gene. The specificity of the As approach is based on the probability that, in the human genome, any sequence longer than a minimal number of nucleotides (nt), 13 for RNA and 17 for DNA, normally occurs only once. The potential applications of As-ODNs are numerous because mRNA is ubiquitous and is more accessible to manipulation than DNA. With the publication of the human genome sequence, it has become theoretically possible to inhibit mRNA of almost any gene by As-ODNs, in order to get a better understanding of gene function, investigate its role in disease pathology and to study novel therapeutic targets for the diseases caused by dysregulated gene expression. The conceptual simplicity, the availability of gene sequence information from the human genome, the inexpensive availability of synthetic oligonucleotides and the possibility of rational drug design makes As-ODNs powerful tools for target identification, validation and therapeutic intervention. In this review we discuss the latest developments in antisense oligonucleotide design, delivery, pharmacokinetics and potential side effects, as well as its uses in target identification and validation, and finally focus on the current developments of antisense oligonucleotides in therapeutic intervention in various diseases.

Recent perspectives in ocular drug delivery

Anatomy and physiology of the eye makes it a highly protected organ. Designing an effective therapy for ocular diseases, especially for the posterior segment, has been considered as a formidable task. Limitations of topical and intravitreal route of administration have challenged scientists to find alternative mode of administration like periocular routes. Transporter targeted drug delivery has generated a great deal of interest in the field because of its potential to overcome many barriers associated with current therapy. Application of nanotechnology has been very promising in the treatment of a gamut of diseases. In this review, we have briefly discussed several ocular drug delivery systems such as microemulsions, nanosuspensions, nanoparticles, liposomes, niosomes, dendrimers, implants, and hydrogels. Potential for ocular gene therapy has also been described in this article. In near future, a great deal of attention will be paid to develop non-invasive sustained drug release for both anterior and posterior segment eye disorders. A better understanding of nature of ocular diseases, barriers and factors affecting in vivo performance, would greatly drive the development of new delivery systems. Current momentum in the invention of new drug delivery systems hold a promise towards much improved therapies for the treatment of vision threatening disorders.

Topical antisense-oligonucleotides targeting IFN-gamma mRNA improve incidence and severity of herpetic stromal keratitis by cytokine specific and sequence unspecific effects

BACKGROUND

Corneal infection with herpes simplex virus-1 (HSV) can cause an inflammatory eye disease termed herpetic stromal keratitis (HSK). Interferon-gamma (IFN-gamma) is known to be involved in the development of this disease. In this study, antisense oligonucleotides targeting IFN-gamma mRNA (IFN-gamma-ASON) were investigated for their effects in experimental HSK.

METHODS

Splenic cells were used to examine the efficacy of IFN-gamma-ASON to decrease IFN-gamma- release into the cell culture supernatants as measured by ELISA. Mice were corneally infected with 10(5) PFU HSV, and IFN-gamma-ASON were given subepithelially. Alternatively, mice were infected without any further treatment, received only buffer, or received control oligonucleotides (CON) to observe substance specific effects. The animals were followed up clinically for the signs of herpetic keratitis. On days 14 and 28 post infection (p.i.), animals were sacrificed, and eyes were collected for histological analysis. On day 7 p.i., infectious virus particles in the eyes were determined by a plaque assay.

RESULTS

While IFN-gamma-ASON diminished the content of IFN-gamma in a concentration-dependent manner in vitro, CON showed no significant effects. Whereas buffer-treated and only infected mice showed severe necrotizing keratitis on day 14 p.i., this was abolished after treatment with IFN-gamma-ASON, even after 28 and 52 days. CON-treated mice also showed an improved HSK on day 14, but not on day 28. The incidence of the disease was also clearly diminished after treatment with IFN-gamma-ASON at all time points examined. The number of inflammatory cells in both the central and the peripheral cornea were strongly reduced after the application of IFN-gamma-ASON as compared to the controls. In contrast, the infectious viral particles in eyes at day 7 p.i. did not differ between the four groups.

CONCLUSIONS

Topical treatment with IFN-gamma-ASON induced a long-term improvement of the course and the incidence of HSK in the murine model. IFN-gamma seems to be involved in a proinflammatory manner during the pathogenesis of HSK, while the antiviral defense against HSV was not affected by this topical cytokine inhibition. Unspecific CON induced a transient and cytokine independent improvement of HSK.

Amphipathic DNA Polymers are Candidate Vaginal Microbicides and Block Herpes Simplex Virus Binding, Entry and Viral Gene Expression

Background

Amphipathic DNA polymers are promising therapies for the prevention of HIV and genital herpes infections. Recent studies on a panel of such compounds indicated potent activity against HIV binding and entry. This current study was conducted to explore the anti-herpes simplex virus (HSV) activity of the same panel of compounds and to determine their mechanism of activity.

Methods

The anti-HSV activity of a 40-nucleotide degenerate polymer (REP 9), a 40-nucleotide polycytidine amphipathic DNA polymer (REP 9C) and an analogue lacking amphipathic activity (Randomer 3) were compared in plaque reduction assays in the absence or presence of human genital tract secretions; the mechanisms of anti-HSV activity were explored.

Results

REP 9 inhibited HSV infection 10,000-fold, whereas Randomer 3 displayed no anti-HSV activity. The antiviral activity was independent of sequence but was dependent on size: the most potent activity was observed for analogues of 40 nucleotides in length. Mechanistic studies indicated that REP 9 and REP 9C blocked HSV-2 binding and entry, were active when added post-entry, inhibited viral gene expression and blocked HSV-induced apoptosis. Confocal microscopy studies showed rapid delivery of fluorescently tagged REP 9 and REP 9C into human epithelial cells, and delivery was significantly greater in infected cells as compared with uninfected cells. REP 9 exhibited no cytotoxicity and retained anti-HSV activity in the presence of cervicovaginal secretions and when virus was introduced in seminal plasma.

Conclusions

REP 9 and REP 9C represent a novel class of antiviral agents that act by multiple mechanisms. These compounds warrant further development for systemic or topical delivery for the prevention and treatment of HIV and HSV.

Bottlenecks in development of retinal therapeutic post-transcriptional gene silencing agents

Development of post-transcriptional gene silencing (PTGS) agents for therapeutic purposes is an immense challenge in modern biology. Established technologies used to knockdown a specific target RNA and its cognate protein: antisense, ribozyme, RNAi, all conditionally depend upon an initial, critical annealing event of the PTGS ligand to a target RNA. In this review we address the nature of the bottlenecks, emphasizing the biocomplexity of target RNA structure, that currently limit PTGS therapeutic development. We briefly review existing and emerging technologies designed to release these constraints to realize the potential of PTGS agents in gene based therapies.

Ocular delivery of nucleic acids: antisense oligonucleotides, aptamers and siRNA

Nucleic acids have gained a lot of interest for the treatment of ocular diseases. The first to enter in clinic has been Vitravene an antisense oligonucleotide for the treatment of cytomegalovirus (CMV) infection and more recently, research on aptamers have led to the marketing of anti-vascular endothelial growth factor (VEGF) inhibitor (Macugen) for the treatment of age-related macular degeneration (AMD). The siRNAs appear very promising as they are very potent inhibitors of protein expression. Despite their potential, nucleic acids therapeutic targets of nucleic acid-based drugs are mainly located in the posterior segment of the eye requiring invasive administration which can be harmful if repeated. Their intracellular penetration in some cases needs to be enhanced. This is the reason why adequate delivery systems were designed either to insure cellular penetration, protection against degradation or to allow long-term delivery. A combination of both effects was also developed for an implantable system. In conclusion, the intraocular administration of nucleic acids offers interesting perspectives for the treatment of ocular diseases.

Restoring immune defenses via lymphotoxin signaling: lessons from cytomegalovirus

Although primary infection with human cytomegalovirus (HCMV), a beta-herpesvirus, is widespread and acquired early in life, it rarely causes disease in immune-competent individuals. However, in immune-compromised patients HCMV infection or reactivation invariably leads to serious disease, the effective treatment of which remains a difficult clinical problem. Current antiviral therapy is limited not only by toxicity but also by the continual emergence of drugresistant viruses. The limitations of these current therapeutics provides a strong impetus to develop novel approaches that will enhance the host's immune responsiveness while at the same time effectively controlling virus replication. Type I interferon (IFN) plays a critical role in initiating innate antiviral defenses and promoting adaptive responses and lymphotoxin (LT)-alphabeta has recently been identified as an essential effector cytokine regulating the induction of type I IFN during CMV infection. In particular, CMV infection of immune-compromised mice has revealed the immunotherapeutic potential of the lymphotoxin-beta receptor (LTbetaR) signaling pathway to restore immune function and provide protection from CMV mortality. In this review, we discuss the potential benefits and risks associated with LTbetaR-directed immunotherapy for CMV disease and other persistent viral infections.

Virucidal activity of a GT-rich oligonucleotide against herpes simplex virus mediated by glycoprotein B

We have investigated the antiviral mechanism of a phosphorothioate oligonucleotide, ISIS 5652, which has activity against herpes simplex virus (HSV) in the low micromolar range in plaque reduction assays. We isolated a mutant that is resistant to this compound. Marker rescue and sequencing experiments showed that resistance was due to at least one of three mutations in the UL27 gene which result in amino acid changes in glycoprotein B (gB). Because gB has a role in attachment and entry of HSV, we tested the effects of ISIS 5652 at these stages of infection. The oligonucleotide potently inhibited attachment of virus to cells at 4 degrees C; however, the resistant mutant did not exhibit resistance at this stage. Moreover, a different oligonucleotide with little activity in plaque reduction assays was as potent as ISIS 5652 in inhibiting attachment. Similarly, ISIS 5652 was able to inhibit entry of pre-attached virions into cells at 37 degrees C, but the mutant did not exhibit resistance in this assay. The mutant did not attach to or enter cells more quickly than did wild-type virus. Strikingly, incubation of wild-type virus with 1 to 2 microM ISIS 5652 at 37 degrees C led to a time-dependent, irreversible loss of infectivity (virucidal activity). No virucidal activity was detected at 4 degrees C or with an unrelated oligonucleotide at 37 degrees C. The resistant mutant and a marker-rescued derivative containing its gB mutations exhibited substantial resistance to this virucidal activity of ISIS 5652. We hypothesize that the GT-rich oligonucleotide induces a conformational change in gB that results in inactivation of infectivity.

Oligonucleotides as antivirals: dream or realistic perspective?

Many reports have been published on antiviral activity of synthetic oligonucleotides, targeted to act either by a true antisense effect or via non-sequence specific interactions. This short review will try to evaluate the current status of the field by focusing on the effects as reported for inhibition of either HSV-1, HCMV or HIV-1. Following an introduction with a historical background and a brief discussion on the different types of constructs and mechanisms of action, the therapeutic potential of antisense oligonucleotides as antivirals, as well as possible pitfalls upon their evaluation will be discussed.

Functionalization density dependence of single-walled carbon nanotubes cytotoxicity in vitro

The cytotoxic response of cells in culture is dependant on the degree of functionalization of the single-walled carbon nanotube (SWNT). After characterizing a set of water-dispersible SWNTs, we performed in vitro cytotoxicity screens on cultured human dermal fibroblasts (HDF). The SWNT samples used in this exposure include SWNT-phenyl-SO(3)H and SWNT-phenyl-SO(3)Na (six samples with carbon/-phenyl-SO(3)X ratios of 18, 41, and 80), SWNT-phenyl-(COOH)(2) (one sample with carbon/-phenyl-(COOH)(2) ratio of 23), and underivatized SWNT stabilized in 1% Pluronic F108. We have found that as the degree of sidewall functionalization increases, the SWNT sample becomes less cytotoxic. Further, sidewall functionalized SWNT samples are substantially less cytotoxic than surfactant stabilized SWNTs. Even though cell death did not exceed 50% for cells dosed with sidewall functionalized SWNTs, optical and atomic force microscopies show direct contact between cellular membranes and water-dispersible SWNTs; i.e. the SWNTs in aqueous suspension precipitate out and selectively deposit on the membrane.

Antisense approach for the treatment of cytomegalovirus infection

Human cytomegalovirus (HCMV) is the most common viral opportunistic infection in patients suffering with acquired immunodeficiency virus (AIDS). HCMV is a systemic infection that may infect several sites in the body, including the retina, gastrointestinal tract, lungs, liver, and central nervous system. Retinitis is the most frequent manifestation of HCMV infection, occurring in 15-40% of all patients. HCMV is progressive and destroys the retina, eventually leading to blindness. Although, there are several drugs available to treat this disease, they are often of limited efficacy and have significant side-effects. Antisense oligonucleotides represent a novel alternative to the currently available drugs. Due to their high affinity and specificity to target the HCMV RNAs, interest in antisense technology to treat HCMV infections has been intense during the past few years. Two antisense drugs are currently in clinical trials, ISIS 2922 (Formivirsen) and GEM 132.