METHODS: Sera from healthy volunteers, helminth-infected individuals, and peanut-allergic children were screened for IgE to peanut components or cat using ImmunoCAP. Renilla luciferase (Ruc) fusion protein constructs were synthesized for Fel d 1 (cat) and Ara h 1, 2, 3, 8, and 9 (peanut). Constructs were transfected into 293 cells. LIPS immunoassays were performed with allergen-Ruc fusion proteins and 5-10 ul of serum per component.
RESULTS: Cat IgE levels ranged from 0.36 to >100. For Fel d 1 LIPS, the signal:noise ratio differed significantly between cat IgE- samples and samples with cat IgE > 0.5 (p < 0.01). LIPS signal correlated to cat IgE levels with R2 = 0.779, p < 0.001. For Ara h 1- 3, LIPS detected component-specific IgE in known positive samples and was negative for known peanut- or Ara h 1, 2, and/or 3-negative samples. LIPS for Ara h 8- 9 could not distinguish between samples positive and negative for these components. Assays were completed in less than one hour.
CONCLUSIONS: LIPS immunoassays are a sensitive, rapid method of detecting allergen component-specific IgE in small volumes of human serum, with few limits to the number of possible components for testing.