In vitro evidence of efficacy and safety of a polymerized cat dander extract for allergen immunotherapy

BACKGROUND: Allergy to cat epithelia is highly prevalent, being the major recommendation for allergy sufferers its avoidance. However, this is not always feasible. Allergen specific immunotherapy is therefore recommended for these patients. The use of polymerized allergen extracts, allergoids, would allow to achieve the high allergen doses suggested to be effective while maintaining safety. RESULTS: Cat native extract and its depigmented allergoid were manufactured and biochemically and immunochemically characterized. Protein and chromatographic profiles showed significant modification of the depigmented allergoid with respect to its corresponding native extract. However, the presence of different allergens (Fel d 1, Fel d 2, Fel d 3, Fel d 4 and Fel d 7) was confirmed in the allergoid. Differences in IgE-binding capacity were observed as loss of biological potency and lower stability of the IgE-allergen complex on surface plasmon resonance. The allergoid induced production of IgG antibodies able to block IgE-binding to native extract. Finally, studies carried out with peripheral-blood mononuclear cells from cat allergic patients showed that the allergoid induced IFN-γ and IL-10 production similar to that induced by native extract. CONCLUSIONS: Cat depigmented allergoid induced production of cytokines involved in a Th1 and Treg response, was able to induce production of IgG-antibodies that blocks IgE-binding to cat native extract, and showed reduced interaction with IgE, suggesting greater safety than native extract while maintaining in vitro efficacy.