Prevalence of respiratory syncytial virus infection among hospitalized children presenting with acute lower respiratory tract infections

Reclassification of respiratory syncytial virus genotypes in India

Respiratory syncytial virus (RSV) is known to be the major cause of lower respiratory tract infections in infants and in the elderly. RSV was recently reclassified and simplified into three genotypes of the RSV-A subgroup (GA1-GA3) and into seven genotypes of the RSV-B subgroup (GB1-GB7). This classification strategy was not implemented globally. This study intended to reclassify the sequences that were submitted in GenBank till September 2021 from India. The gene sequences of the ectodomain region, second hypervariable region (SHR), and the partial second hypervariable region (PSHR) of the G gene were selected for the analysis. 25 ectodomain, 36 s hypervariable, and 19 partial second hypervariable regions of the RSV-A subgroup and 42-ectodomain, 49-s hypervariable region and 11-partial second hypervariable region of RSV-B subgroup were used for phylogenetic analysis. P-distance was calculated to support the genotype determination done by phylogenetic analysis. Phylogenetic analysis revealed that GA2.3.1, GA2.3.3, GA2.3.4, GA2.3.5, and GA2.3.6b lineages of GA2 genotype for RSV-A; and GB5.0.1, GB5.0.2, GB5.0.3, GB5.0.4a, GB5.0.4c, GB5.0.5a, GB5.0.5c lineages of GB5 genotype and GB7 genotype for RSV-B were that circulated in India. This work has implication for RSV vaccine research, and also for strategies for the prevention and control of RSV infection in humans.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-022-00802-x.

Respiratory syncytial virus among children hospitalized with severe acute respiratory infection in Kashmir, a temperate region in northern India

Background

Severe acute respiratory infections (SARI) are a leading cause of hospitalizations in children, especially due to viral pathogens. We studied the prevalence of respiratory viruses among children aged <5 years hospitalized with severe acute respiratory infections (SARI) in Kashmir, India.

Methods

We conducted a prospective observational study in two tertiary care hospitals from October 2013 to September 2014, systematically enrolling two children aged <5 years with SARI per day. We defined SARI as history of fever or measured fever (≥38°C) and cough with onset in the last 7 days requiring hospitalization for children aged 3-59 months and as physician-diagnosed acute lower respiratory infection for children aged <3 months. Trained study staff screened children within 24 hours of hospitalization for SARI and collected clinical data and nasopharyngeal swabs from enrolled participants. We tested for respiratory syncytial virus (RSV) A and B, influenza viruses, rhinoviruses (HRV)/enteroviruses, adenovirus (AdV), bocavirus (BoV), human metapneumovirus (hMPV) A and B, coronaviruses (OC43, NL65, C229E), and parainfluenza viruses (PIV) 1, 2, 3 and 4 using standardized duplex real-time polymerase chain reaction.

Results

Among 4548 respiratory illness admissions screened from October 2013 to September 2014, 1026 met the SARI case definition, and 412 were enrolled (ages = 5 days to 58 months; median = 12 months). Among enrolees, 256 (62%) were positive for any virus; RSV was the most commonly detected (n = 118, 29%) followed by HRV/enteroviruses (n = 88, 21%), PIVs (n = 31, 8%), influenza viruses (n = 18, 4%), BoV (n = 15, 4%), coronaviruses (n = 16, 4%), AdV (n = 14, 3%), and hMPV (n = 9, 2%). Fifty-four children had evidence of virus co-detection. Influenza-associated SARI was more common among children aged 1-5 years (14/18, 78%) while most RSV detections occurred in children <12 months (83/118, 70%). Of the RSV viruses typed (n = 116), the majority were type B (94, 80%). Phylogenetic analysis of G gene of RSV showed circulation of the BA9 genotype with 60bp nucleotide duplication.

Conclusions

Respiratory viruses, especially RSV, contributed to a substantial proportion of SARI hospitalizations among children <5 years in north India. These data can help guide clinicians on appropriate treatment and prevention strategies.

Nebulized Magnesium Sulphate in Bronchiolitis: A Randomized Controlled Trial

OBJECTIVE

To evaluate the efficacy and safety of nebulized magnesium sulphate as a bronchodilator in young children aged 1-24 mo with moderate to severe bronchiolitis in comparison to standard therapy.

METHODS

This was an open labeled randomized controlled trial comprising 60 children with moderate to severe bronchiolitis which was randomly assigned to 2 groups. Intervention group received nebulization with 3 mL of 3.2% magnesium sulphate (MgSO₄) (iso-osmolar) every 4 hourly for 24 h in addition to standard care and the control group received standard care alone. The primary outcome measure was to compare the improvement of bronchiolitis severity score (BSS) and length of hospitalization. The secondary outcome was to measure the need for noninvasive ventilation, need for admission to intensive care unit (ICU) in the initial visit, to evaluate the safety of magnesium sulphate and need for clinic revisit, hospital readmission and ICU readmission within 2 wk after discharge in both the groups.

RESULTS

The mean age of children allocated in the control group was 7.4 ± 5.1 mo and 7.7 ± 4.5 mo in the intervention group. There was no significant difference with respect to improvement of BSS or reduced length of hospitalization in both the groups (p > 0.05). BSS monitored sequentially after enrollment at 1, 2, 4, 8, 12, 16, and 24 h did not show statistically significant differences between the groups. Mean length of hospital stay was 2.89 ± 2.25 d in treatment group and 2.96 ± 1.86 d in control group (p = 0.902). No adverse events were observed in both the groups.

CONCLUSION

Nebulized magnesium sulphate is not superior to standard therapy in children with moderate to severe bronchiolitis.

CLINICAL TRIAL REGISTRATION NUMBER

CTRI/2018/06/014400.

Disease Burden Due to Respiratory Syncytial Virus in Indian Pediatric Population: A Literature Review

Respiratory syncytial virus (RSV) is one of the leading causes of lower respiratory tract infections in young children. Globally, there is huge disease burden, high treatment cost, and health impact beyond acute episodes due to RSV which necessitate development and implementation of preventive strategies for the control of RSV infection. The disease burden due to RSV in pediatric population across India is still not clearly understood so this literature review was therefore conducted to gather data on disease burden due to RSV in Indian pediatric population. Systematic literature search was performed using PubMed and Google search with different medical subject headings from 2007 to 2020. Studies performed in Indian pediatric population were selected for review. Literature review revealed that in India, epidemiology of RSV infection is well documented in young children (0-5 years) as compared to children from other age groups. The rates of RSV detection in various studies conducted in younger children (0-5 years) vary from 2.1% to 62.4% in India which is higher as compared to children from other age groups. In India, RSV mainly peaks around rainy to early winter season, that is, during months of June through October while smaller peak was noted during December, January, and February. In 2020, higher RSV-associated disease burden was reported among children (<5 years) in low-income and lower-middle-income countries. Considering significant disease burden due to RSV in young Indian children, availability of RSV vaccine would be crucial to prevent RSV infections in children and its spread in the community.

Acute Viral Bronchiolitis: A Narrative Review

Acute viral bronchiolitis (AVB) is the leading cause of hospital admissions among infants in developed and developing countries and associated with increased morbidity and cost of treatment. This review was performed to guide the clinicians managing AVB in light of evidence accumulated in the last decade. We searched published English literature in last decade regarding etiology, diagnosis, treatment, and prevention of AVB using PubMed and Cochrane Database of Systematic Reviews. Respiratory syncytial virus is the most common causative agent. The diagnosis is mainly clinical with limited role of diagnostic investigations and chest radiographs are not routinely indicated. The management of AVB remains a challenge, as the role of various interventions is not clear. Supportive care in from of provision of heated and humidified oxygen and maintaining hydration are main interventions. The use of pulse oximetry helps to guide the administration of oxygen. Trials and systematic reviews evaluated various interventions like nebulized adrenaline, bronchodilators and hypertonic saline, corticosteroids, different modes of noninvasive ventilation (high-flow nasal cannula [HFNC], continuous positive airway pressure [CPAP], and noninvasive positive pressure ventilation [NPPV]), surfactant, heliox, chest physiotherapy, and antiviral drugs. The interventions which showed some benefits in infants and children with AVB are adrenaline and hypertonic saline nebulization, HFNC, CPAP, NIV, and surfactant. The routine administration of antibiotics, bronchodilators, corticosteroids, steam inhalation, chest physiotherapy, heliox, and antiviral drugs are not recommended.

Respiratory syncytial virus infections in India: Epidemiology and need for vaccine

Respiratory syncytial virus (RSV) has been identified as a leading cause of lower respiratory tract infections in young children and elderly. It is an enveloped negative-sense RNA virus belonging to Genus Orthopneumovirus. The clinical features of RSV infection range from mild upper-respiratory-tract illnesses or otitis media to severe lower-respiratory-tract illnesses. Current estimates show that about 33.1 million episodes of RSV-acute lower respiratory infection (ALRI) occurred in young children in 2015, of these majority that is, about 30 million RSV-ALRI episodes occurred in low-middle-income countries. In India, the rates of RSV detection in various hospital- and community-based studies mostly done in children vary from 5% to 54% and from 8% to 15%, respectively. Globally, RSV epidemics start in the South moving to the North. In India, RSV mainly peaks in winter in North India and some correlation with low temperature has been observed. Different genotypes of Group A (GA2, GA5, NA1 and ON1) and Group B (GB2, SAB4 and BA) have been described from India. The burden of RSV globally has kept it a high priority for vaccine development. After nearly 50 years of attempts, there is still no licensed vaccine and challenges to obtain a safe and effective vaccine is still facing the scientific community. The data in this review have been extracted from PubMed using the keywords RSV and Epidemiology and India. The data have been synthesised by the authors.

Prevalence of respiratory syncytial virus infection among children hospitalized with acute lower respiratory tract infections in Southern India

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory infections among children.

AIM

To investigate the proportion of RSV and non-RSV respiratory viral infections among hospitalized children ≤ 5 years.

METHODS

Hospitalized children aged < 5 years, with a diagnosis of acute lower respiratory infections (ALRI), admitted between August 2011-August 2013, were included. Cases were defined as laboratory-confirmed RSV and non-RSV respiratory viruses by direct fluorescence assay from the nasopharyngeal wash.

RESULTS

Of 383 1-59 mo old children hospitalized with an acute lower respiratory infection, 33.9% (130/383) had evidence of viral infection, and RSV was detected in 24.5% (94/383). Co-infections with RSV and other respiratory viruses (influenza A or B, adenovirus, para influenza 1, 2 or 3) were seen in children 5.5% (21/383). Over 90% of the RSV-positive children were under 2 years of age. RSV was detected throughout the year with peaks seen after the monsoon season. Children hospitalized with RSV infection were more likely to have been exposed to a shorter duration of breastfeeding of less than 3 mo. RSV positive children had a shorter hospital stay, although there were significant complications requiring intensive care. Use of antibiotics was high among those with RSV and non-RSV viral infections.

CONCLUSION

Our study provides evidence of a high proportion of RSV and other virus-associated ALRI among hospitalized children in India. RSV infection was associated with fewer days of hospital stay compared to other causes of lower respiratory infections. A high level of antibiotic use was seen among all respiratory virus-associated hospitalizations. These results suggest the need for implementing routine diagnostics for respiratory pathogens in order to minimize the use of unnecessary antibiotics and plan prevention strategies among pediatric populations.

Rapid detection of respiratory syncytial virus in community-acquired lower respiratory tract infections in children by chromatographic assay

Respiratory syncytial virus (RSV) is the single most important viral agent causing pediatric lower respiratory tract infections (LRTIs) worldwide. To evaluate the role of RSV in pediatric LRTIs, we studied 85 children <2 years of age hospitalized for community-acquired LRTIs. Nasopharyngeal aspirates were obtained on admission for the detection of RSV antigen by immunochromatographic assay. Demographic, clinical, and radiological findings for RSV antigen were compared. Data analysis was performed by Chi-square test. A relatively higher number of RSV-infected children 32 (60.4%) were below 6 months of age. Clinical and radiological findings in both RSV-positive and RSV-negative groups were comparable. RSV antigen was positive in 53 (62.4%) with immunochromatography. Our study confirms that RSV plays a significant role in community-acquired LRTIs in children.

Global distribution of NA1 genotype of respiratory syncytial virus and its evolutionary dynamics assessed from the past 11 years

Respiratory syncytial virus (RSV) is a potent pathogen having global distribution. The main purpose of this study was to gain an insight into distribution pattern of the NA1 genotype of group A RSV across the globe together with its evolutionary dynamics. We focused on the second hypervariable region of the G protein gene and used the same for Phylogenetic, Bayesian and Network analyses. Eighteen percent of the samples collected from 500 symptomatic pediatric patients with acute respiratory tract infection (ARI) were found to be positive for RSV during 2011-15 from New Delhi, India. Of these, group B RSV was predominant and clustered into two different genotypes (BA and SAB4). Similarly, group A viruses clustered into two genotypes (NA1 and ON1). The data set from the group A viruses included 543 sequences from 23 different countries including 67 strains from India. The local evolutionary dynamics suggested consistent virus population of NA1 genotype in India during 2009 to 2014. The molecular clock analysis suggested that most recent common ancestor of group A and NA1 genotype have emerged in during the years 1953 and 2000, respectively. The global evolutionary rates of group A viruses and NA1 genotype were estimated to be 3.49 × 10^-3 (95% HPD, 2.90-4.17 × 10^-3) and 3.56 × 10^-3 (95% HPD, 2.91 × 10^-3-4.18 × 10^-3) substitution/site/year, respectively. Analysis of the NA1 genotype of group A RSV reported during 11 years i.e. from 2004 to 2014 showed its dominance in 21 different countries across the globe reflecting its evolutionary dynamics. The Network analysis showed highly intricate but an inconsistent pattern of haplotypes of NA1 genotype circulating in the world. Present study seems to be first comprehensive attempt on global distribution and evolution of NA1 genotype augmenting the optimism towards the vaccine development.

Genetic characterization respiratory syncytial virus in Kerala, the southern part of India

Respiratory syncytial virus (RSV) is an important cause of acute lower respiratory tract infection (ALRI) in infants and young children globally. RSV presents two antigenic groups RSV-A and -B. Genetic variability is also very high within each group. RSV circulation varies year to year and even varies among different regions. Data on circulatory pattern of RSV are available from other parts of India except Kerala. The aim of the study was to generate data about groups and genotypes of circulating RSV in Kerala. In this study, RSV positive samples received during January, 2012 to December, 2014 were used for genetic characterization. The samples were tested by using nucleocapsid (N) gene-based conventional multiplex reverse transcriptase polymerase chain reaction (RT-PCR) to identify the RSV group. Genotyping was done by nucleotide sequencing of the C-terminal region of the glycoprotein (G) gene. Out of the 130 patient samples tested, 49 samples were positive for RSV. Among the positive samples, 32 belong to the RSV-A and 17 belong to RSV-B virus. Phylogenetic analysis revealed that all RSV-A sequences (n = 22) belonged to NA1 genotype and five of the sequences showed the novel 72 nucleotide duplication and clustered into the newly designated ON1 genotype. All RSV-B sequences (n = 17) were clustered into the BA (BA9 and 10) genotype. From this study, we concluded both RSV-A and -B were co-circulated in Kerala and RSV-A was observed predominantly in 2012 and RSV-B in 2014. As per our best of knowledge, BA10 genotype is first observed in India.

Natural helper cells mediate respiratory syncytial virus-induced airway inflammation by producing type 2 cytokines in an IL-33-dependent manner

AIM

Type 2 cytokine production during respiratory virus infection is considered to be linked with asthma exacerbation. As potent Th2 cytokine producers, natural helper (NH) cells play a key role in influenza virus-induced airway hyper-responsiveness. However, it is unclear whether NH cells contribute to respiratory syncytial virus (RSV)-induced airway inflammation, and how the cytokine profile in NH cells is changed during RSV infection.

METHODS

BALB/c mice were infected intranasally with RSV. The number of NH cells in lungs was detected by flow cytometry. The expression of cytokine mRNAs was performed by real-time RT-PCR. Cytokines levels were determined by ELISA.

RESULTS

Following intranasal infection with RSV, BALB/c mice showed an increase in the expression of mRNAs for Th2-like cytokines in NH cells. Furthermore, adoptive transfer of pulmonary NH cells resulted in a massive infiltration of mononuclear cells, in particular eosinophils and neutrophils in lungs, in parallel with an augmented production of Th2-associated cytokines, such as IL-4, IL-5 and IL-10 in bronchoalveolar lavage fluids, providing convincing evidence that NH cells contribute to RSV-induced lung pathogenesis by producing type 2 cytokines. It should be noted that blocking IL-33 with antibody can diminish the absolute number of pulmonary NH cells and the relative expression of mRNAs for type 2 cytokines in pulmonary NH cells, suggesting that IL-33 is necessary for activating Th2-type NH cells.

CONCLUSION

These results reveal that pulmonary NH cells might participate in RSV-induced airway inflammation by producing large quality of type 2 cytokines in an IL-33-dependent manner.

Clinical characterization of influenza A and human respiratory syncytial virus among patients with influenza like illness

Influenza A and Respiratory Syncytial Virus (RSV) has been recognized as a major cause of acute respiratory tract infection. H1N1 is one of the subtypes of influenza A, pandemic worldwide in July 2009, causing 18,449 deaths globally. To investigate the prevalence and clinical manifestation of the influenza A, H1N1pdm09, and RSV. Throat/nasal swab collected from the patients of all age group either outpatients/inpatients having respiratory illness from 2 to 5 days. The clinical data were recorded in a predesigned questionnaire. RNA was extracted and analyzed by real time PCR at a tertiary care center, 2009-2014. Total 4,352 samples tested for influenza A and H1N1. Out of 4,352, 32.2% (median positivity 21%; range 16-41% during 6 years) were positive for influenza A and 19% were H1N1 (median positivity 16.7%; range 8.7-23% during 6 years). Total 1653 samples were analyzed for RSV from 2011 to 2014, 12% were RSV positive (median positivity 11.35%; range 10-16.3% during 4 years). Pharyngitis, dyspnea were frequent symptoms in influenza A and H1N1 (P < 0.005) whereas bronchiolitis and pneumonia were commonly present in RSV (P < 0.005). The positivity of influenza A and H1N1 was higher in age-group 21-30, whereas RSV in infant and children. H1N1 and RSV were co-circulated and have common clinical symptoms particularly in lower age group. Therefore, laboratory confirmation is necessary for further disease prognosis. Age was an important risk factor that affects the positivity of influenza A, H1N1, and RSV. Different clinical manifestation of H1N1 and RSV will be helpful for early and accurate diagnosis. J. Med. Virol. 89:49-54, 2017. © 2016 Wiley Periodicals, Inc.

Naso-pharyngeal Carriage of Organisms in Children Aged 3-59 months Diagnosed with Severe Community-acquired Pneumonia

OBJECTIVE

To study the naso-pharyngeal carriage of organisms in children diagnosed with severe pneumonia.

METHODS

Nasopharyngeal aspirate and swabs for microbiological analyses were collected from 377 children aged 3-59 months with severe pneumonia.

RESULTS

28.6% of the samples were positive for S. pneumoniae, 9.6% were positive for H. influenzae, and 8.5% were positive for both the organisms. Respiratory syncytial virus was detected in 27% of samples. The rate of isolation of S. pneumonia and H. influenzae was significantly more in the age group of 12-59 months.

CONCLUSION

In children with severe pneumonia, most common organisms isolated/detected from naso-pharyngeal aspirates were S.pneumoniae and Respiratory Syncytial Virus.

Nebulized Magnesium Sulfate in Acute Bronchiolitis: A Randomized Controlled Trial

OBJECTIVE

To assess the efficacy of nebulized magnesium sulfate as a bronchodilator in infants hospitalized with acute bronchiolitis.

METHODS

This three-center double masked randomized clinical trial comprised 120 children with moderate to severe bronchiolitis. They were randomly assigned into two groups: the first group was treated with nebulized magnesium sulfate (40 mg/kg) and nebulized epinephrine (0.1 ml/kg) and the second group (control) was treated with nebulized epinephrine (0.1 ml/kg). The primary outcome was the length of hospital stay. The use of oxygen, temperature, oxygen saturation (SPO2), pulse rate (PR), respiratory rate (RR) and respiratory distress assessment instrument (RDAI) score were measured in the beginning of the study and during hospitalization.

RESULTS

The mean (SD) age of 120 infants was 5.1(± 2.6) mo and 60% were boys. The length of hospital stay was not different between the two groups (P > 0.01). Use of oxygen supplementation, SPO2 and vital signs were similar in the two groups. Improvement in RDAI score was significantly better in infants treated with nebulized magnesium sulfate than in the other group (P 0.01).

CONCLUSIONS

Thus, in infants with acute bronchiolitis, the effect of nebulized magnesium sulfate is comparable to nebulized epinephrine. However nebulized magnesium sulfate can improve the clinical score so it may have additive effect to reduce symptoms during hospitalization.

IL-33 Receptor (ST2) Signalling is Important for Regulation of Th2-Mediated Airway Inflammation in a Murine Model of Acute Respiratory Syncytial Virus Infection

T1/ST2, an orphan receptor with homology with the interleukin (IL)-1 receptor family, is the ligand-binding component of the receptor for the cytokine IL-33, a newly identified cytokine known to amplify the Th2 cell-dominant immune responses. The function of IL-33/ST2 signalling during respiratory syncytial virus (RSV) infection is not fully known. In this study, following intranasal infection with RSV, BALB/c mice showed a marked increase in the production of IL-33, with an elevated expression of ST2 mRNA as well as a massive infiltration of CD45(+) ST2(+) cells in the lungs, suggesting that during the early phase of RSV infection, IL-33 target cells which express ST2 on cell surface, may play a critical role for the development of RSV-induced airway inflammation. Indeed, blocking ST2 signalling using anti-ST2 monoclonal antibody diminished not only RSV-induced eosinophil recruitment, but also the amounts of Th2-associated cytokines, particularly IL-13, and Th17-type cytokine IL-17A in the lungs of infected mice. However, anti-ST2 antibody treatment did not affect the production of Th1-type cytokine IFN-γ as well as pulmonary viral growth and clearance. These results indicate that IL-33/ST2 signalling is involved in RSV-induced, Th2-associated airway inflammation but not protective immunity.

Recent advances in management of bronchiolitis

Background

Bronchiolitis is one of the major causes for hospital admissions in infants. Managing bronchiolitis, both in the outpatient and inpatient setting remains a challenge to the treating pediatrician. The effectiveness of various interventions used for infants with bronchiolitis remains unclear.

Need and purpose

To evaluate the evidence supporting the use of currently available treatment and preventive strategies for infants with bronchiolitis and to provide practical guidelines to the practitioners managing children with bronchiolitis.

Methods

A search of articles published on bronchiolitis was performed using PubMed. The areas of focus were diagnosis, treatment and prevention of bronchiolitis in children. Relevant information was extracted from English language studies published over the last 20 years. In addition, the Cochrane Database of Systematic Reviews was searched.

Results and Conclusions

Supportive care, comprising of taking care of oxygenation and hydration, remains the corner-stone of therapy in bronchiolitis. Pulse oximetry helps in guiding the need for oxygen administration. Several recent evidence-based reviews have suggested that bronchodilators or corticosteroids lack efficacy in bronchiolitis and should not be routinely used. A number of other novel therapies (such as nebulized hypertonic saline, heliox, CPAP, montelukast, surfactant, and inhaled furosemide) have been evaluated in clinical trials, and although most of them did not show any beneficial results, some like hypertonic saline, surfactant, CPAP have shown promising results.

Infection with respiratory syncytial virus influences FasL-mediated apoptosis of pulmonary γδ T cells in a murine model of allergen sensitization

BACKGROUND

It has been reported that adoptive transfer of γδ T cells increases the cellular infiltration, especially eosinophils, in the lungs of allergic mice, suggesting that γδ T cells may play a proinflammatory role in allergic airway inflammation. Respiratory syncytial virus (RSV) infection can decrease the number of Th2-type γδ T cells. However, the underlying mechanisms remain unknown.

METHODS

BALB/c mice were inoculated intranasally with RSV before or after sensitization to OVA. The amounts of Th1/Th2 cytokines as well as the levels of specific antibodies were determined by ELISA. The apoptotic death of pulmonary γδ T cells was analyzed by flow cytometry.

RESULTS

Adoptive transfer of γδ T cells increased the production of Th2 cytokines in the lungs and allergy-related antibodies in the serum, further confirming that γδ T cells act as pro-inflammatory cells or a promoter for the development of allergic asthma. RSV infection before sensitization to OVA enhanced apoptotic death of pulmonary γδ T cells. The percentage and absolute number of FasL-expressing γδ T cells in the lungs of allergic mice were elicited significantly by prior RSV infection. Blocking FasL with monoclonal antibody diminished apoptotic death of γδ T cells, suggesting that FasL is important for RSV-induced apoptosis of pulmonary γδ T cells.

CONCLUSIONS

This work provides evidence that RSV infection suppresses the subsequent development of OVA-induced allergic responses partly by enhancing FasL-mediated apoptosis of pulmonary γδ T cells.

Respiratory syncytial virus protects against the subsequent development of ovalbumin-induced allergic responses by inhibiting Th2-type γδ T cells

Respiratory syncytial virus (RSV) infection has been hypothesized to be a risk factor for the development of allergy and asthma, but epidemiologic studies in humans still remain inconclusive. The association between RSV infection and allergic diseases may be dependent on an atopic background and previous history of RSV infection. It has been reported that RSV infection before sensitization to an allergen decreased the production of Th2-like cytokines in the lung and the levels of allergen-specific Th2-type antibodies in the serum. However, the underlying mechanisms are largely unknown. In the present study, the role of pulmonary γδ T cells in RSV-affected, allergen-induced airway inflammation was investigated. BALB/c mice were sensitized to or challenged with ovalbumin (OVA) and infected with RSV either before or after the sensitization period. It became clear that sensitization and challenge of mice with OVA induced a large influx of γδ T cells to the lungs. However, prior RSV infection inhibited the infiltration of γδ T cells as well as activated γδ T cells, characterized by expression of CD40L or CD69 molecular in the cell surface. Moreover, prior RSV infection elevated the type 1 cytokine gene expression but suppressed type 2 cytokine expression in the lung γδ T cells. Adoptive transfer of γδ T cells from OVA-sensitized and challenged mice increased airway inflammation, suggesting that γδ T cells may play a proinflammatory role in allergic responses. These results described here support the idea of an unknown γδ T cell-dependent mechanism in the regulation of RSV-affected, allergen-induced allergic airway responses.

Frequency of common viruses in etiology of acute respiratory tract infections

OBJECTIVE

To determine the frequency rate of C. pneumoniae, rhinovirus, respiratory syncytial virus (RSV), influenza virus, metapneumovirus, adenovirus', parainfluenza virus and coronavirus in acute respiratory tract infections in children.

METHODS

One hundred nine pediatric patients having respiratory tract infections were included in this study. Real time PCR, DFA and cell culture method were used for detection of C. pneumoniae, RSV antigen and influenza virus respectively. Multiplex PCR was used for detection of other viruses.

RESULTS

No C. pneumoniae DNA was detected in the samples. Virus was detected in 43 cases from larynx swabs (43/109, 39.4 %). The frequency order of the viral agents detected were as follows; rhinoviruses 14.7 %, RSV B 7.3 %, influenza A 6.4 %, metapneumovirus 3.6 %, adenovirus 3.6 %, coronavirus 0.9 %, parainfluenzavirus type 3, 0.9 %, parainfluenzavirus type 4, 0.9 % and RSV A 0.9 %. Sensitivity of the PCR and DFA methods for the diagnosis of RSV infections were detected as 100 % and 100 %, respectively. Specificity of the PCR and DFA methods for RSV infections were detected as 97 % and 100 % respectively. Sensitivity of the PCR and cell culture methods for influenzavirus infections were detected as 100 % and 100 %, respectively. Specificity of the PCR and DFA methods for RSV infections were detected as 96 % and 100 % respectively.

CONCLUSIONS

Prevalence of viral agents was detected as 39.4 %. Influenza viruses and RSV were common. Metapneumovirus was also frequent (3.6 %). C. pneumoniae was not found to be a common agent for acute respiratory disease in children.