The development of respiratory syncytial virus-specific IgE and the release of histamine in nasopharyngeal secretions after infection

Rhinovirus upper respiratory infection increases airway hyperreactivity and late asthmatic reactions

Although viral upper respiratory infections (URIs) provoke wheezing in many asthma patients, the effect of these illnesses on the airway response to inhaled antigen is not established. The following study evaluated the effect of an experimental rhinovirus (RV) illness on airway reactivity and response to antigen in 10 adult ragweed allergic rhinitis patients. Preinfection studies included measurements of airway reactivity to histamine and ragweed antigen. Furthermore, the patients were also evaluated for late asthmatic reactions (LARs) to antigen (a 15% decrease in forced expiratory volume of the first second approximately 6 h after antigen challenge). 1 mo after baseline studies, the patients were intranasally inoculated with live RV16. All 10 patients were infected as evidenced by rhinovirus recovery in nasal washings and respiratory symptoms. Baseline FEV1 values were stable throughout the study. During the acute RV illness, there was a significant increase in airway reactivity to both histamine and ragweed antigen (P = 0.019 and 0.014, respectively). Before RV inoculation, only 1 of the 10 subjects had an LAR after antigen challenge. However, during the acute RV illness, 8 of 10 patients had an LAR (P less than 0.0085 compared with baseline); the development of LARs was independent of changes in airway reactivity and the intensity of the immediate response to antigen. Therefore, we found that not only does a RV respiratory tract illness enhance airway reactivity, but it also predisposes the allergic patient to develop LARs, which may be an important factor in virus-induced bronchial hyperresponsiveness.

The wheezing infant

In summary, wheezing is a common manifestation of viral respiratory tract disease in infancy. The precise pathogenetic mechanisms of virus-induced wheezing and its sequelae are not clear, although recent reports about participation of the cellular and humoral immune systems are promising. Although therapies like those used to treat asthma are employed in the treatment of virus-induced wheezing in infancy, their efficacy remains controversial in bronchiolitis. Recently developed agents with antiviral properties are promising and the choice of any of these agents in a therapeutic regimen should be individualized. Antiviral agents during acute infections may modify the long-term sequelae. Clearly, much work needs to be done to elucidate pathogenetic mechanisms, and to develop new, safe, and effective anti-inflammatory agents for the therapy of these disorders.

The contribution of viral respiratory infections to the pathogenesis of airway hyperreactivity

From this review, it is apparent that the effects of respiratory viral infection on airway reactivity are multiple. Although virus-associated changes are many, we have at present no evidence to show that respiratory viruses cause intrinsic abnormalities in airway smooth muscle function. Rather, respiratory viruses influence bronchial smooth muscle function through a variety of other means: epithelial injury, PMN-dependent inflammation, and greater mediator release. These observations suggest that a common pathway to development of airway hyperreactivity during respiratory viral illnesses is to enhance those factors which participate in the inflammatory response. When the target of this enhanced inflammatory response becomes the airway, greater bronchial reactivity and obstruction result. Although many questions remain to be answered, we feel that future studies to evaluate the biology of respiratory virus effects on mechanisms of airway responsiveness will lead to a greater understanding of asthma pathogenesis.

Upper airway inflammatory diseases and bronchial hyperresponsiveness

Inflammatory processes of the upper airway may alter the responsiveness of the lower airway. For example, bronchial hyperresponsiveness may be seen in patients with allergic rhinitis. This could represent coexistent but unrecognized asthma, but also suggests that IgE-dependent inflammation may occur in the lower airway that can increase bronchial hyperresponsiveness without at the same time precipitating obvious obstruction. Clearly, allergic rhinitis is a risk factor for asthma. A second example of the interaction of upper airway inflammation and bronchial hyperreactivity are reports that viral upper respiratory tract infections may cause otherwise healthy persons to respond abnormally to inhaled histamine or irritants for several months after the infections. These same viruses usually precipitate attacks in patients with asthma, who already have hyperresponsive airways. Both of these examples suggest that inflammatory processes occurring totally or primarily in the upper airway may participate in the pathogenesis of lower respiratory tract hyperresponsiveness and asthma.

Influence of atopy on the clinical manifestations of coronavirus infection in adult volunteers

In an attempt to understand the relationship between viral upper respiratory tract infection and the underlying virological and immunological mechanisms, thirty-four volunteers were inoculated intranasally with coronavirus 229E; subsequent virus shedding and/or antibody rises, indicating active infection, were observed in twenty-nine. There was a greater increase in independently measured scores of clinical severity, e.g. cold symptoms, in those with detectable IgE in nasal secretions (P less than 0.01). A similar association was found between clinical scores and serum IgE concentrations greater than or equal to 150 IU/ml, but the relationship with systemic atopy, as assessed by skin-prick tests to common allergens, was less marked. A more detailed study of twelve of the infected volunteers failed to explain these findings on the basis of mast cell mediator release, as concentrations of leukotriene B4, the sulphidopeptide leukotriene C4, and histamine, were not appreciably elevated in the nasal secretions following virus inoculation. Similarly, there was no evidence that circulating coronavirus specific IgE was produced. Thus, this study suggest that atopy may be related to the severity of cold symptoms produced by coronavirus 229E, although the exact connection has yet to be determined.

Release of leukotriene C4 in respiratory tract during acute viral infection

Groups of children with wheezing during respiratory illness, children without wheezing during respiratory illness, and appropriately matched healthy children were tested for the presence and concentration of leukotriene C4 (LTC4) in nasopharyngeal secretions, employing the techniques of reverse-phase high-pressure liquid chromatography and radioimmunoassay. Although most wheezing children had LTC4 in nasopharyngeal secretions, the concentration of LTC4 among wheezing children who shed respiratory viruses was found to be consistently elevated (mean 1520 +/- 228 pg/0.1 mL) compared with values in wheezing children without evidence of viral infection (mean 709 +/- 147 pg/0.1 mL). In sharp contrast, little or no LTC4 activity was detected in healthy children (mean 106 +/- 77 pg/0.1 mL). These observations suggest that respiratory viruses are stimuli for the release of mediators of inflammation such as LTC4. Thus development of virus-induced bronchospasm may be related in part to direct mucosal cell-virus interaction and the release of pharmacologically active mediators in the respiratory tract.

Detection, pathogenesis, and therapy of respiratory syncytial virus infections

Respiratory syncytial virus (RSV) infection is a major cause of serious lower respiratory disease in infancy and early childhood. The unique pathogenesis of lower respiratory illness due to RSV offers some intriguing clues to the role of the human immune system in both protection against and development of respiratory illness. More than any other virus, rapid diagnostic techniques have been especially successful in identifying RSV infection. Many of these techniques could be easily adaptable to diagnosis of influenza virus infection and other agents. Finally, ribavirin therapy of RSV infection represents one of the few instances in which antiviral therapy has been shown to be effective for respiratory illnesses. Fundamental observations in these areas in the case of RSV infection open up new and exciting pathways for investigation of respiratory infection due to other viral, chlamydial, and mycoplasmal agents.

Histamine concentrations in nasal secretion and secretory activity in allergic rhinitis

The prerequisites for using the assayed histamine concentration in nasal secretion as an objective measure of disease activity in allergic rhinitis were investigated. It was demonstrated that in histamine determination procedures the presence of quenching substances in the nasal secretion could lead to underestimation of the histamine concentration. This bias was eliminated in a modified spectrofluorometric assay. Only an insignificant fraction of the histamine in samples collected by nasal spray washing was bound to unfiltrable particles or cells. The mean histamine concentration in nasal secretions from 15 healthy subjects was 11.2 micrograms/ml and in a group of nine patients with allergic rhinitis out of season 3.36 micrograms/ml. The histamine concentration in the latter group decreased during the pollen season and after positive allergen challenge. It is suggested that this decrease is caused by the increase in volume of the secretion during the allergic response. The use of lithium as an exogenous marker permitted quantitation of the increase in the relative amount of nasal secretion recovered by washing in the symptomatic subjects.

Allergic predisposition among infants with bronchiolitis

Allergic predisposition among infants with bronchiolitis was examined. The number of infants with serum IgE exceeding mean +1 SD was 31/70 (44.3%). The rate of positive radioallergosorbent test (RAST) scores of 1 or more to mites, egg white, or milk was 31/71 (43.7%) and that of scores over 2 was 11/71 (15.5%). Eosinophils and/or mast cells were found in their nasal smears on several occasions. These results indicated that allergic predisposition may be observed among infants with bronchiolitis.

Total and specific IgE responses in the acute and recovery phases of respiratory infections in children

Total IgE and specific IgE antibodies to common allergens were determined by the enzyme-linked immunosorbent assay in children with Mycoplasma pneumoniae or respiratory syncytial virus (RSV) infections. The decrease of total IgE from the acute to convalescent phase was observed in 105 of 134 (78.4%) children with M. pneumoniae infection and in 40 of 49 (81.6%) of those with RSV infection. Similarly, many patients showed a decrease of the responses of specific IgE in the convalescent phase of the infections. The results indicated that these infections might alter the production of total IgE and IgE specific to common allergens unrelated to the infectious agents.

Predictive value of respiratory syncytial virus-specific IgE responses for recurrent wheezing following bronchiolitis

To determine whether the magnitude of the respiratory syncytial virus (RSV)-specific IgE response at the time of an episode of RSV bronchiolitis in infancy accurately predicts the development of subsequent wheezing episodes, we observed 38 infants prospectively from the time of an episode of infantile bronchiolitis through 48 months of age. Peak RSV-IgE titers were measured at the time of the bronchiolitis episode using an ELISA procedure. Notation was made of both the number of subsequent wheezing episodes reported by parents and the number documented by a physician. Subsequent wheezing was documented by a physician in 20% of infants who did not develop an RSV-IgE response at the time of the bronchiolitis episode and in 70% of those with the highest responses (P less than 0.025). These results suggest that the magnitude of the RSV-IgE response at the time of RSV bronchiolitis is a useful prognostic indicator for recurrent wheezing.

Ketotifen in the treatment of infants and young children with wheezy bronchitis and bronchial asthma

Ketotifen, an orally-administered anti-anaphylactic and antihistamine compound, was given in a dose of 0.06 mg/kg to 142 infants and young children presenting either with non-infected wheezy bronchitis or bronchial asthma to an allergy out-patient department. Treatment continued for 12 weeks. At the end of this time, ketotifen was considered to be very effective or effective in 70% of the children. The effect was more marked in non-infected wheezy bronchitis (83.55% response) than in bronchial asthma (56.5% response), perhaps because factors such as leukotrienes, prostaglandins and thromboxanes tend to produce a sustained bronchoconstriction in the latter condition. Ketotifen was not associated with any adverse effects and did not cause behavioural problems. Patients found it palatable and acceptable. The main disadvantage was that symptoms recurred within days of stopping treatment. Especially in non-infected wheezy bronchitis, ketotifen should be given for a year or longer to older children (older than 30 months) who have shown an initial good response to the drug.

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.

Kinetics of specific IgA, IgD, IgE, IgG, and IgM antibody responses in rubella

Rubella-specific IgD and IgE antibodies were determined with a solid-phase enzyme immunoassay using enzyme-labeled heavy-chain specific anti-immuno-globulins, and the antibody responses in rubella infection were compared to IgM, IgA, and IgG antibodies. IgD and IgE antibodies increased rapidly after the onset of infection, remained at a high level for at least 2 months, and declined slightly by 6 months. In comparison, the IgM antibodies decreased more rapidly, whereas the IgG antibodies persisted longer at a steady level. By 6 months the mean levels of the different antibodies had declined from their maximal mean levels as follows: IgM, 52%; IgA, 42%; IgE, 35%; IgD, 29%; and IgG, 8%. Thus IgD and IgE antibodies, in spite of their known short half lives, persisted longer than IgM and IgA antibodies, which limits their diagnostic value. The IgA antibody responses were found too variable to substitute for IgM antibody determination in diagnosis of a recent rubella virus infection from a single serum specimen. Comparison of maternal and cord blood sera indicated that, in addition to IgG antibodies, rubella-specific IgD antibodies were found to cross the placenta.

Quantitation of immunoglobulin E antibody to cytomegalovirus by antibody capture enzyme-linked immunosorbent assay

An antibody capture enzyme-linked immunosorbent assay was developed for detection of immunoglobulin E antibody to cytomegalovirus (CMV-IgE). Affinity-purified anti-human IgE-coated microtiter plates were used to separate IgE from other classes of antibody in serum. Virus-specific IgE was detected by subsequent incubation with horseradish peroxidase-labeled CMV antigen and substrate. The assay was shown to be very sensitive, since in most positive sera CMV-IgE was still detected at a dilution of 1:5,000. Of 45 patients with primary CMV infection, 43 (96%) were found to produce CMV-IgE. In contrast, CMV-IgE was detected in only 4 (9%) of 44 patients with recurrent CMV infection and in 1 of 144 healthy controls. Furthermore, the level of CMV-IgE in patients with recurrent CMV infection appeared to be lower than that in patients with primary infection. Preliminary examination of successive sera suggested that CMV-IgE is produced somewhat slower than CMV-IgM and -IgA but persists for a shorter period. These results suggest that CMV-IgE may be used as an indicator of primary CMV infection.

The wheezy child

Wheezing in association with viral respiratory tract infections occurs in 10-20% of all infants and young children and usually indicates hyperreactive bronchi. Signs of airway hyperreactivity can usually be demonstrated many years after the child has stopped wheezing. This hyperreactivity is partly constitutional, but it may be further aggravated by viral infections in the respiratory tract. Similarly, allergic inflammation or long-term exposure to airway irritants may also cause or aggravate a state of hyperreactivity which may be expressed as a proneness to asthmatic reactions. As viral infections are among the most potent asthma-provoking factors known, the hyperreactivity does not need to be very pronounced before wheezing develops in the infant or young child, with its small-calibred airway. As long as wheezing only occurs sporadically and only in association with viral respiratory tract infections, the prognosis is usually excellent. However, recommendations regarding avoidance of potent allergens and airway irritants in the daily environment should be given to such families. Such advice is especially important for families with a proneness to atopic reactions or if wheezing begins to occur even during infection-free periods.

Bronchodilator response during acute viral bronchiolitis in infancy

Bronchodilator responsiveness was assessed by measuring specific respiratory conductance before and after inhalation of aerosolized bronchodilator in 50 infants who had acute bronchiolitis due to respiratory syncytial virus infection. Thirty per cent of the infants showed an improvement in specific conductance. Responders could not be differentiated from nonresponders by family histories of atopy, eosinophil counts, or immunoglobulin levels in blood and nasal secretions. Eighty-three per cent of the families and 54% of the mothers of the infants were smokers. Babies of smoking mothers had lower specific conductances than did those of nonsmoking mothers but showed no differences in bronchodilator response. The clinical significance of this bronchodilator-responsive sub-group has yet to be defined.

Risk factors associated with the development of chronic lung disease in children

By better understanding the intrinsic and extrinsic factors that predispose children to chronic lung disease, strategies to prevent its development can be proposed. This article addresses conditions, such as bronchiolitis, croup, hyaline membrane disease, hydrocarbon ingestion, and near-drowning, that have been found to result in long-term changes in lung physiology. Also considered are the possible relationships of common respiratory infection, asthma, smoking, and air pollution to the development of chronic respiratory infection.

Respiratory virus infections and aeroallergens in acute bronchial asthma

Two hundred and fifty six attacks of acute bronchial asthma occurring in 169 children aged over 2 years were studied during a two year period. More attacks occurred during spring and autumn than at other times of the year. In 73 patients (29%) a respiratory virus infection was diagnosed, with the same seasonal variation as the asthmatic attacks. Most of the virus infections were caused by rhinovirus (45%) and respiratory syncytial virus (19%). There was no significant correlation between asthmatic attacks in patients with birch pollen, grass pollen, or Cladosporium herbarum allergy and counts of the respective pollen or spores in the air. More seasonal attacks occurred in patients with cladosporium allergy than in patients without cladosporium allergy but there was no seasonal variation among birch or grass pollen allergic patients. Information about exposure to animals was obtained in only 12% of attacks occurring in 121 patients with allergy to animal dander. The single precipitating factor most frequently associated with acute asthma was respiratory virus infection.

Symptoms, atopy, and bronchial reactivity after lower respiratory infection in infancy

We studied the prevalence of subsequent respiratory symptoms and the relation between atopic status and bronchial reactivity in 200 index children and their controls 7 years after acute lower respiratory tract infections in infancy. Index children with recurrent symptoms differed from controls in respect of social and family characteristics and atopic background. Ventilatory function was diminished and bronchial reactivity increased. Symptom free index children also came from poorer environmental backgrounds, but did not otherwise differ from controls. 'Atopic' index children differed significantly from controls in respect of subsequent symptoms and ventilatory function and similar adverse trends were observed in 'non-atopic' index children. A comparable proportion of 'atopic' and 'non-atopic' index children showed bronchial reactivity (33.5% and 38.9% respectively). Index subgroups with and without bronchial reactivity had increased cough and wheeziness compared with respective matched controls. The former included children with 'established' asthma and the latter those with 'established' bronchitis. Atopic backgrounds were similar in both subgroups, with no differences between cases and controls. These findings suggest that atopic background and bronchial reactivity are not closely related but may contribute independently to the persistence of symptoms after respiratory infections in infancy. Bronchial reactivity may be a more useful basis than atopic status on which to separate children with episodic cough or wheeze, or both, into 'asthmatic' and 'bronchitic' subgroups.

Current theories of the pathophysiology of asthma

Release of chemical mediators from sensitized mast cells is of established importance in allergic asthma and can account for most of the pathology and recognized changes in physiology. There is still uncertainty regarding specific modes of action of most of the drugs effective in the treatment of asthma. Changes in respiratory mucosal permeability induced directly or indirectly by viruses may initiate atopic sensitization in genetically predisposed subjects. Increased bronchial irritability accounts for much of the bronchoconstriction in both allergic and nonallergic asthma. Leukotrienes cause the bronchoconstriction in patients with aspirin sensitivity, but the factors that differentiate these patients from subjects who tolerate aspirin remain unknown. Asthmatics are characterized by a substantial increase in the number of alpha-adrenergic receptors and a more modest decrease in the number of beta-adrenergic receptors as well as increased sensitivity to cholinergic stimulation. Both mediator release and bronchial irritability may be important causes of exercise induced asthma.

Role of parainfluenza virus-specific IgE in pathogenesis of croup and wheezing subsequent to infection

In order to determine the role of parainfluenza virus-specific IgE antibody production and release of histamine in the pathogenesis of lower respiratory disease caused by parainfluenza virus infection, we studied 84 infants and children at the time of parainfluenza virus infection. Parainfluenza virus-IgE antibody was detected in samples of nasopharyngeal secretions by means of an enzyme-linked immunosorbent assay, and histamine content of nasopharyngeal secretions was determined by a fluorometric technique. Virus-specific IgE responses appeared earlier and were of greater magnitude in patients with croup, wheezing, and croup with wheezing caused by parainfluenza virus infection than in patients with parainfluenza virus-induced upper respiratory illness. Histamine was detectable in nasopharyngeal secretions of patients with parainfluenza virus-related croup significantly more often than in patients with upper respiratory illness caused by parainfluenza virus. These observations suggest a role for immunologic mechanisms in the pathogenesis of severe forms of respiratory illness caused by parainfluenza virus infection.

Natural history of parainfluenza virus infection in childhood

In order to determine the natural history of parainfluenza virus infection in early life, we followed prospectively 130 infants and children from birth or a few months of age for evidence of infection with PV. Using rapid diagnostic techniques, standard tissue culture infectivity, and serologic techniques we were able to document primary PV infection in 92% of these infants, and repeated infection with heterotypic or homotypic PV strains in 49% by 30 months of age. Increasing patient age had no significant effect in reducing the incidence of lower respiratory tract illness as a result of PV infection. Infection with one PV serotype provided no protection against LRTI at the time of subsequent infection with a heterotypic PV strain. In contrast, primary PV infection provided a brief period of immunity to LRTI upon homotypic reinfection. Secretory IgA responses to PV were determined by immunofluorescent techniques. Antibody response to PV strains causing primary infection and heterotypic repeated infection were transient and of low magnitude. Homotypic reinfection resulted in significantly enhanced production of secretory antibody to PV. At least in early life, repeated exposures to PV appear to be essential for maintaining immunity to severe forms of illness caused by PV infection.

Outcome of acute lower respiratory tract infection in infants: preliminary report of seven-year follow-up study

Seven years after admission to hospital for acute lower respiratory tract infection in infancy 200 children and their matched controls were assessed for respiratory state and epidemiological characteristics. The index group comprised 100 cases where respiratory syncytial virus infection had been responsible for the index illness (group 1) and 100 cases in whom this organism had not been found (group 2). There were no differences between index and control groups in birth weight or gestational age but fewer index cases were breast fed. Social indices such as class distribution and family size were more favourable in controls, though housing standards and maternal smoking habits were similar in the two groups. The prevalence of subsequent respiratory symptoms--cough, wheeze, nasal discharge, and hearing difficulties--was greater in index cases as was absence from school and family doctor consultation for respiratory illness. Bronchitis and asthma were significantly more common in the index group. Impaired ventilatory function and bronchial hyperreactivity were found in index cases when compared with controls. No differences in clinical characteristics and outcome were found in the two groups of index cases. The question whether lung "damage" during lower respiratory tract infection predisposes to subsequent respiratory problems or whether certain infants are more vulnerable than others to respiratory illnesses (including lower respiratory tract infection) from the onset is unanswered.