An interesting study pertinent to RESPIT was brought to my attention by my friend Dr. Dean Gebroe of Culver City Animal Hospital. You may have noticed the capsule report in the September 2012 Clinician’s Brief entitled “One Allergen to Treat Another Allergy?” Here is my summary of the original article:1
Hypothesis: immunotherapy with allergens not completely matched to sensitizing allergen(s) in experimentally-induced feline asthma can reduce aberrant immune responses.
Methods: In phase I, 19 cats were sensitized to Bermuda grass (BG), housedust mite (HDM), or given a placebo. All cats then received BG immunotherapy for 6 months, beginning with a rush protocol. In phase II, 17 cats were sensitized to both BG and HDM, then received either placebo, BG, or HDM immunotherapy for 6 months.
Bronchoalveolar lavage fluid eosinophils, antigen-specific lymphocyte proliferation, number of IL-10 producing cells, and percentage of regulatory T-cells were measured.
Results: Both BG and HDM immunotherapy resulted in significantly decreased eosinophilic airway inflammation in BG-sensitized cats (p < 0.001), but not the placebo controls (p=0.221). In dually sensitized cats, single allergen immunotherapy with either HD or BG, but not placebo, significantly reduced airway eosinophilia (p = 0.038). Differences in IL-10 and regulatory T-cells were found between cats receiving placebo and single-allergen immunotherapy.
Conclusions: Immunotherapy with allergens which do not completely match the allergen(s) used in asthma induction provided some degree of cross-protection. The mechanism may differ from that when immunotherapy is matched to sensitizing allergens.
Comment: These findings are similar to a study in humans which found that imperfectly matched immunotherapy can be beneficial in the management of rhinitis and bronchial hyperactivity.2 Thus, there is mounting evidence that some of the benefits of immunotherapy are, at least in part, non-specific. This may partially explain why standardized immunotherapy for canine atopic dermatitis is similar in efficacy to customized immunotherapy, and how widely discrepant allergy test results lead to similar immunotherapy efficacy.
1. Reinero C, Lee-Fowler T, Chang C-H, et al. Beneficial cross-protection of allergen-specific immunotherapy on airway eosinophilia using unrelated or a partial repertoire of allergen(s) implicated in experimental feline asthma. The Veterinary Journal 2012;192:412-416.
2. Marogna M, Spadolini I, Massolo A, et al. Effects of sublingual immunotherapy for multiple or single allergens in polysensitized patients. Ann Allergy Asthma Immunol 2007;98:274-280.