In Vitro Evaluation of the Efficacy and Safety of a Depigmented-Polymerized Extract of Cat Epithelia

Rationale: Polymerized allergen extracts (allergoids) have a reduced allergenicity respect to native extracts while maintaining their immunogenicity. The objective of the study was to compare the efficacy and safety of a cat epithelia depigmented-allergoid respect to their corresponding native extract, by in vitro studies.

Methods: Depigmented-polymerized (Dpg-Pol) extracts were produced from native extracts from cat dander. The capacity of native and Dpg-Pol extracts (100 mg/ml) to stimulate cytokine production (IL-4, IFN-g, IL-10, IL-17) in PBMCs from cat atopic donors was evaluated at 24-72h using a quantitative ELISA-based test. The strength of IgE-allergen interaction was measured by surface plasmon resonance biosensor analysis in a three step process: Immobilizing anti-human IgE (or anti-sheep IgE as control) on a chip; Injecting a pool of sera from cat atopic donors (or non atopic as controls); Injecting native and Dpg-Pol cat dander extracts and measuring the interaction. The constant of dissociation (Kd) and average time (t½) were determined.

Results: Cellular assays showed that Dpg-Pol and native extracts induced similar production of IFN-g and IL-10 in PBMCs from atopic donors. IL-4 and IL-17 were not detected. The results of Kd and t½ indicated that the strength and average life of the Dpg-Pol extract-IgE interaction were 1.3 to 4 times (depending on the reference used) lower compared to native extract.

Conclusions: Depigmented-polymerized extracts of cat epithelia induced a comparable production of cytokines involved in Th1 and Treg response and a lower interaction with IgE respect to their corresponding native extract at the same concentration, suggesting similar immunological efficacy and higher safety.