METHODS: A predicted omega-class GST (accession number: ERG80824) from Ascaris suum (rGSTO) was produced in BL21(DE3). Glutathione transferase related-activities were determined spectrophotometrically. Affinity binding to Glutathione Agarose was also assessed and compared with different allergenic GSTs. rGSTO-specific IgE was determined by ELISA in 174 subjects from an A. lumbricoides endemic rural area (infection rate: 66%) and 74 asthmatic patients from Cartagena, Colombia. Anti-Asc s 13 polyclonal antibodies (pAb) were tested against rGSTO to assess cross-reactivity.
RESULTS: In contrast to other GSTs (Blo t 8, Der p 8 and Asc s 13) rGSTO did not exhibit any binding to glutathione-agarose, neither GST activity against CDNB. Among other activities reported for omega-class GSTs, rGSTO showed dehydroascorbate reductase (2.74 ± 0.08 μmol/min/mg) and thioltransferase activity (2.14 ± 0.08 μmol/min/mg). A higher frequency of sensitization was found in asthmatic patients (51%) compared with sigma-class Asc s 13 (18%). In the rural population, IgE recognition of rGSTO was not different between Ascaris infected (32.2%) and uninfected subjects (28.8%, p=0.21). Positive correlation between specific-IgE levels to rGSTO and Asc s 13 (Spearman-rho: 0.59, p=0.01), but anti-Asc s 13 mouse pAbs did not recognize rGSTO.
CONCLUSIONS: rGSTO is a newly described allergenic member of the GST family from Ascaris with the expected omega-class biological properties. Dual sensitization to the sigma-class and omega-class Ascaris GSTs seems to be related with co-sensitization rather than cross-reactivity.