Luciferase Immunoprecipitation Systems (LIPS) Immunoassay is a Sensitive and Rapid Method for Detection of Allergen Component-Specific IgE

RATIONALE: Current laboratory methods to detect allergen-specific IgE require relatively large sample volumes and use either crude biological extracts or purified recombinant allergens, the latter difficult to obtain in conformationally active forms. We demonstrate the use of synthetic biology coupled with previously-described luciferase immunoprecipitation systems (LIPS) immunoassays as a novel method to detect allergen component-specific IgE in small sample volumes.

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.