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Thursday, October 4, 2012

The allergenicity of “hypoallergenic” dogs

It’s a primitive social urge in humans to interact with dogs. So much so that many people found to be clinically sensitive to dogs will own them anyway. In this context, it is not surprising that the search for dogs that elicit a minimal allergic response would claim so much energy, but are there such things as “hypoallergenic” dogs? Vredegoor et al. look at that question in this month’s issue (J Allergy Clin Immunol 2012;130:904-909.e7).

The authors examine levels of the primary dog allergen, Can f 1, in samples from dog fur and skin, and settled and airborne dust from “hypoallergenic” dogs (Labradoodles, Poodles, Spanish water dogs, and Airedale terriers), normal allergenic dogs (Labrador retrievers), and a variety of breeds and mixed breeds that made up the control group. Their results are paradoxical and even ironic.

Poodles and Labradoodles had the highest levels of Can f 1 in their coat and skin; Labrador retrievers had the lowest. Hair and dander shedding was highest from Airedale terriers. Vredegoor et al. report that environmental levels of Can f 1 were not significantly different between “hypoallergenic” dogs and their allergenic counterparts, though homes with covered floors had overall lower environmental levels than homes with exposed floors. The authors note that other identified canine allergens, such as Can f 2 and 3, were not screened due to lack of available methods for analyzing large sample sizes. 

The authors also collected information from owners by administering questionnaires. Dog-allergic owners reported much fewer symptoms with the breeds thought to be hypoallergenic and did not report having different house-cleaning practices than non-allergic owners. It was noted that recent swimming by the dogs had an overall effect of lowering allergen levels and Vredegoor et al. speculated that this could contribute to the lower levels found in Labrador retrievers, which are frequent swimmers.

Vredegoor et al. conclude that there is no evidence that supports the label “hypoallergenic” with respect to dogs, so we asked the authors to comment on a possible explanation for the number of dog-allergic owners who reported experiencing fewer symptoms with certain dogs: Senior author Esmeralda J.M. Seegers-Krop replies, “We believe the health effects can be a kind of placebo effect in these people. It has been seen in cat allergic people as well (they report not to be allergic to their own cat but only to other cats).”

Tuesday, October 2, 2012

Asthma therapies targeting Il-13

This month’s clinical review article by Ingram and Kraft (J Allergy Clin Immunol 2012;130: 829-842) presents exhaustive and timely coverage of a complex issue in asthma treatment, namely, the interface of IL-13 pathophysiology, asthma phenotypes, and IL-13 targeted therapies. The authors take the discussion to foundations of IL-4/IL-13 signaling in asthma before delving into the clinical and investigative implications associated with IL-13 dominance in atopic asthma. The review comprehensively covers current knowledge on the clinical and genetic heterogeneity of asthma, emerging phenotypes and subtypes, biomarker diagnostics, and systemic and targeted therapy responses in well-characterized asthma phenotypes.

Review highlights include:

• Cluster analysis of clinical asthma phenotypes by several research groups, including the consistent finding of eosinophilic, high TH2 cytokine profile asthma and non-eosinophilic, low TH2 cytokine profile asthma.

• Evidence confirming therapeutic efficacy of systemic and targeted therapies in eosinophilic, high TH2 asthma.

• Reports of the successful use of biomarkers in characterizing response to therapy, including recent research involving omalizumab, mepolizumab, and lebrikizumab for patients with severe and/or uncontrolled asthma characterized using clinical and biomarker indices.

• Specific evidence for applying FENO, induced sputum, IgE, and periostin to treatment decision making.

Ingram and Kraft note that traditional and targeted therapies are effective only for eosinophilic, TH2 high asthma patients, leaving a gap in our knowledge about how to effectively manage the low TH2 profile patients. They also remark that TH2 inflammation in asthma patients may be more effectively assessed through the use of combinations of inflammatory and molecular markers, rather than relying on observations of single biomarkers. They conclude by commenting that application of the molecular features of asthma phenotypes, in combination with clinical evidence, is being used to predict response to intervention. They follow by pointing out that the current knowledge base has defined a gap in managing asthma that does not present with a TH2 dominant signature.