cDNA Cloning and Expression of Blo t 11, the <i>Blomia tropicalis</i> Allergen Homologous to Paramyosin

Abstract

Blomia tropicalis is an important mite species in many parts of the world and the most predominant mite species in tropical countries. The prevalence of sensitization to this species has probably been underestimated because commercial extracts are largely unavailable. Identification and characterization of B. tropicalis allergens is an important step toward understanding the role of this species in allergic sensitization and could provide appropriate reagents for diagnostic and therapeutic procedures. This paper describes the isolation, sequence analysis, expression and allergenicity of a cDNA gene coding for a B. tropicalis allergen with homology to paramyosin, a high-molecular-weight allergen previously identified in Dermatophagoides farinae. The full-length Blo t 11 cDNA gene was isolated by cDNA library screening, 5'-rapid amplification of cDNA ends and long-distance PCR. Sequence analysis was performed with a combination of CLUSTAL W, CGC and BLAST program packages. The cDNA gene was expressed as a GST fusion protein in Escherichia coli and purified by affinity chromatography using the glutathione Sepharose column. Allergenicity of the rBlo t 11 was tested by human IgE dot blot immunoassay. Blo t 11 is a 3,111-bp cDNA gene with a 2,625-bp open reading frame coding for an 875-amino acid protein, exhibiting significant homology with different invertebrate paramyosins. The human IgE dot blot immunoassay showed that the rBlo t 11 reacted positively to 52% (33/63) of sera from asthmatic patients. Blo t 11 is the homolog of Der f 11 exhibiting potentially important allergenic activity.