Sera from 42 patients allergic to A. alternata (18 female and 24 male; mean age, 20.5 years; age range, 10–33 years) and 17 control subjects (11 female and six male; mean age, 32.3 years; age range, 14–70 years) were included in the study. Diagnosis of A. alternata allergy was based on a clinical history of recurrent rhinitis (four patients), asthma (four patients), rhinoconjunctivitis (12 patients), rhinitis and asthma (12 patients), rhinoconjunctivitis and asthma (10 patients); a positive cutaneous response to a commercial A. alternata extract (Bial-Arístegui, Bilbao, Spain); and specific IgE to A. alternata extract > 0.35 IU mL−1 according ImmunoCAP (Thermo-Fisher,
to A. alternata, as demonstrated by negative SPT responses and lack of A. alternata-specific IgE, were used as controls. Standard molecular genetic techniques were used (Sambrook et al., 1989). For Southern blotting, genomic DNA was prepared from recombinant yeasts as previously described (Barth & Gaillardin, 1996). Afterwards, DNA was digested, separated on a 0.8% agarose gel, and transferred onto Hybond-N+ nylon membranes (GE-Healthcare, Little Chalfont, Buck, UK). Probes were labeled with [32P]-dCTP using the MegaPrime Kit (GE-Healthcare). The autosomal vector pMM4 was used to express the Alt a 1 allergen. The YlMETII promoter was obtained from plasmid pSG70 (García, 1993; Domínguez et al., 2003) and cloned between the EcoRI-BamHI restriction sites of the pBluescript-SK. The Alt a 1-coding gene sequence (Asturias et al., 2003) 4-Aminobutyrate aminotransferase was cloned after this promoter into the BamHI site, resulting in the pMMR2 vector. As the insertion of the target gene between yeast promoter and terminator sequences produces more efficient expression of heterologous genes in Y. lipolytica (Franke et al., 1998), the YlSTE7 terminator was amplified using specific primers and cloned into the SpeI and XbaI-restriction sites of pMMR2, resulting in the pMMR3 plasmid. This plasmid
was digested with ClaI and XbaI and the 1.8 kb-fragment containing the fusion of the YlMTPII promoter-Alt a 1-YlSTE7-terminator was purified and inserted into the pINA240 plasmid (Barth & Gaillardin, 1996), giving rise to pMMR4. The correct construction was verified by sequencing. The construction of the integrative plasmid pMMR10 was performed as follows. To create the pMMR10 plasmid, the 1.8-kb ClaI-SphI fragment from pMMR4 carrying the YlMTPII promoter-Alt a 1-YlSTE7-terminator fusion was cloned into the pINA62 plasmid. The correct construction was verified by sequencing. Plasmid maps of pMMR4 and pMMR10 and sequences of the specific primers used for YlSTE7 terminator amplification are available as Supporting Information (Fig. S1, Table S1). nAlt a 1 was purified from A. alternata CBS 603.78 spent culture medium after 3 weeks of static growth in Czapeck broth at 25 °C.