Molecular Characterization of American Cockroach Tropomyosin (Periplaneta americana Allergen 7), a Cross-Reactive Allergen

Abstract

Inhalation of allergens produced by the American cockroach (Periplaneta americana) induces IgE Ab production and the development of asthma in genetically predisposed individuals. The cloning and expression in Escherichia coli of P. americana tropomyosin allergen have been achieved. The protein shares high homology with other arthropod tropomyosins (80% identity) but less homology with vertebrate ones (50% identity). The recombinant allergen was produced in E. coli as a nonfusion protein with a yield of 9 mg/l of bacterial culture. Both natural and recombinant tropomyosins were purified by isoelectric precipitation. P. americana allergen 1 (Per a 1) and Per a 7 (tropomyosin) are to date the only cross-reacting allergens found in cockroaches. ELISA and Western blot inhibition experiments, using natural and recombinant purified tropomyosins from shrimp and cockroach, showed that tropomyosin induced cross-reactivity of IgE from patients allergic to these allergens, suggesting that this molecule could be a common allergen among invertebrates.

Genome assembly and annotation of Periplaneta americana reveal a comprehensive cockroach allergen profile

“…Among the verified allergens, the patients showed the highest response rate to the newly identified tropomyosin, where 18 out of 20 patients had an IgE sensitivity greater than the threshold in the ELISA (Figure 2A). The significantly higher sensitization rate in these patients as compared to the 41.4% rate for the known rPer a 7 in ACR‐sensitive patients reported by WHO/IUIS Allergen Nomenclature website could be attributable to heterogeneity among the sensitization profiles of the different patient cohorts 29 …”

“…Our high-quality genome (3.06 Gb) and precisely annotated proteome (29,939) of the American cockroach help revealed a broader allergen spectrum. Seven novel allergen groups Per a 14 to Per a 20 and one isoallergens (Per a 7.02) were validated using ELISA in Thai cohort.…”

“…The significantly higher sensitization rate in these patients as compared to the 41.4% rate for the known rPer a 7 in ACRsensitive patients reported by WHO/IUIS Allergen Nomenclature website could be attributable to heterogeneity among the sensitization profiles of the different patient cohorts. 29 Manual curation with a high-quality genome and transcriptome…”

IgE reactivity patterns in Asian and central European cockroach-sensitized patients reveal differences in primary sensitizing allergen sources

“…Over the last 25 years, several important CR allergens have been purified and characterized; they can now be used for the systematic assessment of the sensitization profiles of allergic individuals. 19 , 22 , 23 , 24 , 25 , 26 , 27 , 28 Component-resolved diagnosis allows for distinguishing between genuine sensitizations, cosensitizations, and cross-reactivities for different allergen sources. 29 With this approach, it has been shown that CR-allergic patients present variable sensitization profiles, without defined immunodominant major CR allergens.…”

“…Moreover, strong IgE cross-reactivity between CR, HDM, and shellfish allergens has been described, in manycases mediated by pan-allergens, such as tropomyosins or arginine kinases. 25 , 27 , 33 …”