Prevalence of asthma, atopy and bronchial hyperresponsiveness and their interrelation in a semi-rural area of Chile.

OBJECTIVE: To assess the prevalence of asthma symptoms and their association with sensitisation to eight allergens and bronchial hyperresponsiveness (BHR) to methacholine. SETTING: A random sample of 1232 adults, aged 22 to 28 years, studied in a Chilean semi-rural area. DESIGN: A cross-sectional design for the purpose of this analysis. RESULTS: The prevalence of wheeze was 27.4% (95%CI 24.9-29.9) and waking with breathlessness 13.7% (95%CI 11.8-15.6), higher than the results of a multi-centre European study. Only 7.8% (95%CI 6.3-9.3) had a positive BHR (< or =8 mg/ml) and 26.3% (95%CI 23.8-28.8) were atopic. The Youden index of asthma symptoms in non-atopic subjects varied from 0.184 to 0.259 when using BHR as gold standard for asthma, and increased from 0.379 to 0.504 among those with positive atopy. Only 4.5% reported asthma, and the Youden index was slightly higher in comparison to the asthma symptom groups. CONCLUSION: The prevalence of asthma symptoms in young adults was high, but only a small proportion of these were sensitised or had a positive BHR. We believe that aetiological studies of asthma should analyse subjects with asthma symptoms separately from those with positive atopic status or positive BHR.

The early origins hypothesis with an emphasis on growth rate in the first year of life and asthma: a prospective study in Chile.

BACKGROUND: There is uncertainty about the impact of the programming hypothesis in terms of nutritional status at birth, rate of growth in the first year of life, length of gestation, breast feeding, and episodes of illness on asthma. An analysis was therefore carried out to test this hypothesis. METHODS: Data were collected on 1232 children born between 1974 and 1978 in a semi-rural area of Chile. Measurements at birth and growth in the first year of life were obtained from a birth registry and clinical notes. Information on asthma was collected using the European Community Respiratory Health Survey questionnaire. Sensitisation to eight allergens and bronchial hyperresponsiveness (BHR) to methacholine were determined. All other information was obtained using a questionnaire. Polytomous logistic analyses were carried out to explore the association of factors at birth and during the first year of life with asthma symptoms, atopy, and BHR. RESULTS: Weight and length gain in the first year were positively associated with wheeze (odds ratio (OR) 1.004, 95% CI 1.001 to 1.007 and OR 1.11, 95% CI 0.98 to 1.25, respectively). A higher body mass index (BMI) at birth was protective in subjects reporting both wheeze and waking with breathlessness (OR 0.54, 95% CI 0.35 to 0.84). Length rate in tertiles divided by length at birth in tertiles was related to asthma symptoms (OR 1.68, 95% CI 1.19 to 2.37). Most other assessments were not associated with asthma. CONCLUSION: These results show promising but inconclusive evidence that a rapid rate of growth in length, especially in newborn infants of low length, might be involved in the aetiology of asthma.

Differential effects of respiratory syncytial virus and adenovirus on mononuclear cell cytokine responses.

Respiratory syncytial virus (RSV) and adenovirus (Advs) serotype 3 (Adv3) and 7h (Adv7h) are associated with mild to severe respiratory infection and are indistinguishable during the acute phases of the illnesses. However, outcome and long-term prognosis are different with both infections. RSV infection is associated with later development of asthma, and Adv, mainly Adv7h, with severe lung damage, bronchiectasis, and hyperlucent lung. We hypothesized that this difference could be partly due to different immune responses induced by these viruses. To test this hypothesis we quantified TCD4+, TCD8+, and BCD19+ expressing the interleukin-2 receptor-alpha chain (CD25) and interferon-gamma (IFN-gamma), interleukin (IL)-10, and IL-4 in the supernatant of peripheral blood mononuclear cells (PBMC) from school children infected in vitro with and without RSV, Adv7h, and Adv3 and after phytohemagglutinin (PHA) stimulation in the presence or absence of these viruses at a multiplicity of infection (MOI) of 1. PBMC from every child produced more IL-10 (p

Respiratory syncytial virus infection in infants is associated with predominant Th-2-like response.

Viral infections have been associated with cellular immune responses and production of Th-1 cytokines. Respiratory syncytial virus (RSV), however, induces virus-specific IgE, which might be a consequence of a Th-2-like activation. To test this hypothesis we quantified interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) in the supernatant of peripheral blood mononuclear cells cultured for 24 and 48 h in the presence or absence of phytohemaglutinin and pokeweed mitogen and the lymphocyte phenotypes to analyze subsets and their activation markers, from 15 hospitalized infants during an acute lower respiratory infection caused by RSV and 17 healthy control infants from 1 to 15 mo of age. Compared with the control infants, those infected with RSV had an increase in the number of B-cells (p < 0.02) and decreases in both CD8+ T-cells (p < 0.01) and activated CD8+/CD25+ suppressor/ cytotoxic T-cells (p < 0.007). In RSV-infected infants, IFN-gamma production was subtotally suppressed, whereas IL-4 production was decreased to a lesser degree, giving significantly (p < 0.001) increased IL-4/IFN-gamma ratio compared with that in the control infants. These findings suggest a predominant Th-z-like response in RSV-infected infants, which could explain some aspects of the immunopathogenesis of RSV infection and the RSV-specific and nonspecific IgE antibody responses observed.