The role of respiratory syncytial virus in acute bronchiolitis in small children in northern Japan

Rapid Detection of Viruses Using Loop-Mediated Isothermal Amplification (LAMP): A Review

Most of the diseases caused by viral infection are found to be fatal, and the diagnosis is difficult due to confusion with other causative agents. So, a highly efficient molecular-based advance detection technique, i.e., loop-mediated isothermal amplification (LAMP) method, is developed for diagnosis of viral infections by various workers. It is based on amplification of DNA at very low level under isothermal conditions, using a set of four specifically designed primers and a DNA polymerase with strand displacement activity. This technique is found to be superior than most of the molecular techniques like PCR, RT-PCR, and real-time PCR due to its high specificity, sensitivity, and rapidity. Major advantage of LAMP method is its cost-effectiveness as it can be done simply by using water bath or dry bath. Here, in this review information regarding almost all the effective LAMP techniques which is developed so far for diagnosis of numerous viral pathogens is presented.

Mast cell degranulation is induced by A549 airway epithelial cell infected with respiratory syncytial virus

Respiratory syncytial virus (RSV), a major causative agent of respiratory tract infections, influences allergic diseases. Mast cells, important effector cells in allergic disease, also express chemokine (C-X(3)-C motif) receptor 1 (CX(3)CR1). The RSV attachment glycoprotein (G protein) is structurally similar to CX(3)C ligand 1 (CX(3)CL1), the CX(3)CR1 ligand, suggesting that RSV directly interacts with and affects mast cell function, including degranulation. In this paper, the effect of RSV infection on mast cell function was studied using the human mast cell line (HMC-1). The results showed that RSV infection and replication was inefficient in HMC-1 cells than in human epithelial A549 cells. Additionally, HMC-1 degranulation occurred only in coculture with RSV-infected A549 cells, with up-regulation of TNFalpha secretion. However, direct RSV inoculation and incubation with RSV-infected A549 cell culture medium failed to induce HMC-1 degranulation, suggesting that virus-infected cells are critical for degranulation during RSV infection; however, degranulation does not occur by direct RSV infection into mast cells.

Evidence of a causal role of winter virus infection during infancy in early childhood asthma

RATIONALE

Bronchiolitis during infancy is associated with an increased risk of childhood asthma. Whether winter viral infections cause asthma or are a manifestation of a predisposition to asthma development is unknown.

OBJECTIVES

To study the relationship of winter virus infection during infancy and the development of childhood asthma.

METHODS

We studied over 95,000 infants born between 1995 and 2000 and followed through 2005 who were enrolled in the Tennessee Medicaid program from birth through early childhood to determine whether infant birth in relationship to the winter virus peak alters the risk of developing early childhood asthma.

MEASUREMENTS AND MAIN RESULTS

Among 95,310 children studied during five winter virus seasons from birth through early childhood, the risk of developing asthma tracked with the timing of infant birth in relationship to the winter virus peak. Infant birth approximately 4 months before the winter virus peak carried the highest risk, with a 29% increase in odds of developing asthma compared with birth 12 months before the peak (adjusted odds ratio, 1.29; 95% confidence interval, 1.19-1.40). Infant age at the winter virus peak was comparable to or greater than other known risk factors for asthma.

CONCLUSIONS

Timing of birth in relationship to winter virus season confers a differential and definable risk of developing early childhood asthma, establishing winter virus seasonality as a causal factor in asthma development. Delay of exposure or prevention of winter viral infection during early infancy could prevent asthma.

Influenza A and respiratory syncytial virus hospital burden in young children in East London

Epidemiological studies have demonstrated high hospitalization rates attributable to influenza and RSV in children aged 6 months and those aged <12 months, respectively (43 and 92.5/10 000 person-months, respectively). In conclusion, these high paediatric RSV and influenza incidence rates can be used to inform UK policy on childhood influenza immunization and subsequent RSV immunization in the future.

Diagnosis of human respiratory syncytial virus infection using reverse transcription loop-mediated isothermal amplification

Human respiratory syncytial virus (RSV) is a major causative agent of lower respiratory tract infections in children and the elderly. A reverse transcription-loop-mediated isothermal amplification (RT-LAMP) was developed assay to amplify the genome of RSV subgroups A and B, in order to improve current diagnostic methods for RSV infection. The primer sets for RT-LAMP were designed using highly conserved nucleotide sequences in the matrix protein region of subgroups A and B, and were specific for each subgroup. The RT-LAMP efficiency was compared to virus isolation and a commercially available enzyme immunoassay (EIA) for RSV detection (BD Directigen EZ RSV test), using nasopharyngeal aspirates from 59 children with respiratory tract infections. The RT-LAMP was specific for RSV and could not detect other respiratory pathogens. 61% (36/59) of children were positive by RT-LAMP, 34% (20/59) by viral isolation, and 56% (26/46) by EZ RSV. Of 16 specimens that were negative by both antigen detection and virus isolation, 12.5% (2/16) were RT-LAMP positive. These results suggest that the RT-LAMP is more sensitive than other methods used to detect RSV. The RT-LAMP assay developed in this study may be useful for diagnostic and epidemiological studies of RSV infection.

Environmental and demographic risk factors for respiratory syncytial virus lower respiratory tract disease

OBJECTIVE

To critically review the literature examining risk factors for development of severe respiratory syncytial virus lower respiratory tract infection (RSV LRI).

STUDY DESIGN

A literature review was performed with the use of a MedLine search strategy. Clinical evidence of putative risk factors was rated by means of the US Preventive Services Task Force recommendations, and the quality of the data was critically assessed. Nonmedical risk factors examined included race/ethnicity, age of acquisition of RSV, sex, birth during the first half of the RSV season, breast-feeding, malnutrition, maternal education, socioeconomic status, crowding/siblings, day care, and tobacco smoke exposure.

RESULTS

There was sufficient evidence available to conclude that (1) male sex, (2) age <6 months, (3) birth during the first half of the RSV season, (4) crowding/siblings, and (5) day care exposure are significant risk factors for severe RSV LRI. There was insufficient evidence to evaluate the effect of race/ethnicity on severe RSV LRI. The evidence for tobacco smoke exposure is mixed. Low maternal education (as a proxy for lower socioeconomic status), lack of breast-feeding, and malnutrition did not appear to increase the risk of severe RSV LRI or RSV hospitalization.

CONCLUSIONS

Male sex, young age, birth in the first half of the RSV season, day care attendance, and crowding/siblings are independent risk factors for the development of severe RSV LRI.

Respiratory syncytial virus epidemics: the ups and downs of a seasonal virus

Respiratory syncytial virus (RSV) is the most common pathogen causing lower respiratory tract infections in infants worldwide. Lower respiratory tract infections caused by RSV occur epidemically, and the appearance of epidemics seems to vary with latitude, altitude and climate. This study uses a review of the literature on RSV seasonality to investigate whether a global pattern in RSV epidemics can be found. A comparison of morbidity and mortality caused by RSV in developed vs. developing countries is also presented. The seasons in which RSV epidemics occur typically depend on geographic location and altitude. During these seasons the epidemics tend to appear in clusters. Although the appearance pattern of these epidemics varies from one continent to another, they usually begin in coastal areas. RSV is the cause of one-fifth of lower respiratory infections worldwide. Generally RSV mortality is low, with a median value of zero. However, RSV mortality in developing countries is significantly higher than RSV mortality in developed countries.

Impact of severe disease caused by respiratory syncytial virus in children living in developed countries

Among industrialized nations, the rate of rehospitalization in the United States for respiratory syncytial virus (RSV) is approximately 30 per 1000, exceptions being noted for American Indians and Alaskan natives, two ethnic groups who tend toward higher rates of RSV hospitalization. In distinction Japan reports an admission rate of 60 per 1000 for RSV disease. Yet Japan ranks considerably lower than many of its western counterparts in premature births. Whether an RSV subtype, a new viral genotype or some other unifying characteristic exists that might explain the severity of adenovirus, parainfluenza and RSV infections in this region of Asia remains to be determined. Outcomes trials in the United States, Canada, United Kingdom, Denmark and Japan all identified crowding and exposure to tobacco smoke as significant and independent risk factors for disease severity of RSV. The epidemiology of RSV is largely consistent throughout Europe, with peak outbreaks occurring in December and January. In Europe RSV accounts for 42 to 45% of hospital admissions for lower respiratory tract infections in children younger than 2 years of age, and inpatient populations tend to be younger and to experience greater disease severity. For RSV bronchiolitis lengths of stay in European hospitals range from a low of 4 days to a high of 10 days. The Infección Respiratoria Infantil por Virus Respiratorio Sincitial Study Group in Spain conducted 2 prospective observational studies in 14 and 26 neonatal units, respectively, on nonprophylaxed neonates to determine hospitalization rates for respiratory syncytial viral illness during 2 consecutive RSV seasons. Throughout each respiratory season the study group followed premature infants of < or =32 weeks gestational age at birth, representing an annual birth cohort of approximately 100 000 infants. A total of 584 infants who were < or =32 weeks gestational age in the first season and 999 in the second season were followed at monthly intervals. The nonprophylaxed hospitalized group was compared with the nonprophylaxed, nonhospitalized group, and presumptive risk factors were determined for rehospitalization among premature infants. These independent variables, similar for both years, were identified as low gestational age, underlying chronic lung disease, living with school age siblings, exposure to tobacco smoke and a chronologic age of < 3 months at the onset of the RSV season.Stable, yet high rates of admission for RSV illness in Spain were observed in this premature group of < or =32 weeks gestational age: 13.4% for 1999; and 13.1% for the year 2000. Of those hospitalized during the 2 years of the study, 18 and 25%, respectively, were admitted to the intensive care unit. With the exception of higher rates of family allergy, multiple deliveries and a lower rate of neonatal morbidity, prognostic variables for high risk of hospital admission in the year 2000 compared with those of the 1999 sample. Findings from this comprehensive, prospective study served as the basis for the development of standards for the prevention of respiratory syncytial virus infection by the Spanish Society of Neonatology.

Development and use of palivizumab (Synagis): a passive immunoprophylactic agent for RSV

Palivizumab (Synagis; Abbott Laboratories), a humanized, monoclonal antibody, prevents lower respiratory tract infection by respiratory syncytial virus (RSV). RSV causes significant morbidity and mortality in young children worldwide and is particularly severe in pre-term infants, children with cardiopulmonary disease, and the immunosuppressed population. The first such genetically engineered agent to be used effectively against a human infectious disease, palivizumab significantly reduces the number of hospitalizations caused by RSV in high-risk infants. This article reviews the preclinical development and clinical experience of palivizumab.

Prevention of respiratory syncytial virus infections in high-risk infants by monoclonal antibody (palivizumab)

Respiratory syncytial virus (RSV) is a major viral pathogen which causes serious respiratory illness in infants and children worldwide. Palivizumab (Synagis) is an anti-RSV monoclonal antibody administered intramuscularly for the prevention of severe RSV respiratory disease in high-risk infants and young children. The IMpact-RSV trial, the pivotal multicenter, randomized, placebo-controlled trial performed in the USA, Canada and the United Kingdom demonstrated an overall 55% reduction in hospitalization rate due to RSV infection in preterm infants (< or = 35 weeks gestation) with and without chronic lung disease (CLD). Subgroup analysis in premature infants without CLD revealed an even greater reduction in RSV hospitalization rates (78%). Adverse events were infrequent and did not differ between placebo and palivizumab groups. Injection site reactions were infrequent and mild; no differences were observed between palivizumab and placebo subjects. Palivizumab does not interfere with administration of other pediatric vaccines. Comprehensive parent education programs regarding prevention of infection, avoidance of risk factors for infection, careful adherence to infection control policies, and recognition of early symptoms of RSV infection remain important components of RSV prevention strategies. In light of the lack of effective vaccines for this serious health risk, palivizumab offers the only option for prophylaxis against RSV disease in high-risk infants.

Respiratory syncytial virus subgroup A in hospitalized children in Zarqa, Jordan

The epidemiology of RSV infection was investigated in 271 children aged less than 2 years admitted to the Zarqa Government Hospital, Jordan with bronchiolitis or bronchopneumonia. Nasopharyngeal washings were cultured and RSV antigen was detected by the direct immunofluorescence technique. Of the 271 specimens, 69 (25.46%) were positive for RSV, representing 50.36% of the respiratory viruses. All RSV isolates were typed as subgroup A by monoclonal antibody and confirmed by RT-PCR. RSV was prevalent in the hospitalised children in the coldest months of the year. The epidemics began in January or February, peaked in spring and then disappeared in summer. This study supports the idea that RSV subgroup A is a major contributor to winter outbreaks of respiratory tract disease in children, and health care workers in Jordan should consider the diagnosis during January-May each year.

Clinical patterns and seasonal trends in respiratory syncytial virus hospitalizations in São Paulo, Brazil

The respiratory viruses are recognized as the most frequent lower respiratory tract pathogens for infants and young children in developed countries but less is known for developing populations. The authors conducted a prospective study to evaluate the occurrence, clinical patterns, and seasonal trends of viral infections among hospitalized children with lower respiratory tract disease (Group A). The presence of respiratory viruses in children's nasopharyngeal was assessed at admission in a pediatric ward. Cell cultures and immunofluorescence assays were used for viral identification. Complementary tests included blood and pleural cultures conducted for bacterial investigation. Clinical data and radiological exams were recorded at admission and throughout the hospitalization period. To better evaluate the results, a non- respiratory group of patients (Group B) was also constituted for comparison. Starting in February 1995, during a period of 18 months, 414 children were included- 239 in Group A and 175 in Group B. In Group A, 111 children (46.4%) had 114 viruses detected while only 5 children (2.9%) presented viruses in Group B. Respiratory Syncytial Virus was detected in 100 children from Group A (41.8%), Adenovirus in 11 (4.6%), Influenza A virus in 2 (0.8%), and Parainfluenza virus in one child (0.4%). In Group A, aerobic bacteria were found in 14 cases (5.8%). Respiratory Syncytial Virus was associated to other viruses and/or bacteria in six cases. There were two seasonal trends for Respiratory Syncytial Virus cases, which peaked in May and June. All children affected by the virus were younger than 3 years of age, mostly less than one year old. Episodic diffuse bronchial commitment and/or focal alveolar condensation were the clinical patterns more often associated to Respiratory Syncytial Virus cases. All children from Group A survived. In conclusion, it was observed that Respiratory Syncytial Virus was the most frequent pathogen found in hospitalized children admitted for severe respiratory diseases. Affected children were predominantly infants and boys presenting bronchiolitis and focal pneumonias. Similarly to what occurs in other subtropical regions, the virus outbreaks peak in the fall and their occurrence extends to the winter, which parallels an increase in hospital admissions due to respiratory diseases.

Epidemiology of acute viral respiratory tract infections in Korean children

OBJECTIVE

Viruses are the most common causes of respiratory tract infection in children. We investigated the aetiologies and the epidemiological features of acute viral respiratory tract infections in Korean children.

METHODS

We tried to isolate respiratory syncytial virus (RSV) and parainfluenza virus from January 1994, influenza virus from February 1995, and adenovirus from April 1996 through August 1998, and identified the isolated viruses by indirect immunofluorescence (IF) staining in the children hospitalized with acute respiratory tract infections (ARTI).

RESULTS

Virus was identified in 360 of 1389 (25.9%) nasopharyngeal aspirates cultured. Of a total of 392 viruses, 164 (41.8%) RSV, 90 (23%) parainfluenza virus, 66 (16.8%) influenza A virus, 54 (13.8%) adenovirus, and 18 (4.6%) influenza B virus were cultured, including cases in mixed viral infections. The male to female ratio of the culture-positive patients was 2:1, and the proportions of the patients aged >6 months, 6-11 months, 1, 2, 3, 4, 5, 6-7, 8-9, and >10 years were 22.5, 29.5, 25.7, 9.5, 3.8, 3.8, 1.7, 1.7, 1.2, and 0.6%, respectively. The major clinical diagnosis was bronchiolitis for RSV, croup for parainfluenza virus, and pneumonia for adenovirus and influenza virus. Infections by RSV, parainfluenza virus, and influenza virus occurred in annual epidemics, and infections by adenovirus occurred annually with or without epidemics. There were somewhat larger epidemics by adenovirus and influenza virus in May to July 1996 and March to June 1997, respectively.

CONCLUSIONS

Viral agents are one of the main aetiologies and the main causes of admission in Korean children with ARTI.

White blood cell count, C-reactive protein and erythrocyte sedimentation rate in respiratory syncytial virus infection of the lower respiratory tract

Laboratory findings such as white blood cell (WBC) count, C-reactive protein (CRP) concentration and erythrocyte sedimentation rate (ESR) level in patients with bronchiolitis, bronchopneumonia and lobar pneumonia caused by respiratory syncytial virus (RSV) were studied. The diagnosis of having RSV infection of the lower respiratory tract was made on the presence of RSV antigen in nasopharyngeal specimens by means of enzyme immunoassay, on chest X-ray appearances and clinical manifestations. The WBC counts in the lobar pneumonia cases (n = 25, 12,288 +/- 6296/mm3) were significantly greater than those for the bronchiolitis (n = 52, 9562 +/- 2720/mm3) and bronchopneumonia (n = 43, 8369 +/- 3714/mm3) cases. The concentrations of CRP in lobar pneumonia cases (n = 25, 6.5 +/- 7.3 mg/dL) were significantly greater than those in the bronchiolitis (n = 52, 1.9 +/- 2.0 mg/dL) and bronchopneumonia (n = 43, 2.1 +/- 2.4 mg/dL) cases. The ESR levels in the lobar pneumonia cases (n = 24, 43.8 +/- 29. mm/h) were also significantly higher than those in the bronchiolitis (n = 34, 20.1 +/- 12.3 mm/h) and bronchopneumonia (n = 40, 24.7 +/- 15.9 mm/h) cases. There were no significant differences in the WBC counts, the CRP concentrations and ESR levels between the bronchiolitis and bronchopneumonia cases. These results suggest that the RSV lobar pneumonia cases are coinfected with some bacterial organisms more heavily than in the RSV bronchiolitis and bronchopneumonia cases.