Comparison of caprine,human and bovine strains of respiratory syncytial virus

Summary A new continuous ovine kidney cell line allowing the growth of caprine, human and bovine respiratory syncytial virus was used to minimize host cell related variations for the direct comparison of the viral ultrastructures, serological relationships and structural protein profiles. Results show that all three strains are closely related although a closer relationship was found between bovine and caprine RS.     

Role of oligosaccharides in the structure and function of respiratory syncytial virus glycoproteins

The contribution of oligosaccharides to the structural and functional make-up of respiratory syncytial (RS) virus G and F proteins was investigated by observing the effects of various oligosaccharide-specific enzymes on their molecular size as well as on virus infectivity. The N-linked oligosaccharides of the F protein were completely removed by endoglycosidase F and N-glycanase. Addition of oligosaccharides to F protein during synthesis was completely inhibited by the drug tunicamycin (TM), an inhibitor of N-linked glycosylation. Glycosylation of the G protein was partially resistant to TM resulting in an 80-kDa form designated GTM. The G protein was estimated to contain approximately 3% N-linked and 55% O-linked carbohydrates, based on migration of G and GTM in polyacrylamide gels. Furthermore, treatment of detergent-extracted G protein with endoglycosidase F and endo-alpha-N-acetylgalactosaminidase, enzymes that specifically cleave N-linked and O-linked oligosaccharides, respectively, generated a variety of partially unglycosylated species, ranging in molecular weight from approximately 80 to 40 kDa. Virus infectivity was sensitive to limited removal of N-linked or O-linked oligosaccharides by endoglycosidases under conditions which did not greatly alter the molecular weight of the G protein. Thus, G and F protein oligosaccharides readily accessible to enzymatic removal are presumed to play an important role in the infectious process.     

Structure of bovine respiratory syncytial virus

Summary Bovine respiratory syncytial (BRS) virus propagated in calf kidney (BK) cell cultures was examined by negative contrast and thin section electron microscopy.In negative stained preparations the virus proved to be of great pleomorphism. Many particles appeared roughly spherical with an overall diamter of 80–450 m. On an average, enveloped viruses covered with spikes measured 200 m in diameter.In ultrathin sections the budding of mature virus particles from the cytoplasmic membrane was clearly visualized. The size of mature viruses was 80–130 m and that of the internal component varied from 11 to 15 m.The similarity with the ultrastructure of human respiratory syncytial (RS) virus as well as of pneumonia virus of mice (PVM) has been pointed out. It is therefore proposed to classify these three viruses together in the metamyxovirus subgroup.     

Pathogenesis of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is recognized as the most important cause of serious lower respiratory tract illness in infants and young children worldwide causing repeat infections throughout life with serious complications occurring in the elderly and immune compromised patient. The level of disease pathogenesis associated with RSV infection is balanced between virus elimination and the nature of the immune response to infection. The innate and adaptive immune responses to RSV infection are not fully elucidated; however, significant progress has been made in understanding the virus-host relationship and mechanisms associated with disease pathogenesis. This review summarizes important aspects of these findings, and provides current perspective on processes that may contribute to RSV disease pathogenesis.     

Molecular epidemiology of respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of viral acute respiratory tract infections in young children. The virus is characterised by distinct seasonality that is dependent upon the latitude and its ability to cause reinfection. Respiratory syncytial virus demonstrates a complex molecular epidemiology pattern as multiple strains and/or genotypes cocirculate during a single epidemic. Previous studies have investigated the relationship between RSV genetic diversity, reinfection, and clinical features. Here, we review the evidence behind this relationship together with the impact that the advancement of whole genome sequencing will have upon our understanding and the need for reconsidering the classification of RSV genotypes.     

呼吸道合胞病毒感染的研究进展

呼吸道合胞病毒是在世界范围内引起婴幼儿呼吸道感染的最常见病原微生物,它不仅可以引起呼吸系统的一些常见症状和体征,而且在肺外器官如中枢神经系统、心血管系统、内分泌系统等各器官也可引起一些尚未被人们普遍认识的肺外表现,而这些临床特点的重要性也愈来愈受到人们的重视.     

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.     

Nosocomial respiratory syncytial virus infections.

We studied the frequency and severity of respiratory syncytial virus infections acquired nosocomially on an infants' ward during a community outbreak. Every three or four days all infants and staff were examined, and specimens were obtained for viral isolation. During two months, 14 of 44 contact infants acquired the virus. All were ill, and four had pneumonia. Infected infants had a significantly longer mean hospital stay (21.5 days) than uninfected ones (9.2 days, P less than 0.001). Risk of nosocomial infection could not be related to age or to underlying disease, but was linked to length of hospitalization: 45 per cent of infants hospitalized for one week or more became infected, and the percentage increased with length of stay. Ten of 24 staff members also acquired the virus and appeared to play a major role as virus carriers. Nosocomial respiratory syncytial virus infection poses a major risk for hospitalized infants and adds to hospital costs.     

Serological studies with respiratory syncytial virus

Summary Cross-neutralization tests with 9 strains of RS virus and antisera prepared against them by intra-nasal infection of ferrets, showed that antigenic variation does occur among RS virus strains. One strain, 8/60, differed from all the other strains tested, and there were smaller differences between some other strains.     

The immunobiology of respiratory syncytial virus infection

There is increasing evidence that young children with severe respiratory syncytial virus (RSV)-induced bronchiolitis are at high risk of developing allergy and asthma during their later life. The determinants for this association are not well understood. Current studies suggest that both genetic backgrounds and unique characteristics of the virus play critical roles in determining the type of immune responses to RSV infection, leading to altered regulation of airway tone associated with wheezing. In susceptible subjects, RSV may either enhance the Th2 immune response or decrease the Th1 immune response. This altered Th1/Th2 cytokine response associated with RSV infection is not commonly observed among other RNA viruses, suggesting that RSV may have unique characteristics. Multiple clinical studies support the link between severe RSV bronchiolitis and the subsequent development of allergy and asthma. This link will be further tested by the ongoing large studies on the effect of early RSV intervention on the development of allergy. The administration of palivizumab, an anti-RSV monoclonal antibody, seems to be helpful for RSV prevention and treatment at early stage. There are no effective RSV vaccines available, and this is, at least in part, because of the poorly understood immunology and pathogenesis of RSV disease. The use of experimental animal models has led to a better, but not sufficient, understanding of the immunologic basis of RSV-induced disease, particularly asthma. Further studies on the immunopathology of RSV infection with animal models, including the nonhuman primate models, may help develop effective RSV vaccines.     

Outbreak of respiratory syncytial virus in France

A report is given of an outbreak of respiratory syncytial virus infection in a neonatal unit in France. Twenty-three of 32 infants were infected (72 %) despite infection control procedures. Prophylactic administration of non-specific gamma globulins was associated with a significant decrease in infection rate (p < 0.05). The administration of transfer factor to infected infants was also associated with a significantly lower rate of severe respiratory diseases (p < 0.05).     

siRNA-mediated inhibition of respiratory syncytial virus replication

The effect of siRNA against respiratory syncytial virus (RSV) was investigated in the cultured cells. MA104 cells were inoculated by RSV and transfected by different variants of siRNA against RSV phosphoprotein (P) mRNA or non-specific siRNA as a control. The inhibition of RSV was assessed by microscopically studying the cells, titrating the virus, and estimating viral RNA quantity in the culture supernatants by real-time polymerase chain reaction (PCR). The most potent variants of siRNA caused an up to 8-day delay of microscopically detectable syncytium generation to 8 days, an up to 280-fold decrease in viral titers, and an up to 40-fold reduction in viral RNA quantity in the supernatants, as compared to the controls (p < 0.001). RSV mRNA is a suitable target for siRNA-mediated RSV replication inhibition, promising an advance in the treatment of RSV infection.     

A stat-method of determining respiratory syncytial virus

For rapid detection of RS virus we have modified agglutination test with staphylococcus coated with RSV-antibody which allows the virus titer to be determined within 3-5 min. The results of RS virus titration in the yield compared with those obtained by CFT and CPE tests showed our modified test to be twice as specific and sensitive (60-80 ng/ml). This modification of the coagglutination test with sensitized staphylococcus and the method of running the test on a row of slides may be used in virological and serological laboratories as well as in infectious hospitals and outpatient wards.     

Reinfection of mice with respiratory syncytial virus

The origin and clinical significance of vestibular papillae were evaluated by comparing histological features with the presence of human papillomavirus (HPV) types 6/11 and 16/18, as revealed by Southern blot DNA hybridization. Twenty women with vestibular papillomatosis underwent clinical evaluation and follow-up. When available, male partners were also examined. Histological changes suggestive of HPV infection were present in all the 20 specimens. Sixteen cases (80%) contained DNA sequences homologous to the viral probes. In particular, 12 cases (60%) reacted with the HPV 16/18 probe. Follow-up for more than 18 months revealed no variation in the distribution and appearance of vestibular papillae. No male partner showed signs of HPV lesions. The study shows that HPV 16 is frequently associated with vestibular papillae but does not support a productive infection. Therefore the most appropriate management of these patients should be evaluated clinically in each individual case.     

Active and passive immunisation against respiratory syncytial virus

RSV is a major cause of respiratory illness in infants under 2 years of age. Evidence is accumulating that it is also underestimated as a cause of respiratory infection in adults, the elderly and immunocompromised individuals. Active interventions to control the impact of RSV infection have been hampered by a lack of understanding of the immune response to RSV in different age groups. A number of different strategies for developing RSV vaccines have been pursued, including live attenuated vaccines, genetically engineered live and subunit vaccines and peptide vaccines with varying degrees of success. The target populations for RSV vaccines include infants, the elderly and women of childbearing age, but the efficacy of different vaccines may differ according to age. Desirable immune responses and immune correlates of protection to RSV in humans remain uncertain and determining these is critical for introduction of any vaccines. Prophylaxis and treatment of RSV in infants using human immunoglobulin containing high titres of RSV specific neutralising antibody (RSV-Ig) has shown limited success in different infant populations. Prophylaxis of premature infants with RSV-Ig, particularly those with bronchopulmonary dysplasia, has demonstrated limited clinical efficacy against RSV. In contrast, there are significant safety concerns for use of this preparation for prophylaxis in infants with congenital heart disease and no demonstrable efficacy in treatment of RSV disease in healthy infants. The cost of the preparation will limit use to highly selected infant groups. Production of humanized monoclonal antibodies to RSV offers another potential passive immunotherapy intervention for RSV, with increased specific activity and reduced side effects, although its use remains experimental.     

New drugs and treatment for respiratory syncytial virus

The respiratory syncytial virus (RSV) is a global health problem affecting infants and the elderly and claiming more lives than AIDS in many parts of the world. Only two antibody drugs are approved for its prevention, and ribavarin, a relatively nonspecific antiviral, is used for treatment. In the mid-1990s, a number of pharmaceutical and biotech companies initiated research programs against RSV. Together, the academic and the industrial R&D covered the whole spectrum of antibodies, vaccines, synthetic small molecule antiviral and antisense technology, and at one point, accounted for at least 25 active R&D programs. However, coincident to the marketing of the monoclonal antibody palivizumab (Synagis) in 1998, a sharp decline in such projects ensued. Many companies recently cancelled RSV projects during a prioritisation of their R&D portfolios although the continuing medical need, large market size and sales projections clearly indicate that a safe and effective RSV drug or vaccine is likely to attain blockbuster status. Today RSV receives an insignificant fraction of the R&D budget compared with AIDS, for example. This article reviews the present status of the anti-RSV regimen, covers drugs in the market and in development, and attempts to link basic research to industrial drug development, animal models of RSV, clinical trials, current clinical management, and present and future market projections. It is hoped that the unmet medical need of the victims of RSV will encourage continued involvement of the pharmaceutical and biotechnology industry in developing safe and effective prevention and treatments for RSV.     

Influenza and respiratory syncytial virus in the elderly

Respiratory infections are one of the leading causes of morbidity and mortality worldwide: influenza and respiratory syncytial virus (RSV) are the predominant pathogens responsible. Annual vaccination and the use of antiviral drugs provides both protection and treatment against influenza, particularly protecting those patients most at risk, including the elderly and individuals with chronic comorbidities. Currently, there are extremely limited options in the protection against RSV infection, making those at-risk patients vulnerable to serious disease, complications and death. This review focuses on recent trends in respiratory illness in the elderly, particularly focusing on the burden of influenza and RSV on hospitalizations and mortality. We discuss the potential benefit of influenza vaccination on these outcomes, including the recent controversial debate over the effectiveness of influenza vaccination.     

Primary respiratory syncytial virus infection in mice

A mouse model of respiratory syncytial virus (RSV) infection is described. A high-titered, large-volume inoculum results in replication of RSV to a high titer in lungs of BALB/c mice. Mice older than 15 weeks of age are more susceptible to RSV infection. Titers up to 10(6.9) plaque-forming units (pfu)/gram lung can be attained in 32-week-old mice. Older mice experience a clinical illness manifested by ruffled fur, reduced activity, and weight loss. Lung histology of older mice infected with RSV shows bronchiolitis and increased number of lymphocytes and macrophages in alveolar spaces compared with that of mice less than 8 weeks old. This model will serve as the basis for investigating immunodeterminants of recovery and protection from RSV infection.     

Detection of antibody to bovine syncytial virus and respiratory syncytial virus in bovine fetal serum.

Batches of commercial fetal bovine serum, described by the suppliers as antibody-free, all contained antibody to bovine syncytial virus (BSV) when tested by indirect immunofluorescence. Antibody to bovine respiratory syncytial virus (RSV) was not detected in these sera. Twenty-four percent of individual fetal bovine sera contained antibody to BSV, and 14% contained antibody to RSV when tested by indirect immunofluorescence. BSV antibody titers in fetal sera from dams with high BSV antibody levels were variable but always higher than RSV antibody titers. Radial immunodiffusion studies with BSV-positive sera revealed the presence of immunoglobulin M (IgM), IgG, and IgA, but the quantity of these immunoglobulins was not directly related to the BSV antibody titers. The evidence suggests that the antibody present in fetal sera arose as the result of infection rather than from maternal transfer across the placenta.