title: The influence of chitin on the immune response to the house dust mite allergen Blo T 12.
abstract: BACKGROUND
  Information about the biological properties of Blomia tropicalis allergens is scarce. It is predicted that Blo t 12, an allergen with two described isoforms, contains a chitin-binding domain, similar to that found in peritrophins. Th2 adjuvant properties have been described for chitin. Therefore, it is feasible that binding to this carbohydrate influences its allergenicity. We aimed to evaluate the chitin-binding activity of Blo t 12 isoallergens and its effect on airway inflammation and antibody responses in a murine model of allergen sensitization.
  
  
  METHODS
  Chitin-binding assays were conducted with the recombinant isoallergens Blo t 12.0101 and Blo t 12.0102. BALB/c mice were sensitized via i.p. with any of the two isoforms (alone, with chitin or alum) and then challenged intranasally. Methacholine-induced bronchial hyperreactivity was tested by whole-body plethysmography and lung sections were stained with hematoxylin and eosin and periodic-acid Schiff. Total IgE and allergen-specific IgE, IgG1 and IgG2 levels were measured by ELISA.
  
  
  RESULTS
  The two isoforms bound chitin, but Blo t 12.0101 showed a stronger binding capacity. Both isoforms induced total and allergen-specific IgE, airway hyperreactivity, bronchial inflammation and mucus secretion without any adjuvant; however, when administered with chitin, Blo t 12.0101 induced higher total IgE levels. The IgG1/IgG2a ratio was significantly higher in mice immunized with Blo t 12.0101 than those immunized with Blo t 12.0102. As peritrophins, Blo t 12 was detected in mite feces.
  
  
  CONCLUSIONS
  Blo t 12 isoforms are chitin-binding proteins that induce airway inflammation and bronchial hyperreactivity. However, for Blo t 12.0101, chitin reinforces its effects on total IgE production.
authors: Institute for Immunological Research, University of Cartagena, Cartagena, Colombia.
authors: Josefina
authors: J
authors: Zakzuk
authors: Inés
authors: I
authors: Benedetti
authors: Enrique
authors: E
authors: Fernández-Caldas
authors: Luis
authors: L
authors: Caraballo
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D039741:Antigens, Dermatophagoides / Q000737:chemistry / Q000276:immunology*; D016535:Bronchial Hyperreactivity / Q000276:immunology; D002457:Cell Extracts; D060833:Cellular Microenvironment; D002686:Chitin / Q000276:immunology* / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D056724:Immunity, Humoral; D007073:Immunoglobulin E / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D020033:Protein Isoforms / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D039981:Pyroglyphidae / Q000276:immunology; D012130:Respiratory Hypersensitivity / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D039741:Antigens, Dermatophagoides; C587927:Blo t 12 allergen, Blomia tropicalis; D002457:Cell Extracts; D010446:Peptide Fragments; D004364:Pharmaceutical Preparations; D020033:Protein Isoforms; D002686:Chitin; D007073:Immunoglobulin E