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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.

An aerobiologic survey using a rotoslide sampler was conducted daily (January 1979 through December 1981) in Tampa, Florida. A major tree pollen season (Dec. through May) consisted of oak, pine, Australian pine, bald cypress, cedar, bayberry and mulberry. A minor tree season (Oct. and Nov.) consisted of Australian pine and elm. Grass pollen was found throughout the year and most prevalent April through October. A major weed pollen season (May through Dec.) consisted of ragweed, Mexican tea, pigweed, dog fennel, and false nettle. A minor weed season (March through July) consisted of sorrel and dock.

Thirty-eight subjects were challenged (25 nasal, 13 bronchial) with Bahia grass, Paspalum notatum, pollen extract. A positive Bahia intradermal skin test predicted a positive challenge to Bahia in all (11/11) of the nasal challenges and 75% (6/8) of the bronchial challenges. All 19 subjects with negative Bahia intradermal skin tests had negative challenges with Bahia. Specific IgE antibodies to Bahia pollen were detected by conventional RAST (greater than or equal to 2+) in 82% (14/17) of subjects with positive challenges and in 5% (1/20) of subjects with negative challenges. Eight subjects had positive intradermal skin tests to either Bahia (three) or timothy, Phleum pratense (five). Seven of the eight subjects reacted exclusively to either Bahia or timothy nasal challenge as predicted by their skin tests. Bahia grass is a significant aeroallergen, which in some subjects can be demonstrated not to cross-react with timothy.