RNA interference therapy in lung transplant patients infected with respiratory syncytial virus

Practical guidelines: lung transplantation in patients with cystic fibrosis

There are no European recommendations on issues specifically related to lung transplantation (LTX) in cystic fibrosis (CF). The main goal of this paper is to provide CF care team members with clinically relevant CF-specific information on all aspects of LTX, highlighting areas of consensus and controversy throughout Europe. Bilateral lung transplantation has been shown to be an important therapeutic option for end-stage CF pulmonary disease. Transplant function and patient survival after transplantation are better than in most other indications for this procedure. Attention though has to be paid to pretransplant morbidity, time for referral, evaluation, indication, and contraindication in children and in adults. This review makes extensive use of specific evidence in the field of lung transplantation in CF patients and addresses all issues of practical importance. The requirements of pre-, peri-, and postoperative management are discussed in detail including bridging to transplant and postoperative complications, immune suppression, chronic allograft dysfunction, infection, and malignancies being the most important. Among the contributors to this guiding information are 19 members of the ECORN-CF project and other experts. The document is endorsed by the European Cystic Fibrosis Society and sponsored by the Christiane Herzog Foundation.

Vertically integrated translational studies of PDX1 as a therapeutic target for pancreatic cancer via a novel bifunctional RNAi platform

RNA interference (RNAi) represents a powerful, new tool for scientific investigation as well as a promising new form of targeted gene therapy, with applications currently in clinical trials. Bifunctional short hairpin RNA (shRNA) are synthetic RNAi molecules, engineered to utilize multiple endogenous RNAi pathways to specifically silence target genes. Pancreatic and duodenal homeobox 1 (PDX1) is a key regulator of pancreatic development, β-cell differentiation, normal β-cell function and pancreatic cancer. Our aim is to review the process of identifying PDX1 as a specific, potential RNAi target in pancreatic cancer, as well as the underlying mechanisms and various forms of RNAi, with subsequent testing and development of PDX1-targeted bifunctional shRNA therapy.

Tunable delivery of siRNA from a biodegradable scaffold to promote angiogenesis in vivo

A system has been engineered for temporally controlled delivery of siRNA from biodegradable tissue regenerative scaffolds. Therapeutic application of this approach to silence prolyl hydroxylase domain 2 promoted expression of pro-angiogenic genes controlled by HIF1α and enhanced scaffold vascularization in vivo. This technology provides a new standard for efficient and controllable gene silencing to modulate host response within regenerative biomaterials.

Recent advances in diagnosis, prevention, and treatment of human respiratory syncytial virus

Human respiratory syncytial virus (RSV) is a common cause of respiratory infection in infants and the elderly, leading to significant morbidity and mortality. The interdisciplinary fields, especially biotechnology and nanotechnology, have facilitated the development of modern detection systems for RSV. Many anti-RSV compounds like fusion inhibitors and RNAi molecules have been successful in laboratory and clinical trials. But, currently, there are no effective drugs for RSV infection even after decades of research. Effective diagnosis can result in effective treatment, but the progress in both of these facets must be concurrent. The development in prevention and treatment measures for RSV is at appreciable pace, but the implementation into clinical practice still seems a challenge. This review attempts to present the promising diverse research approaches and advancements in the area of diagnosis, prevention, and treatment that contribute to RSV management.

Novel antiviral agents for respiratory viral infection in immunocompromised adults

Respiratory viruses cause significant morbidity and mortality in immunocompromised populations such as stem cell transplant and solid organ transplant patients. Few viruses causing respiratory tract infection have an approved therapy, and many of the viruses have no therapeutic options at all. In this article, we describe novel agents under development for treatment options against several respiratory viruses.

Strategies for reducing the risk of respiratory syncytial virus infection in infants and young children: a Canadian nurses' perspective

Respiratory syncytial virus (RSV) infections are prevalent globally and can cause substantial morbidity in infants and young children. The virus is easily transmitted by direct hand-to-hand contact and can lead to serious respiratory disease and hospitalization, particularly in premature infants and children with certain medical conditions. Educating families with young children, especially those in remote rural regions, regarding the potential adverse health outcomes of RSV infection and measures to reduce the risk of transmitting or acquiring RSV has been a key focus of the health care system in Canada. Geographic, cultural, and socioeconomic factors present formidable challenges to the execution of this endeavor. Therefore, it is critical to develop and systematically implement effective educational programs for both families and health care providers. In Canada, nurses play a critical role in education and counseling. In this review, we share our perspectives and suggest empirical practices that may be applicable worldwide.

Respiratory syncytial virus: how, why and what to do

Bronchiolitis is the leading cause of hospitalization of infants and young children worldwide. Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Studies conducted using molecular diagnostic assays confirmed that RSV accounts for over 50% of bronchiolitis in young children requiring hospitalization. Those studies demonstrate that it is common to identify RSV in association with a second viral agent but it is yet unclear whether the simultaneous detection of two or even three viruses is associated with increased disease severity. Despite extensive efforts, a vaccine for prevention of RSV infection is not yet available. Palivizumab a humanized monoclonal antibody directed against the F protein of RSV is the only agent licensed to prevent severe RSV disease in high-risk children. Among the new antivirals being developed for treatment of RSV infections, an RNA-interference based agent has demonstrated promising results for treatment of lung transplant recipients with acute RSV infection.

Expression of non-structural-1A binding protein in lung epithelial cells is modulated by miRNA-548an on exposure to influenza A virus

Understanding the host response to influenza A virus infection is essential for developing intervention approaches. We show that infection of human alveolar epithelial cells and human bronchial epithelial cells with influenza A for 3h resulted in down-regulation of host hsa-miRNA-548an (miRNA-548an) which triggered the overexpression of influenza non-structural-1A binding protein (IVNS1ABP, herein referred to as NS1ABP). Reduced NS1ABP mRNA and NS1ABP protein expression after transfection of miRNA-548an mimic or increased NS1ABP mRNA and NS1ABP protein expression after transfection of miRNA-548an inhibitor provided evidence that miRNA-548an is involved in the regulation of NS1ABP. Transfection of cells with inhibitor led to reduced apoptosis of infected cells while transfection of mimic led to increased apoptosis and reduced influenza copy number suggesting that NS1ABP has a role in viral maintenance. Thus, miRNA-548an may be an important target in controlling the early stage infection of influenza A.

Efficient Biodistribution and Gene Silencing in the Lung epithelium via Intravenous Liposomal Delivery of siRNA

RNA interference (RNAi) may provide a therapeutic solution to many pulmonary epithelium diseases. However, the main barrier to the clinical use of RNAi remains the lack of efficient delivery vectors. Research has mainly concentrated on the intranasal route of delivery of short interfering RNA (siRNA) effector molecules for the treatment of respiratory diseases. However, this may be complicated in a diseased state due to the increased fluid production and tissue remodeling. Therefore, we investigated our hydration of a freeze-dried matrix (HFDM) formulated liposomes for systemic delivery to the lung epithelium. Here, we show that 45 ± 2% of epithelial murine lung cells receive siRNA delivery upon intravenous (IV) liposomal administration. Furthermore, we demonstrate that liposomal siRNA delivery resulted in targeted gene and protein knockdown throughout the lung, including lung epithelium. Taken together, this is the first description of lung epithelial delivery via cationic liposomes, and provides a proof of concept for the use of IV liposomal RNAi delivery to specifically knockdown targeted genes in the respiratory system. This approach may provide an attractive alternate therapeutic delivery strategy for the treatment of lung epithelium diseases.

Silencing of indoleamine 2,3-dioxygenase enhances dendritic cell immunogenicity and antitumour immunity in cancer patients

Dendritic cells (DCs) are being explored as a therapeutic vaccine for cancers. However, their immunogenic potential is limited by the presence of immunosuppressive factors. Among these factors is the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO). In this study, we have investigated the safety, immunogenicity and clinical response of IDO-silenced DC vaccine in four patients with gynecological cancers. DCs were transfected with IDO small interfering RNA and mRNA encoding human telomerase reverse transcriptase (hTERT) or survivin, two universal tumour antigens. Silencing of IDO in DCs did not affect the expression of the co-stimulatory molecules CD80 and CD86, but enhanced the expression of the CCR7 and CD40 molecules. IDO-silenced DCs showed superior potency to activate allogeneic T cells compared to their IDO-positive counterparts. The immunisation with this novel DC cancer vaccine was well tolerated and all patients developed delayed-type hypersensitivity skin reaction and specific T-cell response against hTERT and survivin tumour antigens. Perhaps most importantly, the immune response seen in the patients was related to objective clinical response. Thus, IDO silencing can enhance the immunogenic function of DCs in vitro and in vivo. Overall, the data provide proof-of-principle that immunisation with IDO-silenced DC vaccine is safe and effective in inducing antitumour immunity.

siRNA Delivery from an Injectable Scaffold for Wound Therapy

SIGNIFICANCE

Aberrant overexpression of proinflammatory molecules is believed to be a key mediator in the formation of chronic skin wounds, and the inhibition of these signals may be an effective therapeutic strategy to promote healing. Small interfering RNA (siRNA) can provide gene-specific silencing and may present a safe and effective route for knockdown of inflammatory or other target proteins in chronic skin wounds.

CRITICAL ISSUES

siRNA suffers from delivery barriers in vivo such as susceptibility to degradation, membrane impermeability, and transient activity. Therefore, a delivery strategy that stabilizes siRNA, provides intracellular (cytoplasmic) delivery, and produces temporally sustained activity is needed. The novel approach described combines pH-responsive, siRNA-loaded nanoparticles into a biodegradable polyurethane (PUR) scaffold and presents a promising platform for effective, local silencing of deleterious genes in nonhealing skin wounds.

RECENT ADVANCES

The siRNA delivery barriers have been overcome using a nanoparticulate carrier that protects siRNA and responds to pH gradients in the endo-lysosomal pathway to mediate cytosolic delivery. Nanoparticle incorporation into a biodegradable PUR scaffold provides a means for controlling the delivery kinetics of siRNA-loaded carriers. Furthermore, the PUR is injectable, making it feasible for clinical use, and provides a porous tissue template for cell in-growth during tissue regeneration and remodeling. This local siRNA delivery platform can be tuned to optimize release kinetics for specific pathologies.

FUTURE DIRECTIONS

siRNA may provide a new class of biologic drugs that will outperform growth factor approaches, which have shown only moderate clinical success. The new platform presented here may provide clinicians with an improved option for wound care.

A linear polyethylenimine mediated siRNA-based therapy targeting human epidermal growth factor receptor in SPC-A1 xenograft mice

Background

Linear polyethylenimine (LPEI) is considered as a desirable gene in vivo delivery system, but whether it could deliver the specific siRNA targeted EGFR to the tumor site to inhibit the growth of NSCLC xenograft in nude mice still needs to be examined.

Methods

In this study, LPEI/siRNA was made into a complex and SPC-A1-xenografted mice model was established. Then, stable LPEI/siRNA-EGFR complexes were intraperitoneally administrated. Afterwards, tumor growth was measured every 3 days. At the end of the experiment, tumor volume was calculated, and tumors were weighed, and examined for EGFR expression, proliferation, and apoptosis evaluations. By using blood samples, toxicity tests including aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea and creatinine (Cr) were measured for liver and renal function evaluation. Serum concentrations of TNF-α and IFN-γ were also examined.

Results

Our results demonstrated that LPEI/siRNA-EGFR complexes could downregulate EGFR expression in SPC-A1 xenografted tumor upon single i.p. injection. LPEI/siRNA-EGFR complexes inhibited tumor growth and did not induce organ toxicity in SPC-A1-xenografted mice. At the end of the experiment no significant IFN-α increase was detected in LPEI/siRNA complexes or glucose-treated groups.

Conclusions

The novel modality of siRNA-based therapy targeting EGFR may be of great potential in NSCLC treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/2213-0802-1-2) contains supplementary material, which is available to authorized users.

RNAi Therapeutic Platforms for Lung Diseases

RNA interference (RNAi) is rapidly becoming an important method for analyzing gene functions in many eukaryotes and holds promise for the development of therapeutic gene silencing. The induction of RNAi relies on small silencing RNAs, which affect specific messenger RNA (mRNA) degradation. Two types of small RNA molecules, i.e. small interfering RNAs (siRNAs) and microRNAs (miRNAs), are central to RNAi. Drug discovery studies and novel treatments of siRNAs are currently targeting a wide range of diseases, including various viral infections and cancers. Lung diseases in general are attractive targets for siRNA therapeutics because of their lethality and prevalence. In addition, the lung is anatomically accessible to therapeutic agents via the intrapulmonary route. Recently, increasing evidence indicates that miRNAs play an important role in lung abnormalities, such as inflammation and oncogenesis. Therefore, miRNAs are being targeted for therapeutic purposes. In this review, we present strategies for RNAi delivery and discuss the current state-of-the-art RNAi-based therapeutics for various lung diseases.

Delivery systems and local administration routes for therapeutic siRNA

With the increasing number of studies proposing new and optimal delivery strategies for the efficacious silencing of gene-related diseases by the local administration of siRNAs, the present review aims to provide a broad overview of the most important and latest developments of non-viral siRNA delivery systems for local administration. Moreover, the main disease targets for the local delivery of siRNA to specific tissues or organs, including the skin, the lung, the eye, the nervous system, the digestive system and the vagina, were explored.

Pharmacological Characterization of a Novel ENaCα siRNA (GSK2225745) With Potential for the Treatment of Cystic Fibrosis

Lung pathology in cystic fibrosis is linked to dehydration of the airways epithelial surface which in part results from inappropriately raised sodium reabsorption through the epithelial sodium channel (ENaC). To identify a small-interfering RNA (siRNA) which selectively inhibits ENaC expression, chemically modified 21-mer siRNAs targeting human ENaCα were designed and screened. GSK2225745, was identified as a potent inhibitor of ENaCα mRNA (EC₅₀ (half maximal effective concentration) = 0.4 nmol/l, maximum knockdown = 85%) and protein levels in A549 cells. Engagement of the RNA interference (RNAi) pathway was confirmed using 5′ RACE. Further profiling was carried out in therapeutically relevant human primary cells. In bronchial epithelial cells, GSK2225745 elicited potent suppression of ENaCα mRNA (EC₅₀ = 1.6 nmol/l, maximum knockdown = 82%). In human nasal epithelial cells, GSK2225745 also produced potent and long-lasting (≥72 hours) suppression of ENaCα mRNA levels which was associated with significant inhibition of ENaC function (69% inhibition of amiloride-sensitive current in cells treated with GSK2225745 at 10 nmol/l). GSK2225745 showed no evidence for potential to stimulate toll-like receptor (TLR)3, 7 or 8. In vivo, topical delivery of GSK2225745 in a lipid nanoparticle formulation to the airways of mice resulted in significant inhibition of the expression of ENaCα in the lungs. In conclusion, GSK2225745 is a potent inhibitor of ENaCα expression and warrants further evaluation as a potential novel inhaled therapeutic for cystic fibrosis.

Respiratory syncytial virus mechanisms to interfere with type 1 interferons

Respiratory syncytial virus (RSV) is a member of the Paramyxoviridae family that consists of viruses with nonsegmented negative-strand RNA genome. Infection by these viruses triggers the innate antiviral response of the host, mainly type I interferon (IFN). Essentially all other viruses of this family produce IFN suppressor functions by co-transcriptional RNA editing. In contrast, RSV has evolved two unique nonstructural proteins, NS1 and NS2, to effectively serve this purpose. Together, NS1 and NS2 degrade or sequester multiple signaling proteins that affect both IFN induction and IFN effector functions. While the mechanism of action of NS1 and NS2 is a subject of active research, their effect on adaptive immunity is also being recognized. In this review, we discuss various aspects of NS1 and NS2 function with implications for vaccine design.

The Role of Infections in BOS

Background: Infectious agents, particularly cytomegalovirus (CMV), have long been considered to be potential triggers for BOS, although the exact magnitude of the role of infections and the mechanisms thereof remain an area of active research. Methods: This chapter will review previous literature and newer results concerning the possible roles of CMV, other herpesviruses, community-acquired respiratory viruses, bacteria (including Pseudomonas, other gram-negative, gram-positive, and atypical organisms), and fungi, including colonization as well as invasive infection. Results: The text reviews and evaluates the body of literature supporting a role for these infectious agents as risk factors for BOS and time to BOS. Changing patterns of infection over time are taken into account, and studies that have shown an association between BOS (or lack thereof) and CMV are reviewed. Strategies for prevention or early treatment of infections are discussed as potential means of preserving allograft function long term. Immunizations, stringent infection-control practices, and antimicrobial treatment including newer therapies will be discussed. Conclusion: In addition to the classic literature that has focused on CMV, an expanding spectrum of infectious organisms has been implicated as possible risk factors for BOS. Increasing knowledge of the impact of long-term antiviral suppression, prophylaxis, and outcomes of early therapy will help guide future recipient management.

Respiratory syncytial virus disease: prevention and treatment

Respiratory syncytial virus (RSV) is one of the most clinically important viruses infecting young children, the elderly, and the immunocompromised. Over the past decade, the most significant advance in the prevention of RSV disease has been the development of high-titered antibody products. Infection control is the only other strategy to prevent RSV disease. A humanized monoclonal antibody directed against the fusion (F) protein palivizumab, (Synagis®, MedImmune, Inc., Gaithersburg, MD), is given routinely on a monthly basis to premature infants and young children less than 24 months of age with underlying medical problems including prematurity, chronic lung disease, or cardiac disease to prevent RSV disease and hospitalization. Other products utilizing polyclonal or monoclonal antibodies or antibody fragments against the F protein have been developed and some already tested in patient populations. The only licensed antiviral treatment available today is ribavirin, a guanosine analogue generally administered as a small particle aerosol to immunocompromised patients with lower respiratory tract disease due to RSV. This drug has also been utilized in oral and intravenous forms, again mainly in immunocompromised patients. Promising new antiviral agents under development by multiple pharmaceutical and biotechnology companies include small molecule fusion inhibitors, attachment inhibitors, inhibitors of RNA synthesis, and small interfering RNA particles (siRNA).

Clinical and epidemiologic features of respiratory syncytial virus

Since its discovery in 1955, respiratory syncytial virus (RSV) has consistently been noted to be the single most important cause of lower respiratory tract illness in infants <1 year of age. RSV also causes repeat infections and significant disease throughout life. In addition to the young child, persons with compromised immune, pulmonary or cardiac systems, and the elderly have significant risk from infection. Though RSV causes the full spectrum of acute respiratory illnesses, it is most notably associated with signs and symptoms of increased airway resistance manifested as wheezing and, in the young child, diagnosed as bronchiolitis. In temperate climates, RSV occurs as yearly outbreaks usually between late fall and early spring lasting 3-4 months in a community. The timing of outbreaks varies between years and in the same year between regions and even between nearby communities. RSV can be a serious nosocomial pathogen in high risk individuals but nosocomial transmission that can often be prevented with meticulous attention to good infection control practices. High risk groups include the premature infants and persons of any age with compromised cardiac, pulmonary, or immune systems. Risk factors for infection include increased number of children in the household and day care center attendance. There are reasonable estimates of the sizable burden of RSV disease in infants and young children and the elderly but less data on disease in older children, the role of RSV in later reactive airway disease (see chapter by M.T. Lotz et al. , this volume), and RSV-associated mortality in developing countries. The available data on burden of disease suggests there are at least four potential target populations for a vaccine, the young infant, young children >4-6 months of age, pregnant women, and the elderly. A link between infection in the young infant and later reactive airway disease and mortality in developing countries is needed. Each target population has different vaccine safety and efficacy concerns and may warrant a different type of vaccine.

Targeting RSV with vaccines and small molecule drugs

Respiratory syncytial virus (RSV) is the most significant cause of pediatric respiratory infections. Palivizumab (Synagis®), a humanized monoclonal antibody, has been used successfully for a number of years to prevent severe RSV disease in at-risk infants. However, despite intense efforts, there is no approved vaccine or small molecule drug for RSV. As an enveloped virus, RSV must fuse its envelope with the host cell membrane, which is accomplished through the actions of the fusion (F) glycoprotein, with attachment help from the G glycoprotein. Because of their integral role in initiation of infection and their accessibility outside the lipid bilayer, these proteins have been popular targets in the discovery and development of antiviral compounds and vaccines against RSV. This review examines advances in the development of antiviral compounds and vaccine candidates.

Fourth European Conference on Infections in Leukaemia (ECIL-4): guidelines for diagnosis and treatment of human respiratory syncytial virus, parainfluenza virus, metapneumovirus, rhinovirus, and coronavirus

Community-acquired respiratory virus (CARV) infections have been recognized as a significant cause of morbidity and mortality in patients with leukemia and those undergoing hematopoietic stem cell transplantation (HSCT). Progression to lower respiratory tract infection with clinical and radiological signs of pneumonia and respiratory failure appears to depend on the intrinsic virulence of the specific CARV as well as factors specific to the patient, the underlying disease, and its treatment. To better define the current state of knowledge of CARVs in leukemia and HSCT patients, and to improve CARV diagnosis and management, a working group of the Fourth European Conference on Infections in Leukaemia (ECIL-4) 2011 reviewed the literature on CARVs, graded the available quality of evidence, and made recommendations according to the Infectious Diseases Society of America grading system. Owing to differences in screening, clinical presentation, and therapy for influenza and adenovirus, ECIL-4 recommendations are summarized for CARVs other than influenza and adenovirus.

Target mRNA inhibition by oligonucleotide drugs in man

Oligonucleotide delivery in vivo is commonly seen as the principal hurdle to the successful development of oligonucleotide drugs. In an analysis of 26 oligonucleotide drugs recently evaluated in late-stage clinical trials we found that to date at least half have demonstrated suppression of the target mRNA and/or protein levels in the relevant cell types in man, including those present in liver, muscle, bone marrow, lung, blood and solid tumors. Overall, this strongly implies that the drugs are being delivered to the appropriate disease tissues. Strikingly we also found that the majority of the drug targets of the oligonucleotides lie outside of the drugable genome and represent new mechanisms of action not previously investigated in a clinical setting. Despite the high risk of failure of novel mechanisms of action in the clinic, a subset of the targets has been validated by the drugs. While not wishing to downplay the technical challenges of oligonucleotide delivery in vivo, here we demonstrate that target selection and validation are of equal importance for the success of this field.

RSV prevention and treatment in pediatric lung transplant patients: a survey of current practices among the International Pediatric Lung Transplant Collaborative

RSV infection can be severe after pediatric lung transplantation. Strategies to prevent and treat RSV in this population are underreported. To assess the current practices, we surveyed the members of the IPLTC regarding RSV prevention and treatment strategies. Twenty-eight programs were surveyed; 18 (64.3%) responded at least partially. A median of 53 transplants (range, 8-355) occurred since inception. RSV testing occurs in asymptomatic (6/17) and symptomatic (17/17) patients. Diagnostic method is polymerase chain reaction at 13 sites and DFA at 8. Transplant candidates were received prophylaxis at 10 sites, with nine following national (5) or local (4) guidelines. All use palivizumab IM and/or IV. Recipients were received prophylaxis with palivizumab at eight centers (eight IM, one IV). Fourteen were treated for RSV (seven all patients; seven age-related). Medications include inhaled (6), oral (4), or IV (4) ribavirin, plus IVIG (9), steroids (8), and IV (2) or IM (3) palivizumab. Prevention and treatment barriers include insurance/hospital concerns, such as institutional reluctance to use inhaled ribavirin. RSV prevention and treatment strategies are diverse at pediatric lung transplant programs. Many centers offer prophylaxis (9/17) and treatments (14/17), but strategies are not uniform.

Identifying targets in the hunt for effective respiratory syncytial virus interventions

Respiratory syncytial virus (RSV) is a major cause of human infections worldwide. There is currently no effective vaccine or antiviral therapy available for widespread clinical use; prophylaxis with anti-RSV antibodies is used in only a small percentage of potential recipients. New targets for effective RSV interventions are needed. Previous anti-RSV intervention strategies have focused on targeting aspects of the virus, an approach that can lead to the emergence of resistant RSV strains. Increased understanding of the biology of RSV-host interactions provides an alternative approach for identifying novel targets for RSV interventions that focus on host factors, and exploiting them with the aim to limit the incidence and severity of RSV infections.

The chemistry and biology of oligonucleotide conjugates

Short DNA or RNA oligonucleotides have tremendous potential as therapeutic agents. Because of their ability to engage in Watson-Crick base pairing, they can interact with mRNA or pre-mRNA targets with high selectivity. As a result, they could precisely manipulate gene expression. This possibility has engendered extensive efforts to develop oligonucleotides as drugs, and many candidates are already in clinical trials. However, a major impediment to the maturation of this field of oligonucleotide-based therapeutics remains: these relatively large and often highly charged molecules don't easily cross cellular membranes, making it difficult for them to reach their sites of action in the cytosol or nucleus. In this Account, we summarize some basic features of the biology of antisense and siRNA oligonucleotides. We then discuss chemical conjugation as an approach to improving the intracellular delivery and therapeutic potential of these agents. Instead of focusing on the details of conjugation chemistry, we emphasize the pharmacological ramifications of oligonucleotide conjugates. In one important approach to improving delivery and efficacy, researchers have conjugated oligonucleotides with ligands designed to bind to particular receptors and thus provide specific interactions with cells. In another strategy, researchers have coupled antisense or siRNA with agents such as cell penetrating peptides that are designed to provoke escape of the conjugate from intracellular vesicular compartments. Although both of these strategies have had some success, further research is needed before oligonucleotide conjugates can find an important place in human therapeutics.

Targeting mutant huntingtin for the development of disease-modifying therapy

Huntington's disease (HD) is a progressive and fatal neurodegenerative disease, and the most common inherited CAG repeat disorder. A polyglutamine expansion in the N-terminus of the huntingtin protein (HTT) leads to protein misfolding and downstream pathogenic processes culminating in widespread functional impairment and neurodegeneration in the striatum, cortex and other brain areas. To date, only symptomatic treatments are available that address motor, psychiatric and cognitive deficits. Here we review recent strategies for developing disease-modifying therapies designed to limit or abolish the pathogenic activities of the primary molecular target in HD, the mutant HTT protein itself.

Assessing Modeled CO(2) Retention and Rebreathing of a Facemask Designed for Efficient Delivery of Aerosols to Infants

Background. New aerosol drugs for infants may require more efficient delivery systems, including face masks. Maximizing delivery efficiency requires tight-fitting masks with minimal internal mask volumes, which could cause carbon dioxide (CO₂) retention. An RNA-interference-based antiviral for treatment of respiratory syncytial virus in populations that may include young children is designed for aerosol administration. CO₂ accumulation within inhalation face masks has not been evaluated. Methods. We simulated airflow and CO₂ concentrations accumulating over time within a new facemask designed for infants and young children (PARI SMARTMASK^® Baby). A one-dimensional model was first examined, followed by 3-dimensional unsteady computational fluid dynamics analyses. Normal infant breathing patterns and respiratory distress were simulated. Results. The maximum average modeled CO₂ concentration within the mask reached steady state (3.2% and 3% for normal and distressed breathing patterns resp.) after approximately the 5th respiratory cycle. After steady state, the mean CO₂ concentration inspired into the nostril was 2.24% and 2.26% for normal and distressed breathing patterns, respectively. Conclusion. The mask is predicted to cause minimal CO₂ retention and rebreathing. Infants with normal and distressed breathing should tolerate the mask intermittently delivering aerosols over brief time frames.

Respiratory viral infections post-lung transplantation

Community-acquired respiratory viruses (CARVs) are common pathogens in lung transplant recipients. Infection due to these viruses is associated with multiple complications including: rhinitis, pharyngitis, bronchitis, pneumonia, respiratory failure and even death. CARVs have also become increasingly recognized as a risk factor for acute rejection (AR) and bronchiolitis obliterans syndrome (BOS). Newer diagnostic techniques have enhanced the accuracy of diagnosis, but proven treatment options for CARVs are limited. Further insight into the immune response and allograft dysfunction associated with CARV infections is needed in order to develop novel management strategies which can reduce the morbidity and mortality caused by these infectious agents.

Antiviral effects of small interfering RNA simultaneously inducing RNA interference and type 1 interferon in coxsackievirus myocarditis

Antiviral therapeutics are currently unavailable for treatment of coxsackievirus B3, which can cause life-threatening myocarditis. A modified small interfering RNA (siRNA) containing 5'-triphosphate, 3p-siRNA, was shown to induce RNA interference and interferon activation. We aimed to develop a potent antiviral treatment using CVB3-specific 3p-siRNA and to understand its underlying mechanisms. Virus-specific 3p-siRNA was superior to both conventional virus-specific siRNA with an empty hydroxyl group at the 5' end (OH-siRNA) and nonspecific 3p-siRNA in decreasing viral replication and subsequent cytotoxicity. A single administration of 3p-siRNA dramatically attenuated virus-associated pathological symptoms in mice with no signs of toxicity, and their body weights eventually reached the normal range. Myocardial inflammation and fibrosis were rare, and virus production was greatly reduced. A nonspecific 3p-siRNA showed relatively less protective effect under identical conditions, and a virus-specific OH-siRNA showed no protective effects. We confirmed that virus-specific 3p-siRNA simultaneously activated target-specific gene silencing and type I interferon signaling. We provide a clear proof of concept that coxsackievirus B3-specific 3p-siRNA has 2 distinct modes of action, which significantly enhance antiviral activities with minimal organ damage. This is the first direct demonstration of improved antiviral effects with an immunostimulatory virus-specific siRNA in coxsackievirus myocarditis, and this method could be applied to many virus-related diseases.

Prophylaxis and treatment of respiratory syncytial virus in adult immunocompromised patients

OBJECTIVE

To review the literature regarding current strategies and strategies under active development for the prevention and treatment of respiratory syncytial virus (RSV) infections in immunocompromised adults.

DATA SOURCES

The MEDLINE/PubMed, EMBASE, and Cochrane databases were queried from January 1980 to December 2011 for articles in English using these associated search terms: respiratory syncytial virus, ribavirin, intravenous immunoglobulin, IVIG, palivizumab, motavizumab, lung, pneumonia, transplantation, bone marrow, cancer, malignancy, and vaccine.

STUDY SELECTION AND DATA EXTRACTION

All relevant original studies, meta-analyses, systematic reviews, and review articles were assessed for inclusion. References from pertinent articles were examined for additional content not found during the initial search.

DATA SYNTHESIS

RSV in the immunocompromised adult can lead to significant morbidity and mortality. Treatment of RSV-infected adults is limited to antiviral therapy with ribavirin (aerosolized, oral, intravenous) and immunomodulation with intravenous immunoglobulins, corticosteroids, and palivizumab. Existing literature is predominantly case reports, small trials, and retrospective reviews of patients infected with RSV who have undergone lung or hematopoietic stem cell transplantation (HSCT). Palivizumab may be a viable option for prophylaxis against RSV in high-risk adults. Ribavirin is the most studied treatment option and should remain the backbone of multidrug regimens. Of the routes of administration, aerosolized ribavirin carries the preponderance of evidence and, though challenging, is preferred to limit systemic toxicities in the infected patient. Addition of an immunomodulator to ribavirin may provide a survival benefit over ribavirin alone; however, this has only been studied in a subset of HSCT patients with lower respiratory tract RSV infection.

CONCLUSIONS

Research most strongly supports the use of aerosolized ribavirin as the treatment strategy for immunocompromised adults with RSV. Addition of an immunomodulator may provide a survival benefit over ribavirin alone. Strategies and supportive data for the prevention of RSV infection in the high-risk adult are critically needed.

Respiratory syncytial virus NS1 protein colocalizes with mitochondrial antiviral signaling protein MAVS following infection

Respiratory syncytial virus (RSV) nonstructural protein 1(NS1) attenuates type-I interferon (IFN) production during RSV infection; however the precise role of RSV NS1 protein in orchestrating the early host-virus interaction during infection is poorly understood. Since NS1 constitutes the first RSV gene transcribed and the production of IFN depends upon RLR (RIG-I-like receptor) signaling, we reasoned that NS1 may interfere with this signaling. Herein, we report that NS1 is localized to mitochondria and binds to mitochondrial antiviral signaling protein (MAVS). Live-cell imaging of rgRSV-infected A549 human epithelial cells showed that RSV replication and transcription occurs in proximity to mitochondria. NS1 localization to mitochondria was directly visualized by confocal microscopy using a cell-permeable chemical probe for His₆-NS1. Further, NS1 colocalization with MAVS in A549 cells infected with RSV was shown by confocal laser microscopy and immuno-electron microscopy. NS1 protein is present in the mitochondrial fraction and co-immunoprecipitates with MAVS in total cell lysatesof A549 cells transfected with the plasmid pNS1-Flag. By immunoprecipitation with anti-RIG-I antibody, RSV NS1 was shown to associate with MAVS at an early stage of RSV infection, and to disrupt MAVS interaction with RIG-I (retinoic acid inducible gene) and the downstream IFN antiviral and inflammatory response. Together, these results demonstrate that NS1 binds to MAVS and that this binding inhibits the MAVS-RIG-I interaction required for IFN production.

The Prophylaxis and Treatment with Antiviral Agents of Respiratory Syncytial Virus Infections

In this review, we consider recent advances in the discovery and development of antiviral agents for respiratory syncytial virus (RSV) infections. A background to the various manifestations of human RSV infection and current treatments is provided. The technical, clinical and commercial issues surrounding the development of such antiviral agents are discussed.

RNA-based therapeutics: current progress and future prospects

Recent advances of biological drugs have broadened the scope of therapeutic targets for a variety of human diseases. This holds true for dozens of RNA-based therapeutics currently under clinical investigation for diseases ranging from genetic disorders to HIV infection to various cancers. These emerging drugs, which include therapeutic ribozymes, aptamers, and small interfering RNAs (siRNAs), demonstrate the unprecedented versatility of RNA. However, RNA is inherently unstable, potentially immunogenic, and typically requires a delivery vehicle for efficient transport to the targeted cells. These issues have hindered the clinical progress of some RNA-based drugs and have contributed to mixed results in clinical testing. Nevertheless, promising results from recent clinical trials suggest that these barriers may be overcome with improved synthetic delivery carriers and chemical modifications of the RNA therapeutics. This review focuses on the clinical results of siRNA, RNA aptamer, and ribozyme therapeutics and the prospects for future successes.

MicroRNA-221 modulates RSV replication in human bronchial epithelium by targeting NGF expression

Background

Early-life infection by respiratory syncytial virus (RSV) is associated with aberrant expression of the prototypical neurotrophin nerve growth factor (NGF) and its cognate receptors in human bronchial epithelium. However, the chain of events leading to this outcome, and its functional implications for the progression of the viral infection, has not been elucidated. This study sought to test the hypothesis that RSV infection modulates neurotrophic pathways in human airways by silencing the expression of specific microRNAs (miRNAs), and that this effect favors viral growth by interfering with programmed death of infected cells.

Methodology

Human bronchial epithelial cells infected with green fluorescent protein-expressing RSV (rgRSV) were screened with multiplex qPCR arrays, and miRNAs significantly affected by the virus were analyzed for homology with mRNAs encoding neurotrophic factors or receptors. Mimic sequences of selected miRNAs were transfected into non-infected bronchial cells to confirm the role of each of them in regulating neurotrophins expression at the gene and protein level, and to study their influence on cell cycle and viral replication.

Principal Findings

RSV caused downregulation of 24 miRNAs and upregulation of 2 (p<0.01). Homology analysis of microarray data revealed that 6 of those miRNAs exhibited a high degree of complementarity to NGF and/or one of its cognate receptors TrKA and p75^NTR. Among the selected miRNAs, miR-221 was significantly downregulated by RSV and its transfection in bronchial epithelial cells maximally inhibited gene and protein expression of NGF and TrKA, increased apoptotic cell death, and reduced viral replication and infectivity.

Conclusions/Significance

Our data suggest that RSV upregulates the NGF-TrKA axis in human airways by silencing miR-221 expression, and this favors viral replication by interfering with the apoptotic death of infected cells. Consequently, the targeted delivery of exogenous miRNAs to the airways may provide a new strategy for future antiviral therapies based on RNA interference.

Progress toward in vivo use of siRNAs-II

RNA interference (RNAi) has been extensively employed for in vivo research since its use was first demonstrated in mammalian cells 10 years ago. Design rules have improved, and it is now routinely possible to obtain reagents that suppress expression of any gene desired. At the same time, increased understanding of the molecular basis of unwanted side effects has led to the development of chemical modification strategies that mitigate these concerns. Delivery remains the single greatest hurdle to widespread adoption of in vivo RNAi methods. However, exciting advances have been made and new delivery systems under development may help to overcome these barriers. This review discusses advances in RNAi biochemistry and biology that impact in vivo use and provides an overview of select publications that demonstrate interesting applications of these principles. Emphasis is placed on work with synthetic, small interfering RNAs (siRNAs) published since the first installment of this review which appeared in 2006.

Progress in understanding and controlling respiratory syncytial virus: still crazy after all these years

Human respiratory syncytial virus (RSV) is a ubiquitous pathogen that infects everyone worldwide early in life and is a leading cause of severe lower respiratory tract disease in the pediatric population as well as in the elderly and in profoundly immunosuppressed individuals. RSV is an enveloped, nonsegmented negative-sense RNA virus that is classified in Family Paramyxoviridae and is one of its more complex members. Although the replicative cycle of RSV follows the general pattern of the Paramyxoviridae, it encodes additional proteins. Two of these (NS1 and NS2) inhibit the host type I and type III interferon (IFN) responses, among other functions, and another gene encodes two novel RNA synthesis factors (M2-1 and M2-2). The attachment (G) glycoprotein also exhibits unusual features, such as high sequence variability, extensive glycosylation, cytokine mimicry, and a shed form that helps the virus evade neutralizing antibodies. RSV is notable for being able to efficiently infect early in life, with the peak of hospitalization at 2-3 months of age. It also is notable for the ability to reinfect symptomatically throughout life without need for significant antigenic change, although immunity from prior infection reduces disease. It is widely thought that re-infection is due to an ability of RSV to inhibit or subvert the host immune response. Mechanisms of viral pathogenesis remain controversial. RSV is notable for a historic, tragic pediatric vaccine failure involving a formalin-inactivated virus preparation that was evaluated in the 1960s and that was poorly protective and paradoxically primed for enhanced RSV disease. RSV also is notable for the development of a successful strategy for passive immunoprophylaxis of high-risk infants using RSV-neutralizing antibodies. Vaccines and new antiviral drugs are in pre-clinical and clinical development, but controlling RSV remains a formidable challenge.

Using drug-excipient interactions for siRNA delivery

SiRNA is the trigger of RNA interference, a mechanism discovered in the late 1990s. To release the therapeutic potential of this versatile but large and fragile molecule, excipients are used which either interact by electrostatic interaction, passively encapsulate siRNA or are covalently attached to enable specific and safe delivery of the drug substance. Controlling the delicate balance between protective complexation and release of siRNA at the right point and time is done by understanding excipients–siRNA interactions. These can be lipids, polymers such as PEI, PLGA, Chitosans, Cyclodextrins, as well as aptamers and peptides. This review describes the mechanisms of interaction of the most commonly used siRNA delivery vehicles, and looks at the results of their clinical and preclinical studies.