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.     

The use of semi-automated EBV IgG avidity determination for the diagnosis of infectious mononucleosis

The diagnosis of acute Epstein-Barr virus (EBV) infection is based frequently on the combination of positive viral capsid antigen (VCA) IgM antibodies and negative EB viral nuclear antigen 1 (EBNA-1) IgG antibodies. However, both VCA IgM and EBNA-1 IgG can provide false positive and false negative results. Therefore, situations in which the EBV serology remains unclear are not uncommon. Determination of EBV IgG avidity can clarify the EBV status in these patients. So far, mainly immunofluorescence assays have been used for this purpose. These tests are laborious, their evaluation is subjective, and automation is difficult. Therefore, two commercially available microtiter plate enzyme immunoassays (EIA) were compared for their usefulness for semi-automated EBV IgG avidity determination. One assay is based on a mixture of EBV antigens, the other assay uses a synthetic peptide of the VCA-complex. Patient sera of confirmed acute and past EBV infections were tested for avidity by both assays. The results with the antigen mixture assay proved to be highly sensitive (100%) and specific (100%). Avidity index calculations on the basis of one-point-quantification titers gave better results than calculations using OD values. Determination of EBV IgG avidity by the peptide assay was complicated by the fact that it was less sensitive than the antigen mixture assay for IgG detection in acute EBV infections. On the other hand, about 30% of the samples had to be retested with the peptide assay in a higher dilution because the IgG units in initial testing fell outside the range covered by the standard curve. Using OD values of the peptide EIA, the sensitivity was 99% but the specificity of detection of acute EBV infections was only 86%. Thus, while the peptide EBV avidity assay is unsuitable as a confirmatory assay, avidity testing with the antigen mixture assay is a useful tool to resolve equivocal EBV serologies. Avidity assays on the basis of EIA can be automated which should lead to wider use of this methodology. J. Med. Virol. 54:145–153, 1998. © 1998 Wiley-Liss,Inc.     

Molecular epidemiology and disease severity of respiratory syncytial virus in relation to other potential pathogens in children hospitalized with acute respiratory infection in Jordan

Human respiratory syncytial virus (HRSV) is the major viral cause of acute lower respiratory tract infections in children. Few data about the molecular epidemiology of respiratory syncytial virus in developing countries, such as Jordan, are available. The frequency and severity of infections caused by HRSV were assessed in hospitalized Jordanian children <5 years of age compared with other potential etiological agents. Overall a potential pathogen was detected in 78% (254/326) of the children. HRSV was detected in 43% (140/326) of the nasopharyngeal aspirates. HRSV was found more frequently during the winter (January/February), being less frequent or negligible by spring (March/April). Analysis of 135 HRSV-positive strains using restriction fragment length polymorphism showed that 94 (70%) belonged to subgroup A, and 41 (30%) to subgroup B. There were also two cases of mixed genotypic infection. Only four of the six previously described N genotypes were detected with NP4 predominating. There were no associations between subgroup or N-genogroup and disease severity. HRSV was significantly associated with more severe acute respiratory infection and the median age of children with HRSV was lower than for those without. Next in order of frequency were adenovirus (116/312: 37%), human bocavirus (57/312: 18%), rhinovirus (36/325: 11%), Chlamydia spp. (14/312: 4.5%), human metapneumovirus (8/326: 2.5%), human coronavirus NL63 (4/325: 1.2%), and influenza A virus (2/323: 0.6%). Influenza B; parainfluenza viruses 1-4, human coronavirus HKU1 and Mycoplasma pneumoniae were not detected.     

Prevalence and clinical characteristics of human respiratory syncytial virus in Chinese adults with acute respiratory tract infection

Respiratory syncytial virus (RSV) is a leading cause of respiratory tract illnesses worldwide. Although the prevalence and clinical manifestations of the two subtypes, RSV‐A and RSV‐B, have been studied in some detail in infants and young children, they have not been determined in adults. To evaluate the prevalence of the RSV subtypes and disease severity between RSV‐A and RSV‐B infections in adults, nasal and throat swabs that were collected from patients ≥15 years old who sought medical care for acute respiratory infections at the Fever Clinic of the Peking Union Medical College Hospital in Beijing, China between May 2005 and April 2010. The samples were tested for RSV infection using PCR and sequencing analysis. RSV was detected in 95 (1%) of the adult patients, of whom 53 (55.8%) were positive for RSV‐A and 42 (44.2%) for RSV‐B. The incidence of RSV infections increased with age (χ² = 37.17, P = 1.66E?07). Demographic data and clinical manifestations of RSV‐A were similar to those of RSV‐B. Although RSV‐A and RSV‐B co‐circulated during the 2005–2006 and 2008–2009 seasons, RSV‐A was predominant in the 2006–2008 seasons, whereas RSV‐B was predominant in the 2009–2010 season. Upper respiratory tract infections were diagnosed in most RSV‐infected patients (n = 80, 84.2%), and three patients suffered from pulmonary infection. This is the first study to provide data on the prevalence and clinical manifestations of RSV subgroups among Chinese adults with fever and acute illness, over five successive epidemic seasons. J. Med. Virol. 85:348–353, 2013. © 2012 Wiley Periodicals, Inc.     

Immunoglobulin class-specific antibody response in respiratory syncytial virus infection measured by enzyme immunoassay

Immunoglobulin class-specific enzyme immunoassay (EIA) was used for determination of antibody responses in sera collected from 26 children with acute primary respiratory syncytial virus (RSV) infections. All 26 patients had IgG antibody responses with a significant titer increase in 24 (92%); an IgM antibody response was detected in 19 of the 26 (73%). From patients aged 6 months or less only 5 of 8 produced detectable IgM antibodies, whereas all patients aged 1–2 years did so. IgM antibodies appeared within 1 week after onset of illness and persisted from 20 days to 2–3 months. An IgA antibody response was observed in 20 of 26 (77%) patients with a significant titer increase detected in 17 of 26 (65%) patients. In some patients the persistence of IgA antibodies followed that of the IgM antibodies, but in others the IgA antibody titers remained stable up to the end of the follow-up. The most sensitive assay system for serological diagnosis of acute RSV infection in children was the determination of titer increases by IgG antibody.     

Local antibody production and respiratory syncytial virus infection in children with leukaemia

Children undergoing therapy for acute lymphoblastic leukaemia (ALL) are at increased risk of severe viral respiratory infection, and some find it difficult to terminate virus secretion. This increased severity may result from a defect in the mucosal immune response. To test this hypothesis, nasal immunoglobulin secretion and specific antiviral antibody responses to infection with respiratory syncytial (RS) virus in children with ALL have been compared with those in a normal age-matched comparison group. Children with leukaemia secreted normal levels of IgA and slightly raised IgM levels. IgG levels were depressed. Following RS virus infection, the majority of children with leukaemia secreted normal amounts of IgA and IgG nasal antibody and successfully cleared the virus. However, three of the 13 children studied made poor or undetectable nasal antibody responses, which correlated with their inability to clear the virus.     

Comparison of strain-specific antibody responses during primary and secondary infections with respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in infants. RSV repeatedly reinfects individuals: this may be due in part to the variability of the attachment (G) glycoprotein and changes in this protein have been shown to be under positive selection. Infants experiencing their primary infection show a genotype-specific antibody response with respect to the variable regions of the G protein. A prospective study of RSV infections in a birth cohort in rural Kenya identified infants experiencing repeat infections with RSV. The serum antibody responses of these infants were investigated with respect to their anti-RSV reactions in an enzyme-linked immunosorbent assay (ELISA) and the specificity of the response to a variable region of the G protein by ELISA and immunoblotting using bacterially expressed polypeptides representative of the currently circulating strains of RSV. The results presented here confirm that the primary antibody response to the variable regions of the G protein is generally genotype-specific, but show that the response may become cross-reactive (at least within group A viruses) during secondary infections even where the secondary infection is of the same genotype as the initial infection. Also, some infants who did not mount a detectable antibody response to whole RSV antigens during their primary infection nevertheless showed genotype-specific responses to the G protein. In conclusion, the strain-specific nature of the serum antibody response to the variable regions of the G protein of RSV observed in primary infections can become cross-reactive in subsequent reinfections.     

Appearance of complement components and immunoglobulins on nasopharyngeal epithelial cells following naturally acquired infection with respiratory syncytial virus

Nasopharyngeal epithelial cells (NPEC) were collected from 144 infants and children with respiratory syncytial virus (RSV) infection, and were analyzed by fluorescent antibody techniques for the presence of cell-bound complement (C^/₃), IgA, IgC, and IgM class of immunoglobulins (Ig), and respiratory syncytial virus antigen. Viral antigen was present on the surface of NPEC in 100% of samples obtained in the first 3 days of illness. The percentage of patients positive for RSV antigen declined steadily, so that no patient still expressed viral antigen on NPEC by 57 days after the onset of illness. Cell-bound IgA, IgC, and IgM could be detected in most of the samples tested in the first 13 days after the onset of illness. Subsequently, the frequency of detection of cell-bound Ig gradually declined. Only 8–3 3 % of patients tested 57 days after the onset of illness expressed IgA, IgG, or IgM on NPEC. About 45% of samples tested in the first 8 weeks after the onset of illness exhibited complement binding to NPEC. The percentage of subjects showing cell-bound C^/₃ reached a maximum at 8–13 says after the onset of illness, while cell–bound C^/₃ could not be detected in any of the samples collected 57–90 days after the onset of illness. Although cell-bound C^/₃ was generally present in association with cell-bound Ig on NPEC, in a small percentage (4.6%) of patients cell-bound C^/₃ could be detected in the absence of any cell–bound Ig. Cell-bound C^/₃ and IgA, IgG, and IgM were present with equal frequency in patients with all forms of clinical disease caused by RSV, and in patients less than or greater than 6 months of age at the onset of illness.     

Shift in the timing of respiratory syncytial virus circulation in a subtropical megalopolis: Implications for immunoprophylaxis

Respiratory syncytial virus (RSV) is the most common cause of severe respiratory infections worldwide, and an important cause of childhood bronchiolitis, pneumonia, and mortality. Although prevention of RSV infection by immunoprophylaxis with palivizumab has proved effective, a precise understanding of the timing of RSV outbreaks is necessary to ensure that infants are protected when RSV is circulating. In this study a consistent shift in the seasonal patterns of RSV circulation in southeast Brazil (São Paulo) is reported based on the analysis of 15 years of viral surveillance. Surveillance was conducted from 1996 to 2010 and involved the collection of samples from children with symptoms of acute respiratory infection. Putative changes in school terms, in the proportion of RSV genotypes infecting children and in the seasonal dynamics of several climatic parameters during the period were also investigated. The results revealed a progression in the timing of RSV seasons, with a shift in the onset and peak of RSV epidemics from 2007 onwards. Although lower rainfall and temperatures were associated with the onset of outbreaks, there was no evidence of changes in climate, school terms or in the relative proportion of genotypes in the period analyzed. These findings have direct implications for improving the prophylactic use of palivizumab, and stress the importance of fine tuning prophylaxis with recent surveillance data. In the case of São Paulo, palivizumab prophylaxis should be initiated earlier than suggested currently. Similar adjustments may be necessary in other regions. J. Med. Virol. 84:1825–1830, 2012. © 2012 Wiley Periodicals, Inc.     

Molecular epidemiology of respiratory syncytial virus in Kilifi district, Kenya

Respiratory syncytial virus (RSV) causes significant burden of disease during infancy and childhood. This study examined the genetic relatedness of RSV positive samples from child inpatients and outpatients and a birth cohort from a rural coastal district of Kenya and also the distribution of strains between these three groups. Clinical samples were collected over a 4-year period in Kilifi District, Kenya from community and hospital surveillance. Three hundred ninety seven of 1,044 nasal specimens from children (under 5 years old) attending Kilifi District Hospital, and from community-monitored infants, were positive for RSV by multiplex RT-PCR. Of these, 376 samples were analysed further by restriction fragment length polymorphisms (RFLP) of the nucleocapsid (N) and attachment (G) protein genes. The G gene was sequenced for 109 samples and phylogenetic analysis carried out. The group A samples from Kilifi fell into two clusters based on G gene sequences, while only one group B cluster was observed. One RSV-B sample from 2003 demonstrated the presence of a 60-nucleotide duplication within the G gene, clustering with similar isolates from Buenos Aries from 1999. All had similar sequences to isolates from the UK, USA, Spain, or Uruguay. The Kilifi District samples showed greater than 97% homology to isolates from South Africa and Mozambique and 91-94% homology to isolates from The Gambia. Samples from different sources, clearly differing in disease severity, did not differ in genotype characteristics, suggesting that disease causing variants are a general reflection of infections within this community.     

Clinical characteristics and viral load of respiratory syncytial virus and human metapneumovirus in children hospitaled for acute lower respiratory tract infection

Respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) are two common viral pathogens in acute lower respiratory tract infections (ALRTI). However, the association of viral load with clinical characteristics is not well‐defined in ALRTI. To explore the correlation between viral load and clinical characteristics of RSV and HMPV in children hospitalized for ALRTI in Lanzhou, China. Three hundred and eighty‐seven children hospitalized for ALRTI were enrolled. Nasopharyngeal aspirates (NPAs) were sampled from each children. Real‐time PCR was used to screen RSV, HMPV, and twelve additional respiratory viruses. Bronchiolitis was the leading diagnoses both in RSV and HMPV positive patients. A significantly greater frequency of wheezing (52% vs. 33.52%, P = 0.000) was noted in RSV positive and negative patients. The RSV viral load was significant higher in children aged <1 year (P = 0.003), children without fever and wheezing (P = 0.015 and P = 0.000), days of illness <14 days (P = 0.002), children with bronchiolitis (P = 0.012) and children with RSV single infections (P = 0.000). No difference was found in the clinical features of HMPV positive and negative patients. The HMPV viral load had no correlation with any clinical characteristics. The incidences of severe disease were similar between single infection and coinfection for the two viruses (RSV, P = 0.221; HMPV, P = 0.764) and there has no statistical significance between severity and viral load (P = 0.166 and P = 0.721). Bronchiolitis is the most common disease caused by RSV and HMPV. High viral load or co‐infection may be associated with some symptoms but neither has a significant impact on disease severity for the two viruses. J. Med. Virol. 89:589–597, 2017 . © 2016 Wiley Periodicals, Inc.

     

Prevalence of respiratory syncytial virus IgG antibodies in infants living in a rural area of Mozambique

A case control study was carried out in Manhiça (Mozambique). Serum samples were collected from infants < 1 year of age in hospital to assess the effect of serum antibodies on the incidence of respiratory syncytial virus (RSV) infection. Sera were collected from a total of 31 cases of RSV infection and paired uninfected controls matched for age and sex. Anti‐RSV antibodies were assessed by a membrane fluorescent antibody test (MFAT) for immunoglobulin G (IgG) antibodies and by a neutralizing antibody test. IgG RSV antibodies were of higher prevalence and at higher levels in the control group when compared to the infected case group (P < 0.001), indicating an important role for IgG antibodies in protection. To assess infection before recruitment, IgA RSV antibodies were also measured by MFAT. IgA RSV antibody prevalence was very low in patients and controls (0/31 and 4/31 respectively), suggesting that most of the detected IgG RSV antibody in both groups was of maternal origin. Re‐analysis of data from the subset of 27 matched, IgA RSV antibody negative infant pairs mirrored the full analysis indicating that maternal antibody has an important role in RSV protection. Similar results were obtained when neutralizing antibodies were measured and when the measurement was done against subgroup A virus strain A2, subgroup B virus strain 8/60 and a contemporary subgroup A isolate, Moz00. No significant differences in the reactivity of maternal antibodies with the three virus strains were observed. The data described below represent the first analysis of the role of maternal antibodies in reducing the risk of pediatric infection in developing countries. The results reinforce the concept of maternal vaccination for the control of RSV in very young children in whom the risk and severity of infection are the highest. J. Med. Virol. 67:616–623, 2002. © 2002 Wiley‐Liss, Inc.     

Role of complement in neutralization of respiratory syncytial virus

Serum neutralizing antibody titers to respiratory syncytial virus (RSV) are higher when assayed with guinea pig complement. A number of different mechanisms have been suggested for enhancement of neutralization by complement. The most straightforward is that complement-antibody complexes present a greater steric hindrance to viral entry than with antibody alone. To define the implications of measuring serum neutralizing antibody with and without complement, sera from adults, young children, infants, and cord bloods were run in plaque neutralization assays with representative viruses of the RSV A and B subgroups. Although titers of neutralizing antibody were higher in the presence of complement, the addition of complement did not increase the ability to detect antibody rises after natural infection. Some of the complement effect may be attributable to an inhibition of RSV replication by complement alone. While these observations do not address the role for complement in the pathogenesis of RSV infection, they suggest that neutralization assays performed without complement may be most reflective of physiologic conditions in the respiratory tract.     

Diagnosis of respiratory syncytial virus infection in children: Comparison of viral antigen detection and serology

Direct detection of viral antigen in nasopharyngeal secretion by radioimmunoassay was compared with serology by IgG antibody enzyme immunoassay for diagnostic efficacy in 77 children with clinically suspected respiratory syncytial virus (RSV) infections. Antigen detection gave a positive diagnosis in 26 of 33 (79%) children in whom RSV infection was diagnosed by any of the two methods. The diagnostic efficacy of antigen detection was dependent upon the interval after onset at which specimens were collected; 88% of specimens taken during the first 5 days and 50% of specimens taken 6–10 days after onset of illness were positive. It was also dependent on the age of the patients, the diagnostic efficacy being 88 and 76% in children under and over 6 months of age, respectively.