Respiratory syncytial virus pneumonia: mechanisms of inflammation and prolonged airway hyperresponsiveness

Risk factors associated with wheezing in severe pediatric community-acquired pneumonia: a retrospective study

BACKGROUND

Wheezing is a common clinical manifestation in children with pneumonia. However, the risk factors associated with the development of wheezing pneumonia and its clinical features are not fully characterized, especially in children with severe pneumonia.

METHODS

We retrospectively recruited 1434 pediatric patients diagnosed with severe pneumonia between April 2012 and September 2019 in Fujian Maternity and Child Health Hospital. The medical records regarding demographic information, clinical manifestations, radiographic/laboratory findings, and complications were collected. Based on the presence or absence of wheezing symptoms and signs, subjects were divided into wheezing cohort (N.=684) and non-wheezing cohort (N.=750), and their clinical data were compared. Multivariate cox regression analysis was performed to identify independent risk factors of wheezing.

RESULTS

Demographic features including gender, weigh, onset season, birth weight, full-term birth or not, history of pneumonia were significantly associated with the occurrence of wheezing in severe CAP (P<0.05). Specifically, male gender, onset seasons in autumn/winter, and absence of a history of pneumonia were identified as independent risk factors of wheezing in multivariate analysis (P<0.05). As for clinical features, wheezing cohort differed from the non-wheezing one in terms of clinical manifestation (higher incidence of cough and breathless, but lower incidence of fever), laboratory finding (higher levels of red blood cells, hemoglobin, and albumin and lower levels of total or indirect bilirubin and creatine), pathogen detection (higher incidence of respiratory syncytial viral infection), and clinical complications (lesser risk of sepsis and hydrothorax) (P<0.05).

CONCLUSIONS

Severe CAP with wheezing is a special clinical entity of severe pneumonia in children, which has specific risk factors and differ from non-wheezing pneumonia in terms of clinical features and etiologic pathogens.

Regulation of acute reflectory hyperinflammation in viral and other diseases by means of stellate ganglion block. A conceptual view with a focus on Covid-19

Whereas the autonomic nervous system (ANS) and the immune system used to be assigned separate functions, it has now become clear that the ANS and the immune system (and thereby inflammatory cascades) work closely together. During an acute immune response (e. g., in viral infection like Covid-19) the ANS and the immune system establish a fast interaction resulting in "physiological" inflammation. Based on our knowledge of the modulation of inflammation by the ANS we propose that a reflectory malfunction of the ANS with hyperactivity of the sympathetic nervous system (SNS) may be involved in the generation of acute hyperinflammation. We believe that sympathetic hyperactivity triggers a hyperresponsiveness of the immune system ("cytokine storm") with consecutive tissue damage. These reflectory neuroimmunological and inflammatory cascades constitute a general reaction principle of the organism under the leadership of the ANS and does not only occur in viral infections, although Covid-19 is a typical current example therefore. Within the overreaction several interdependent pathological positive feedback loops can be detected in which the SNS plays an important part. Consequently, there is a chance to regulate the hyperinflammation by influencing the SNS. This can be achieved by a stellate ganglion block (SGB) with local anesthetics, temporarily disrupting the pathological positive feedback loops. Thereafter, the complex neuroimmune system has the chance to reorganize itself. Previous clinical and experimental data have confirmed a favorable outcome in hyperinflammation (including pneumonia) after SGB (measurable e. g. by a reduction in proinflammatory cytokines).

Pediatric Lower Respiratory Tract Infections: Imaging Guidelines and Recommendations

Lower respiratory tract infection (LRTI) remains a major cause of morbidity and mortality in children. Various organisms cause LRTI, including viruses, bacteria, fungi, and parasites, among others. Infections caused by 2 or more organisms also occur, sometimes enhancing the severity of the infection. Medical imaging helps confirm a diagnosis but also plays a role in the evaluation of acute and chronic sequelae. Medical imaging tests help evaluate underlying pathology in pediatric patients with recurrent or long-standing symptoms as well as the immunocompromised.

Factors Associated With Bronchiolitis Guideline Nonadherence at US Children's Hospitals

BACKGROUND

The objective with this study was to explore factors associated with nonadherence to national bronchiolitis guidelines at 52 children's hospitals.

METHODS

We included patients 1 month to 2 years old with emergency department (ED) or admission encounters between January 2016 and December 2018 and bronchiolitis diagnoses in the Pediatric Health Information System database. We excluded patients with any intensive care, stay >7 days, encounters in the preceding 30 days, chronic medical conditions, croup, pneumonia, or asthma. Guideline nonadherence was defined as receiving any of 5 tests or treatments: bronchodilators, chest radiographs, systemic steroids, antibiotics, and viral testing. Nonadherence outcomes were modeled by using mixed effects logistic regression with random effects for providers and hospitals. Adjusted odds ratio (aOR) >1 indicates greater likelihood of nonadherence.

RESULTS

A total of 198 028 encounters were included (141 442 ED and 56 586 admission), and nonadherence was 46.1% (ED: 40.2%, admissions: 61.0%). Nonadherence increased with patient age, with both ED and hospital providers being more likely to order tests and treatments for children 12 to 24 months compared with infants 1 ot 2 months (ED: aOR, 3.39; 95% confidence interval [CI], 3.20-3.60; admissions: aOR, 2.97; CI, 2.79-3.17]). Admitted non-Hispanic Black patients were more likely than non-Hispanic white patients to receive guideline nonadherent care (aOR, 1.16; CI, 1.10-1.23), a difference driven by higher use of steroids (aOR, 1.29; CI, 1.17-1.41) and bronchodilators (aOR, 1.39; CI, 1.31-1.48). Hospital effects were prominent for viral testing in ED and admission encounters (intraclass correlation coefficient of 0.35 and 0.32, respectively).

CONCLUSIONS

Multiple factors are associated with national bronchiolitis guideline nonadherence.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Respiratory Syncytial Virus Persistence in Murine Macrophages Impairs IFN-β Response but Not Synthesis

Type-I interferon (IFN-I) production is an early response to viral infection and pathogenic viruses have evolved multiple strategies to evade this cellular defense. Some viruses can establish and maintain persistent infections by altering the IFN-I signaling pathway. Here, we studied IFN-I synthesis and response in an in vitro model of persistent infection by respiratory syncytial virus (RSV) in a murine macrophage-like cell line. In this model, interferon regulatory factor 3 was constitutively active and located at nuclei of persistently infected cells, inducing expression of IFN-beta mRNA and protein. However, persistently infected macrophages did not respond in an autocrine manner to the secreted-IFN-beta or to recombinant-IFN-beta, since phosphorylated-STAT1 was not detected by western blot and transcription of the interferon-stimulated genes (ISGs) Mx1 and ISG56 was not induced. Treatment of non-infected macrophages with supernatants from persistently infected cells induced STAT1 phosphorylation and ISGs expression, mediated by the IFN-I present in the supernatants, because blocking the IFN-I receptor inhibited STAT1 phosphorylation. Results suggest that the lack of autocrine response to IFN-I by the host cell may be one mechanism for maintenance of RSV persistence. Furthermore, STAT1 phosphorylation and ISGs expression induced in non-infected cells by supernatants from persistently infected macrophages suggest that RSV persistence may trigger a proinflammatory phenotype in non-infected cells as part of the pathogenesis of RSV infection.

Respiratory syncytial virus persistence in macrophages alters the profile of cellular gene expression

Viruses can persistently infect differentiated cells through regulation of expression of both their own genes and those of the host cell, thereby evading detection by the host’s immune system and achieving residence in a non-lytic state. Models in vitro with cell lines are useful tools in understanding the mechanisms associated with the establishment of viral persistence. In particular, a model to study respiratory syncytial virus (RSV) persistence in a murine macrophage-like cell line has been established. Compared to non-infected macrophages, macrophages persistently infected with RSV show altered expression both of genes coding for cytokines and trans-membrane proteins associated with antigen uptake and of genes related to cell survival. The biological changes associated with altered gene expression in macrophages as a consequence of persistent RSV infection are summarized.

Respiratory syncytial virus (RSV) RNA loads in peripheral blood correlates with disease severity in mice

BACKGROUND

Respiratory Syncytial Virus (RSV) infection is usually restricted to the respiratory epithelium. Few studies have documented the presence of RSV in the systemic circulation, however there is no consistent information whether virus detection in the blood correlates with disease severity.

METHODS

Balb/c mice were inoculated with live RSV, heat-inactivated RSV or medium. A subset of RSV-infected mice was treated with anti-RSV antibody 72 h post-inoculation. RSV RNA loads were measured by PCR in peripheral blood from day 1-21 post-inoculation and were correlated with upper and lower respiratory tract viral loads, the systemic cytokine response, lung inflammation and pulmonary function. Immunohistochemical staining was used to define the localization of RSV antigens in the respiratory tract and peripheral blood.

RESULTS

RSV RNA loads were detected in peripheral blood from day 1 to 14 post-inoculation, peaked on day 5 and significantly correlated with nasal and lung RSV loads, airway obstruction, and blood CCL2 and CXCL1 expression. Treatment with anti-RSV antibody reduced blood RSV RNA loads and improved airway obstruction. Immunostaining identified RSV antigens in alveolar macrophages and peripheral blood monocytes.

CONCLUSIONS

RSV RNA was detected in peripheral blood upon infection with live RSV, followed a time-course parallel to viral loads assessed in the respiratory tract and was significantly correlated with RSV-induced airway disease.

Acquired Nonneoplastic Neonatal and Pediatric Diseases

The lung biopsy is an established procedure to procure a pathologic diagnosis in a child with a suspected pneumonic process of undetermined etiology. Improvements in pediatric anesthesia and surgery have reduced the operative complications to a minimum. A biopsy can usually be taken through a small intercostal incision when localization is not especially important in a patient with diffuse changes (see Chapter 1). The alternative method for tissue sampling is the endoscopic transbronchial biopsy. There is less risk to the patient, but the specimen is smaller and crush artifacts from the instrument are more common.

Acute primary Chlamydophila pneumoniae bronchitis and bronchial hyperresponsiveness in young nonasthmatic Thai military recruits

BACKGROUND

A correlation between chronic Chlamydophila pneumoniae infection and chronic airway diseases has been suggested by several studies, but direct evidence to support the link between acute Cpneumoniae infection and new-onset asthma is insufficient.

OBJECTIVES

To determine the association between C. pneumoniae infection and subsequent bronchial hyperresponsiveness (BHR) and hence asthma.

METHODS

We studied 110 Thai military conscripts during an epidemic of Cpneumoniae infection in Thailand, from November 1, 1998, through February 28, 1999. The diagnosis was based on a standardized microimmunofluorescence technique. Spirometry and methacholine challenge tests (MCTs) were conducted. This cohort study excluded all conscripts with preexisting positive MCTs.

RESULTS

Ninety-three percent of the conscripts presented with an acute cough of a mean duration of 15.2 days. The pattern of serologic response revealed that 83% had acute primary infections and 10% had acute reinfections. Mean forced expiratory volume in 1 second was 99.5%, with an improvement of 1.8% after bronchodilator administration. Only 3.6% revealed small airways disease (forced expiratory flow between 25% and 75% of <65%) on spirometry. Methacholine challenge tests failed to demonstrate BHR in all conscripts, and none had developed a new-onset wheeze (physician-diagnosed asthma) at up to 2 years of follow-up.

CONCLUSIONS

This study demonstrates that cough in patients with acute primary Cpneumoniae infection is not associated with BHR among previously healthy adults. The pathogenetic mechanism by which organisms cause coughing and wheezing in acute bronchitis seems to be different among causative respiratory pathogens.

Antioxidant treatment ameliorates respiratory syncytial virus-induced disease and lung inflammation

RATIONALE

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in children. No treatment has been shown to significantly improve the clinical outcome of patients with this infection. Recent evidence suggests that oxidative stress could play an important role in the pathogenesis of acute and chronic lung inflammatory diseases. We do not known whether RSV induces pulmonary oxidative stress and whether antioxidant treatment can modulate RSV-induced lung disease.

OBJECTIVES

To investigate the effect of antioxidant administration on RSV-induced lung inflammation, clinical disease, and airway hyperreactivity (AHR).

METHODS

BALB/c mice were infected with 10(7) plaque-forming units of RSV, in the presence or absence of orally administered butylated hydroxyanisole (BHA), an antioxidant. Malondialdehyde and 4-hydroxynonenal were measured in bronchoalveoar lavage (BAL) by colorimetric assay. Cytokines and chemokines were measured in BAL by Bio-Plex and leukotrienes were measured by enzyme-linked immunosorbent assay. AHR to methacholine challenge was measured by whole-body plethysmography.

RESULTS

BHA treatment significantly attenuated RSV-induced lung oxidative stress, as indicated by the decrease of malondialdehyde and 4-hydroxynonenal content in BAL of RSV-infected mice. RSV-induced clinical illness and body weight loss were also reduced by BHA treatment, which inhibited neutrophil recruitment to the lung and significantly reduced pulmonary cytokine and chemokine production after RSV infection. Similarly, antioxidant treatment attenuated RSV-induced AHR.

CONCLUSION

Modulation of oxidative stress represents a potential novel pharmacologic approach to ameliorate RSV-induced acute lung inflammation and potentially prevent long-term consequences associated with RSV infection, such as bronchial asthma.

Lung inflammatory responses

Inflammation is an important manifestation of respiratory disease in domestic animals. The respiratory system is mucosal in nature and has specific defense mechanisms used to control invasion by microbes and environmental elements. Inflammation can be beneficial or detrimental to the host. This article broadly discusses the primary mediators and mechanisms of inflammation within the respiratory tract of domestic animals. The role of cells, chemokines, cytokines and mediators in both acute and chronic inflammation are addressed. The pathogenesis of the initial insult determines the type of inflammation that will be induced, whether it is acute, chronic or allergic in origin. Maintenance of the microenvironment of cytokines and chemokines is critical for pulmonary homeostasis. Uncontrolled inflammation in the respiratory tract can be life threatening to the animal. The understanding of the mechanisms of inflammation, whether due to microbes or through inappropriate immune activation such as those occurring with allergies, is required to develop successful intervention strategies and control respiratory disease in animals.

Kinase inhibitors and airway inflammation

Kinases are believed to play a crucial role in the expression and activation of inflammatory mediators in the airway, in T-cell function and airway remodelling. Important kinases such as Inhibitor of kappaB kinase (IKK)2, mitogen activated protein (MAP) kinases and phsopho-inositol (PI)3 kinase regulate inflammation either through activation of pro-inflammatory transcription factors such as activating protein-1 (AP-1) and nuclear factor kappaB (NF-kappaB), which are activated in airway disease, or through regulation of mRNA half-life. Selective kinase inhibitors have been developed which reduce inflammation and some characteristics of disease in animal models. Targeting specific kinases that are overexpressed or over active in disease should allow for selective treatment of respiratory diseases. Interest in this area has intensified due to the success of the specific Abelson murine leukaemia viral oncogene (Abl) kinase inhibitor imatinib mesylate (Gleevec) in the treatment of chronic myelogenous leukaemia. Encouraging data from animal models and primary cells and early Phase I and II studies in other diseases suggest that inhibitors of p38 MAP kinase and IKK2 may prove to be useful novel therapies in the treatment of severe asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis and other inflammatory airway diseases.

Immunopathogenesis of coronavirus infections: implications for SARS

The severe acute respiratory syndrome (SARS), which was first identified in 2003, is caused by a novel coronavirus: the SARS coronavirus (SARS-CoV).

Many features of the infection indicate that an excessive, but perhaps 'normal', immune response contributes to SARS.

Several coronaviruses cause diseases that result in considerable morbidity and mortality in animals. Some of these diseases are also immune mediated and provide insights into the pathogenesis of SARS.

Feline infectious peritonitis virus (FIPV) causes a fatal, immune-mediated disease of felines. Macrophage infection, lymphocyte depletion and antibody-dependent disease enhancement are hallmarks of this disease.

Infection with the murine coronavirus murine hepatitis virus (MHV) strain JHM results in immune-mediated demyelination. Similar to SARS, macrophage activation is a key component in the pathogenic process.

Another strain of MHV, MHV-3, causes a fatal, fulminant hepatitis. MHV-3 infection of macrophages, with subsequent activation and induction of expression of a novel procoagulant, fibrinogen-like protein 2 (FGL2), is required for severe disease.

Chickens that are infected with avian infectious bronchitis virus (IBV) develop respiratory and renal disease. An excessive innate immune response contributes to the pathogenic process in these animals.

To develop effective therapies for SARS will require understanding of the contributions of direct injury by virus and of the host immune response to pathogenesis. This requires further studies of the interactions of SARS-CoV with its target cells and necessitates the development of an animal model that reproduces the pulmonary infection that is observed in infected humans.

At the end of 2002, the first cases of severe acute respiratory syndrome (SARS) were reported, and in the following year, SARS resulted in considerable mortality and morbidity worldwide. SARS is caused by a novel species of coronavirus (SARS-CoV) and is the most severe coronavirus-mediated human disease that has been described so far. On the basis of similarities with other coronavirus infections, SARS might, in part, be immune mediated. As discussed in this Review, studies of animals that are infected with other coronaviruses indicate that excessive and sometimes dysregulated responses by macrophages and other pro-inflammatory cells might be particularly important in the pathogenesis of disease that is caused by infection with these viruses. It is hoped that lessons from such studies will help us to understand more about the pathogenesis of SARS in humans and to prevent or control outbreaks of SARS in the future.