Antisense oligonucleotides directed against the viral RNA polymerase gene enhance survival of mice infected with influenza A

Interferon mediated prophylactic protection against respiratory viruses conferred by a prototype live attenuated influenza virus vaccine lacking non-structural protein 1

The influenza A non-structural protein 1 (NS1) is known for its ability to hinder the synthesis of type I interferon (IFN) during viral infection. Influenza viruses lacking NS1 (ΔNS1) are under clinical development as live attenuated human influenza virus vaccines and induce potent influenza virus-specific humoral and cellular adaptive immune responses. Attenuation of ΔNS1 influenza viruses is due to their high IFN inducing properties, that limit their replication in vivo. This study demonstrates that pre-treatment with a ΔNS1 virus results in an antiviral state which prevents subsequent replication of homologous and heterologous viruses, preventing disease from virus respiratory pathogens, including SARS-CoV-2. Our studies suggest that ΔNS1 influenza viruses could be used for the prophylaxis of influenza, SARS-CoV-2 and other human respiratory viral infections, and that an influenza virus vaccine based on ΔNS1 live attenuated viruses would confer broad protection against influenza virus infection from the moment of administration, first by non-specific innate immune induction, followed by specific adaptive immunity.

Prophylactic protection against respiratory viruses conferred by a prototype live attenuated influenza virus vaccine

The influenza A non-structural protein 1 (NS1) is known for its ability to hinder the synthesis of type I interferon (IFN) during viral infection. Influenza viruses lacking NS1 (ΔNS1) are under clinical development as live attenuated human influenza virus vaccines and induce potent influenza virus-specific humoral and cellular adaptive immune responses. Attenuation of ΔNS1 influenza viruses is due to their high IFN inducing properties, that limit their replication in vivo. This study demonstrates that pre-treatment with a ΔNS1 virus results in an immediate antiviral state which prevents subsequent replication of homologous and heterologous viruses, preventing disease from virus respiratory pathogens, including SARS-CoV-2. Our studies suggest that ΔNS1 influenza viruses could be used for the prophylaxis of influenza, SARS-CoV-2 and other human respiratory viral infections, and that an influenza virus vaccine based on ΔNS1 live attenuated viruses would confer broad protection against influenza virus infection from the moment of administration, first by non-specific innate immune induction, followed by specific adaptive immunity.

Application of 2'-OMethylRNA' Antisense Oligomer to Control Candida albicans EFG1 Virulence Determinant

Antisense oligomers and their analogs have been successfully utilized to silence gene expression for the treatment of many human diseases; however, the control of yeast’s virulence determinants has never been exploited before. In this sense, this work is based on the key hypothesis that if a pathogen’s genetic sequence is a determinant of virulence, it will be possible to synthesize a nucleic acid mimic based on antisense therapy (AST) that will bind to the mRNA produced, blocking its translation into protein and, consequently, reducing the pathogen virulence phenotype. EFG1 is an important determinant of virulence that is involved in the regulation of the Candida albicans switch from yeast to filamentous form. Thus, our main goal was to design and synthesize an antisense oligonucleotide (ASO) targeting the EFG1 mRNA and to validate its in vitro applicability. The results show that the anti-EFG1 2′-OMethylRNA (2′OMe) oligomer was able to significantly reduce the levels of EFG1 gene expression and of Efg1p protein translation (both approximately 60%), as well as effectively prevent filamentation of C. albicans cells (by 80%). Moreover, it was verified that anti-EFG1 2′OMe keeps the efficacy in different simulated human body fluids. Undeniably, this work provides potentially valuable information for future research into the management of Candida infections, regarding the development of a credible and alternative method to control C. albicans infections, based on AST methodology.

Oligonucleotide therapy: An emerging focus area for drug delivery in chronic inflammatory respiratory diseases

Oligonucleotide-based therapies are advanced novel interventions used in the management of various respiratory diseases such as asthma and Chronic Obstructive Pulmonary Disease (COPD). These agents primarily act by gene silencing or RNA interference. Better methodologies and techniques are the need of the hour that can deliver these agents to tissues and cells in a target specific manner by which their maximum potential can be reached in the management of chronic inflammatory diseases. Nanoparticles play an important role in the target-specific delivery of drugs. In addition, oligonucleotides also are extensively used for gene transfer in the form of polymeric, liposomal and inorganic carrier materials. Therefore, the current review focuses on various novel dosage forms like nanoparticles, liposomes that can be used efficiently for the delivery of various oligonucleotides such as siRNA and miRNA. We also discuss the future perspectives and targets for oligonucleotides in the management of respiratory diseases.

Construction of a Gene Knockdown System Based on Catalytically Inactive ("Dead") Cas9 (dCas9) in Staphylococcus aureus

There has been an absence of an efficient method of gene knockdown in the important human pathogen Staphylococcus aureus like RNA interference in eukaryotes. The previously developed antisense RNA technology is mainly applied for forward genetic screening but is rather limited in specific gene knockdown because of the lack of rational antisense RNA design strategies. Here we report an efficient and specific system for gene knockdown in S. aureus based on the type II clustered regularly interspaced short palindromic repeat (CRISPR) system from Streptococcus pyogenes We can achieve gene silencing with the coexpression of dCas9, an RNA-guided DNA binding protein, and a small guide RNA complementary to the target gene. With this system, we have successfully silenced diverse sets of genes varying in size and expression level in different S. aureus strains. This system exhibited high-efficiency knockdown of both essential and nonessential genes, and its effect is inducible and reversible. In addition, the system can repress the expression of multiple genes simultaneously and silence an entire operon or part of it. This RNA-guided DNA targeting system thus provides a simple, rapid, and affordable method for selective gene knockdown in S. aureus IMPORTANCE Staphylococcus aureus is an important human and animal pathogen that can cause a diversity of infectious diseases. Molecular genetic study of S. aureus has provided an avenue for the understanding of its virulence, pathogenesis, and drug resistance, leading to the discovery of new therapies for the treatment of staphylococcal infections. However, methodologies developed for genetic manipulation of S. aureus usually involve either low efficiency or laborious procedures. Here we report an RNA-guided system for gene knockdown in S. aureus and show its high efficiency and simplicity for selective gene silencing in different strains of S. aureus This simple, rapid, and affordable system may serve as a promising tool for functional gene study in S. aureus, especially for the study of essential genes, thus facilitating the understanding of this pathogen and its interaction with its hosts.

Antisense antimicrobial therapeutics

Antisense antimicrobial therapeutics are synthetic oligomers that silence expression of specific genes. This specificity confers an advantage over broad-spectrum antibiotics by avoiding unintended effects on commensal bacteria. The sequence-specificity and short length of antisense antimicrobials also pose little risk to human gene expression. Because antisense antimicrobials are a platform technology, they can be rapidly designed and synthesized to target almost any microbe. This reduces drug discovery time, and provides flexibility and a rational approach to drug development. Recent work has shown that antisense technology has the potential to address the antibiotic-resistance crisis, since resistance mechanisms for standard antibiotics apparently have no effect on antisense antimicrobials. Here, we describe current reports of antisense antimicrobials targeted against viruses, parasites, and bacteria.

A Conserved Secondary Structural Element in the Coding Region of the Influenza A Virus Nucleoprotein (NP) mRNA Is Important for the Regulation of Viral Proliferation

Influenza A virus is a threat to humans due to seasonal epidemics and infrequent, but dangerous, pandemics that lead to widespread infection and death. Eight segments of RNA constitute the genome of this virus and they encode greater than eight proteins via alternative splicing of coding (+)RNAs generated from the genomic (-)RNA template strand. RNA is essential in its life cycle. A bioinformatics analysis of segment 5, which encodes nucleoprotein, revealed a conserved structural motif in the (+)RNA. The secondary structure proposed by energy minimization and comparative analysis agrees with structure predicted based on experimental data using a 121 nucleotide in vitro RNA construct comprising an influenza A virus consensus sequence and also an entire segment 5 (+)RNA (strain A/VietNam/1203/2004 (H5N1)). The conserved motif consists of three hairpins with one being especially thermodynamically stable. The biological importance of this conserved secondary structure is supported in experiments using antisense oligonucleotides in cell line, which found that disruption of this motif led to inhibition of viral fitness. These results suggest that this conserved motif in the segment 5 (+)RNA might be a candidate for oligonucleotide-based antiviral therapy.

The use of nano-sized acicular material, sliding friction, and antisense DNA oligonucleotides to silence bacterial genes

Viable bacterial cells impaled with a single particle of a nano-sized acicular material formed when a mixture containing the cells and the material was exposed to a sliding friction field between polystyrene and agar gel; hereafter, we refer to these impaled cells as penetrons. We have used nano-sized acicular material to establish a novel method for bacterial transformation. Here, we generated penetrons that carried antisense DNA adsorbed on nano-sized acicular material (α-sepiolite) by providing sliding friction onto the surface of agar gel; we then investigated whether penetron formation was applicable to gene silencing techniques. Antisense DNA was artificially synthesized as 15 or 90mer DNA oligonucleotides based on the sequences around the translation start codon of target mRNAs. Mixtures of bacterial cells with antisense DNA adsorbed on α-sepiolite were stimulated by sliding friction on the surface of agar gel for 60 s. Upon formation of Escherichia coli penetrons, β-lactamase and β-galactosidase expression was evaluated by counting the numbers of colonies formed on LB agar containing ampicillin and by measuring β-galactosidase activity respectively. The numbers of ampicillin resistant colonies and the β-galactosidase activity derived from penetrons bearing antisense DNA (90mer) was repressed to 15% and 25%, respectively, of that of control penetrons which lacked antisense DNA. Biphenyl metabolite, ring cleavage yellow compound produced by Pseudomonas pseudoalcaligenes penetron treated with antisense oligonucleotide DNA targeted to bphD increased higher than that lacking antisense DNA. This result indicated that expression of bphD in P. pseudoalcaligenes penetrons was repressed by antisense DNA that targeted bphD mRNA. Sporulation rates of Bacillus subtilis penetrons treated with antisense DNA (15mer) targeted to spo0A decreased to 24.4% relative to penetrons lacking antisense DNA. This novel method of gene silencing has substantial promise for elucidation of gene function in bacterial species that have been refractory to experimental introduction of exogenous DNA.

Antisense oligonucleotides targeting the RNA binding region of the NP gene inhibit replication of highly pathogenic avian influenza virus H5N1

The H5N1 avian influenza virus (AIV) causes widespread infections in bird and human respiratory tracts, and vaccines and drug therapy are limited in their effectiveness. Recent studies of AIV structures have been published and provide new targets for designing antiviral drugs such as antisense oligonucleotides (AS ODNs), which effectively inhibit gene replication. In this study, we designed and synthesized three AS ODNs (NP267, NP628, NP749) that were specific for the RNA binding region of nucleoprotein (NP) based on AIV structure. Results showed that all three AS ODNs could inhibit viral replication in MDCK cells. The NP628 showed the best antiviral effect of all through viral titers, quantitative RT-PCR and indirect immunofluorescence (IFA) assays. In addition, the liposome mediated NP628 could partially protect the mice from a lethal H5N1 influenza virus challenge. Moreover, the NP628 group had a lower viral titer and lung index in the infected mice when compared with the viral control. Our results showed that AS ODN targeting of the AIV NP gene could potently inhibit AIV H5N1 reproduction, thus, formulating a candidate for an emergent therapeutic drug for the pathogenic H5N1 influenza virus infection.

Packaging signals in the 5'-ends of influenza virus PA, PB1, and PB2 genes as potential targets to develop nucleic-acid based antiviral molecules

In a previous study a 15-mer phosphorothioate oligonucleotide (S-ON) derived from the packaging signal in the 5' end of segment 1 (PB2) of influenza A virus (designated 5-15b) proved markedly inhibitory to virus replication. Here we investigated whether analogous inhibitory S-ONs targeting the 5' end of segments 2 (PB1) and 3 (PA) could be identified and whether viral resistance to S-ONs can be developed. Similar to our earlier result, 20-mer S-ONs reproducing the 5' ends of segments 2 or 3 (complementary to the 3'-coding regions of PB1 and PA, respectively) exerted a powerful antiviral activity against a variety of influenza A virus subtypes in MDCK cells. Serial passage of the A/Taiwan/1/86 H1N1 strain in the presence of S-ON 5-15b or its antisense as5-15b analogue showed that mutant viruses with reduced susceptibility to the S-ON could indeed be generated, although the resistant viruses displayed reduced replicative fitness. Sequencing the resistant viruses identified mutations in the PB1, PB2, PA and M1 genes. Introduction of these changes into the A/PR/8/34 H1N1 strain by reverse genetics, suggested that alterations to RNA function in the packaging regions of segments 2 and 3 were important in developing resistance to S-ON inhibition. However, many of the other sequence changes induced by S-ON treatment were markedly deleterious to virus fitness. We conclude that packaging signals in the influenza A virus polymerase segments provide feasible targets for nucleic acid-based antivirals that may be difficult for the virus to evade through resistance mutations.

Antisense oligonucleotide inhibits avian influenza virus H5N1 replication by single chain antibody delivery system

H5N1 avian influenza virus (AIV) causes widespread infections in poultry and wild birds, and has the potential to emerge as a pandemic threat to human. Antisense oligonucleotides (AS ODNs) are highly effective at inhibiting gene replication. Antibody-mediated delivery is a novel approach to target specific cells and tissues. In this study, we designed and synthesized three AS ODNs (PA4, PA492 and PA1203) specific for conserved region of AIV PA protein, and all the three AS ODNs could inhibit viral replication. The PA492 ODN showed the best antiviral effect by viral titers and quantitative RT-PCR in MDCK cells. The fusion protein scFv-tP was constructed as a single chain variable fragment (scFv) against AIV hemaglutinin antigen with a truncated protamine (tP). The results showed that scFv-tP fusion improved the antiviral effectiveness of PA492 in MDCK cells as measured by viral titers, quantitative RT-PCR and indirect immunofluorescence (IFA) assays. In addition, scFv-tP-delivered PA492 was also found to partially protect mice from lethal H5N1 influenza virus challenge. Using scFv-tP delivery, fluorescein isothiocyanate labeled-PA492 was found to be significantly localized in the lungs, compared to liposome-delivered PA492. Moreover, the fusion protein mediated PA492 had a lower lung index and viral titers in the infected mice as compared with the liposome method. These results provided a potential method for using anti-HA fusion protein for the targeted delivery of AS ODNs against AIV H5N1.

Reduction of liver tumor necrosis factor-alpha expression by targeting delivery of antisense oligonucleotides into Kupffer cells protects rats from fulminant hepatitis

BACKGROUND

Fulminant liver failure can cause extreme mortality due to the lack of effective and targeting therapeutics for the disease. Novel therapeutics using antisense technology require an efficient and safe delivery system with Kupffer cell targeting ability.

METHODS

We explored the capacity of galactosylated low molecular weight chitosan (GLC) to efficiently mediate the antisense oligonucleotide (ASO) TJU-2755 into Kupffer cells, enhance the effect of the oligonucleotides on the suppression of tumor necrosis factor (TNF)-alpha and prolong the active time of the antisense drug in vivo. The protective and therapeutic effect of ASO/GLC in the animal model of D-galactosamine/lipopolysaccharide-induced fulminant hepatitis was tested.

RESULTS

ASOs delivered by GLC were concentrated in Kupffer cells and more potent in reducing the expression of TNF-alpha mRNA, as well as reducing serum TNF-alpha levels. Furthermore, the ASO/GLC complex successfully rescued animals from fulminant hepatitis and mortality. Compared to naked ASO, the complex notably reduced the dose administrated in animals and prolonged its effectiveness. A single dose of 5 mg ASO per kg body weight achieved a satisfactory effect after 5 days, and 20 mg ASO per kg body weight preserved 70% of the effect after more than 2 weeks. Its efficacy was affirmed through both pretreatment and therapeutic use after liver damage had begun.

CONCLUSIONS

Inhibiting TNF-alpha expression in the liver by this strategy represents a novel therapeutic approach that may be valuable for the treatment of some inflammation-related liver diseases.

Oligonucleotides derived from the packaging signal at the 5' end of the viral PB2 segment specifically inhibit influenza virus in vitro

The development of new antiviral molecules to fight the possible emergence of influenza viruses with pandemic potential is needed. In this study, phosphorothioate oligonucleotides (S-ONs) derived from the packaging signals in the 3' and 5' ends of the viral PB2 RNA were associated with liposomes and tested against influenza virus in vitro. A 15-mer S-ON derived from the 5' end of the viral PB2 RNA, complementary to the 3' end of its coding region (nucleotides 2279-2293) and designated 5-15b, proved markedly inhibitory. The antiviral activity of 5-15b was dose- and time-dependent but was independent of the cell substrate and multiplicity of infection used. Importantly, inhibition of influenza A and B viruses required S-ONs reproducing the respective packaging signals. Furthermore, 5-15b and its antisense derivative S-ON activity did not affect intracellular accumulation of viral RNA. Confocal microscopy showed that 5-15b is clearly nucleophilic. These findings indicate that the packaging signal at the 5' end of the PB2 RNA is an interesting target for the design of new anti-influenza-virus compounds.

Oligonucleotide antiviral therapeutics: antisense and RNA interference for highly pathogenic RNA viruses

RNA viruses are a significant source of morbidity and mortality in humans every year. Additionally, the potential use of these viruses in acts of bioterrorism poses a threat to national security. Given the paucity of vaccines or postexposure therapeutics for many highly pathogenic RNA viruses, novel treatments are badly needed. Sequence-based drug design, under development for almost 20 years, is proving effective in animal models and has moved into clinical trials. Important advances in the field include the characterization of RNA interference in mammalian cells and chemical modifications that can dramatically increase the in vivo stability of therapeutic oligonucleotides. Antisense strategies utilize single-stranded DNA oligonucleotides that inhibit protein production by mediating the catalytic degradation of target mRNA, or by binding to sites on mRNA essential for translation. Double-stranded RNA oligonucleotides, known as short-interfering RNAs (siRNAs), also mediate the catalytic degradation of complementary mRNAs. As RNA virus infection is predicated on the delivery, replication, and translation of viral RNA, these pathogens present an obvious target for the rapidly advancing field of sequence-specific therapeutics. Antisense oligonucleotides or siRNAs can be designed to target the viral RNA genome or viral transcripts. This article reviews current knowledge on therapeutic applications of antisense and RNA interference for highly pathogenic RNA viral infections.

Anti-influenza virus agents: synthesis and mode of action

Annual epidemics of influenza virus infection are responsible for considerable morbidity and mortality, and pandemics are much more devastating. Considerable knowledge of viral infectivity and replication has been acquired, but many details still have to be elucidated and the virus remains a challenging target for drug design and development. This review provides an overview of the antiviral drugs targeting the influenza viral replicative cycle. Included are a brief description of their chemical syntheses and biological activities. For other reviews, see References1-9.

Inhibition of highly pathogenic avian H5N1 influenza virus replication by RNA oligonucleotides targeting NS1 gene

H5N1 avian influenza virus (AIV) has caused widespread infections in poultry and wild birds, and has the potential to emerge as a pandemic threat to human. In order to explore novel approaches to inhibiting highly pathogenic H5N1 influenza virus infection, we have developed short RNA oligonucleotides, specific for conserved regions of the non-structural protein gene (NS1) of AIV. In vitro the hemagglutination (HA) titers in RNA oligonucleotide-treated cells were at least 5-fold lower than that of the control. In vivo, the treatment with three doses of RNA oligonucleotides protected the infected chickens from H5N1 virus-induced death at a rate of up to 87.5%. Plaque assay and real-time PCR analysis showed a significant reduction of the PFU and viral RNA level in the lung tissues of the infected animals treated with the mixed RNA oligonucleotides targeting the NS1 gene. Together, our findings revealed that the RNA oligonucleotides targeting at the AIV NS1 gene could potently inhibit avian H5N1 influenza virus reproduction and present a rationale for the further development of the RNA oligonucleotides as prophylaxis and therapy for highly pathogenic H5N1 influenza virus infection in humans.

Coxsackievirus-induced myocarditis: new trends in treatment

Myocarditis is a common inflammatory heart disease in children and young adults that may result in chronically dilated cardiomyopathy. Coxsackievirus B3 is the major etiologic agent of this disease. Current treatments for patients with viral myocarditis are almost entirely supportive. In recent years, some promising therapeutic candidates have emerged, including novel treatments and improvements of existing drugs. Among these are molecules that specially target virus entry, such as pleconaril, WIN 54954 and CAR-Fc; nucleic acid-based antiviral agents that inhibit viral translation and/or transcription, such as antisense oligodeoxynucleotide and short interfering RNA; and immunomodulatory agents that augment the host-protective immune responses to effectively clear viruses from target tissues, including interferons and immunoglobulins. In addition, certain new antiviral strategies, still in the early stages, include modulation of signal transduction pathways responsible for viral replication using enzyme inhibitors, which have revealed potential therapeutic targets for viral myocarditis. Finally, the progress in cellular cardiomyoplasty for end-stage therapy, in particular the preliminary clinical trials, is also discussed with respect to its potential future application.

Inhibition of multiple subtypes of influenza A virus in cell cultures with morpholino oligomers

Peptide-conjugated phosphorodiamidate morpholino oligomers (P-PMO) are single-stranded nucleic acid-like antisense agents that can reduce gene expression by sterically blocking complementary RNA sequence. P-PMO are water soluble and nuclease resistant, and they readily achieve uptake into cells in culture under standard conditions. Eight P-PMO, each 20 to 22 bases in length, were evaluated for their ability to inhibit influenza A virus (FLUAV) A/PR/8/34 (H1N1) replication in cell culture. The P-PMO were designed to base pair with FLUAV RNA sequences that are highly conserved across viral subtypes and considered critical to the FLUAV biological-cycle, such as gene segment termini and mRNA translation start site regions. Several P-PMO were highly efficacious, each reducing viral titer in a dose-responsive and sequence-specific manner in A/PR/8/34-infected cells. Two P-PMO, one designed to target the AUG translation start site region of PB1 mRNA and the other the 3'-terminal region of nucleoprotein viral genome RNA, also proved to be potent against several other FLUAV strains, including A/WSN/33 (H1N1), A/Memphis/8/88 (H3N2), A/Eq/Miami/63 (H3N8), A/Eq/Prague/56 (H7N7), and the highly pathogenic A/Thailand/1(KAN-1)/04 (H5N1). The P-PMO exhibited minimal cytotoxicity in cell viability assays. High efficacy by two of the P-PMO against multiple FLUAV subtypes suggests that these oligomers represent a broad-spectrum therapeutic approach against a high percentage of known FLUAV strains.

Gene silencing of virus replication by RNA interference

Small interfering RNAs (siRNAs) are as effective as long double-stranded RNAs (dsRNAs) at targeting and silencing genes by RNA interference (RNAi). siRNAs are widely used for assessing gene function in cultured mammalian cells or early developing vertebrate embryos. They are also promising reagents for developing gene-specific therapeutics. The specific inhibition of viral replication is particularly well suited to RNAi, as several stages of the viral life cycle and many viral and cellular genes can be targeted. The future success of this approach will depend on the recent advances in siRNA-based clinical trials.

Antisense downregulation of SARS-CoV gene expression in Vero E6 cells

Background

Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus (SARS‐CoV). It is an enveloped, single‐stranded, plus‐sense RNA virus with a genome of ∼30 kb. The structural proteins E, M and N of SARS‐CoV play important roles during host cell entry and viral morphogenesis and release. Therefore, we have studied whether expression of these structural proteins can be down‐regulated using an antisense technique.

Methods

Vero E6 cells were transfected with plasmid constructs containing exons of the SARS‐CoV structural protein E, M or N genes or their exons in frame with the reporter protein EGFP. The transfected cell cultures were treated with antisense phosphorothioated oligonucleotides (antisense PS‐ODN, 20mer) or a control oligonucleotide by addition to the culture medium.

Results

Among a total of 26 antisense PS‐ODNs targeting E, M and N genes, we obtained six antisense PS‐ODNs which could sequence‐specifically reduce target genes expression by over 90% at the concentration of 50 µM in the cell culture medium tested by RT‐PCR. The antisense effect was further proved by down‐regulating the expression of the fusion proteins containing the structural proteins E, M or N in frame with the reporter protein EGFP. In Vero E6 cells, the antisense effect was dependent on the concentrations of the antisense PS‐ODNs in a range of 0–10 µM or 0–30 µM.

Conclusions

The antisense PS‐ODNs are effective in downregulation of SARS. The findings indicate that antisense knockdown of SARS could be a useful strategy for treatment of SARS, and could also be suitable for studies of the pathological function of SARS genes in a cellular model system. Copyright © 2004 John Wiley & Sons, Ltd.

Inhibition of Staphylococcus aureus gene expression and growth using antisense peptide nucleic acids

Gene function studies in bacteria lag behind progress in genome sequencing, in part because current reverse genetics technology based on genome disruption does not allow subtle control of gene expression for all genes in a range of species. Essential genes and clustered regions are particularly problematic. Antisense technology offers an attractive alternative for microbial genomics. Unfortunately, bacteria lack RNAi mechanisms and conventional oligonucleotides are not taken up efficiently. However, in Escherichia coli, efficient and gene-specific antisense knock down is possible using antisense peptide nucleic acids (PNAs) attached to carrier peptides (KFFKFFKFFK). Carrier peptides can enter a range of microbial species, and in this study we asked whether peptide-PNAs could mediate antisense effects in Staphylococcus aureus. Using low micromolar concentrations we observed dose- and sequence-dependent inhibition of the reporter gene gfp and endogenous gene phoB. Also, antisense peptide-PNAs targeted to the essential genes fmhB, gyrA, and hmrB were growth inhibitory. Control peptide-PNAs were much less effective, and sequence alterations within the PNA and target mRNA sequences reduced or eliminated inhibition. Further development is needed to raise the antibacterial potential of PNAs, but the present results show that the approach can be used to study gene function and requirement in this important pathogen.

Resistance to influenza A virus infection by antigen-conjugated CpG oligonucleotides, a novel antigen-specific immunomodulator

Oligodeoxynucleotides (ODN) containing CpG motifs (CpG) act as modulators that bias the immune response towards a Th1-dominant phenotype. To investigate this effect further, we examined the protective effects of a covalently linked conjugate between CpG-ODN and HA-2kd antigen in mice infected with influenza A virus. The conjugated form of CpG-ODN and HA-2kd was more efficient in regulating influenza A virus than the unconjugated mixture of CpG-ODN and HA-2kd. The antigen-conjugated CpG-ODN induced an immune response with a Th1-dominant cytokine pattern characterized by the secretion of high levels of HA-2kd-specific interferon-gamma and IgG2a (Th1), which were only slightly induced by HA-2kd alone. These findings support the use of CpG-ODN-Ag conjugates as novel Ag-specific immunomodulators and suggest that CpG-ODN-HA-2kd might be a promising immune therapy for patients with influenza virus.

In vitro and in vivo transport and delivery of phosphorothioate oligonucleotides with cationic liposomes

A recent strategy in gene therapy has been using antiviral genes that are delivered to uninfected cells, either as RNA or DNA, to provide intracellular protection from human immunodeficiency virus type-1 (HIV-1) infection. Antisense oligonucleotides that are complementary to specific target genes suppress gene expression. A variety of techniques are available to enhance the cellular uptake and pharmacological effectiveness of antisense oligonucleotides, both in vitro and in vivo. We investigated the intracellular and tissue uptake of an oligonucleotide/cationic lipid complex, using a fluorescently labeled oligonucleotide. The antisense oligonucleotide was designed against the HIV-1 gag gene sequence. A T-cell line (MT-4) and PHA-stimulated peripheral blood mononuclear cells (PBMCs) were both infected with HIV-1(NL432) at an MOI of 0.01. One h later, both cultures were washed and treated with medium containing 1 microM antisense oligonucleotide. After a 3-day interval, the HIV-1 antigen expression was monitored by an indirect immunofluorescence assay. At 3 days post infection, we confirmed that p24 antigen production was inhibited by the antisense oligonucleotide/cationic lipid complex at a 1/10 ratio in the PBMCs, using enzyme-linked immunosorbent assay (ELISA). We also confirmed the intracellular existence of the complex by fluorescent microscopy. We investigated different means of transporting the antisense oligonucleotide/cationic lipid complex to mouse tissues by intravenous, intraperitoneal and subcutaneous injections. We observed that the anti-HIV-1 activity of the antisense oligonucleotide/cationic lipid complex was the result of enhanced cellular uptake, both in vitro and in vivo. Therefore, the antisense oligonucleotide/cationic lipid complex is an excellent system for the transport and delivery of genes to target cells, as it is effective both in vitro and in vivo.

Antisense morpholino-oligomers directed against the 5' end of the genome inhibit coronavirus proliferation and growth

Conjugation of a peptide related to the human immunodeficiency virus type 1 Tat represents a novel method for delivery of antisense morpholino-oligomers. Conjugated and unconjugated oligomers were tested to determine sequence-specific antiviral efficacy against a member of the Coronaviridae, Mouse hepatitis virus (MHV). Specific antisense activity designed to block translation of the viral replicase polyprotein was first confirmed by reduction of luciferase expression from a target sequence-containing reporter construct in both cell-free and transfected cell culture assays. Peptide-conjugated morpholino-oligomers exhibited low toxicity in DBT astrocytoma cells used for culturing MHV. Oligomer administered at micromolar concentrations was delivered to >80% of cells and inhibited virus titers 10- to 100-fold in a sequence-specific and dose-responsive manner. In addition, targeted viral protein synthesis, plaque diameter, and cytopathic effect were significantly reduced. Inhibition of virus infectivity by peptide-conjugated morpholino was comparable to the antiviral activity of the aminoglycoside hygromycin B used at a concentration fivefold higher than the oligomer. These results suggest that this composition of antisense compound has therapeutic potential for control of coronavirus infection.

A phosphorothioate antisense oligodeoxynucleotide specifically inhibits coxsackievirus B3 replication in cardiomyocytes and mouse hearts

Antisense oligodeoxynucleotides (AS-ODNs) are promising therapeutic agents for the treatment of virus-induced diseases. We previously reported that coxsackievirus B3 (CVB3) infectivity could be inhibited effectively in HeLa cells by phosphorothioate AS-ODNs complementary to different regions of the 5' and 3' untranslated regions of CVB3 RNA. The most effective target is the proximal terminus of the 3' untranslated region. To further investigate the potential antiviral role of the AS-ODN targeting this site in cardiomyocytes (HL-1 cell line), corresponding AS-ODN (AS-7) was transfected into the HL-1 cells and followed by CVB3 infection. Analyses by RT-PCR, Western blotting and plaque assay demonstrated that AS-7 strongly inhibits viral RNA and viral protein synthesis as compared to scrambled AS-ODNs. The percent inhibitions of viral RNA transcription and capsid protein VP1 synthesis were 87.6 and 40.1, respectively. Moreover, AS-7 could inhibit ongoing CVB3 infection when it was given after virus infection. The antiviral activity was further evaluated in a CVB3 myocarditis mouse model. Adolescent A/J mice were intravenously administrated with AS-7 or scrambled AS-ODNs prior to and after CVB3 infection. Following a 4-day therapy, the myocardium CVB3 RNA replication decreased by 68% and the viral titers decreased by 0.5 log(10) in the AS-7-treated group as compared to the group treated with the scrambled AS-ODNs as determined by RT-PCR, in situ hybridization and viral plaque assay. Taken together, our results demonstrated a great potential for AS-7 to be further developed into an effective treatment towards viral myocarditis as well as other diseases caused by CVB3 infection.

A new modified DNA enzyme that targets influenza virus A mRNA inhibits viral infection in cultured cells

DNA enzymes are RNA-cleaving single-stranded DNA molecules. We designed DNA enzymes targeting the PB2 mRNA translation initiation (AUG) region of the influenza A virus (A/PR/8/34). The modified DNA enzymes have one or two N3'-P5' phosphoramidate bonds at both the 3'- and 5'-termini of the oligonucleotides, which significantly enhanced their nuclease resistance. These modified DNA enzymes had the same cleavage activity as the unmodified DNA enzymes, determined by kinetic analyses, and reduced influenza A virus replication by more than 99%, determined by plaque formation. These DNA enzymes are highly specific; their protective effect was not observed in influenza B virus (B/Ibaraki)-infected Madin-Darby canine kidney cells.

Antisense treatment against Ki-67 mRNA inhibits proliferation and tumor growth in vitro and in vivo

The Ki-67 protein is tightly regulated and depends on the proliferative status of a cell. It is present in the nuclei of proliferating cells but absent in resting cells. Since transformation of malignant cells is frequently associated with high cell proliferation and since proliferation is tightly associated with the Ki-67 protein labeling index, this antigen may represent a potential target for cancer therapy. In the present study we determined the ability of a phosphorothioate antisense oligodeoxyribonucleotide (ODN) targeted against Ki-67 mRNA to inhibit tumor cell proliferation specifically in cell culture, in multicellular 3-dimensional spheroids (MCS) and in subcutaneous murine tumor models. Antisense treatment of 1 myeloid and different epithelial tumor cell lines in suspension and monolayer culture, respectively, resulted in specific reduction of Ki-67 mRNA and protein, inhibition of proliferation and increased apoptotic cell death. Multicellular human bladder carcinoma spheroids lost their 3-dimensional structure and underwent cell death after incubation with antisense oligonucleotides. The growth of subcutaneous syngeneic prostatic (p = 0.05) and transitional cell tumors (p = 0.001) in immunocompetent mice was significantly inhibited in antisense-treated animals. From these findings we conclude that antisense inhibition of Ki-67 protein expression may be a rational approach in anticancer therapy.

Glutathione-sensitive stabilization of block copolymer micelles composed of antisense DNA and thiolated poly(ethylene glycol)-block-poly(L-lysine): a potential carrier for systemic delivery of antisense DNA

Glutathione (GSH)-sensitive stabilization of polyion complex (PIC) micelles entrapping antisense oligonucleotide (ODN) was achieved by the reversible cross-linking of the core through disulfide bonds, aiming at the development of a novel DNA carrier system for antisense therapy following systemic administration. Thiolated poly(ethylene glycol)-block-poly(L-lysine) (PEG-thioPLL) and ODN spontaneously associated to form the PIC micelles with the core cross-linked through disulfide bonds. The diameters of the cross-linked micelles were similar to those of the non-cross-linked micelles and were determined to be about 40 nm by light scattering measurements. The micelles have sufficient colloidal stability due to the PEG shell surrounding the core of the polyion complex composed of PLL and ODN. The polyanion exchange studies suggested that the dissociation of the micelles was suppressed through the core cross-linking. The stability of the ODN in the core cross-linked micelles against nuclease was appreciably increased compared to that of free ODN and that in the micelles without cross-linking. On the other hand, the micelles dissociated to release ODN in the presence of GSH at a concentration comparable to the intracellular environment, featuring the potential ability of this system for intracellular ODN delivery.

Inhibition of human immunodeficiency virus type 1 replication by P-stereodefined oligo(nucleoside phosphorothioate)s in a long-term infection model

Oligo(nucleoside phosphorothioate)s (S-ODNs), if prepared by conventional methods, consist of a mixture of diastereomers by virtue of the asymmetry of the phosphorus atom involved in the internucleotide linkages. This may affect the stability of the complexes formed between S-ODNs and complementary oligoribonucleotides, which is commonly accepted as the most important factor in determining the efficacy of an antisense approach. Using HIV-1-infected MOLT-4 cells via a long-term culture approach, we studied the influence of the P-chirality sense of stereodefined 28mer oligo(nucleoside phosphorothioate)s, [All-Rp]-S-ODN-gag-28-AUG and [All-Sp]-S-ODN-gag-28-AUG, complementary to the sequence starting at the AUG initiation codon of the gag mRNA of HIV-1, upon the anti-HIV-1 activity. The [All-Sp]-S-ODN-gag-28-AUG at a low concentration of 0.5 microM can completely suppress HIV-1(gag) p24 antigen expression in HIV-1-infected MOLT-4 clone 8 cells for 32 days. Cells treated with [All-Rp]-S-ODN-gag-28-AUG (0.5 microM) showed a high level of the antigen expression at day 16. Furthermore, satisfactory suppression could not be achieved from a random [Mix]-S-ODN-gag-28-AUG, consisting of a diastereomeric mixture of the oligonucleotides. Our results suggest that chemotherapy based upon the use of stereodefined antisense [All-Sp] S-ODN may be a more effective method for reducing the viral burden in HIV-1-infected individuals.

Genomic analysis using conditional phenotypes generated by antisense RNA

Antisense technology has been widely used to regulate gene expression. A tetracycline (tet)-regulated antisense-RNA-expressing system has been developed and used to downregulate chromosomally derived genes expressed in Staphylococcus aureus. This downregulation subsequently provides an evaluation of the virulence factor and drug targets. The regulated antisense RNA library allows for genome-wide analyses of the functions of staphylococcal gene products for growth in culture and survival during infection. Moreover, this antisense RNA technology may provide a key tool to identify mechanisms of novel antibacterial compound action.

Inhibition of Vesivirus infections in mammalian tissue culture with antisense morpholino oligomers

Caliciviruses infect and cause disease in animals and humans. They are nonenveloped, positive-stranded RNA viruses with a genome of approximately 7.5 kb that encodes viral proteins in three open reading frames (ORF). Antisense oligomers targeting one of the three ORF of caliciviruses of the genus Vesivirus significantly inhibit viral replication in tissue culture. Porcine kidney and African green monkey kidney cells were infected with Vesivirus isolates SMSV-13 and PCV Pan-1. Phosphorodiamidate morpholino oligomers (PMO) with sequence complementary to the AUG translation start site regions of ORF1, ORF2, and ORF3 were evaluated for their effect on viral titer. Scrape-loading delivered PMO to 50%-70% of the cells of the two cell lines, as measured by fluorescence microscopy and flow cytometry. A PMO targeting ORF3 caused a significant increase in viral titer. A PMO targeting ORF2, a scrambled PMO control sequence, and an unrelated PMO antisense sequence did not alter viral titer. Various PMO sequences antisense to an upstream region of ORF1 were effective in reducing viral titer up to 80% in a dose-dependent and sequence-specific manner. The extent of viral titer reduction was proportional to the delivery of PMO to cells. These observations demonstrate that antisense PMO can disrupt caliciviral gene function in a nucleic acid sequence-specific manner and are potentially effective antiviral agents.

Identification of critical staphylococcal genes using conditional phenotypes generated by antisense RNA

Comprehensive genomic analysis of the important human pathogen Staphylococcus aureus was achieved by a strategy involving antisense technology in a regulatable gene expression system. In addition to known essential genes, many genes of unknown or poorly defined biological function were identified. This methodology allowed gene function to be characterized in a comprehensive, defined set of conditionally growth-defective/lethal isogenic strains. Quantitative titration of the conditional growth effect was performed either in bacterial culture or in an animal model of infection. This genomic strategy offers an approach to the identification of staphylococcal gene products that could serve as targets for antibiotic discovery.

Anti-influenza drugs and neuraminidase inhibitors

Each year, influenza viruses are responsible for considerable illness, complications and mortality. An effective treatment will have a major impact on the severe personal and economic burden that this disease incurs. There are several points in the influenza life cycle that may be potentially inhibited. One critical point is the release of newly synthesized virions from the host cell surface. Viral neuraminidase (NA) cleaves the virus from host cell sialic acid residues allowing infection of other host cells. Rationally designed NA inhibitors that block the viral life cycle are now in the clinic and these molecules are effective and safe for the treatment of influenza. Compared with other anti-influenza agents the NA inhibitors are well tolerated, effective against all influenza types and there has been little evidence of the emergence of viral resistance. NA inhibitors provide an important new therapeutic weapon for the management of influenza infection.

Prophylaxis and treatment of influenza virus infection

Influenza virus infections remain an important cause of morbidity and mortality. Furthermore, a recurrence of pandemic influenza remains a real possibility. There are now effective ways to both prevent and treat influenza. Prevention of infection is most effectively accomplished by vaccination. Vaccination with the inactivated, intramuscular influenza vaccine has been clearly demonstrated to reduce serious morbidity and mortality associated with influenza infection, especially in groups of patients at high risk (e.g. the elderly). However, the inactivated, intramuscular vaccine does not strongly induce cell-mediated or mucosal immune responses, and protection induced by the vaccine is highly strain specific. Live, attenuated influenza vaccines administered intranasally have been studied in clinical trials and shown to elicit stronger mucosal and cell-mediated immune responses. Live, attenuated vaccines appear to be more effective for inducing protective immunity in children or the elderly than inactivated, intramuscular vaccines. Additionally, novel vaccine methodologies employing conserved components of influenza virus or viral DNA are being developed. Preclinical studies suggest that these approaches may lead to methods of vaccination that could induce immunity against diverse strains or subtypes of influenza. Because of the limitations of vaccination, antiviral therapy continues to play an important role in the control of influenza. Two major classes of antivirals have demonstrated ability to prevent or treat influenza in clinical trials: the adamantanes and the neuraminidase inhibitors. The adamantanes (amantadine and rimantadine) have been in use for many years. They inhibit viral uncoating by blocking the proton channel activity of the influenza A viral M2 protein. Limitations of the adamantanes include lack of activity against influenza B, toxicity (especially in the elderly), and the rapid development of resistance. The neuraminidase inhibitors were designed to interfere with the conserved sialic acid binding site of the viral neuraminidase and act against both influenza A and B with a high degree of specificity when administered by the oral (oseltamivir) or inhaled (zanamivir) route. The neuraminidase inhibitors have relatively low toxicity, and viral resistance to these inhibitors appears to be uncommon. Additional novel antivirals that target other phases of the life cycle of influenza are in preclinical development. For example, recombinant collectins inhibit replication of influenza by binding to the viral haemagglutinin as well as altering phagocyte responses to the virus. Recombinant techniques have been used for generation of antiviral proteins (e.g. modified collectins) or oligonucleotides. Greater understanding of the biology of influenza viruses has already resulted in significant advances in the management of this important pathogen. Further advances in vaccination and antiviral therapy of influenza should remain a high priority.

Anti-influenza drugs and neuraminidase inhibitors

Each year, influenza viruses are responsible for considerable illness, complications and mortality. An effective treatment will have a major impact on the severe personal and economic burden that this disease incurs. There are several points in the influenza life cycle that may be potentially inhibited. One critical point is the release of newly synthesized virions from the host cell surface. Viral neuraminidase (NA) cleaves the virus from host cell sialic acid residues allowing infection of other host cells. Rationally designed NA inhibitors that block the viral life cycle are now in the clinic and these molecules are effective and safe for the treatment of influenza. Compared with other anti-influenza agents the NA inhibitors are well tolerated, effective against all influenza types and there has been little evidence of the emergence of viral resistance. NA inhibitors provide an important new therapeutic weapon for the management of influenza infection.

Inhibition of hepadnaviral replication by polyethylenimine-based intravenous delivery of antisense phosphodiester oligodeoxynucleotides to the liver

Antisense oligodeoxynucleotides (ODNs) appear as attractive anti-hepatitis B virus (HBV) agents. We investigated in vivo, in the duck HBV (DHBV) infection model, whether linear polyethylenimine (lPEI)-based intravenous delivery of the natural antisense phosphodiester ODNs (O-ODNs) can prevent their degradation and allow viral replication inhibition in the liver. DHBV-infected Pekin ducklings were injected with antisense O-ODNs covering the initiation codon of the DHBV large envelope protein, either in free form (O-ODN-AS2) or coupled to lPEI (lPEI/O-ODN-AS2). Following optimization of lPEI/O-ODN complex formulation, complete O-ODN condensation into a homogenous population of small (20-60 nm) spherical particles was achieved. Flow cytometry analysis showed that lPEI-mediated transfer allowed the intrahepatic delivery of lPEI/O-ODN-AS2 to increase three-fold as compared with the O-ODN-AS2. Following 9-day therapy the intrahepatic levels of both DHBV DNA and RNA were significantly decreased in the lPEI/O-ODN-AS2-treated group as compared with the O-ODN-AS2-treated, control lPEI/O-ODN-treated, and untreated controls. In addition, inhibition of intrahepatic viral replication by lPEI/O-ODN-AS2 was not associated with toxicity and was comparable with that induced by the phosphorothioate S-ODN-AS2 at a five-fold higher dose. Taken together, our results demonstrate that phosphodiester antisense lPEI/O-ODN complexes specifically inhibit hepadnaviral replication. Therefore we provide here the first in vivo evidence that intravenous treatment with antisense phosphodiester ODNs coupled to lPEI can selectively block a viral disease-causing gene in the liver.

Antisense therapy of influenza

The liposomally encapsulated and the free antisense phosphorothioate oligonucleotides (S-ODNs) with four target sites (PB1, PB2, PA, and NP) were tested for their abilities to inhibit virus-induced cytopathogenic effects by a MTT assay using MDCK cells. The liposomally encapsulated S-ODN complementary to the sites of the PB2-AUG initiation codon showed highly inhibitory effects. On the other hand, the inhibitory effect of the liposomally encapsulated S-ODN targeted to PB1 was considerably decreased in comparison with those directed to the PB2 target sites. The liposomally encapsulated antisense phosphorothioate oligonucleotides exhibited higher inhibitory activities than the free oligonucleotides, and showed sequence-specific inhibition, whereas the free antisense phosphorothioate oligonucleotides were observed to inhibit viral absorption to MDCK cells. Therefore, the antiviral effects of S-ODN-PB2-AUG and PA-AUG were examined in a mouse model of influenza virus A infection. Balb/c mice exposed to the influenza virus A (A/PR/8/34) strain at dose of 100 LD(50)s were treated i.v. with various doses (5-40 mg/kg) of liposomally (Tfx-10) encapsulated PB2-AUG or PA-AUG before virus infection and 1 and 3 days postinfection. PB2-AUG oligomer treated i.v. significantly prolonged the mean survival time in days (MDS) and increased the survival rates with a dose-dependent manner. We demonstrate the first successful in vivo antiviral activity of antisense administered i.v. in experimental respiratory tract infections induced with influenza virus A.

Inhibitory effects of an antisense oligonucleotide in an experimentally infected mouse model of influenza A virus

The antiviral effects of a 20-mer antisense phosphorothioate oligonucleotide, PB2-as, on influenza A virus infection in mice were examined and compared to those of PB2-as encapsulated with several cationic liposomes. Intravenous injection of PB2-as, as a complex with DMRIE-C, a cationic liposome, was most effective for prolonging the mean survival time in days (MSDs) and increasing the survival rates of mice infected with the influenza A virus. In addition, the liposomal PB2-as significantly inhibited viral growth in lung tissues. These results suggest that PB2-as encapsulated with DMRIE-C may be active against the influenza A virus infection through the inhibition of virus replication in the mouse lung.

Chemically modified ribozyme to V gene inhibits anti-DNA production and the formation of immune deposits caused by lupus lymphocytes

A variety of autoantibodies is responsible for the tissue injury in autoimmune diseases. We have demonstrated that the human anti-DNA Ab O-81, of which Ids are commonly detected in renal glomeruli of active lupus nephritis, uses the V3-7 gene. We tried to develop a new therapy for lupus nephritis by using chemically modified ribozymes to specifically inhibit the expression of the mRNA of Ig V gene. The transfection of hammerhead ribozyme or the addition of chemically modified ribozyme against the flanking region of V3-7 caused a potent and selective inhibition of anti-DNA production in V3-7-using B cell clones, but not in irrelevant V gene-using clones in vitro. Chemically modified ribozyme was long-acting and resistant to RNase, and nonspecific cytotoxicity of the ribozyme was negligible. To know the efficacy of the ribozyme in vivo, we used a model of immune complex nephritis in SCID mice in which 5 x 10(6) PBLs from patients with active lupus nephritis (lupus PBL) were transferred twice. The injection of lupus PBL in combination with chemically modified ribozyme to increase resistance to RNase significantly reduced anti-DNA Ab levels in blood and decreased levels of urinary protein in the immune deposit models. Immunofluorescence study also revealed a marked decrease in IgG deposits at renal glomeruli in the ribozyme-treated group. These results indicate an efficacy of chemically modified ribozyme therapy for autoantibody-mediated immune diseases.

Antisense imaging: where are we now?

The field of antisense targeting is changing rapidly as additional results from in vitro studies and animal and patient trials become available. While these developments apply primarily to antisense chemotherapy, many have implications for antisense imaging and radiotherapy. It may now be profitable to reconsider antisense imaging in the light of these recent developments. With the benefit of further insight, it may be possible to predict which antisense mechanisms will be preferable for antisense imaging. It is also possible to consider the influences of carriers (vectors) on the targeting of antisense DNA and whether this might improve imaging. Furthermore, estimates showing only low mRNA steady-state copy numbers per cell may be reconsidered in refining predictions of tissue counting rates. Finally, recent results suggest that radiolabeling antisense DNAs may not adversely influence the targeting properties of antisense DNAs.

Inhibition of influenza virus replication in cultured cells by RNA-cleaving DNA enzyme

Influenza virus replication has been effectively inhibited by antisense phosphothioate oligonucleotides targeting the AUG initiation codon of PB2 mRNA. We designed RNA-cleaving DNA enzymes from 10-23 catalytic motif to target PB2-AUG initiation codon and measured their RNA-cleaving activity in vitro. Although the RNA-cleaving activity was not optimal under physiological conditions, DNA enzymes inhibited viral replication in cultured cells more effectively than antisense phosphothioate oligonucleotides. Our data indicated that DNA enzymes could be useful for the control of viral infection.

Reduction of liver Fas expression by an antisense oligonucleotide protects mice from fulminant hepatitis

Aberrant apoptosis-mediated cell death is believed to result in a number of different human diseases. For example, excessive apoptosis in the liver can result in fulminant and autoimmune forms of hepatitis. We have explored the possibility that inhibition of Fas expression in mice would reduce the severity of fulminant hepatitis. To do this, we have developed a chemically modified 2'-O-(2-methoxy)ethyl antisense oligonucleotide (ISIS 22023) inhibitor of mouse Fas expression. In tissue culture, this oligonucleotide induced a reduction in Fas mRNA expression that was both concentration- and sequence-specific. In Balb/c mice, dosing with ISIS 22023 reduced Fas mRNA and protein expressions in liver by 90%. The ID50 for this response was 8-10 mg kg-1 daily dosing, and the reduction was highly dependent on oligonucleotide sequence, oligonucleotide concentration in liver, and treatment time. Pretreatment with ISIS 22023 completely protected mice from fulminant hepatitis induced by agonistic Fas antibody, by a mechanism entirely consistent with an oligonucleotide antisense mechanism of action. In addition, oligonucleotide-mediated suppression of Fas expression reduced the severity of acetaminophen-mediated fulminant hepatitis, but was without effect on concanavalin A-mediated hepatitis. Our results demonstrate that 2'-O-(2-methoxy)ethyl containing antisense oligonucleotides targeting Fas can exert in vivo pharmacological activity in liver, and suggest that oligonucleotide inhibitors of Fas may be useful in the treatment of human liver disease.

Vaccines and therapeutics against influenza virus infections

BACKGROUND

Vaccination prior to epidemic season is the best measure to control influenza virus infection; however, there are several issues to be considered regarding influenza vaccines in Japan. In the present review, current issues regarding influenza vaccine in Japan are described, as well as the future prospects of vaccine development. As well as vaccination, anti-influenza agents such as amantadine are now available in Japan. Furthermore, neuraminidase inhibitors are expected to appear in the market in near future. These anti-influenza agents represent new options for influenza control.

CONCLUSIONS

Vaccination and antiviral agents are a major armamentarium against influenza infections. Thus, exploratory studies on novel forms of vaccine and anti-influenza drugs should help to prepare against pandemics that must emerge in near future.

Treatment of experimental autoimmune encephalomyelitis with antisense oligonucleotides against the low affinity neurotrophin receptor

Upregulated expression of the low-affinity neurotrophin receptor (p75) in the central nervous system (CNS) during experimental autoimmune encephalomyelitis (EAE) has recently been demonstrated. To investigate whether p75 plays a role in disease pathogenesis, we adopted a gene therapy approach, utilizing antisense oligonucleotides to downregulate p75 expression during EAE. Phosphorothioate antisense oligonucleotides (AS), nonsense oligonucleotides (NS) or phosphate buffered saline (PBS) were injected daily for 18 days after immunization of SJL/J (H-2s)-mice with myelin proteolipid protein (PLP) peptide 139-151. In the AS group, there was a statistically significant reduction in both the mean maximal disease score (1.85 in the AS, 2.94 in the NS and 2.75 in the PBS-groups, respectively, P < 0.025) and in the cumulative disease incidence ( approximately 60% in the AS group and approximately 90% in the control groups). Histological and immunohistochemical analysis showed reduced inflammation and demyelination, as well as reduced p75 expression at the blood-brain barrier (BBB) in the AS-treated mice in comparison with both control groups. There was no difference, however, in p75 expression on neural cells within the CNS between the three groups of mice. We conclude that p75 could play a proactive role in the pathogenesis of EAE and may exert its effect at the level of the BBB.

Recent progress in anti-influenza chemotherapy

Influenza virus infections in high risk individuals, such as infants, the elderly, and patients with cardiopulmonary disorders or immunocompromised states, cause severe manifestations which often result in fatalities. The emergence of a new antigen type of influenza A virus (H5N1) in Hong Kong during 1997 and 1998 threatened a possible pandemic of a new influenza infection. The investigation for anti-influenza chemotherapies has progressed in the last decade whereas clinical trials of new compounds have been limited to amantadine, rimantadine and ribavirin. Fusion inhibitors which directly inhibit conformational change of haemagglutinin (HA), protease inhibitors which inhibit cleavage of HA to HA1 and HA2, RNA transcription inhibitors which inhibit cap formation of mRNA and antisense oligonucleotides targeted at mRNA of PB2 (a part of viral RNA polymerase) have been reported, in their development phases. Recently, 2 neuraminidase (NA) inhibitors, zanamivir and oseltamivir (GS 4104), were used in clinical trials for the treatment of patients with influenza. Both agents showed promising results. A polyoxometalate, PM-523, inhibits fusion between the virus envelope and cell membrane and inhibits the penetration of the virus into cells. This compound has shown potent anti-influenza activity and synergistic inhibitory activity in combination with ribavirin or zanamivir in vitro and in vivo. Resistant strains for zanamivir, oseltamivir or PM-523 have been isolated. The analysis of mutation points of these strains have contributed to the investigation of the antiviral mechanisms of action of these compounds and the mechanism of resistance of the mutants to these compounds.