Allergenic activity of Glutathione Transferase derived from Blomia tropicalis (Blo t 8)

Abstract

BACKGROUND: The prevalence of allergic diseases has increased worldwide. Blomia tropicalis is a mite of allergenic importance in tropical and subtropical areas. Few allergens from this source have been fully characterized and there is a need to gain a deep insight on the immunological response to its components due to its clinical and academic implications. It has been previously reported that Blo t 8, the glutathione transferase of this mite, has allergenic properties. However, the influence of sensitization on asthma presentation remained unknown. METHODS: The IgE-binding capacity of recombinant Blo t 8 (rBlo t 8) was evaluated by indirect ELISA in 574 subjects living in three different locations of the Department of Bolivar. The asthma case-control study involved 183 asthmatic patients and 200 non-asthmatic controls living in Santa Catalina or Cartagena. Additionally, we compared in 191 subjects the specific IgE response to Blo t 8 between two matched groups of African-descendent subjects (with parents and grandparents born in Palenque) who lived in this rural (93) town or in the urban (91) city of Cartagena. Additionally, we tested if Blo t 8 was able to induce airways inflammation. Three groups of BALB/c mice (n = 6 each) were sensitized i.p. and challenged i.n. with: 1.Alum-adsorbed Blo t 8, 2. phosphate buffer + alum (as negative control) or Alumadsorbed ovalbumin (as positive control). Total and allergen-specific IgE, IgG1 and IgG2a antibodies were measured. The allergenic potential of Blo t 8 was also evaluated in a mouse model of passive cutaneous anaphylaxis and human basophil activation test. RESULTS: Blo t 8 sensitization was higher in controls than in asthmatic patients (64,4% versus 23,9%, respectively). After adjustment by several potential confounders, Blo t 8 sensitization kept as a protective factor for asthma (aOR: 0.1 95%CI: 0.05-0.17). In the two related populations of Palenque origin, it was observed that Blo t 8 specific IgE response was more intense in the rural environment. In regard to the observed results in mice, Blo t 8 induced total and specific IgE roduction; however, contrary to OVA, it did not induce airway inflammation. In regard to the PCA results, the allergenic potential was intermediate, being the highest for OVA and negative for PBS. CONCLUSION: The epidemiological relationship of rBlo t 8 with asthma presentation was in a protective direction. In contrast to classical allergens, sensitization to rBlo t 8 did not induce features of airway inflammation in experimentally sensitized animals.