RESUMO
BACKGROUND: The association between atopy and asthma is attenuated in non-affluent populations, an effect that may be explained by childhood infections such as geohelminths. OBJECTIVE: To investigate the association between atopy and wheeze in schoolchildren living in urban and rural areas of Ecuador and examine the effects of geohelminths on this association. METHODS: We performed nested case-control studies among comparable populations of schoolchildren living in rural communities and urban neighbourhoods in the Province of Esmeraldas, Ecuador. We detected geohelminths in stool samples, measured recent wheeze and environmental exposures by parental questionnaire, and atopy by specific IgE (sIgE) and skin prick test (SPT) reactivity to aeroallergens. RESULTS: Atopy, particularly sIgE to house dust mite (HDM), was more strongly associated with recent wheeze in urban than rural schoolchildren: (urban, adj. OR 5.19, 95% CI 3.37-8.00, P < 0.0001; rural, adj. OR 1.81, 95%CI 1.09-2.99, P = 0.02; interaction, P < 0.001). The population fractions of wheeze attributable to atopy were approximately two-fold greater in urban schoolchildren: SPT to any allergen (urban 23.5% vs. rural 10.1%), SPT to HDM (urban 18.5% vs. rural 9.6%), and anti-HDM IgE (urban 26.5% vs. rural 10.5%), while anti-Ascaris IgE was related to wheeze in a high proportion of rural (49.7%) and urban (35.4%) children. The association between atopy and recent wheeze was attenuated by markers of geohelminth infections. CONCLUSIONS: Our data suggest that urban residence modifies the association between HDM atopy and recent wheeze, and this effect is explained partly by geohelminth infections.
Assuntos
Hipersensibilidade Imediata/epidemiologia , Hipersensibilidade Imediata/imunologia , Sons Respiratórios/imunologia , População Rural , População Urbana , Adolescente , Alérgenos/imunologia , Animais , Estudos de Casos e Controles , Criança , Estudos Transversais , Exposição Ambiental/efeitos adversos , Feminino , Humanos , Imunoglobulina E/sangue , Imunoglobulina E/imunologia , América Latina/epidemiologia , Masculino , Fatores de Risco , Testes Cutâneos , Inquéritos e Questionários , Adulto JovemRESUMO
BACKGROUND: Most childhood asthma in poor populations in Latin America is not associated with aeroallergen sensitization, an observation that could be explained by the attenuation of atopy by chronic helminth infections or effects of age. OBJECTIVE: To explore the effects of geohelminth infections and age on atopy, wheeze, and the association between atopy and wheeze. METHODS: A case-control study was done in 376 subjects (149 cases and 227 controls) aged 7-19 years living in rural communities in Ecuador. Wheeze cases, identified from a large cross-sectional survey, had recent wheeze and controls were a random sample of those without wheeze. Atopy was measured by the presence of allergen-specific IgE (asIgE) and skin prick test (SPT) responses to house dust mite and cockroach. Geohelminth infections were measured in stools and anti-Ascaris IgE in plasma. RESULTS: The fraction of recent wheeze attributable to anti-Ascaris IgE was 45.9%, while those for SPT and asIgE were 10.0% and 10.5% respectively. The association between atopy and wheeze was greater in adolescents than children. Although Anti-Ascaris IgE was strongly associated with wheeze (adj. OR 2.24 (95% CI 1.33-3.78, P = 0.003) and with asIgE (adj. OR 5.34, 95% CI 2.49-11.45, P < 0.001), the association with wheeze was independent of asIgE. There was some evidence that the association between atopy and wheeze was greater in uninfected subjects compared with those with active geohelminth infections. CONCLUSIONS AND CLINICAL RELEVANCE: Atopy to house dust mite and cockroach explained few wheeze cases in our study population, while the presence of anti-Ascaris IgE was an important risk factor. Our data provided only limited evidence that active geohelminth infections attenuated the association between atopy and wheeze in endemic areas or that age modified this association. The role of allergic sensitization to Ascaris in the development of wheeze, independent of atopy, requires further investigation.
Assuntos
Helmintíase/imunologia , Hipersensibilidade Imediata/etiologia , Hipersensibilidade Imediata/imunologia , Sons Respiratórios/etiologia , Sons Respiratórios/imunologia , Adolescente , Fatores Etários , Animais , Ascaris/imunologia , Estudos de Casos e Controles , Criança , Baratas/imunologia , Equador/epidemiologia , Feminino , Humanos , Imunoglobulina E/sangue , Imunoglobulina E/imunologia , Masculino , Pyroglyphidae/imunologia , População Rural , Testes Cutâneos , Adulto JovemRESUMO
BACKGROUND AND OBJECTIVE: The capacity of respiratory syncytial virus (RSV) to stimulate an IgE antibody response and enhance the development of atopy and asthma remains controversial. Nasal washes and sera from 40 infants (20 with wheezing, 9 with rhinitis, and 11 without respiratory tract symptoms) were obtained to measure IgE, IgA, and IgG antibody to the immunodominant, F and G, virion proteins from RSV. STUDY DESIGN: Children (aged 6 weeks to 2 years) were enrolled in the emergency department during the mid-winter months and seen at follow-up when they were asymptomatic. All nasal washes were tested for RSV antigen. Determinations of antibody isotypes (IgE, IgA, and IgG) to RSV antigens were done in nasal washes and sera by using an enzyme-linked immunosorbent assay. In a subset of nasal washes, IgE to RSV was also evaluated by using a monoclonal anti-F(c)E antibody-based assay. RESULTS: Fifteen patients with wheezing, two with rhinitis, and one control subject tested positive for RSV antigen at enrollment. Thirteen patients with wheezing were <6 months old, and most (77%) were experiencing their first attack. Among the children with positive test results for RSV antigen, an increase in both nasal wash and serum IgA antibody to RSV-F(a) and G(a) was observed at the follow-up visit. However, there was no evidence for an IgE antibody response to either antigen. CONCLUSION: Both IgA and IgG antibodies to the immunodominant RSV-F(a) and G(a) antigens were readily detected in the nasal washes and sera from patients in this study. We were unable to demonstrate specific IgE antibody to these antigens and conclude that the production of IgE as a manifestation of a T(H)2 lymphocyte response to RSV is unlikely.
Assuntos
Asma/virologia , Imunoglobulina A/metabolismo , Imunoglobulina E/metabolismo , Imunoglobulina G/metabolismo , Infecções por Vírus Respiratório Sincicial/imunologia , Antígenos Virais/imunologia , Asma/complicações , Estudos de Casos e Controles , Feminino , Humanos , Lactente , Masculino , Sons Respiratórios/etiologia , Sons Respiratórios/imunologia , Infecções por Vírus Respiratório Sincicial/complicações , Fatores de Risco , Estatísticas não ParamétricasRESUMO
In tropical and subtropical regions of the world, allergens produced by Blomia tropicalis are an important cause of IgE-mediated sensitization among patients with asthma. We compared the relative importance of sensitization to the two mite species among asthma patients from Florida, Puerto Rico, and Brazil (n = 83), who were concurrently exposed to B. tropicalis and D. pteronyssinus, with patients from the United States and from the United Kingdom (n = 56) exposed to D. pteronyssinus. In addition, molecular cloning techniques were used to clone and express a major B. tropicalis allergen. There were significant differences between IgE antibody responses to B. tropicalis and D. pteronyssinus that were related to exposure: only 22% of patients exposed to both species had a high ratio (> 10) of IgE D. pteronyssinus:B. tropicalis, whereas 68% of patients exposed only to D. pteronyssinus had a ratio of > 10 (p < 0.001). A major 14-kD allergen (Blo t 5), cloned from a B. tropicalis cDNA library, showed 43% sequence homology to D. pteronyssinus Der p 5. Recombinant Blo t 5 produced in E. coli reacted with 45 to 69% of sera from B. tropicalis-allergic asthmatics and induced positive immediate skin tests at 10(-3) to 1 microg/ml. In vivo and in vitro comparisons of IgE responses to B. tropicalis, D. pteronyssinus, rBlo t 5, and rDer p 5, showed that B. tropicalis has unique allergens that cause specific IgE responses. The results suggest that B. tropicalis is an independent cause of sensitization and that use of recombinant Blo t 5 should lead to a better understanding of the role of B. tropicalis in causing asthma in tropical environments.
Assuntos
Alérgenos/imunologia , Asma/imunologia , Ácaros/imunologia , Adolescente , Adulto , Sequência de Aminoácidos , Animais , Antígenos de Dermatophagoides , Antígenos de Plantas , Sequência de Bases , Brasil , Criança , Pré-Escolar , Clonagem Molecular , Florida , Glicoproteínas/imunologia , Humanos , Imunoglobulina E/análise , Dados de Sequência Molecular , Porto Rico , Proteínas Recombinantes/imunologia , Homologia de Sequência , Testes Cutâneos , Clima TropicalRESUMO
BACKGROUND: Our objective was to identify the allergens associated with asthma among schoolchildren in an area of the United States where dust mite growth is expected to be poor. Los Alamos, N.M., was chosen because it has low rainfall and is at high altitude (7200 feet) making it very dry. One hundred eleven children (12 to 14 years old) from the middle school who had been previously classified according to bronchial hyperreactivity to histamine (BHR) were studied. METHODS: Sera were assayed for IgE antibodies to mite, cat, dog, cockroach, Russian thistle, and grass pollen, with both CAP system fluoroimmunoassay (Kabi Pharmacia, Uppsala, Sweden) and conventional RAST. Allergens were measured in dust samples from 108 homes with two-site assays for mite (Der p 1 and Der f 1), cat (Fel d 1), dog (Can f 1), and cockroach (Bla g 2). RESULTS: Concentrations of dog and cat allergens were elevated in almost all houses with pets but were also high in a significant proportion of the houses without pets. Levels of mite allergen were less than 2 micrograms/gm in 95% of the houses, and cockroach was undetectable in all but two of the houses. Among the 21 with BHR who had symptoms, 67% had IgE antibody to dog and 62% had IgE antibody to cat. For these allergens IgE antibody was strongly associated with asthma (p < 0.001). By contrast, the presence of IgE antibody to mite, cockroach, or grass pollen was not significantly associated with asthma. CONCLUSION: The high prevalence of IgE antibody to cat and dog allergens among these children is in keeping with the presence of cat and/or dog allergen in most of the houses. Furthermore, sensitization (as judged by IgE antibodies) to cat and dog allergens was strongly associated with asthma. On the other hand, no clear relationship was found between sensitization or symptoms and the current level of allergen in individual houses. The results show that in this mite-and cockroach-free environment sensitization to domestic animals was the most significant association with asthma.
Assuntos
Alérgenos/imunologia , Asma/imunologia , Glicoproteínas/imunologia , Imunização , Adolescente , Poluição do Ar em Ambientes Fechados , Animais , Anticorpos/análise , Antígenos de Plantas , Gatos , Criança , Cães , Exposição Ambiental , Humanos , Imunoglobulina E/análise , Imunoglobulina E/imunologia , New MexicoRESUMO
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.
Assuntos
Proteínas Sanguíneas , Cátions , Eosinófilos , Líquido da Lavagem Nasal/química , Sons Respiratórios , Adolescente , Proteínas Sanguíneas/análise , Cátions/análise , Criança , Pré-Escolar , Humanos , Imunoglobulina E/sangue , Lactente , Vírus Sinciciais Respiratórios/isolamento & purificação , Doenças Respiratórias/virologiaRESUMO
A survey of the Middle School in Los Alamos, N.M., USA, identified 57 children with symptoms of asthma and 54 controls. Among these children, sensitization to cat and dog allergens was very strongly associated with bronchial reactivity and symptoms. In contrast, sensitization to mites, cockroach, or grass pollen allergens was not significantly associated with symptoms or bronchial reactivity. In keeping with these results, dust from houses in Los Alamos only contained high levels of cat or dog allergens.
Assuntos
Alérgenos/imunologia , Asma/epidemiologia , Gatos/imunologia , Cães/imunologia , Adolescente , Alérgenos/isolamento & purificação , Altitude , Animais , Asma/etiologia , Asma/imunologia , Estudos de Casos e Controles , Criança , Baratas/imunologia , Poeira/análise , Exposição Ambiental , Habitação , Humanos , Umidade , Imunoglobulina E/imunologia , Ácaros/imunologia , New Mexico/epidemiologia , Pólen/imunologia , PrevalênciaRESUMO
The most frequently invoked explanation for the origin of metabolic pathways is the retrograde evolution hypothesis. In contrast, according to the so-called "patchwork" theory, metabolism evolved by the recruitment of relatively inefficient small enzymes of broad specificity that could react with a wide range of chemically related substrates. In this paper it is argued that both sequence comparisons and experimental results on enzyme substrate specificity support the patchwork assembly theory. The available evidence supports previous suggestions that gene duplication events followed by a gradual neoDarwinian accumulation of mutations and other minute genetic changes lead to the narrowing and modification of enzyme function in at least some primordial metabolic pathways.
Assuntos
Bactérias/metabolismo , Enzimas/metabolismo , Evolução Molecular , RNA/metabolismo , Especificidade por Substrato/fisiologia , Bactérias/enzimologia , Bactérias/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , DNA Polimerase Dirigida por DNA/genética , DNA Polimerase Dirigida por DNA/metabolismo , Evolução Molecular Direcionada , Enzimas/genética , RNA/genética , RNA Catalítico/genética , RNA Catalítico/metabolismo , Especificidade por Substrato/genéticaAssuntos
Alérgenos , Asma/prevenção & controle , Exposição Ambiental , Criança , Pré-Escolar , HumanosRESUMO
We compared exposure and levels of IgE and IgG antibodies to inhalant allergens in 20 children with asthma and positive skin tests to Dermatophagoides pteronyssinus, living in São Paulo, to 20 control children without history of asthma or allergy and negative skin tests to D. pteronyssinus, D. farinae, and Blomia tropicalis. In 16/20 and 17/20 houses of asthmatic and control children, respectively, at least one sample was obtained which contained > 10 micrograms Der p I/g of dust. Serum IgE antibodies to D. pteronyssinus and Blomia tropicalis were > 200 RAST U/mL in 19/20 and in 16/20 asthmatic children, respectively. In the control group, IgE antibodies to either mite species were < 40 RAST U/mL in most cases. IgG anti-Der p I and anti-Der f I antibodies were detected in 17/20 asthmatics, as opposed to 3/20 controls. Neither cat nor cockroach allergens caused significant sensitization among asthmatic or control children. Although exposure to high levels of mite allergens was common in São Paulo, significant IgE and IgG antibody responses were detected only in children with asthma.
Assuntos
Alérgenos/imunologia , Anticorpos Anti-Idiotípicos/imunologia , Asma/epidemiologia , Asma/imunologia , Ácaros/imunologia , Administração por Inalação , Adolescente , Alérgenos/administração & dosagem , Animais , Formação de Anticorpos , Brasil/epidemiologia , Gatos/imunologia , Criança , Poeira , Exposição Ambiental , Humanos , Imunoglobulina E/imunologia , Imunoglobulina G/imunologia , Teste de RadioalergoadsorçãoRESUMO
Inner city children have the highest prevalence and the highest mortality rates for asthma in the United States. The purpose of this study was to evaluate sensitization and exposure to common indoor allergens among children aged 3 years to 15 years seen for treatment of asthma at Grady Memorial Hospital, Atlanta, Ga. Eighty children in this study were enrolled in the emergency department and 64 in hospital clinics. Dust from 57 homes, assayed for three indoor allergens (dust mite, cat, and cockroach), revealed similar exposure for asthma and control groups. Sixty-nine percent of the children with asthma had IgE antibodies to dust mite, cockroach, or cat; only 27% of the control subjects were similarly sensitized (p < 0.001). Of 35 children with asthma 21 had both sensitization and significant exposure to the relevant allergen; this was true for only 3 of 22 control subjects (odds ratio, 9.5; p < 0.001). Neither sensitization nor exposure to cat allergen was common in this population. The results show that black children in inner city Atlanta are exposed to high levels of mite and cockroach allergens and that a high proportion of the children with asthma are sensitized to these allergens; the combination of sensitization and exposure is a major risk factor for asthma in this population.
Assuntos
Asma/epidemiologia , Pobreza , População Urbana , Adolescente , Negro ou Afro-Americano/estatística & dados numéricos , Alérgenos/análise , Especificidade de Anticorpos , Asma/imunologia , Distribuição de Qui-Quadrado , Criança , Pré-Escolar , Poeira/análise , Georgia/epidemiologia , Humanos , Imunização/estatística & dados numéricos , Imunoglobulina E/sangue , Razão de Chances , Pobreza/estatística & dados numéricos , Prevalência , Fatores de Risco , Estudos Soroepidemiológicos , População Urbana/estatística & dados numéricosRESUMO
A group of 20 mite allergic asthmatic children aged 6-12 years old, living in São Paulo, Brazil, was studied regarding their degree of sensitization to house dust mites and exposure to mite allergens in their homes. In 18 out of 20 houses at least one dust sample was obtained which contained greater than 10 micrograms Der p I/g of dust. The highest levels of Dermatophagoides pteronyssinus allergens, Der p I and Group II, were measured in bedding samples (geometric mean 38.4 and 36.6 micrograms/g, respectively), followed by bedroom floor, TV room and kitchen. Mite allergen levels in Brazilian houses were as high as those reported to be associated with sensitization and acute attacks of asthma in other parts of the world. In keeping with previous reports that D. farinae is rarely found in Brazil, Der f I was undetectable or found in very low levels (less than 0.5 micrograms/g). Levels of cat allergen Fel d I of greater than 8 micrograms/g of dust were obtained only in 2 houses only. Cockroach allergen Bla g I was detected in five out of 20 houses. Levels of IgE antibodies to D. pteronyssinus were greater than 200 RAST U/ml in 19 out of 20 children (geometric mean 1588 RAST U/ml). IgE antibodies to cat, cockroach, A. fumigatus, ragweed and rye grass pollens were undetectable or less than 80 RAST U/ml. IgE antibodies to the mite Blomia tropicalis were also measured, and levels greater than 200 RAST U/ml were observed in 13 out of 20 sera.(ABSTRACT TRUNCATED AT 250 WORDS)