Mite amylase from Blomia tropicalis (Blo t 4): differential allergenicity linked to geographical regions.

BACKGROUND

Blomia tropicalis is an important domestic dust mite in the tropics and subtropics. This study describes cDNA cloning of the group 4 allergen of B. tropicalis, and the evaluation of the sensitization of this allergen in atopic populations from 2 geographic regions.

METHODS

cDNA cloning was carried out using the Smart RACE cDNA amplification kit. The full-length Blo t 4 cDNA was isolated by cDNA library screening, 5' and 3' rapid amplification of cDNA ends and long-distance PCR. Sequence analysis was performed with a combination of the Clustal W, CGC and Blast program packages. The cDNA was expressed in Pichia pastoris yeast. The skin prick test was used to evaluate the sensitization profile of recombinant Blo t 4, crude dust mite allergen extracts and major B. tropicalis recombinant allergen Blo t 5.

RESULTS

The cloned Blo t 4 had a molecular weight of 56 kDa and had 68% amino acid homology with group 4 allergens of Dermatophagoides pteronyssinus and 65% with those of Euroglyphus maynei. A sensitization profile to the expressed recombinant Blo t 4 allergen (28%) showed an unusually higher frequency than to the major allergen Blo t 5 (22%) in allergic subjects from Chengdu, PR China. In comparison, the subjects from Singapore showed very low sensitization to Blo t 4 (4%) compared with Blo t 5 (84%).

CONCLUSIONS

Group 4 allergens of B. tropicalis may be an important dust mite allergen in certain distinct populations.