Proof of concept of the preventive efficacy of high-dose recombinant mono-allergen immunotherapy in atopic dogs sensitized to the Dermatophagoides farinae allergen Der f 2.

BACKGROUND: Allergen immunotherapy is currently the only intervention proposed to specifically prevent clinical flares after allergen challenges. The low molecular weight Der f 2 (Df2) is a major allergen in Japanese dogs sensitized to Dermatophagoides farinae house dust mites.

OBJECTIVES: Pilot, blinded, placebo-controlled experiment testing the efficacy of subcutaneous immunotherapy (SCIT) with high doses of recombinant Df2 conjugated to the maltotriose pullulan (rDf2-P).

METHODS: Eight Maltese beagle atopic dogs were sensitized to rDf2 then randomized to SCIT with rDf2-P (six dogs) or placebo (two). The immunotherapy consisted of six weekly injections of increasing doses (0.1-10.0 μg) of rDf2-P followed by four monthly injections of 10 μg of this allergen. Epicutaneous rDf2 challenges, rDf2-specific IgE serology and intradermal reactivity, as well as serum cytokine level measurements, were performed throughout the study.

RESULTS: Subcutaneous injections of placebo did not alter the cutaneous reactivity after rDf2 challenge, while that of the dogs treated with rDf2-P SCIT disappeared in five of six dogs (83%) and was reduced in one of six (17%). During SCIT maintenance, skin lesion scores were significantly lower in dogs receiving SCIT compared to those treated with placebo. This clinical improvement was accompanied by a concurrent, yet not significant, decrease in rDf2-specific IgE serology and immediate intradermal reactivity. Cytokine serum levels were inconclusive. There were no adverse events seen with rDf2-P SCIT.

CONCLUSIONS AND CLINICAL IMPORTANCE: The new mono-allergen SCIT appears safe and effective for reducing skin lesions after allergen challenges; it deserves further testing in dogs with spontaneous atopic dermatitis.