Identification and characterization of a novel allergen from Blomia tropicalis: Blo t 21

J Allergy Clin Immunol. 2007 Jul;120(1):105-12. doi: 10.1016/j.jaci.2007.02.032. Epub 2007 Apr 18.


Background: Allergenic components from Blomia tropicalis are important triggers of allergies in the tropics.

Objective: We sought to identify and characterize a novel allergen, Blo t 21, from B tropicalis.

Methods: Blo t 21 was initially identified from an expressed sequence tag database generated from a B tropicalis cDNA library. Allergenicity of this antigen was examined by means of skin prick testing, ELISA, and IgE immuno-dot blotting. We evaluated whether Blo t 21 and Blo t 5 were cross-reactive by using IgE inhibition ELISAs.

Results: Blo t 21, a 129-amino-acid protein sharing 39% identity with Blo t 5, is a product of a single-copy gene. It has an alpha-helical secondary structure and localizes to midgut and hindgut contents of B tropicalis, as well as fecal particles. Positive responses to Blo t 21 were shown in 93% (40/43) by means of ELISA and 95% (41/43) by means of skin prick testing when assayed in 43 adult patients with ongoing persistent allergic rhinitis. However, sera of 494 consecutive individuals attending outpatient allergy clinics over 1(1/2) years showed 57.9% (286/494) had positive responses to Blo t 21. Although the majority (>75%) of sensitized individuals were cosensitized to both Blo t 5 and Blo t 21, these 2 allergens had a low-to-moderate degree of cross-reactivity.

Conclusion: Blo t 21 is a major allergen in B tropicalis that is not highly cross-reactive to Blo t 5, despite sharing some sequence and structural identity.

Clinical implications: Blo t 21, representing a new group of allergens, is an important B tropicalis allergen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Allergens / chemistry
  • Allergens / genetics
  • Allergens / immunology*
  • Amino Acid Sequence
  • Animals
  • Child
  • Cross Reactions
  • Genome
  • Humans
  • Immunoglobulin E / immunology
  • Mites / genetics
  • Mites / immunology*
  • Molecular Sequence Data
  • Protein Structure, Secondary
  • Sequence Alignment


  • Allergens
  • Immunoglobulin E