Multi-country IgE reactivity determination of isoforms of the Blomia tropicalis mite allergen Blo t 2 revealed a potential biomarker of asthma severity.

BACKGROUND

Blomia tropicalis is an important source of inhalant allergens in Southeast Asia and Latin America. Previous proteomics identified multiple Blo t 2 isoforms, yet their clinical relevance to Latin American populations and association with asthma phenotypes remain a priority in the field.

OBJECTIVE

To produce and purify the two recombinant isoforms rBlo t 2.2 and rBlo t 2.5 and physicochemically characterize them.

METHODS

Isoforms were expressed in E. coli Shuffle T7 and purified via cation-exchange chromatography. Structural features were verified by mass spectrometry and Fourier-transform infrared spectroscopy. Further, proteolytic stability and LPS-binding activity were determined. IgE-reactivity and allergenic activity were evaluated by Western blot, ELISA and mediator release assays. Sensitization patterns were analyzed in serum samples of Blomia tropicalis-allergic individuals with and without asthma from Brazil, Colombia, and Ecuador.

RESULTS

Both isoforms were correctly folded with proper disulfide bonds and exhibited high stability against endolysosomal proteases. Recombinant Blo t 2.2 lacked specific LPS-binding activity and displayed low cross-reactivity with rDer p 2. Across the three countries, the average sensitization rate to rBlo t 2.2 was 50%. Specifically, sensitization was observed in 47% of Brazilian teenagers and 52% of adults, 53% of Colombian individuals, and 48% of Ecuadorian children and teenagers. Sera from the Ecuadorian study exhibited the highest IgE reactivity. The rBlo t 2.2 isoform displayed significantly higher IgE-binding than rBlo t 2.5 in Brazil. Sensitization to rBlo t 2.2 was significantly more frequent in severe asthma patients than in mild asthma and rhinitis patients.

CONCLUSION

rBlo t 2.2 is a stable, mid-tier to major isoform and a candidate biomarker for severe asthma in Brazil. Its structural and immunological characteristics support its inclusion in molecular diagnostic panels. However further investigations with larger sample sizes and application of multivariate analyses are still warranted to confirm our findings.