ABSTRACT
BACKGROUND: Obeche wood dust is a known cause of occupational asthma where an IgE-mediated mechanism has been demonstrated. OBJECTIVE: To characterize the allergenic profile of obeche wood dust and evaluate the reactivity of the proteins by in vitro, ex vivo and in vivo assays in carpenters with confirmed rhinitis and/or asthma MATERIALS AND METHODS: An in-house obeche extract was obtained, and two IgE binding bands were purified (24 and 12 kDa) and sequenced by N-terminal identity. Specific IgE and IgG, basophil activation tests and skin prick tests (SPTs) were performed with whole extract and purified proteins. CCD binding was analyzed by ELISA inhibition studies. RESULTS: Sixty-two subjects participated: 12 with confirmed occupational asthma/rhinitis (ORA+), 40 asymptomatic exposed (ORA-), and 10 controls. Of the confirmed subjects, 83% had a positive SPT to obeche. There was a 100% recognition by ELISA in symptomatic subjects vs. 30% and 10% in asymptomatic exposed subjects and controls respectively (p<0.05). Two new proteins were purified, a 24 kDa protein identified as a putative thaumatin-like protein and a 12 kDa gamma-expansin. Both showed allergenic activity in vitro, with the putative thaumatin being the most active, with 92% recognition by ELISA and 100% by basophil activation test in ORA+ subjects. Cross-reactivity due to CCD was ruled out in 82% of cases. CONCLUSIONS: Two proteins of obeche wood were identified and were recognized by a high percentage of symptomatic subjects and by a small proportion of asymptomatic exposed subjects. Further studies are required to evaluate cross reactivity with other plant allergens.
Subject(s)
Asthma/immunology , Malvaceae/immunology , Occupational Diseases/immunology , Plant Proteins/immunology , Rhinitis/immunology , Wood/immunology , Adolescent , Adult , Allergens/immunology , Allergens/isolation & purification , Asthma/blood , Asthma/etiology , Electrophoresis, Polyacrylamide Gel , Enzyme-Linked Immunosorbent Assay , Female , Humans , Immunoglobulin E/blood , Immunoglobulin E/immunology , Immunoglobulin G/blood , Immunoglobulin G/immunology , Male , Malvaceae/metabolism , Middle Aged , Occupational Diseases/blood , Occupational Diseases/etiology , Occupational Exposure/adverse effects , Plant Proteins/isolation & purification , Rhinitis/blood , Rhinitis/etiology , Skin Tests , Wood/metabolism , Young AdultABSTRACT
BACKGROUND: Anaphylaxis after the first exposure to a food allergen is uncommon unless a cross-reaction is present. OBJECTIVE: To investigate a possible relationship between the fruit Cyphomandra betacea Sendth (commonly known as tamarillo) and the wood of Triplochiton scleroxylon (obeche) in a patient with allergic occupational bronchial asthma due to obeche wood who began to experience anaphylaxis episodes after eating tamarillo. METHODS: A 33-year-old carpenter exposed to obeche wood in his occupation was initially seen with rhinitis and bronchial asthma. The causal relationship of these symptoms to obeche wood exposure was investigated by means of peak flow monitoring and bronchial inhalation testing. Furthermore, the patient had 2 acute episodes of anaphylaxis a few minutes after eating salad containing tamarillo. He had never tasted tamarillo before. The allergologic study included skin prick tests, serum specific IgE determinations, bronchial challenges, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunoblotting. RESULTS: Results of skin prick tests with common aeroallergens were negative. Strong skin prick test responses were obtained with obeche and tamarillo. Results of bronchial challenge testing with obeche extract were positive. In tamarillo extract, a 28-kDa band appeared as the most relevant IgE-binding antigen. A similar band of 28 kDa happens to be frequently detected in obeche-allergic patients. CONCLUSION: To our knowledge, this is the first reported case of anaphylaxis to tamarillo presented in a patient allergic to obeche, which raises the question of a new cross-reactivity antigen.
