Predisposition of infants with chronic lung disease to respiratory syncytial virus-induced respiratory failure: a vascular hypothesis

CD8A is a Promising Biomarker Associated with Immunocytes Infiltration in Hyperoxia-Induced Bronchopulmonary Dysplasia

Background

Bronchopulmonary dysplasia (BPD) refers to a chronic lung disease which is commonly observed in preterm infants. It can usually be caused by several pathological processes that endanger the long-term lung development, such as inflammation and immune dysfunction.

Methods

In this study, a bioinformatics approach was applied to identify the differentially expressed immune-related genes (DEIRGs). We downloaded the transcriptional profiles (GSE32472 dataset) from the Gene Expression Omnibus (GEO) database and performed gene set enrichment analysis (GSEA). Cell type Identification By Estimating Relative Subsets of RNA Transcripts (CIBERSORT), microenvironment cell populations counter (MCPcounter), and Estimation of STromal and Immune cells in Malignant Tumor tissues using Expression data (ESTIMATE) were used for the analysis of the immune cell infiltration landscape of BPD. A weighted co-expression network was subsequently constructed using weighted gene co-expression network analysis (WGCNA) to screen candidate differentially expressed immune related genes (DEIRGs).

Results

GSEA results indicated that immune-related pathways were mainly involved in BPD. Ten significantly different immune cell types were observed between BPD and normal groups. A total of 228 DEGs in the turquoise module were identified, and 31 DEIRGs were further identified. Cluster of the differentiation 8 alpha (CD8A) expression was down-regulated in BPD, and its expression was validated by the GSE25286, GSE25293, GSE99633 datasets and qRT-PCR. In addition, CD8A expression was closely associated with immune cells infiltration, especially T cells CD8 and neutrophil.

Conclusion

A distinct immune cell infiltration landscape was found between BPD and normal group. CD8A can be a novel candidate biomarker for BPD, which plays an essential role in the onset and progress of hyperoxia-related BPD via the disruption of immune cell functions.

Safety and Feasibility of Riociguat Therapy for the Treatment of Chronic Pulmonary Arterial Hypertension in Infancy

The effects of riociguat, an oral-soluble guanylate-cyclase stimulator, were studied in 10 infants with chronic pulmonary arterial hypertension. Respiratory status (n = 8/10), right heart dilation (n = 7/10), function (n = 9/10), and chronic pulmonary arterial hypertension (n = 8/10) improved. Median decrement in systolic (12 [4, 14]), diastolic (14 [7, 20]), and mean arterial (14 [10, 17]) pressures were noted; no critical hypotension or hypoxemia occurred.

Respiratory Syncytial Virus-Associated Acute Lower Respiratory Infections in Children With Bronchopulmonary Dysplasia: Systematic Review and Meta-Analysis

BACKGROUND

Respiratory syncytial virus (RSV) is among the most important causes of acute lower respiratory tract infection (ALRI) in young children. We assessed the severity of RSV-ALRI in children less than 5 years old with bronchopulmonary dysplasia (BPD).

METHODS

We searched for studies using EMBASE, Global Health, and MEDLINE. We assessed hospitalization risk, intensive care unit (ICU) admission, need for oxygen supplementation and mechanical ventilation, and in-hospital case fatality (hCFR) among children with BPD compared with those without (non-BPD). We compared the (1) length of hospital stay (LOS) and (2) duration of oxygen supplementation and mechanical ventilation between the groups.

RESULTS

Twenty-nine studies fulfilled our inclusion criteria. The case definition for BPD varied substantially in the included studies. Risks were higher among children with BPD compared with non-BPD: RSV hospitalization (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.7-4.2; P < .001), ICU admission (OR, 2.9; 95% CI, 2.3-3.5; P < .001), need for oxygen supplementation (OR, 4.2; 95% CI, .5-33.7; P = .175) and mechanical ventilation (OR, 8.2; 95% CI, 7.6-8.9; P < .001), and hCFR (OR, 12.8; 95% CI, 9.4-17.3; P < .001). Median LOS (range) was 7.2 days (4-23) (BPD) compared with 2.5 days (1-30) (non-BPD). Median duration of oxygen supplementation (range) was 5.5 days (0-21) (BPD) compared with 2.0 days (0-26) (non-BPD). The duration of mechanical ventilation was more often longer (>6 days) in those with BPD compared with non-BPD (OR, 11.9; 95% CI, 1.4-100; P = .02).

CONCLUSIONS

The risk of severe RSV disease is considerably higher among children with BPD. There is an urgent need to establish standardized BPD case definitions, review the RSV prophylaxis guidelines, and encourage more specific studies on RSV infection in BPD patients, including vaccine development and RSV-specific treatment.

Severe respiratory syncytial virus disease in preterm infants: a case of innate immaturity

Respiratory syncytial virus (RSV) is the most common viral pathogen associated with acute lower respiratory tract infection (LRTI) in children under 5 years of age. Severe RSV disease is associated with the development of chronic respiratory complications such as recurrent wheezing and asthma. A common risk factor for developing severe RSV disease is premature gestation and this is largely due to an immature innate immune system. This increases susceptibility to RSV since the innate immune system is less able to protect against pathogens at a time when adaptive immunity has not fully developed. This review focuses on comparing different aspects of innate immunity between preterm and term infants to better understand why preterm infants are more susceptible to severe RSV disease. Identifying early life innate immune biomarkers associated with the development of severe RSV disease, and understanding how these compare between preterm and term infants, remains a critically important question that would aid the development of interventions to reduce the burden of disease in this vulnerable population.

Comparative two time-point proteome analysis of the plasma from preterm infants with and without bronchopulmonary dysplasia

BACKGROUND

In this study, we aimed to analyze differences in plasma protein abundances between infants with and without bronchopulmonary dysplasia (BPD), to add new insights into a better understanding of the pathogenesis of this disease.

METHODS

Cord and peripheral blood of neonates (≤ 30 weeks gestational age) was drawn at birth and at the 36th postmenstrual week (36 PMA), respectively. Blood samples were retrospectively subdivided into BPD(+) and BPD(-) groups, according to the development of BPD.

RESULTS

Children with BPD were characterized by decreased afamin, gelsolin and carboxypeptidase N subunit 2 levels in cord blood, and decreased galectin-3 binding protein and hemoglobin subunit gamma-1 levels, as well as an increased serotransferrin abundance in plasma at the 36 PMA.

CONCLUSIONS

BPD development is associated with the plasma proteome changes in preterm infants, adding further evidence for the possible involvement of disturbances in vitamin E availability and impaired immunological processes in the progression of prematurity pulmonary complications. Moreover, it also points to the differences in proteins related to infection resistance and maintaining an adequate level of hematocrit in infants diagnosed with BPD.

Immune System Regulation Affected by a Murine Experimental Model of Bronchopulmonary Dysplasia: Genomic and Epigenetic Findings

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common cause of abrupted lung development after preterm birth. BPD may lead to increased rehospitalization, more severe and frequent respiratory infections, and life-long reduced lung function. The gene regulation in lungs with BPD is complex, with various genetic and epigenetic factors involved.

OBJECTIVES

The aim of this study was to examine the regulatory relation between gene expression and the epigenome (DNA methylation) relevant for the immune system after hyperoxia followed by a recovery period in air using a mouse model of BPD.

METHODS

Newborn mice pups were subjected to an immediate hyperoxic condition from birth and kept at 85% O2 levels for 14 days followed by a 14-day period in room air. Next, mice lung tissue was used for RNA and DNA extraction with subsequent microarray-based assessment of lung transcriptome and supplementary methylome analysis.

RESULTS

The immune system-related transcriptomeregulation was affected in mouse lungs after hyperoxia. A high proportion of genes relevant in the immune system exhibited significant expression alterations, e.g., B cell-specific genes central to the cytokine-cytokine receptor interaction, the PI3K-AKT, and the B cell receptor signaling pathways. The findings were accompanied by significant DNA hypermethylation observed in the PI3K-AKT pathway and immune system-relevant genes.

CONCLUSIONS

Oxygen damage could be partly responsible for the increased susceptibility and abnormal response to respiratory viruses and infections seen in premature babies with BPD through dysregulated genes.

Bronchopulmonary Dysplasia: An Update of Current Pharmacologic Therapies and New Approaches

Bronchopulmonary dysplasia (BPD) remains the most prevalent long-term morbidity of surviving extremely preterm infants and is associated with significant health care utilization in infancy and beyond. Recent advances in neonatal care have resulted in improved survival of extremely low birth weight (ELBW) infants; however, the incidence of BPD has not been substantially impacted by novel interventions in this vulnerable population. The multifactorial cause of BPD requires a multi-pronged approach for prevention and treatment. New approaches in assisted ventilation, optimal nutrition, and pharmacologic interventions are currently being evaluated. The focus of this review is the current state of the evidence for pharmacotherapy in BPD. Promising future approaches in need of further study will also be reviewed.

New mouse model of pulmonary hypertension induced by respiratory syncytial virus bronchiolitis

Pulmonary hypertension (PH) has been observed in up to 75% of infants with moderate to severe respiratory syncytial virus (RSV) bronchiolitis and is associated with significant morbidity and mortality in infants with congenital heart disease. The purpose of the present study was to establish a mouse model of PH secondary to RSV bronchiolitis that mimics the disease etiology as it occurs in infants. Neonatal mice were infected with RSV at 5 days of age and then reinfected 4 wk later. Serum-free medium was administered to age-matched mice as a control. Echocardiography and right ventricular systolic pressure (RVSP) measurements via right jugular vein catheterization were conducted 5 and 6 days after the second infection, respectively. Peripheral capillary oxygen saturation monitoring did not indicate hypoxia at 2-4 days post-RSV infection, before reinfection, and at 2-7 days after reinfection. RSV-infected mice had significantly higher RVSP than control mice. Pulsed-wave Doppler recording of the pulmonary blood flow by echocardiogram demonstrated a significantly shortened pulmonary artery acceleration time and decreased pulmonary artery acceleration time-to-ejection time ratio in RSV-infected mice. Morphometry showed that RSV-infected mice exhibited a significantly higher pulmonary artery medial wall thickness and had an increased number of muscularized pulmonary arteries compared with control mice. These findings, confirmed by RVSP measurements, demonstrate the development of PH in the lungs of mice infected with RSV as neonates. This animal model can be used to study the pathogenesis of PH secondary to RSV bronchiolitis and to assess the effect of treatment interventions. NEW & NOTEWORTHY This is the first mouse model of respiratory syncytial virus-induced pulmonary hypertension, to our knowledge. This model will allow us to decipher molecular mechanisms responsible for the pathogenesis of pulmonary hypertension secondary to respiratory syncytial virus bronchiolitis with the use of knockout and/or transgenic animals and to monitor therapeutic effects with echocardiography.

Respiratory virus prophylaxis in congenital heart disease

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections and causes up to 200,000 infant deaths a year worldwide. The average rate of hospitalization for severe RSV infection is 5 per 1000 children, and the rate is three-times higher in those with congenital heart disease (CHD). Palivizumab, a monoclonal antibody, reduces hospitalization rates and intensive care admissions. It is used prophylactically and is administered as monthly doses during the RSV season. Hemodynamically unstable CHD is the most susceptible CHD to a severe episode of RSV infection. This review explores current evidence surrounding therapies, patterns of infection and identifies groups which may still be vulnerable to severe RSV infection.

Health Care and Societal Costs of Bronchopulmonary Dysplasia

Despite significant technological advances and increasing survival of premature infants, bronchopulmonary dysplasia (BPD) continues to be the most prevalent major morbidity in surviving very low-birthweight infants. Infants with BPD are often sicker, require longer stays in the NICU, and accumulate greater hospital costs. However, care of the infant with BPD extends beyond the time spent in the NICU. This article reviews the costs of BPD in the health-care setting, during the initial hospitalization and beyond, and the long-term neurodevelopmental impact of BPD, as well as the impact on a family caring for a child with BPD.

CHD and respiratory syncytial virus: global expert exchange recommendations

BACKGROUND

Palivizumab is the standard immunoprophylaxis against serious disease due to respiratory syncytial virus infection. Current evidence-based prophylaxis guidelines may not address certain children with CHD within specific high-risk groups or clinical/management settings.

METHODS

An international steering committee of clinicians with expertise in paediatric heart disease identified key questions concerning palivizumab administration; in collaboration with an additional international expert faculty, evidence-based recommendations were formulated using a quasi-Delphi consensus methodology.

RESULTS

Palivizumab prophylaxis was recommended for children with the following conditions: <2 years with unoperated haemodynamically significant CHD, who are cyanotic, who have pulmonary hypertension, or symptomatic airway abnormalities; <1 year with cardiomyopathies requiring treatment; in the 1st year of life with surgically operated CHD with haemodynamically significant residual problems or aged 1-2 years up to 6 months postoperatively; and on heart transplant waiting lists or in their 1st year after heart transplant. Unanimous consensus was not reached for use of immunoprophylaxis in children with asymptomatic CHD and other co-morbid factors such as arrhythmias, Down syndrome, or immunodeficiency, or during a nosocomial outbreak. Challenges to effective immunoprophylaxis included the following: multidisciplinary variations in identifying candidates with CHD and prophylaxis compliance; limited awareness of severe disease risks/burden; and limited knowledge of respiratory syncytial virus seasonal patterns in subtropical/tropical regions.

CONCLUSION

Evidence-based immunoprophylaxis recommendations were formulated for subgroups of children with CHD, but more data are needed to guide use in tropical/subtropical countries and in children with certain co-morbidities.

Looking ahead: where to next for animal models of bronchopulmonary dysplasia?

Bronchopulmonary dysplasia (BPD) is the most common complication of preterm birth, with appreciable morbidity and mortality in a neonatal intensive care setting. Much interest has been shown in the identification of pathogenic pathways that are amenable to pharmacological manipulation (1) to facilitate the development of novel therapeutic and medical management strategies and (2) to identify the basic mechanisms of late lung development, which remains poorly understood. A number of animal models have therefore been developed and continue to be refined with the aim of recapitulating pathological pulmonary hallmarks noted in lungs from neonates with BPD. These animal models rely on several injurious stimuli, such as mechanical ventilation or oxygen toxicity and infection and sterile inflammation, as applied in mice, rats, rabbits, pigs, lambs and nonhuman primates. This review addresses recent developments in modeling BPD in experimental animals and highlights important neglected areas that demand attention. Additionally, recent progress in the quantitative microscopic analysis of pathology tissue is described, together with new in vitro approaches of value for the study of normal and aberrant alveolarization. The need to examine long-term sequelae of damage to the developing neonatal lung is also considered, as is the need to move beyond the study of the lungs alone in experimental animal models of BPD.

Recent advances in the mechanisms of lung alveolarization and the pathogenesis of bronchopulmonary dysplasia

Alveolarization is the process by which the alveoli, the principal gas exchange units of the lung, are formed. Along with the maturation of the pulmonary vasculature, alveolarization is the objective of late lung development. The terminal airspaces that were formed during early lung development are divided by the process of secondary septation, progressively generating an increasing number of alveoli that are of smaller size, which substantially increases the surface area over which gas exchange can take place. Disturbances to alveolarization occur in bronchopulmonary dysplasia (BPD), which can be complicated by perturbations to the pulmonary vasculature that are associated with the development of pulmonary hypertension. Disturbances to lung development may also occur in persistent pulmonary hypertension of the newborn in term newborn infants, as well as in patients with congenital diaphragmatic hernia. These disturbances can lead to the formation of lungs with fewer and larger alveoli and a dysmorphic pulmonary vasculature. Consequently, affected lungs exhibit a reduced capacity for gas exchange, with important implications for morbidity and mortality in the immediate postnatal period and respiratory health consequences that may persist into adulthood. It is the objective of this Perspectives article to update the reader about recent developments in our understanding of the molecular mechanisms of alveolarization and the pathogenesis of BPD.

Is radiological appearance of lower respiratory tract infection due to respiratory syncytial virus a predictor of clinical outcome?

OBJECTIVE

Respiratory syncytial virus (RSV) lower respiratory tract infection is the most common viral infection in childhood. RSV-infected infants demonstrate various radiographic findings. The aim of the study is to evaluate whether assessment of radiological characteristics of lower tract infection due to RSV may be a predictor of clinical outcome in newborns.

METHODS

The study included 36 newborn infants hospitalized for lower tract infection. In order to detect RSV, RSV Respi-Strip (Coris Bioconcept Organization) test kits were used on admission. Chest X-rays and clinical characteristics of the study group were reviewed.

RESULTS

Of 36 patients hospitalized for lower tract infection from October 2012 to April 2013, 18 (50%) newborns were infected with RSV. The study included 36 neonates. Patients with RSV-positive infants at admission had greater need for respiratory support, supplemental oxygen and prolonged stay in the NICU. Newborns with an atelectasis pattern on admission chest radiograph had greater at RSV-positive infants.

CONCLUSION

Chest radiological patterns with lower respiratory tract infection in newborn infants due to RSV are a predictor of clinical outcome.

Metyrapone alleviates deleterious effects of maternal food restriction on lung development and growth of rat offspring

Maternal food restriction (MFR) causes intrauterine growth restriction, a known risk factor for developing chronic lung disease. However, it is unknown whether this negative outcome is gender specific or preventable by blocking the MFR-induced hyperglucocorticoidism. Using a well-established rat model, we used metyrapone (MTP), an inhibitor of glucocorticoid synthesis, to study the MFR-induced lung changes on postnatal day (p) 21 in a gender-specific manner. From embryonic day 10 until delivery, pregnant dams were fed either an ad libitum diet or a 50% caloric restricted diet with or without MTP supplementation. Postnatally, the offspring were fed ad libitum from healthy dams until p21. Morphometric, Western blot, and immunohistochemical analysis of the lungs demonstrated that MTP mitigated the MFR-mediated decrease in alveolar count, decrease in adipogenic protein peroxisome proliferator-activated receptor γ, increase in myogenic proteins (fibronectin, α-smooth muscle actin, and calponin), increase in Wnt signaling intermediates (lymphoid enhancer-binding factor 1 and β-catenin), and increase in glucocorticoid receptor (GR) levels. The MFR-induced lung phenotype and the effects of MTP were similar in both genders. To elucidate the mechanism of MFR-induced shift of the adipogenic-to-myogenic phenotype, lung fibroblasts were used to independently study the effects of (1) nutrient restriction and (2) excess steroid exposure. Nutrient deprivation increased myogenic proteins, Wnt signaling intermediates, and GR, all changes blocked by protein supplementation. MTP also blocked, likely by normalizing nicotinamide adenine dinucleotide phosphate levels, the corticosterone-induced increase in myogenic proteins, but had no effect on GR levels. In summary, protein restriction and increased glucocorticoid levels appear to be the key players in MFR-induced lung disease, affecting both genders.

Respiratory syncytial virus detection in cells and clinical samples by using three new monoclonal antibodies

Acute respiratory infections caused by the respiratory syncytial virus (RSV) are important health burdens that affect infants worldwide. RSV is also an important cause of morbidity and disease in adults, which causes enormous economic losses. At the present time, RSV infection is diagnosed by immunofluorescence, test pack and/or PCR, obtaining better results with PCR than with any other technique. The production of new monoclonal antibodies (mAbs) capable of detecting RSV in clinical samples is necessary to generate better and faster diagnosis tools for RSV. In this study, three new mAbs, directed against the RSV N and M2-1 proteins, were evaluated for the detection of RSV in clinical samples. Nasopharyngeal swabs were obtained from: 27 RSV-positive patients; 15 human metapneumovirus (hMPV)-positive patients; and 6 healthy controls. To evaluate RSV presence in these samples, clinical samples and RSV-infected cells were tested by Enzyme-Linked ImmunoSorbent Assay (ELISA), flow cytometry, immunofluorescence, and dot-blot assays. Specificity and sensitivity were determined for each mAb by using purified RSV antigens and antigens from different viruses. Infected cells and clinical samples tested with the three new mAbs resulted positive by immunofluorescence, ELISA, flow cytometry, and dot blot. No false positives were obtained in samples infected with other respiratory virus (hMPV) or from healthy controls. These results suggest that these new anti-RSV mAbs can be considered for the rapid and reliable detection of RSV on infected cells and clinical specimens by multiple immunological approaches.

Should respiratory care in preterm infants include prophylaxis against respiratory syncytial virus infection? The case in favour

Respiratory syncytial virus (RSV) is the most significant cause of acute respiratory tract infections (RTI) in infants and young children throughout the world. Preterm infants are at increased risk for severe RSV lower respiratory tract infection due to small lung volumes, a reduced lung surface area, small airways and an increased air space wall thickness. Additionally, the airways of preterm infants have been ventilated mechanically and suctioned and potentially damaged by many microtraumas with disruption of endothelial surfaces enabling pathogens to invade more easily. The immune system of preterm infants is immature resulting in low antibody titers (incomplete transplacental transfer of maternal antibodies) and a reduced cellular immunity with reduced viral clearance. Rehospitalization rates of preterm compared to term infants due to RSV infection are increased as are total morbidity and mortality associated with RSV disease. Palivizumab effectively reduces RSV related rehospitalisation in this high-risk population.

[Bronchopulmonary dysplasia-associated pulmonary arterial hypertension of very preterm infants]

Bronchopulmonary dysplasia (BPD) of very preterm infants is a multifactorial chronic lung disease and its incidence has not decreased despite improvements in neonatal intensive care, including lung protective strategies. Pulmonary hypertension (PH) can complicate the course of BPD. Mortality in infants with BPD-associated PH is thought to be very high, but its incidence is unknown and a standard diagnostic and therapeutic strategy has not been well defined. In this article, we will first describe the current knowledge on the BPD-associated PH and the current treatments available for this pathology. We will then present the HTP-DBP Study, carried out in Paris (France) starting in 2012. The diagnosis of PH is suspected on echocardiographic criteria, but cardiac catheterization is considered the gold standard for diagnosis and evaluation of the severity of PH. Moreover, pulmonary vasoreactivity testing is used to guide the management of patients with PH. The pathogenesis of BPD-associated PH is poorly understood and even less is known about appropriate therapy. Today, optimizing ventilation and reducing the pulmonary vascular tone with specific pulmonary vasodilatator drugs are the main goals in treating HTP-associated DBP. Animal studies and a few clinical studies suggest that medications targeting the nitric oxide (NO) signaling pathway (NO inhalation, oral sildenafil citrate) could be effective treatments for BPD-associated PH, but they have not been approved for this indication. The HTP-DBP study is a French multicenter prospective observational study. The objective is to evaluate the frequency of BPD-associated PH, to describe its physiopathology, its severity (morbidity and mortality), and the effectiveness of current treatments.

Inhibiting NF-κB in the developing lung disrupts angiogenesis and alveolarization

Bronchopulmonary dysplasia (BPD), a chronic lung disease of infancy, is characterized by arrested alveolar development. Pulmonary angiogenesis, mediated by the vascular endothelial growth factor (VEGF) pathway, is essential for alveolarization. However, the transcriptional regulators mediating pulmonary angiogenesis remain unknown. We previously demonstrated that NF-κB, a transcription factor traditionally associated with inflammation, plays a unique protective role in the neonatal lung. Therefore, we hypothesized that constitutive NF-κB activity is essential for postnatal lung development. Blocking NF-κB activity in 6-day-old neonatal mice induced the alveolar simplification similar to that observed in BPD and significantly reduced pulmonary capillary density. Studies to determine the mechanism responsible for this effect identified greater constitutive NF-κB in neonatal lung and in primary pulmonary endothelial cells (PEC) compared with adult. Moreover, inhibiting constitutive NF-κB activity in the neonatal PEC with either pharmacological inhibitors or RNA interference blocked PEC survival, decreased proliferation, and impaired in vitro angiogenesis. Finally, by chromatin immunoprecipitation, NF-κB was found to be a direct regulator of the angiogenic mediator, VEGF-receptor-2, in the neonatal pulmonary vasculature. Taken together, our data identify an entirely novel role for NF-κB in promoting physiological angiogenesis and alveolarization in the developing lung. Our data suggest that disruption of NF-κB signaling may contribute to the pathogenesis of BPD and that enhancement of NF-κB may represent a viable therapeutic strategy to promote lung growth and regeneration in pulmonary diseases marked by impaired angiogenesis.

Current pharmacologic approaches for prevention and treatment of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a major complication of preterm birth and has serious adverse long-term health consequences. The etiology of BPD is complex, multifactorial, and incompletely understood. Contributing factors include ventilator-induced lung injury, exposure to toxic oxygen levels, and infection. Several preventive and therapeutic strategies have been developed with variable success. These include lung protective ventilator strategies and pharmacological and nutritional interventions. These strategies target different components and stages of the disease process and they are commonly used in combination. The purpose of this review is to discuss the evidence for current pharmacological interventions and identify future therapeutic modalities that appear promising in the prevention and management of BPD. Continued improved understanding of BPD pathogenesis leads to opportunities for newer preventive approaches. These will need to be evaluated in the setting of current clinical practice in order to assess their efficacy.

Epidemiology and prevention of respiratory syncytial virus infections among infants and young children

Since its discovery in 1956, respiratory syncytial virus (RSV) has been recognized as one of the most common causes of serious lower respiratory tract infections in young children worldwide. While considered a high priority, development of a safe and effective vaccine has remained elusive. Prevention of RSV disease relies on infection control and hygiene measures, as well as providing immunoprophylaxis in select infants. The prophylaxis, however, is costly, and so targeting the recipient population and timing of administration is important for optimal effectiveness and judicious use of limited health care resources. This article reviews the epidemiology of RSV infections in infants and young children, including risk factors for severe disease, so as to inform decisions about prevention efforts.

Pattern recognition receptors and genetic risk for rsv infection: value for clinical decision-making?

Respiratory syncytial virus (RSV) causes respiratory tract infections, especially among young infants. Practically, all infants are infected during epidemics and the clinical presentation ranges from subclinical to fatal infection. Known risk factors for severe RSV infection include prematurity, age of <2 months, underlying chronic lung or heart diseases, serious neurological or metabolic disorders, immune deficiency (especially a disorder of cellular immunity), crowded living conditions, and indoor smoke pollution. Twin studies indicate that host genetic factors affect susceptibility to severe RSV infection. Pattern recognition receptors (PRRs) are the key mediators of the innate immune response to RSV. In the distal respiratory tract, RSV is recognized by the transmembrane Toll-like receptor 4 (TLR4) and adapter proteins, which lead to production of proinflammatory cytokines and subsequent activation of the adaptive immune response. Surfactant proteins A and D are able to bind both RSV and TLR4, modulating the inflammatory response. Genetic variations in TLR4, SP-A, and SP-D have been associated with the risk of severe RSV bronchiolitis, but the results have varied between studies. Both the homozygous hyporesponsive 299Gly genotype of TLR4 and the non-synonymous SP-A and SP-D polymorphism influence the presentation of RSV infection. The reported relative risks associated with these markers are not robust enough to justify clinical use. However, current evidence indicates that innate immune responses including pattern recognition receptors (PRRs) and other components in the distal airways and airspaces profoundly influence the innate immune responses, playing a key role in host resistance to RSV in young infants. This information is useful in guiding efforts to develop better means to identify the high-risk infants and to treat this potentially fatal infection effectively.

Genetic diversity of the host and severe respiratory syncytial virus-induced lower respiratory tract infection

Respiratory syncytial virus (RSV)-induced lower respiratory tract disease is a common problem in children and adults in Western societies. The clinical range of RSV infection from asymptomatic to respiratory distress syndrome is believed to be the outcome of viral and host immunity interactions. Genes associated with immune response are of particular interest regarding genetic predisposition to severe RSV infection. Several investigators have sought to identify genetic markers for high-risk patients, and more than 20 independent studies in the medical literature assess the impact of genetic variations-mostly single nucleotide polymorphisms-on the clinical presentation of RSV-induced disease. Several candidate gene loci have been tested in association studies based on the concept that a particular allele is a significant risk factor for a phenotype of interest. Despite the wealth of information available, we are still far from evolving a practical and cost-effective screening tool; certain flaws in association studies first need to be overcome. The development of haplotype-based analysis for candidate loci across the genome, along with advances in biostatistics and bioinformatics, would facilitate the assessment of the relative contribution of genetic markers to disease susceptibility in RSV infection.

Wheezing illness caused by respiratory syncytial virus and other agents

BACKGROUND

Respiratory syncytial virus (RSV) and other pathogenic agents cause lower respiratory infection with wheezing in infants (wheezing illness in infancy). Wheezing illness in infancy due to RSV can be life-threatening and can induce recurrent wheezing; but these events can also be produced by infection by other pathogenic agents. Thus, whether RSV induces more severe wheezing illness in infancy remains poorly understood.

METHODS

Infants with an initial wheezing illness were divided into an RSV-positive group and an RSV-negative group and the differences in disease severity, intensity of acute symptoms, and susceptibility to recurrent wheezing, between these two groups, were investigated.

RESULTS

The RSV-positive group accounted for 57.4% of the infants. The infants in the RSV-positive group were significantly younger than those in the RSV-negative group. Other background parameters, gender and family history, were not significantly different. There were no significant differences in indicators of severity (hospitalization periods, periods of persistent wheezing and requirement of oxygen supplementation) between the two groups.

CONCLUSION

Wheezing illness in infancy caused by RSV is more common in younger infants, but it is not more severe than that caused by other pathogenic agents.

Palivizumab and the prevention of respiratory syncytial virus illness in pediatric patients with congenital heart disease

Respiratory syncytial virus (RSV) is a significant pathogen for infants and children with congenital heart disease. Non-sustained immunity and failure to develop an effective vaccine has steered RSV management toward a passive immunotherapy strategy in at-risk children. Palivizumab is a humanized murine monoclonal antibody targeting the RSV envelope F glycoprotein. In a Phase III clinical trial palivizumab significantly reduced RSV hospitalization in children with significant congenital heart disease and was proven to be safe. Palivizumab is one of the first monoclonal antibodies to significantly impact a pediatric disease.

Respiratory health in prematurely born preschool children with and without bronchopulmonary dysplasia

OBJECTIVE

To investigate the respiratory health of preterm infants with bronchopulmonary dysplasia (BPD) at preschool age and to determine whether lung function (measured by forced oscillation technique (FOT) and interruption technique (Rint) is affected by BPD in preterm infants compared with preterm infants without BPD.

PARTICIPANTS

3 to 5 years of age born preterm with BPD (N = 40, mean gestational age 28 weeks, mean birth weight 1051 g), and without BPD (N = 36, mean gestational age 29 weeks, mean birth weight 1179 g).

OUTCOME VARIABLES

prevalence of symptoms determined by European Community Respiratory Health Survey and lung function measured by FOT and Rint.

RESULTS

A large percentage of infants in both preterm groups reported respiratory symptoms during the last 12 months. Lung function measurements showed higher resonant frequency (Hz) in BPD compared with non-BPD (mean 26.8 vs 22.7, P < .001) and lower mean reactance X(4-24) (hPa.s/l)(-3.0 vs -1.9, P = .005). No differences were found in respiratory resistance between the groups, although the mean values of both groups were increased compared with reference values.

CONCLUSION

Preterm birth affects respiratory health at 3 to 5 years of age. Children with BPD could be distinguished from children without BPD based on a higher resonant frequency and a lower mean reactance.

Follow-up of a randomized, placebo-controlled trial of postnatal dexamethasone: blood pressure and anthropometric measurements at school age

OBJECTIVE

The purpose of this work was to evaluate the effects of a 42-day tapering course of dexamethasone on blood pressure and anthropometric measurements in school-age children who were born with very low birth weight.

METHODS

Sixty-eight children, who as neonates participated in a randomized placebo-controlled trial of a 42-day tapering course of dexamethasone (n = 38, dexamethasone; n = 30, placebo) to facilitate weaning from the ventilator, were seen at a median of 9 years of age. Participants underwent measurements of systolic blood pressure, diastolic blood pressure, mid-arm circumference, triceps skinfold thickness, height, and weight. Mann-Whitney U tests were used to compare groups, and Spearman coefficients were used to examine correlations between variables.

RESULTS

Comparing dexamethasone- and placebo-treated children, we found no differences in systolic blood pressure, mid-arm circumference, triceps skinfold thickness, height, weight, or body mass index. Twenty-nine percent of all subjects had systolic blood pressure and/or diastolic blood pressure > or = 90th percentile for age and gender. Thirty percent of all subjects had body mass index > or = 85th percentile for age and gender.

CONCLUSIONS

In a group of preterm very low birth-weight infants at high risk for chronic lung disease, we found no effects of dexamethasone on blood pressure or anthropometric measurements at 8 to 11 years of age. Of concern is that a high proportion in this sample had blood pressure > or = 90th percentile and/or body mass index > or = 85th percentile.

The current state of infection with respiratory syncytial virus in the setting of congenital cardiac malformations

A long with prematurity and chronic lung disease, the presence of congenital cardiac disease in infants and young children is a significant risk for the clinical consequences of an illness produced by infection with the respiratory syncytial virus.1In this review, we present a current understanding of such illnesses, their prevention, and their treatment.

Pharmacological strategies in the prevention and management of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a disease of complex and multifactorial etiology and a major cause of morbidity in premature infants. Contributing factors include infection, exposure to toxic oxygen levels, and ventilator-induced lung injury, resulting in arrested lung development and impaired lung function. Several preventive and therapeutic strategies have been employed and include lung protective ventilator strategies, pharmacological and nutritional interventions. These strategies target different components and stages of the disease process, and their success has been variable. This review intends to bring together prior and current pharmacological interventions and future therapeutic modalities that appear promising in the prevention and management of BPD. Better understanding of the pathogenesis has given hope for newer treatment options. Newer studies need to be designed to assess the efficacy of combination therapies that target multiple steps of the disease process.

T280M variation of the CX3C receptor gene is associated with increased risk for severe respiratory syncytial virus bronchiolitis

BACKGROUND

Recent data suggest that immunologic response during respiratory syncytial virus (RSV) infection is partially modified through interaction of viral G glycoprotein with the host's chemokine receptor, CX3CR1. We hypothesized that two nonsynonymous, single-nucleotide polymorphisms of the CX3CR1 gene (CX3CR1-V249I and CX3CR1-T280M) that disrupt the affinity of CX3CR1 for its natural ligand (fractalkine) could also affect the G glycoprotein-CX3CR1 pathway.

METHODS

To test the hypothesis, DNA samples were obtained from 82 children hospitalized for RSV bronchiolitis in a 1-year period. One hundred twenty sex-matched healthy adults, without a history of severe lower respiratory tract infections, formed the control group.

RESULTS

Epidemiologic data showed an increase in the RSV infection rate during the late winter season, with a peak rate in early spring. Genotyping revealed predominance of the 280M-containing genotypes (M/M or T/M) in cases compared with controls (37.8% versus 20.8%, respectively; odds ratio, 2.03; 95% confidence interval, 1.1-3.9; P = 0.025), demonstrating an association between the common CX3CR1-T280M variations and increased risk of severe RSV bronchiolitis.

CONCLUSIONS

Our findings support the hypothesis of the pivotal role of the G glycoprotein CX3CR1 pathway in the pathogenesis of RSV bronchiolitis and propose CX3CR1 as a potential therapeutic target.

Acute and long-term effects of infection by the respiratory syncytial virus in children with congenital cardiac malformations

All newborn infants have limited pulmonary reserve compared with older children. This puts them at increased risk of respiratory complications, such as those associated with infection by the respiratory syncytial virus. Young children with congenital cardiac disease are particularly likely to suffer severe disease related to infection by the virus. In these children, the extreme vulnerability of the lung to pulmonary oedema is compounded by the additional burden caused by the respiratory syncytial virus. In addition to the well-documented acute pulmonary effects of infection with the respiratory syncytial virus, there may also be consequent long-term respiratory morbidity. Clinical studies have shown that infection by the virus in infancy is associated with a higher risk of developing subsequent bronchial obstructive disease. Much debate surrounds the mechanisms underlying this association. It is thought that a combined immunological and neurogenic response mechanism is likely. Prevention of severe respiratory disease in infants and young children with congenital heart disease due to infection by the virus may, therefore, offer both immediate and long-term benefits. Indeed, an increasing body of evidence supports this hypothesis, indicating a clinical rationale for prophylaxis against the virus in infancy, in order to reduce the chance of developing reactive airways disease and asthma in later life.