Mechanism of perennial allergic asthma

Efficacy and Safety of Diethylcarbamazine in Treatment of Allergic Rhinitis: A Double Blind Randomised Controlled Trial

There are many evidences showing diethylcarbamazine as a potential drug for the treatment of allergic rhinitis. This study evaluated the effectiveness of diethylcarbamazine in the treatment of allergic rhinitis and compared it with montelukast and levocetirizine. This parallel double-blind randomized clinical trial was done in allergic rhinitis patients. Seven hundred and twelve participants who met the inclusion criteria and provided informed written consent were randomized and divided into 2 equal groups. Diethylcarbamazine 300 mg/day orally in divided doses was given to group A, and montelukast 10 mg and levocetirizine 5 mg/day orally at night for 21 days was given to group B. Primary outcomes were the change in symptoms, absolute eosinophil count, serum total IgE, phadiatop and response in skin prick from baseline to 21 days and 3 months after treatment. Secondary outcome was to compare it with montelukast and levocetirizine. The mean (SD) age of the patients was 33 (10.6) years, with 374 (52.5%) males and 338 (47.5%) females. There was statistically significant improvement in all the parameters in both groups. Improvement was better with diethylcarbamazine compared to montelukast and levocetirizine and the effects were sustained for 3 months in diethylcarbamazine group. The findings suggest that diethylcarbamazine is effective in the treatment of allergic rhinitis. It gives better control and is cost-effective than montelukast and levocetirizine. Trial Registration: https://www.ctri.nic.in Identifier: CTRI/2020/03/024145 registered on 20-03-2020.

Satellite Monitoring for Air Quality and Health

Data from satellite instruments provide estimates of gas and particle levels relevant to human health, even pollutants invisible to the human eye. However, the successful interpretation of satellite data requires an understanding of how satellites relate to other data sources, as well as factors affecting their application to health challenges. Drawing from the expertise and experience of the 2016-2020 NASA HAQAST (Health and Air Quality Applied Sciences Team), we present a review of satellite data for air quality and health applications. We include a discussion of satellite data for epidemiological studies and health impact assessments, as well as the use of satellite data to evaluate air quality trends, support air quality regulation, characterize smoke from wildfires, and quantify emission sources. The primary advantage of satellite data compared to in situ measurements, e.g., from air quality monitoring stations, is their spatial coverage. Satellite data can reveal where pollution levels are highest around the world, how levels have changed over daily to decadal periods, and where pollutants are transported from urban to global scales. To date, air quality and health applications have primarily utilized satellite observations and satellite-derived products relevant to near-surface particulate matter <2.5 μm in diameter (PM_2.5) and nitrogen dioxide (NO₂). Health and air quality communities have grown increasingly engaged in the use of satellite data, and this trend is expected to continue. From health researchers to air quality managers, and from global applications to community impacts, satellite data are transforming the way air pollution exposure is evaluated.

Nasal Challenge, Skin Tests, and Serum Antibodies in the Diagnosis of Latex-Induced Occupational Rhinitis

The purpose of the study was to develop a suitable natural rubber latex (NRL) antigen powder and a control material for the nasal application of the test reagent and to evaluate the nasal provocation test (NPT) response pattern in latex allergic and nonlatex allergic subjects with a suspicion of latex-induced rhinitis. A questionnaire was completed among health care workers (n = 268) in one hospital. Seven health care workers who had upper respiratory symptoms associated with daily usage of latex gloves were examined by using skin prick test (SPT), NPT, and sinus plain X-ray. NRL allergen for the nasal challenge was collected from surgical gloves. The powder was obtained by washing the gloves, freeze-drying the solution, and the powder was then used in NPT. As a negative control, clean corn starch powder was applicated on nasal mucous. SDS-PAGE analysis of the NRL test powder was performed. After the nasal challenge, one of seven workers showed rhinorrhea, a significant increase in nasal obstruction, and in the amount of nasal secretion in NPT. This patient also showed a positive SPT to NRL allergens and an elevated NRL specific IgE level in her serum. In six patients NPT, SPT, and specific IgE for latex were negative. SDS-PAGE analysis of the glove powder showed a major NRL antigen, with molecular weight of 14 kDa. The NPT may be used in persons with a suspicion of latex-induced rhinitis and borderline skin and humoral test results for NRL and in subjects with heavy glove powder-associated nasal symptoms but negative skin and humoral tests for latex. Only well known test reagents should be used in NPT.

Inhaled allergen bronchoprovocation tests

The allergen bronchoprovocation test is a long-standing exacerbation model of allergic asthma that can induce several clinical and pathophysiologic features of asthma in sensitized subjects. Standardized allergen challenge is primarily a research tool, and when properly conducted by qualified and experienced investigators, it is safe and highly reproducible. In combination with validated airway sampling and sensitive detection techniques, allergen challenge allows the study of several features of the physiology of mainly TH2 cell-driven asthma in relation to the kinetics of the underlying airway pathology occurring during the allergen-induced late response. Furthermore, given the small within-subject variability in allergen-induced airway responses, allergen challenge offers an adequate disease model for the evaluation of new (targeted) controller therapies for asthma in a limited number of subjects. In proof-of-efficacy studies thus far, allergen challenge showed a fair positive predicted value and an excellent negative predictive value for the actual clinical efficacy of new antiasthma therapies, underscoring its important role in early drug development. In this review we provide recommendations on challenge methods, response measurements, sample size, safety, and harmonization for future applications.

Phosphodiesterase inhibitors: history of pharmacology

The first pharmacological investigations of phosphodiesterase (PDE) inhibitors were developed with the clinical efficacies of drugs isolated from coffee, cacao and tea but only later their relevant ingredients were identified as xanthines that act as PDE. With its diuretic, inotropic and bronchodilating clinical efficacy, use of theophylline anticipated the clinical goals, which were later approached with the first-generation of weakly selective PDE inhibitors in the period from 1980 to 1990. Pharmacological and clinical research with these early compounds provided a vast pool of information regarding desired and adverse actions - although most of these new drugs had to be discontinued due to severe adverse effects. The pharmacological models for cardiac, vascular and respiratory indications were analysed for their PDE isoenzyme profiles, and when biochemical and molecular biological approaches expanded our knowledge of the PDE superfamily, the purified isoenzymes that were now available opened the door for more systematic studies of inhibitors and for generation of highly selective isoenzyme-specific drugs. The development of simple screening models and clinically relevant indication models reflecting the growing knowledge about pathomechanisms of disease are summarised here for today's successful application of highly selective PDE3, PDE4 and PDE5 inhibitors. The interplay of serendipitous discoveries, the establishment of intelligent pharmacological models and the knowledge gain by research results with new substances is reviewed. The broad efficacies of new substances in vitro, the enormous biodiversity of the PDE isoenzyme family and the sophisticated biochemical pharmacology enabled Viagra to be the first success story in the field of PDE inhibitor drug development, but probably more success stories will follow.

Nasal histamine reactivity among adolescents in a remediated moisture-damaged school--a longitudinal study

In a previous study, in the spring of 1995, we found that teachers, who had been working for several years in a moister-damaged school, 1 year after the renovation still reported a higher frequency of complaints and symptoms and showed significantly higher mucosal histamine reactivity compared with teachers in a control school, although the school seemed to be properly renovated. A longitudinal study of 90 randomly selected senior high school students entering the two schools was initiated to exclude or verify if the indoor air still exerted an irritant effect on the upper airways of an earlier unexposed group. The students went through a nasal histamine provocation test and answered a questionnaire on three occasions, in 1995, 1996 and 1997. No significant differences in the nasal histamine provocation curves for the students at the target school and those at the control school could be shown from start to endpoint of the study period. Neither was there any differences concerning perceived indoor air or mucosal symptoms between the target and the control group and technical measurements showed no noteworthy differences between the two schools. In conclusion, this study indicates that based on both technical and objective medical measures, the current indoor air in the remediated moisture-damaged school does not exert an irritant effect on the upper airway mucosa of the students. A 2-year follow-up of the teachers showed a decreased reactivity to histamine, giving further support to this statement. The increased mucosal reactivity observed among the teachers is probably a result of the previous long-term exposure to building dampness. No differences were seen between atopic and non-atopic students.

PRACTICAL IMPLICATIONS

Persistent symptoms and increased nasal mucosal reactivity among personnel in a remediated damp building does not necessary imply an inadequate renovation. A longitudinal study with registration of subjective (questionnaires) and objective (nasal histamine reactivity) data of an earlier unexposed group residing in the same building further contributes to the evaluation whether the renovation was successful or not.

Selenium serum and urine is associated to mild asthma and atopy. The SUS study

To examine the associations between selenium (Se) status, asthma, bronchial hyperresponsiveness (BHR), and atopy in 154 male subjects (72 with mild asthma, 41 with BHR and 41 with no respiratory symptoms) aged 18 (range 17-22) years. Each subject underwent a medical interview and FEV1 and FVC were recorded. Histamine bronchial reactivity (Yan method) was measured, skin prick test (inhalant allergens) was performed and Se in urine and serum was analysed (AOAC modified fluometric method). Se in serum 74.04 (10.58) micrograms/L (mean (SD)) was lower in subjects with asthma and the logarithm of the ratio of Se in serum (microgram/L) and urine standardised to creatinine excretion (ng/mg creatinine) 0.748 (0.096) (mean (SD)) was lower in subjects with asthma and atopy compared to subjects with no allergic symptoms 77.79 (10.16) micrograms/L and 0.808 (0.111) respectively (p < 0.05). In subjects with asthma atopy was significantly associated to urine Se 0.24 (0.73) (beta (SE)) (p < 0.05). Subjects with BHR had the same Se status as subjects with no respiratory symptoms and heavy smokers had a lower concentration of Se in serum 73.80 (9.56) micrograms/L than non-smokers 78.16 (10.74) micrograms/L (p < 0.05), Se status was associated to asthma and smoking. Measuring Se in urine might add further information to possible relations between Se status, atopy and asthma.

Wheezing as the sole clinical manifestation of cor triatriatum

Cardiac malformations involving low-pressure chambers (i.e., either of the atria) are more often diagnosed later in life than lesions that involve high-pressure systems such as ventricular septal defects or persistent ducti arteriosi. Patients with congenital heart disease involving the atria may present only symptoms suggesting lung disease. We report on a child with recurrent episodes of wheezing, which did not respond to albuterol nebulizations and intravenous corticosteroids; he was subsequently found to have cor triatriatum. When a patient suffers from recurrent episodes of lower pulmonary infection and wheezing, despite appropriate management for asthma, less common (including cardiac) causes should be considered.

Antigen-induced airway inflammation and hyper-responsiveness does not enhance airway responses to a subsequent antigen challenge in rats

Brown-Norway (BN) rats develop airway hyper-responsiveness and lung eosinophilia 18-24 h after ovalbumin (OA) challenge. We hypothesized therefore that allergen-induced airway inflammation would further enhance airway responses to a subsequent antigen challenge. Animals were sensitized to both OA and bovine serum albumin (BSA) and, 14 days later, challenged by aerosols with both antigens 24 h apart. Measurements of pulmonary resistance (RL) were made for 8 h after the second antigen challenge and bronchoalveolar lavage (BAL) was performed. Animals were divided into three groups and received two challenges as follows: saline-BSA (n=9), OA-saline (n=8) and OA-BSA (n=10). Sensitization was confirmed by measurements of specific OA-IgE and BSA-IgE. Early responses [determined as the highest value of RL within the first 30 min after the challenge] were absent in all study groups. The late responses [determined from the area under the RL versus time curve from 120 to 480 min after the challenge] were significantly greater in animals challenged with BSA (15.16+/-3.86) compared to saline (3.76+/-4.09; P<0.05). However previous exposure to OA did not further increase the late response in animals subsequently challenged with BSA (20.11+/-3.67) despite enhanced airway responsiveness to LTD4 at this time point. BAL eosinophils and lymphocytes were significantly increased following BSA challenge in previously OA-challenged animals, compared to numbers retrieved from animals previously exposed to saline (P<0.05). These data indicate that previous exposure to OA did not further increase the LR to a second antigen challenge despite substantial increases in airway inflammatory cells and airway hyper-responsiveness to LTD4.

Inhibition of airway inflammation in rDer f 2-sensitized mice by oral administration of recombinant der f 2

Recombinant Der f 2 (rDer f 2) is a promising new allergen expected to improve the diagnosis and immunotherapy of house dust mite allergy and to further immunological studies. To evaluate the hyposensitizing activity of rDer f 2 to mite allergy, we examined the effect of its oral administration on allergic inflammation in A/J mice immunized with mite allergens. A/J mice immunized with rDer f 2 alone or rDer f 2 + crude mite extract were orally given 0 (control), 0.01, 0.1, or 1 mg/day of rDer f 2 for 4 weeks, followed by an antigen inhalation challenge. Twenty-four hours after rDer f 2 inhalation, control animals experienced severe leukocyte influx into the airway. The infiltrating cells were mainly neutrophils, with some eosinophils and lymphocytes. The concentrations of IL4, IFNgamma, and soluble ICAM-1 in the bronchial alveolar lavage fluid increased twofold compared with values before rDer f 2 inhalation. In contrast, inflammation was significantly suppressed in mice given 1 mg/day of rDer f 2 orally for 4 weeks and partially suppressed in those fed 0.1 mg/day of the antigen. Plasma anti-rDer f 2 antibody levels were unchanged by oral rDer f 2 treatment. Mite extract inhalation challenge provoked neutophilia in rDer f 2 + mite-sensitized control mice, and this allergic reaction tended to decrease in sensitized mice fed 1 mg/day of rDer f 2 orally for 4 weeks. We conclude that rDer f 2 has hyposensitizing activities and may be useful in immunotherapy for house dust mite allergy.

A preceding airway reaction to one allergen may lead to priming of the airway responses to another allergen

This study aimed to determine whether a preceding airway response to one allergen leads to priming of the airway responses to another allergen. Twelve asthmatic children who had positive prick tests to two allergens, Dermatophagoides pteronyssinus (D.p.) and German cockroach (CR), participated in a randomized, placebo-controlled crossover study. We performed two consecutive inhalation challenges, D.p. challenge being followed 48 h later by CR challenge. The effect of initial (D.p.) challenge on the early and late airway responses to the subsequent (CR) challenge (CR2) was examined by comparing the responses with those to CR challenge preceded by sham challenge (CR1). The geometric mean PD20 of CR allergen in the CR2 was 2.8 BU (breath unit) (range of 1 SD; 0.77-10.4), which was 12.0-fold less than that (33.7 BU, 10.8-105.2) in the CR1. The administration of a 6.1-fold less dose (8.9 BU, 2.7-28.8) in the CR2 than in the CR1 (54.5 BU, 44.1-69.3) provoked a similar degree of late-phase reactions (18.7 +/- 7.3% vs 15.8 +/- 9.6%). Our data indicated that the early- and late-phase reactions to CR challenge were augmented by the preceding reaction to D.p. This suggests that a preceding airway response to one allergen may lead to priming, with enhancement of the early and late airway responses to the subsequent challenge with another allergen.

Nasal responsiveness to allergen and histamine in patients with perennial rhinitis with and without a late phase response

BACKGROUND

In the lower airways an association has been found between early phase reaction (EPR), late phase reaction (LPR), and bronchial hyperreactivity. However, this association has not been shown for the upper airways in nasal pollen challenge studies. A study was undertaken to determine whether the EPR, LPR, and nasal hyperreactivity are related in perennial allergic rhinitis.

METHODS

Twenty four patients with rhinitis who were allergic to house dust mite (HDM) were challenged with HDM extract. The nasal response was monitored by symptom scores and nasal lavages for up to 9.5 hours after challenge and concentrations of albumin, tryptase, and eosinophil cationic protein (ECP) in the lavage fluid were measured. Thirteen patients (defined as dual responders) had increased symptom scores between 3.5 and 9.5 hours compared with the baseline score. The other 11 patients (defined as early responders) showed an isolated EPR only. Nasal hyperreactivity was determined by nasal histamine challenge 24 hours later.

RESULTS

Dual responders showed a significantly higher symptom score, albumin influx, and tryptase release during the EPR. During the late phase (3.5-9.5 hours) albumin influx was significantly increased at most time points and ECP release was significantly higher at 9.5 hours in the dual responder group. Dual responders showed a significantly stronger response to all doses of histamine. The area under the curve (AUC) of symptom scores during EPR and LPR and the AUC of the histamine dose response were significantly correlated (EPR-LPR: r = 0.49, p < 0.01; EPR-histamine: r = 0.75, p < 0.001; LPR-histamine: r = 0.66, p < 0.001).

CONCLUSIONS

In patients with perennial allergic rhinitis the nasal responses to allergen and histamine are associated. Dual responders have an increased EPR, increased levels of mediators, and increased allergen-induced hyperreactivity.

A major outbreak of asthma associated with a thunderstorm: experience of accident and emergency departments and patients' characteristics. Thames Regions Accident and Emergency Trainees Association

OBJECTIVE

To investigate the time course of an epidemic of asthma after a thunderstorm, characteristics of patients affected, and the demand on emergency medical resources.

DESIGN

Study of registers and records in accident and emergency departments and questionnaire to staff.

SETTING

London area.

SUBJECTS

All patients presenting at 12 accident and emergency departments with asthma or other airway disease.

MAIN OUTCOME MEASURES

Numbers of patients, clinical features, information on shortage of resources--equipment, drugs and staff.

RESULTS

The epidemic had a sudden onset on 24 June 1994; 640 patients with asthma or other airways disease attended during 30 hours from 1800 on 24 June, nearly 10 times the expected number. Over half (365) the patients were aged 21 to 40 years. A history of hay fever was recorded in 403 patients; for 283 patients this was the first known attack of asthma; a history of chronic obstructive airways disease was recorded in 12 patients. In all, 104 patients were admitted (including five to an intensive care unit). Several departments ran out of equipment or drugs, called in additional doctors, or both.

CONCLUSIONS

This study supports the view that this epidemic was larger than previously reported epidemics and the hypothesis that "thunderstorm associated asthma' is related to aeroallergens. Demands on resources were considerable; a larger proportion of patients needing intensive care would have caused greater problems.

Childhood asthma--advances in pathogenesis

Increase in morbidity and mortality of asthmatics in the world is a cause of concern. Many researchers have described various aspects of etiopathogenesis which has thrown light on the better understanding of asthma. Our experience with nearly 3 lakhs of asthmatic children, over a period of twenty-five years and our studies in Asthma clinic of ICH & HC, Madras generated new ideas to propose a hypothesis on etiopathogenesis of asthma. "Asthma is a disease caused by a specific infective agent in a genetically predisposed individual resulting in altered cellular response initially leading to hyperactive bronchial tree which on exposure to various aggravating factors manifest clinically as recurrent cough, dyspnoea and wheeze". Category of wheezers who manifest asthma is also discussed.

Airway responsiveness to allergen is increased 24 hours after exercise challenge

Although exercise is one of the most ubiquitous triggers of acute bouts of asthma, the changes in airway responsiveness before and after exercise are not well defined. Specifically, the effect of the changes in airway responsiveness induced by exercise has not been studied on subsequent allergen exposure. To test whether the reactivity to allergen is altered by preceding exercise and to define possible factors determining it, we subjected 24 children with atopic asthma to the relevant allergen challenge on two occasions: one as a control without a preceding procedure and the other 24 hours after exercise challenge. Mean postallergen maximal percent falls in forced expiratory volume in 1 second from baseline (delta FEV1) of the whole group were higher after the exercise challenge compared with those of control in both early (< 1 hour) and late (3 to 10 hours) phases. The changes of postallergen maximal delta FEV1 between the control and post-exercise allergen challenges were not related to the early bronchial response to the preceding exercise challenge. Late asthmatic responses to exercise developed in six children, and the changes in both early and late phases were significantly higher in these children, compared with those without late asthmatic responses. Furthermore, the changes were well correlated with the magnitude of the late-phase response to preceding exercise in the group as a whole. It is concluded that an increased airway responsiveness to allergen occurs 24 hours after exercise in some patients with asthma. As the changes are related to a late bronchial response to exercise, late asthmatic response to exercise, when it occurs, may be associated with increased asthmatic symptoms for as long as 24 hours after exercise.

Bronchial responsiveness is not always increased after allergen challenge

Increased bronchial responsiveness has been reported at various time points following allergen challenge (AC), and may be related to the magnitude of the late response (LAR). We have studied 20 mild asthmatics, who were known to develop a late asthmatic response to inhalation of house dust mite extract (fall of > 15% from post-diluent baseline FEV1 from 2 to 7h after AC). The provocation concentration of methacholine causing a 20% fall in FEV1 (PC20 FEV1) was measured before and 24 h after challenge with house dust mite extract (HDM). The mean (SEM) change in log(PC20) was 0.08 (0.09) mg ml-1, and was not significant (P = 0.38; paired t-test). The change in PC20 for each subject was not significantly correlated with the size of LAR (r = -0.33; P > 0.05), but was significantly correlated with the absolute change from baseline FEV1 at 24 h (r = 0.67; P < 0.01). Our subjects had a high baseline responsiveness, when compared with previous studies. We suggest they may have been approaching a maximally responsive state prior to study, and allergen challenge may have had little effect in further increasing responsiveness. Exposure to allergen in late responders is not necessarily followed by an increase in non-specific bronchial responsiveness.

Development of atopic asthma in infants with pulmonary congestion caused by congenital heart disease

We studied the effects of pulmonary congestion on the development of atopic asthma in 31 infants with congenital heart disease. Respiratory distress did not resolve after surgery in seven patients, six of whom had a family history of allergy. Pulmonary congestion in infancy may increase the risk of atopic asthma in genetically predisposed children.

Airways of allergic rhinitics are 'primed' to repeated allergen inhalation challenge

The hypothesis that repeated exposure to a specific allergen will further increase bronchial responsiveness to that allergen is supported by indirect evidence. However, it has not been tested as intensely in the laboratory setting, and in some cases, conflicting results are presented. In order to test the hypothesis in the atopic subjects, allergen inhalation challenge tests were performed in 29 house dust mite (Dermatophagoides pteronyssinus) sensitive subjects with allergic rhinitis. Nine subjects displayed early asthmatic responses (EARs) to the first challenge (Group I). Twenty subjects with no significant airway response were submitted to the second challenge 24 h later. Thirteen subjects showed EARs (Group II) and two of these showed late asthmatic responses (LARs) as well. In Group II, there were significant changes between the first and second challenge in post-allergen early phase FEV1 (88.1 +/- 4.2 vs 71.7 +/- 4.2% baseline, P < 0.05) and in post-allergen late phase FEV1 (93.1 +/- 3.4 vs 86.6 +/- 7.8, P < 0.05). After the second challenge, PD20 (provocative dose of methacholine required to produce a 20% fall in FEV1) decreased significantly from the baseline values. When challenged separately with twofold dose of allergen, only three and one of the Group II showed EAR and LAR respectively. PD20 did not change significantly after this challenge. These results indicated that two repeated exposure to allergen dose, which is not enough to cause significant airway responses at a time, may provoke asthmatic airway responses in the subjects with allergic rhinitis and that this effect of priming is not attributed to the cumulative dose but to the consequent effect of repeated allergen exposure.

Reversibility of the allergen-provoked late asthmatic response by an inhaled beta 2-adrenoceptor agonist

There is uncertainty about the relative contributions of bronchial smooth muscle contraction, mucosal oedema and mucus plugging to airflow obstruction in the allergen-induced late asthmatic response (LAR). We systematically studied the ability of the inhaled beta 2-agonist salbutamol to reverse the LAR in eight subjects after allergen bronchoprovocation. Salbutamol reversed the LAR by restoring FEV1 to a level similar to the initial value measured at the same time of day (18.00 h) on the previous evening. For the eight subjects studied, this initial FEV1 value, measured after abstaining from beta-agonists for 8 h, was a mean +/- SEM 90.7 +/- 5.6% of predicted, which suggests further bronchodilation may have been possible at this time. We then studied six of the eight subjects in an identical protocol with saline challenge substituted for allergen bronchoprovocation to answer the question whether further bronchodilation was possible at that time after salbutamol in the absence of an LAR. After salbutamol on the allergen challenge day the FEV1 for the six subjects was 84.1 +/- 7.0% of predicted, compared with 94.0 +/- 3.7% of predicted at the same point on the saline challenge day (P < 0.05). We conclude that, although the LAR may be effectively reversed by beta 2-agonists, there is evidence for some residual airway narrowing, presumably related to mucosal oedema, exudate and mucus plugging.

Contribution of pulmonary hemodynamics on manifestation of allergic asthma in patients with congenital heart disease

The purpose of this study was to determine whether pulmonary hemodynamic abnormalities relate to manifestations of allergic asthma. In 448 patients with congenital heart disease the relationships between asthma and age or pulmonary arterial blood (PA) flow were studied. Asthma (allergic and non-allergic) was more common in 39 (19%) of 201 patients with high PA flow, compared with the incidence in those with normal PA flow (6/117, 5%; P < 0.001) and reduced PA flow (1/130, 1%; P < 0.05). In the high PA flow group, the frequency of asthma declined significantly (P < 0.01) with age, from 25-26% in the 6 month-5 year patient group to 5% in the 6-12 year old patients. The frequency of asthma, including allergic type, was significantly (P < 0.01) greater in patients with pulmonary hypertension (15/24, 63%) than in those without (10/77, 13%) at the age of 6 months to 1 year. Asthma in the high PA flow group was associated with other allergic diseases in 30 (77%) of 39 patients, including food allergy in nine (23%), atopic dermatitis in 14 (36%), allergic rhinitis in seven (18%) and abnormally high total IgE levels in 14 (36%). These findings suggest that high pulmonary flow or pulmonary hypertension enhances the manifestation of allergic disease, particularly asthma.

Importance of house dust mite and Alternaria allergens in childhood asthma: an epidemiological study in two climatic regions of Australia

The relation of house dust mite allergen levels to asthma and allergy was examined in two population samples of children aged 8-11 years in northern New South Wales. We studied 805 children in Lismore (a hot, humid, coastal region) and 770 in Moree/Narrabri (a hot, dry inland region). Respiratory symptoms were measured by questionnaire, bronchial hyperresponsiveness (BHR) by histamine inhalation test, and allergy by skin-prick tests. Current asthma was defined as the presence of both wheeze in last 12 months and BHR. Der p I levels were measured in dust from the bed and floors in the homes of 57 randomly selected children in the coastal region and of 74 inland children. Der p I levels were significantly higher by the coast (83.0 vs 11.2 microg/g, P < 0.001). House dust mite sensitivity was of similar prevalence in both regions (28.6 vs 26.4%, n.s.) but Alternaria sensitivity was higher inland (4.0 vs 15.2% P<0.001). Bronchial responsiveness was more severe in coastal children sensitized to house dust mites and in inland children who were sensitized to Alternaria. The adjusted odds ratios for current asthma in children sensitized to house dust mites were 21.3 (95% CI 10.5, 43.2) by the coast and 2.7 (95% CI 1.3, 5.4) inland, and in children sensitized to Alternaria were 3.4 (95% CI 1.3, 9.1) in the coastal region and 5.6 (95% CI 3.1, 10.1 inland. These studies suggest that high house dust mite allergen levels in a humid, subtropical region act to significantly increase bronchial responsiveness in sensitized children, and that Alternaria allergens have a similar but less potent action in a dry, rural region.

Lymphocyte transformation test with house dust mite (Dermatophagoides pteronyssinus) in normal children, asthmatic children and asthmatic children receiving hyposensitization

In the first part of this study the proliferative response of lymphocytes (lymphocyte transformation test) to house dust mite (HDM) stimulation in cultures was studied in normal children (n = 16), asthmatic children who never received hyposensitization (HS) (n = 50) and asthmatic children receiving HS with HDM for at least 6 months (n = 20). The results are expressed as disintegrations per minute (d.p.m.) and as stimulation index (SI = d.p.m. in the presence of the allergen/d.p.m. in the control culture). A positive SI (> 2) was found in 54% of the asthmatic children who never received HS, in 30% of the asthmatics receiving HS and in none of the normal children. Furthermore, between asthmatics with and without HS, the SI was not statistically different, although asthmatics without HS tended to have a higher SI (median value: 2.13 vs 1.38) (P = 0.10). In a second series of experiments the effect of adding interleukin-2 (IL-2) to the lymphocyte cell culture was studied in asthmatic children with and without HS. Interleukin-2 induced an additional stimulatory effect on the lymphoproliferative response to HDM and to phytohaemagglutinin in patients who never received HS, but had no effect in patients receiving HS. We conclude that HS treatment seems to have an inhibiting effect upon this proliferative response, not only inhibiting the degree of the allergen-induced lymphocyte proliferation, but also inhibiting the sensitivity of proliferating lymphocytes for IL-2. These inhibiting effects upon lymphocytic activation could be responsible for the anti-inflammatory effects (i.e. suppression of the late asthmatic reaction) of HS.

T cell-mediated induction of airway hyperresponsiveness and altered lung functions in mice are independent of increased vascular permeability and mononuclear cell infiltration

Previously it was demonstrated that during delayed-type hypersensitivity reactions (DTH) to picryl chloride (PCl) in murine lungs, as a model for cellular IgE-independent immunity, tracheal hyperreactivity and increased pulmonary resistance are induced. In the present study it is demonstrated that after pretreatment with 5HT-2 antagonists, such as ketanserin and methysergide, DTH lung reactions to PCl in mice are suppressed. The increase in vascular permeability, detectable at 2 h after intranasal hapten challenge and probably necessary for the development of a classic DTH reaction, as was demonstrated in skin DTH models, as well as the classic late inflammatory component of lung DTH, is inhibited. However, in vitro tracheal hyperreactivity to the cholinergic receptor agonist carbachol and increased pulmonary resistance in vivo, both induced during the development of these inflammatory DTH lung reactions, are not affected by 5HT-2 receptor antagonist pretreatment. These results indicate that the actual presence of increased vascular permeability and mononuclear infiltrates is not a prerequisite for the development of changed lung functions and tracheal hyperresponsiveness. Thus in mice, serotonin-independent mechanisms that appear during T cell-dependent lung immune reactions induce airway hyperresponsiveness and increased pulmonary resistance.

Bronchial lavage and bronchoalveolar lavage in allergen-induced single early and dual asthmatic responders

The phenotypic cellular profile of bronchial lavage (BL) and bronchoalveolar lavage (BAL) was studied in 7 single early (SR) and 10 dual asthmatic responders (DR). Lavage was performed, after previously having determined bronchial hyperresponsiveness to histamine and the response to house dust mite (HDM) challenge. The recovered lavage fluid was separated in two fractions, BL and BAL. Total fluid recovery and cell number from the BL and BAL were comparable in both patient groups. Differential cell counting and immunocytochemistry were performed. DR had a significantly higher number of eosinophils and EG2+ cells in BL but not in their BAL. No differences could be found in CD4+, CD8+, and HLA-DR+ cells. A strong correlation was found between eosinophils in the BL+ and EG2+ cells in the BL (r = 0.79, p < 0.001) and between eosinophils in the BL and peripheral blood eosinophils (r = 0.70, p < 0.0025). The number of EG2+ cells and the number of epithelial cells in both BL and BAL showed a correlation (r = 0.55, p < 0.05). Dual responders had a higher total IgE (p < 0.01), and total serum IgE correlated well with the eosinophils in the BL (r = 0.85, p < 0.0001). Our observations demonstrate cellular differences in the lung on mainly a bronchial level between single early and dual asthmatic responders. A bronchial lavage eosinophil and EG2+ cell count and higher blood total IgE level are associated with the tendency to develop a dual asthmatic response.

Recent advances in the pathogenesis of atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disorder affecting 5%-10% of children. Although basic mechanisms remain largely speculative, recent studies on the pathogenesis have elucidated new insights, pointing to the importance of food and inhalant allergens. The pathogenesis of AD can be more easily explained by the model of late skin reaction occurring after mast cell activation. The present report highlights some of the more recent developments in the mechanisms of AD which can be important in understanding and treating this troublesome disease.

Asthma pathogenesis and the implications for therapy in children

Gaining greater insight into the pathogenesis of asthma has redefined the approach to treatment of children with asthma. Clearly, the Expert Panel of the National Heart, Lung, and Blood Institute National Education Program has played a major role in taking the message to a wide audience of health care providers. Although only early trends are evident at this point in time, within several years therapeutic trends underway currently will be more commonplace, and we may observe how asthma continues to impact society and our health care system. The approach to therapy will continue to evolve and most likely be controversial for years to come.

Pharmacotherapy of childhood asthma. An inflammatory disease

The recognition that asthma constitutes 2 kinds of physiopathological reactions, namely bronchospasms (immediate reactions) and inflammatory responses (late reactions), suggests that the treatment should be focused against these events. Furthermore, the allergen provocation model, showing the existence of immediate and late asthmatic reactions, can be used to study the effects of different antiasthmatic drugs. Recently, the importance of inflammation in the pathogenesis of asthma in adults has led to the development of therapeutic regimens in which anti-inflammatory treatments are used frequently as a first-line step in the management of asthma. Although at the moment the hard data showing inflammation in childhood asthma are scarce, it is assumed that childhood asthma constitutes the same kind of chronic inflammatory processes as in adult asthma and that its treatment should also include anti-inflammatory drugs.

Inflammation and the allergic response

The atopic diseases--allergic rhinitis, asthma, and atopic dermatitis--are chronic inflammatory diseases characterized by an exacerbating and remitting course and can only rarely be associated causally with allergen exposure. The challenge to ascribe an allergic basis to these diseases is derived from the apparent inability to reconcile these chronic inflammatory features with a process thought to be initiated by the rapid release of mediators after the interaction of allergen with IgE-coated mast cells. The traditional understanding has been that mast cell activation results in the release of a series of preformed and rapidly synthesized substances that mediate the immediate onset of vasodilatation, vascular leakage, smooth muscle contraction, and irritant nerve receptor stimulation. These mediators, however, are rapidly degraded and are not thought to be associated with a significant inflammatory component. Recent studies, however, have established that the interaction of allergen with the immune system is, in fact, far more complex (Fig. 4). In addition to mast cell activation, allergen can interact with and activate T-lymphocytes and mononuclear phagocytic cells, leading to the secretion of cytokines and other inflammatory substances. Furthermore, the interaction of allergen with the mast cell may be far more complex, with the potential to stimulate the delayed release of newly synthesized cytokines. The interaction of allergen with the immune system also promotes the secondary release of inflammatory neuropeptides. Thus, the known spectrum of mediators released after allergen exposure has vastly been expanded. These include numerous still uncharacterized chemotactic and activating peptides; eicosanoids such as 5-HETE, 12-HETE, and leukotriene B4; platelet-activating factor; several proteases; neuropeptides and, most importantly, the cytokines. These mediators recruit and activate neutrophils, monocytes, basophils, and eosinophils, attract additional lymphocytes and mononuclear phagocytic cells, and induce mast cell proliferation with further mast cell degranulation. A vicious cycle subsequently develops, with further inflammation and tissue destruction. Thus, the interaction of allergen with the immune system has become a complex cascade capable of producing the chronic inflammatory changes characteristic of allergic diseases.

Asthma in children

Despite advances in the understanding of asthma, there is still a high rate of morbidity and mortality from this disease in children. Although many factors are involved, a persistent concern is that the overuse of beta-agonists combined with the underuse of antiinflammatory medications leads to increased mortality. The demonstration that airway inflammation is present in mild asthma and the observations that inflammatory stimuli increase airway responsiveness have led to the use of antiinflammatory agents at earlier stages of disease. However, the medications with antiinflammatory activity that are currently available are not effective for all patients. The problems posed by chronic severe asthma in a child despite appropriate use of corticosteroids suggest that our current concepts are overly simplistic. Therefore, health care workers dealing with this disease must maintain an open mind about what constitutes optimal therapy.

A research method to induce and examine a mild exacerbation of asthma by withdrawal of inhaled corticosteroid

This study evaluated a research method to examine an exacerbation of asthma induced by corticosteroid withdrawal. Ten non-smoking adult asthmatics who were stable on treatment with inhaled steroid underwent a graded reduction of the daily dose by 200 micrograms at weekly intervals until an exacerbation of symptoms occurred. A daily symptom, peak expiratory flow rate (PEF) and medication diary was kept. Weekly clinic visits were used to assess symptoms, spirometry, methacholine airway responsiveness (expressed as the provocative concentration to cause a fall in FEV1 of 20%, PC20), circulating eosinophils, basophils and their progenitors (Eo/B-CFU), and sputum inflammatory cells. The laboratory tests were performed blind to the clinical details. Each subject developed an exacerbation of symptoms, on average at 16 (7-26) days after the onset of steroid reduction. This was accompanied by a deterioration in each of the objective measures. There was a fall in FEV1 by 320 ml (s.e.m. 9.5) and in PC20 from 0.8 to 0.43 mg/ml. Circulating eosinophils rose from 114 (24) x 10(3)/ml to 227 (50) x 10(3)/ml and Eo/B-CFU rose from 31 (5.6) to 44 (11.3)/10(6) cells. Sputum developed in five subjects and contained 36 (5.2)% eosinophils and 1.98 (0.21)% metachromatic cells (mast cells or basophils). The symptom diary and weekly questionnaire were demonstrated to be valid and responsive to change. A deterioration indicated by the daily symptom score preceded changes in PEF. Treatment by an increase in steroid was followed by reversal of each of the changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Theophylline inhibits late asthmatic reactions induced by toluene diisocyanate in sensitised subjects

Toluene diisocyanate (TDI)-induced asthma is a frequent occupational airway disease. To determine whether a calibrated dosage of oral slow-release theophylline inhibits asthmatic reactions and the associated increase of airway responsiveness to methacholine induced by TDI, we examined six asthmatic subjects who developed a late or a dual asthmatic reaction after TDI inhalation challenge. We administered oral slow-release theophylline or placebo to each subject for 7 days according to a double-blind, randomized, cross-over study design. When the subjects received a placebo, TDI caused a late or a dual asthmatic reaction. When the subjects received theophylline. TDI caused significantly reduced late asthmatic reactions. Mean serum theophylline concentrations were within the therapeutic range. Theophylline neither modified the baseline airway responsiveness to methacholine, nor the increase of airway responsiveness to methacholine induced by TDI. These results suggest that slow-release theophylline may improve TDI-induced late asthmatic reactions, but it does not change the baseline airway responsiveness to methacholine and the increase of airway responsiveness to methacholine induced by TDI.

Platelet-activating factor (PAF) plays an important role in the immediate asthmatic response in guinea-pig by augmenting the response to histamine

1. To investigate the role of platelet activating factor (PAF) in the immediate asthmatic response, we examined the bronchial reactivity to histamine after administration of PAF to guinea-pigs or antigen challenge to passively sensitized guinea-pigs. 2. A bolus injection of PAF (20-40 ng kg-1), which did not cause a significant increase in intrathoracic pressure (ITP), augmented the bronchial response to histamine almost 8 fold. This airway hyperreactivity was observed even 1 min after PAF treatment. 3. A subthreshold dose of antigen (0.01 mg kg-1, i.v.) also provoked hyperreactivity to histamine, which became significant 6 and 11 min after the antigen treatment. 4. The specific PAF-antagonists, SM-10661 and CV-6209 (i.v.) dose-dependently inhibited both PAF- and antigen-induced airway hyperreactivities to histamine. 5. These results suggest that PAF plays an important role in antigen-induced acute airway responses by augmenting the activities of spasmogens.