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


CONCLUSIONS
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.


CONCLUSIONS
Blo t 21, representing a new group of allergens, is an important B tropicalis allergen.
Gao
Yun Feng
YF
Department of Biological Sciences, National University of Singapore, Singapore.
Wang
De Yun
de Y
Ong
Tan Ching
TC
Tay
Su Ling
SL
Yap
Kwong Hsia
KH
Chew
Fook Tim
FT
D000328:Adult; D000485:Allergens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D002648:Child; D003429:Cross Reactions; D016678:Genome; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D008925:Mites / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016415:Sequence Alignment
D000485:Allergens; D007073:Immunoglobulin E