Effect Of Respiratory Syncytial Virus Research Articles

Difficult questions about long COVID in children

Difficult questions about long COVID in children

The Effects of Respiratory syncytial virus prophylaxis Application Protocol on Patient Compliance and Clinical Outcomes in Congenital Heart Diseases

Giriş: Palivizumab, yüksek riskli çocuklarda respiratuar sinsisyal virüs (RSV) önlenmesinde iyi tolere edilen, güvenli bir monoklonal antikordur. Hastaların zamanında ve tam doz proflaksi alabilmeleri için anne ve babanın uyumu son derece önemlidir. RSV proflaksisinde hasta uyumunu ve klinik sonuçlarını değerlendiren makaleler bulunmaktadır. Her kliniğin kendi takip ve uygulama protokolü bulunmaktadır ancak kullanılan protokoller, hasta uyumu ve doz tamamlanması ile ilgili bir çalışma bulunmamaktadır.Hastalar ve Yöntem: Ekim 2016-Mart 2018 tarihleri arasında çocuk kardiyoloji polikliniğinde RSV proflaksisi endikasyonu almış hemodinamik olarak anlamlı KKH’na sahip 2 yaş altı toplam 60 hastaya ait veriler çocuk kardiyoloji poliklinik ve servis kayıtlarından retrospektif olarak incelendi. 2 farklı sezonda, proflaksi endikasyonu alan ve 2 farklı protokol ile takip edilen hastalar uyum ve klinik sonuçlar açısından birbiriyle karşılaştırıldı. Tam uyum, sezon boyunca 5 aylık dönemde, 30 gün aralarla en az 4 doz palivizumab uygulaması yapılması olarak tanımlandı.Bulgular: Ekim 2016- Mart 2017 sezonunda, 5 aylık dönemde uygulan ortalama doz 1 ± 0.2 doz idi ve tam hasta uyumu %10 olarak bulundu. Doz aralıkları 37.2 ± 6.15 gün olarak bulundu. 10 hastada (% 40) ASYE nedeniyle hastaneye yatış ve RSV izolasyonu mevcuttu. Ekim 2017-Mart 2018 sezonunda yapılan protokol değişikliği sonrası, hasta uyumu %100 olarak değerlendirildi, ASYE nedeniyle acil servis başvurusu ve hastaneye yatış gereksinimi tespit edilmedi. Sonuç: Palivizumab proflaksisinde doz tamamlanması ve aralığı uyumunu arttırmak RSV’ye bağlı hastane yatışlarını önemli ölçülde azaltmaktadır. Detaylı ve iyi organize edilmiş takip ve uygulama protokolleri hazırlanmak uyumu arttırmada son derece önemlidir.

The Effect of Respiratory Syncytial Virus on the Severity of Acute Bronchiolitis in Hospitalized Infants: A Prospective Study from Turkey

Objectives: Respiratory syncytial virus (RSV) is a major cause of respiratory infections in infants and children. The aim of this study was to evaluate clinical significance of respiratory infections as single pathogen RSV, respiratory viruses with RSV and those with bronchiolitis caused by other respiratory viruses. Methods: A total of 316 throat swabs were collected from children diagnosed with acute bronchiolitis. Real-time polymerase chain reaction was used to identify the viruses in the samples. The subjects were divided into three groups: single pathogen RSV, agents with RSV and agents without RSV. Binary logistic regression analysis was used to evaluate the corelation between single and multiple RSV infection group and infections without RSV group for parameters including age, wheezing, supplemental oxygen therapy. Results: The overall positivity for viruses in the study was found to be 75% with a co-infection rate of 34.2%. Compared to children with RSV alone, children with any other agents accompanying RSV, were not very likely to have fever, wheezing or supplemental oxygen therapy. Conclusions: The findings of our study suggest that RSV still represents a large burden of bronchiolitis since it is associated with the hospitalization of children, particularly those less than six months old. We can not foresee the clinical presentation of specific agent or agents in connection to being with or without RSV in infants with any level of bronchiolitis. The study agrees with the concept that co infections with or without RSV do not increase the severity of the disease.

Effect of respiratory syncytial virus on the growth of hepatocellular carcinoma cell-lines.

In several reports, the respiratory syncytial virus (RSV) was identified as an oncolytic virus in cancer cells (e.g., lung and prostate cancer). However, the effects of RSV in hepatocellular carcinoma (HCC) cells have not yet been investigated. Here, we observed the inhibitory effects of RSV infection in HCC cell-lines. Cell growth was significantly decreased by RSV infection in BNL-HCC, Hep3B, Huh-7 and SNU-739 cells. After RSV infection, plaque formation and syncytial formation were observed in affected Hep3B and Huh-7 cells. RSV protein-expression was also detected in Hep3B and Huh-7 cells; however, only Huh-7 cells showed apoptosis after RSV infection. Furthermore, inhibition of cell migration by RSV infection was observed in BNL-HCC, Hep3B, Huh-7 and SNU-739 cells. Therefore, further investigation is required to clarify the molecular mechanism of RSV-mediated inhibition of HCC cell growth, and to develop potential RSV oncolytic viro-therapeutics. [BMB Reports 2015; 48(10): 565-570]

Interference between respiratory syncytial virus and rhinovirus in respiratory tract infections in children

An acute viral respiratory tract infection might prevent infections by other viruses because of the antiviral innate immune response. However, with the use of PCR methods, simultaneous detection of two or more respiratory viruses is frequent. We analysed the effect of respiratory syncytial virus (RSV) infection on the occurrence of simultaneous rhinovirus (RV) infection in children within a birth cohort study setting. We used PCR for virus detection in nasal swabs collected from children with an acute respiratory tract infection at the age of 0–24 months and from healthy control children, who were matched for age and date of sample collection. Of 226 children with RSV infections, 18 (8.0%) had co-infections with RV, whereas RV was detected in 31 (14%) of 226 control children (p 0.049 by chi-square test). Adjustment for sex, number of siblings and socio-economic status strengthened the negative association between RSV and RV (OR 0.46, 95% CI 0.24–0.90; p 0.02). The median durations of symptoms (cough, rhinorrhoea, or fever) were 11 days in children with single RSV infections and 14 days in children with RSV–RV co-infections (p 0.02). Our results suggest that the presence of RSV reduces the probability of RV infection, but that, if a co-infection occurs, both viruses cause clinical symptoms.

Association of respiratory viruses with outcomes of severe childhood pneumonia in Botswana.

BackgroundThe highest incidence of childhood acute lower respiratory tract infection (ALRI) is in low- and middle-income countries. Few studies examined whether detection of respiratory viruses predicts ALRI outcomes in these settings.MethodsWe conducted prospective cohort and case-control studies of children 1-23 months of age in Botswana. Cases met clinical criteria for pneumonia and were recruited within six hours of presentation to a referral hospital. Controls were children without pneumonia matched to cases by primary care clinic and date of enrollment. Nasopharyngeal specimens were tested for respiratory viruses using polymerase chain reaction. We compared detection rates of specific viruses in matched case-control pairs. We examined the effect of respiratory syncytial virus (RSV) and other respiratory viruses on pneumonia outcomes.ResultsBetween April 2012 and August 2014, we enrolled 310 cases, of which 133 had matched controls. Median ages of cases and controls were 6.1 and 6.4 months, respectively. One or more viruses were detected from 75% of cases and 34% of controls. RSV and human metapneumovirus were more frequent among cases than controls, but only enterovirus/rhinovirus was detected from asymptomatic controls. Compared with non-RSV viruses, RSV was associated with an increased risk of treatment failure at 48 hours [risk ratio (RR): 1.85; 95% confidence interval (CI): 1.20, 2.84], more days of respiratory support [mean difference (MD): 1.26 days; 95% CI: 0.30, 2.22 days], and longer duration of hospitalization [MD: 1.35 days; 95% CI: 0.20, 2.50 days], but lower in-hospital mortality [RR: 0.09; 95% CI: 0.01, 0.80] in children with pneumonia.ConclusionsRespiratory viruses were detected from most children hospitalized with ALRI in Botswana, but only RSV and human metapneumovirus were more frequent than among children without ALRI. Detection of RSV from children with ALRI predicted a protracted illness course but lower mortality compared with non-RSV viruses.

Viperin protein expression inhibits the late stage of respiratory syncytial virus morphogenesis

We examined the effect of respiratory syncytial virus (RSV) infection on viperin protein expression in the permissive HEp2 and non-permissive RAW 264.7 macrophage cell lines. In RSV-infected HEp2 cells low levels of the viperin protein was localized to the virus-induced inclusion bodies and did not impair virus transmission in these cells. In contrast, RSV-infected RAW 264.7 cells increased expression of the STAT1 protein occurred at between 6 and 12h post-infection, which coincided with the appearance of P-STAT1. A relatively high level of viperin protein expression was detected in infected RAW 264.7 cells, and it was extensively localized throughout the cytoplasm of infected cells. The effect of early viperin protein expression on RSV infection in cells that are normally permissive to RSV cultivation was examined by using either transient transfected HEp2 cells or stable transfected HeLa cells that expressed the viperin protein. The early expression of viperin in HeLa cells did not prevent virus infection, and no significant inhibitory effect on either virus protein expression or targeting of virus proteins to the cell surface was noted. However, while inclusion body formation was not inhibited, early viperin protein expression was associated with the inhibition of virus filament formation and reduced cell-to-cell virus transmission. Inhibition of virus filament formation was also observed in HEp2 cells expressing viperin. Collectively our data suggested that viperin impaired RSV transmission by inhibiting virus filament formation, providing a basis for its anti-virus activity in RSV-infected cells.

Viral disruption of olfactory progenitors is exacerbated in allergic mice.

Upper airway viral infection in patients with airway allergy often exacerbates olfactory dysfunction, but the mechanism for this exacerbation remains unclear. Here, we examined the effects of respiratory syncytial virus (RSV) infection, in the presence or absence of airway allergy, on olfactory receptor neurons (ORNs) and their progenitors in mice. Immunohistological analyses revealed that cockroach allergen (CRA)-induced airway allergy alone did not affect the number of OMP(+) mature ORNs and SOX2(+) ORN progenitors. Intranasal RSV line 19 infection in allergy-free mice resulted in a transient decrease in SOX2(+) ORN progenitors without affecting OMP(+) ORNs. In contrast, the RSV-induced decrease in SOX2(+) ORN progenitors was exacerbated and prolonged in allergic mice, which resulted in eventual loss of OMP(+) ORNs. In the allergic mice, reduction of RSV in the olfactory epithelium was delayed as compared with allergy-free mice. These results suggest that ORN progenitors were impaired by RSV infection and that airway allergy exacerbated damage to ORN progenitors by reducing viral clearance.

Dual effects of respiratory syncytial virus infections on airway inflammation by regulation of Th17/Treg responses in ovalbumin-challenged mice.

We investigated the effects of respiratory syncytial virus (RSV) infections on ovalbumin (OVA)-challenged mice via regulation of Th17/Treg cell responses. BALB/c mice were challenged with OVA, followed by RSV infections twice. In OVA-challenged mice, the secretion of Th2/Th17-type cytokines, airway hyperresponsiveness and inflammation were significantly inhibited by initial RSV infection. Moreover, the in vivo findings demonstrated that initial RSV infection reversed the imbalance of Th17/Treg responses. In contrast, RSV re-infection strengthened Th2/Th17-type cytokine secretion, airway hyperresponsiveness, and inflammation, especially for lymphocyte infiltration in OVA-challenged mice. Meanwhile, RSV re-infection enhanced the imbalanced Th17/Treg responses. Upon all results reveal that RSV-induced respiratory infections may lead to dual effects pertaining to allergic airway inflammation by regulation of Th17/Treg responses.

The Oncolytic Effect of Respiratory Syncytial Virus (RSV) in Human Skin Cancer Cell Line, A431

BackgroundOncolytic viruses have become of noticeable interest as a novel biological approach for selectively infecting cancer cells and triggering apoptosis in a number of malignant cells. Many researches are devoted to characterize more viruses with oncolytic properties.ObjectivesEvidences on the oncolytic feature of respiratory syncytial virus (RSV) are conflicting; therefore, this study was designed to elucidate the possible role of RSV on the modulation of cell growth and apoptosis in the skin cancer cells.Materials and MethodsPlaque assay was used to determine RSV titers. The cytotoxic effect of RSV in A431 (skin carcinoma cell line) was determined using MTT assay. The detection of apoptosis was performed via Annexin-V-FITC staining method and analyzed with flow cytometry.ResultsThe results indicated that A431 cell growth was inhibited following infection by RSV in a dose- and time-dependent manner. The most growth inhibitory effect of RSV was occurred at the MOI of 3, and 48 hour after infection. The inhibitory effect of RSV on the cell growth was accompanied by the induction of apoptosis in the skin cancer cells. The percentages of early and late apoptotic cells were increased following exposure to RSV in a concentration- and time-dependent manner.ConclusionsThis study delineated the beneficial role of RSV for growth regulation of skin cancer cells and highlighted the involvement of RSV in the induction of apoptosis in A431 cells. These findings might conduct evidence into the oncolytic properties of RSV in the skin cancer. Further studies are required to indicate intracellular targets for RSV-induced apoptosis in skin cancer cells.

The Anti-Apoptotic Effect of Respiratory Syncytial Virus on Human Peripheral Blood Neutrophils is Mediated by a Monocyte Derived Soluble Factor

Respiratory Syncytial Virus (RSV) causes annual epidemics of respiratory disease particularly affecting infants. The associated airway inflammation is characterized by an intense neutrophilia. This neutrophilic inflammation appears to be responsible for much of the pathology and symptoms. Previous work from our group had shown that there are factors within the airways of infants with RSV bronchiolitis that inhibit neutrophil apoptosis. This study was undertaken to determine if RSV can directly affect neutrophil survival.Neutrophils were isolated from citrated venous blood (collected from healthy adult volunteers) by discontinuous plasma: Percoll gradient centrifugation and, in some experiments, further purified by negative immunomagnetic bead selection. The effect of RSV on neutrophil survival was measured by Annexin V-PE /To-Pro-3 staining and by morphological changes, using Dif-Quick staining of cytospins.Inhibition of neutrophil apoptosis was observed in neutrophils isolated by standard plasma:Percoll gradient when exposed to RSV but not in ultra pure neutrophil preparations. Adding monocytes back to ultra purified preparations restored the effect. The inhibition of apoptosis was observed with both active and UV inactivated virus. The effect is dependent on a soluble factor and appears to be dependent on CD14 receptors on the monocytes.

The effect of respiratory syncytial virus on subsequent recurrent wheezing in atopic and nonatopic children

BackgroundAlthough respiratory syncytial virus (RSV) lower respiratory tract infections (LRTIs) in early life are followed by later airway hyperreactivity, it is unclear whether there is a causal relationship between this and an atopic diathesis.ObjectivesTo separate the effects of RSV LRTI and an atopic diathesis on subsequent recurrent wheezing, we examined the protective effect of previous palivizumab administration against subsequent recurrent wheeze in infants with and without a family history of atopy.MethodsA prospective multicenter, matched, double cohort study was conducted in 27 centers in Europe and Canada. The rates of physician-diagnosed recurrent wheezing in premature infants <36 weeks gestation who had received palivizumab in the first year of life were compared to those of gestational age–matched controls.ResultsThe relative protective effect of palivizumab on physician-diagnosed recurrent wheezing through the ages of 2 to 5 years was 68% in those with no family history of asthma (odds ratio, 0.32; (95% CI, 0.14-0.75; N = 146 palivizumab-treated, 171 untreated) and 80% in those with no family history of atopy or food allergies (odds ratio, 0.20; 95% CI, 0.07-0.59; N = 101 palivizumab-treated, 100 untreated). In contrast, there was no effect of palivizumab on subsequent recurrent wheezing in the 90 children with a family history of atopy or food allergies compared to 130 untreated infants with atopic families.ConclusionRespiratory syncytial virus prophylaxis in nonatopic children decreases by 80% the relative risk of recurrent wheezing but does not have any effect in infants with an atopic family history. This suggests that RSV predisposes to recurrent wheezing in an atopy-independent mechanism.

Assessing the burden of paediatric influenza in Europe: the European Paediatric Influenza Analysis (EPIA) project.

The European Paediatric Influenza Analysis (EPIA) project is a multi-country project that was created to collect, analyse and present data regarding the paediatric influenza burden in European countries, with the purpose of providing the necessary information to make evidence-based decisions regarding influenza immunisation recommendations for children. The initial approach taken is based on existing weekly virological and age-specific influenza-like illness (ILI) data from surveillance networks across Europe. We use a multiple regression model guided by longitudinal weekly patterns of influenza virus to attribute the weekly ILI consultation incidence pattern to each influenza (sub)type, while controlling for the effect of respiratory syncytial virus (RSV) epidemics. Modelling the ILI consultation incidence during 2002/2003–2008 revealed that influenza infections that presented for medical attention as ILI affected between 0.3% and 9.8% of children aged 0–4 and 5–14 years in England, Italy, The Netherlands and Spain in an average season. With the exception of Spain, these rates were always higher in children aged 0–4 years. Across the six seasons analysed (five seasons were analysed from the Italian data), the model attributed 47–83% of the ILI burden in primary care to influenza virus infection in the various countries, with the A(H3N2) virus playing the most important role, followed by influenza viruses B and A(H1N1). National season averages from the four countries studied indicated that between 0.4% and 18% of children consulted a physician for ILI, with the percentage depending on the country and health care system. Influenza virus infections explained the majority of paediatric ILI consultations in all countries. The next step will be to apply the EPIA modelling approach to severe outcomes indicators (i.e. hospitalisations and mortality data) to generate a complete range of mild and severe influenza burden estimates needed for decision making concerning paediatric influenza vaccination.

Effects of respiratory syncytial virus upon expressions of mRNA and protein of intercellular adhesion molecule-1 in human embryonic lung fibroblast cells

To explore the effects of respiratory syncytial virus (RSV) upon the expressions of mRNA and protein of intercellular adhesion molecule-1 (ICAM-1) in human embryonic lung fibroblast cells. The expressions of mRNA and protein of ICAM-1 were determined in human embryonic lung fibroblast cells after being infected by the LONG strain type A RSV and in normal fibroblast cells with real-time PCR and flow cytometry. The mRNA of ICAM-1 expression in human embryonic lung fibroblast cells was 2.51 times at 24 h post-infection as that in normal fibroblast cells (P < 0.05). The protein of ICAM-1 expression of RSV control group (1.25 +/- 0.09, 1.87 +/- 0.18, 4.78 +/- 0.52, 13.34 +/- 0.64, 1.58 +/- 0.37) were significantly higher than those of normal cell group (0.21 +/- 0.06, 0.30 +/- 0.06, 0.29 +/- 0.07, 0.35 +/- 0.17, 0.35 +/- 0.14) at 12, 24, 48, 72 and 96 h post-infection (all P < 0.01). The protein of ICAM-1 expression of RSV control group achieved a peak value between 48 h and 72 h, and then it decreased significantly at 96 h. Lung fibroblast cell and ICAM-1 may play some roles in pathogenic mechanism of RSV viral pneumonia.

Effects of Respiratory Syncytial Virus Infection on Dendritic Cells and Cysteinyl Leukotrienes in Lung Tissues of a Murine Model of Asthma

Pulmonary dendritic cells (DCs) play critical roles in both allergy and in viral infection. Levels of cysteinyl leukotrienes (cysLTs) increase after allergen sensitization and viral infection and can modulate the migration and functions of DCs. The present study examines the effects of respiratory syncytial virus (RSV) infection on numbers of DCs and cysLT concentrations in lung tissues of mice sensitized with mite allergen. We examined Control, Dermatophagoides farinae allergen sensitized (Df), RSV infected (RSV) and Df allergen sensitized and RSV infected (Df-RSV) Balb/c mice. We then determined the number of CD11c-positive DCs and the LT concentration in lung tissues of the mice and examined lung pathology and cytokine profiles in thoracic lymph nodes. Infection with RSV significantly enhanced allergic airway inflammation in Df mice with concomitant increases in Th1 and Th2 immunity. The number of DCs and the cysLT concentrations were significantly increased in the lungs of Df and RSV mice and more so in Df-RSV, than in Df mice. The present findings suggest that RSV infection increases the number of DCs and the cysLT concentrations in lung tissues of asthma patients, both of which could result in enhanced allergic airway inflammation.

Effect of respiratory syncytial virus on the activity of matrix metalloproteinase in mice

Respiratory syncytial virus (RSV) is a common pathogen in the lower respiratory tract of infants and children. Recent studies have shown that in adults, especially in the elderly population who have relatively weak immunity, lower respiratory tract infection is not uncommon. RSV was detected in 22% hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease (COPD), and the detection rate was only next to that of parvovirus and influenza virus respectively. Further studies revealed that lung infection of RSV could lead to inflammatory destruction and structural remodeling. This study was undertaken to examine the effect of infection with RSV on matrix metalloproteinase (MMPs) in mice, and to explore the role of RSV in the pathogenesis of pulmonary diseases. Twenty BALB/c mice were divided randomly into an RSV infection group and a blank control group. The mice in the RSV infection group were given 100 microl liquid containing 10(6) PFU of RSV by intranasal instillation. Three days after the infection, the bronchoalveolar lavage fluid (BALF) was harvested and RT-PCR and Western blotting were used to detect MMP-9 and the expression of tissue inhibitors of matrix metalloproteinase (TIMP)-1 mRNA in lung tissues. Gelatin zymography was employed to detect the activities of MMP-9 and MMP-2 in BALF. Immunohistochemistry was used to determine the expressions of E-cadherin (E-cd) and proliferating cell nuclear antigen (PCNA) in the lung tissues. In the BALF of the mice infected with RSV, the activities of MMP-9 and MMP-2 were significantly increased (t = 6.08, P < 0.01 and t = 5.68, P < 0.01). The levels of mRNA and proteins of MMP-9 in the lung tissues of the mice infected with RSV were significantly elevated, and the mRNA and protein levels were significantly higher than those of the blank controls. Though the ratio of MMP-9/TIMP-1 mRNA in the lung tissues of the infected mice was not significantly different from that of the normal controls, the ratio of the MMP-9/TIMP-1 protein in the RSV infection group was significantly higher than that in the control group. Moreover, the number of cells with positive E-cd expression was decreased and the number of cells positive for PCNA was increased, with an enhanced expression. In mice, infection with RSV can significantly increase the activities of MMP-9 and MMP-2, and conspicuously elevate the mRNA transcription of MMP-9. RSV infection can increase the activity of gelatinase while up-regulating its inhibitory factors but increase its protein ratio of MMP-9/TIMP-1 in lung tissues, thereby facilitating fibrosis after structural destruction of the airway. The resultant status might be an important factor causing chronic reconstruction of the airway.

Effect of Respiratory Syncytial Virus on Apnea in Weanling Rats

Apnea is a common complication of respiratory syncytial virus (RSV) infection in young infants. The purpose of this study was to determine whether this infection affects apnea triggered by sensorineural stimulation in weanling rats. We also studied which neurotransmitters are involved in this response and whether passive prophylaxis with a specific neutralizing antibody (palivizumab) confers protection against it. Weanling rats were inoculated intranasally with RSV, adenovirus, or virus-free medium. Changes in respiratory rate and apnea in response to nerve stimulation with increasing doses of capsaicin were measured by plethysmography. Capsaicin-induced apnea was significantly longer in RSV-infected rats at postinoculation days 2 (upper airways infection) and 5 (lower airways infection), and apnea-related mortality occurred only in the RSV-infected group. Reduction in the duration of apnea was observed after selective inhibition of central gamma-aminobutyric acid (GABA) type A receptors and neurokinin type 1 receptors for substance P. Prophylactic palivizumab protected against apnea and apnea-related mortality. These results suggest that sensorineural stimulation during RSV infection is associated with the development of apnea and apnea-related death in early life, whose mechanism involves the release of GABA acting on central GABA type A receptors and substance P acting on neurokinin type 1 receptors.

Respiratory virus infections in cystic fibrosis.

Respiratory virus infections have pronounced and long-lasting effects on patients with cystic fibrosis (CF), resulting in significant declines in FVC, FEV(1) and Shwachman score, significantly increasing both the frequency and duration of hospitalisation. Deleterious effects on patients with CF have been reported for most viruses studied but the effects of respiratory syncytial virus and influenza appear the greatest. There is circumstantial evidence that respiratory virus infections may facilitate bacterial infections, particularly Pseudomonas aeruginosa.

The failure of interleukin-10-deficient mice to develop airway hyperresponsiveness is overcome by respiratory syncytial virus infection in allergen-sensitized/challenged mice.

Interleukin-10-deficient mice develop a robust pulmonary inflammatory response but no airway hyperresponsiveness (AHR) to inhaled methacholine (MCh) following allergen sensitization and challenge. In the present study, we investigated the effect of respiratory syncytial virus (RSV) infection on AHR and pulmonary inflammation in allergic IL-10-/- mice. Unlike littermate control mice, RSV-infected or ovalbumin (OVA)-sensitized/challenged IL-10-/- mice failed to develop significant AHR. In contrast, sensitized/challenged IL-10-/- mice infected with RSV did develop AHR accompanied by increased eosinophil numbers, both in bronchoalveolar lavage (BAL) and pulmonary tissue, and mucin production in airway epithelium. The cytokine profile in OVA-sensitized/challenged IL-10-/- mice was skewed toward a Th1 response but after RSV infection, this response was more of a Th2 type, with increased IL-5 levels in the BAL. Studies with an RSV mutant that lacks the G and SH genes showed equal enhancement of the AHR response as the parental wild-type strain, indicating that G protein is not essential to this response. These data suggest that RSV infection can overcome the failure of development of AHR in allergic IL-10-/- mice.

Induction and regulation of nitric oxide synthase in airway epithelial cells by respiratory syncytial virus.

In this study, we evaluated the effects of respiratory syncytial virus (RSV) infection on nitric oxide (NO) production in human airway epithelial cells. In addition, we evaluated whether T-helper type 1 (Th1)- and Th2-type cytokines modulate the release of NO in response to RSV infection. To do this, we infected monolayers of A549 cells with RSV and determined nitrite levels in the supernatant fluids. We also measured nitrite levels in human small-airway epithelial cells (SAEC) in primary culture and in the bronchoalveolar lavage fluid (BALF) obtained from Balb/c mice after RSV infection. To further support our observations in these analyses, we performed immunocytochemistry and Western blot analysis for inducible nitric oxide synthase (iNOS) in A549 cells. To evaluate the regulation of NO production in response to RSV, we performed experiments in the absence and presence of the Th1 and Th2 type cytokines: interferon (IFN)-gamma, interleukin (IL)-4, and IL-13. In addition, we assessed the inhibitory effect of dexamethasone on iNOS in RSV infected A549 cells. Results were expressed in terms of nmol/mg protein and shown as percents of control values (mean +/- SE). RSV increased the release of nitrites in A549 cells, SAEC, and BALF. The increase in nitrite levels was supported by immunocytochemistry and Western blot analysis for iNOS protein in A549 cells, indicating activation of iNOS in response to RSV infection. IFN-gamma and IL-13 did not affect the RSV-induced increase in NO production. By contrast, IL-4 and dexamethasone suppressed the release of NO in response to RSV infection. These observations show that RSV infection leads to activation of iNOS within the airway epithelium and that IL-4 and dexamethasone inhibit the production of NO in response to RSV infection.