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.
Cheong
Nge
N
Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Ramos
John Donnie A
JD
Tang
Chwee Ying
CY
Chng
Hiok Hee
HH
Yao
Rong
R
Liang
Zongan
Z
Lee
Bee Wah
BW
Chua
Kaw Yan
KY
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D052179:Antigens, Plant; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003001:Cloning, Molecular; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology / Q000276:immunology*; D008875:Middle Aged; D008925:Mites / Q000201:enzymology / Q000276:immunology*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment; D012846:Singapore / Q000453:epidemiology; D012882:Skin Tests; D055815:Young Adult; D000516:alpha-Amylases / Q000235:genetics / Q000276:immunology*
D000485:Allergens; D052179:Antigens, Plant; D011994:Recombinant Proteins; C094701:allergen Blo t 5; D000516:alpha-Amylases