Vaccine prevention of acute otitis media

The incidence of acute otitis media (AOM) in infants and young children has increased dramatically in recent years in the United States. AOM often follows upper respiratory tract infections due to pathogens such as respiratory syncytial virus (RSV), influenza virus, and parainfluenza virus (PIV). These viruses cause eustachian tube dysfunction that is critical to the pathogenesis of AOM. Vaccines against these viruses would likely reduce the incidence of AOM. In three previous studies, influenza virus vaccines reduced the incidence of AOM by 30% to 36%. Vaccines to prevent infections with RSV and PIV type 3 are undergoing clinical testing at this time. Streptococcus pneumoniae, nontypeable Haemophilus influenzae (NTHi), and Moraxella catarrhalis are the three most common AOM pathogens. Heptavalent pneumococcal conjugate vaccine is effective in preventing invasive disease and AOM caused by serotypes contained in the vaccine. Vaccine candidates for NTHi and M. catarrhalis are under development.

The role of viruses in the induction and progression of asthma

Viral respiratory infections have been related to asthma in several ways. It is well established that viral common colds precipitate exacerbations of asthma. Severe bronchiolitis in early life is related to subsequent wheezing and therefore may represent a marker of susceptibility to asthma; alternatively, it could be involved in the initiation of the disease. Finally, it is possible that some infections may protect from the development of asthma and allergies by promoting a type-1 host response. However, whether respiratory or other viruses could mediate such a protective effect is debated. The design and implementation of novel anti- or proviral strategies targeting asthma depends on the resolution of these questions. This review presents current evidence on the epidemiologic correlations and proposed mechanisms for the involvement of viral infections in the development and progression of asthma.

Gene expression in epithelial cells in response to pneumovirus infection

Respiratory syncytial virus (RSV) and pneumonia virus of mice (PVM) are viruses of the family Paramyxoviridae, subfamily pneumovirus, which cause clinically important respiratory infections in humans and rodents, respectively. The respiratory epithelial target cells respond to viral infection with specific alterations in gene expression, including production of chemoattractant cytokines, adhesion molecules, elements that are related to the apoptosis response, and others that remain incompletely understood. Here we review our current understanding of these mucosal responses and discuss several genomic approaches, including differential display reverse transcription-polymerase chain reaction (PCR) and gene array strategies, that will permit us to unravel the nature of these responses in a more complete and systematic manner.

Predominant type-2 response in infants with respiratory syncytial virus (RSV) infection demonstrated by cytokine flow cytometry

Acute RSV infection in infancy may produce some asthma-like symptoms and may be followed by a recurrent wheeze later in childhood. It has been proposed that RSV infection stimulates type-2 cytokine responses, resembling those found in atopy and asthma. Peripheral blood cells were obtained from RSV-infected infants (n = 30) and healthy controls (n = 10). After in vitro restimulation of the cells, intracellular IL-4 and interferon-gamma (IFN-gamma) were measured by flow cytometry. The cells from RSV-infected infants produced more IL-4 and less IFN-gamma than those from healthy controls. IL-4 production was more frequent in CD8 than in CD4 cells, and the bias toward IL-4 production was greatest in infants with mild infections, whereas IFN-gamma production increased with disease severity. Our conclusions are that RSV infection is associated with IL-4 production in peripheral T cells, and that peripheral blood in infants with severe disease may be depleted of cytokine-producing cells.

Viral-Bacterial Synergy in Otitis Media: Implications for Management

Despite the extensive use of broad-spectrum antibiotics, poor clinical response to the treatment of acute otitis media is common. Evidence derived from numerous studies during the past two decades supports a crucial role for respiratory viruses in the etiology and pathogenesis of acute otitis media, and recent studies indicate that viruses may also have a profound adverse effect on the resolution of this disease. Viruses seem to interact with bacteria and enhance the local inflammatory process in the middle ear. Effective adjuvant therapies are needed to improve outcome in children with otitis media. Increasing knowledge of the role of viruses, viral-bacterial interaction, and host inflammatory mechanisms in otitis media may lead to major improvements in the management of this disease.

Detection of viral, Chlamydia pneumoniae and Mycoplasma pneumoniae infections in exacerbations of asthma in children

BACKGROUND

A high frequency of virus infections has been recently pointed out in the exacerbations of asthma in children.

OBJECTIVES

To confirm this, using conventional and molecular detection methods, and expanding the study to younger children.

STUDY DESIGN

One hundred and thirty-two nasal aspirates from 75 children hospitalized for a severe attack of asthma were studied (32 infants, mean age 9.1 months; and 43 children, mean age 5.6 years). According to the virus, a viral isolation technique, immunofluorescence assays (IFA) or both were used for the detection of rhinovirus, enterovirus, respiratory syncytial (RS) virus, adenovirus, coronavirus 229E, influenza and parainfluenza virus. Polymerase chain reaction (PCR) assays were used for the detection of rhinovirus, enterovirus, RS virus, adenovirus, coronavirus 229E and OC43, Chlamydia pneumoniae and Mycoplasma pneumoniae.

RESULTS

Using IFA and viral isolation techniques, viruses were detected in 33.3% of cases, and by PCR techniques, nucleic acid sequences of virus, Chlamydia pneumoniae and Mycoplasma pneumoniae were obtained in 71.9% of cases. The combination of conventional and molecular techniques detects 81.8% of positive samples. Two organisms were identified in the same nasal sample in 20.4% of the cases. The percentage of detections was higher (85.9%) in the younger group than in the other (77%). The most frequently detected agents were rhinovirus (46.9%) and RS virus (21.2%). Using PCR rather than conventional techniques, the detection rates were increased 5.8- and 1.6-fold in rhinovirus and RS virus infections, respectively. The detection levels of the other organisms are as follows: 9.8, 5.1, 4.5, 4.5, 4.5, 3.7, and 2.2% for enterovirus, influenza virus, Chlamydia pneumoniae, adenovirus, coronavirus, parainfluenza virus, and Mycoplasma pneumoniae, respectively.

CONCLUSION

These results confirm the previously reported high frequency of rhinovirus detection in asthmatic exacerbations in children. They also point out the frequency of RS virus detection, and emphasize the fact that PCR assays may be necessary to diagnose respiratory infections in asthma.

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

We wished to retrospectively evaluate the effects of permissive hypercapnia (PHY) on barotrauma, mortality and length of stay when applied to ventilated infants with respiratory syncytial virus (RSV) bronchiolitis. Nineteen control infants with RSV induced respiratory failure were treated with conventional ventilation (April 1991-January 1994), after which time PHY was adopted as unit policy. A further 28 infants were then treated with PHY (January 1994 April 1996). Demographic and physiological data were collected from admission, and outcome variables including length of stay, barotrauma and mortality were recorded. The PHY group showed a significantly higher mean pCO2 (7.6 vs 5.2 kPa), a lower mean pH (7.34 vs 7.40), and a reduction in maximal peak inspiratory pressures (25 vs 30 cmH2O). Mortality, barotrauma, use of neuromuscular blockade and nosocomial infection did not differ between groups. There was a trend towards increased length of ventilation in the PHY group (median 7 vs 5 days).

CONCLUSION

Based on this retrospective data we can show no benefit for the use of permissive hypercapnia as a ventilatory strategy in this patient group. A prospective randomised controlled trial is warranted to accurately assess the outcome variables and cost implications of this strategy.

Atypical pulmonary eosinophilia is mediated by a specific amino acid sequence of the attachment (G) protein of respiratory syncytial virus

We analyzed the immune responses evoked by a series of overlapping peptides to better understand the molecular basis for respiratory syncytial virus (RSV) G protein-induced eosinophilia in BALB/c mice. In vitro stimulation of spleen cells from natural G protein-primed mice showed dominant proliferative and cytokine (interferon [IFN]-gamma and interleukin [IL]-5) responses to a peptide encompassing amino acids 184-198. Mice vaccinated with peptide 184- 198 conjugated to keyhole limpet hemocyanin showed significant pulmonary eosinophilia (39.5%) after challenge with live RSV. In contrast, mice immunized with a peptide (208-222) conjugate associated with induction of IFN-gamma secreting spleen cells did not exhibit pulmonary eosinophilia after challenge. The in vivo depletion of CD4(+) cells abrogated pulmonary eosinophilia in mice vaccinated with the peptide 184-198 conjugate, whereas the depletion of CD8(+) cells had a negligible effect. Therefore, we have identified an association between peptide 184- 198 of natural G protein and the CD4(+) T cell-mediated induction of pulmonary eosinophilia after live RSV challenge. Out of 43 human donors, 6 provided peripheral blood mononuclear cells that showed reactivity to G protein from RSV A2, 3 of which responded to peptide 184- 198. The results have important implications for the development of a vaccine against RSV.

The apoptosis of neutrophils is accelerated in respiratory syncytial virus (RSV)-induced bronchiolitis

Neutrophils are the predominant inflammatory cell in the lung tissues and airways in RSV infection, and can augment the epithelial cell damage induced by RSV. Neutrophil apoptosis has been suggested to be a mechanism to reduce the potential for tissue injury. The apoptosis of neutrophils from nasopharyngeal aspirates (NPA) (n = 19) and peripheral blood (PB) of infants with RSV bronchiolitis (n = 11) and PB from healthy controls (n = 9) was investigated. Monoclonal antibody against CD95 (Fas) and a binding protein Annexin V were used to determine the apoptosis of neutrophils. The expression of CD11b and CD18 on neutrophils was also detected with flow cytometry. The mean fluorescence intensity (MFI) of CD95 on neutrophils from RSV+ NPA was increased compared with cells from control PB (73.6 +/- 7.6 versus 31.5 +/- 4.3); the MFI of Annexin V, CD11b and CD18 on neutrophils from RSV+ NPA was up-regulated compared with cells from both control PB (105.3 +/- 18.1 versus 11.8 +/- 1.5; 1683 +/- 153.3 versus 841.1 +/- 72.3; 517 +/- 50.5 versus 147 +/- 8.7, respectively) and RSV+ PB (105.3 +/- 18.1 versus 35.8 +/- 4.1; 1683 +/- 153.3 versus 818 +/- 141.2; 517 +/- 50.5 versus 260 +/- 25.8, respectively). Furthermore, the percentage of neutrophils expressing Annexin V and the MFI of CD18 on neutrophils from RSV+ PB were increased compared with neutrophils from control PB. In addition, both CD11b (MFI) and CD18 (MFI) correlated with Annexin V (MFI) on neutrophils. We conclude that neutrophil apoptosis in RSV bronchiolitis is accelerated; and CD11b/CD18 may play an important role in RSV infection by influencing neutrophil apoptosis.

Increased number of T cells committed to IL-5 production after respiratory syncytial virus (RSV) infection of human mononuclear cells in vitro

We examined changes in the cytokine profile of T cells induced by in vitro infection with RSV. Isolated mononuclear cells from 27 healthy adults and six infants were infected with RSV at a concentration of 3 MOI (multiplicity of infection). After 48 h cells were restimulated with phorbol ester and ionomycin in the presence of monensin for 5 h. The intracellular expression of viral antigen, the cytokines IL-2, IL-4, IL-5, interferon-gamma (IFN-gamma), and the expression of surface markers were assessed by immunofluorescent staining and flow cytometry. There was a significant (P<0.001) rise of IL-5 expression in RSV-infected cultures in comparison with uninfected cultures from the same individuals, whereas there were no changes in the expression of the other lymphokines. The increase in IL-5 generation depended on viable infectious RSV rather than inactivated virus. RSV infection as well as IL-5 production in T cells were confined to the CD8 subpopulation. However, there was no simultaneous expression of RSV antigen and IL-5. Purified T cells did not show any increase in IL-5 generation. However, when the rate of RSV infection was enhanced in monocytes by means of a specific monoclonal antibody, co-cultured T cells displayed an increase of IL-5 production compared with samples with ordinary low rate RSV infection. It is therefore likely that the increased commitment of lymphocytes to produce IL-5 after RSV infection in vitro is mediated by monocytes or other antigen-presenting cells.

Protection against respiratory syncytial virus infection by DNA immunization

Respiratory syncytial virus (RSV) remains a major cause of morbidity and mortality in infants and the elderly and is a continuing challenge for vaccine development. A murine T helper cell (Th) type 2 response associates with enhanced lung pathology, which has been observed in past infant trials using formalin-inactivated RSV vaccine. In this study, we have engineered an optimized plasmid DNA vector expressing the RSV fusion (F) protein (DNA-F). DNA-F was as effective as live RSV in mice at inducing neutralizing antibody and cytotoxic T lymphocyte responses, protection against infection, and high mRNA expression of lung interferon gamma after viral challenge. Furthermore, a DNA-F boost could switch a preestablished anti-RSV Th2 response towards a Th1 response. Critical elements for the optimization of the plasmid constructs included expression of a secretory form of the F protein and the presence of the rabbit beta-globin intron II sequence upstream of the F-encoding sequence. In addition, anti-F systemic immune response profile could be modulated by the route of DNA-F delivery: intramuscular immunization resulted in balanced responses, whereas intradermal immunization resulted in a Th2 type of response. Thus, DNA-F immunization may provide a novel and promising RSV vaccination strategy.

The immunostimulating complex (ISCOM) is an efficient mucosal delivery system for respiratory syncytial virus (RSV) envelope antigens inducing high local and systemic antibody responses

ISCOM is an efficient mucosal delivery system for RSV envelope proteins as measured by antibody responses in respiratory tract secretions and in sera of mice following two intranasal (i.n.) administrations. Intranasally administered RSV ISCOMs induced high levels of IgA antibodies both in the upper respiratory tract and in the lungs. In the lungs, a prominent and long-lasting IgA response was recorded, which still persisted 22 weeks after the second i.n. immunization when the experiment ended. Subcutaneous (s.c.) immunization only induced low IgA titres in the upper respiratory tract and no measurable response to RSV was found in the lungs. Differences were also noticed in serum between the i.n. and s.c. modes of immunization. ISCOMs given intranasally induced earlier, higher and longer lasting IgM and IgG1 serum anti-RSV antibody responses than those induced by the s.c. mode of administration. A low serum IgE response was only detectable at 2 weeks after i.n. immunization with ISCOMs and after s.c. immunization with an inactivated virus, but no IgE response was detectable after s.c. injection of ISCOMs. The serum IgA response was more pronounced following s.c. injection of inactivated virus than after i.n. application of ISCOMs, and a clear-cut booster effect was obtained with a second immunization. Virtually no serum IgA response was detected after the s.c. administration of ISCOMs. In conclusion, the high immune responses induced by RSV ISCOMs in the respiratory tract and serum after i.n. administration indicate prominent mucosal delivery and adjuvant properties of the ISCOMs, warranting further studies.

Eliminating a region of respiratory syncytial virus attachment protein allows induction of protective immunity without vaccine-enhanced lung eosinophilia

In a murine model of respiratory syncytial virus disease, prior sensitization to the attachment glycoprotein (G) leads to pulmonary eosinophilia and enhanced illness. Three different approaches were taken to dissect the region of G responsible for enhanced disease and protection against challenge. First, mutant viruses, containing frameshifts that altered the COOH terminus of the G protein, were used to challenge mice sensitized by scarification with recombinant vaccinia virus (rVV) expressing wild-type G. Second, cDNA expressing these mutated G proteins were expressed by rVV and used to vaccinate mice before challenge with wild-type respiratory syncytial virus (RSV). These studies identified residues 193-205 to be responsible for G-induced weight loss and lung eosinophilia and showed that this region was not was not necessary for induction of protective immunity. Third, mice were sensitized using an rVV that expressed only amino acids 124-203 of the G protein. Upon RSV challenge, mice sensitized with this rVV developed enhanced weight loss and eosinophilia. This is the first time that a region within RSV (amino acids 193-203) has been shown to be responsible for induction of lung eosinophilia and disease enhancement. Moreover, we now show that it is possible to induce protective immunity with an altered G protein without inducing a pathological response.

Improved oxygenation after discontinuing neuromuscular blockade

OBJECTIVE

To evaluate the effects of prolonged neuromuscular blockade (NMB) on oxygenation and duration of mechanical ventilation in children with respiratory failure.

DESIGN

Retrospective case control study.

SETTING

The pediatric intensive care unit (PICU) of a tertiary university hospital.

PATIENTS

All children (n = 68) in the PICU ventilated for pulmonary parenchymal disease for 3 days or longer over a 4 1/2 year period.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Diagnoses, pediatric risk of mortality scoring, indications for, and duration of, mechanical ventilation and neuromuscular blockade, and blood gas data with corresponding ventilator parameters were extracted from the medical records. Twenty-eight patients received NMB at the initiation of mechanical ventilation and this was continued for 72 h or longer. Cessation of NMB was associated with a significant improvement in ventilator parameters and oxygenation index. The subset of children with respiratory syncytial virus disease (RSV) receiving prolonged NMB had longer ventilator courses compared to those in whom NMB was not used, despite similar demographics, severity of illness and oxygenation impairment.

CONCLUSIONS

Stopping NMB is associated with a rapid improvement in oxygenation and prolonged use of NMB in children with RSV is associated with a protracted ventilatory course.

DEFINITION

Oxygenation index (OI)*: Mean Airway Pressure x FiO2 x 100/PaO2* Higher scores represent deterioration in oxygenation.

Respiratory syncytial virus-induced cytokine production by neonatal macrophages

The induction of immunoregulatory cytokines IL-1 beta, IL-6, IL-12, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) was studied with neonatal (cord blood) monocyte-derived macrophages (MDM) after in vitro infection with respiratory syncytial virus (RSV). The expression of mRNAs for these cytokines in RSV-infected MDM was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The activities of these cytokines were assayed by ELISA. Significant increase of expression of mRNA for IL-6, IL-12, TNF-alpha and IFN-gamma occurred within 2 h after infection and decreased within 6 h after infection. At 20 h after infection the MDM produced and secreted moderate levels of IL-6 and TNF-alpha; however, no IL-12 and IFN-gamma activities were detected. Moderate IL-1 beta mRNA was expressed before RSV infection, and its expression increased at 2 h after infection. However, no detectable IL-1 beta was secreted in culture fluids. These observations suggest that RSV-infected neonatal macrophages produce and secrete IL-6 and TNF-alpha quickly during the eclipse phase of RSV infection and therefore may play a prominent role in the initiation of the immune response to RSV.

A model for respiratory syncytial virus (RSV) infection based on experimental aerosol exposure with bovine RSV in calves

Five conventionally kept calves aged between 17 and 24 days were experimentally infected with bovine respiratory syncytial virus (BRSV) by aerosol in order to mimic the natural infection route. The calves were killed and autopsies performed 7 days after the first virus challenge. The BRSV isolate used induced tracheitis, bronchitis and atelectasis in infected calves. The only virus which could be isolated from the lungs of the calves was BRSV. In addition, Mycoplasma bovirhinis was isolated from the lungs or/and trachea of two calves. The clinical and histopathological findings, as well as the detection of BRSV antigens by immunofluorescence in the epithelial cells of lung and trachea, and the reisolation of the virus from bronchoalveolar lavage fluids of all inoculated calves, provided confirmation of successful infection with BRSV.

Aetiology of community-acquired pneumonia in children treated in hospital

Viral and bacterial antigen and antibody assays were prospectively applied to study the microbial aetiology of community-acquired pneumonia in 195 hospitalised children during a surveillance period of 12 months. A viral infection alone was indicated in 37 (19%), a bacterial infection alone in 30 (15%) and a mixed viral-bacterial infection in 32 (16%) patients. Thus, 46% of the 69 patients with viral infection and 52% of the 62 patients with bacterial infection had a mixed viral and bacterial aetiology. Respiratory syncytial virus (RSV) was identified in 52 patients and Streptococcus pneumoniae in 41 patients. The next common agents in order were non-classified Haemophilus influenzae (17 cases), adenoviruses (10 cases) and Chlamydia species (8 cases). The diagnosis of an RSV infection was based on detecting viral antigen in nasopharyngeal secretions in 79% of the cases. Pneumococcal infections were in most cases identified by antibody assays; in 39% they were indicated by demonstrating pneumococcal antigen in acute phase serum. An alveolar infiltrate was present in 53 (27%) and an interstitial infiltrate in 108 (55%) of the 195 patients. The remaining 34 patients had probable pneumonia. C-reactive protein (CRP), erythrocyte sedimentation rate and total white blood cell count were elevated in 25%, 40% and 36% of the patients, respectively. CRP was more often elevated in patients with bacterial infection alone than in those with viral or mixed viral-bacterial infections. No other correlation was seen between the radiological or laboratory findings and serologically identified viral, bacterial or mixed viral-bacterial infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics and prognosis of hospital-treated obstructive bronchitis in children aged less than two years

In a prospective study 101 children aged less than 2 years (median age 10 months), were examined the first time they were admitted to a paediatric ward for asthmatic symptoms. Two-thirds were boys and 58 had parents or siblings with allergic symptoms. During winter-spring, respiratory syncytial (RS) virus was verified in 50% of children. Other viral agents were adenovirus, parainfluenza 3, coxsackie B 2, ECHO 6 and rotavirus. At the acute stage, 54% of the children displayed changes on pulmonary X-ray. The total IgE value was greater than or equal to +2 SD score units in 14 children. At reinvestigation after 3-4.5 years, when the children were aged 3.3-6.3 years, 53% were free from asthmatic symptoms; the median age for the last episode was 2 years. A total of 33% had mild asthma, 8% moderate and 6% severe asthma. The factors which correlated significantly with persistent asthma were: (1) The need for daily medication for at least 6 months. (2) A young age in conjunction with the first wheezing episode and on the first admission to a paediatric ward because of asthmatic symptoms. (3) Other past or present atopic symptoms. Heredity, tobacco smoking at home, having a furry pet, RS virus infection, or high total IgE at the time of the first admission did not correlate significantly with the persistence of asthma 3-4.5 years later. The results emphasize the good overall prognosis of wheezing in early childhood, even when the wheezing is severe enough to lead to inpatient treatment.

The effect of common bovine respiratory diseases on tidal breathing flow-volume loops

In order to better understand the bovine breathing pattern, tidal breathing flow-volume loops (TBFVL) were analyzed in 24 healthy cattle of different body weights (range: 37-660 kg) (Group A) and in 28 cattle suffering from the common respiratory diseases: verminous bronchitis (Group B); shipping fever (Group C); acute respiratory distress syndrome (Group D); respiratory syncytial virus pneumonia (Group E); organophosphate poisoning (Group F); and necrotic laryngitis (Group G). Respiratory airflow and tidal volume were measured with a breathing mask-Fleisch pneumotachograph assembly. TBFVL were traced from these values using a computerized method. All the loop indices proposed by Amis and Kurpershoek (1986a) were calculated from 5 representative breathing cycles for each of the 52 animals. The TBFVL shapes and indices were relatively constant in most healthy cattle and were not correlated with the body size. When compared to normal values, animals with moderate respiratory syndromes (Groups B and C) had a more flattened shape to their TBFVL. On the other hand, in most cattle with severe respiratory pathologies (Groups D, F and G expiration tended to be biphasic with the peak expiratory flow (PEF) occurring significantly later than in healthy animals. Both PEF and peak inspiratory flow were increased in all the pathological conditions. The TBFVL indices were more frequently and more severely changed during expiration than during inspiration.

Viral findings in children under the age of two years with expiratory difficulties

Viral findings were prospectively studied in lower respiratory tract infections in small children with and without expiratory difficulties. On first admission, a viral aetiology was found in 71 of 127 children (56%). On re-admission, a viral etiology was found in only two of 31 cases (6%). Respiratory syncytial viruses (RSV) were responsible for 71% of the cases with viral diagnoses. A recently-developed method for the direct detection of viral antigens in nasopharyngeal specimens by radio-immunoassay was more sensitive than complement fixation serology, especially in patients aged less than six months. Viral diagnosis was reached using this new method alone in 43% of infections caused by RSV and in 27% of infections caused by other viruses. In children under six months, RSV were found in 89% by direct antigen detection and in 22% by serology. We suggest that direct antigen detection should be used as the primary virological method in small children with lower respiratory tract infections. The aetiological agents were the same in cases with and without expiratory difficulties, RSV being found in about 40% of children in both instances. It is concluded that host factors are critical to the development of expiratory difficulties.

Bovine respiratory syncytial virus infection in an ontario cattle herd

Bovine respiratory syncytial virus was recovered from the lung of a six month old calf that died during an outbreak of respiratory disease in a cattle herd in Ontario. Lung tissue removed from the calf at necropsy, performed within two hours of death, was frozen at -70 degrees C prior to virus isolation attempts. Syncytia and intracytoplasmic inclusions were demonstrated both in histological sections of the calf's lung and in stained cell culture preparations infected with the bovine respiratory syncytial virus isolate. Direct fluorescent antibody and virus neutralization tests serologically confirmed the identity of the isolate.

Presumed respiratory syncytial virus pneumonia in three immunocompromised adults

Three cases of presumed respiratory syncytial virus (RSV) pneumonia in immunocompromised adults are described. Two patients had symptoms of cough, fever, and malaise, following completion of a course of combination chemotherapy for the treatment of acute lymphoblastic leukemia. The third patient, a juvenile onset diabetic, developed similar symptoms while hospitalized for severe hyperglycemia. Chest roentgenograms showed lower lobe infiltrates in both leukemic patients and a bilateral non-confluent bronchopneumonia in the diabetic patient. All patients had a marked rise in complement-fixing antibody titres to RSV, suggesting a concurrent infection with the virus. Extensive microbiological investigations failed to reveal any other etiologic agent. Nosocomial infection was considered possible. RSV is not considered a cause of pneumonia in compromised adults. Our three cases suggest that there may be a higher incidence of RSV pneumonia in compromised patients, than previously recognized.

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, IgG, 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 or 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, IgG, 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 8-33% 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.

Clones of cells from a human embryo lung: their growth and susceptibility to respiratory viruses

Colonies of cells were obtained from human fetal lung tissue and exposed to recently isolated respiratory viruses. There was a considerable variation in the number of rounded cells found in different colonies exposed to rhinovirus types 2 and 9 (RV2 and 9), human coronavirus 229E (HCV), adenovirus type 3 (Ad3) and respiratory syncytial virus (RSV). Smaller colonies had more rounded cells than larger colonies. Clones were established from 9 out of 11 colonies. They varied in their rate of growth and the pattern formed on a plastic surface. They varied also in their virus susceptibility particularly to "difficult" rhinoviruses such as RV9 and SF1340. One cell clone (HL1/77 Clone 8), was highly susceptible to all these viruses. All cultures were more sensitive to RSV when maintained in F12K medium than in MEM, whereas there was no difference for rhinoviruses. Influenza A and B and parainfluenza 3 viruses sometimes produced cytopathic effect, and always produced haemadsorption, but unlike the previous strains could not be passed serially and presumably produced little infectious virus. All clones were rather insusceptible to Ad3; but the virus could be passed, whereas coxsackie virus B3 produced no CPE. Substantial yields of coronavirus and rhinovirus were obtained in gelatin sponge cultures. Two "very difficult" respiratory viruses which had just been adapted to tissue culture; namely, HS rhinovirus and JK coronavirus grew in 7 of 9 and in 6 of 9 clones respectively.

Bovine respiratory syncytial virus infection of bovine embryonic lung cultures: enhancement of infectivity with diethylaminoethyl-dextran and virus-infected cells

The effects of incorporating diethylaminoethyl-dextran (DEAE-D) in the inoculum with bovine respiratory syncytial virus (BRSV) on the infectivity of BRSV was evaluated. A concentration of 40 microgram DEAE-D/ml provided maximal enhancement of infection as determined by the time of onset of cytopathic effect (CPE), the percentage of cells infected by the inoculum, and the amount of virus produced. When DEAE-D was used in the inoculum, the CPE appeared a day earlier, the percentage of cells infected by the inoculum, as determined by the fluorescent antibody test, was increased 11 times, and the viral titer was increased 2 times as compared to results obtained without DEAE-D. Bovine respiratory syncytial virus-infected cultures contained much cell-associated virus which could be liberated by sonication to increase the titer of virus stocks. The use of BRSV-infected cells rather than supernates from BRSV-infected cells increased the rate at which a cytopathic effect developed, although it did not substantially increase the titer of virus which was harvested. The use of DEAE-D in the inoculum and the passage of BRSV-infected cells instead of viral suspensions was found to be the quickest and most effective method of consistently obtaining BRSV with a titer of about 10(5.5) TCID50/ml.

The incidence and aetiology of respiratory tract infections in general practice--with emphasis on Mycoplasma pneumoniae

The incidence of respiratory tract infections in patients seeking medical advice at a community care centre (Dalby) during 1973 and 1974 was studied. About every third patient seen at this primary health station presented with signs of such infections. In the age groups less than 10, 10-19, 20-39, 40-59 and greater than or equal to 60 years, respiratory tract infections accounted for 65, 45, 32, 18 and 9% of the fotal number of diagnoses made during 1974. The aetiology of acute respiratory tract infections in a series of patients seen at this health station was studied. The series included randomly selected cases, but excluded children under seven years of age and patients presenting with signs of acute otitis media and tonsillitis. Attempts to establish the aetiology were made on the basis of the history, the clinical examination, and cultures for beta-haemolytic streptococci and Mycoplasma pneumoniae, complement foxation tests for influenza A and B, para-influenza 1, 2, and 3, adeno, cytomegalovirus and respiratory syncytial virus, and Chlamydia psittaci. Paul-Bunnell test and tests for cold agglutinins were also performed. With this test battery, an aetiological diagnosis was obtained in only 33% of the 101 patients studied. The findings suggest an infection with M.pneumoniae in 16%, with beta-haemolytic streptococci in 9%, and with viruses (adeno and para-influenza) in 7% of the patients. The present communication highlights the role of M.pneumoniae in upper respiratory infections, as few data have appeared on such infections in patients seen in general practice. The difficulty of establishing the aetiology of respiratory tract infections and the consequent treatment dilemma is discussed.

Attenuated respiratory syncytial virus vaccines in asthmatic children

Extract: Two live “attenuated” respiratory syncytial virus (RSV) vaccines were administered intranasally and by aerosol in placebo-controlled trials among asthmatic children hospitalized at National Jewish Hospital and Research Center (NJH). The first vaccine, a 26° -adapted RSV vaccine, was given to 28 children, and a placebo control was given to 25. Twenty-one of 28 vaccinees (75%) had “takes,” as judged by virus shedding and/or rises in serum antibody and/or rises in nasal secretion neutralizing activity. No excess in wheezing was attributable to the vaccine administration, although there was a high background level of acute respiratory symptoms in both vaccinees and control subjects. In an outbreak of natural RSV infection which occurred some months after the vaccine was given, there was some evidence that those who received the vaccine less than 4 months before exposure to wild virus were protected against reinfection. Protection was not evident when this interval was greater than 4 months. The second vaccine, a temperature-sensitive mutant strain (ts-1), was administered to 22 children, and placebo to 21. Thirteen children (59%) had “takes.” In vaccinees under 6 years of age, 7 of 7 had “takes.” Again, no excess wheezing was seen in vaccinees as compared with control subjects, although there was some evidence that upper respiratory symptoms were more frequent in younger vaccinees. Four of 10 vaccinees shed virus with temperature-sensitive characteristics somewhat different from those of the vaccine strain. Vaccine virus was demonstrated to spread to uninoculated or placebo control children. Natural RSV challenge did not occur during the period of study. Speculation: One of two live “attenuated” RSV vaccines may have produced a brief period of protection against natural infection. This finding offers hope that such live vaccines might prevent disease in selected children over a critical time period, such as infants for the 1st year of life, or allergic or asthmatic children during periods of epidemic prevalence. Asthmatic children did not appear to develop symptoms of wheezing after attenuated RSV infection. This finding suggests that the mechanism of wheezing in asthmatic children with RSV infection may be dependent on, among other factors, the virulence of the virus strain (perhaps its capacity to replicate in and, possibly, invade the lower respiratory tract), rather than on an allergic response to antigens introduced into, and limited to, the upper airway. In view of the spread of the ts-1 vaccine and its apparent loss of temperature sensitivity in some vaccinees, the vaccine may have had the potential for reversion to virulence and hence initiation of epidemic disease. These characteristics are undesirable in live respiratory virus vaccines and should, if possible, be avoided in the development of future such vaccines.

Epidemiology of respiratory syncytial virus infection among infants and children in Chicago

From January 1, 1967 to December 1971, the temporal pattern of respiratory syncytial virus infection was investigated in infants and children younger than 18 months hospitalized for acute lower respiratory tract disease. Of 4696 infants and children with acute lower respiratory tract disease admitted to the Cook County Hospital, 2530 were tested for virus infection by virus isolation or serologic procedures or both. Overall, respiratory syncytial virus infections were detected in 12% and parainfluenza 3 virus in 10.8% of individuals tested. Other respiratory viruses were less commonly identified. Respiratory syncytial virus epidemics occurred annually and were temporally synchronous with the peak periods of respiratory disease admissions. Only during epidemics of respiratory syncytial virus did admission for respiratory tract disease usually reach 40 patients or more weekly. The peak months of respiratory syncytial virus epidemics were December 1966, January 1968, February-March 1969, April 1970 and January 1971. Epidemics lasted about 17 weeks. No similar annual epidemic pattern was seen with the other myxoviruses.

Virus infections and the natural history of chronic obstructive lung disease

415 male out-patients were studied by serological means (complement-fixation with various viral antigens, hemagglutination-inhibition with adenoviruses of subgroup II). The conclusion was reached that the viruses investigated do not play a major role in the natural history of chronic obstructive lung disease. This is based on the following observations:

The rate of viral infections associated with respiratory disease or acute exacerbations of the bronchitis is low (see Tables 2 and 6).

Respiratory disease before the first examination is not caused by these viruses to any appreciable extent (see Table 3).

Antibody level in patients' sera against individual viruses or groups of viruses do not indicate protection against subsequent respiratory disease or against a deterioration of bronchial function (see Tables 4 and 5).