Viral Specific Factors Contribute to Clinical Respiratory Syncytial Virus Disease Severity Differences in Infants

All Eyes on the Prefusion-Stabilized F Construct, but Are We Missing the Potential of Alternative Targets for Respiratory Syncytial Virus Vaccine Design?

Respiratory Syncytial Virus (RSV) poses a significant global health concern as a major cause of lower respiratory tract infections (LRTIs). Over the last few years, substantial efforts have been directed towards developing vaccines and therapeutics to combat RSV, leading to a diverse landscape of vaccine candidates. Notably, two vaccines targeting the elderly and the first maternal vaccine have recently been approved. The majority of the vaccines and vaccine candidates rely solely on a prefusion-stabilized conformation known for its highly neutralizing epitopes. Although, so far, this antigen design appears to be successful for the elderly, our current understanding remains incomplete, requiring further improvement and refinement in this field. Pediatric vaccines still have a long journey ahead, and we must ensure that vaccines currently entering the market do not lose efficacy due to the emergence of mutations in RSV's circulating strains. This review will provide an overview of the current status of vaccine designs and what to focus on in the future. Further research into antigen design is essential, including the exploration of the potential of alternative RSV proteins to address these challenges and pave the way for the development of novel and effective vaccines, especially in the pediatric population.

An impact of age on respiratory syncytial virus infection in air-liquid-interface culture bronchial epithelium

Background

Elderly people are known to be vulnerable to virus infection. However, this has not been appropriately tested in in vitro studies due to a lack of appropriate virus infection models. In this report, we investigated the impact of age on respiratory syncytial virus (RSV) in pseudostratified air-liquid-interface (ALI) culture bronchial epithelium, which more closely mimic human airway epithelium morphologically and physiologically, than submerged cancer cell line cultures.

Methods

RSV A2 was inoculated apically to the bronchial epithelium obtained from 8 donors with different ages (28–72 years old), and time-profiles of viral load and inflammatory cytokines were analyzed.

Results

RSV A2 replicated well in ALI-culture bronchial epithelium. The viral peak day and peak viral load were similar between donors at ≤60 years old (n = 4) and  > 65 years old (n = 4; elderly group), but virus clearance was impaired in the elderly group. Furthermore, area under the curve (AUC) analysis, calculated from viral load peak to the end of sample collection (from Day 3 to 10 post inoculation), revealed statistically higher live viral load (PFU assay) and viral genome copies (PCR assay) in the elderly group, and a positive correlation between viral load and age was observed. In addition, the AUCs of RANTES, LDH, and dsDNA (cell damage marker) were statistically higher in the elderly group, and the elderly group showed a trend of higher AUC of CXCL8, CXCL10 and mucin production. The gene expression of p21CDKN1A (cellular senescence marker) at baseline was also higher in the elderly group, and there was a good positive correlation between basal p21 expression and viral load or RANTES (AUC).

Conclusion

Age was found to be a key factor affecting viral kinetics and biomarkers post virus infection in an ALI-culture model. Currently, novel or innovative in vitro cell models are introduced for virus research, but when virus studies are conducted, similarly to working with other clinical samples, the age balance is important to obtain more accurate results.

Evolutionary dynamics of group A and B respiratory syncytial virus in China, 2009-2018

Respiratory syncytial virus (RSV) is a major cause of acute respiratory tract infections in children and is a public health threat globally. To investigate the spatiotemporal dynamics of RSV evolution, we performed systematic phylogenetic analysis using all available sequences from the GenBank database, together with sequences from Shanghai, China. Both RSV-A and RSV-B appear to have originated in North America, with an inferred origin time of 1954.0 (1938.7-1967.6) and 1969.7 (1962.6-1975.5), respectively. BA-like strains of RSV-B, with a 60-nt insertion, and the ON1 strain of RSV-A, with a 72-nt insertion, emerged in 1997.6 (1996.2-1998.6) and 2010.1 (2009.1-2010.3), respectively. Since their origin, both genotypes have gradually replaced the former circulating genotypes to become the dominant strain. The population dynamic of RSV-A showed a seasonal epidemic pattern with obvious expansion in the periods of 2006-2007, 2010-2011, 2011-2012, and 2013-2014. Thirty fixed amino acid substitutions were identified during the divergence of NA4 from GA1 genotypes of RSV-A, and 13 were found during the divergence of SAB4 from GB1 of RSV-B. Importantly, ongoing evolution has occurred since the emergence of ON1, including four amino acid substitutions (I208L, E232G, T253K, and P314L). RSV-A genotypes GA5, NA4, NA1, and ON1 and RSV-B genotypes CB1, SAB4, BA-C, BA10, BA7, and BA9 were co-circulating in China from 2005 to 2015. In particular, RSV-A genotype ON1 was first detected in China in 2011, and it completely replaced GA2 to become the predominant strain after 2016. These data provide important insights into the evolution and epidemiology of RSV.

NMR Spectroscopic Windows on the Systemic Effects of SARS-CoV-2 Infection on Plasma Lipoproteins and Metabolites in Relation to Circulating Cytokines

To investigate the systemic metabolic effects of SARS-CoV-2 infection, we analyzed 1H NMR spectroscopic data on human blood plasma and co-modeled with multiple plasma cytokines and chemokines (measured in parallel). Thus, 600 MHz 1H solvent-suppressed single-pulse, spin-echo, and 2D J-resolved spectra were collected on plasma recorded from SARS-CoV-2 rRT-PCR-positive patients (n = 15, with multiple sampling timepoints) and age-matched healthy controls (n = 34, confirmed rRT-PCR negative), together with patients with COVID-19/influenza-like clinical symptoms who tested SARS-CoV-2 negative (n = 35). We compared the single-pulse NMR spectral data with in vitro diagnostic research (IVDr) information on quantitative lipoprotein profiles (112 parameters) extracted from the raw 1D NMR data. All NMR methods gave highly significant discrimination of SARS-CoV-2 positive patients from controls and SARS-CoV-2 negative patients with individual NMR methods, giving different diagnostic information windows on disease-induced phenoconversion. Longitudinal trajectory analysis in selected patients indicated that metabolic recovery was incomplete in individuals without detectable virus in the recovery phase. We observed four plasma cytokine clusters that expressed complex differential statistical relationships with multiple lipoproteins and metabolites. These included the following: cluster 1, comprising MIP-1β, SDF-1α, IL-22, and IL-1α, which correlated with multiple increased LDL and VLDL subfractions; cluster 2, including IL-10 and IL-17A, which was only weakly linked to the lipoprotein profile; cluster 3, which included IL-8 and MCP-1 and were inversely correlated with multiple lipoproteins. IL-18, IL-6, and IFN-γ together with IP-10 and RANTES exhibited strong positive correlations with LDL1-4 subfractions and negative correlations with multiple HDL subfractions. Collectively, these data show a distinct pattern indicative of a multilevel cellular immune response to SARS CoV-2 infection interacting with the plasma lipoproteome giving a strong and characteristic immunometabolic phenotype of the disease. We observed that some patients in the respiratory recovery phase and testing virus-free were still metabolically highly abnormal, which indicates a new role for these technologies in assessing full systemic recovery.

Safety and Antiviral Effects of Nebulized PC786 in a Respiratory Syncytial Virus Challenge Study

Background

PC786 is a nebulized nonnucleoside respiratory syncytial virus (RSV) polymerase inhibitor designed to treat RSV, which replicates in the superficial layer of epithelial cells lining the airways.

Methods

Fifty-six healthy volunteers inoculated with RSV-A (Memphis 37b) were randomly dosed with either nebulized PC786 (5 mg) or placebo, twice daily for 5 days, from either 12 hours after confirmation of RSV infection or 6 days after virus inoculation. Viral load (VL), disease severity, pharmacokinetics, and safety were assessed until discharge. RSV infection was confirmed by reverse-transcription quantitative polymerase chain reaction with any positive value (intention-to-treat infected [ITT-I] population) or RSV RNA ≥1 log₁₀ plaque-forming unit equivalents (PFUe)/mL (specific intention-to-treat infection [ITT-IS] population) in nasal wash samples.

Results

In the ITT-I population, the mean VL area under the curve (AUC) was lower in the PC786 group than the placebo group (274.1 vs 406.6 log₁₀ PFUe/mL × hour; P = .0359). PC786 showed a trend toward reduction of symptom score and mucous weight. In ITT-IS (post hoc analysis), the latter was statistically significant as well as VL AUC (P = .0126). PC786 showed an early time to maximum plasma concentration, limited systemic exposure, and long half-life and consequently a 2-fold accumulation over the 5-day dosing period. PC786 was well tolerated.

Conclusions

Nebulized PC786 demonstrated a significant antiviral effect against RSV, warranting further clinical study.

Clinical Trials Registration

ClinicalTrials.gov: NCT03382431; EudraCT: 2017-002563-18.

The association between climate, geography and respiratory syncitial virus hospitalizations among children in Ontario, Canada: a population-based study

Background

Respiratory syncytial virus (RSV) infection is a major cause of hospitalization in young children in Canada, despite routine immunoprophylaxis in those with medical risk factors. We aimed to determine if cold temperatures are associated with RSV hospitalization.

Methods

We conducted a population-based nested case–control study of children in Ontario, Canada, using health administrative data. We compared children hospitalized for RSV between September 1, 2011 and August 31, 2012 to age and sex matched controls. We used multivariable logistic regression to identify associations between minimum daily temperature and RSV hospitalizations with adjustment for sociodemographic and environmental factors.

Results

We identified 1670 children with RSV hospitalizations during the study period and 6680 matched controls. Warmer temperatures (OR = 0.94, 95%CI: 0.93, 0.95) were associated with lower odds of RSV hospitalization. Southern ecozone (OR = 1.6, 95%CI: 1.2, 2.1), increased ozone concentration (OR = 1.03, 95%CI: 1.01, 1.06) and living in a lower income neighbourhood (OR = 1.3, 95%CI: 1.1, 1.5) significantly increased the odds of RSV hospitalization, as did living in a household with a larger number of siblings in a sub-cohort of children (OR = 1.34, 95%CI: 1.26, 1.41).

Conclusions

In Ontario, the likelihood of having an RSV hospitalization is associated with colder temperature exposures and socioeconomic factors.

The Role of Viral Coinfection in Bronchiolitis Treated With High-Flow Nasal Cannula at Pediatric Emergency Department During 2 Consecutive Seasons: An Observational Study

BACKGROUND

The role of multiple respiratory viruses in bronchiolitis treated with high-flow nasal cannula (HFNC) has not been thoroughly investigated. We evaluated the contribution of coinfection on clinical course of bronchiolitis treated with HFNC and on response to this treatment.

METHODS

We selected 120 children with bronchiolitis, younger than 12 months, admitted to Emergency Department between 2016 and 2018 and treated with HFNC. We compared single and multiple virus infections in relation to specific outcomes such as the clinical response to HFNC and the HFNC failure. The multiple virus infection was defined by the detection of 2 or more viruses in nasopharyngeal aspirates. The HFNC failure was defined as escalation to higher level of care, including Helmet-Continuous Positive Airway Pressure, invasive ventilation or transfer to pediatric intensive care unit within 48 hours from the time of HFNC initiation. We also performed a comparison between HFNC failure and HFNC not-failure groups according to the number of virus and the type of virus.

RESULTS

The severity score post-HFNC initiation was significantly associated with coinfection [odds ratio (OR): 1.361; 95% confidence interval (CI): 1.036-1.786; P = 0.027]. The likelihood of coinfection decreased by 23.1% for each increase of saturation O2 after HFNC initiation (OR: 0.769; 95% CI: 0.609-0.972; P = 0.028). Atelectasis was more likely to occur in coinfection (OR: 2.923; 95% CI: 1.049-8.148; P = 0.04). The duration of HFNC treatment increased significantly in coinfection (OR: 1.018; 95% CI: 1.006-1.029; P = 0.002). No significant differences were described between HFNC failure and the number and the type of detected viruses.

CONCLUSIONS

The detection of multiple viruses and the type of virus did not influence the HFNC failure, although the coinfection was associated with a deterioration of severity score, a longer HFNC treatment and a major presence of atelectasis. The role of coinfection on HFNC treatment might subtend a complex interplay between multiple viruses and host susceptibility.

Aims, Study Design, and Enrollment Results From the Assessing Predictors of Infant Respiratory Syncytial Virus Effects and Severity Study

Background

The majority of infants hospitalized with primary respiratory syncytial virus (RSV) infection have no obvious risk factors for severe disease.

Objective

The aim of this study (Assessing Predictors of Infant RSV Effects and Severity, AsPIRES) was to identify factors associated with severe disease in full-term healthy infants younger than 10 months with primary RSV infection.

Methods

RSV infected infants were enrolled from 3 cohorts during consecutive winters from August 2012 to April 2016 in Rochester, New York. A birth cohort was prospectively enrolled and followed through their first winter for development of RSV infection. An outpatient supplemental cohort was enrolled in the emergency department or pediatric offices, and a hospital cohort was enrolled on admission with RSV infection. RSV was diagnosed by reverse transcriptase-polymerase chain reaction. Demographic and clinical data were recorded and samples collected for assays: buccal swab (cytomegalovirus polymerase chain reaction, PCR), nasal swab (RSV qualitative PCR, complete viral gene sequence, 16S ribosomal ribonucleic acid [RNA] amplicon microbiota analysis), nasal wash (chemokine and cytokine assays), nasal brush (nasal respiratory epithelial cell gene expression using RNA sequencing [RNAseq]), and 2 to 3 ml of heparinized blood (flow cytometry, RNAseq analysis of purified cluster of differentiation [CD]4+, CD8+, B cells and natural killer cells, and RSV-specific antibody). Cord blood (RSV-specific antibody) was also collected for the birth cohort. Univariate and multivariate logistic regression will be used for analysis of data using a continuous Global Respiratory Severity Score (GRSS) as the outcome variable. Novel statistical methods will be developed for integration of the large complex datasets.

Results

A total of 453 infants were enrolled into the 3 cohorts; 226 in the birth cohort, 60 in the supplemental cohort, and 78 in the hospital cohort. A total of 126 birth cohort infants remained in the study and were evaluated for 150 respiratory illnesses. Of the 60 RSV positive infants in the supplemental cohort, 42 completed the study, whereas all 78 of the RSV positive hospital cohort infants completed the study. A GRSS was calculated for each RSV-infected infant and is being used to analyze each of the complex datasets by correlation with disease severity in univariate and multivariate methods.

Conclusions

The AsPIRES study will provide insights into the complex pathogenesis of RSV infection in healthy full-term infants with primary RSV infection. The analysis will allow assessment of multiple factors potentially influencing the severity of RSV infection including the level of RSV specific antibodies, the innate immune response of nasal epithelial cells, the adaptive response by various lymphocyte subsets, the resident airway microbiota, and viral factors. Results of this study will inform disease interventions such as vaccines and antiviral therapies.

Late therapeutic intervention with a respiratory syncytial virus L-protein polymerase inhibitor, PC786, on respiratory syncytial virus infection in human airway epithelium

BACKGROUND AND PURPOSE

Effective anti-respiratory syncytial virus (RSV) agents are still not available for clinical use. Current major targets are virus surface proteins, such as a fusion protein involved in viral entry, but agents effective after RSV infection is established are required. Here we have investigated the effects of late therapeutic intervention with a novel inhaled RSV polymerase inhibitor, PC786, on RSV infection in human airway epithelium.

EXPERIMENTAL APPROACH

Air liquid interface-cultured bronchial or small airway epithelium was infected with RSVA2. PC786 was applied apically or basolaterally once daily following peak virus load on Day 3 post inoculation. Apical wash was collected daily for determination of viral burden by PCR and plaque assay (primary endpoints) and biomarker analyses. The effects were compared with those of ALS-8112, an anti-RSV nucleoside analogue, and GS-5806, a fusion-protein inhibitor, which were treated basolaterally.

KEY RESULTS

Late intervention with GS-5806 did not show significant anti-viral effects, but PC786 produced potent, concentration-dependent inhibition of viral replication with viral load falling below detectable limits 3 days after treatment commenced in airway epithelium. These effects were superior to those of ALS-8112. PC786 showed inhibitory activities against RSV-induced increases of CCL5, IL-6, double-strand DNA and mucin. The effects of PC786 were also confirmed in small airway epithelium.

CONCLUSION AND IMPLICATIONS

Late therapeutic intervention with the RSV polymerase inhibitor, PC786, reduced the viral burden quickly in human airway epithelium. Thus, PC786 demonstrates the potential to be an effective therapeutic agent to treat active RSV infection.

Engystol reduces onset of experimental respiratory syncytial virus-induced respiratory inflammation in mice by modulating macrophage phagocytic capacity

Background

Respiratory viruses such as respiratory syncytial virus (RSV) or rhinovirus are one of the major causes for respiratory tract infections causing common cold disease. Respiratory viral infections range from mild symptoms in adults to serious illness especially in the very young or elderly as well as patients suffering from lung diseases or being immunocompromised due to other reasons. Engystol (EGY-2) is a multicomponent, multitarget preparation consisting of Vincetoxicum hirundinaria and Sulfur in various dilutions. The study objective was to test the effect of EGY-2 on the innate immune response during the early onset of respiratory viral infection in vivo as exemplified in a mouse model of RSV-induced respiratory inflammation.

Methods

Naïve BALB/c mice were infected with 1x10⁶ infectious units RSV A2 intranasally to cause a mild respiratory infection. EGY-2 was administered daily per oral gavage starting seven days prior to RSV infection at doses of 0.4 to 5.1 tablets/kg. Control groups received placebo treatment. Animals were sacrificed 1 to 3 days post infection (p.i.) to analyse the infection and induced immune response in the lung. Viral load in bronchoalveolar lavage fluid (BALF) and lung homogenate was determined by TCID₅₀ assay as well as immunofluorescence staining of BALF cells using anti-RSV antibody and microscopic analysis. The RSV induced immune response was assessed by evaluation of BALF differential cell count, BALF cytokine secretion and analysis of the phagocytic capacity of alveolar macrophages.

Results

EGY-2 significantly reduced the RSV induced neutrophil and early lymphocyte influx on day 1 p.i. in BALF. EGY-2 treatment significantly diminished the RSV induced secretion of pro-inflammatory cytokines such as IFN-γ, IL-1β, IL-6, KC and TNF-α at day 1. EGY-2 treatment was not protective for RSV infection per se, as no alteration in the viral load in lung and BALF was detected. Enhanced numbers of phagocytic-active macrophages were observed in EGY-2 treated animals on day 1 and this macrophage population showed strongly enhanced phagocytic activity on day 1 and day 3.

Conclusion

The data suggest a beneficial immunomodulatory effect of EGY-2 during early onset of respiratory viral infection in vivo, mediated by stimulation of macrophage phagocytosis, resulting in a reduced innate inflammatory response in terms of neutrophil and early lymphocyte infiltration as well as reduced inflammatory cytokine secretion.

Molecular epidemiology of respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of viral acute respiratory tract infections in young children. The virus is characterised by distinct seasonality that is dependent upon the latitude and its ability to cause reinfection. Respiratory syncytial virus demonstrates a complex molecular epidemiology pattern as multiple strains and/or genotypes cocirculate during a single epidemic. Previous studies have investigated the relationship between RSV genetic diversity, reinfection, and clinical features. Here, we review the evidence behind this relationship together with the impact that the advancement of whole genome sequencing will have upon our understanding and the need for reconsidering the classification of RSV genotypes.

Distinct patterns of innate immune activation by clinical isolates of respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major respiratory pathogen of infants and young children. Multiple strains of both subgroup A and B viruses circulate during each seasonal epidemic. Genetic heterogeneity among RSV genomes, in large part due to the error prone RNA-dependent, RNA polymerase, could mediate variations in pathogenicity. We evaluated clinical strains of RSV for their ability to induce the innate immune response. Subgroup B viruses were used to infect human pulmonary epithelial cells (A549) and primary monocyte-derived human macrophages (MDM) from a variety of donors. Secretions of IL-6 and CCL5 (RANTES) from infected cells were measured following infection. Host and viral transcriptome expression were assessed using RNA-SEQ technology and the genomic sequences of several clinical isolates were determined. There were dramatic differences in the induction of IL-6 and CCL5 in both A549 cells and MDM infected with a variety of clinical isolates of RSV. Transcriptome analyses revealed that the pattern of innate immune activation in MDM was virus-specific and host-specific. Specifically, viruses that induced high levels of secreted IL-6 and CCL5 tended to induce cellular innate immune pathways whereas viruses that induced relatively low level of IL-6 or CCL5 did not induce or suppressed innate immune gene expression. Activation of the host innate immune response mapped to variations in the RSV G gene and the M2-1 gene. Viral transcriptome data indicated that there was a gradient of transcription across the RSV genome though in some strains, RSV G was the expressed in the highest amounts at late times post-infection. Clinical strains of RSV differ in cytokine/chemokine induction and in induction and suppression of host genes expression suggesting that these viruses may have inherent differences in virulence potential. Identification of the genetic elements responsible for these differences may lead to novel approaches to antiviral agents and vaccines.

Preclinical Characterization of PC786, an Inhaled Small-Molecule Respiratory Syncytial Virus L Protein Polymerase Inhibitor

Although respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and young children, attempts to develop an effective therapy have so far proved unsuccessful. Here we report the preclinical profiles of PC786, a potent nonnucleoside RSV L protein polymerase inhibitor, designed for inhalation treatment of RSV infection. PC786 demonstrated a potent and selective antiviral activity against laboratory-adapted or clinical isolates of RSV-A (50% inhibitory concentration [IC₅₀], <0.09 to 0.71 nM) and RSV-B (IC₅₀, 1.3 to 50.6 nM), which were determined by inhibition of cytopathic effects in HEp-2 cells without causing detectable cytotoxicity. The underlying inhibition of virus replication was confirmed by PCR analysis. The effects of PC786 were largely unaffected by the multiplicity of infection (MOI) and were retained in the face of established RSV replication in a time-of-addition study. Persistent anti-RSV effects of PC786 were also demonstrated in human bronchial epithelial cells. In vivo intranasal once daily dosing with PC786 was able to reduce the virus load to undetectable levels in lung homogenates from RSV-infected mice and cotton rats. Treatment with escalating concentrations identified a dominant mutation in the L protein (Y1631H) in vitro. In addition, PC786 potently inhibited RSV RNA-dependent RNA polymerase (RdRp) activity in a cell-free enzyme assay and minigenome assay in HEp-2 cells (IC₅₀, 2.1 and 0.5 nM, respectively). Thus, PC786 was shown to be a potent anti-RSV agent via inhibition of RdRp activity, making topical treatment with this compound a novel potential therapy for the treatment of human RSV infections.

Influenza and other respiratory viruses: standardizing disease severity in surveillance and clinical trials

INTRODUCTION

Influenza-Like Illness is a leading cause of hospitalization in children. Disease burden due to influenza and other respiratory viral infections is reported on a population level, but clinical scores measuring individual changes in disease severity are urgently needed. Areas covered: We present a composite clinical score allowing individual patient data analyses of disease severity based on systematic literature review and WHO-criteria for uncomplicated and complicated disease. The 22-item ViVI Disease Severity Score showed a normal distribution in a pediatric cohort of 6073 children aged 0-18 years (mean age 3.13; S.D. 3.89; range: 0 to 18.79). Expert commentary: The ViVI Score was correlated with risk of antibiotic use as well as need for hospitalization and intensive care. The ViVI Score was used to track children with influenza, respiratory syncytial virus, human metapneumovirus, human rhinovirus, and adenovirus infections and is fully compliant with regulatory data standards. The ViVI Disease Severity Score mobile application allows physicians to measure disease severity at the point-of care thereby taking clinical trials to the next level.

Animal models of respiratory syncytial virus infection

Human respiratory syncytial virus (hRSV) is a major cause of respiratory disease and hospitalisation of infants, worldwide, and is also responsible for significant morbidity in adults and excess deaths in the elderly. There is no licensed hRSV vaccine or effective therapeutic agent. However, there are a growing number of hRSV vaccine candidates that have been developed targeting different populations at risk of hRSV infection. Animal models of hRSV play an important role in the preclinical testing of hRSV vaccine candidates and although many have shown efficacy in preclinical studies, few have progressed to clinical trials or they have had only limited success. This is, at least in part, due to the lack of animal models that fully recapitulate the pathogenesis of hRSV infection in humans. This review summarises the strengths and limitations of animal models of hRSV, which include those in which hRSV is used to infect non-human mammalian hosts, and those in which non-human pneumoviruses, such as bovine (b)RSV and pneumonia virus of mice (PVM) are studied in their natural host. Apart from chimpanzees, other non-human primates (NHP) are only semi-permissive for hRSV replication and experimental infection with large doses of virus result in little or no clinical signs of disease, and generally only mild pulmonary pathology. Other animal models such as cotton rats, mice, ferrets, guinea pigs, hamsters, chinchillas, and neonatal lambs are also only semi-permissive for hRSV. Nevertheless, mice and cotton rats have been of value in the development of monoclonal antibody prophylaxis for infants at high risk of severe hRSV infection and have provided insights into mechanisms of immunity to and pathogenesis of hRSV. However, the extent to which they predict hRSV vaccine efficacy and safety is unclear and several hRSV vaccine candidates that are completely protective in rodent models are poorly effective in chimpanzees and other NHP, such as African Green monkeys. Furthermore, interpretation of findings from many rodent and NHP models of vaccine-enhanced hRSV disease has been confounded by sensitisation to non-viral antigens present in the vaccine and challenge virus. Studies of non-human pneumoviruses in their native hosts are more likely to reflect the pathogenesis of natural hRSV infection, and experimental infection of calves with bRSV and of mice with PVM result in clinical disease and extensive pulmonary pathology. These animal models have not only been of value in studies on mechanisms of immunity to and the pathogenesis of pneumovirus infections but have also been used to evaluate hRSV vaccine concepts. Furthermore, the similarities between the epidemiology of bRSV in calves and hRSV in infants and the high level of genetic and antigenic similarity between bRSV and hRSV, make the calf model of bRSV infection a relevant model for preclinical evaluation of hRSV vaccine candidates which contain proteins that are conserved between hRSV and bRSV.

Relation of Cytokine Profile to Clinical and Hemodynamic Features in Young Patients With Congenital Heart Disease and Pulmonary Hypertension

In congenital heart disease, severity of pulmonary hypertension and operability is defined by noninvasive parameters (clinical history, physical examination, and echocardiography) and sometimes, cardiac catheterization. We investigated how circulating levels of inflammatory mediators correlate with such parameters in a young pediatric population (age, 2.0 months to 3.1 years) and the effects of preoperative pulmonary vasodilator therapy with sildenafil. Cytokines were analyzed in serum using chemiluminescence signals. In the whole patient group (n = 47), interleukin 17E, a Th2 immune response mediator increased with increasing age, considered as a parameter of disease severity (R² = 0.24, p <0.001), whereas the angiogenic chemokine growth-regulated oncogene alpha decreased (R² = 0.21, p = 0.001). Macrophage migration inhibitory factor chemokine was greater in subjects with elevated pulmonary vascular resistance (n = 16, p = 0.022), whereas regulated on activation, normal T cell expressed and secreted chemokine was greater in subjects with pulmonary congestion due to increased pulmonary blood flow (n = 31, p = 0.037). The observations were the same for the specific subpopulation of patients with Down syndrome (p = 0.009 and p = 0.012 for migration inhibitory factor and regulated on activation, normal T cell expressed and secreted in the respective subgroups). Sildenafil administration to patients with elevated pulmonary vascular resistance resulted in improvement of pulmonary blood flow (p = 0.012) and systemic oxygen saturation (p = 0.010), with a decrease in serum interleukin 6 (p = 0.027) and soluble ICAM-1 (p = 0.011). In conclusion, levels of circulating inflammatory molecules seem to correlate with disease severity in this population, with potential pathophysiological and therapeutic implications.

Serum Cytokines in Young Pediatric Patients with Congenital Cardiac Shunts and Altered Pulmonary Hemodynamics

Background and Objective. Inflammation is central in the pathogenesis of pulmonary hypertension. We investigated how serum cytokines correlate with clinical features, hemodynamics, and lung histology in young patients with pulmonary hypertension associated with congenital cardiac shunts. Design. Prospective, observational study. Methods and Results. Patients (n = 44) were aged 2.6 to 37.6 months. Group I patients (n = 31) were characterized by pulmonary congestion and higher pulmonary blood flow compared to group II (p = 0.022), with no need for preoperative cardiac catheterization. Group II patients (n = 13) had no congestive features. At catheterization, they had elevated pulmonary vascular resistance (5.7 [4.4–7.4] Wood units·m², geometric mean with 95% CI). Cytokines were measured by chemiluminescence. Macrophage migration inhibitory factor (MIF) was found to be inversely related to pulmonary blood flow (r = −0.33, p = 0.026) and was higher in group II (high pulmonary vascular resistance) compared to group I (high pulmonary blood flow) (p = 0.017). In contrast, RANTES chemokine (regulated on activation, normal T cell expressed and secreted) was characteristically elevated in Group I (p = 0.022). Interleukin 16 was also negatively related to pulmonary blood flow (r_S = −0.33, p = 0.029) and was higher in patients with obstructive vasculopathy at intraoperative lung biopsy (p = 0.021). Conclusion. Cytokines seem to be important and differentially regulated in subpopulations of young patients with cardiac shunts.

Risk of Respiratory Syncytial Virus Infection in Cyanotic Congenital Heart Disease in a Subtropical Area

OBJECTIVE

To compare the risk of respiratory syncytial virus (RSV)-associated hospitalization and analyze the epidemiology of RSV infection in patients with cyanotic and acyanotic congenital heart disease (CHD), we analyzed the nationwide health insurance database from 2005-2010.

STUDY DESIGN

This study included 1050 patients with cyanotic CHD and 7077 patients with acyanotic CHD. Patients with acyanotic CHD were further classified into hemodynamically significant (hs)-acyanotic and non-hs-acyanotic groups according to whether they underwent surgery or took at least 2 anticongestive medications.

RESULTS

RSV-associated hospitalization was higher in the cyanotic group than in hs-acyanotic and non-hs-acyanotic groups both before 1 year of age (4.8% vs 2.1% vs 1.5%, P < .001) and between 1 and 2 years of age (0.9% vs 0.56% vs 0.14%, P = .003). The hospitalization duration, intensive care, ventilator support prevalence, hospitalization cost, and mortality rate were significantly higher in the cyanotic group than in the other 2 groups. Logistic regression revealed that cyanotic CHD was the most significant risk factor for the ventilator support and RSV-associated mortality. In both patients with cyanotic and acyanotic CHD, RSV-associated hospitalization rate was higher in patients aged younger than 1 year and in spring and autumn in Taiwan, a subtropical country.

CONCLUSIONS

The results show that patients with cyanotic CHD have a higher risk of severe RSV infection than do those with acyanotic CHD. RSV prophylaxis is more important and may reduce costs more for patients with cyanotic CHD.