Dissecting cockroach allergens

Childhood asthma in an urban community: prevalence, care system, and treatment

OBJECTIVES

We describe the system of asthma care in Hartford, CT, an urban, minority community.

METHODS

The health field concept was used to organize factors influencing asthma prevalence and severity. Data were obtained from national, state, and municipal reports, and from surveys of children in Hartford seeking medical care in an asthma program called Easy Breathing.

RESULTS

Between June 1, 1998, and May 1, 2000, 21% of children receiving Medicaid in Hartford did not file a medical claim. Between 1998 and 2000, the number of providers in Hartford decreased by 37% while the number of outpatient visits increased by 8%. Using claims data, we found the following: 19.0% of Hartford children had asthma (data from the International Classification of Disease, ninth revision, and the National Drug Code); and 12% of children with asthma filled a prescription for inhaled corticosteroid therapy, 83% for a bronchodilator, and 36% for an oral corticosteroid. Children with asthma were more likely to be hospitalized (10% vs 5%, respectively) and to visit an emergency department (45% vs 29%, respectively), and, on average, they had more hospital days (0.603 vs 0.415 days per child, respectively) and more outpatient visits per year (4.7 vs 2.5 visits, respectively) compared to children without asthma. Asthma prevalence in the 6,643 children surveyed in the Easy Breathing program was 41%. Persistent asthma was diagnosed in 50% of the children with asthma. Asthma prevalence varied by ethnic origin, age, and gender, and was highest in Hispanic/Puerto Rican children, in children 5 to 10 years of age, in boys up to 10 years of age, and in girls after 15 years of age.

CONCLUSION

Improved personal behaviors and medical care will have a limited sustained impact on childhood asthma until basic environmental issues are modified. The health field concept provides a mechanism with which to address the issues surrounding asthma in urban communities.

Occupational allergic disease in cereal workers by stored grain pests

It is well known that workers occupationally exposed to grain dust have a high prevalence of respiratory symptoms, but their pathogenesis remains obscure when sensitization to cereal flour cannot be demonstrated. Storage mites, tenebroids, and cockroaches are stored-grain pests found in grain and cereal products frequently in our area, where the cereal industry is the most important industry. An epidemiological analysis of sensitization of these stored-grain pests was performed on 4379 patients residing in an area of cereal industries. Fifty grain workers were selected for in vivo diagnostic tests with nine genera of mites, Tenebrio molitor and Blatta orientalis. Specific IgE antibodies to the extracts were demonstrated by prick tests and RAST. Association between respiratory symptoms and occupational exposure was confirmed by challenge tests (specific and methacholine). The prevalence of mite sensitization in the total sample studied (4379) was 18.96% (SEM 0.58, 95% CI 16.93-19.19). The prevalence of sensitization to storage mites among mite-sensitive patients was 11.88% (SEM 1.15, 95% CI 9.63-14.3). Among the 50 selected patients the most frequent sensitization was that to Dermatophagoides pteronyssinus (58%), followed by Dermatophagoides frinae (48%), Lepidoglyphus destructor and Tyrophagus putrescentiae (38%), Blomia kulagini (34%), and Acarus siro and Chortoglyphus arcuatus (24%). In addition, 22% of the patients presented negative prick tests and RAST for Dermatophagoides species with positive test to storage mites. Fifty percent of the 50 patients were sensitizated to Tenebrio molitor (SEM 0.7, CI 95% 36-64), and 36% to Blatta orientalis (SEM 0.67, CI 95% 23-49). The identification of mites, tenebroids, and cockroaches in dust samples yields useful data for the diagnosis of our patients.

Molecular cloning of a major cockroach (Blattella germanica) allergen, Bla g 2. Sequence homology to the aspartic proteases

Inhalation of allergens produced by the German cockroach (Blattella germanica) elicits IgE antibody formation and the development of asthma in genetically predisposed individuals. We compared the allergenic importance of two cockroach (CR) allergens, Bla g 1 and Bla g 2, and determined the complete amino acid sequence of the major 36-kDa allergen, Bla g2. A survey of 106 sera from CR allergic patients showed the prevalence of IgE antibodies to Bla g 1 and Bla g 2 to be 30.2% and 57.6%, respectively. Immediate skin tests on 7 selected patients gave positive reactions using 10(-3) micrograms/ml either allergen, whereas controls showed no response to 10 micrograms/ml. Natural Bla g 2 was purified and the sequence of the NH2 terminus and tryptic peptides, comprising 36% of the molecule, was determined. The cDNA for Bla g 2 was cloned from a B. germanica expression library and encoded a 24-amino acid signal peptide and a 328-amino acid mature protein, which showed the highest degree of identity to mosquito (Aedes aegypti) lysosomal aspartic protease (30.8%), with similar identity to pepsin, cathepsins D and E, renin, and chymosin. Bla g 2 mRNA and protein were detected in B. germanica, but not in Periplaneta americana, the other principal domiciliary CR species in the U.S. High concentrations of Bla g 2 were found in CR digestive organs (esophagus, gut, and proventriculus). The results show that Bla g 2 is a major species-specific allergen of B. germanica and suggest that the allergen functions as a digestive enzyme in the cockroach.