Physiological Study to Determine the Allergic Skin Activity After Different Skin Preparation

BACKGROUND INFORMATION The prevalence of allergic diseases has been continuously increasing, reaching a prevalence of up to 30% in industrialized countries. In Switzerland, about 2 million people are affected by IgE-mediated allergies as reported by the Swiss Center for Allergy, Skin and Asthma and the Swiss Society for Allergology and Immunology (SSAI). By subcutaneous injections of gradually increasing allergen doses, conventional subcutaneous SIT (SCIT) is found to reduce the inappropriate T-helper (Th) 2 responses and IgE production. Due to the risk of systemic allergic side effects, the typical therapy duration of 3-5 years and the requirement of 50-80 injections, patient acceptance of SCIT is low and less than 5% of allergy patients choose to undergo SCIT. A recently rediscovered route of allergen administration is via the epidermis in a procedure called epicutaneous immunotherapy (EPIT).

The skin is an attractive administration route for immunotherapy being both easily accessible as well as playing an important role in the immune system consisting of keratinocytes, Langerhans cells (LC), dermal dendritic cells (DC). A major challenge in EPIT is to overcome the physiological barrier function of the skin. In order to deliver the allergen to the immunological effector cells in the skin, the allergen must be transported through the outermost keratinized layer of the epidermis, called the stratum corneum. The stratum corneum is 10-20μm thick and impermeable for molecules greater than 500 Da. Proteins, such as allergens, do not passively permeate across the skin and therefore enhancement strategies are needed to enable this transfer. Advances in microtechnology might contribute to improve the situation by allowing for the miniaturization of mechanics and structures. As the stratum corneum is only 10-20μm thick, it has been proposed by Henry et al., that microneedles as small as a few tens to a few hundreds of microns, could be used to penetrate the stratum corneum.

Such new methods of overcoming the skin barrier raise the question of the influence of different types of skin injury patterns on the allergic skin reactivity. Namely, how important is the role of the exposed area (microneedles), the depth of injury (skin pricking) and the keratinocyte activation. This physiological question is in the focus of this study.

PRODUCTS In order to investigate the physiological reactions concerning different skin conditions and allergen exposition the following products/techniques have been chosen for the purpose of inducing different skin conditions in a reproducible way.

Prick lancet:

For the pricking skin preparation, sterile prick lancets for 1mm point skin testing will be used: prick lancet, produced by Entaco LTD., Redditch, Worcestershire, UK and distributed by Stallergenes®. They are used for allergy diagnostics in daily routine.

Adhesive tape:

For the tape stripping skin preparation a conventional tape will be used (Tesafilm®).

Microneedle array:

To induce a large number of microchannels with a maximal depth of 150μm into the cornea layer,the solid Microstructured Transdermal System (sMTS) by 3M® will be used. This system is a small patch of 351 tiny needles, which is on the market in the US and is intended for preparing the skin for transdermal application of topical dermatology products.

Epicutaneous allergen solution:

For the epicutaneous administration four ten-fold serial dilutions (10 HEP, 1 HEP, 0.1 HEP and 0.01HEP/ml) of registered allergen extracts of birch pollen (Betula verrucosa) (Soluprick®, ALK-Abelló A/S, Hørsholm, Denmark) will be used as in everyday allergy diagnostic practice. Histamine as positive control will be used at 10 mg/ml and a solution containing only the excipients will serve as negative control.

This is an open-label physiological investigation of the allergic skin reactivity to epicutaneous allergen exposition in allergic patients comparing different methods of skin preparation. The focus of the study is on the skin preparation and not on the specific allergen or allergy, but for reasons of homogeneity a single allergic disease, birch pollen allergy was chosen as the basis for the testing. In order to evaluate the effects of the different skin preparation techniques an intra-individual comparison of the skin reactivity in terms of the immediate phase I reaction to serial dilutions of birch pollen extracts was chosen. The serial dilution approach allows a dose dependent effect evaluation and determination of the mean allergen concentration yielding similar skin reactions - thus differences will be explained mainly by the different skin preparation allowing a quantitative comparison of these techniques.

HYPOTHESIS We will determine which of the three different skin preparation techniques uses higher protein concentration of allergen preparation (Ch10) eliciting a wheal area of the same size as histamine 10 mg/ml will be calculated.

The Null hypothesis therefore would be:

Ch10 is not significantly different between the three skin preparation techniques.