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PubMed2005

Impact of human metapneumovirus in childhood: comparison with respiratory syncytial virus and influenza viruses.

This study evaluated the overall impact of human metapneumovirus (hMPV) infection in 1,505 children and their households, and compared it with infections due to respiratory syncytial virus (RSV) and influenza viruses. Nasopharyngeal swabs were used at enrollment to collect specimens for the detection of hMPV, RSV, and influenza virus RNA by reverse-transcriptase polymerase chain reaction (RT-PCR). hMPV was detected in 42 children (2.8%), RSV in 143 (9.5%; P < 0.0001 vs. hMPV), and influenza viruses in 230 (15.3%; P < 0.0001 vs. hMPV). Of the 42 hMPV-positive samples, one was also positive for RSV and six for influenza viruses, for a co-infection rate of 16.7%. Clinically, hMPV was identified only in patients with acute respiratory infection, whereas RSV and influenza viruses were also detected in patients with different clinical manifestations. Symptoms with statistically significant different proportions at presentation were fever (more frequent in the hMPV- and influenza-positive children) and wheezing with bronchiolitis or asthma exacerbation (more frequent among hMPV- and RSV-positive cases). The households of the hMPV- and the influenza-positive children had significantly more illnesses, needed significantly more medical visits, received more antipyretics, and missed significantly more work or school days than those of the RSV-positive children. Results show that hMPV is an emerging cause of acute respiratory infection in childhood, and may have a significant clinical and socioeconomic impact on children and their families.

Child, Preschool↗
PubMed2005

A phylogenetic study of human respiratory syncytial viruses group A and B strains isolated in two cities in Japan from 1980-2002.

The circulation pattern and genetic evolution of respiratory syncytial virus (RSV) in Japan were examined based on 109 RSV field strains isolated over 20 seasons (1980-2002) in two cities, Sapporo and Tokyo. The second hypervariable region of the large glycoprotein (G) gene was amplified by RT-PCR and the products sequenced directly. The nucleotide sequences were compared to those representatives of RSV genotypes identified previously. Japanese group A and B isolates clustered into five and four genotypes defined previously, respectively. Another one group A and one group B genotypes, which could not be assigned to previous genotypes, were also identified. Although different genotypes usually co-circulated in each season, the isolates in proximate seasons from two communities were usually located in the same branches. Moreover, the strains with genotypes defined previously were usually isolated at the same time as each reference strain of Western countries. Several mutant group B strains with 1-20 longer amino acid G proteins were newly identified in Sapporo. These findings suggest that Japanese RSV strains underwent geographical and also temporal clustering while participating in RSV genetic evolution in a global setting. In addition, Japanese strains, especially group B, might have evolved individually in each community, sometimes changing the length of the G protein.

Amino Acid Sequence↗
PubMed2005

Detection of respiratory syncytial virus genome by subgroups-A, B specific reverse transcription loop-mediated isothermal amplification (RT-LAMP).

Annual seasonal outbreaks of respiratory syncytial virus (RSV) infection occur every winter. Most patients are diagnosed clinically by a rapid detection kit for RSV protein(s) from nasopharyngeal secretion (NPS), but some problems have been reported on the specificity and sensitivity of such rapid detection kits. To ratify these issues, a sensitive, specific, simple, and rapid molecular based diagnostic method is expected to be introduced and we have developed a method to detect the RSV genome of subgroups A and B independently by reverse transcription loop-mediated isothermal amplification (RT-LAMP). We detected the genomic RNA corresponding approximately to 0.1 TCID 50 in the sample by RT-LAMP for both RSV subgroups under isothermal condition within 60 min after extraction of RNA. Specific DNA amplification was monitored by a real-time turbidimeter and the quantity of RNA was calculated. The RSV genome was detected in 47 of 50 NPS by RT-LAMP, and in 42 by nested RT-PCR, whereas virus isolation was positive for 29 and enzyme-linked immunoassay (EIA) for 34. RSV subgroup A was detected in 25 by RSV RT-LAMP A, RSV subgroup B in 23 by RSV RT-LAMP B, and dual infection with RSV subgroups A and B was identified in one case. They were confirmed with digestion with a specific restriction enzyme, Bgl II. The results showed the potential clinical feasibility of RT-LAMP as a useful diagnostic tool for the detection of RSV with high sensitivity similar to nested RT-PCR.

Genome, Viral↗
PubMed2005

Intragroup antigenic diversity of human respiratory syncytial virus (group A) isolated in Argentina and Chile.

The intragroup antigenic diversity of the G glycoprotein of 226 human respiratory syncytial virus (HRSV) strains isolated in Buenos Aires (Argentina) and Santiago (Chile) between 1995 and 2002 was evaluated by ELISA with a panel of 14 anti-G monoclonal antibodies (MAbs). Out of 226 strains characterized, 172 (76%) belonged to group A and 54 (24%) to group B. Strains from both groups cocirculated throughout the study period in both countries, except in 1996, 2000, and 2002 when only group A strains were isolated. Within group A 23 different antigenic patterns were found as defined by the combination of reactivities with eight strain-specific anti-G MAbs. These antigenic patterns showed different behavior regarding their circulation. Some major patterns were observed in most years with variable proportions; other minor patterns were present in low proportions during 1 or 2 years and then were apparently replaced by new patterns. Some antigenic patterns occurred both in Argentina and Chile during the same epidemics. Since no strain-specific MAbs were available for group B, we could not evidence the antigenic variability within group B. These are the first data on antigenic characterization of HRSV strains isolated in Argentina and Chile. It is shown that the ELISA with MAbs directed against the G protein of RSV is a valuable tool. These results will also provide useful information for further studies to evaluate the antigenic variability of HRSV strains in relation with genetic characteristics.

Antigenic Variation↗
PubMed2005

Molecular epidemiology of human respiratory syncytial virus subgroup A over a six-year period (1999-2004) in Argentina.

Human respiratory syncytial virus (HRSV) is the main viral cause of acute lower respiratory tract infections in children. Little information about the molecular epidemiology of HRSV in developing countries, such as Argentina, is available. By RT-PCR, we subgrouped 353 HRSV isolates over six consecutive epidemic seasons (1999-2004) and few isolates from 1997. Between them, 232 (65.7%) belonged to subgroup A and 121 (34.3%) to subgroup B. Therefore, the nucleotide, amino-acid variability and phylogenetic relations of 78 HRSV subgroup A isolates, were analyzed using RFLP and sequence analysis of the G-protein gene. The results showed that there were two main restriction patterns (PA1 and PA2) and two previously described genotypes (GA2 and GA5) cocirculating in Buenos Aires, without evidence of alternation between them during the studied period. The Argentine sequences were compared with previously reported molecular data from other countries. It showed that viruses genetically related circulated the same years within neighboring countries and the sequences from long-distant places were closely related to Argentine sequences, but they belonged to different sampling years. The data reported here support the growing database on the molecular diversity of HRSVA circulating in Latin America in children under 2 years of age and contributes to describe the pattern of global spread of this virus.

Argentina↗
PubMed2001

Occurrence and severity of infections caused by subgroup A and B respiratory syncytial virus in children in southeast Brazil.

The frequency and severity of infections caused by respiratory syncytial virus (RSV) were assessed in children <2 years of age seen at the emergency department. The frequency of RSV detection in the clinical virology laboratory during the past 3 years was also analyzed retrospectively. RSV was found in 21.6% (188/869) of the samples collected from children seen at the emergency department and was found to be more frequent during the autumn, being less frequent or negligible by midwinter. RSV subgroups A and B co-circulated within the same time period in children seen at the emergency department, with varying predominance of either subgroup. There was no significant association of RSV subgroup with disease severity, but only a trend for RSV subgroup B being more frequent in children with risk factors for severe disease.

Acute Disease↗
PubMed2006

Respiratory syncytial virus infection in a murine model of cystic fibrosis.

Viral respiratory infections play an important role in the development and progression of pulmonary disease in cystic fibrosis (CF). The CF mouse model provides a tool to examine the relationship between the cystic fibrosis transmembrane conductance regulator (CFTR) defect and lung disease. This work investigates the cellular response to a common viral pathogen, respiratory syncytial virus (RSV) in the lung of CF mice. RSV was administered by intranasal inoculation of CFTR(tm1Unc)-Tg(FABPCFTR)1Jaw/J (CFTR-/-) and control mice. At day 5 post infection, viral titers, bronchoalveolar fluid nitrate levels (BALF) cell and differential counts, histology and studies on airway mechanics were performed. CFTR-/- mice had an impaired ability to clear RSV. This was associated with an exaggerated inflammatory response (increased lymphocytes and neutrophils) in BALF of RSV-infected CFTR-/- mice and a decreased ability to generate nitric oxide (NO) (measured as BAL nitrate). Lung histopathology of RSV-infected CFTR-/- mice demonstrated increased inflammation compared to RSV (-) CFTR-/- and control mice (regardless of RSV treatment). The airway response to methacholine was increased by RSV infection in CF mice when compared to controls. The CFTR-/- mouse exhibits an aberrant response to RSV infection. This model should be useful in providing further mechanistic information on the biology of respiratory viruses in mammalian models, and provide new insights into the pathogenesis of airway inflammation in patients with CF.

Animals↗
PubMed2006

Genetic diversity among respiratory syncytial viruses that have caused repeated infections in children from rural India.

Respiratory syncytial virus (RSV) causes repeat infections throughout life. Antigenic variability in the RSV G protein may play a significant role in reinfections. A variable region of the RSV G gene was analyzed for 14 viruses from seven children who experienced initial and repeat infections. Eleven group A strains were in clades GA2 and GA5 and the three group B viruses were in the newly identified BA clade. In five children reinfections were caused by a heterologous group or genotype of RSV. Two children experienced infection and reinfection by viruses of the same clade, these virus pairs differed by only two to three amino acids in the region compared. This is the first report of RSV nucleotide sequence analysis from India and one of the few molecular characterizations of paired RSV from reinfections. Determining the molecular basis of reinfections may have important implications for RSV vaccine development.

Amino Acid Sequence↗
PubMed2006

Distinct patterns of evolution between respiratory syncytial virus subgroups A and B from New Zealand isolates collected over thirty-seven years.

Respiratory syncytial virus (RSV) is the most important cause of viral lower respiratory tract infections in infants and children worldwide. In New Zealand, infants with RSV disease are hospitalized at a higher rate than other industrialized countries, without a proportionate increase in known risk factors. The molecular epidemiology of RSV in New Zealand has never been described. Therefore, we analyzed viral attachment glycoprotein (G) gene sequences from 106 RSV subgroup A isolates collected in New Zealand between 1967 and 2003, and 38 subgroup B viruses collected between 1984 and 2004. Subgroup A and B sequences were aligned separately, and compared to sequences of viruses isolated from other countries during a similar period. Genotyping and clustering analyses showed RSV in New Zealand is similar and temporally related to viruses found in other countries. By quantifying temporal clustering, we found subgroup B viruses clustered more strongly than subgroup A viruses. RSV B sequences displayed more variability in stop codon usage and predicted protein length, and had a higher degree of predicted O-glycosylation site changes than RSV A. The mutation rate calculated for the RSV B G gene was significantly higher than for RSV A. Together, these data reveal that RSV subgroups exhibit different patterns of evolution, with subgroup B viruses evolving faster than A.

Biological Evolution↗
PubMed2002

Genetic susceptibility to respiratory syncytial virus infection in inbred mice.

Differences in the severity of respiratory syncytial virus (RSV)-induced lower respiratory disease in infants have been attributed to multiple environmental and genetic factors. To identify the genetic factor(s) influencing RSV susceptibility, we examined RSV infection in eight inbred mouse strains. Lung RSV titers differed significantly between mouse strains: the RSV titers were 15-fold higher in AKR/J (permissive) mice compared with C57BL/6J (resistant) mice at 4 days after inoculation. This strain-specific difference in RSV titers suggested that susceptibility to RSV infection was attributable to genetic differences between strains. To examine the mode of inheritance of RSV susceptibility, F1 and backcross (F1 x AKR/J) progeny were infected and RSV titers determined. RSV titers in the F1 progeny were similar to those found in the resistant (C57BL/6J) parent, suggesting resistance was inherited as a dominant trait. The distribution of RSV titers in backcross progeny were discordant with that predicted for a single gene effect, suggesting susceptibility was influenced by more than one gene. These data suggest that RSV susceptibility is a multigenic trait that should be amenable to resolution by genomic analysis.

Animals↗
PubMed2002

Seasonal variation in respiratory syncytial virus chest infection in the tropics.

Respiratory syncytial virus (RSV) is the most important cause of lower respiratory tract infection (LRTI) in young children. We determined if there was a seasonal variation in Malaysia in the incidence of RSV infection in young children admitted with LRTI, and possible associations of RSV infection with local meteorological parameters. A total of 5,691 children, aged less than 24 months and hospitalized with LRTI (i.e., bronchiolitis and pneumonia) between 1982-1997, were included in this study. Nasopharyngeal samples were collected and examined for RSV by immunofluorescence, viral culture, or both. Seasonal variations were determined by analyzing the monthly RSV-positive isolation rate via time series analysis. Possible correlations with local meteorological parameters were also evaluated.RSV was isolated in 1,047 (18.4%) children. Seasonal variations in RSV infection rate were evident and peaked during the months of November, December, and January (test statistics [T] = 53.7, P < 0.001). This seasonal variation was evident for both bronchiolitis and pneumonia categories (T = 42.8 and 56.9, respectively, P < 0.001). The rate of RSV infection appeared to correlate with the monthly number of rain days (r = 0.26, P < 0.01), and inversely with the monthly mean temperature (r = -0.38, P < 0.001). In the tropics, seasonal variations in the incidence of RSV infection are evident, with an annual peak in November, December, and January. This information provides a guide for healthcare provisions and implementation of RSV prevention.

Humans↗
PubMed2001

Respiratory syncytial virus immune globulin: decisions and costs.

A decision analysis was used to evaluate the economic effectiveness of respiratory syncytial virus immune globulin (RSVIG) prophylaxis on selected pediatric populations at risk for developing RSV bronchiolitis or all respiratory illness-related hospitalizations. We compared costs, outcomes, and cost-effectiveness of administering RSVIG to no treatment in different pediatric populations, including those at risk of developing RSV-bronchiolitis and those at risk of developing any respiratory illness-related hospitalization. We observed that if only infants at high risk of severe RSV infections received treatment with RSVIG, a calculated cost saving of about 27,000 dollars per hospitalization prevented were realized. If the Food and Drug Administration (FDA)-approved indications for RSVIG were followed, the cost to prevent one hospitalization due to RSV bronchiolitis would be over 53,000 dollars. If the aim, however, was to prevent all respiratory illness-related hospitalizations for this broader population, a much lower cost (4,000 dollars) to prevent one hospitalization would result. In this situation, cost neutrality was possible, with a therapy cost of 2,843 dollars compared to the actual average therapy cost of 4,444 dollars. Sensitivity analysis showed that the model was relatively insensitive to all variables, with the exceptions of costs related to RSVIG and intensive care unit (ICU) admissions. We conclude that RSVIG resulted in cost savings if therapy were reserved for the infants who are at highest risk for developing severe RSV infections. RSVIG is not cost-effective for preventing RSV bronchiolitis when used according to the FDA-approved indications. Education that emphasizes frequent hand-washing, avoidance of passive smoking, and lessening exposure to sick children remains the least expensive prevention tool.

Antibodies, Monoclonal↗
PubMed1995

A cotton rat model of effectors of immunity to respiratory syncytial virus other than serum antibody.

A model for studying effectors of immunity to respiratory syncytial virus (RSV) was developed. Paris of inbred cotton rats (Sigmodon hispidus) were joined surgically using the technique of parabiosis. One week later, one animal of each pair was primed intranasally with a small volume of RSV suspension. Fourteen days after priming, both animals of each pair were bled for determination of serum neutralizing antibody titers, and challenged intranasally with a standard dose of RSV suspension. Single, unprimed cotton rats were challenged concomitantly and served as controls. Four days after challenge, all animals were sacrificed for virus titration of nasal tissues and lungs. Parabiosed cotton rats were surgically separated at varying intervals between priming and challenge (days 7, 9, 12, or 14 after priming) or were kept joined until sacrificed (day 18). Significant transfer of nasal and pulmonary immunity from primed to unprimed parabionts began 9 days after priming, gradually increasing through 18 days. Resistance to RSV challenge in spite of low levels of serum neutralizing antibody suggests that non-antibody immunologic mediators were responsible for the transferred immunity. Evidence is presented for three broad categories of RSV immunologic effectors: systemic, local with a transient systemic phase, and local without a systemic phase. These categories are now amenable to further study using the described model.

Animals↗
PubMed2006

Beyond randomized controlled trials: a "real life" experience of respiratory syncytial virus infection prevention in infancy with and without palivizumab.

A population-based study of the impact of palivizumab on confirmed Respiratory Syncytial Virus (RSV) hospitalizations over a 7-year period within and between two similar health regions . Clinicians in Calgary implemented palivizumab prophylaxis for high-risk infants during the last four RSV seasons; clinicians in Edmonton did not. The two cities are part of a unified health care system and similar sociodemographics. Infants <36 weeks (wk) of gestational age (GA) were identified. RSV prophylaxis data and RSV-hospitalizations for high-risk infants eligible for prophylaxis were reviewed, as well as that of moderate-risk infants (33-35 weeks GA) for whom RSV prophylaxis was not given a high priority in the recommendations published by the Canadian Paediatric Society (CPS). Prevalence of RSV hospitalization before and after palivizumab was determined (1995-1998 and 1999-2002, respectively). There were 411 high-risk infants eligible for palivizumab prior to its provision (Pre) and 496 during the prophylaxis program (Post) in Calgary. There were 401 Pre and 425 Post in Edmonton, where no such prophylaxis program was implemented. In Calgary where palivizumab was offered (Post), RSV hospitalization was significantly reduced: 7.3% Pre versus 3.0% Post (OR, 2.53, 95% CI, 1.34, 4.76). No reduction was observed in Edmonton where palivizumab was not offered: 5.0% Pre versus 7.1% Post (OR, 1.45, 95% CI, 0.81, 2.59; P = 0.212). RSV hospitalizations did not change for moderate-risk infants not receiving palivizumab in Calgary (OR, 1.26, 95% CI, 0.75, 2.12; P = 0.389). An RSV prevention program with palivizumab for high-risk infants reduced RSV hospitalizations, providing "real life" evidence of the benefits of this prophylaxis strategy. Further research is required to determine if specific sub-sets of moderate-risk infants would also benefit from an RSV prophylaxis program with palivizumab.

Alberta↗
PubMed2007

Human metapneumovirus and respiratory syncytial virus infections in older children with cystic fibrosis.

BACKGROUND: Human metapneumovirus (hMPV) has been isolated from children with acute respiratory infection worldwide. Its epidemiology remains to be defined in children with cystic fibrosis (CF). We describe the epidemiology and clinical impact of hMPV in CF children and compared it to respiratory syncytial virus (RSV). METHODS: CF children ages 7-18 years were studied prospectively during the 1998 -1999 RSV season. Nasopharyngeal specimens were collected during acute respiratory illnesses and tested for respiratory viruses. Blood specimens were drawn early, mid, and end of the RSV season, and tested for serological evidence of hMPV and RSV infections. Rates of lower respiratory tract illnesses (LRTI) and hospitalizations for pulmonary exacerbations were compared during the time intervals they developed serological evidence of infection to their non-infection intervals. RESULTS: Six of 44 CF children had a virus positive respiratory illness in 56 LTRI events and 18 hospitalizations. Serological evidence of hMPV and RSV infections occurred in 16 and 20 CF children, respectively; 8 had infections with both viruses. A greater proportion of CF children had >or=1 LRTI during their infection intervals compared to their non-infection intervals (13/25 vs. 5/25; P=0.03). A trend for higher rates of LRTI was observed in the infection intervals compared to non-infection intervals (9.5 +/- 11.0 vs. 4.2 +/- 9.9 per 1,000 child-days; P=0.06), and it was significantly greater with a more conservative estimate (one event per child per interval; 7.4 +/- 7.7 vs. 2.6 +/- 5.4 per 1,000 child-days; P <or=0.01). No differences in hospitalizations rates were detected. CONCLUSION: The infection rates and clinical impact observed for hMPV were comparable to that for RSV in CF children 7-18 years of age.

Adolescent↗
PubMedDate not supplied

Molecular epidemiology of respiratory syncytial virus.

Human respiratory syncytial virus (RSV) is the major cause of lower respiratory tract disease in infants. It is unusual in that it causes repeated infections throughout life. Despite considerable efforts there is as yet no satisfactory vaccine available. This paper reviews the molecular epidemiology of the RSV and describes the complex genotypic structure of RSV epidemics. The evolution of the virus is discussed, with particular reference to the antigenic and genetic variability of the attachment glycoprotein.

Adult↗
PubMed1998

Respiratory syncytial virus induces the expression of 5-lipoxygenase and endothelin-1 in bronchial epithelial cells.

Respiratory syncytial virus (RSV) infection causes and exacerbates asthma, yet the mechanism by which RSV triggers asthma is poorly understood. Herein, an in vitro model of RSV infection was established using HEp-2 and BEAS-2B bronchial epithelial cell lines, and the expression of 5-lipoxygenase (5-LO), and endothelin-1 (ET-1) was examined. RSV infection increased the expression of 5-LO mRNA and protein in both cell lines, as detected by RT-PCR and western blot analysis, respectively. The levels of leukotrienes also increased in the supernatants of RSV infected cells. Furthermore, RSV infection increased the expression of ET-1 mRNA and protein following RSV infection in a time-dependent manner. It is concluded that RSV infection upregulates the expression of ET-1 and 5-LO in the epithelial cells leading to the production of leukotrienes, which may mediate the consequent exacerbation of asthma.

Arachidonate 5-Lipoxygenase↗
PubMed2000

MIP-1alpha is produced but it does not control pulmonary inflammation in response to respiratory syncytial virus infection in mice.

The intent of this study was to compare the cellular and biochemical inflammatory responses of mice infected with the paramyxovirus pathogens respiratory syncytial virus (RSV) and pneumonia virus of mice (PVM). Although RSV is not a natural pathogen of mice, it has been used extensively in mouse models of the human disease, as a limited respiratory infection can be established via intranasal inoculation of virus at high titer. In earlier work, we found that acute infection with the natural rodent pathogen, PVM, elicited a rapid and sustained pulmonary inflammatory response (peak, 1.7 x 10(6) leukocytes/ml BAL fluid) that was dependent on both local production of MIP-1alpha and signaling via its receptor, CCR1. We find here that MIP-1alpha is also produced in response to RSV, although relatively few leukocytes (<200 ml BAL fluid) are recruited to the lungs in response. Further experiments with CCR1-deficient mice confirm the finding that although MIP-1alpha is produced in response to RSV infection, leukocytes do not respond via this pathway. Among the explanations for these findings, we propose that there are other, as yet to be identified proinflammatory mediators elicited in response to PVM (but not in response to RSV) that serve to prime the leukocytes in vivo, thus enabling them to respond to MIP-1alpha signaling via CCR1. Furthermore, the differences in disease pathogenesis seen in response to each of these pneumovirus infections in mice raise questions regarding the extent to which primary RSV infection in mice can be used as a model of primary RSV infection in humans.

Acute Disease↗