Prevention and treatment recommendations for respiratory syncytial virus infection. Background and clinical experience 40 years after discovery

Respiratory Syncytial Virus Infections in Neonates: A Persisting Problem

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infections in young infants. It is an enveloped, single-stranded, nonsegmented, negative-strand RNA virus, a member of the family Pneumoviridae. Globally, RSV is responsible for 2.3% of deaths among neonates 0-27 days of age. Respiratory syncytial virus infection is most common in children aged below 24 months. Neonates present with cough and fever. Respiratory syncytial virus-associated wheezing is seen in 20% infants during the first year of life of which 2-3% require hospitalization. Reverse transcriptase polymerase chain reaction (RT-PCR) gives fast results and has higher sensitivity compared with culture and rapid antigen tests and are not affected by passively administered antibody to RSV. Therapy for RSV infection of the LRT is mainly supportive, and preventive measures like good hygiene and isolation are the mainstay of management. Standard precautions, hand hygiene, breastfeeding and contact isolation should be followed for RSV-infected newborns. Recent AAP guidelines do not recommend pavilizumab prophylaxis for preterm infants born at 29-35 weeks without chronic lung disease, hemodynamically significant congenital heart disease and coexisting conditions. RSV can lead to long-term sequelae such as wheezing and asthma, associated with increased healthcare costs and reduced quality of life.

What Are the Most Powerful Immunogen Design Vaccine Strategies? A Structural Biologist's Perspective

The ability of structure-based design to control the shape and reactivity-the atomic-level chemistry-of an immunogen argues for it being one of the "most powerful" immunogen-design strategies. But antigenic reactivity is only one of the properties required to induce a protective immune response. Here, a multidimensional approach is used to exemplify the enabling role atomic-level information can play in the development of immunogens against three viral pathogens, respiratory syncytial virus, influenza A virus, and human immunodeficiency virus (HIV), which have resisted standard approaches to vaccine development. Overall, structure-based strategies incorporating B-cell ontogenies and viral evasion mechanisms appear exceptionally powerful.

The cost effectiveness of palivizumab in term Inuit infants in the Eastern Canadian Arctic

INTRODUCTION

Canadian, Inuit, full term infants have the highest rate of respiratory syncytial virus (RSV) infection globally, which results in substantial costs associated hospitalisation.

METHODS

Decision-analytical techniques were used to estimate the incremental cost-effectiveness ratio (ICER) for palivizumab compared to no prophylaxis for Inuit infants of all gestational age. The time horizon was that of life-time follow-up, and costs and effectiveness were discounted at 5% per year. Costs (2007 CAD$) for palivizumab, hospitalisation (including medical evacuation, intensive care unit [ICU]), physician visits, and transportation were calculated based on the Canadian payer's perspective. Benefits on decreasing RSV hospitalisation were expressed as quality-adjusted life-years (QALYs). One-way and probabilistic sensitivity analysis (PSA) were conducted, varying: mortality rates, utilities, length of stay in hospital and ICU.

RESULTS

For all of Baffin Island infants (<1 year), the ICER was $39,435/QALY. However, when infants were grouped by age and area of residence, those residing in Iqaluit (<1 year) had an ICER of $152,145/QALY, while those residing in rural areas (outside of Iqaluit) had an ICER of $24,750/QALY. Prophylaxis was a dominant strategy (cost saving) for rural infants under 6 months of age, with the PSA demonstrating that it was dominant 98% of the time.

CONCLUSIONS

The ICERs suggested that palivizumab is a cost-effective option for the prevention of RSV for Inuit infants on Baffin Island compared to no prophylaxis. Palivizumab is highly cost effective in Arctic infants <1 year of age specifically residing outside of Iqaluit and is a dominant strategy for those under 6 months of age in rural areas. However, palivizumab is not cost effective compared to no treatment for infants of all ages residing in Iqaluit.

Cost effectiveness of palivizumab for RSV prevention in high-risk children in the Netherlands

BACKGROUND

Respiratory syncytial virus (RSV) is a common pathogen that is the leading cause of lower respiratory tract infections in young children. High-risk children are at risk of severe infection, which may require hospitalisation. RSV is also associated with a high risk for respiratory morbidity and mortality, which may have long-term clinical and economic consequences.

OBJECTIVE

To assess the cost effectiveness of palivizumab, a humanised monoclonal antibody, used as prevention against severe respiratory syncytial virus (RSV) infection requiring hospitalisation, in the indication of preterm infants and infants with preterm/bronchopulmonary dysplasia and in the second indication of children with congenital heart disease in the Dutch healthcare setting.

METHODS

A decision-tree model was used to estimate the cost effectiveness of palivizumab, used as a preventative treatment against severe respiratory syncytial virus (RSV) infection, in high-risk groups of children in the Netherlands. The analysis was based on a lifetime follow-up period in order to capture the impact of palivizumab on long-term morbidity and mortality resulting from an RSV infection. Data sources included published literature, the palivizumab pivotal trials, official price/tariff lists and national population statistics. The study was conducted from the perspective of society in the Netherlands.

RESULTS

The use of palivizumab results in undiscounted incremental cost-effectiveness ratios of €12,728/QALY and €4,256/QALY in preterm/bronchopulmonary dysplasia and congenital heart disease indications, respectively. Inclusion of indirect costs leads to even more favourable cost-effectiveness outcomes. The study is limited by a number of conservative assumptions. It was assumed that palivizumab only affects the occurrence of RSV hospitalisation and does not influence the severity of the RSV infection. Another assumption was that international clinical trial data and data on utilities could be applied to the Dutch healthcare setting.

CONCLUSION

Palivizumab provides cost-effective prophylaxis against RSV in high-risk infants. The use of palivizumab in these children results in positive short- and long-term health-economic benefits.

Clinical predictors of respiratory syncytial virus infection in children

AIM

The aim of this study was to develop a clinical prediction model that identifies respiratory syncytial virus (RSV) infection in infants and young children.

METHODS

Children < or = 36 months of age with respiratory illness, who were suspected of having RSV infection, were enrolled in this prospective cohort study during the study period between January and February 2002. RSV testing was performed on all patients.

RESULTS

Of the 197 patients enrolled in the study, 126 (64%) were positive for RSV and 71 (36%) patients were either negative for RSV or had a positive culture for viruses other than RSV. The mean age of patients was 5 months and 57% were male. Backwards stepwise logistic regression analysis identified cough (p = 0.000), wheezing (p = 0.002), and retractions (p = 0.008) as independent variables predictive of RSV infection. The prediction model had a sensitivity of 80% (95% CI, 71-87%), specificity of 68% (95% CI, 54-79%), positive predictive value 82% (95% CI, 74-89%), negative predictive value 66% (95% CI, 52-77), positive likelihood ratio 2.5 (95% CI, 1.8-3.7) and post-test probability of 82%.

CONCLUSION

The combination of cough, wheezing and retractions predicts RSV infection in infants and young children.

Respiratory syncytial virus fusion inhibitors. Part 3: Water-soluble benzimidazol-2-one derivatives with antiviral activity in vivo

The introduction of acidic and basic functionality into the side chains of respiratory syncytial virus (RSV) fusion inhibitors was examined in an effort to identify compounds suitable for evaluation in vivo in the cotton rat model of RSV infection following administration as a small particle aerosol. The acidic compounds 2r, 2u, 2v, 2w, 2z, and 2aj demonstrated potent antiviral activity in cell culture and exhibited efficacy in the cotton rat comparable to ribavirin. In a BALB/c mouse model, the oxadiazolone 2aj reduced virus titers following subcutaneous dosing, whilst the ester 2az and amide 2aab exhibited efficacy following oral administration. These results established the potential of this class of RSV fusion inhibitors to interfere with infection in vivo following topical or systemic administration.

Treatment of mannan-enhanced influenza B virus infections in mice with oseltamivir, ribavirin and viramidine

Mannan, a polysaccharide preparation from Saccharomyces cerevisiae, has previously been shown to enhance influenza virus replication in mice by inhibiting host defense collectins. The use of mannan in infections may serve to broaden the types of influenza viruses that can be studied in rodent infection models. When mannan was co-administered with influenza B/Sichuan/379/99 virus to mice, the animals died from the infection, whereas mice infected with only virus survived. Three types of influenza A (H1N1) and another influenza B (Hong Kong/330/01) virus infection were also enhanced by mannan, but not four types of influenza A (H3N2) viruses. Mannan was used at 0.16 or 0.5 mg/mouse for optimal disease-enhancing activity using influenza B/Sichuan/379/99 virus. Using this model, influenza B/Sichuan/379/99 infections were treated with oseltamivir, ribavirin or viramidine (the carboxamidine derivative of ribavirin). When oral gavage treatments started 4 h before virus and mannan challenge, oseltamivir was effective at 2.5, 5 and 10 mg/kg/day. Ribavirin was active at 20, 40 and 80 mg/kg/day. Viramidine was effective at 80 and 160 mg/kg/day but not at 40 mg/kg/day. Active drug doses improved lung consolidation scores and lung weights, with decreases in lung virus titres also noted. Arterial oxygen saturation values in treated groups were significantly better than those of the placebo group on days 7-11 of the infection. Oseltamivir (5 mg/kg/day) and ribavirin (40 mg/kg/day) were used alone and in combination to determine how late after infection they could be beneficially administered. Ribavirin alone was very effective (90-100% survival of mice) when treatments started as late as 3 days after infection. Forty percent survival was evident even when treatments started 4 days post-infection. Oseltamivir was active starting treatments 1 day after virus exposure, but lost considerable efficacy when treatments began after that time. The combination of ribavirin and oseltamivir appeared to be no better than ribavirin alone, due to the stronger beneficial effect of ribavirin in this model. The overall results demonstrate that mannan can be used to enhance certain non-lethal influenza virus infections sufficiently to allow antiviral studies.

Respiratory syncytial virus inhibitors. Part 2: Benzimidazol-2-one derivatives

Structure-activity relationships for a series of benzimidazol-2-one-based inhibitors of respiratory syncytial virus are described. These studies focused on structural variation of the benzimidazol-2-one substituent, a vector inaccessible in a series of benzotriazole derivatives on which 2 is based, and revealed a broad tolerance for substituent size and functionality.

Synthesis and anti-measles virus activity of new isoquinolin-4-one derivatives

Despite intense efforts to increase vaccine coverage, measles virus (MV) still causes significant morbidity and mortality in the world sometimes as a results of severe, chronic and lethal diseases. In an effort to develop therapies to supplement immunization strategies a number of 1-oxo-2-[[(1E)-phenylmethylene]amino]-1,2-dihydroisoquinoline-4-carboxylic acid derivatives were synthesized and evaluated for anti-measles activity. The substituents on the aromatic ring were chosen in order to evaluate the influence of electron-withdrawing or electron-donating effects on the electronic density of the aromatic moiety. We also evaluated the introduction of a vinyl chain between the exocyclic nitrogen and phenyl moiety. The biological results allow to outline some preliminary considerations on structure-activity relationship.

Comparison of the inhibition of human metapneumovirus and respiratory syncytial virus by ribavirin and immune serum globulin in vitro

Human metapneumovirus (hMPV) is a newly recognized pathogen that like its better-known relative, human respiratory syncytial virus (hRSV), appears to be ubiquitous and an important cause of respiratory disease in diverse subpopulations. No antivirals or vaccines are currently approved for the treatment or prevention of hMPV infections. However, ribavirin is licensed to treat serious hRSV-induced infections in children and immune globulin designed for intravenous administration (i.v.IG) and palivizumab (Synagis), a humanized monoclonal antibody preparation, have been utilized as alternatives to vaccines for preventing or reducing the severity of infections caused by this virus. Because both ribavirin and i.v.IG have broad viral specificities, studies were performed to compare the ability of these two agents to inhibit the replication of hRSV and hMPV in tissue culture-based assays. Two experimental chemotherapeutic agents (i.e. VP14637 and JNJ2408068) and different antibody preparations were included in this testing for comparison. Ribavirin and the i.v.IG utilized were found to have equivalent antiviral activity against hMPV and hRSV. In contrast, except for antisera specifically raised against hMPV, all of the other materials tested had marked activity only against hRSV.

Fundamental structure-activity relationships associated with a new structural class of respiratory syncytial virus inhibitor

Structure-activity relationships surrounding the dialkylamino side chain of a series of benzotriazole-derived inhibitors of respiratory syncytial virus fusion based on the screening lead 1a were examined. The results indicate that the topology of the side chain is important but the terminus element offers considerable latitude to modulate physical properties.

Comparison of corticosteroids for treatment of respiratory syncytial virus bronchiolitis and pneumonia in cotton rats

Triamcinolone acetonide, methylprednisolone, and dexamethasone were each evaluated in combination with palivizumab (Synagis) for the therapy of established respiratory syncytial virus infection in the cotton rat. Triamcinolone and methylprednisolone proved to be more effective than dexamethasone in reducing lung pathology. No recurrence of viral replication or pulmonary pathology followed the cessation of therapy.

Respiratory syncytial virus infection in patients with phagocyte defects

Patients with phagocyte defects frequently develop bacterial or fungal pneumonias, but they are not considered to be at increased risk for viral infections. We describe 3 patients with known phagocyte immunodeficiencies who developed lower respiratory tract infections (LRTI) caused by respiratory syncytial virus (RSV). All 3 patients had dense pneumonias as indicated by computed tomography scan of the lungs and RSV was recovered. We conclude that RSV can present as a dense pneumonia in patients with phagocyte defects. Along with common pathogens causing LRTI, RSV should be considered in the differential diagnosis. Viral cultures as well as rapid antigen detection assays for respiratory viruses should be included in the evaluation of LRTI in patients with phagocyte defects. respiratory syncytial virus, phagocyte, immunodeficiency, pneumonia.

Rehospitalization because of respiratory syncytial virus infection in premature infants younger than 33 weeks of gestation: a prospective study. IRIS Study Group

OBJECTIVE

To collect data on hospitalization for respiratory syncytial virus (RSV) infections and presumptive risk factors for rehospitalization among premature infants in Spain.

DESIGN

Observational, prospective, longitudinal, multicenter study.

SETTING

Fourteen Spanish neonatal units with an annual birth cohort of 57,000 infants.

PATIENTS

All children (n = 680) born < or =32 weeks of gestational age between April 1, 1998, and March 31, 1999, and discharged from the hospital before March 31, 1999, were included in the study. A total of 96 were excluded because of administration of prophylactic treatment (n = 55) or were lost to follow-up (n = 41). Five children died during the study period, but death was related to RSV in only 1 case.

METHODS AND MAIN OUTCOME MEASURES

Neonatal and demographic data were recorded at the initial visit. Infants were prospectively followed at monthly intervals up to March 31, 1999. In patients rehospitalized for respiratory disorders, further data about RSV status and morbidity were collected. A comparison was made between children rehospitalized for RSV infection and those who were not. The influence of factors on the probability of rehospitalization for RSV infection was assessed by logistic regression analysis.

RESULTS

Of the 584 evaluable patients 118 (20.2%) were rehospitalized for respiratory disease during the study period. The causative pathogen was identified in 89 (75.4%) hospital admissions. Of these 59 (66.3%) were a result of RSV infection in 53 children; 6 were reinfections. In a logistic regression model significant independent prognostic variables included: lower risk of RSV hospitalization with increase gestational age [odds ratio (OR), 0.85; 95% confidence interval (CI), 0.72 to 0.99; P < 0.047]; higher risk with chronic lung disease (OR = 3.1; 95% CI 1.22 to 7.91; P < 0.016); and living with school age siblings (OR = 1.86; 95% CI 1.01 to 3.4; P < 0.048).

CONCLUSION

This large descriptive study has enabled us to define the influence of specific risk factors that increase the risk of rehospitalization for RSV infection in preterm infants. Such studies help to define the appropriate role of available prophylactic interventions and establish treatment guidelines.

Respiratory syncytial virus: recent progress towards the discovery of effective prophylactic and therapeutic agents

Although respiratory syncytial virus (RSV) was discovered in 1955, the burden associated with this infectious agent on all population groups is only now beginning to be fully appreciated. The successful launch of the humanized monoclonal antibody Synagis (developed by MedImmune, Gaithersburg, MD, USA), as a prophylactic in September 1998 has helped to heighten awareness of the extent of mortality and morbidity associated with annual RSV epidemics. Small, drug-like molecules that would provide the clinician with effective and conveniently administered prophylactic and therapeutic agents for the prevention and treatment of RSV have not yet advanced into clinical studies. This review will summarize recent developments in the area of RSV drug discovery and development.

Use of cotton rats to evaluate the efficacy of antivirals in treatment of measles virus infections

No practical animal models for the testing of chemotherapeutic or biologic agents identified in cell culture assays as being active against measles virus (MV) are currently available. Cotton rats may serve this purpose. To evaluate this possibility, 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide (EICAR) and poly(acrylamidomethyl propanesulfonate) (PAMPS), two compounds that have been reported to inhibit MV in vitro, and ribavirin, an established antiviral drug with MV-inhibitory activity, were evaluated for their antiviral activities against MV and respiratory syncytial virus (RSV) in tissue culture and in hispid cotton rats. A single administration of PAMPS markedly inhibited pulmonary RSV or MV replication (>3 log(10) reduction in pulmonary titer compared to that for controls), but only if this compound was administered intranasally at about the time of virus inoculation. Both EICAR and ribavirin exhibited therapeutic activity against RSV and MV in cotton rats when they were administered parenterally. However, both of these compounds were less effective against MV. On the basis of the pulmonary virus titers on day 4 after virus inoculation, the minimal efficacious dose of EICAR against MV (120 mg/kg of body weight/day when delivered intraperitoneally twice daily) appeared to be three times lower against this virus than that of ribavirin delivered at a similar dose (i.e., 360 mg/kg/day). These findings correlated with those obtained in vitro. The data obtained suggest that cotton rats may indeed be useful for the initial evaluation of the activities of antiviral agents against MV.

Current and Future Use of Vaccines for Viral and Bacterial Respiratory Tract Infections

Viral and bacterial respiratory infections remain the number one cause of infectious disease-related deaths around the world. In the past, vaccines were often created by repeatedly passing laboratory cultures to develop attenuated strains or simply by inactivating live cultures of pathogens. A variety of new and innovative technologies are being applied to develop vaccines against the more elusive pathogens. A variety of protein conjugates have been used to greatly enhance the immunogenicity of Haemophilus influenzae type B vaccine, and are now being employed for new pneumococcal and meningococcal vaccines. Live attenuated vaccine strains of respiratory syncytial virus and influenza, which induce protective immunity through localized replication in the nasopharynx, may soon be available for routine use. Future innovations may include genetic vaccines that introduce DNA into host cells to produce specific protective antigens, along with a desired cytokine response to induce a protective immune response.

Aerosolized antimicrobial therapy in acutely ill patients

Recent data are sparking renewed interest in therapy with aerosolized antimicrobials in critically ill patients as well as other populations such as those with neutropenia, human immunodeficiency virus infection, and cystic fibrosis. Pneumonia is a common complication in these patients and is associated with substantial morbidity and increased mortality. Clinical trials evaluated aerosolized antimicrobials for the prevention and treatment of pneumonia in hospitalized patients. In addition, factors that affect the pulmonary deposition of aerosolized drugs in mechanically ventilated patients were identified.

Palivizumab: an overview

Respiratory syncytial virus (RSV) affects almost all children in their first 2 years of life and can cause severe or even life-threatening disease in some at-risk infants. Treatment is limited and there is currently no safe or effective vaccine. However, a new monoclonal antibody, palivizumab, reduces RSV hospitalization by 55% in at-risk groups if given prophylactically throughout the RSV season.

[Respiratory syncytial virus pneumonia in four immunocompromised adults]

INTRODUCTION

In hematologic malignancies, respiratory syncytial viral infections can be explained by neutropenia, and cellular and humoral immunodepression, and may cause severe respiratory infections.

EXEGESIS

Four patients with hematologic malignancies developed a severe respiratory syncytial virus infection. Three of them had previously received autologous bone marrow transplantation (ABMT). Progress was favorable for three patients. One patient died of acute respiratory failure.

CONCLUSION

When such patients present with respiratory symptoms, especially during the winter months, they should be screened for RSV. Bronchoalveolar lavage allowed quick and accurate diagnosis by immunofluorescence. Treatment with nebulized ribavirin is controversial. Its use may be interesting in patients with high-risk factors (intensive chemotherapy, ABMT, diffuse pneumonia with hypoxemia).

Chemotherapy of respiratory viruses: prospects and challenges

Billions of people are infected with respiratory viruses annually. Infants and young children, the elderly, immunocompromised individuals and those debilitated by other diseases or nutritional deficiencies are most at risk for serious disease. There are few vaccines available for use against these viruses, and even where there are (influenza, measles and adenovirus), infections remain common. The continued prevalence of respiratory virus infections has lead to renewed efforts to find safe agents effective against the most medically important respiratory viruses: influenza, respiratory syncytial, parainfluenza, measles, rhino- and adenovirus. Copyright 1999 Harcourt Publishers Ltd.

Respiratory syncytial virus (RSV) disease and prospects for its control

Respiratory syncytial virus (RSV) is a major virus pathogen of infants and young children, an important cause of disease in adults and is responsible for a significant amount of excess morbidity and mortality in the elderly. It also can be devastating in immunosuppressed populations. Vaccines are being developed, but none are currently licensed. Moreover, even if one or more are approved, they may not be suitable for some populations vulnerable to RSV (e.g. very young infants and the immunosuppressed). Ribavirin and immunoglobulin preparations with high titers of RSV-specific neutralizing antibodies are currently approved for use to treat and prevent RSV infection. However, neither of these is cost-effective or simple to administer. New agents are needed to reduce the impact of RSV. This review is concerned with the means currently available for controlling RSV, the search for new agents effective against this virus, and future prospects for preventing and treating RSV infections.