An allergenic polypeptide representing a variable region of hsp 70 cloned from a cDNA library of Cladosporium herbarum.
BACKGROUND: Extracts of Cladosporium herbarum, a major source of fungal aeroallergens, exhibit a complex profile of IgE-binding proteins. Yields of conventionally purified allergens from this mold have been insufficient to permit further molecular analyses. OBJECTIVE: To enhance and simplify the purification of allergens from C. herbarum, we have sought to use recombinant DNA techniques to clone, identify and bacterially express immunoselected C. herbarum allergens. METHODS: We constructed a cDNA library in lambda ZAP II using mRNA isolated from C. herbarum. From this library, phage clones encoding a new allergen were immunoselected using pooled human atopic IgE. The cloned cDNA was excised from the phage vector as a recombinant pBluescript II SK-phagemid and sequenced. Expression of the recombinant allergen was carried out in E. coli XL1-blue transformants of the phagemid. Bacterial lysates from cells induced to express the cloned allergen were immunoblotted and probed with individual human atopic IgEs. RESULTS: The cDNA clone encodes a 278 amino acid polypeptide homologous to the C-terminal portion of 70 kDa heat shock protein (hsp 70). The polypeptide possesses features common to other hsps 70, i.e. a similar hydropathic profile and a variable C-terminal region with conserved sequence at the very C-terminus. Binding of the recombinant peptide to IgE from 38% of atopic sera or plasma from individuals allergic to C. herbarum was demonstrated. CONCLUSION: These results indicate that amino acid substitutions are relatively conserved even in the variable C-terminal regions of hsp 70 species. Thus, this study should draw attention to the possibility of induction of anaphylactic responses in a sensitized individual when hsp 70 from any pathogenic species is administered for vaccination.