Insights into Local Grass and Weed Pollen Sensitization in Bangkok, Thailand: IgE Reactivity Patterns, Cross-Reactivity, and Putative Allergens.

Background: Allergic rhinitis (AR) triggered by pollen is a growing global public health concern. This study aimed to: 1) analyze IgE reactivity to grass and weed pollen in Thai AR patients; 2) assess the prevalence and intensity of IgE-reactive protein bands; and 3) investigate cross-reactivity among pollen species.

Methods: Sera were collected from Thai adult AR patients in Bangkok, Thailand, and skin prick test (SPT) data were obtained. ELISA assessed IgE reactivity to pollen extracts from four grasses (Bermuda grass, para grass, Johnson grass, Manila grass) and two weeds (nutsedge, careless weed) using 119 patient sera. Immunoblot identified IgE-reactive protein bands using 65 patient sera with positive SPT. Cross-reactivity was confirmed by immunoblot and ELISA inhibition assays.

Results: Johnson grass showed the highest ELISA optical density (OD) values. Significant positive correlations (r_s = 0.740 to 0.935, p < 0.0001) in IgE reactivity were observed among pollen species, with stronger correlations among grasses. Immunoblot identified 30 kDa and 63 kDa proteins as major IgE-reactive proteins in grasses, and 25 kDa and 75 kDa proteins in nutsedge. Strong positive correlations were found within grass species for number of bands, ELISA OD, and SPT wheal size. A positive correlation existed between ELISA and SPT results (r_s = 0.27, p = 0.030). Inhibition assays confirmed cross-reactivity among grass and weed species.

Conclusion: This study highlights variability in pollen sensitization, cross-reactivity, and potential novel allergens in Thai AR patients. These findings are crucial for enhancing pollen allergy understanding and improving diagnostic and treatment, particularly in tropical/subtropical regions.