Antigenic proteins involved in occupational rhinitis and asthma caused by obeche wood (Triplochiton scleroxylon).

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.

Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease.

BACKGROUND AND AIMS: Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages. METHODS: Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of 'Groeneveld' and 'Dodoens' grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation. KEY RESULTS: 'Dodoens' had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. 'Groeneveld' had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area. CONCLUSIONS: Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of 'Dodoens' were unaffected by the DED fungus. 'Dodoens' proved to be a valuable elm germplasm for further breeding strategies.

Occupational IgE-mediated softwood allergy: characterization of the causative allergen.

Allergic reactions to wood dust allergens are rare, and only few in vitro diagnostic tools and information about relevant allergens are available. To differentiate between protein-based allergy and probably clinically silent glycogenic sensitization, it is helpful to characterize the relevant protein allergens and specify IgE binding. The current case report deals with the occupational softwood allergy of a carpenter exposed to different wood dusts. Skin tests and IgE tests against wood were performed with specifically tailored ImmunoCAPs and cross-reactive carbohydrate determinants. Potential allergens were identified by IgE blots and tandem mass spectrometry. The clinical relevance was verified by challenge tests. Specific IgE to softwood (spruce, pine and larch wood), beech wood, natural rubber latex (NRL) and horseradish peroxidase (HRP) were detected. Allergens in spruce wood, the dominant allergen source, were identified as peroxidases. Softwood were the strongest inhibitors. HRP reduced IgE binding to softwood to <50%, indicating predominantly proteinogenic epitopes, whereas IgE binding to NRL and beech wood was reduced to >50% by HRP, indicating predominantly glycogenic IgE epitopes. Skin and challenge tests underlined that softwoods were the source of sensitization. For the polysensitized patient, a clinically relevant softwood allergy was diagnosed, not only by challenge tests but also with specifically tailored in vitro tools.

Impact of cross-reactive carbohydrate determinants on wood dust sensitization.

BACKGROUND: Occupational wood dust exposure can induce allergy and may be one cause of respiratory health problems among woodworkers. OBJECTIVE: The objective was to determine the prevalence and quantitative level of specific immunoglobulin E (sIgE) to beech and pine wood in exposed workers. Wood sensitization was specified with regard to cross-reactivity and was correlated to the reported symptoms. METHODS: Danish workers (n=701) were investigated for sIgE to beech and pine. Wood samples from workplaces were analysed and coupled to ImmunoCAPs. Workers sensitized to wood were tested for cross-reactive carbohydrate determinants (CCDs) and environmental allergens. IgE binding was specified for glycogenic vs. proteinogenic epitopes by inhibition tests. RESULTS: The prevalence of wood sensitization among all workers was 3.7%. There was no association between sensitization prevalence or sIgE concentrations and self-reported allergic symptoms. Beech- and pine-sensitized workers showed a high prevalence of CCD sensitization (73%). However, workers with a single sensitization to wood had no sIgE to CCDs. Specifying IgE epitopes demonstrated that sera of workers reporting allergic symptoms recognized proteinogenic IgE-epitopes on wood allergens, whereas workers without allergic symptoms had primarily sIgE-epitopes to glycogenic structures. Although 96% of the wood-sensitized workers were atopic, no significant correlation was found between wood sensitization and sIgE to beech and birch pollen, but an association was found between sIgE against CCDs and pine pollen. CONCLUSION: Sensitization prevalence to beech and pine wood measured by tailored ImmunoCAPs was not correlated to allergic symptoms. We recommend the application of CCD tools to assess the relevance of individual wood sensitization.

A meta-analysis on wood dust exposure and risk of asthma.

Work-related asthma is the most common occupational respiratory disorder in the industrialized countries. It has been postulated that wood dust exposure may increase the risk of work-related asthma. The objective of this study was to assess, through a meta-analysis, the risk of developing work-related asthma associated with wood dust exposure. A systematic search of the literature was performed. Inclusion and exclusion criteria were applied and a quality scale used to measure the quality of the included studies was developed. Using standard meta-analysis techniques, studies were pooled using both random and fixed effects models. Nineteen studies were included which consisted of three cohort studies, twelve case-control studies and four mortality studies. The pooled relative risk (RR) of asthma among workers exposed to wood dust was 1.53 (95% CI 1.25-1.87). When the analysis was restricted to studies carried out on Caucasian populations, the pooled RR was 1.59 (95% CI 1.26-2.00) while the pooled RR of studies on Asian populations was 1.15 (95% CI 0.92-1.44). Wood workers present a higher risk of asthma. Future research should include careful evaluation of ethnicity and nativity as risk modifiers.

Occupational rhinitis and asthma due to cedroarana (Cedrelinga catenaeformis Ducke) wood dust allergy.

We describe a case of occupational rhinitis and asthma in a 46-year-old carpenter who presented nasal and bronchial symptoms after cedrorana (Cedrelinga catenaeformis Ducke) wood dust exposure. Skin prick tests (SPT) with a battery of common allergens and different kinds of wood, were positive to cedrorana and grass pollen and negative to the other wood extracts. Nasal provocation and exposure challenge tests with Cedrorana wood dust also gave a positive reaction. IgE-immunoblotting showed two bands of 45 and 78 kDa respectively. This is the first reported case of occupational rhinitis and asthma due to Cedrorana wood dust where an IgE mediated mechanism has been found.

Accumulation of Isohemigossypolone and Its Related Compounds in the Inner Bark and Heartwood of Diseased Pachira aquatica.

Isohemigossypolone (1) and 2-O-methylisohemigossypolone (2), major fungitoxins of Pachira aquatica, were found to accumulate locally in the outer bark of the swollen trunk, whereas the inner bark and heartwood contained only a trace amount of them. From P. aquatica that was infected with a phytopathogenic bacterium, we detected significant amounts of 1 and 2 from browned inner tissues of the swollen trunk. According to a quantitative analysis by a gas-chromatograph, the concentration of 1 in the diseased inner tissues was calculated to be approximately 780 µg/g f.w., which was the same level as that in the outer bark of healthy individuals. These findings suggest that the inner tissues inducibly produced and accumulated antifungals 1 and 2 during infection events, as do many plants with phytoalexins. 11-Nor-2-O-methylisohemigossypolone (3), showing approximately equivalent fungitoxic activity to that of 1 and 2, was also isolated from the infected inner tissues. We screened pathogenic bacteria from the infected tissue, and isolated a rod-shaped bacterium that was tentatively identified as Pseudomonas sp. which promoted tissue-browning on sectioned disks of P. aquatica trunks.