Peripheral blood eosinophil counts and eosinophil cationic protein content of respiratory secretions in bronchiolitis: relationship to severity of disease

Limited clinical role of blood eosinophil levels in early life atopic disease: A mother-child cohort study

BACKGROUND

Blood eosinophil count is a well-established biomarker of atopic diseases in older children and adults. However, its predictive role for atopic diseases in preschool children is not well established.

OBJECTIVE

To investigate the association between blood eosinophil count in children and development of atopic diseases up to age 6 years.

METHODS

We investigated blood eosinophil count at age 18 months and 6 years in relation to recurrent wheeze/asthma, atopic dermatitis, allergic rhinitis, and allergic sensitization during the first 6 years of life in the two Copenhagen Prospective Studies on Asthma in Childhood cohorts (n = 1111). Blood eosinophil count was investigated in association with remission of existing atopic disease, current atopic disease, and later development of atopic disease.

RESULTS

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis, while blood eosinophil count at age 6 years was associated with increased occurrence of current wheezing/asthma (OR = 1.1; 1.04-1.16, p = .0005), atopic dermatitis (OR = 1.06; 1.01-1.1, p = .02), and allergic rhinitis (OR = 1.11; 1.05-1.18, p = .0002). Blood eosinophil count at 18 months did not predict persistence or development of recurrent wheeze/asthma or atopic dermatitis at age 6 years.

CONCLUSION

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis and did not predict persistence or development of disease. This implies a limited clinical role of blood eosinophil levels in early-life atopic disease and questions the clinical value of blood eosinophil counts measured in toddlers as a predictive biomarker for subsequent atopic disease in early childhood.

Blood eosinophils during bronchiolitis: Associations with atopy, asthma and lung function in young adults

AIM

To study if blood eosinophils during bronchiolitis were associated with atopy, asthma and lung function in young adults and if these associations differed between respiratory syncytial virus (RSV) bronchiolitis and non-RSV bronchiolitis.

METHODS

This historical cohort enrolled 225 subjects. Blood eosinophils were measured during bronchiolitis in infancy, and the subjects were invited to a follow-up at 17-20 years of age including questionnaires for asthma and examinations of lung function and atopy.

RESULTS

The level of eosinophils was positively associated with subsequent atopy in the unadjusted analysis, but not in the adjusted analysis, and not with asthma. There was a negative association between the level of eosinophils and forced vital capacity (FVC) (-0.11; -0.19, -0.02) and forced expiratory volume in first second (FEV₁ ) (-0.12; -0.21, -0.03) (regression coefficient; 95% confidence interval). The non-RSV group had higher levels of eosinophils during bronchiolitis, but there was no interaction between the level of eosinophils and RSV status for any outcome.

CONCLUSIONS

The level of eosinophils during bronchiolitis was negatively associated with lung function in young adult age, but we found no associations with atopy or asthma. These associations were not different after RSV bronchiolitis compared to non-RSV bronchiolitis.

Immune biomarkers predicting bronchiolitis disease severity: A systematic review

Bronchiolitis is one of the leading causes of hospitalisation in infancy, with highly variable clinical presentations ranging from mild disease safely managed at home to severe disease requiring invasive respiratory support. Identifying immune biomarkers that can predict and stratify this variable disease severity has important implications for clinical prognostication/disposition. A systematic literature search of the databases Embase, PubMed, ScienceDirect, Web of Science, and Wiley Online Library was performed. English language studies that assessed the association between an immune biomarker and bronchiolitis disease severity among children aged less than 24 months were included. 252 distinct biomarkers were identified across 90 studies. A substantial degree of heterogeneity was observed in the bronchiolitis definitions, measures of disease severity, and study designs. 99 biomarkers showed some significant association with disease severity, but only 18 were significant in multiple studies. However, all of these candidate biomarkers had comparable studies that reported conflicting results. Conclusion: The heterogeneity among included studies and the lack of a consistently significant biomarker highlight the need for consensus on bronchiolitis definitions and severity measures, as well as further studies assessing their clinical utility both in isolation and in combination.

Blood eosinophilia is associated with unfavorable hospitalization outcomes in children with bronchiolitis

BACKGROUND

Bronchiolitis, the most common indication for hospitalization of young children, is associated with subsequent asthma. Blood eosinophilia is associated with increased severity of asthma, but it is unclear if eosinophilia is associated with severity of illness in bronchiolitis. We hypothesized that blood eosinophilia is associated with unfavorable short-term outcomes of bronchiolitis hospitalizations.

METHODS

Data from initial bronchiolitis admissions to our institution between 2010 and 2013 were extracted using Population Explorer software (Explorys, Cleveland, OH). Children were categorized as "CBC-none" (no complete blood count [CBC] data during the first 7 days of hospitalization), EOS-positive (at least one CBC with ≥300 eosinophils per microliter or ≥3% of all leukocytes identified as eosinophils) or EOS-negative (at least one CBC and no eosinophilia). The association between hospitalization duration and maximum absolute eosinophil count (AEC) was analyzed using Spearman correlation. Variables independently associated with prolonged (≥72 hr) hospitalization were identified using stepwise multivariate logistic regression.

RESULTS

In 1356 inpatients <24 months with bronchiolitis, median hospitalization duration was 2.46 days and 38.0% had prolonged hospitalization. CBC data were available in 32.4% of subjects: 20.7% were EOS-positive and 79.3% were EOS-negative. Increased maximum AEC was significantly associated with longer duration of hospitalization. Prolonged hospitalization was independently associated with EOS-positive versus EOS-negative children (OR 1.88, 95%CI: 1.12-3.17, P = 0.020). Mechanical ventilation was most common in EOS-positive subjects (24.2% of cases), versus EOS-negative (7.2%) and CBC-none (0.7%) (P < 0.001).

CONCLUSIONS

Blood eosinophilia is associated with unfavorable clinical outcomes in a large cohort of inpatients with bronchiolitis.

Low eosinophils during bronchiolitis in infancy are associated with lower risk of adulthood asthma

BACKGROUND

Infant bronchiolitis may be the first manifestation of asthma.

AIM

To evaluate the association of early-childhood risk or protective factors for asthma and lung function reduction in adults 30 years after bronchiolitis in infancy.

METHODS

Forty-seven former bronchiolitis patients attended the clinical study at the median age of 29.5 years, including doctoral examination and measurement of post-bronchodilator lung function with flow-volume spirometry. Data on early-life risk factors including blood eosinophil counts on admission for bronchiolitis and on convalescence 4-6 weeks after bronchiolitis were available.

RESULTS

Low blood eosinophil count <0.25 × 10E9/l on admission for bronchiolitis was a significant protective factor and high blood eosinophil count >0.45 × 10E9/l on convalescence was a significant risk factor for asthma in adulthood independently from atopic status in infancy. Parental asthma and high blood eosinophil count >0.45 × 10E9/l during bronchiolitis were significant risk factors for irreversible airway obstruction (FEV1/FVC ratio below the 5th percentile lower limit of normality after bronchodilation).

CONCLUSION

Our adjusted analyses confirmed that eosinopenia during infant bronchiolitis predicted low asthma risk and eosinophilia outside infection predicted high asthma risk up to the age of 28-31 years. Parental asthma and eosinophilia during bronchiolitis were recognized as risk factors for irreversible airway obstruction.

Endobiogeny: a global approach to systems biology (part 2 of 2)

ENDOBIOGENY AND THE BIOLOGY OF FUNCTIONS ARE BASED ON FOUR SCIENTIFIC CONCEPTS THAT ARE KNOWN AND GENERALLY ACCEPTED: (1) human physiology is complex and multifactorial and exhibits the properties of a system; (2) the endocrine system manages metabolism, which is the basis of the continuity of life; (3) the metabolic activity managed by the endocrine system results in the output of biomarkers that reflect the functional achievement of specific aspects of metabolism; and (4) when biomarkers are related to each other in ratios, it contextualizes one type of function relative to another to which is it linked anatomically, sequentially, chronologically, biochemically, etc.

Testing protocols: care of biological samples in a rural setting

The purpose of this study is to evaluate collection, transport, and storage protocols of urine and air allergen samples from infants in a rural setting. Infant urine and aeroallergen samples (n = 21) are collected in the home setting in rural areas where time and distance to the central laboratory is a consideration. Urine samples are analyzed using ELISA tests after being transported using three different techniques: (a) ambient temperature, (b) dry ice, and (c) packaged on dry ice and shipped commercially. Following initial ELISA testing for levels of cytokines, urine samples are frozen at -70 degrees Celsius for 6 months. Samples are then reanalyzed for levels of cytokines. Dust samples are analyzed for levels of aeroallergens, stored at 4 degrees for 6 months, and reanalyzed. The integrity of samples varies by biomarker, shipment temperature, and storage time, creating a high degree of variability in results.

Understanding respiratory syncytial virus (RSV) vaccine-enhanced disease

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and children worldwide. In addition, RSV causes serious disease in elderly and immune compromised individuals. RSV infection of children previously immunized with a formalin-inactivated (FI)-RSV vaccine is associated with enhanced disease and pulmonary eosinophilia that is believed to be due to an exaggerated memory Th2 response. As a consequence, there is currently no licensed RSV vaccine and detailed studies directed towards prevention of vaccine-associated disease are a critical first step in the development of a safe and effective vaccine. The BALB/c mouse model of RSV infection faithfully mimics the human respiratory disease. Mice previously immunized with either FI-RSV or a recombinant vaccinia virus (vv) that expresses the attachment (G) glycoprotein exhibit extensive lung inflammation and injury, pulmonary eosinophilia, and enhanced disease following challenge RSV infection. CD4 T cells secreting Th2 cytokines are necessary for this response because their depletion eliminates eosinophilia. Intriguing recent studies have demonstrated that RSV-specific CD8 T cells can inhibit Th2-mediated pulmonary eosinophilia in vvG-primed mice by as yet unknown mechanisms. Information gained from the animal models will provide important information and novel approaches for the rational design of a safe and efficacious RSV vaccine.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

Peripheral blood eosinophilia in association with generalized pustular and erythrodermic psoriasis

BACKGROUND

In recent studies, it has been documented that the eosinophil cells play active role in many kinds of inflammatory disorders. Measurements of the mediators released by eosinophils and cell counts in serum and skin have provided some evidence indicating the role of eosinophils in psoriasis.

OBJECTIVE

To evaluate the blood eosinophil cell count in patients with erythrodermic psoriasis and generalized pustular psoriasis.

METHODS

In this study, 48 patients with histopathologically proven psoriasis (33 with erythrodermic, 15 with generalized pustular); 43 patients with maculopapular, erythematous, or bullous drug eruption with widespread involvement; and 51 patients with basal cell carcinoma were included. These three groups were compared with each other in terms of their absolute eosinophil cell counts and percentage of eosinophils.

RESULTS

Forty-one point seven per cent of patients with psoriasis had peripheral blood eosinophilia compared with 58.1% of the patients with drug eruption and 11.8% of patients with basal cell carcinoma. The percentage of patients with eosinophilia both in patients suffering from psoriasis and drug eruption were significantly increased compared with the patients with basal cell carcinoma (P < 0.001). The absolute median eosinophil cell counts both in patients with psoriasis and drug eruption were also significantly differed from patients with basal cell carcinoma (259.2, 439.1 and 183.1, respectively; P < 0.001)

CONCLUSIONS

Peripheral blood eosinophilia seems to be associated with severe forms of psoriasis. This finding may suggest that the eosinophils have significant roles in the pathogenesis of these types of psoriasis.

Eosinophil cationic protein and chemokines in nasopharyngeal secretions of infants with respiratory syncytial virus (RSV) bronchiolitis and non-RSV bronchiolitis

Bronchiolitis is a risk factor for the development of childhood asthma. Eosinophilic inflammation in airways plays an important role in the pathophysiology of both bronchiolitis and asthma. To investigate this inflammation, we measured the eosinophil cationic protein (ECP), regulated on activation normal T-cell expressed and secreted (RANTES) and eotaxin levels in nasopharyngeal secretions (NPS). Twenty-eight patients with RSV bronchiolitis (RSV group), 11 patients with non-RSV bronchiolitis (non-RSV group) and 7 controls were enrolled in this study. ECP, RANTES, and eotaxin levels were measured by enzyme immunoassays. The ECP level in the NPS of the RSV group was significantly higher than that in the NPS of the non-RSV group and controls. RANTES and eotaxin levels in infants with bronchiolitis were significantly higher than those in the controls, but there was no significant difference between the RSV and non-RSV groups. In conclusion, with regard to eosinophilic airway inflammation, as compared with non-RSV bronchiolitis, RSV bronchiolitis may be more similar to childhood asthma.

Age and sex as factors of response to RSV infections among those with previous history of wheezing

Although enhanced immune reaction caused by the respiratory syncytial virus (RSV) in allergen-sensitized animal model has been reported, RSV illnesses in children already sensitized or having recurrent wheezing episodes have not been completely studied. In addition, the reason for male dominances in RSV infection at young ages was also inconclusive. Therefore, gender analysis in recurrent wheezing children with RSV infection can shed light on asthma pathogenesis. We studied the clinical features and the laboratory data of RSV infections in children who had recurrent wheezing histories. The subjects with RSV infection consisted of 98 boys and 58 girls. The children under 4 yr of age were 123 (78.8%) in number. Children with pneumonia were 78 and those with febrile episode were 119. Children above 1 yr of age were highly sensitized with mite antigen (75/96, 78.1%). The clinical symptoms and signs differed according to their ages. Children in each age group behaved differently in their immune reaction to RSV. Above all, 3-yr-old children deteriorated clinically during acute RSV infection, accompanied by transient elevated C-reactive protein (CRP) and suppressed blood eosinophil counts. Clinical features differed in several points between boys and girls. In general, the white blood cell count and the CRP levels were higher in girls in every age group. Blood eosinophil counts at the acute illness were significantly higher in boys than girls aged 2 and 3< yr. Age and gender comparison in already sensitized children might suggest a clue to asthma pathogenesis.

Gender analysis in acute bronchiolitis due to respiratory syncytial virus

It is reasonable to compare immune reactions between boys and girls because many infections in the early stages are predominant in males. A relationship between immunomodulatory effects of sex hormone surge in boys at early months and infectious diseases is still unclear. We compared clinical features between boys and girls who suffered from wheezing that was initially triggered by acute respiratory syncytial virus (RSV) bronchiolitis. For systemic immune response evaluation, white blood cell (WBC) count, blood eosinophil count, and serum C-reactive protein (CRP) were measured. For local inflammation evaluation, scores for eosinophils and neutrophils in sputum were evaluated microscopically. Patients consisted of 90 boys and 51 girls. Most children were under 6 months of age. WBC counts and serum CRP levels were significantly increased in girls compared with boys. Blood eosinophilia at the acute stage was rarely observed in children after 6 months of age. For local response evaluation, sputum specimens obtained from 42 boys and 29 girls were microscopically examined. Sputum eosinophil score of 2+ and more was observed in boys (6/42) exclusively. In contrast, sputum neutrophilia was commonly observed in boys and girls. From a follow-up study, we confirmed that 28 children with RSV bronchiolitis showed wheezing episodes afterwards. However, their blood and sputum eosinophilia during RSV bronchiolitis did not reflect their subsequent wheezing. We speculated that gender-specific responses to RSV infection might account for male susceptibility. Differences in RSV pathogenicity between boys and girls should be further investigated in terms of asthma progression.

Human parainfluenza virus 3 neuraminidase activity contributes to dendritic cell maturation

Mechanisms of dendritic cells (DCs) immunomodulation by parainfluenza viruses have not been characterized. We analyzed whether the human parainfluenza 3 (HPF3) virus hemagglutinin-neuraminidase glycoprotein (HN) might influence DC maturation. HN possesses a receptor binding function and a neuraminidase or desialidating activity. To assess whether the neuraminidase activity of HN affects DC maturation, human myeloid DCs were exposed to either live or UV-inactivated HPF3 viruses containing wild type or a mutated form of HN with decreased neuraminidase activity. Exposure of human DCs to either UV-inactivated or live virus induced up-regulation of CD83 and CD86 surface markers, morphological changes, and a cytokine expression pattern consistent with maturation. However, the level of maturation was found to be lower in DCs infected with the neuraminidase deficient variant as compared to the wild type. These results suggest that during the course of viral infection, HN's neuraminidase activity may play an important role contributing to maturation and activation of DCs.

Respiratory syncytial virus and other respiratory viruses during the first 3 months of life promote a local TH2-like response

BACKGROUND

Respiratory syncytial virus (RSV) infections during infancy are considered to be a risk factor for developing asthma and possibly allergic sensitization.

OBJECTIVE

The aim of this study was to investigate the cytokines, chemokines, and eosinophil cationic protein in the nasopharyngeal secretions of infants < or = 7 months of age with RSV infections or other respiratory viral infections and healthy infants as controls. Groups were also analyzed according to age, < or = 3 months and >3 months, and the levels were compared within and between groups.

RESULTS

Thirty-nine infants with RSV, 9 with influenza or parainfluenza virus infections and 50 controls with no history of infections, were enrolled in the study. The RSV-infected infants had significantly higher levels of IL-4; macrophage inflammatory protein 1beta, a chemoattractant for T cells; and eosinophil cationic protein in nasopharyngeal secretions compared with the control group. The levels of the TH2 cytokine IL-4 were significantly higher in RSV-infected infants < or = months of age compared with RSV-infected infants >3 months of age. In infants < or = 3 months of age, infections with influenza or parainfluenza virus caused TH2-like responses similar to those produced by RSV.

CONCLUSION

Infections with RSV as well as with influenza and parainfluenza virus during early infancy preferentially promote a TH2-like response in the nose with local production of IL-4, IL-5, and macrophage inflammatory protein 1beta and infiltration and activation of eosinophils.

Inflammatory profile in nasal secretions of infants hospitalized with acute lower airway tract infections

OBJECTIVE

The aim of this study was to determine whether the regulatory immune response (interleukin (IL)-10 response) differed between children hospitalized with acute respiratory infections and wheezing.

METHODOLOGY

Infants with signs and symptoms of acute viral respiratory infection, admitted during winter 2000 to Princess Margaret Hospital for Children, Perth, WA, Australia, were enrolled in this study. Nasopharyngeal aspirates were collected in the first 48 h of admission. Total cell count and differential cell counts were assessed. Samples were tested for the presence of respiratory viruses. The concentrations of the anti-inflammatory cytokine IL-10, and pro-inflammatory cytokines IL-8, interferon-gamma, and IL-11 were determined by ELISA.

RESULTS

Children with acute bronchiolitis (AB; n = 36), recurrent wheeze (RW; n = 17) and upper respiratory infection (URI; n = 18) were enrolled. Respitory syncytial virus was the most commonly detected virus in all groups. IL-10 concentrations were significantly increased in AB (median, 0.019 ng/mL) when compared to URI (median, 0.006 ng/mL) or to RW (median, 0.007 ng/mL; P < 0.05). Neutrophils were the predominant cells in the cytological analysis in all subjects.

CONCLUSION

These data argue that host-response factors are important in determining the clinical phenotype, independent of the causative virus.

Eosinophil activation and cysteinyl leukotriene production in infants with respiratory syncytial virus bronchiolitis

BACKGROUND

It has been suggested that acute infantile bronchiolitis associated with respiratory syncytial virus (RSV) may share some pathogenic features with atopic asthma in that virus-specific IgE is produced and cysteinyl leukotrienes (cLTs) and eosinophil cationic protein (ECP) have been detected in airway secretions. ECP is a specific marker of eosinophil activation although leukotrienes can be released from a variety of cells including mast cells, eosinophils and monocytes.

OBJECTIVE

To test the association between eosinophil activation and cysteinyl leukotriene production in the upper airway secretions of infants with RSV positive (RSV+ve) bronchiolitis.

METHODS

Nasal lavage samples were performed in 78 infants (0.0-11.5 months) admitted to hospital with RSV+ve bronchiolitis soon after admission (0-48 h). Leukotriene C4 (LTC4) was assayed by enzyme immunoassay (EIA) and eosinophil cationic protein (ECP) by fluoroimmunoassay (FIA).

RESULTS

LTC4 was detectable in 51 and ECP in 57 of 78 samples with a significant positive relationship between LTC4 and ECP (r=0.557, P<0.001).

CONCLUSION

In the majority of our subjects with RSV+ve bronchiolitis ECP and LTC4 were detectable in upper airway secretions and were significantly associated with each other. In this clinical setting much of the detected LTC4 within upper airway secretions is likely to originate from the eosinophil, an observation that may have implications for clinical management and for delineation of the underlying mechanisms associated with this illness.

Prior airway exposure to allergen increases virus-induced airway hyperresponsiveness

BACKGROUND

Respiratory syncytial virus (RSV) bronchiolitis in early life can lead to changes in airway function, but there are likely additional predisposing factors, such as prior allergen exposure, determining which children develop wheezing and asthma.

OBJECTIVE

To define the effects of prior airway exposure to sensitizing allergen on the development of airway inflammation and hyperresponsiveness (AHR) to subsequent RSV infection.

METHODS

BALB/c mice were exposed to ovalbumin or PBS exclusively through the airways and subsequently infected with RSV or sham-inoculated. AHR, lung inflammation, and the frequency of cytokine-producing T lymphocytes in the lung were determined.

RESULTS

In PBS-exposed mice, RSV infection induced AHR and an increased proportion of TH1-type (IFN-gamma and IL-12) cytokine-producing cells in the lungs. However, in mice previously exposed to ovalbumin through the airways and subsequently infected with RSV, the degree of AHR was significantly increased and was associated with an increased proportion of TH2 (IL-4, IL-5) cytokine-producing T lymphocytes. This response was also associated with an increased accumulation of eosinophils, neutrophils, and CD8+ T cells in the lungs.

CONCLUSIONS

These data suggest that prior airway exposure to allergen may predispose sensitized hosts to a greater degree of altered airway function upon subsequent respiratory viral infection.

RSV-induced bronchiolitis but not upper respiratory tract infection is accompanied by an increased nasal IL-18 response

The aim of this study was to investigate potential differences in the local nasal immune response between bronchiolitis and upper respiratory tract infection induced by respiratory syncytial virus (RSV). Nasal brush samples were obtained from 14 infants with RSV bronchiolitis and from 8 infants with RSV upper respiratory tract infection. The samples were taken during infection (acute phase) and 2-4 weeks later (convalescent phase). Cytospin preparations were stained immunohistochemically for T cells, macrophages, and eosinophils. Staining also took place for intercellular adhesion molecule-1 (ICAM-1), T-helper 1 (Th1)-like (interleukin-12 [IL-12], interferon-gamma [IFN-gamma]), Th2-like (IL-4, IL-10), and proinflammatory cytokines (IL-6, IL-8, IL-18). During both RSV-induced bronchiolitis and upper respiratory tract infection, cellular inflammation was observed. This was characterised by an increase in the numbers of nasal macrophages, which tended to be higher in bronchiolitis than in upper respiratory tract infection. Numbers of T lymphocytes and ICAM-1 positive cells increased during both bronchiolitis and upper respiratory tract infection. There were no differences between numbers in the groups. Interestingly, a distinct nasal proinflammatory cytokine response was observed in RSV-induced bronchiolitis. This is characterised by an increase in the number of IL-18 positive cells. This increase is specific for bronchiolitis, as a similar increase could not be detected in RSV-induced upper respiratory tract infection. Numbers of IL-6 and IL-12 positive cells were higher in both bronchiolitis and upper respiratory tract infection, and there were no differences between the groups. By contrast, the number of IL-8, IFN-gamma, IL-4, and IL-10-positive cells remained constant. In conclusion, clear differences were found in nasal immune responses of children with RSV-induced upper respiratory tract infection or bronchiolitis. The induction of a strong IL-18 response was typical for bronchiolitis, as this could not be observed in RSV-induced upper respiratory tract infection, and could explain the eosinophilia that is observed frequently during bronchiolitis.

The complex relationship between respiratory syncytial virus and allergy in lung disease

Epidemiologic studies suggest a strong link between severe respiratory syncytial virus (RSV)-induced bronchiolitis in infancy and allergic disease; however, the mechanisms determining this relationship are currently unknown. In this review article, we summarize data from human clinical studies that explore the association between RSV infection and allergy, some that suggest that RSV bronchiolitis requiring hospitalization leads to an increased incidence of the allergic phenotype and others that suggest that pre-existing allergy is a risk factor for severe RSV bronchiolitis. We also review the published murine models that combine RSV infection and allergic sensitization that attempt to explain the complex relationship between these two factors in regard to lung immunopathology and physiologic dysfunction.

Identification of immunodominant epitopes derived from the respiratory syncytial virus fusion protein that are recognized by human CD4 T cells

Memory CD4 T-cell responses against respiratory syncytial virus (RSV) were evaluated in peripheral blood mononuclear cells of healthy blood donors with gamma interferon enzyme-linked immunospot (Elispot) assays. RSV-specific responses were detected in every donor at levels varying between 0.05 and 0.3% of CD4 T cells. For all donors tested, a considerable component of the CD4 T-cell response was directed against the fusion (F) protein of RSV. We characterized a set of 31 immunodominant antigenic peptides targeted by CD4 T cells in the context of the most prevalent HLA class II molecules within the Caucasian population. Most antigenic peptides were HLA-DR restricted, whereas two dominant DQ peptides were also identified. The antigenic peptides identified were located across the entire sequence of the F protein. Several peptides were presented by more than one major histocompatibility complex class II molecule. Furthermore, most donors recognized several F peptides. Detailed knowledge about immunodominant antigenic peptides will facilitate the ability to monitor CD4 T-cell responses in patients and the measurement of correlates of protection in vaccinated subjects.

The association between persistent eosinophilia and asthma in childhood is independent of atopic status

BACKGROUND

Although peripheral blood eosinophilia is associated with risk of asthma, the relation with atopy has not been established.

OBJECTIVE

To assess the relationship between eosinophils and chronic asthma in childhood, and to determine the factors associated with eosinophil levels over time.

METHODS

Percent eosinophils/300 white blood cell (WBC) count ('eos') was measured at 9 months, 6 years and 11 years in subjects participating in the prospective Tucson Children's Respiratory Study. Children were classified based on the number of measurements in which they had low (< or = 2%) or high (>5%) eosinophils, as follows: (1) Persistently low eos (n = 130); (2) Low eos (intermittently low or consistently moderate, but never high, n = 317); (3) Intermittently high eos (n = 192); and (4) Persistently high eos (n = 17). Only children with > or = 2 eos measurements were included in the analysis. Chronic asthma was defined as medical doctor (MD)-diagnosed asthma with reports of wheezing during the previous year, on > or = 3 questionnaires completed between 2 and 13 years of age. Children with at least one positive skin prick test (SPT; > or = 3 mm) at age 6 or 11 were considered 'atopic'.

RESULTS

Chronic asthma was linearly related to longitudinally ascertained eosinophils (trend chi2 P<0.001) with prevalence ranging from 5.8% among children with persistently low eos to 37.5% among children with persistently high eos. This relation was independent of atopy. Parental history of asthma was associated with both chronic asthma (P <0.001) and with longitudinal eosinophil status (P < 0.001). After adjusting for atopy and gender, there was a 70% increase in asthma risk with each increase in longitudinal eosinophil level. This stepwise increase was reduced to 48% when parental asthma was added to the model.

CONCLUSION

Longitudinal eosinophil levels are linearly associated with chronic asthma in childhood, independent of atopy. The strong association between parental asthma and eosinophil status suggests that genetic background may be an important determinant of eosinophilic response.

Eosinophil cationic protein and interleukin-8 levels in bronchial lavage fluid from children with asthma and infantile wheeze

It has been shown previously that airway eosinophils characterize childhood asthma and neutrophils contribute to the pathophysiology of both infantile wheezing and asthma. Therefore, eosinophil cationic protein (ECP) and interleukin-8 (IL-8) levels in bronchoalveolar lavage fluid (BALF) from asthmatics (n = 16) and infantile wheezers (n = 30) were analyzed as markers of eosinophil- and neutrophil-mediated inflammation. To aid the interpretation, a control group of children (n = 10) with no lower airway pathology were included. Disease severity was assessed by using a symptom score. Surprisingly, no significant difference was found in IL-8 or ECP levels among asthma, infantile wheeze, and control groups. Asthma was characterized by: a correlation between ECP levels and eosinophil counts (r = 0.618, p = 0.014); a correlation between neutrophil number and IL-8 levels (r = 0.747, p = 0.002); and increasing IL-8 levels with symptom score (p = 0.03). In infantile wheezers, IL-8 levels were poorly related to neutrophil number but were significantly increased when neutrophils were > 10%. Although detectable levels were found in all but one symptomatic infant, IL-8 concentrations did not reflect the symptom score in infantile wheeze. ECP was unexpectedly correlated to neutrophil percentages (Rho = 0.832, p = 0.001), and a threshold of ECP>20 ng/ml was associated with persistent symptoms in these infantile wheezers. Hence, in accordance with BALF cellularity, activation of eosinophils was suggested by raised levels of ECP in childhood asthma, but not in infantile wheeze. Neutrophil-mediated inflammation appeared to better reflect the severity of asthma than that of infantile wheeze. Although its meaning remains to be elucidated, ECP was suggested to be a helpful indicator of persistent infantile wheeze. However, its utility as a marker predicting ongoing asthma remains to be established.

Role of interferon gamma in the pathogenesis of primary respiratory syncytial virus infection in BALB/c mice

Immunologic mechanisms are thought to contribute to the pathogenesis of respiratory syncytial virus (RSV) bronchiolitis in humans. RSV-infected BALB/c mice exhibit tachypnea and signs of outflow obstruction, similar to symptoms in humans. Interferon gamma (IFNgamma) has been found to be the predominant cytokine produced in humans and mice with RSV infection. We therefore undertook this study to evaluate the role of IFNgamma in the development of respiratory illness in RSV-infected mice. BALB/c mice were infected with RSV, and lung function was assessed by plethysmography. Bronchoalveolar lavage (BAL) fluids were analyzed for the concentration of interferon gamma (IFNgamma) and the presence of inflammatory cells, and lung tissue sections were examined for histopathologic changes. The role of IFNgamma was further addressed in studies of IFNgamma knock-out mice (IFNgamma(-/-)) and of mice depleted of IFNgamma by in vivo administration of a neutralizing antibody. After infection, mice developed respiratory symptoms that were strongly associated with the number of inflammatory cells in BAL, as well as with the concentrations of IFN-gamma. Both IFN-gamma(-/-) mice and mice treated with anti-IFNgamma developed more extensive inflammation of the airways than control mice. However mice lacking IFNgamma exhibited less severe signs of airway obstruction. Together these data suggest a protective role of IFNgamma in RSV infection in terms of limiting viral replication and inflammatory responses but also a pathogenic role in causing airway obstruction.

Allergen challenge-induced acute exudation of IL-8, ECP and alpha2-macroglobulin in human rhinovirus-induced common colds

Rhinovirus infections cause exacerbations of eosinophilic airway disease. The acute effects of allergen‐challenge on nasal interleukin‐8 (IL‐8), eosinophil cationic protein (ECP), and α₂‐macroglobulin were examined in atopic subjects with common cold symptoms.

Twenty‐three patients with seasonal allergic rhinitis were inoculated with human rhinovirus 16 outside the pollen season. Diluent and allergen challenges, followed by nasal lavages, were carried out about 3 months before and 4 days after virus inoculation.

Seventeen patients developed significant common cold symptoms with increased nasal lavage fluid levels of α₂‐macroglobulin, IL‐8, and ECP at baseline (p<0.001–0.05 versus before inoculation), and were further increased by allergen challenge (p<0.001–0.05); IL‐8 and ECP levels were correlated (r=0.63, p<0.001). Before inoculation, the six patients who later did not develop common cold symptoms had high levels of IL‐8 and myeloperoxidase (MPO), and exhibited strong allergen‐induced plasma exudation responses (α₂‐macroglobulin). After inoculation, IL‐8 and ECP did not increase in these symptomless subjects.

In conclusion, high nasal interleukin‐8 and myeloperoxidase levels and exudative hyperresponsiveness may protect against infection. The association between nasal interleukin‐8 and eosinophil cationic protein in common cold, particularly that observed in nasal lavage fluids after allergen‐induced acute exudation of plasma, suggests the involvement of interleukin‐8 in exacerbation of airway mucosal eosinophil activity.

The role of viruses in development or exacerbation of atopic asthma

Respiratory viral infections in early childhood have been linked to the development of persistent wheezing and asthma. Epidemiologic data indicate that, for the majority of children, virus-induced wheezing is a self-limited condition, with no long-term consequences. For a substantial minority, however, virus-induced wheezing is associated with persistent asthma and the potential for enhanced allergic sensitization. For the most part, this subset of patients is genetically predisposed; they are atopic children in whom respiratory viral infections trigger the early development of asthma by mechanisms that have not been fully elucidated. Both inflammatory and noninflammatory mechanisms may be involved. It does not appear that viral infection per se in early life is responsible for the induction of atopic asthma. Data from animal models provide support for the concept that enhanced allergic sensitization caused by increased uptake of allergen during infection may play a critical role, as well as T-cell-mediated immune responses to viral infection, which may favor eosinophilic inflammatory responses and the development of altered airway function to inhaled methacholine. Recent advances in our understanding of the interactions between respiratory viruses and the development of reactive airway disease offer new possibilities for preventive treatment in children at risk for developing persistent wheezing and asthma exacerbation as a result of viral infection.

Eosinophilia at the time of respiratory syncytial virus bronchiolitis predicts childhood reactive airway disease

OBJECTIVE

Bronchiolitis in infancy is viewed as a risk factor for childhood asthma, but factors predicting which infants will have persistent wheezing have not been identified. In addition, the nature of the association between the 2 conditions is uncertain. We wished to determine whether eosinophil counts at the time of acute bronchiolitis predicted the presence of wheezing in later childhood.

METHODS

We retrospectively identified infants hospitalized with bronchiolitis, determined peripheral blood eosinophil counts at the time of bronchiolitis, and then contacted their families when they had reached 7 years of age.

RESULTS

Eosinophil counts at the time of bronchiolitis were greater in subjects who would have wheezing at 7 years of age (median: 98 cells/mm(3)) than in infants who would have no recurrent wheezing (median: 0 cells/mm(3)) or transient wheezing only up to 3 years of age (median: 0 cells/mm(3)). When the effects of family history of asthma, gender, and passive exposure to cigarette smoke were examined, only eosinophilia at the time of bronchiolitis demonstrated a statistically significant relationship to the presence of wheezing at 7 years of age.

CONCLUSIONS

Eosinophilia at the time of bronchiolitis generally predicts the development of wheezing persisting into later childhood. Therefore, the association of bronchiolitis and childhood asthma seems more likely to be attributable to an immunologic anomaly that precedes the development of, or is induced by, bronchiolitis rather than to structural damage to the airway as a result of bronchiolitis.

Advances in the immunobiology of eosinophils and their role in disease

Eosinophils play a protective role in host immunity to infections by parasitic worms and, detrimentally, are involved in the pathophysiology of asthma and other allergic diseases. Airway inflammation is central to the pathology of asthma and is characterized by infiltration of the bronchial mucosa by large numbers of proinflammatory cells, amongst which the eosinophil is prominent despite being a minority constituent of circulating leukocytes. Crucial steps in eosinophilic inflammation include augmented production of eosinophils in the bone marrow, their increased release into the circulation, and their selective accumulation in the conducting airways. The eosinophil has a potent armory of proinflammatory mediators, including cytotoxic granule proteins, cytokines and lipid mediators with considerable potential to initiate and sustain an inflammatory response. Thus there is much interest in the elucidation of the mechanisms responsible for eosinophil accumulation, persistence, activation and ultimate fate. This article reviews our current understanding of the role of the eosinophil in human disease and the immunobiology of this important proinflammatory cell.

Recognizing early asthma

Asthma symptoms often develop during the first years of life. Longitudinal studies show that at least 40% of children with wheezing lower respiratory illnesses (LRIs) during the first 3 years of life still have wheezing episodes at 6 years of age. Thus, it is important to identify children at risk of developing asthma, and to distinguish these from those in whom early wheezing is likely to be transient. This is complicated, however, by the variable nature of asthma and the lack of specific and sensitive markers. Genetic markers and epidemiologic risk factors for asthma have been identified, but cannot be used to predict the development of asthma in an individual patient. Similarly, infants who subsequently develop asthma in childhood have higher serum immunoglobulin E (IgE) and peripheral eosinophil counts than those who do not develop asthma, but, again, these factors are not sufficiently sensitive and specific to allow identification of children at risk of developing asthma. An algorithm is presented that outlines possible criteria to determine the risk of developing asthma in infants.

Increased production of IFN-gamma and cysteinyl leukotrienes in virus-induced wheezing

BACKGROUND

An imbalance of production of T-helper lymphocyte cytokines, favoring overproduction of IL-4, is believed to be important in the pathogenesis of allergic asthma. However, less is known about the cytokine response in virus-induced wheezing, which is a major cause of morbidity in asthma.

OBJECTIVE

We undertook this study to determine the magnitude of IFN-gamma, IL-4 and IL-10, and leukotriene (LT) responses in infants and children with virus-induced wheezing.

METHODS

We measured the concentrations of IFN-gamma, IL-4 and IL-10, and cysteinyl LTs in respiratory secretions of 82 infants and young children during acute episodes of virus-induced wheezing. Control subjects were 47 infants and children with uncomplicated upper respiratory infections and 18 normal healthy infants.

RESULTS

Ratios of IFN-gamma to IL-4 were higher (due to increased quantities of IFN-gamma) in subjects with wheezing than in those with upper respiratory infection alone (P =. 003). Quantities of LTs were also increased in wheezing subjects in comparison with those with upper respiratory infections (P =.009). There was a significant correlation between measured concentrations of IFN-gamma and LTs (correlation coefficient =.451, P =.007). Quantities of IL-4 were slightly suppressed in the wheezing groups.

CONCLUSIONS

An imbalance favoring overproduction of IFN-gamma appears to be associated temporarily with virus-induced wheezing. A possible mechanism is the enhanced release of LTs from eosinophils or mast cells after sensitization by IFN-gamma.

IL-5 and Eosinophils Are Essential for the Development of Airway Hyperresponsiveness Following Acute Respiratory Syncytial Virus Infection

Viral respiratory infections can cause bronchial hyperresponsiveness and exacerbate asthma. In mice, respiratory syncytial virus (RSV) infection, which induces an immune response dominated by IFN-γ, results in airway hyperresponsiveness (AHR) and eosinophil influx into the airways, both of which are prevented by pretreatment with anti-IL-5 Ab. To delineate the role of IL-5, IL-4, and IFN-γ in the development of RSV-induced AHR and lung eosinophilia, we tested the ability of mice deficient in each of these cytokines to develop these symptoms of RSV infection. Mice deficient in either IL-5, IL-4, or IFN-γ were administered infectious RSV intranasally, and 6 days later, airway responsiveness to inhaled methacholine was assessed by barometric body plethysmography, and numbers of lung eosinophils and production of IFN-γ, IL-4, and IL-5 by mononuclear cells from peribronchial lymph nodes were monitored. RSV infection resulted in airway eosinophilia and AHR in both IL-4- and IFN-γ-deficient mice, but not in IL-5-deficient mice. Reconstitution of IL-5-deficient mice with IL-5 restored these responses and enhanced the responses in IL-4-deficient mice. Anti-VLA-4 (very late Ag-4) treatment prevented lung eosinophilia and AHR following RSV infection and IL-5 reconstitution. We conclude that in response to RSV, IL-5 is essential for the influx of eosinophils into the lung and that eosinophils in turn are critical for the development of AHR. IFN-γ and IL-4 are not essential for these responses to RSV infection.

Allergen challenge-induced acute exudation of IL-8, ECP and alpha2-macroglobulin in human rhinovirus-induced common colds

Rhinovirus infections cause exacerbations of eosinophilic airway disease. The acute effects of allergen-challenge on nasal interleukin-8 (IL-8), eosinophil cationic protein (ECP), and alpha2-macroglobulin were examined in atopic subjects with common cold symptoms. Twenty-three patients with seasonal allergic rhinitis were inoculated with human rhinovirus 16 outside the pollen season. Diluent and allergen challenges, followed by nasal lavages, were carried out about 3 months before and 4 days after virus inoculation. Seventeen patients developed significant common cold symptoms with increased nasal lavage fluid levels of alpha2-macroglobulin, IL-8, and ECP at baseline (p<0.001-0.05 versus before inoculation), and were further increased by allergen challenge (p< 0.001-0.05); IL-8 and ECP levels were correlated (r = 0.63, p<0.001). Before inoculation, the six patients who later did not develop common cold symptoms had high levels of IL-8 and myeloperoxidase (MPO), and exhibited strong allergen-induced plasma exudation responses (alpha2-macroglobulin). After inoculation, IL-8 and ECP did not increase in these symptomless subjects. In conclusion, high nasal interleukin-8 and myeloperoxidase levels and exudative hyperresponsiveness may protect against infection. The association between nasal interleukin-8 and eosinophil cationic protein in common cold, particularly that observed in nasal lavage fluids after allergen-induced acute exudation of plasma, suggests the involvement of interleukin-8 in exacerbation of airway mucosal eosinophil activity.

Eosinophils and basophilic cells in sputum and nasal smears taken from infants and young children during acute asthma

To examine the increase in eosinophils and basophilic cells in the respiratory areas of infants and young children with asthma (n = 111), we analyzed the numbers of eosinophils and basophilic cells in sputum and nasal smears. The number of children with eosinophilia grades of 2+ or greater (> or = 11 cells/five fields in x1000 magnification) in sputum and nasal smears, respectively, in each age group was as follows: 33% and 21% under 1 year, 59% and 64% at 1 year, and 79-80% and 75-78% at 2-3 years. An increased infiltration of basophilic cells according to age was also observed. Infiltration of these cells began earlier than the appearance of IgE antibodies to mite in blood.

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.