Blo T 2.2 Reactivity Varies Across Countries And Asthma Phenotypes

In paired testing of Blo t 2 isoforms, rBlo t 2.2 showed significantly higher IgE reactivity than rBlo t 2.5 when analysis was restricted to reactive sera. Investigators compared isoform-specific responses across allergic cohorts from Brazil, Colombia, and Ecuador and examined differences across asthma phenotypes. They also reported that both recombinant proteins were correctly folded with proper disulfide bonds and were highly stable against endolysosomal proteases. The analysis centered on how isoform-specific reactivity varied by region and across allergic respiratory disease phenotypes.

The study analyzed 233 sera overall, beginning with Brazilian teenagers aged 12 to 18 in an initial paired-isoform screen. Broader comparisons then included Brazilian adults, Colombian individuals, and Ecuadorian children and teenagers, with ages spanning 3 to 82 years. Allergic participants had a clinical history of allergy, a positive skin prick test to B. tropicalis extract, and specific IgE above 0.70 kU/L. IgE positivity in ELISA was defined by a cutoff set at the mean plus 3 standard deviations of non-allergic sera. Structural analyses indicated preserved folding, intact disulfide bonds, and sustained stability, framing the comparisons that followed.

Across the Brazil, Colombia, and Ecuador cohorts, sensitization to rBlo t 2.2 was identified in 87 of 174 allergic patients overall. Country-specific sensitization rates were 52% in Brazilian adults, 53% in Colombian participants, and 48% in Ecuadorian children and teenagers, placing the response near one half in each setting. Investigators reported the highest IgE absorbance values in Ecuadorian sera, separating response intensity from sensitization prevalence across settings. Reactivity to rBlo t 2.2 correlated strongly with B. tropicalis extract IgE in all three countries. Taken together, the regional contrast was described as reflecting signal intensity more than large differences in sensitization frequency.

Across asthma phenotypes, sensitization to rBlo t 2.2 appeared more frequent in severe asthma than in mild asthma or allergic rhinitis. Investigators also noted higher IgE reactivity in severe and mild asthma than in allergic rhinitis without asthma. Within the severe-asthma subgroup, non-reactive patients were reported more often in the high-dose corticosteroid category, while reactive patients were reported more often in the intermediate-dose category, describing a treatment-use pattern within that subgroup. The authors emphasized that this association remained preliminary because the phenotype groups were imbalanced and larger multivariable analyses are still needed.

The authors concluded that rBlo t 2.2 could be a candidate biomarker for severe asthma in Brazil and suggested it may be relevant for molecular diagnostic panels, while noting that larger studies and multivariate analyses are still needed. They framed this interpretation around the observed phenotype signal and the stronger paired IgE binding of rBlo t 2.2 relative to rBlo t 2.5. The finding was not presented as a standalone diagnostic conclusion and was described within the study population examined. Overall, the work linked isoform-specific sensitization with geography and asthma phenotype through an author-reported multicountry pattern.

Key Takeaways

• In paired analysis restricted to reactive sera, rBlo t 2.2 showed higher IgE reactivity than rBlo t 2.5, and both recombinant isoforms were described as structurally stable.
• Sensitization to rBlo t 2.2 was observed in about half of allergic sera across Brazil, Colombia, and Ecuador, with the highest absorbance in Ecuadorian samples.
• More frequent sensitization to rBlo t 2.2 was observed in severe asthma, and the authors characterized that association as preliminary.