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Keywords:

  • exhaled nitric oxide;
  • induced sputum;
  • occupational asthma;
  • specific inhalation challenge;
  • tampico fiber

Tampico fiber is extracted from the leaves of Agave lechugilla which grows mainly in Mexico. The material is used extensively for making yard brooms, deck brushes and bath brushes. Agave-induced irritant contact dermatitis has been previously reported among workers with Agave tequilana for tequila making (1, 2). Allergic reactions caused by tampico fibers have not been previously reported.

We surveyed the five employees (two supervisors and three machine operators) at a brush making-plant. The two supervisors (patients 1 and 2), who were brothers and had been exposed to tampico for 13 and 10 years, respectively, reported work-related rhinitis and asthma symptoms. Patient 1 also experienced localized contact urticaria with tampico fiber. Patient 1 had experienced rhinitis and asthma symptoms for 10 and 2 years, and patient 2 for 8 and 5 years, respectively. The remaining workers did not report symptoms at work. Exhaled nitric oxide (eNO) measurements (Nioxmino; Aerocrine, Solna, Sweden) performed at the end of the work shift were elevated only in the two symptomatic employees (44 and 83 ppb), whereas they were normal in the remaining workers (<23 ppb). The mean concentration of total dust particles in the brush-making plant during an ordinary work shift using a laser-based aerosol monitor (DustTrack model 8520; TSI, St. Paul, MN, USA) was 0.42 mg/m3 (range: 0.28–0.68).

After obtaining written informed consent, single blind specific inhalation challenges (SIC) were carried out. On visit 1, methacholine inhalation test and sputum induction was performed. On visit 2, the patients underwent a SIC with nebulized aqueous tampico extract (3). Twenty-four hours later, on visit 3, sputum induction was performed again. On visit 4, a week apart from the tampico SIC, the patients underwent a SIC with horsehair extract.

Spirometry results were normal. Sputum was processed as previously described (4) and analyzed using FC scan cytometry (FACSCalibur flow cytometer; Becton Dickinson, San José, CA, USA). Monoclonal antibodies (Pharmingen, San Diego, CA, USA) used to identify sputum cells are described elsewhere (4).

Skin prick testing with tampico extract 10% w/v was positive in patient 1 (5 mm) and patient 2 (3 mm), whereas it was negative with horsehair extract. Both patients also had positive skin prick tests to grass pollen, and patient 2 to house dust mites and cat and dog dander. The remaining workers had negative skin tests to tampico and horsehair extracts.

PC20methacholine was 0.9 mg/ml (patient 1) and 8 mg/ml (patient 2). SIC with tampico at 10% w/v elicited an isolated early asthmatic response in both patients. An increase in sputum total cell count and neutrophils count (about threefold) as well as in eosinophil counts (fourfold) in induced sputum were observed 24 h after SIC. Two subjects with asthma underwent the same challenge protocol with tampico and no relevant changes in forced expiratory volume in 1 s or sputum were observed. The increase in eosinophil counts in sputum after tampico SIC in the patients, as well as the negative results obtained with exposure to horsehair support the specificity of the airway reaction to tampico. There is still conflicting evidence regarding the usefulness of eNO in the investigation of occupational asthma (5). A study reported an increase of eNO in individuals with symptoms of asthma when exposed to laboratory animals (6).

Sodium dodecylsulphate-polyacrylamide gel electrophoresis revealed several protein bands ranging from 14 to 97 kDa (Fig 1A). Immunonoblotting was performed using the patient’s serum diluted at 1/10, incubated overnight, and revealed with a second antibody (antihuman IgE) diluted at 1/5000. Three IgE-binding bands were recognized in the tampico extract of about 31, 39 and 43 kDa (Fig. 1B). These results point out that tampico fibers may give rise to upper and lower airway symptoms as well as to airway inflammation through an IgE-dependent mechanism.

image

Figure 1.  SDS-PAGE (A) and immunoblotting (B) of tampico fibers showing IgE-binding bands with serum from the two patients (lanes 1 and 2) and no reactivity with negative control serum (lane 3).

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