Development of interleukin 6 and tumor necrosis factor alpha activity in nasopharyngeal secretions of infants and children during infection with respiratory syncytial virus

Respiratory Syncytial Virus Infections in Neonates: A Persisting Problem

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

Effects of calcitriol on oxidative burst, phagocytic function, and leukocyte cytokine production in shelter dogs

Background

The active metabolite of vitamin D, calcitriol, has been shown across many different species to augment innate immune responses and dampen aberrant proinflammatory cytokine production. Community acquired infections are common in shelters and consume limited shelter resources, impact adoption rates, and can result in unnecessary euthanasia. Prophylactic oral vitamin D supplementation decreases the incidence and severity of upper and lower respiratory tract infections in humans. Before a clinical trial investigating the clinical benefit of oral vitamin D supplementation in shelter dogs can be pursued, an in vitro study evaluating the immunomodulatory effects of calcitriol in blood from shelter dogs is warranted. Therefore, the objective of this study was to determine if incubation of whole blood obtained from apparently healthy dogs housed in a shelter for ≥7 days with calcitriol would alter granulocyte/monocyte (GM) oxidative burst and phagocytic function as well as pathogen-associated molecular pattern (PAMP)-stimulated leukocyte production of tumor necrosis factor (TNF)-α, and interleukin (IL)-6, and IL-10.

Results

Ten dogs housed in a shelter for ≥7 days were enrolled in a prospective cohort study. Whole blood from these dogs was incubated with calcitriol (10^− 7 M) or diluent (control) for 24 h. Subsequent to this incubation, phagocytosis of opsonized-Escherichia coli (E. coli) and E. coli-induced oxidative burst were evaluated via flow cytometry. In addition, leukocyte production of TNF-α, IL-6, and IL-10 were measured using a canine-specific multiplex bead assay. Calcitriol significantly decreased leukocyte TNF-α production (p = 0.009) and increased IL-10 production (p = 0.002). Tumor necrosis factor-α-to-IL-10 ratio was significantly decreased with calcitriol (p = 0.017), while IL-6 production as well as GM oxidative burst and phagocytic function were not significantly affected.

Conclusions

These data indicate that calcitriol attenuates proinflammatory immune responses without affecting GM oxidative burst or phagocytic function in vitro in whole blood obtained from apparently healthy shelter dogs.

Immune function and serum vitamin D in shelter dogs: A case-control study

This study sought to establish a baseline understanding of immune function and its association with serum vitamin D in shelter dogs. Ten apparently healthy shelter dogs housed in the Arizona Humane Society for ≥7 days and 10 apparently healthy, age, breed, and sex-matched control dogs were included. Serum 25-hydroxyvitamin D (25[OH]D), the major circulating vitamin D metabolite, was measured using high performance liquid chromatography. Whole blood samples were stimulated with lipopolysaccharide (LPS), lipoteichoic acid, or phosphate buffer solution, and tumor necrosis factor (TNF)-ɑ, interleukin (IL)-6, and IL-10 were measured using a canine-specific multiplex bead-based assay. Phagocytosis of opsonized-Escherichia coli and E. coli-induced oxidative burst were evaluated with flow cytometry. Shelter dogs had decreased percentages of granulocytes and monocytes (GM) that had phagocytized opsonized-E coli (P = 0.019) and performed E. coli-induced oxidative burst (P = 0.011). There were no significant differences in TNF-α, IL-6, IL-10, or 25(OH)D concentrations between shelter and control dogs. Serum 25(OH)D concentrations had a weak positive association with the intensity of GM E. coli-induced oxidative burst (r² = 0.23, P = 0.03). There was a moderate inverse association between serum 25(OH)D concentration and LPS-stimulated TNF-ɑ production in shelter dogs (r² = 0.40, P = 0.04). These results demonstrate immune dysregulation in vitro in shelter dogs housed for ≥7 days when compared to age, breed, and sex-matched control dogs. While serum 25(OH)D concentrations did not differ between shelter and control dogs, significant associations between 25(OH)D concentration and immune function parameters in vitro were identified.

Smoke Exposure, Cytokine Levels, and Asthma Visits in Children Hospitalized for Bronchiolitis

BACKGROUND AND OBJECTIVE

To determine if cigarette smoke exposure, marijuana smoke exposure, or cytokine levels at admission to the hospital for bronchiolitis are associated with follow-up visits for asthma.

METHODS

We enrolled a cohort of children aged 31 days to 2 years who were hospitalized with bronchiolitis from January 2013 to April 2014. Data included the results of a baseline survey about children's health and demographics, nasal wash samples, the results of a 6-month postdischarge follow-up survey, and a chart review. Nasal wash samples were tested for interleukin (IL)-6, IL-13, and tumor necrosis factor α (TNF-α); values were categorized for analysis. χ2, Fisher's exact, and Wilcoxon rank tests were done to test bivariable differences; all analyses were done using SAS.

RESULTS

We approached 180 families for enrollment; 99 consented to participate, and 74% of these completed follow-up surveys. Half of those with high levels of IL-13 had follow-up visits for asthma, whereas only 4.2% of those with low levels had follow-up visits for asthma (P = .02). Marijuana exposure was reported for 12.5% (n = 7) of study participants. There was a significant association between marijuana exposure and TNF-α levels (P = .03).

CONCLUSIONS

Our study revealed an association between IL-13 and follow-up visits for asthma in children who were hospitalized with bronchiolitis. We found an association between family-reported marijuana smoke exposure and detectable but lower levels of TNF-α. Further research is needed to study these relationships.

Cytokines regulate complement receptor immunoglobulin expression and phagocytosis of Candida albicans in human macrophages: A control point in anti-microbial immunity

Complement Receptor Immunoglobulin (CRIg), selectively expressed by macrophages, plays an important role in innate immunity by promoting phagocytosis of bacteria. Thus modulation of CRIg on macrophages by cytokines can be an important mechanism by which cytokines regulate anti-microbial immunity. The effects of the cytokines, tumor necrosis factor, transforming growth factor-β1, interferon-γ, interleukin (IL)-4, IL-13, IL-10, IL-1β, IL-6, lymphotoxin-α, macrophage-colony stimulating factor (M-CSF) and GM-CSF on CRIg expression were examined in human macrophages. We demonstrated that cytokines regulated the CRIg expression on macrophages during their development from monocytes in culture at the transcriptional level using qPCR and protein by Western blotting. Both CRIg spliced forms (Long and Short), were similarly regulated by cytokines. Direct addition of cytokines to matured CRIg+ macrophages also changed CRIg mRNA expression, suggesting that cytokines control macrophage function via CRIg, at two checkpoints. Interestingly the classical complement receptors, CR3 and CR4 were differentially regulated by cytokines. The changes in CRIg but not CR3/CR4 mRNA expression correlated with ability to phagocytose Candida albicans by macrophages. These findings suggest that CRIg is likely to be a control point in infection and immunity through which cytokines can mediate their effects, and is differentially regulated from CR3 and CR4 by cytokines.

The Human Immune Response to Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is an important etiological agent of respiratory infections, particularly in children. Much information regarding the immune response to RSV comes from animal models and in vitro studies. Here, we provide a comprehensive description of the human immune response to RSV infection, based on a systematic literature review of research on infected humans. There is an initial strong neutrophil response to RSV infection in humans, which is positively correlated with disease severity and mediated by interleukin-8 (IL-8). Dendritic cells migrate to the lungs as the primary antigen-presenting cell. An initial systemic T-cell lymphopenia is followed by a pulmonary CD8+ T-cell response, mediating viral clearance. Humoral immunity to reinfection is incomplete, but RSV IgG and IgA are protective. B-cell-stimulating factors derived from airway epithelium play a major role in protective antibody generation. Gamma interferon (IFN-γ) has a strongly protective role, and a Th2-biased response may be deleterious. Other cytokines (particularly IL-17A), chemokines (particularly CCL-5 and CCL-3), and local innate immune factors (including cathelicidins and IFN-λ) contribute to pathogenesis. In summary, neutrophilic inflammation is incriminated as a harmful response, whereas CD8+ T cells and IFN-γ have protective roles. These may represent important therapeutic targets to modulate the immunopathogenesis of RSV infection.

Pathophysiology of Clinical Symptoms in Acute Viral Respiratory Tract Infections

In this article we discuss the pathophysiology of common symptoms of acute viral respiratory infections (e.g., sneezing, nasal discharge, sore throat, cough, muscle pains, malaise, and mood changes). Since clinical symptoms are not sufficient to determine the etiology of viral respiratory tract infections, we believe that the host defense mechanisms are critical for the symptomatology. Consequently, this review of literature is focused on the pathophysiology of respiratory symptoms regardless of their etiology. We assume that despite a high prevalence of symptoms of respiratory infection, their pathogenesis is not widely known. A better understanding of the symptoms' pathogenesis could improve the quality of care for patients with respiratory tract infections.

Interleukins for the paediatric pulmonologist

Interleukins are critical immune modulators and since their first description in 1977, there has been a steady increase in the recognition of their roles in many paediatric respiratory diseases. This basic and clinical knowledge is now maturing into both approved and investigational therapies aimed at blocking or modifying the interleukin response. The purpose of this review is to bring up to date what is known about interleukin function in paediatric pulmonology, focusing on nine important lung conditions. This is followed by summaries about 18 interleukins which have been associated with these paediatric pulmonary conditions. Throughout, emphasis is placed on where interventions have been tested. Over the next several years, it is likely that many more treatments based on interleukin biology and function will become available and understanding the basis for these therapies will allow the practicing paediatric pulmonologist to take appropriate advantage of them.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

Immunisation of pigs with a major envelope protein sub-unit vaccine against porcine reproductive and respiratory syndrome virus (PRRSV) results in enhanced clinical disease following experimental challenge

Disease exacerbation was observed in pigs challenged with virulent porcine reproductive and respiratory syndrome virus (PRRSV) following immunisation with a recombinant GP5 sub-unit PRRSV vaccine (rGP5) produced in E. coli. Eighteen animals were divided into three experimental groups: group A were immunised twice IM with rGP5, 21 days apart; group B acted as positive controls (challenged but not immunised); and group C were negative controls. Pigs in groups A and B were challenged 21 days after the second immunisation of the group A animals. Following challenge, three pigs given rGP5 exhibited more severe clinical signs than the positive controls, including respiratory distress and progressive weight-loss. Although not statistically significant, the more severe disease exhibited by group A animals may suggest previous immunisation as a contributory factor. The mechanisms of these findings remain unclear and no association could be established between the severity of disease, non-neutralising antibody concentrations and tissue viral loads.

Respiratory viral infections in hematopoietic stem cell and solid organ transplant recipients

Respiratory viral infections (RVIs) are common causes of mild illness in immunocompetent children and adults with rare occurrences of significant morbidity or mortality. Complications are more common in the very young, very old, and those with underlying lung diseases. However, RVIs are increasingly recognized as a cause of morbidity and mortality in recipients of hematopoietic stem cell transplants (HSCT) and solid organ transplants (SOTs). Diagnostic techniques for respiratory syncytial virus (RSV), parainfluenza, influenza, and adenovirus have been clinically available for decades, and these infections are known to cause serious disease in transplant recipients. Modern molecular technology has now made it possible to detect other RVIs including human metapneumovirus, coronavirus, and bocavirus, and the role of these viruses in causing serious disease in transplant recipients is still being worked out. This article reviews the current information regarding epidemiology, pathogenesis, clinical presentation, diagnosis, and treatment of these infections, as well as the aspects of clinical significance of RVIs unique to HSCT or SOT.

The use of a neonatal mouse model to study respiratory syncytial virus infections

Respiratory syncytial virus (RSV) infection is the most significant cause of viral death in infants worldwide. The significant morbidity and mortality associated with this disease underscores the urgent need for the development of an RSV vaccine. The development of an RSV vaccine has been hampered by our limited understanding of the human host immune system, which plays a significant role in RSV pathogenesis, susceptibility and vaccine efficacy. As a result, animal models have been developed to better understand the mechanisms by which RSV causes disease. Within the past few years, a revolutionary variation on these animal models has emerged--age at time of initial infection--and early studies in neonatal mice (aged <7 days at time of initial infection) indicate the validity of this model to understand RSV infection in infants. This article reviews available information on current murine and emerging neonatal mouse RSV models.

Double-stranded RNA-activated protein kinase regulates early innate immune responses during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the most common cause of childhood viral bronchiolitis and lung injury. Inflammatory responses significantly contribute to lung pathologies during RSV infections and bronchiolitis but the exact mechanisms have not been completely defined. The double-stranded RNA-activated protein kinase (PKR) functions to inhibit viral replication and participates in several signaling pathways associated with innate inflammatory immune responses. Using a functionally defective PKR (PKR(-/-)) mouse model, we investigated the role of this kinase in early events of RSV-induced inflammation. Our data showed that bronchoalveolar lavage (BAL) fluid from infected PKR(-/-) mice had significantly lower levels of several innate inflammatory cytokines and chemokines. Histological examinations revealed that there was less lung injury in infected PKR(-/-) mice as compared to the wild type. A genome-wide analysis showed that several early antiviral and immune regulatory genes were affected by PKR activation. These data suggest that PKR is a signaling molecule for immune responses during RSV infections.

The role of TNF-alpha in eosinophilic inflammation associated with RSV bronchiolitis

The purpose of our study was to investigate whether tumor necrosis factor (TNF)-alpha correlates with eosinophilic inflammation that occurs during a lower respiratory tract infection with the respiratory syncytial virus (RSV) in children. Sixty children with RSV bronchiolitis (RSV group) and 20 healthy children with no respiratory symptoms (Control group) were enrolled. We measured the nasal lavage fluid (NLF) Th2 cytokine (IL-5), proinflammatory cytokine (TNF-alpha, IL-8), eosinophil-active cytokine [granulocyte-macrophage colony stimulating factor (GM-CSF), IFN-gamma], and eosinophil-active chemokine (eotaxin, regulated on activation normal T cell excreted and secreted) levels for both groups. We also measured serum eosinophil-degranulation product (eosinophil-derived neurotoxin; EDN, eosinophil cationic protein; ECP) levels from RSV group. TNF-alpha, IL-8, GM-CSF, IFN-gamma, and eotaxin levels were significantly higher in the RSV group compared with the Control group. TNF-alpha correlated with GM-CSF (r = 0.87, p < 0.0001), IFN-gamma (r = 0.92, p < 0.0001), eotaxin (r = 0.64, p < 0.0001), and IL-8 (r = 0.84, p < 0.0001). TNF-alpha may have an important role in eosinophilic inflammation of airways in children with RSV bronchiolitis.

Local production of inflammatory mediators during childhood parainfluenza virus infection

OBJECTIVE

To describe the clinical manifestations of parainfluenza virus (PIV) infection and to characterize biochemical markers of PIV disease severity.

PATIENTS AND METHODS

We reviewed the medical records of 165 children who had a nasal wash culture positive for PIV at our institution between 1998 and 2008. Nasal wash samples were assayed for 26 inflammatory mediators using Luminex bead proteomics.

RESULTS

A total of 153 patients, ages 2 weeks to 12 years, with single virus infection were included in our final analysis. Fifty-two patients were infected with PIV1, 19 with PIV2, 74 with PIV3, and 8 with PIV4. Lower respiratory tract infection (LRTI) was diagnosed in 67 (44%) patients, 21 (14%) had laryngotracheobronchitis, and 49 (32%) had an upper respiratory infection other than laryngotracheobronchitis. LRTI was diagnosed in 54% of patients infected with PIV3, 35% of those infected with PIV1, 26% of those with PIV2, and 50% of those with PIV4. Compared with uninfected control patients, PIV-infected patients had higher nasal wash concentrations of interleukin-6, CX-chemokine ligand 8 (CXCL8 or interleukin-8), CCL3 (macrophage inflammatory protein-1alpha), CCL4 (macrophage inflammatory protein-1beta), CXCL9 (monokine induced by interferon gamma), and CCL5 (regulated upon activation, normal T cell expressed and secreted (RANTES). Patients with LRTI, moderate or severe illness, and PIV 1 or 3 (respirovirus) infection had higher nasal wash concentrations of CXCL8 when compared with patients with upper respiratory infection, mild illness, or PIV 2 and 4 (rubulavirus) infection (P < 0.05).

CONCLUSIONS

PIV infection causes a spectrum of illnesses associated with the expression and release of several proinflammatory mediators. Of note, elevated concentrations of CXCL8 in nasal wash samples are associated with more severe forms of PIV disease.

Immunopathogenesis of polymicrobial otitis media

OM, or inflammation of the middle ear, is a highly prevalent infection in children worldwide. OM is a multifactorial disease with multiple risk factors, including preceding or concurrent viral URT infection. Hence, OM is also a polymicrobial disease. The mechanisms by which viruses predispose to bacterial OM are replete; however, all are predicated on the general principle of compromise of primary host airway defenses. Thus, despite an as-yet incomplete understanding of the molecular mechanisms involved in bacterial superinfection of a virus-compromised respiratory tract, the URT viruses are known to induce histopathology of airway mucosal epithelium, up-regulate expression of eukaryotic receptors used for bacterial adherence, alter the biochemical and rheological properties of airway mucus, and affect innate and acquired host immune functions, among others. Although discussed here in the context of OM, during preceding or concurrent viral infection of the human respiratory tract, viral impairment of airway defenses and the resulting predisposition to subsequent bacterial coinfection are also known to be operational in the mid and lower airway as well.

Otitis Media and Sinusitis

Otitis media (OM) and sinusitis are common and costly maladies that are often preceded by the development of a viral upper respiratory infection (vURI). Although antibiotics have been shown to be somewhat effective in the treatment of these disorders, increasing concern over the emergence of pathogen resistence to these agents underscores the need for the development of other treatment options, including agents to treat and/or prevent vURIs. Earlier research implicated roles for cytopathology, cellular infiltration, and inflammatory mediators such as bradykinin, in the pathogenesis of vURIs and its complications, including OM and sinusitis, but these factors are now recognized as late events with specific and limited contributions to disease expression. Current therapies are relatively ineffective and aimed at reducing symptoms rather than moderating underlying mechanisms. Nasal elevations of proinflammatory cytokines and leukotrienes track symptom expression during vURIs, and it is hypothesized that these chemicals orchestrate a common response to infection with many different viruses causing vURIs. Moreover, recent evidence demonstrates that specific cytokine gene polymorphisms may modulate the severity of illness and incidence of complications during episodes of vURI. Additionally, other evidence supports a role for neurogenic inflammation in the development of complications. Future studies should dissect the role of proinflammatory cytokines, leukotrienes, and neuropeptides in the expression of symptoms, signs, pathophysiologies, and complications of vURIs.

RSV-infected airway epithelial cells cause biphasic up-regulation of CCR1 expression on human monocytes

Respiratory syncytial virus (RSV) infection can cause extensive airway inflammation, which is orchestrated by chemokines and their receptors. RSV-infected epithelial cells secrete many cytokines and chemokines, but little is known about regulation of chemokine receptors on target cells. We investigated the effects of conditioned media (CM) from RSV-infected epithelial cells on monocyte CCR1, CCR2, and CCR5 expression. RSV-CM but not control-CM stimulated a biphasic increase in cell-surface CCR1, and levels peaked at 36 h and 96 h poststimulation. Similar CCR1 up-regulation occurred on monocyte-derived macrophages. Cytochlasin D and colchicine blocked both peaks of expression, demonstrating requirement of a functional cytoskeleton. Intracellular staining revealed little internal sequestration of CCR1 protein, and CCR1 up-regulation was inhibited by actinomycin D and cycloheximide, indicating that both waves of RSV-CM-induced surface CCR1 expression were dependent on de novo transcription and protein synthesis. Cytokine-neutralizing experiments showed that the effects of RSV-CM were decreased by blocking TNF-alpha (percent inhibition=51+/-2.3% at 36 h peak and 42+/-7.7% at 96 h peak) and to a lesser extent, IL-1 (percent inhibition=32+/-7.2% at 36 h and 23+/-2.9% at 96 h). In summary, RSV-CM causes a biphasic up-regulation of surface CCR1 on monocytes, which is dependent on an intact cytoskeleton, requires new gene transcription and protein synthesis, and is mediated in part by the proinflammatory cytokines TNF-alpha and IL-1.

T helper 1/T helper 2 cytokine imbalance in respiratory syncytial virus infection is associated with increased endogenous plasma cortisol

OBJECTIVE

Cellular immunity has classically been described as the defense mechanism for viral infections. The development of cellular or humoral immune responses will depend on a repertoire of cytokines produced by numerous cells, including CD4+ and CD8+ T cells. These lymphocytes can be subdivided into 2 subsets, T helper 1 (Th1) and Th2, on the basis of the cytokine profiles they synthesize. Type 1 T cells produce interferon gamma (IFN-gamma), an essential cytokine in the viral cell-mediated immune response. Th2 cells selectively produce interleukin 4 (IL-4) and IL-5 that participate in the development of humoral immunity and have a prominent role in immediate-type hypersensitivity. An imbalance in the Th1/Th2 cytokine immune response has been related to pathogenesis of the respiratory syncytial virus (RSV) bronchiolitis and to the severity of the infection. Glucocorticosteroids have a role in inhibiting the IFN-gamma response, acting directly on T cells or indirectly through IL-12. In this way, an increase in plasma cortisol would induce a decrease in the Th1 products with the imbalance between Th1/Th2 cytokines and a shift to Th2 response. We hypothesized that there is a relationship among endogenous cortisol response in acute RSV infection, severity of illness, and decreased Th1 cytokine response.

METHODS

We studied 42 infants under 12 months of age during an acute RSV infection. Twenty-one infants with a median age of 6 months had a severe illness and required hospitalization, whereas 21 with mild diseases with a median age of 7 months were under ambulatory control. All of them had bronchial obstruction evidenced by wheezing and/or hyperinflation on chest radiograph and positive RSV antigen detected by indirect immunofluorescence in nasopharyngeal aspirates. The control group included 21 infants in good health matched by age and gender with median age of 6 months that required blood tests for minor surgery. They were evaluated during a non-RSV epidemic period. Heparinized blood was collected on enrollment from all participating children at 9 am for total leukocyte and differential cell count, determination of lymphocyte subsets, and for intracellular detection of cytokines in single cells; mononuclear cells were cultured to determine in the supernatant cytokine production. In addition, 1 mL of plasma was separated and kept frozen at -20 degrees C for cortisol assay. In the supernatant of the cultured peripheral blood mononuclear cells (PBMCs), we quantified IL-12, IFN-gamma, IL-4, IL-5, and IL-10. Lymphocyte phenotypes and CD4+ and CD8+ T cells with intracellular IL-4, IL-10, and IFN-gamma were analyzed by triple-color immunofluorescence of single cells on a FACScan flow cytometer.

RESULTS

Infants with severe illness had significantly higher plasma cortisol levels than infants with mild disease, and in both groups of infected infants, those were higher than in the control group. A significantly decreased IL-12 and IFN-gamma production by PBMCs and a fall in the percentage of CD4+ T cells expressing IFN-gamma were observed only in the severely affected infants. IL-12 concentrations were 2 pg/mL in severe illness versus 13 pg/mL in mildly infected infants and 12 pg/mL in controls. PBMCs from infants with severe illness produced less IFN-gamma than mildly infected infants and than controls when compared with severe illness. No differences between the 3 groups of infants were observed during the acute phase of the disease for IL-4, IL-5, and IL-10. IL-12 and IFN-gamma production had an inverse correlation with plasma cortisol levels. During severe RSV bronchiolitis, infants developed lymphopenia, and significantly lower eosinophil counts and percentages and absolute counts of CD4+ and CD8+ T cells. Eighty days postinfection, all values had returned to normal levels.

CONCLUSIONS

In this study, we demonstrate that during the acute phase of RSV infection, there is an increase in the level of plasma cortisol that is parallel to the decrease in IL-12 and IFN-gamma production. These findings suggest an association between increased plasma cortisol and a decreased Th1-type response. The increase in plasma cortisol was greater in infants with the more severe symptomatology in association with a lower level of IL-12 and IFN-gamma production. The potential causative role of endogenous cortisol in the imbalance of the Th1/Th2 response observed during severe RSV infection requires additional investigation. Our results suggest that the immunologic changes observed in the more severely ill patients may be partially explained by the increased levels of plasma cortisol. This finding should be taken into consideration when systemic steroids are prescribed to infants infected with the RSV because there is still controversy regarding the efficacy of systemic steroid use in severe bronchiolitis.

Peroxisome-proliferator-activated receptor-gamma agonists inhibit the release of proinflammatory cytokines from RSV-infected epithelial cells

The epithelial cells of the airways are the target cells for respiratory syncytial virus (RSV) infection and the site of the majority of the inflammation associated with the disease. Recently, peroxisome-proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, has been shown to possess anti-inflammatory properties. Therefore, we investigated the role of PPARgamma agonists (15d-PGJ(2), ciglitazone and troglitazone) on the synthesis of RSV-induced cytokine release from RSV-infected human lung epithelial cells (A549). We observed that all PPARgamma ligands inhibited dose-dependently the release of TNF-alpha, GM-CSF, IL-1alpha, IL-6 and the chemokines CXCL8 (IL-8) and CCL5 (RANTES) from RSV-infected A549 cells. Concomitantly, the PPARgamma ligands diminished the cellular amount of mRNA encoding for IL-6, CXCL8 and CCL5 and the RSV-induced binding activity of the transcription factors NF-kappaB (p65/p50) and AP-1 (c-fos), respectively. Our data presented herein suggest a potential application of PPARgamma ligands in the anti-inflammatory treatment of RSV infection.

Possible pathomechanisms of sudden infant death syndrome: key role of chronic hypoxia, infection/inflammation states, cytokine irregularities, and metabolic trauma in genetically predisposed infants

Chronic hypoxia, viral infections/bacterial toxins, inflammation states, biochemical disorders, and genetic abnormalities are the most likely trigger of sudden infant death syndrome (SIDS). Autopsy studies have shown increased pulmonary density of macrophages and markedly more eosinophils in the lungs accompanied by increased T and B lymphocytes. The elevated levels of immunoglobulins, about 20% more muscle in the pulmonary arteries, increased airway smooth muscle cells, and increased fetal hemoglobin and erythropoietin are evidence of chronic hypoxia before death. Other abnormal findings included mucosal immune stimulation of the tracheal wall, duodenal mucosa, and palatine tonsils, and circulating interferon. Low normal or higher blood levels of cortisol often with petechiae on intrathoracic organs, depleted maternal IgG antibodies to endotoxin core (EndoCAb) and early IgM EndoCAb triggered, partial deletions of the C4 gene, and frequent IL-10-592*A polymorphism in SIDS victims as well as possible hypoxia-induced decreased production of antiinflammatory, antiimmune, and antifibrotic cytokine IL-10, may be responsible for the excessive reactions to otherwise harmless infections. In SIDS infants, during chronic hypoxia and times of infection/inflammation, several proinflammatory cytokines are released in large quantities, sometimes also representing a potential source of tissue damage if their production is not sufficiently well controlled, eg, by pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP). These proinflammatory cytokines down-regulate gene expression of major cytochrome P-450 and/or other enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity, thus affecting metabolism of several endogenous lipophilic substances, such as steroids, lipid-soluble vitamins, prostaglandins, leukotrienes, thromboxanes, and exogenous substances. In SIDS victims, chronic hypoxia, TNF-alpha and other inflammatory cytokines, and arachidonic acid (AA) as well as n-3 polyunsaturated fatty acids (FA), stimulated and/or augmented superoxide generation by polymorphonuclear leukocytes, which contributed to tissue damage. Chronic hypoxia, increased amounts of nonheme iron in the liver and adrenals of these infants, enhanced activity of CYP2C9 regarded as the functional source of reactive oxygen species (ROS) in some endothelial cells, and nicotine accumulation in tissues also intensified production of ROS. These increased quantities of proinflammatory cytokines, ROS, AA, and nitric oxide (NO) also resulted in suppression of many CYP450 and other enzymes, eg, phosphoenolpyruvate carboxykinase (PEPCK), an enzyme important in the metabolism of FA during gluconeogenesis and glyceroneogenesis. PEPCK deficit found in SIDS infants (caused also by vitamin A deficiency) and eventually enhanced by PACAP lipolysis of adipocyte triglycerides resulted in an increased FA level in blood because of their impaired reesterification to triacylglycerol in adipocytes. In turn, the overproduction and release of FA into the blood of SIDS victims could lead to the metabolic syndrome and an early phase of type 2 diabetes. This is probably the reason for the secondary overexpression of the hepatic CYP2C8/9 content and activity reported in SIDS infants, which intensified AA metabolism. Pulmonary edema and petechial hemorrhages often present in SIDS victims may be the result of the vascular leak syndrome caused by IL-2 and IFN-alpha. Chronic hypoxia with the release of proinflammatory mediators IL-1alpha, IL-1beta and IL-6, and overloading of the cardiovascular and respiratory systems due to the narrowing airways and small pulmonary arteries of these children could also contribute to the development of these abnormalities. Moreover, chronic hypoxia of SIDS infants induced also production of hypoxia-inducible factor 1alpha (HIF-1alpha), which stimulated synthesis and release of different growth factors by vascular endothelial cells and intensified subclinical inflammatory reactions in the central nervous system, perhaps potentiated also by PACAP and VIP gene mutations. These processes could lead to the development of brainstem gliosis and disorders in the release of neuromediators important for physiologic sleep regulation. All these changes as well as eventual PACAP abnormalities could result in disturbed homeostatic control of the cardiovascular and respiratory responses of SIDS victims, which, combined with the nicotine effects and metabolic trauma, finally lead to death in these often genetically predisposed children.

Animal models of sudden unexplained death

The etiology of sudden infant death syndrome (SIDS) is unknown but thought to be multifactorial. Several animal models have been developed that induce death without pre-existing symptoms and with pathology similar to that seen in SIDS infants; however, the relevance of these animal models to the events leading to SIDS remains elusive, in part because animal models are as varied as the potential causes of SIDS. In addition, it is difficult to find an animal model that can accurately reflect the genetic, developmental and environmental risk factors for SIDS. Comparisons between species can prove difficult but animal models provide a useful tool for evaluating potential mechanisms related to sudden unexplained death. This review focuses on models developed to examine the association of infection and inflammation with mechanisms proposed to explain sudden unexplained death.

Effects of a single intranasal dose of modified-live bovine respiratory syncytial virus vaccine on cytokine messenger RNA expression following viral challenge in calves

OBJECTIVE

To characterize cytokine messenger RNA (mRNA) expression in intranasally vaccinated calves after bovine respiratory syncytial virus (BRSV) challenge.

ANIMALS

Twelve 8- to 12-week-old calves.

PROCEDURES

Calves received modified-live BRSV vaccine (vaccinated) or spent tissue culture medium (mock-vaccinated) intranasally, followed by challenge 30 days later with BRSV, or mock challenge with spent tissue culture medium (mock-challenge controls). Interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) mRNA was measured in lungs, bronchoalveolar lavage (BAL) fluid cells, pharyngeal tonsils, and tracheobronchial lymph nodes, and tumor necrosis factor-alpha (TNF-alpha) mRNA was measured in lungs and BAL fluid cells by reverse transcriptase-competitive polymerase chain reaction assay.

RESULTS

Resistance to clinical signs of disease was conferred in vaccinated calves. Expression of TNF-alpha mRNA in lungs and BAL fluid cells was higher in mock-vaccinated calves than control or vaccinated calves. In the lung, IL-4 mRNA expression was higher in vaccinated calves than control or mock-vaccinated calves. In pharyngeal tonsils, expression of mRNA for IL-4 and IFN-gamma was higher in mock-vaccinated calves than control calves. In tracheobronchial lymph nodes, IFN-gamma mRNA expression was higher in mock-vaccinated calves than vaccinated calves.

CONCLUSIONS AND CLINICAL RELEVANCE

Although vaccinated calves had decreased clinical signs of disease after BRSV challenge, compared with mock-vaccinated calves, this difference was not related to a T helper type 1 bias, as determined by increased expression of interferon-gamma mRNA relative to interleukin-4 mRNA in lungs, BAL fluid cells, or tracheobronchial lymph nodes of vaccinated calves. Pulmonary inflammation was decreased in vaccinated calves as determined by decreased expression of TNF-alpha mRNA.

The VP7 outer capsid protein of rotavirus induces polyclonal B-cell activation

The early response to a homologous rotavirus infection in mice includes a T-cell-independent increase in the number of activated B lymphocytes in the Peyer's patches. The mechanism of this activation has not been previously determined. Since rotavirus has a repetitively arranged triple-layered capsid and repetitively arranged antigens can induce activation of B cells, one or more of the capsid proteins could be responsible for the initial activation of B cells during infection. To address this question, we assessed the ability of rotavirus and virus-like particles to induce B-cell activation in vivo and in vitro. Using infectious rotavirus, inactivated rotavirus, noninfectious but replication-competent virus, and virus-like particles, we determined that neither infectivity nor RNA was necessary for B-cell activation but the presence of the rotavirus outer capsid protein, VP7, was sufficient for murine B-cell activation. Preincubation of the virus with neutralizing VP7 antibodies inhibited B-cell activation. Polymyxin B treatment and boiling of the virus preparation were performed, which ruled out possible lipopolysaccharide contamination as the source of activation and confirmed that the structural conformation of VP7 is important for B-cell activation. These findings indicate that the structure and conformation of the outer capsid protein, VP7, initiate intestinal B-cell activation during rotavirus infection.

Prior airway exposure to allergen increases virus-induced airway hyperresponsiveness

BACKGROUND

Respiratory syncytial virus (RSV) bronchiolitis in early life can lead to changes in airway function, but there are likely additional predisposing factors, such as prior allergen exposure, determining which children develop wheezing and asthma.

OBJECTIVE

To define the effects of prior airway exposure to sensitizing allergen on the development of airway inflammation and hyperresponsiveness (AHR) to subsequent RSV infection.

METHODS

BALB/c mice were exposed to ovalbumin or PBS exclusively through the airways and subsequently infected with RSV or sham-inoculated. AHR, lung inflammation, and the frequency of cytokine-producing T lymphocytes in the lung were determined.

RESULTS

In PBS-exposed mice, RSV infection induced AHR and an increased proportion of TH1-type (IFN-gamma and IL-12) cytokine-producing cells in the lungs. However, in mice previously exposed to ovalbumin through the airways and subsequently infected with RSV, the degree of AHR was significantly increased and was associated with an increased proportion of TH2 (IL-4, IL-5) cytokine-producing T lymphocytes. This response was also associated with an increased accumulation of eosinophils, neutrophils, and CD8+ T cells in the lungs.

CONCLUSIONS

These data suggest that prior airway exposure to allergen may predispose sensitized hosts to a greater degree of altered airway function upon subsequent respiratory viral infection.

Cytokine levels during symptomatic viral upper respiratory tract infection

BACKGROUND

Previous studies suggest a role for locally produced proinflammatory cytokines in the development and expression of illness during experimental infection with a variety of respiratory viruses. However, most of these studies fail to make comparisons between symptomatic and asymptomatic infected subjects.

OBJECTIVE

To compare the pattern of nasal cytokine elaboration in asymptomatic and symptomatic subjects experimentally infected with rhinovirus-39 (RV-39).

METHODS

Healthy adults underwent experimental intranasal inoculation with a safety-tested clinical isolate of RV-39. Nasal lavages were collected, nasal symptoms were recorded, and expelled nasal secretions were weighed before and then daily for 6 days after challenge. Nasal lavages were submitted for viral culture and assayed for cytokine protein levels by enzyme-linked immunosorbent assay.

RESULTS

Twenty-nine subjects were enrolled in the study. All subjects were infected as evidenced by viral shedding and/or seroconversion. Sixteen subjects were symptomatic and 13 were asymptomatic as evaluated by subject self-report. During infection, significant increases in mean levels of nasal interleukin 6 (IL-6) (P = .01) and IL-1 (P = .02) were observed in symptomatic but not asymptomatic subjects. In symptomatic subjects, these increases were temporally related to the development of nasal symptoms and production of secretions. Mean levels of IL-8, IL-10, and tumor necrosis factor a were not increased in either group during infection.

CONCLUSIONS

The results of this study demonstrate elevations in certain locally produced cytokines during symptomatic but not asymptomatic respiratory infection with RV-39. Future studies using selected anticytokine therapies may help elucidate the precise role of cytokines in mediating disease expression.

Prevention of otitis media caused by viral upper respiratory tract infection: vaccines, antivirals, and other approaches

Otitis media (OM) imposes significant morbidity on the pediatric age group and a large financial burden on the general population. Because standard medical treatments are not highly efficacious in resolving the accompanying middle ear (ME) inflammation, a goal of current research is OM prevention. Past studies show that new episodes of OM are usually a complication of viral upper respiratory infection (vURI), and therefore, a rational approach to achieving that goal is to develop intervention strategies that target vURI-associated OM. However, past experiences with antibiotics show that, in the absence of well-defined treatment protocols that maximize expected efficacy, the adoption of prophylactic or active treatments for OM can have negative consequences for the patient and for the general population. In this review, we discuss the hypothesized mechanisms by which a vURI is translated into an acute OM episode and describe different strategies for aborting that process. Limitations to deployment of each strategy are outlined.

Cytokine gene polymorphisms moderate illness severity in infants with respiratory syncytial virus infection

Illness severity and frequency of complications in infants with respiratory syncytial virus (RSV) infection may be influenced by the local elaboration of cytokines. Cytokine gene polymorphisms moderate severity of illness in various inflammatory and infectious diseases. We performed cytokine genotyping on 77 infants hospitalized with confirmed RSV infection to determine whether specific cytokine gene polymorphisms are associated with illness severity or complications. DNA was extracted from buccal brushings and assayed for tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-6 and IL-10, and transforming growth factor (TGF)-beta1 genotypes using polymerase chain reaction-sequence-specific primer technology. Clinical outcomes consisted of severity scores of lower respiratory illness, blood oxygen saturation, lengths of oxygen supplementation, and intensive care unit (ICU) and hospital stays, and the presence or absence of pneumonia and otitis media. IFN-gamma genotype was related to severity of lower respiratory illness, duration of ICU stay, and frequency of otitis media. Additionally, IL-6 genotype was related to the length of oxygen (O(2)) supplementation and hospital stay, IL-10 genotype to the frequency of pneumonia, and TGF-beta1 genotype to O(2) saturations at presentation. There were no associations between TNF-alpha genotype and any of the outcome parameters. These results demonstrate that certain cytokine gene polymorphisms contribute to illness severity and complications during RSV infection in infants. If future prospective studies confirm these observations, cytokine genotyping may be a useful tool for identifying "at risk" infants who may benefit from the selective use of preventive or early intervention treatments for RSV.

Cytokine gene polymorphisms moderate responses to respiratory syncytial virus in adults

Immune responses and illness severity during viral upper respiratory infections may be influenced by the local elaboration of cytokines. Cytokine gene polymorphisms moderate immune responses and severity of illness in various inflammatory and infectious diseases. We performed cytokine genotyping on 29 adults experimentally inoculated with respiratory syncytial virus (RSV) to determine whether specific cytokine gene polymorphisms are associated with immune responses or illness severity. DNA was extracted from leukocytes and assayed for TNF-alpha, IFN-gamma, IL-6, IL-10 and TGF-beta1 genotypes using polymerase chain reaction-sequence-specific primer technology. Outcomes consisted of baseline and convalescent RSV-specific serum IgG and nasal IgA titers, nasal secretion weights, nasal, throat and general symptom scores, and nasal cytokine protein levels. IFN-gamma genotype was directly related with the frequency of subjects having at least a four-fold increase in RSV-specific serum IgG and TNF-alpha genotype was inversely associated with the frequency of subjects having at least a twofold increase in RSV-specific nasal IgA. Additionally, IL-6 genotype was predictive of certain measures of illness expression, while IFN-gamma genotype predicted IL-1 protein levels, and TNF-alpha genotype predicted IL-6 and IL-8 protein levels in nasal lavage fluids. There were no associations between IL-10 or TGF-beta1 and any of the outcome parameters. These results suggest that certain cytokine gene polymorphisms moderate immune responses and illness severity in adults experimentally exposed to RSV.

Cytokines and chemokines in respiratory secretion and severity of disease in infants with respiratory syncytial virus (RSV) infection

BACKGROUND

little is known about inflammatory mediators (IM); like cytokines, chemokines and receptors; in respiratory secretion as possible indicators of the severity of respiratory syncytial virus (RSV) disease. Nor have systematic studies been published on the ratios between IM as such indicators.

OBJECTIVE

to define the role of IM ratios as possible indicators of the severity of RSV disease.

STUDY DESIGN

about 46 infants aged 0-9 months with acute RSV infections were studied. Prematurity (PM) and/or underlying disease (UD) were present in 11 of them. The concentrations of seven different IM were measured by ELISA in samples of nasopharyngeal secretions (NPS), four cytokines; IL-1, IL-6, IL-10 and TNF-alpha; the cytokine receptor TNF-R1 and the chemokines; IL-8 and RANTES. 21 IM ratios were calculated from these concentrations. The patients were assigned a clinical score (CS) ranging from 0 to 3 according to the severity of disease.

RESULTS

when 25 patients with severe disease (CS 2-3) and 21 patients with mild disease (CS 0-1) were compared with respect to different IM ratios, three ratios were related to severity of disease: IL-1/RANTES, IL-8/RANTES and TNF-R1/RANTES. When 12 patients with mild disease were compared with 16 patients with severe disease, omitting patients more than 5 months of age and patients with PM and/or UD, the following IM ratios were related to severity of disease: TNF-R1/RANTES, IL-8/RANTES and RANTES/IL-10.

CONCLUSION

of 21 IM ratios studied, TNF-R1/RANTES was related to severity of disease with greatest consistency.

Viral rhinitis

Viral rhinitis is a common, morbid, and costly malady, often complicated by otitis media, sinusitis, and asthma. Current therapies are relatively ineffective and aimed at reducing symptoms rather than moderating underlying mechanisms. Nasal elevations of proinflammatory cytokines track symptom expression during viral rhinitis, and it is hypothesized that these chemicals orchestrate a common response to infection with many different viruses that cause rhinitis. Also, recent evidence supports a role for neurogenic inflammation in the development of complications. Future studies should dissect the role of proinflammatory cytokines and neuropeptides in the expression of symptoms, signs, pathophysiologies, and complications of viral rhinitis.

Increased pulmonary secretion of tumor necrosis factor-alpha in calves experimentally infected with bovine respiratory syncytial virus

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease among calves in the Danish cattle industry. An experimental BRSV infection model was used to study the pathogenesis of the disease in calves. Broncho alveolar lung lavage (BAL) was performed on 28 Jersey calves, of which 23 were experimentally infected with BRSV and five were given a mock inoculum. The presence of the cytokine tumor necrosis factor alpha (TNF-alpha) in the BAL fluids was detected and quantified by a capture ELISA. TNF-alpha was detected in 21 of the infected animals. The amount of TNF-alpha in the BAL fluid of calves killed post inoculation day (PID) 2 and 4 was at the same very low level as in the uninfected control animals. Large amounts of TNF-alpha were detected on PID 6, maximum levels of TNF-alpha were reached on PID 7, and smaller amounts of TNF-alpha were seen on PID 8. The high levels of TNF-alpha appeared on the days where severe lung lesions and clinical signs were obvious and the amounts of BRSV-antigen were at their greatest. Although Pasteurellaceae were isolated from some of the BRSV-infected calves, calves treated with antibiotics before and through the whole period of the infection, as well as BRSV-infected calves free of bacteria reached the same level of TNF-alpha as animals from which bacteria were isolated from the lungs. It is concluded that significant quantities of TNF-alpha are produced in the lungs of the calves on PID 6-7 of BRSV infection. The involvement of TNF-alpha in the pathogenesis of, as well as the anti-viral immune response against, BRSV infection is discussed.

Sudden infant death syndrome: a toxic response

Causes of sudden infant death syndrome (SIDS) remain elusive. Much of the current literature points to an infectious cause with a role for proinflammatory cytokines and septic shock in stimulating an overwhelming response in an infant. This article reviews the literature and possible causes of this devastating condition.

Role of viruses in the pathogenesis of acute otitis media

To date there is ample evidence suggesting a crucial role for respiratory viruses in the pathogenesis of AOM. Respiratory viral infection appears to initiate the cascade of events that finally leads to development of AOM (Fig. 1). The pathogenesis of AOM is complicated, involving a network of factors, some probably not yet identified, which affect each other in a time-dependent manner. Increased knowledge of the detailed mechanisms of viral infection, the host inflammatory response during URI and the interaction between viruses and bacteria could lead to major advances in the prevention of AOM.

Viral-Bacterial Synergy in Otitis Media: Implications for Management

Despite the extensive use of broad-spectrum antibiotics, poor clinical response to the treatment of acute otitis media is common. Evidence derived from numerous studies during the past two decades supports a crucial role for respiratory viruses in the etiology and pathogenesis of acute otitis media, and recent studies indicate that viruses may also have a profound adverse effect on the resolution of this disease. Viruses seem to interact with bacteria and enhance the local inflammatory process in the middle ear. Effective adjuvant therapies are needed to improve outcome in children with otitis media. Increasing knowledge of the role of viruses, viral-bacterial interaction, and host inflammatory mechanisms in otitis media may lead to major improvements in the management of this disease.

Sudden infant death syndrome, virus infections and cytokines

Many epidemiological risk factors identified for sudden infant death syndrome (SIDS) suggest a viral aetiology, e.g. exposure to cigarette smoke and winter peak, mild respiratory symptoms. Virus infections and bacterial toxins induce cytokine activity and it has been suggested that uncontrolled inflammatory mediators could be involved in some cases of SIDS. The aim of this review was to assess the evidence for virus infection in SIDS and to examine those findings in relation to individual variations in cytokine responses and various pathophysiological mechanisms proposed for SIDS such as sleep derangement, hypoxia, cardiac arrhythmia, vascular hypotonicity and hypoglycaemia.

Quantification of cytokines and inflammatory mediators in samples of nasopharyngeal secretions with unknown dilution

In the study of inflammatory mechanisms in the upper respiratory tract, the unknown dilution of collected samples of nasal secretions poses a serious problem for interpretation of the measured concentrations of various substances in the specimens. We investigated the magnitude of the dilution problem in a true clinical research situation and determined the validity of using the levels of total protein, albumin, and secretory IgA in nasal secretions to correct for the unknown dilution. The study samples consisted of simultaneously obtained nasopharyngeal aspirates and nasal lavage specimens from 52 children with upper respiratory tract infection. The dilution factors of the nasal lavage specimens varied widely between 1.8 and 432 (median, 11.2). Of the three proteins studied, total protein had the narrowest inter-subject variation in the nasal secretions of the children and thus seemed to provide the best standardization method for comparing levels of substances between individuals. Concentrations of IL-6 standardized with total protein correlated significantly better with the true IL-6 concentrations in the nasal secretions than did IL-6 levels measured in the nasal lavage specimens without standardization (p = 0.049). These findings suggest that the most common current practice of measuring substances in nasopharyngeal specimens, i.e. measuring without correction for the dilution, may produce "false-negative" results. Potentially important information on inflammatory mechanisms may be undetected if false-negative results mask real differences between groups. The use of exogenous markers of dilution might improve the accuracy of quantifying substances in nasal secretions.

Elevated cytokine concentrations in the nasopharyngeal and tracheal secretions of children with respiratory syncytial virus disease

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in infants. The role of inflammatory mediators in the pathogenesis of RSV disease is not well-understood. The present study was designed (1) to determine whether RANTES (regulated on activation, normal T cell expressed and presumably secreted), macrophage-inflammatory protein-1-alpha (MIP-1-alpha), interleukin (IL)-6, IL-8 and IL-10 can be detected in respiratory secretions of children with RSV infection and (2) to assess whether the concentrations of these cytokines in respiratory secretions correlate with white blood cell (WBC) counts and RSV concentrations and with disease severity.

METHODS

During the 1996 to 1997 RSV season, we studied prospectively 14 intubated and 14 nonintubated children hospitalized with RSV disease. Nasal wash (NW) and tracheal aspirate (TA) samples were obtained from intubated patients on Hospital Days 1, 3 and 5. NW samples were obtained from nonintubated patients on hospital days 1 and 3. Seven healthy children undergoing elective surgery served as controls. All samples were analyzed for: (1) WBC and differential counts; (2) concentrations of RANTES, MIP-1-alpha, IL-6, IL-8 and IL-10; and (3) quantitative RSV cultures, except in control patients.

RESULTS

RANTES, MIP-1-alpha, IL-6, IL-8 and IL-10 were detected in NW and TA samples from all children with RSV infection. The concentrations of these cytokines in samples obtained from children with RSV infection were significantly greater than those in samples obtained from control children. NW WBC counts significantly correlated with NW RANTES, IL-6, IL-8 and IL-10 concentrations, whereas TA WBC counts significantly correlated with TA IL-6, IL-8, IL-10 and MIP-1-alpha concentrations. NW RSV concentrations correlated with NW WBC counts and with NW cytokine concentrations. Among children with RSV infection nonintubated patients had greater NW WBC counts and NW RANTES concentrations than intubated patients. TA RANTES, IL-8 and IL-10 concentrations inversely correlated with clinical markers of RSV disease severity.

CONCLUSION

The presence of cytokines in NW and TA samples of children with RSV infection suggests that they have a role in mediating the respiratory tract inflammation induced by RSV. These observations could have implications for designing new therapeutic strategies directed at immunomodulation of RSV disease.

Severity of respiratory syncytial virus disease related to type and genotype of virus and to cytokine values in nasopharyngeal secretions

BACKGROUND

Investigations concerning the severity of respiratory syncytial virus (RSV) disease as related to (1) RSV type and genotype determined respectively by PCR and restriction enzyme analysis and (2) interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) values in samples of nasopharyngeal secretion (NPS) have not been previously reported.

METHODS

We prospectively studied 105 RSV infections in the lower respiratory tract of infants and young children admitted to a pediatric department in Copenhagen during three winter seasons, 1993, 1994 and 1995. RSV strains were typed and genotyped, respectively, by PCR and nucleic acid restriction analysis and correlated to the severity of the disease. The ratio IL-6:TNF-alpha, determined from IL-6- and TNF-alpha values in samples of NPS, was related to the severity of the disease. Concentrations of IL-6 and of TNF-alpha were determined in serum samples taken during 5 weeks after the onset of illness.

RESULTS

Type B infections produced more severe disease than did type A infections, as assessed on the length of the hospital stay, use of respiratory support and the presence of an infiltrate on a chest radiograph. This difference was age-related. It was observed in infants 0 to 5 months old, but not in older age groups. Type B genotype B1122 produced more severe disease than type A genotype A2311 in infants 0 to 11 months old. Increased serum concentrations of IL-6 and TNF-alpha were detected in samples taken 1 to 2 days after the onset of illness. Whereas TNF-alpha serum concentrations remained high, IL-6 serum concentrations decreased during the following 3 to 4 weeks. The IL-6:TNF-alpha ratio in samples of NPS was related to the severity of the disease. A high ratio was related to a low severity.

CONCLUSIONS

The severity of disease in patients admitted with acute RSV infections can be correlated to the RSV type as determined by PCR, to the RSV genotype as determined by nucleic acid restriction analysis and to the ratio IL-6:TNF-alpha in NPS.

Respiratory syncytial virus infection of human alveolar epithelial cells enhances interferon regulatory factor 1 and interleukin-1beta-converting enzyme gene expression but does not cause apoptosis

The induction kinetics of the transcriptional activities of interferon regulatory factor 1 (IRF-1), interleukin-1beta-converting enzyme (ICE), and CPP32 by respiratory syncytial virus (RSV) infection of human type II alveolar epithelial cells (A549 cells) were analyzed semiquantitatively by reverse transcriptase PCR. The appearance of ICE and CPP32 protein in cell lysate was examined by Western blotting analysis. The induction of apoptosis by RSV infection was examined by the appearance of DNA fragmentation detected by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling. RSV moderately enhanced IRF-1 mRNA as early as 4 h after infection, and this enhancement lasted several hours. Following induction of the IRF-1 gene, ICE gene expression increased significantly, and an increase of ICE protein was observed in the RSV-infected cell lysate. These increments were observed in cells treated with live RSV but not in cells treated with inactivated RSV or control antigen. However, no infection-specific increase of CPP32 gene expression or the protein was observed. No nucleosomal fragmentation was observed in RSV-infected cells during the whole course of infection, despite the appearance of extensive cytopathic change and cell death. These observations suggest that RSV infection of human alveolar epithelial cells induces the ICE gene and its protein as a result of increased IRF-1 induction but that the increased ICE was insufficient to cause apoptosis in the RSV-infected cells. ICE might not be able to activate CPP32, which is thought to be the more important protease for apoptosis.

Autocrine regulation and experimental modulation of interleukin-6 expression by human pulmonary epithelial cells infected with respiratory syncytial virus

The mechanisms of regulation of interleukin-6 (IL-6) production in respiratory syncytial virus (RSV)-infected respiratory epithelial cells were evaluated in A549 cell cultures. Incubation with purified RSV resulted in significant production of IL-1alpha, IL-1beta, IL-6, and tumor necrosis factor alpha (TNF-alpha). Addition of saturating concentrations of neutralizing antibodies against IL-1alpha, IL-1beta, or TNF-alpha into purified RSV-infected cell cultures resulted in a significant inhibition of IL-6 production, although anti-IL-1alpha antibody had the most predominant effect (80% inhibition). Anti-IL-1alpha antibody also almost completely blocked the expression of mRNA for IL-6. Addition of therapeutic concentrations of dexamethasone (1 microM) or ribavirin (90 microg/ml), an antiviral agent, also significantly inhibited the synthesis of IL-6. Hence, in clinical settings, pharmacological agents such as the specific antagonists of IL-6-inducing cytokines, as well as dexamethasone and ribavirin, could be used to modulate IL-6 production.

Respiratory syncytial virus infection of neonatal monocytes stimulates synthesis of interferon regulatory factor 1 and interleukin-1beta (IL-1beta)-converting enzyme and secretion of IL-1beta

Interleukin-1beta (IL-1beta) production in response to respiratory syncytial virus (RSV) was investigated in normal neonate monocytes. Intracellular or culture supernatant IL-1beta protein levels were measured by enzyme immunoassay. The expression of mRNAs for interferon regulatory factor 1 (IRF-1), IL-1beta-converting enzyme (ICE), and IL-1beta in the cells was analyzed semiquantitatively by reverse transcriptase-PCR. Before RSV exposure, some IRF-1, ICE, and IL-1beta transcripts were already expressed in the monocytes. The levels of these transcripts increased significantly 2 h after RSV exposure compared with those in mock-infected cells. At that time, significantly higher intracellular IL-1beta protein levels were observed in RSV-exposed cells. After 20 h of RSV exposure, quantities of soluble IL-1beta secreted from RSV-exposed cells were moderately higher than those from noninfected cells. These observations suggest that RSV infection of neonatal monocytes triggers enhanced transcription and increased translation of the IL-1beta gene and increased secretion of the soluble protein. The later phase of these processes may be promoted by ICE activity, which was upregulated by increased IRF-1. The increase in IRF-1 activity may also result from RSV infection.

Role of viruses in middle-ear disease

Taken together, there is ample evidence suggesting a role for viruses in the pathogenesis of OM. This evidence comes from numerous studies performed in animals and in vitro cell cultures, as well as in adults and children with URI and OM. Viruses induce host immune and inflammatory responses that result in pathology of the ET and the middle ear, and predispose the host in various ways to secondary bacterial infection. A suggested mechanism for the pathogenesis of OM following respiratory viral infection is presented in Figure 1.