Bovine respiratory syncytial virus protects cotton rats against human respiratory syncytial virus infection

Human respiratory syncytial virus (HRSV) is the most frequent cause of severe respiratory infections in infancy. No vaccine against this virus has yet been protective, and antiviral drugs have been of limited utility. Using the cotton rat model of HRSV infection, we examined bovine respiratory syncytial virus (BRSV), a cause of acute respiratory disease in young cattle, as a possible vaccine candidate to protect children against HRSV infection. Cotton rats were primed intranasally with graded doses of BRSV/375 or HRSV/Long or were left unprimed. Three weeks later, they were challenged intranasally with either BRSV/375, HRSV/Long (subgroup A), or HRSV/18537 (subgroup B). At intervals postchallenge, animals were sacrificed for virus titration and histologic evaluation. Serum neutralizing antibody titers were determined at the time of viral challenge. BRSV/375 replicated to low titers in nasal tissues and lungs. Priming with 10(5) PFU of BRSV/375 effected a 500- to 1,000-fold reduction in peak nasal HRSV titer and a greater than 1,000-fold reduction in peak pulmonary HRSV titer upon challenge with HRSV/Long or HRSV/18537. In contrast to priming with HRSV, priming with BRSV did not induce substantial levels of neutralizing antibody against HRSV and was associated with a delayed onset of clearance of HRSV upon challenge. Priming with BRSV/375 caused mild nasal and pulmonary pathology and did not cause exacerbation of disease upon challenge with HRSV/Long. Our findings suggest that BRSV may be a potential vaccine against HRSV and a useful tool for studying the mechanisms of immunity to HRSV.     

Effect of respiratory syncytial virus infection of HeLa-cell macromolecular synthesis

Cells infected with respiratory syncytial (RS) virus eventually die but there appears to be no specific mechanism for shutting off cellular synthesis of macromolecules. DNA and RNA synthesis, as measured by the incorporation of labelled thymidine or uridine, do not begin to shut down until some time between 11 and 18 h after infection. By 18 h their rates of synthesis are reduced to approx. 50% for DNA and 35% for RNA. Protein synthesis continues throughout the course of infection at approximately the same rate. Synthesis of most of the cellular polypeptides also continues, but the distribution of polypeptides of high and low mol. wt. shifts. The increase in the proportion of those of high mol. wt. includes a peak that represents one of the seven previously identified virion polypeptides. Another consequence of RS virus infection is an increase in glucosamine incorporation, beginning near the end of the virus eclipse period (12 h after infection), which may be associated with virion glycoprotein synthesis. Polyacrylamide-gel electrophoresis of glucosamine-labelled cells reveals that at 18 h after infection two of the three previously identified virion glycoproteins are present.     

Epidemiology of respiratory syncytial virus infection requiring hospitalization in East Denmark

BACKGROUND: Prophylaxis against infection caused by respiratory syncytial virus (RSV) with high titered RSV immunoglobulin or humanized antibody may soon be available in Europe. OBJECTIVE: To study the epidemiology of RSV infections requiring hospitalization in infants <6 months in East Denmark to provide a rational basis for decisions concerning prophylaxis against RSV. METHOD: Populat ion-based retrospective review of case records of infants <6 months admitted to pediatric departments with RSV infection in East Denmark from November 1, 1995, to April 30, 1996. RESULTS: Data were obtained from 459 infants. Seventy-three had predisposing conditions: prematurity, 49; pulmonary disease, 2; congenital heart disease, 7; neurologic disease, 6; others, 9. One preterm infant had bronchopulmonary dysplasia. The incidence of RSV infection requiring hospitalization in East Denmark among infants <6 months was estimated to be 34/1000/season. It was 32/1000/season among term infants and 66/ 1000/season among preterm infants (P<0.001). Infants with predisposing conditions and/or nosocomial infection (n = 24) had significantly more severe courses than otherwise healthy infants (P<0.01). One-hundred thirty infants received respiratory support by nasal continuous positive airway pressure, but only six required mechanical ventilation. No infants died. CONCLUSION: The course of RSV disease in East Denmark was milder than reported elsewhere, possibly as a result of the low prevalence of bronchopulmonary dysplasia in Denmark. However, RSV constitutes a considerable burden to the Danish pediatric health care system, and therefore prophylaxis against RSV is desirable.     

Immunobiology of bovine respiratory syncytial virus infections

This paper describes recent findings on the immunobiology of bovine respiratory syncytial virus (BRSV) infections. The pathobiology of alveolar macrophages and BRSV, and the immunological reaction of cattle to the virus after natural or experimental infection, or vaccination, were studied. Because in severe cases BRSV infection leads to lower respiratory tract disease, replication of BRSV in alveolar macrophages was studied. Alveolar macrophages, which are important aspecific defense cells in the lower respiratory tract, exhibited a high intrinsic resistance to BRSV. Furthermore, BRSV-infected alveolar macrophages produced significantly less nitric oxide (which has a bacteriocidal effect) than uninfected macrophages. The kinetics of antibody titres against the envelope protein G were different from those of antibody titres against the envelope protein F. For example, many animals that are reinfected do not possess antibodies against the G protein. After vaccination or after natural infection, antibody titres against the F and G protein, and against epitopes on the F protein, differed markedly, and also in animals with different MHC haplotypes. These findings may be related to differences in protection. The strains of BRSV that circulate in the Netherlands belong to the subgroups A and AB. There was no evidence for differences in virulence between these subgroups. BRSV could be detected in 30% of lungs obtained from calves suffering from severe lower respiratory tract disease. Based on cross-protection studies, calves that were infected with a virus from a particular BRSV subgroup were protected against reinfection with a virus from a different subgroup. A recombinant gE-protein negative bovine herpesvirus 1 vaccine carrying a gene encoding the G protein of BRSV, and a DNA vaccine encoding the same protein afforded protection after experimental challenge of calves. This offers the possibility to develop effective multivalent (gE-negative BHV1) marker vaccines in the future.     

Use of permissive hypercapnia in the ventilation of infants with respiratory syncytial virus infection

The authors report a case of intraoperative sinus arrest in an otherwise healthy patient undergoing craniotomy for aneurysm clipping after mild subarachnoid hemorrhage. The sinus arrest was precipitated by a rapid infusion of 1500 mg phenytoin and was successfully treated with standard resuscitative measures. The differential diagnosis of intraoperative cardiac arrest and the mechanisms of action of phenytoin are discussed. The authors emphasize the role of phenytoin in cerebral protection.     

Breast-feeding protects against respiratory syncytial virus infections

Eight out of 115 infants admitted to hospital with respiratory syncytial (RS) virus infection had been breast-fed compared with 46 out of 167 controls; this difference was statistically significant. Twenty-one specimens of human colostrum were examined, and all contained RS virus neutralising activity. Specific IgA and IgG were detected in 18 specimens, whereas IgM was detected in none. The titre of IgA antibody was usually higher and correlated more closely to the titre of neutralising activity than that of IgG. Infants inhale milk feeds and regurgitate them through the nose, and the IgA collecting in the respiratory tract might protect against severe respiratory infection. Alternatively, if severe RS virus illness is a sign of hypersensitivity to the virus breast-feeding might protect the infant from an early sensitising infection.     

Respiratory syncytial virus infection in childhood

Respiratory syncytial virus is the most frequent cause of respiratory tract infections in infants and is responsible for annual winter epidemics of acute bronchiolitis. Over the last decades medical therapy has remained unchanged and controversial, despite intensive research. Inhaled bronchodilators are often not effective and should be discontinued if no beneficial response can be documented. Steroids and ribavirin are not indicated in previously healthy infants with acute RSV bronchiolitis. There is some evidence, however, that certain risk groups may benefit from their use. With good supportive care the mortality from RSV infection is now low. Postinfectious alterations in lung function are usually transient and reversible. High-risk infants can be protected from severe RSV infections by monthly infusions of RSV immune globulins. This treatment modality has, however, not gained wide acceptance because of the benign nature of the disease and the high costs and side effects of regular immune globulin infusions. An international consensus statement on the treatment of RSV bronchiolitis may help to reduce the wide differences in clinical practice.     

Animal models for intra-abdominal infection

Animal models are widely used to study intra-abdominal infections. Experimental intra-abdominal infections. Experimental intra-abdominal infection is a bi-phasic process; initially a peritonitis or septic phace caused by E. coli and later a chronic-abscess forming stage, caused by B. fragilis similar to human beings. Various methods have been described. These methods includes challenge of the peritoneum with either endogenous bacteria or inoculation of pure bacteria or fectal material. Non-bacterial models have also been described. Each of these models have their own advantages and disadvantages. The aim and the end points should govern the selection of the right model to be used for experimental purposes. The ideal model should be reliable, standard, reproducible and resembling human disease. A single model with those specifications is yet to be described.     

Respiratory syncytial virus infection in north-east England

During a period covering four winter epidemics 987 respiratory syncytial (RS) virus infections were identified in the children's wards that served a total population of about 875 000 in north-east England. The incidence of admission to hospital with RS virus infection tended to be twice as high among children in Tyneside as that among children from the rest of the catchment area. The risk of hospital admission with RS virus infection in the first year of life for city children was about 1 in 50. The risk tended to be increased when there was a high proportion of children in the population, overcrowded housing, and unemployment. There was no clear relation between climatic changes and the onset or progress of epidemics. Thirteen deaths associated with RS virus infection were identified, four of them sudden and unexpected at home, and nine of them in children with congenital or acquired abnormalities. Twelve children were admitted twice with distinct RS virus infections; the relative severity of their two illnesses depended on age. Hospital cross-infection accounted for 60 of the 987 illnesses. Large families and overcrowding among poorer families seem to lead to a higher incidence of RS virus infection, and measures to reduce overcrowding and improve housing should help to reduce the spread of infection. Breast-feeding also protects infants from infection, but further information is needed to pinpoint the infants at greater risk and how they may best be protected.     

Respiratory syncytial virus infection in older persons

Respiratory Syncytial Virus (RSV) is an increasingly recognized cause of serious disease in older adults. RSV causes excess morbidity and mortality in older persons residing in nursing homes and in the community. The study of RSV in adults has been hampered by the lack of sensitive methods for the diagnosis of acute infections. Such tools are needed to better understand the epidemiology and immunology of RSV in adults. The immune status of older adults has begun to be explored and preliminary data indicates that low serum neutralizing antibody may predispose to symptomatic RSV infection and that a greater diversity of antibody titres may be seen in the elderly compared to young adults. PFP-2, a candidate RSV subunit vaccine, has been evaluated in healthy and institutionalized elderly and been found to be safe and immunogenic.     

Phosphoprotein profile analysis of ruminant respiratory syncytial virus isolates

OBJECTIVE: To determine the apparent molecular weight for 24 ruminant respiratory syncytial viruses (RSV) on the basis of differences in the electrophoretic mobility of the phosphoprotein (P protein). PROCEDURE: 29 bovine RSV (BRSV), 20 of which were not previously tested, 3 ovine RSV, and 1 caprine RSV isolates were selected for determination of electrophoretic mobility of the P protein. Virus radiolabeled with [35S]methionine was immunoprecipitated with polyclonal antiserum to BRSV and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. RESULTS: On the basis of apparent molecular size of the P protein, all isolates could be categorized into 2 electropherotypes, low molecular size of 36 kd and high molecular size of 38 kd. Twenty-three BRSV, the 3 ovine RSV, and 1 caprine RSV isolates had a high molecular size P protein; 6 BRSV isolates had a low molecular size P protein. CONCLUSIONS: The apparent molecular size of the P protein of the ruminant RSV strains is greater than that of the human RSV subgroups, providing further evidence of their distinctiveness. Whether categorization of electrophoretic mobility of the P protein of BRSV underlies distinct antigenic subgroups, as it does in human RSV, requires further antigenic and genetic analysis. CLINICAL RELEVANCE: Antigenic subgroups of ruminant RSV may have relevance in the development of new vaccines for control of the disease.     

Antigenic structure of human respiratory syncytial virus fusion glycoprotein

New series of escape mutants of human respiratory syncytial virus were prepared with monoclonal antibodies specific for the fusion (F) protein. Sequence changes selected in the escape mutants identified two new antigenic sites (V and VI) recognized by neutralizing antibodies and a group-specific site (I) in the F1 chain of the F molecule. The new epitopes, and previously identified antigenic sites, were incorporated into a refined prediction of secondary-structure motifs to generate a detailed antigenic map of the F glycoprotein.     

Inactivation of respiratory syncytial virus by detergents and disinfectants

The activity of a number of detergents and disinfectants against respiratory syncytial virus (RSV) was evaluated in an in vitro assay system. Equal volumes of RSV and serial 10-fold dilutions of the test agents were mixed at 4 degrees C for 5 minutes. The RSV titer in each mixture was compared with that of untreated RSV alone. In 14 experiments with input RSV titers ranging from 2.6 x 10(3) to 2 x 10(7) plaque-forming units/ml, a 10-fold dilution of 5.25% sodium hypochlorite (generic bleach) inactivated (> or = 3-log reduction in titer) the virus. With lower RSV titers inactivation was also observed at a 100-fold dilution of bleach. Fetal calf serum concentrations up to 50% as an organic load did not diminish the bleach effect. The degree of RSV inactivation was also defined for Lysol, povidone-iodine, Amphyl, Hibiclens, Osyl, ethanol and Listermint. The short contact time, the reproducible nature of the findings and the continued effectiveness with increasing organic loads all suggest that detergents and disinfectants can potentially play an important role in decreasing the spread of RSV infection.     

CD8+ T cells control Th2-driven pathology during pulmonary respiratory syncytial virus infection

BALB/c mice vaccinated with vaccinia virus expressing the major surface glycoprotein G of respiratory syncytial virus (RSV) develop lung eosinophilia during RSV challenge. The G protein is remarkable in that it induces CD4+, but no CD8+ T cells in this mouse strain. Studies using passive T cell transfers show that co-injection of CD8+ T cells greatly reduces the Th2-driven lung eosinophilia caused by G-specific CD4+ T cells. By contrast, vaccination with the fusion protein (F) induces both CD8+ and CD4+ T cells, but not lung eosinophilia during RSV infection. These observations suggest that CD8+ T cells play a crucial role in preventing Th2-driven pathology. We therefore depleted mice with anti-CD8 antibodies in vivo. This treatment allowed lung eosinophilia to develop in F-primed mice. Depletion of interferon (IFN)-gamma had a similar effect, suggesting that secretion of this cytokine is the mechanism by which CD8+ T cells exert their effect. To test whether similar effects occurred in other strains of mice, RSV-infected C57BL/6 mice (which do not develop eosinophilia after sensitization to G) were treated with anti-IFN-gamma. Again, these mice developed eosinophilia. In this strain, genetic deletion of CD8-alpha, beta2-microglobulin or genes coding for the transporter associated with antigen presentation (which in each case eliminates CD8+ T cells) caused lung eosinophilia during RSV infection. These studies show the critical roles that CD8+ T cells and IFN-gamma production play in regulating Th2-driven eosinophilia and provide a unifying explanation for previous studies of lung eosinophilia. We propose that vaccines designed to enhance CD8+ T cell recognition might avoid disease caused by CD4+ Th2 cells.     

Long term follow-up of children hospitalized with respiratory syncytial virus lower respiratory tract infection and randomly treated with ribavirin or placebo

PURPOSE: To determine how many cases of breast cancer might be found if women not known to have the disease were thoroughly examined (the disease "reservoir"). DATA SOURCES: MEDLINE search from 1966 to the present. STUDY SELECTION: Hospital-based and forensic autopsy series examining women not known to have had breast cancer during life. DATA EXTRACTION: Observed prevalence of occult invasive breast cancer or ductal carcinoma in situ (DCIS) in which the number of women who were given a diagnosis was the numerator and the number of women examined was the denominator. For each autopsy series, we attempted to ascertain the level of scrutiny (sampling method, number of slides examined) given to the pathologic specimens. DATA SYNTHESIS: Among seven autopsy series of women not known to have had breast cancer during life, the median prevalence of invasive breast cancer was 1.3% (range, 0% to 1.8%) and the median prevalence of DCIS was 8.9% (range, 0% to 14.7%). Prevalences were higher among women likely to have been screened (that is, women 40 to 70 years of age). The mean number of slides examined per breast ranged from 9 to 275; series that reported higher levels of scrutiny tended to discover more cases of cancer. CONCLUSIONS: A substantial reservoir of DCIS is undetected during life. How hard pathologists look for the disease and, perhaps, their threshold for making the diagnosis are potentially important factors in determining how many cases of DCIS are diagnosed. The latter has important implications for what it means to have the disease.     

Detection of antibody to respiratory syncytial virus by membrane fluorescence

An indirect membrane fluorescent antibody technique was established to study HEp 2 cells infected with respiratory syncytial (RS) virus. It was possible to detect IgG and IgM antibody to RS virus in the sera of patients with respiratory infections using this technique. The technique was further applied to the detection of IgA antibody to the same virus in colostrum.     

A bovine model of vaccine enhanced respiratory syncytial virus pathophysiology

A critical issue has been the observation that vaccination of children with a formalin-inactivated respiratory syncytial virus (RSV) vaccine is associated with disease enhancement. We have taken advantage of bovine RSV and our experience with this disease in calves to develop a natural model that parallels human disease. Using formalin-inactivated bovine RSV vaccine calves were either sham-vaccinated/infected, vaccinated/infected, or vaccinated/sham-infected and their clinical signs, pulmonary function, and histological lung lesions quantitatively scored. Interestingly there was significantly greater disease in vaccinated/infected calves and histological lesions in calves were similar to those of affected children. Finally, we note that vaccination did not induce neutralizing antibodies, but IgG antibodies were detected by ELISA. Our model of RSV enhanced disease is important because it provides quantifiable evidence of disease severity that can be applied to evaluate the mechanisms of immunopathology and the safety of candidate RSV vaccines.