The sigma-and omega-class members of the glutathione-S-transferase family from ascaris are IgE binding components with marked differences in the IgG1 and IgG4 response

Ana Milena Lozano-Mendoza, Juana Bustillo, Juan López, Luis Caraballo, Josefina Zakzuk


Background: The family of gluthation-S-transferases possesses several isoforms, one of its members, Asc s 13, is allergenic, but other molecules of this repertoire may have different immunological properties. Different omega-class of gluthatio-S-transferases has been reported as anti-inflammatory molecules.

Objective: To evaluate the antibody response to a new member of the gluthation-S-transferases family from Ascaris suum.

Methods: Recombinant gluthatio-S-transferases omega (rGSTO) and gluthatio-S-transferases sigma or Asc s 13 (rGSTA) from Ascaris suum were obtained in Escherichia coli. Specific IgE, IgG4 and IgG1 levels were determined by ELISA in 183 patients from a rural area of Colombia where ascariasis is endemic. A phylogenetic tree was built with published helminth gluthatio-S-transferases sequences. IgG reactivity to rGSTO and rGSTA was evaluated by ELISA using a polyclonal antibody (pAb) obtained from rGSTA-immunized mice.

Results: These proteins share 20 %/39 % of identity/similarity; low surface amino-acid conservation was also observed. These Ascaris suum-gluthatio-S-transferases clustered in different clades, rGSTO was more similar to other omega-gluthatio-S-transferases and rGSTA to other sigma-class. Anti-rGSTA pAb recognized the immunogen in a dilution-dependent manner, but not the rGSTO. Human IgE recognized both, rGSTA (median OD 405 = 0.127; IQR = 0.111-0.150) and rGSTO (0.122; IQR = 0.109-0.157), with no difference (p = 0.321). Sensitization rates were similar (rGSTA: 32.8 % and rGSTO: 30.6 %, p = 0.65). Human-IgG4 against rGSTO and rGSTA was found in 73.2 % and 41.0 % (p < 0.01). Median anti-GSTO IgG4 (0.174; IQR = 0.14-0.25) was significantly higher than to rGSTA (0.135; IQR = 0.115–0.171). IgG1 reactivity to rGSTA and rGSTO was 84.2 and 95.6 % (p < 0.01), respectively. Median IgG1 levels were significantly higher for rGSTO (0.332; IQR = 0.234-0.466) than to rGSTA (0.176; IQR = 0.140-0.259).

Conclusions: rGSTO is also an IgE binding component of ascaris. No cross-reactivity with rGSTA in immunized mice. Differences in IgG1 and IgG4 responses suggest these isoforms induce different immune response profiles.

Palabras clave

Gluthation-S-transferases; Ascaris suum

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