Q-170. Allergic Significance of Airborne Trichoderma harzianum, a Common Microbial Biopesticide

S. Das1, A. Adhikari2, S. Gupta-Bhattacharya1;
1Bose Inst., Kolkata, INDIA, 2Univ. of Cincinnati, Cincinnati, OH.

Background: Airborne fungi, a major constituent of atmospheric bioaerosol, are well-known source of allergens and cause allergic rhinitis and bronchial asthma in sensitive subjects. Trichoderma harzianum, a filamentous fungus antagonistic to several plant-pathogenic fungi, is being widely used as a potential biopesticide. Although a high exposure risk is assumable in farms and rural areas, the role of this fungus in provoking allergic symptoms in pre-sensitized individuals, however, was poorly investigated. We conducted this study to monitor airborne T. harzianum and to evaluate its potential as an aeroallergen causing nasobronchial allergy in sensitized individuals. Methods: Seasonal periodicity of T. harzianum was studied for two years (2002-04) by Andersen air sampler. The relationships between meteorological parameters and airborne T. harzianum concentration were explored by linear regression models. The allergic potential of T. harzianum extract was studied on 389 respiratory allergic patients by performing skin prick tests (SPT) and measuring the allergen-specific IgE levels in SPT positive patient sera by ELISA. Spirometry was performed to diagnose lung function impairments among subjects. SDS-PAGE and immunoblotting were performed to identify its IgE-binding components. Results: Airborne T. harzianum concentration range was 4-147 CFU/m3 and reached the peak level in March. Relative humidity was a significant (p<0.05) predictor for the occurrence of T. harzianum in air. Positive skin reaction was observed in 105 patients (27%) including 10 (9.5%) showing markedly high (2+ to 3+) skin sensitization. A definite decrease in FEV1 value (a lung function variable) was detected in 157 (40.4%) subjects. Crude antigenic extract of T. harzianum was resolved in 18 protein bands in the molecular weight range of 12 to 72 kDa on SDS-PAGE (12% gel). Two IgE-binding protein bands (21 and 32 kDa) were detected by immunoblot analysis. Conclusion: Exposures to T. harzianum in environments where it naturally occurs or is used as an active ingredient of biopesticides may confer risk of IgE-mediated sensitization in sensitive individuals.