Reduced long-term respiratory morbidity after treatment of respiratory syncytial virus bronchiolitis with ribavirin in previously healthy infants: a preliminary report

Past, Present and Future Approaches to the Prevention and Treatment of Respiratory Syncytial Virus Infection in Children

INTRODUCTION

The REGAL (RSV Evidence - A Geographical Archive of the Literature) series has provided a comprehensive review of the published evidence in the field of respiratory syncytial virus (RSV) in Western countries over the last 20 years. This seventh and final publication covers the past, present and future approaches to the prevention and treatment of RSV infection among infants and children.

METHODS

A systematic review was undertaken of publications between January 1, 1995 and December 31, 2017 across PubMed, Embase and The Cochrane Library. Studies reporting data on the effectiveness and tolerability of prophylactic and therapeutic agents for RSV infection were included. Study quality and strength of evidence (SOE) were graded using recognized criteria. A further nonsystematic search of the published literature and Clinicaltrials.gov on antiviral therapies and RSV vaccines currently in development was also undertaken.

RESULTS

The systematic review identified 1441 studies of which 161 were included. Management of RSV remains centered around prophylaxis with the monoclonal antibody palivizumab, which has proven effective in reducing RSV hospitalization (RSVH) in preterm infants < 36 weeks' gestational age (72% reduction), children with bronchopulmonary dysplasia (65% reduction), and infants with hemodynamically significant congenital heart disease (53% reduction) (high SOE). Palivizumab has also shown to be effective in reducing recurrent wheezing following RSVH (high SOE). Treatment of RSV with ribavirin has conflicting success (moderate SOE). Antibodies with increased potency and extended half-life are currently entering phase 3 trials. There are approximately 15 RSV vaccines in clinical development targeting the infant directly or indirectly via the mother.

CONCLUSION

Palivizumab remains the only product licensed for RSV prophylaxis, and only available for high-risk infants. For the general population, there are several promising vaccines and monoclonal antibodies in various stages of clinical development, with the aim to significantly reduce the global healthcare impact of this common viral infection.

FUNDING

AbbVie.

Mutagenic Effects of Ribavirin on Hepatitis E Virus-Viral Extinction versus Selection of Fitness-Enhancing Mutations

Hepatitis E virus (HEV), an important agent of viral hepatitis worldwide, can cause severe courses of infection in pregnant women and immunosuppressed patients. To date, HEV infections can only be treated with ribavirin (RBV). Major drawbacks of this therapy are that RBV is not approved for administration to pregnant women and that the virus can acquire mutations, which render the intra-host population less sensitive or even resistant to RBV. One of the proposed modes of action of RBV is a direct mutagenic effect on viral genomes, inducing mismatches and subsequent nucleotide substitutions. These transition events can drive the already error-prone viral replication beyond an error threshold, causing viral population extinction. In contrast, the expanded heterogeneous viral population can facilitate selection of mutant viruses with enhanced replication fitness. Emergence of these mutant viruses can lead to therapeutic failure. Consequently, the onset of RBV treatment in chronically HEV-infected individuals can result in two divergent outcomes: viral extinction versus selection of fitness-enhanced viruses. Following an overview of RNA viruses treated with RBV in clinics and a summary of the different antiviral modes of action of this drug, we focus on the mutagenic effect of RBV on HEV intrahost populations, and how HEV is able to overcome lethal mutagenesis.

Improving vaccines by incorporating immunological coadjuvants

While vaccination continues to be the most successful interventionist health policy to date, infectious disease remains a significant cause of death worldwide. A primary reason that vaccination is not able to generate effective immunity is a lack of appropriate adjuvants capable of initiating the desired immune response. Adjuvant combinations can potentially overcome this problem; however, the possible permutations to consider, which include the route and kinetics of vaccination, as well as combinations of adjuvants, are practically limitless. This review aims to summarize the current understanding of adjuvants and related immunological processes and how this knowledge can and has been applied to the strategic selection of adjuvant combinations as components of vaccines against human infectious disease.

Prevention and treatment of respiratory syncytial virus infection in infants: an update

Respiratory syncytial virus (RSV) is a serious pathogen causing significant mortality and morbidity, especially in premature infants and infants with chronic lung disease or significant congenital heart disease. Therapy for RSV infection is essentially supportive, although several new compounds are under investigation. Therefore, immunoprophylaxis to prevent severe RSV disease in high-risk infants assumes great significance. Palivizumab, a humanized monoclonal antibody to RSV, significantly reduces hospitalization in the first 6 months in premature infants born at less than 35 weeks, infants less than 24 months of age with chronic lung disease and requiring treatment in the last 6 months, and in children 24 months or younger with hemodynamically significant heart disease. A new ultrapotent anti-RSV antibody (MEDI-524) appears to be more effective in animals than palivizumab and is undergoing clinical evaluation. There has been considerable progress in the development of vaccines; namely subunit, live attenuated, genetically recombinant virus and polypeptide vaccines. Plasmid DNA vaccines coding for parts of the F and G surface glycoproteins and vaccinia vector vaccines are also being evaluated. Maternal immunization has the potential to prevent RSV disease in early infancy. RSV prophylaxis has seen tremendous progress in the last decade.

Ribavirin for respiratory syncytial virus bronchiolitis reduced the risk of asthma and allergen sensitization

Respiratory syncytial virus (RSV) bronchiolitis in early life is a risk factor for later development of asthma and atopy. Ribavirin is the only effective drug currently available against acute RSV bronchiolitis. However, the long-term effects of ribavirin remain unclear. We investigated a cohort of children hospitalized with RSV bronchiolitis from when they were under 2 yr old until they reached a mean age of 6.2 yr. In total, we enrolled 175 children in this study. Both the group treated with ribavirin and the group not treated with ribavirin included high-risk young children with congenital heart disease or chronic lung disease. Their respective age-matched controls, that we labeled groups A and B, both without ribavirin treatment, consisted of previously healthy subjects. Wheezing was either verified by physicians or estimated by a questionnaire. Allergen sensitization was judged by serum allergen-specific IgE levels. The cumulative incidence of physician-diagnosed asthma or recurrent wheezing in the ribavirin group (15%) was significantly lower than its incidence in the non-ribavirin-treated group (34%, p = 0.049), and in the control A group (43%, p = 0.005). Allergen sensitization was also least frequent in the ribavirin group. Ribavirin therapy was an independent factor in reducing the risk of developing asthma, asthma/recurrent wheezing, and sensitization to D. pteronyssinus/D. farinae. The long-term value of ribavirin for acute RSV bronchiolitis and its underlying mechanisms deserves further research.

Respiratory viral infections in adults with hematologic malignancies and human stem cell transplantation recipients: a retrospective study at a major cancer center

Community respiratory viruses (CRVs) have been recognized as a potential cause of pneumonia and death among hematopoietic stem cell transplantation (HSCT) recipients and patients with hematologic malignancies. We reviewed the Microbiology Laboratory records dated from July 1, 2000, to June 30, 2002, to identify patients who had respiratory specimens positive for influenza, parainfluenza, respiratory syncytial virus, or picornavirus. We identified 343 infections among patients with underlying hematologic malignancies and HSCT. We collected data on type of disease, age, sex, type of infection, neutrophil and lymphocyte counts, therapy, and outcome. Influenza, parainfluenza, and respiratory syncytial virus accounted for most cases and were approximately equal in frequency. Most infections occurred predominantly among recipients of allogeneic transplants. Infection progressed to pneumonia in 119 patients (35%) and occurred with similar frequency for the 3 viruses. Patients at greatest risk for developing pneumonia included those with leukemia, those aged more than 65 years, and those with severe neutropenia or lymphopenia. Lack of respiratory syncytial virus-directed antiviral therapy (p=0.025) and age (p=0.042) were associated with development of respiratory syncytial virus pneumonia, and an absolute lymphocyte count<or=200 cells/mL (p=0.049) was associated with development of influenza pneumonia. The overall mortality rate for CRV pneumonia was 15%. The only independent predictor of fatal outcome was an absolute lymphocyte count<or=200 cells/mL (p=0.03) in patients with influenza pneumonia.HSCT recipients and patients with hematologic malignancies who develop upper respiratory infection due to CRVs should be considered for antiviral therapy of proven efficacy to reduce the risk of pneumonia and death.

Respiratory syncytial virus infections: Recent prospects for control

Respiratory syncytial virus (RSV) infections remain a significant public health problem throughout the world, although recently developed and clinically approved anti-RSV antibodies administered prophylactically to at-risk populations appear to have significantly affected the disease development. Much effort has been expended to develop effective anti-RSV therapies, using both in vitro assay systems and mouse, cotton rat, and primate models, with several products now in various stages of clinical study. Several products are also being considered for the treatment of clinical symptoms of RSV. In this review, updates on the status of the approved anti-RSV antibodies, ribavirin, and recent results of studies with potential new anti-RSV compounds are summarized and discussed.

[Asthma and respiratory syncytial virus. New opportunities for therapeutic intervention]

Numerous studies have described an association between respiratory sincticial virus (RSV) infection in infancy and the subsequent development of airway hyperresponsiveness (AHR). Besides the exaggerated immune response and the abnormal neurogenic mechanisms induced by RSV, recent studies have correlated the "persistence" of RSV in the lower respiratory tract with the development of AHR. Several investigators have evaluated whether treatment with antiviral or immunosuppressive agents could decrease the long term respiratory abnormalities induced by RSV. The RSV murine model has allowed us to study the immunopathogenesis of RSV-induced AHR. Once the airway obstruction, typical of acute disease, is resolved and no virus is longer detected by cell cultures, mice progress into a chronic phase characterized by AHR and persistent airway inflammation. The use of polymerase chain reaction assay for RSV quantitation has demonstrated, quite unexpectedly, the presence of RSV RNA in the lower respiratory tract of mice during the chronic phase of the disease. As an example of intervention, the administration of an anti-RSV neutralizing antibody (palivizumab) was associated with a significant reduction in viral replication, pulmonary inflammation and inflammatory cytokines, as well as a significant improvement in the pulmonary function both in the acute and chronic phases of the disease. Future clinical studies to determine whether therapy with palivizumab can prevent the long-term morbidity associated with RSV in children are warranted.

Effectiveness of drug therapies to treat or prevent respiratory syncytial virus infection-related morbidity

Respiratory syncytial virus (RSV) infection causes a huge burden to the health service, as it results in a large number of in-patient days each year and increases the risk of asthma in childhood. In the acute phase, therapy is supportive as bronchodilators and corticosteroids have resulted, at best, only in short-term benefits; promising treatments for ventilated patients, such as exogenous surfactant, require further testing. Passive immunoprophylaxis reduces hospital admission in high risk groups. In the prevention of chronic respiratory morbidity following RSV infection, however, studies are needed to determine whether immunoprophylaxis will have a useful role and to identify which drug treatment will be most cost-effective.

Pleiotropic mechanisms of ribavirin antiviral activities

Renewed interest in the mechanism of action of ribavirin results from its synergistic enhancement of interferon therapy and the need to develop more efficacious agents to treat hepatitis C virus infection. Since the discovery of ribavirin over 30 years ago by scientists at ICN Pharmaceuticals, many mechanisms of action for ribavirin have been proposed. These include inhibition of host inosine monophosphate dehydrogenase by ribavirin monophosphate, inhibition of viral capping enzymes, inhibition of viral RNA synthesis by ribavirin triphosphate, lethal mutagenesis of viral RNA genomes resulting from promiscuous incorporation of ribavirin triphosphate by the viral RNA polymerase, and modulation of the host immune responses. In this article, we will briefly review the evidence for these mechanisms, emphasizing recent findings. In addition, we will discuss strategies for development of nucleoside analogs that may replace ribavirin in the future.

Bronchiolitis, respiratory syncytial virus, and recurrent wheezing: what is the relationship?

Various follow-up studies of children hospitalized with bronchiolitis caused by respiratory syncytial virus have demonstrated that a significant proportion of infants (50%) have recurrent wheezing during childhood. Nevertheless, the relationship between these two entities, if any, has not been established. In order to explain this observation, several hypotheses have been proposed. The first suggests that some children could have an individual predisposition to bronchiolitis caused by respiratory syncytial virus and recurrent wheezing. The virus could be a marker of this condition, and the individual predisposition could in turn be related to an individual hypersensitivity to common allergens (atopy), airway hyperreactivity, or to some disorder related to pulmonary anatomy or physiology that was present before the acute episode of bronchiolitis. Another hypothesis proposes that respiratory syncytial virus could be directly responsible for recurrent wheezing. During an episode of bronchiolitis, the damage in the airway mucosa caused by the vital inflammatory response to infection contributes to sensitivity to other allergens or exposes irritant receptors, resulting in recurrent wheezing. For this review, we analyzed the studies that discuss these hypotheses with the purpose of clarifying the mechanisms for the important issue of recurrent wheezing in childhood.

Palivizumab in the prevention of respiratory syncytial virus disease

Respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract infection in infants and young children. Premature infants and infants with underlying lung disease are at increased risk for severe RSV infection in the first 1 - 2 years of life. Monthly prophylaxis with palivizumab (Synagis) during RSV season has been proven safe and effective in this population and these effects have persisted over the 4 years since the drug was approved by the US FDA in 1998. Issues remain regarding the optimal candidates for palivizumab prophylaxis and whether additional groups of high-risk individuals, for example infants with congenital heart disease or cystic fibrosis, and immunocompromised hosts, might benefit from such preventive therapy. It is possible that palivizumab in combination with antiviral or anti-inflammatory agents might also prove to be beneficial in the treatment of RSV disease. Newer monoclonal antibodies to RSV in development may offer the potential for less frequent dosing, increased efficacy and a role in treatment of RSV disease, but pending further evaluation of such products palivizumab provides significant protection for high-risk infants against a major pathogen.

Early ribavarin treatment of bronchiolitis: effect on long-term respiratory morbidity

BACKGROUND

The mortality rate from respiratory syncytial virus (RSV) bronchiolitis has significantly reduced over the last decade. A major concern now is the long-term respiratory morbidity following RSV bronchiolitis.

METHODS

In this prospective study, we randomly assigned 49 previously healthy infants with severe RSV bronchiolitis, early in the course of illness (< 5 days duration), to receive either conservative treatment (n = 21) or additional ribavirin treatment (n = 24). Both groups were closely matched for age and clinical characteristics.

RESULTS

During a prospective, closely monitored, 1-year follow-up period, the group treated with ribavirin had significantly fewer episodes (2.7 +/- 2.3 episodes vs 6.4 +/- 4.2 episodes per patient per year) and reduced severity of reactive airway disease (0.08 episodes vs 1.09 episodes of moderate-to-severe illness per patient per year) and respiratory illness-related hospitalization (25 hospital days vs 90 hospital days per 100 patients per year).

CONCLUSIONS

Early ribavirin treatment of RSV bronchiolitis in previously healthy infants resulted in reduction of incidence and severity of reactive airway disease as well as respiratory illness-related hospitalization.

Respiratory syncytial virus infection: clinical features, management, and prophylaxis

Respiratory syncytial virus (RSV) infects almost all children by two years of age, resulting in a large number of hospital admissions in infants. Reactive airway disease is more common after RSV infection, even in previously healthy children. Management of the acute infection is supportive, but preliminary evidence suggests surfactant administration to ventilated infants may be of benefit. Whether ribavirin or corticosteroids reduce respiratory morbidity after RSV infection remains controversial. Immunoprophylaxis reduces RSV admissions, Palivizumab, a humanized monoclonal antibody, is a more cost-effective prophylaxis than RSV immune globulin. Nevertheless, the cost of prophylaxis, unless only given to very high-risk infants, exceeds savings made in reducing admissions.

Prevention and treatment of respiratory syncytial virus bronchiolitis and postbronchiolitic wheezing

Respiratory syncytial virus (RSV) is the primary cause of hospitalization for acute respiratory tract illness in general and specifically for bronchiolitis in young children. The link between RSV bronchiolitis and reactive airway disease is not completely understood, even though RSV bronchiolitis is frequently followed by recurrent episodes of wheezing. Therapy with ribavirin does not appear to significantly reduce long-term respiratory outcome of RSV lower respiratory tract infection, and corticosteroid or bronchodilator therapy may possibly improve outcomes only on a short-term basis. No vaccine against RSV is yet available. It is not known whether prophylaxis with RSV intravenous immune globulin or palivizumab can reduce postbronchiolitic wheezing.

Mechanisms of action of ribavirin in antiviral therapies

Although ribavirin was originally synthesized over 30 years ago and has been used to treat viral infections as monotherapy (respiratory syncytial virus and Lassa fever virus) or with interferon-alpha (IFN-alpha) as combination therapy (hepatitis C virus), the precise mechanism of its therapeutic activities remains controversial. In this review we focus on two main biological properties of ribavirin: its indirect and direct antiviral activities (with particular emphasis on its efficacy against chronic hepatitis C infection). Each property could individually or collectively account for its clinical efficacy against viral infections. First, with emphasis on the evidence for indirect activities of ribavirin, we will review the clinical observations that suggest that the immunomodulatory properties of ribavirin can in part account for its antiviral activities in vivo. We will then describe the mode of ribavirin's direct antiviral activities. These direct activities can be ascribed to several possible mechanisms, including the recently described activity as an RNA mutagen, a property that may be important in driving a rapidly mutating RNA virus over the threshold to 'error catastrophe'.

Respiratory Syncytial Virus: Update on Infection, Treatment, and Prevention

Respiratory syncytial virus (RSV) infection, which primarily manifests as bronchiolitis or pneumonia, is the leading cause of lower respiratory tract infection in infants and young children. It is associated with more than 100,000 pediatric hospitalizations each year in the United States. Infants who were premature; have chronic lung disease, congenital heart disease, or immunodeficiency disorders; or have underlying metabolic or neuromuscular disorders are at increased risk for especially severe RSV disease. Treatment of children hospitalized with RSV disease is primarily supportive, with administration of supplemental oxygen and fluid replacement therapy. Bronchodilators may benefit at least a subset of such patients. Antiviral therapy with aerosolized ribavirin is available for high-risk, severely ill patients. Handwashing, cleaning of environmental surfaces, and cohorting in hospital settings may decrease RSV transmission. In children born premature and younger than 1 year of age, and in patients with bronchopulmonary dysplasia younger than 2 years of age, passive protection against severe RSV disease may be achieved through monthly injections of anti-RSV antibody (palivizumab) during winter months. No vaccine is available to provide active immunity against RSV, but live attenuated and subunit cloned surface protein vaccines are in development.

The effect of ribavirin to treat previously healthy infants admitted with acute bronchiolitis on acute and chronic respiratory morbidity

The role of ribavirin in the treatment of acute bronchiolitis is controversial. It has been suggested that the use of ribavirin may be of benefit during the acute illness and may reduce subsequent recurrent respiratory morbidity. This randomized, double-blind, placebo-controlled study was designed to determine whether ribavirin administered during the acute illness would have an influence on respiratory morbidity during both the acute illness and during the following year. Bronchial reactivity 6 months after the acute illness was also assessed. Forty previously well infants with moderately severe acute bronchiolitis were recruited during three winter epidemics. Subjects received study medication for 18 h a day. Management was otherwise unaltered. Subjects were evaluated daily by the investigator and subsequently assessed at 6 weeks, 6 months and 1 year following the acute illness. Assessment of bronchial hyper-responsiveness was assessed at 6 months of age using total body plethysmography and an established ultra-sonically nebulized distilled water challenge. A total of 40 patients (21 ribavirin, 19 placebo) were entered into the study. The two groups did not differ with respect to age, gender or clinical severity on entry to the trial. No significant differences were identified in the rate of clinical improvement over the first 24 h, the time to discharge, bronchial responsiveness at 6 months of age, frequency of significant respiratory symptoms over the first year of life and the frequency of prescribed bronchodilators and inhaled steroids during the year of follow-up. This study was unable to demonstrate any clinical benefit from the use of ribavirin in the acute illness or during subsequent follow-up for 1 year.

An update on respiratory syncytial virus antiviral agents

Respiratory syncytial virus (RSV), the most common cause of lower respiratory tract disease in infants and young children, is a ubiquitous respiratory pathogen, infecting or reinfecting much of the population every year and causing severe, sometimes fatal disease in high-risk populations of infants and adults, particularly in developing countries. Spurred by the medical and economic burdens of RSV disease and enticed by the economic potential of therapeutic drugs, particularly in the absence to date of a safe and effective RSV vaccine, scientists in many industrial, academic and government laboratories have developed a wide variety of candidate RSV antiviral agents. Most of these have been screened thus far only in cell culture, a few in animal models. Aside from ribavirin, however, none has proven effective in therapeutic clinical trials and even ribavirin usage has declined precipitously in recent years due to concerns over efficacy, safety, ease of use and cost. All of the antiviral compounds discussed in this review were evaluated primarily for their ability to reduce viral load, with little or no attention paid to the role of host inflammation in the pathogenesis of RSV disease. Recent research has highlighted the prominent role of inflammatory mediators and an increasing number of reports suggest that a therapeutic strategy that combines antiviral and anti-inflammatory components will be the most effective way of treating RSV disease.

Long-term consequences of respiratory syncytial virus (RSV) bronchiolitis

Despite differences in study design, follow-up studies consistently show that approximately half of the infants with respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) go on to have recurrent wheezing episodes during childhood. Respiratory symptoms are associated with abnormal lung function, including bronchial hyper-responsiveness. Wheezing symptoms following RSV LRTI gradually decrease, and it appears that during school age airway morbidity is no longer related to RSV LRTI during infancy. Mechanisms underlying the association between RSV LRTI and long-term airway morbidity are poorly understood. On the one hand, abnormal airway function that is congenitally present or acquired before RSV LRTI occurs could be the cause of both RSV LRTI and subsequent recurrent wheezing. On the other hand, it is possible that RSV LRTI causes changes in the lower airways or the immune system that result in long-term airway morbidity. Animal models suggest that RSV infection can promote the development of allergic sensitization, but most studies in humans do not indicate a role for atopy in the development of recurrent wheezing following RSV LRTI.

Respiratory viruses and asthma

Viral infections have become increasingly recognized as a significant cause of asthma exacerbations, mainly because of improved viral detection techniques. Unfortunately, the ability to specifically treat viral infections and to limit the asthma morbidity associated with these agents has not kept pace with diagnostic technology. This article focuses on current concepts of the epidemiology of viruses in asthma exacerbations, investigations studying the physiologic and immunologic consequences of viral infection, and potential therapies to minimize virally-induced airway hyperresponsiveness. To impact this significant health problem, researchers must definitively ascertain the mechanisms by which viruses induce airway reactivity and must develop rational, safe approaches to prevent the consequences of viral infection in the patient with asthma.