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

Serum eosinophil cationic protein and interleukin-5 in children with bronchial asthma and acute bronchiolitis

The aim of our study was to evaluate the clinical applicability of serum eosinophil cationic protein (ECP), interleukin-5 (IL-5) and total eosinophil counts in childhood asthma and bronchiolitis. These parameters were measured in 44 children aged 12-84 months with moderate and mild asthma during symptomatic and asymptomatic phases of disease. Fifteen of the patients were included at the time of admission to hospital due to an acute asthmatic attack, and ten of these were also examined one month after discharge. None of the patients were treated with glucocorticoids or cromoglycate at any time during the study. Serum ECP was significantly increased in the children with acute asthma compared to children with stable moderate asthma, stable mild asthma, as well as to controls. There was no difference between the groups with stable asthma or between stable asthma and controls, and there was large overlap between all groups of asthmatics and controls. Detectable levels of circulating IL-5 were demonstrated in eight of 15 children with acute asthma, with significantly higher levels in atopic children, whereas all samples from children with stable asthma and controls were negative. The results suggest that even though serum ECP and IL-5 increases during acute asthmatic attacks, these parameters cannot alone be used to discriminate between different groups of young children with stable asthma, nor between asthmatics and healthy controls. In addition, the same parameters of eosinophil inflammation were examined in serum samples from 25 children aged 1-17 months undergoing their first episode of acute bronchiolitis. Children with acute respiratory syncytial virus (RSV) bronchiolitis had significantly higher levels of serum ECP than those with RSV negative disease, whereas the total eosinophil counts were significantly decreased in all patients with acute bronchiolitis. Serum IL-5 was only detected in two children with acute bronchiolitis. The results suggest that the inflammation in RSV bronchiolitis differs from that induced by other viruses.

Association of life style with high risk of hyperimmunity and of immunosuppression mediated by IgE

To test the hypothesis that the increase in allergic prevalence is related not only to environmental allergens, but also to comprehensive life style, we administered to 733 workers at a hard metal plant a questionnaire that included 17 physical and mental health practices. We have shown that eight practices are associated with increases or decreases of total and specific IgE levels, serving to keep them within the normal range (5-400 IU/ml), after controlling for age, sex, and environmental factors. Further confirmation of the definite effect of life style on allergic reactions comes from higher heritability among younger pairs of identical twins of total IgE levels and allergic disorders than among older pairs of identical twins. A marked synergism was found among Undesirable life-style factors as bipolar high-risk factors for the development of allergic diseases or immunosuppression characterized by low natural killer (NK) cell activity through which soluble low-affinity IgE receptor is kept low. An effort to practice Desirable life styles, therefore, may be of benefit in reducing the risk of immunoallergic disorders.

Specific IgE detected by ELISA and immunoblot after human cytomegalovirus infection (HCMV) in renal transplant (RT) recipients

BACKGROUND

Specific HCMV IgE response has been reported by some authors, and was proposed as a valuable virologic marker of CMV infection.

OBJECTIVES

we evaluated specific HCMV IgE in renal transplant patients with active (primary and secondary) HCMV infection with special interest to symptomatic infections.

STUDY DESIGN

Specific IgE was tested retrospectively by ELISA and immunoblot (IB) on sera of 55 RT patients who were followed before and after transplantation with virologic markers of CMV infection.

RESULTS

Total serum IgE levels were similar in control group and in patients with primary and secondary HCMV infections. Anti-CMV specific IgE response by ELISA was more frequently found in patients with primary infection (76.9%) than in patients with secondary infection (47.1%). These specific IgE reacted on immunoblot with a 150 kDa protein in 84.6% of patients with primary infection and 94.1% with secondary infections; and reacted with rp52 (pUL44) in 76.9% of primary infection and 47.1% of secondary infection.

CONCLUSIONS

Anti-CMV specific IgE tested by immunoblot and ELISA is a marker of CMV infection. It was clearly detected in cases of active infection (primary and secondary) and was present in cases with severe CMV clinical manifestations. In contrast, anti-CMV specific IgE, was consistently negative among healthy blood donors. This is the first report of CMV proteins detected by IgE immunoblot.

Undetectable IgE responses after respiratory syncytial virus infection

Sequential nasopharyngeal secretions were collected from 81 infants from one day to three months after admission to hospital with respiratory syncytial virus (RSV) infection. Samples from 21 infants were assayed for anti-RSV IgE in an antigen capture ELISA assay. No IgE antibodies were detected although an assay of IgA antibodies carried out in parallel by a similar technique detected IgA antibodies in the secretions of all patients tested. Neither prior absorption of IgA or IgG, concentration of the secretions by freeze drying, nor enzyme amplification of the assay revealed any virus specific IgE. Using an antibody capture ELISA with a sensitivity of 0.85 IU/ml, IgE could be detected in sequential secretions of only one of the 81 RSV infected infants studied. Further testing of the secretions from 12 of these patients and those of a further 15 using an enzyme amplified assay with a sensitivity of 0.1 IU/ml revealed no further positives. Low concentrations of IgE were found in the sera of the majority of infants with RSV infection but they did not differ from those of virus negative children of a similar age collected between RSV epidemics. No rise in mean serum IgE concentrations between acute and convalescent samples was observed. No virus specific IgE was detected in the sera of any infant using the enzyme amplified antigen capture ELISA.

Virus-induced immunopathology

Several viruses cause damage to the tissue by immunopathological mechanisms. This chapter presents the principal examples of immunopathogenesis caused by the viruses, accompanied by speculations about its management. The most common mechanism of lesion development in virus induced immunopathology involves T cells. Usually, it seems that when CD8+ T cells act as the controlling cell type, lesions are acute and the outcome is decided quickly. The classic example is provided by LCM in mice. The newest candidate may turn out to be SNV infection in humans. Lesions orchestrated primarily by CD4+ T cells can be either acute or long-lasting. Curiously, in the LCMV example, if CD8+ T cells are removed from the scene, immunopathological responses may still occur and these involve CD4+ T cells. Such responses are far more chronic and of lower grade than those mediated by CD8+ T lymphocytes. One possible sequel to chronic inflammatory responses to viruses is that autoreactive inflammatory reactions are initiated and an autoimmune disease occurs. The adage that an ounce of prevention is worth a pound of cure is certainly true in the field of viral pathogenesis. Preventing viral infection or manipulating immune processes during the initial phases of infection is far more successful than attempting to counteract pathological events once underway.

Respiratory syncytial virus induces interleukin-10 by human alveolar macrophages. Suppression of early cytokine production and implications for incomplete immunity

Respiratory syncytial virus (RSV) causes repeated infections thought to be due to an ineffective immune response. We examined the hypothesis that incomplete immunity may result, in part, from RSV-infected alveolar macrophage production of IL-10 which can interfere with the production of immunoregulatory cytokines. We also assessed whether RSV induced the expression of the 2',5' oligoadenylate (2-5A)-dependent RNase L, an endoribonuclease involved in the antiviral activities of interferons. Human alveolar macrophages were exposed to medium (uninfected control), RSV, LPS, and RSV + LPS then were assessed for expression of the cytokines TNF-alpha, IL-1 beta, IL-8, IL-10, as well as 2-5A-dependent RNase L. LPS up-regulated the expression of protein and mRNA for all cytokines. RSV stimulated the protein levels of TNF-alpha, did not alter IL-1 beta, and decreased IL-8. RSV markedly stimulated protein expression of IL-10 and 2-5A-dependent RNase L. RSV had minor effects on the steady state mRNA levels of TNF-alpha, IL-1 beta, and IL-8, yet potently induced IL-10. Cells costimulated with RSV + LPS demonstrated reduced protein and mRNA levels of TNF-alpha, IL-1 beta, IL-8 but synergistically increased IL-10 levels compared to RSV- or LPS-activated cells. Kinetic analysis indicated that RSV induced a delayed and sustained increase in IL-10 transcripts. Furthermore, RSV-infected alveolar macrophage supernatants suppressed IL-1 beta and IL-8 production by LPS-stimulated alveolar macrophages as did recombinant IL-10. Anti-IL-10 neutralized these effects. These studies indicate that RSV is capable of suppressing production of early immunoregulatory cytokines through induction of IL-10 perhaps mediated by 2-5A-dependent RNase L (or other endoribonucleases) accounting for the ineffective immune response to this virus.

Eosinophil cationic protein in serum and nasal washes from wheezing infants and children

OBJECTIVE

To compare eosinophil counts and concentrations of eosinophil cationic protein (ECP) in serum and nasal wash fluid from wheezing infants and children with those from age-matched children without respiratory tract symptoms.

DESIGN

A case-control study of 71 children treated for wheezing and 59 control subjects in the University of Virginia Pediatric Emergency Department. The patients ranged from 2 months to 16 years of age. Eosinophil numbers and ECP concentrations were assessed in serum and nasal washes. Total serum IgE was measured and the radioallergosorbent test was used to measure IgE antibody to common inhalant allergens.

RESULTS

Among children less than the age of 2 years, markedly elevated levels of ECP (> 200 ng/ml) were measured in nasal washes from 9 (41%) of 22 wheezing patients and 1 (6%) of 17 control subjects (p < 0.03). None of these children had a positive radioallergosorbent test result for IgE antibody to common aeroallergens or a nasal smear containing 10% eosinophils. Few of the wheezing children under 2 years of age had either increased concentrations of total IgE or ECP in their serum or an elevated total blood eosinophil count. After the age of 2 years, the percentage of patients with nasal ECP levels greater than 200 ng/ml was also significantly higher in wheezing children than in control subjects (p < 0.001), and a positive correlation was observed between ECP concentrations in their nasal washes and other eosinophil responses (total blood eosinophil counts, serum ECP levels, and nasal eosinophil counts).

CONCLUSION

Increased concentrations of ECP were detected in nasal washes from wheezing infants and children, indicating that eosinophils may contribute to the pathogenesis of airway inflammation in some children who wheeze early in life.

Microbial inciters of acute asthma in urban Nigerian children

BACKGROUND

In tropical Africa the role of microbial agents of acute respiratory infections in acute exacerbations of bronchial asthma remains largely unexplored. However, empirical antibacterial therapy is frequently initiated in moderate to severe cases of acute asthma with symptoms of acute respiratory infection. A study was set up to determine how often acute respiratory infection is associated with acute asthma, to identify the associated pathogens, and to proffer appropriate therapeutic suggestions.

METHODS

Over a 16 month period, 86 episodes of acute asthma were studied for clinical and laboratory features of acute respiratory infection at the University College Hospital (UCH), Ibadan. Virological diagnosis was based on immunofluorescence studies of nasopharyngeal aspirates and/or serological tests using the microtitre complement fixation technique. Throat swabs and blood were cultured for bacterial agents.

RESULTS

Of the 64 cases who presented with rhinorrhoea, 51 (79.7%) were pyrexial (T > or = 37.6 degrees C). Inflammatory changes (frequently interstitial streakiness) were identified in 10 (19.6%) of the 51 chest radiographs; only two of these had lobar shadowing. Significant bacterial isolates were made in only three (3.5%) of the throat swabs and two (2.4%) of the blood cultures from the 86 cases; none had clinical septicaemia. On the other hand, 55 viral agents were identified from 39 (53%) of the 74 subjects studied; 16 (41.0%) had dual viral identifications. Respiratory syncytial virus (RSV) accounted for 20 (36.4%) identifications, parainfluenza virus (PIV) type 3 for 15 (27.3%), and influenza type A (Flu A) for 12 (21.8%). Viral identifications were significantly higher in infants and preschool subjects (< 5 years) and in those presenting with either rhinorrhoea or pyrexia.

CONCLUSIONS

The results of this study underscore the importance of viral upper respiratory infections in asthma exacerbations in a tropical setting. The paucity of clinical and investigative features of bacterial acute respiratory infection suggests that there is little rationale for routine antibiotic cover in children with acute exacerbations of asthma in the tropics.

Effect of rhinovirus 39 (RV-39) infection on immune and inflammatory parameters in allergic and non-allergic subjects

The economic impact and medical complication rate of the common cold are well documented, but many of the physiological, inflammatory, and immune responses to common cold viruses have only recently been investigated. The purpose of this study was to compare selected systemic immune and inflammatory responses to experimental rhinovirus (RV)-39 challenge in seronegative allergic rhinitis and non-allergic rhinitis subjects. Peripheral blood was obtained before (baseline), during (acute), and 23 days after (convalescent) RV-39 intranasal challenge and assayed for leucocyte histamine release, serum immunoglobulins, allergen-specific IgE antibodies, plasma histamine, and platelet aggregation. All subjects were infected, as manifested by viral shedding in nasal secretions or seroconversion. RV-39 infection induced significant acute increases in serum IgE, leucocyte histamine release, and platelet aggregation, but caused no changes in serum IgG, serum IgA, serum IgM, and plasma histamine. The first change was confined to the allergic rhinitis subjects. There was no evidence that the acute rise in total serum IgE was due to an elevation of a pre-existing, pollen-specific serum IgE antibody. The results show that intranasal challenge with RV-39 induced changes in systemic immune and inflammatory parameters with a unique response pattern in allergic rhinitis subjects.

Viral infections and the development of asthma

The possible role of viral infections in the inception of asthma has been the matter of considerable debate. Older data suggested that viral respiratory infections occurring during early life could alter the lungs and the immune system, thus starting the process leading to allergic sensitization and persistent bronchial responsiveness. More recent studies suggest that infants who wheeze belong to two distinct groups, which at present can only be differentiated by the evolution of their illness. Most of these infants have a transitory tendency to wheeze during viral infections, and their lung function shortly after birth is significantly lower than that of infants who will not wheeze during similar infections. Most of these children become symptom-free during the preschool years, and their condition is not associated with higher serum IgE levels. A smaller group of children who wheeze as infants will still have wheezing episodes during the early school years. The factors that determine which infants will become persistent wheezers are not well understood, but viral infections per se are likely to play a minor role, if any. Early sensitization to aeroallergens in subjects genetically predisposed to having high serum IgE levels seems to be the main risk factor for this condition.

Asthma and wheezing in the first six years of life. The Group Health Medical Associates

BACKGROUND

Many young children wheeze during viral respiratory infections, but the pathogenesis of these episodes and their relation to the development of asthma later in life are not well understood.

METHODS

In a prospective study, we investigated the factors affecting wheezing before the age of three years and their relation to wheezing at six years of age. Of 1246 newborns in the Tucson, Arizona, area enrolled between May 1980 and October 1984, follow-up data at both three and six years of age was available for 826. For these children, assessments in infancy included measurement of cord-serum IgE levels (measured in 750 children), pulmonary-function testing before any lower respiratory illness had occurred (125), measurement of serum IgE levels at nine months of age (672), and questionnaires completed by the children's parents when the children were one year old (800). Assessments at six years of age included measurement of serum IgE levels (in 460), pulmonary-function testing (526), and skin allergy testing (629).

RESULTS

At the age of six years, 425 children (51.5 percent) had never wheezed, 164 (19.9 percent) had had at least one lower respiratory illness with wheezing during the first three years of life but had no wheezing at six years of age, 124 (15.0 percent) had no wheezing before the age of three years but had wheezing at the age of six years, and 113 (13.7 percent) had wheezing both before three years of age and at six years of age. The children who had wheezing before three years of age but not at the age of six had diminished airway function (length-adjusted maximal expiratory flow at functional residual capacity [Vmax FRC]) both before the age of one year and at the age of six years, were more likely than the other children to have mothers who smoked but not mothers with asthma, and did not have elevated serum IgE levels or skin-test reactivity. Children who started wheezing in early life and continued to wheeze at the age of six were more likely than the children who never wheezed to have mothers with a history of asthma (P < 0.001), to have elevated serum IgE levels (P < 0.01), to have normal lung function in the first year of life, and to have elevated serum IgE levels (P < 0.001) and diminished values for VmaxFRC (P < 0.01) at six years of age.

CONCLUSIONS

The majority of infants with wheezing have transient conditions associated with diminished airway function at birth and do not have increased risks of asthma or allergies later in life. In a substantial minority of infants, however, wheezing episodes are probably related to a predisposition to asthma.

Tryptase and IgE concentrations in the respiratory tract of infants with acute bronchiolitis

It has been proposed that a specific IgE response contributes to the immunopathology of acute respiratory syncytial virus (RSV) bronchiolitis but previous work has been difficult to replicate. Indirect evidence that might support this contention was sought by measuring total IgE concentrations in bronchoalveolar lavage (BAL) samples obtained from intubated infants and by attempting to detect mRNA for IgE in cells obtained from both the upper and lower respiratory tract. Evidence of significant mast cell activation was sought by measuring tryptase concentrations in BAL fluid and serum. Detectable concentrations of IgE were found in two of seven BAL samples obtained more than five days after intubation and mRNA for IgE was demonstrated in three of six BAL samples and three of six samples obtained from the upper respiratory tract. Tryptase was detectable in 11 of 12 BAL samples with the two highest values detected on day 1. These values were raised compared with control samples but were not such to suggest that mast cell degranulation is the major contributor to the inflammatory process. These results suggest that IgE may be produced in the airways of infants in response to RSV infection. The relationships between IgE production, RSV infection, and symptoms of acute bronchiolitis remain obscure.

Virus-induced airway hyperresponsiveness in guinea pigs is related to a deficiency in nitric oxide

Intratracheal inoculation of parainfluenza type 3 virus to guinea pigs induces a marked increase in airway responsiveness in vivo and in vitro. In spontaneously breathing anesthetized guinea pigs inhalation of an aerosol containing the nitric oxide (NO) precursor L-arginine (2.0 mM) completely prevented the virus-induced airway hyperresponsiveness to histamine. In addition, perfusion of L-arginine (200 microM) or the direct NO-donor S-nitroso-N-acetyl-penicillamine (SNAP, 1 microM) through the lumen of tracheal tubes from infected animals prevented the increase in airway responsiveness to histamine or the cholinoceptor agonist methacholine. The NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME, 120 microM) did not further increase the virus-induced airway hyperresponsiveness. In additional experiments, NO was measured with an Iso-NO nitric oxide meter and sensor. Stimulation of control tissues in vitro with histamine (10(-3) M) resulted in a contraction with a simultaneous release of NO (44.5 +/- 5.4 nM). The release of NO was markedly reduced by 75% (P < 0.01, 11.4 +/- 3.1 nM) in tracheas from virus-infected animals that demonstrated enhanced contractile responses. Preincubation of tissues from virus-treated guinea pigs with L-arginine (200 microM) completely prevented the enhanced contraction and simultaneously returned the NO production to control values (51.2 +/- 3.4 nM). An NO deficiency might be causally related to the development of airway hyperresponsiveness after a viral respiratory infection.

Eosinophil cationic protein in nasal secretion and in serum and myeloperoxidase in serum in respiratory syncytial virus bronchiolitis: relation to asthma and atopy

Eosinophil cationic protein (ECP) in nasal secretions was determined in 34 infants with respiratory syncytial virus (RSV) bronchiolitis during the acute infection stage and one and six months later. ECP in serum was determined in 19 of these children at the same time. Myeloperoxidase (MPO) was determined in the same 19 children at the acute infection stage and after one month. All children were followed prospectively for two years after the infection with regard to the development of bronchial obstructive symptoms. Asthma, defined as three or more episodes of bronchial obstruction verified by a physician, developed in 18% of children and less severe obstructive symptoms in 29%. A screening test for food IgE antibodies in serum was performed six months and a skin prick test two years after the acute infection. Nasal ECP/albumin ratios after six months were significantly higher than during the acute RSV infection. MPO, but not ECP, levels in serum were significantly elevated at the time of acute infection compared with levels after one month. Nasal ECP/albumin ratios at the acute infection were compared to a control group of 27 infants with non-RSV upper respiratory tract infections and did not differ. It was not possible to predict, either from ECP/albumin ratios in nasal secretion or from ECP and MPO in serum, which children would develop asthma, other bronchial obstructive symptoms or positive IgE tests.

The role of respiratory infections in airway hyperresponsiveness and asthma

Viruses provoke symptoms of wheezing in many patients with asthma. Furthermore, there is evidence that viruses increase airway responsiveness in non-asthma patients. The mechanisms involved in these reactions are not clearly established, but evidence suggests that the ability of viruses to promote this bronchial responsiveness may be related to an upregulation of the allergic inflammatory reaction. This would explain why patients may be more prone to have a late asthmatic reaction.

Immunology in the pediatrician's office

The development of antibody-mediated immunity is reflected in the maturation of B lymphocytes, in the changing levels of total immunoglobulins, and in the development of specific antibodies first to proteins and then sequentially to different types of polysaccharides. The measurement of anti-pneumococcal antibodies allows us to recognize specific antibody deficiencies, which need to be differentiated from normal developmental phases in the maturation of antibody-mediated immunity. The recognition of the late phase of IgE mediated allergic reactions is important to understanding the chronic manifestations of allergy. Chronic manifestations of allergy are frequently missed because they do not appear to be clearly related to acute triggers of allergic reactions. These conditions can be appropriately diagnosed, prevented, and treated, however, when the mechanisms of the late manifestations of allergy are understood. The integration of knowledge about the development of immunity and of allergic diseases enhances the pediatrician's ability to care for patients with immunologic abnormalities.

Bronchial asthma after early childhood wheezing: a follow-up until 4.5-6 years of age

Over a period of 12 months from 1981 to 1982, 83 patients aged less than 2 years were treated in hospital for acute bronchiolitis. The children were followed-up prospectively; 68 (83%) completed the study until 4.5-6.0 years of age. At this age, 17 (25%) of the 68 children with bronchiolitis still suffered from wheezing attacks. These 17 asthmatics suffered from both atopic dermatitis (29 versus 6%) and allergic rhinitis (29 versus 8%) more frequently than non-asthmatic children. In contrast, positive results in the skin prick tests were almost equally common (29 and 20%) in asthmatic and non-asthmatic children. In these tests, allergies to birch pollen, timothy grass pollen and house dust mite were most common; asthma was particularly associated with house dust mite allergy. The presence of atopic dermatitis, elevated immunoglobulin E values and repeated wheezing episodes between 1 and 2 years of age were significant risk factors for later asthma. In conclusion, the risk for later asthma is increased after early childhood bronchiolitis; the frequency of asthma was 25% in the present study. Our results confirm that atopics are at a greater risk of developing asthma later in childhood than non-atopics; the risk was significant from 1 year of age onwards.

Eosinophil cationic protein in nasopharyngeal secretions and serum of infants infected with respiratory syncytial virus

Eosinophil cationic protein (ECP) was assayed in nasopharyngeal secretion (NPS) and serum from 42 infants, hospitalized with acute lower respiratory infection, in El Salvador and the results analyzed in relation to etiology of the infection. ECP concentrations were high in NPS, at an average 50 times higher than those found in serum. Exceedingly high levels of ECP (> 1000 micrograms/L) were found more frequently in wheezing than in non-wheezing children (30% vs 7%) and, accordingly, were more commonly found in children hospitalized with bronchiolitis than in those with pneumonia. Excessive levels were significantly more common in girls than in boys. Of the 42 cases, 28 were found to be caused by respiratory syncytial virus (RSV) subgroup A, and 3 by RSV-B, by means of detection of RSV antigen in nasopharyngeal cells. ECP serum levels were moderately elevated during the acute phase of the respiratory infection and increased slightly but significantly, in cases with RSV antigen-positive bronchiolitis, but not in those with pneumonia. The ECP levels in NPS from patients in Sweden who, by antigen detection in NPS cells, were diagnosed as either RSV or para-influenza 3 infection or none of these, were similar. These results indicate that elevation of ECP in NPS is associated with acute lower respiratory infection in general, but particularly pronounced in cases of bronchiolitis. Elevation of ECP is not an exclusive consequence of RSV infection, but may occur to an equal extent in infections caused by other agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumour necrosis factor-alpha and leukotriene E4 production in wheezy infants

It is not clear why certain infants wheeze during viral upper respiratory tract infections (URTIs) but it is possible that they have a tendency to mount an exaggerated inflammatory response leading to production of mediators that induce airway narrowing. We studied nasal tumour necrosis factor-alpha (TNF alpha) and urinary leukotriene E4 (LTE4) production during infection and after recovery in 31 wheezy infants (median age 6.2 months). Urinary LTE4 production was not altered during wheezy episodes or URTIs. However, the concentration of TNF alpha in nasal lining fluid (NLF) was significantly increased during acute episodes of wheeze compared to recovery (median [interquartile range] of 293 [42-1753] vs 0 [0-203] pg/ml NLF). TNF alpha was detectable more often and in higher concentration when wheezing was due to respiratory syncytial virus. TNF alpha was also present in 7/30 asymptomatic wheezy infants who had recovered from infection (> 100 pg/ml NLF) and in 4/7 non-wheezy siblings during URTIs (> 200 pg/ml NLF). This suggests that upregulation of TNF alpha production is not the only factor that makes some infants wheeze.

Respiratory syncytial virus vaccines: can we improve on nature?

Both inactivated and live RSV candidate vaccines will continue to be tested in infants and young children. Sequential vaccination, with a first dose of live attenuated vaccine followed by boosting with intramuscular subunit vaccines, also is an option. We are encouraged by the fact that influenza subunit and cold-adapted live vaccines are both safe and immunogenic in infants and children of the same age group. Testing of RSV vaccines must proceed at a slower pace because of the phenomenon of vaccine-induced enhanced disease. Curiously, this phenomenon of disease enhancement has not been demonstrated in the case of inactivated influenza or parainfluenza virus vaccines. Another important step in the development of RSV vaccines is to determine a target population. Clearly, children with underlying cardiac or pulmonary disease would benefit from an RSV vaccine. It can be expected that 1% of all infants in the general population will be hospitalized for RSV infection during their first year of life. These infants also would appear to be good candidates for an RSV vaccine, but it is unclear how they would be identified before infection occurs. Immunization of the entire population of infants to protect these 1% would be feasible only if the vaccine were inexpensive and easily administered.

Antigenic diversity of respiratory syncytial viruses and its implication for immunoprophylaxis in ruminants

Bovine respiratory syncytial virus (BRSV) is a very important pathogen of cattle and perhaps other ruminants. It is a major contributor to the incidence of respiratory tract disease in nursing beef and feedlot and dairy calves. The genome of respiratory syncytial viruses encodes 10 proteins translated from 10 unique mRNAs. The major glycoprotein (G), fusion protein (F), 1A protein and the 22K protein are components of the viral envelope. The nucleocapsid contains the nucleocapsid protein (N), the phosphoprotein (P), and the large protein (L). The matrix protein (M) forms a structural layer between the envelope and the nucleocapsid. Antibodies to all the structural proteins develop in convalescent calves. However, evidence suggests that immunity develops primarily as a result of the antigenic stimulus by the major glycoprotein G and the fusion glycoprotein F. It is known also that activated cytotoxic T cells interact with N and F protein antigens and helper T cells interact with N, F, and 1A protein antigens. With the exception of the major glycoprotein, the respective proteins of various respiratory syncytial viruses share major antigenic domains. Based on antigenic differences of the major glycoprotein, at least 3 subgroups of RSV are recognized; human A, human B, and bovine RSV. Indirect evidence suggests that a second subgroup of BRSV exists. However, we have identified only one BRSV subgroup based on our work with RNase mismatch cleavage analysis of the G protein gene from a limited number of strains. Furthermore, our data indicated that a caprine RSV isolate is closely related to the bovine strains, but an ovine isolate is not. The latter may constitute yet another subgroup of RSV. These data affect decisions on optimization of immunoprophylaxis since evidence suggests that protection against a homologous RSV subgroup virus is superior to that against a heterologous strain in immune subjects.

Virus-induced airway inflammation and hyperresponsiveness in the guinea-pig is inhibited by levodropropizine

Intratracheal Parainfluenza type 3 (PI-3) virus inoculation of guinea pigs leads to a non-specific airway hyperresponsiveness in vivo and in vitro which coincides with a significant increase in the number of inflammatory cells in the broncho-alveolar lavage fluid (90% increase, 4 days after inoculation). The activity of the bronchoalveolar cells, as measured by the chemiluminescence production of infected animals is significantly diminished (34.2%, 4 days after inoculation) after renewed stimulation with PI-3 virus in vitro as compared to the chemiluminescence production by bronchoalveolar cells obtained from control guinea pigs. Pretreatment of the guinea-pigs with the antitussive agent levodropropizine, administered intra-peritoneally twice a day for five successive days at a dose of 10 mg/kg, prevents the virus-induced airway hyperresponsiveness in vivo and in vitro, and inhibits the influx of broncho-alveolar cells. Levodropropizine at a dose of 1 mg/kg did not modulate these responses. Further, the decrease in chemiluminescence production of broncho-alveolar cells obtained from virus-infected animals after PI-3 virus stimulation in vitro was inhibited by levodropropizine (10 mg/kg). These data demonstrate the ability of levodropropizine to counteract the hyperresponsiveness phenomenon and the associated inflammatory event induced by PI-3 virus, an effect which may be due to its capacity to act on the peptidergic system or may be due to the anti-allergic/bronchoconstrictor property of this compound.

Virus-induced changes in airway responsiveness, morphology, and histamine levels in guinea pigs

A significant increase in airway responsiveness to histamine was observed in vitro and in vivo 4 days after intratracheal inoculation of parainfluenza Type 3 (PI-3) virus to guinea pigs. Light microscopic and ultrastructural examination of the central airways of animals inoculated with virus revealed stratification of the epithelial lining, with pronounced loss of cilia and granule-depleted goblet cells. In the peripheral airways, typical lesions of patchy alveolitis and bronchiolitis were found. The alveolar epithelium often lacked Type I alveolar cells and was lined merely by cells containing osmiophilic lamellar bodies typical of Type II alveolar cells. PI-3 virus inoculation resulted in a reduction in the number of airway mucosal mast cells, particularly in the bronchioles, and in a change of density of the granules of mast cells. Further, a significant rise (100%) in histamine concentration was observed in lung lavage fluid after virus inoculation. The prostaglandin E2 (PGE2) content in the lavage fluid was not changed. After stimulation with histamine, the tracheae of animals inoculated with control solution or PI-3 virus produced similar amounts of PGE2. These data indicate that PI-3 virus activates airway mast cells and increases the histamine content in the respiratory tract. Neither the virus-induced lung damage nor the increased levels of histamine in the airways influence the release of the epithelially derived relaxing factor PGE2. It is suggested that mast cell-derived products, in particular histamine, are involved in virus-induced airway hyperresponsiveness.

Relationship between viral antibodies and bronchial hyperresponsiveness in 495 unselected children and adolescents

The purpose of this study was to investigate whether recent and previous subclinical viral respiratory infection can explain the presence of increased bronchial responsiveness to histamine. We studied a randomly selected population of 495 children and adolescents, aged 7-16 years, from Copenhagen. If the subjects had had symptoms of respiratory infection recently, the examination was postponed for at least 6 weeks. Bronchial hyperresponsiveness (BHR) to inhaled histamine was found in 79 (16%) of the subjects, of whom 28 had asthma. Forty-eight subjects (10%) had increased levels of serum IgM antibodies against either parainfluenza, influenza, adenovirus, or respiratory syncytial virus (RSV), reflecting a recently acquired infection. No association between BHR and antibodies against respiratory viruses was found, as 7 (8.9%) of the 79 subjects with BHR and 41 (9.9%) of the 416 subjects without BHR had viral antibodies. Furthermore, no association between degree of bronchial responsiveness and viral antibodies was found. Moreover, 251 individuals (51%) had signs of earlier RSV infection, i.e. IgG antibodies against RSV. No relationship was found between age of the subjects and the presence of antibodies against either respiratory viruses in general or IgG-RSV. No relationship was found between the presence of antibodies against RSV and BHR; furthermore, evidence of earlier RSV infection was unrelated to the level of lung function and degree of bronchial responsiveness. We conclude that increased bronchial responsiveness in asymptomatic, unselected schoolchildren and adolescents is not likely to be caused by recent or previous viral respiratory infections.

Virus-induced airway hyperresponsiveness in the guinea-pig: possible involvement of histamine and inflammatory cells

1. Guinea-pig tracheal contractions by histamine and by the cholinoceptor agonist, arecoline, are significantly enhanced (30% and 20%, respectively), 96 h after intra-tracheal inoculation with Parainfluenza-3 (PI-3) virus. 2. The airway hyperresponsiveness in animals inoculated with virus coincides with a significant increase in the number of broncho-alveolar cells (82%), and in the albumin concentration (121%) in lung lavage fluid, relative to values obtained in guinea-pigs challenged with control solution. 3. The chemiluminescence production by isolated broncho-alveolar cells, obtained from virus-infected guinea-pigs 96 h after inoculation stimulated with PI-3 virus in vitro, is significantly reduced by 42% relative to broncho-alveolar cells obtained from animals inoculated with control solution. This diminution was not specific for stimulation by PI-3 virus since the chemiluminescence production was also significantly reduced by 30% in response to zymosan. 4. Pretreatment of the guinea-pigs with the anti-allergic drugs, oxatomide (2.5 mg kg-1) or nedocromil (2.5 mg kg-1), or the specific H1-histamine receptor antagonist, levocabastine (0.25 mg kg-1), administered intra-peritoneally twice a day for five successive days, inhibits the virus-induced airway hyperresponsiveness, suppresses the influx of broncho-alveolar cells and increase in albumin content, and corrects the reduced chemiluminescence production by broncho-alveolar cells in response to zymosan. 5. In contrast, the cyclo-oxygenase inhibitor, suprofen (5.0 mg kg-1), the 5-HT2 receptor antagonist, ketanserin (0.63 mg kg-1), or the Ca2+ overload blocker, flunarizine (2.5 mg kg-1) do not modify the above mentioned processes. 6. The platelet-activating factor receptor antagonist, WEB 2170 (10 mg kg-1), reduces virus-induced airway hyperresponsiveness and influx of broncho-alveolar cells into the lungs but does not attenuate the increase of albumin in the bronchial lavage fluid. 7. Guinea-pigs nebulized with histamine, twice a day (30 min) during 4 successive days, do not demonstrate an increased airway responsiveness, but instead show tachyphylaxis in response to histamine in vitro. In addition, no influx of inflammatory cells is found in these animals. 8. These results suggest that histamine does not directly increase the responsiveness of the guinea-pig trachea; however, histamine may be involved in a cascade of events leading to airway hyperresponsiveness after a viral infection, a process that could be related to an influx and/or an activation of broncho-alveolar cells after PI-3 virus stimulation.

Evaluation of immunoglobulin E-specific antibodies and viral antigens in nasopharyngeal secretions of children with respiratory syncytial virus infections

Enzyme immunoassays were developed to detect the presence of specific immunoglobulin E (IgE) antibodies and respiratory syncytial (RS) virus structural proteins in nasopharyngeal secretions in order to improve the knowledge on some aspects of the pathogenesis of severe acute lower respiratory tract infections caused by RS virus. These assays were used to analyze clinical specimens from children with RS virus-associated infections (bronchiolitis and pneumonia), and the findings were correlated with the patients' clinical symptoms. The results indicate the presence of specific IgE against the two external glycoproteins (G and F) and the absence of detectable IgE levels for the internal viral antigens. There was a correlation between the levels of IgE-specific antibodies and the amount of viral protein F in the secretions, indicating that the IgE response against the viral glycoproteins might be related to the antigen load. In addition, a correlation was found between higher levels of both viral protein F-specific IgE and F antigen with higher respiratory rates in children with pneumonia. These findings may be relevant because they suggest an association between the virus load and the immune response in the pathogenesis of RS virus infections.

Nasal IgA response in wheezy infants

It is unknown why some infants wheeze during upper respiratory tract infections. One possibility is that secretory IgA, which has a major role in mucosal defence against viral infection, might be deficient in wheezy infants. The nasal IgA response to upper respiratory tract infection in 32 wheezy infants (median age 5.8 months) was compared with nine siblings (median age 2.6 years) who had nasal symptoms only. Nasal lavage was performed during infections and on follow up when free from symptoms, using inulin as a marker of dilution to determine absolute concentrations of IgA in the nasal secretions. The two groups showed a similar increase in total IgA and total protein levels during infection, but secretory IgA concentrations were unchanged. This study shows that wheezy infants have a normal nasal IgA response to infection and that the increase in total IgA during early infection is due to plasma exudation rather than increased production of secretory IgA.

Airway inflammation, bronchial reactivity and asthma

Asthma is a common disease of children the basis of which is a state of chronic immunological inflammation which causes bronchial hyperreactivity and renders the patient liable to develop widespread airways obstruction in response to a variety of stimuli. In many instances it is likely that the immunological inflammation results from ongoing antigenic stimuli with the release of chemical mediators responsible for short term bronchospasm and cytokines responsible for the ongoing inflammatory process. Other insults can apparently result in very similar immunological events in asthmatics, particularly viral infections and a similar process can be initiated in children without asthma, including those with chronic bacterial infections of the lungs. There are differences in the bronchial hyperreactivity of asthma and other diseases which suggest that in the asthmatic the mast cell is either different structurally or functionally and this renders the patient susceptible to exercise induced asthma in addition to the bronchial hyperreactivity to chemical mediators common to a number of diseases with hyperreactivity. There is good evidence of direct genetic control of atopy and the large majority of children with asthma are atopic but there is no direct genetic link between atopy and asthma and twin studies strongly suggest the existence of a 'permissive' asthma gene which will allow the disease to develop if there is an appropriate external trigger. The only drugs which have been shown to significantly reduce bronchial reactivity are the corticosteroids with a lesser effect noted for sodium cromoglycate and nedocromil. Inhaled corticosteroids can reverse the immunologic inflammatory process and reduce bronchial reactivity, sometimes to normal levels, but on stopping treatment the patient reverts back to the asthmatic state. At the present time it appears that controlled longterm inhaled corticosteroid therapy is the most rational treatment for significant perennial childhood asthma.

The relationship of RSV-specific immunoglobulin E antibody responses in infancy, recurrent wheezing, and pulmonary function at age 7-8 years

In order to determine if respiratory syncytial virus (RSV)-specific IgE responses at the time of bronchiolitis in infancy are related to recurrent wheezing and pulmonary function at 7-8 years of age, a cohort of 43 infants was identified at the time of their initial RSV bronchiolitis episode. RSV-specific IgE responses in nasopharyngeal secretions were determined, and patients were then followed prospectively with notation of the number of wheezing episodes and exposure to cigarette smoke at home. At 7-8 years of age the patients underwent skin testing to 7 environmental allergens and pulmonary function testing, including pulse oximetry and methacholine challenge. Pulmonary function following inhalation of bronchodilating agents was compared to baseline pulmonary function results in order to determine if abnormalities of pulmonary function were reversible. Recurrent wheezing following bronchiolitis was associated with the initial RSV-IgE response, as well as with a family history of asthma. Current wheezing at age 7-8 years was associated with 2 or more positive skin tests (P < 0.01), a history of exercise-induced wheezing (P = 0.01), and increased sensitivity to methacholine (P < 0.01). Pulmonary function test results were similar for groups with and without recurrent wheezing following bronchiolitis. For the entire study group, RSV-IgE specific responses were unrelated to pulmonary function, but small airway dysfunction was associated with passive smoking (P < 0.025), and both large airway dysfunction and increased airway reactivity were associated with the number of positive skin tests (P < 0.025). Reduced small airway function improved following bronchodilator inhalation.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factors for developing wheezing and asthma in childhood

Wheezing lower respiratory tract illness in infancy and asthma share the clinical findings of wheezing and respiratory distress. Although the link between wheezing lower respiratory tract illness in infancy and the subsequent development of asthma is a limited one, both conditions do share some common risk factors, including exposure to environmental tobacco smoke, difficult living conditions (low socioeconomic class, crowding, allergen exposure), and increased risk in males. The impact of baseline lung function on wheezing lower respiratory tract illness risk is substantial and may be independent of airway reactivity. In contrast, the development of chronic airway inflammation mediated by allergic sensitization plays a central role in the development of persistent asthma. Although the endogenous risks for these two outcomes may be fixed, it is clear that caregivers may help to reduce or eliminate the exogenous risks listed earlier by parental education and improvement of the living conditions of young children.

The impact of respiratory infections on asthma

It is apparent that the effects of viral respiratory infections on the development of airway hyperresponsiveness are multiple and interrelated and involved the production of viral specific IgE, upregulation of leukocyte inflammatory activity, enhancement of the factors involved in the generation of late phase allergic responses, altered beta-adrenergic and cholinergic nervous system activity, and damage to the airway epithelium. The summation of these effects is the development of airway inflammation rather than a direct effect on bronchial smooth muscle, per se. An understanding of this pathogenesis underscores the relative importance of anti-inflammatory rather than antimicrobial therapy in viral-induced exacerbations in asthma symptoms.

Is asthma curable?

The information reviewed here supports the concept that asthma is potentially curable. Reports of complete, durable remission of asthma can no longer be regarded as fortuitous occurrences, unrepresentative of asthma in general. Systematic studies of anti-inflammatory drug therapy designed to explore possible induction or remission of asthma clearly are warranted. Studies of aggressive anti-inflammatory drug therapy of asthma at the onset, to avoid establishment of chronic asthma, also are desirable. The current goals of therapy of asthma have been revised to include reduction of airway hyperreactivity with topical anti-inflammatory drugs, in addition to relief of current symptoms. This approach may provide valuable resistance to exacerbations in response to antigen exposures, infections, exercise, or irritants. Pathophysiologic mechanisms apparently essential to the establishment and perpetuation of chronic asthma have been identified. These processes may be vulnerable to eradication by combination therapy with existing pharmacologic agents such as cyclosporin A or FK-506 (to suppress cytokine production), gold, methotrexate, and other anti-inflammatory drugs, alone or in combination. Equally important, the vigorous anti-inflammatory therapy may be necessary only long enough to achieve a resolution of the chronic pulmonary inflammation. Systematic studies of the use of these agents to induce partial, or complete, stable remissions of asthma should be performed. In the past, remissions of asthma in children with neoplasia and the other patients presented herein were complete, durable, and welcome, but they were largely unexpected and unpredictable. For the future, there is increasing reason to believe that predictable pharmacologically induced remission of asthma will be feasible.