Wednesday, 13 September 2017 08:59

BASF: Peptide assays for determining allergic potential – Goodbye to experiments on mice Featured

A team of scientists in the department Experimental Toxicology and Ecology at BASF SE in Ludwigshafen, Germany, has refined a method for detecting substances that can trigger allergic skin reactions. This allows the intensity of a substance’s skin-sensitizing effect to be predicted. This is important for assessing not only chemicals’ skin-sensitizing effects (H317) according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), but also their potency (sub-categories 1A and 1B).

After many years of development, methods for testing chemicals for skin sensitization (i.e. the allergenic effect) have been available since 2012. Both the individual assays and a graded test system have also been approved for regulatory testing, with the three single assays implemented in series. However, determining the intensity of a skin-sensitizing substance has been debatable so far. Therefore the only validated method with which this potency can be currently determined is still an animal experiment, the so-called Local Lymph Node Assay (LLNA) using mice.

A team headed by Britta Wareing from BASF SE has now refined one of the officially approved methods to be able to predict the potency of the skin-sensitizing (allergic) effect of chemicals. This means that the experiments on mice could be done away with.

Successful refinement of the Direct Peptide Reactivity Assay (DPRA) for measuring the potency of allergenic potentials: BASF research group. First from right: Britta Wareing.
Photo: BASF SE


For their new test the developers optimized the so-called Direct Peptide Reactivity Assay (DPRA) to create the quantitative Direct Peptide Reactivity Assay (qDPRA) and the kinetic DPRA, so as to address the question of potency assessment. Both methods investigate peptide reactivity to determine the potential for skin sensitization. The underlying hypothesis is that it is only by reacting with proteins that low molecular substances can form antigens, which ultimately trigger the immune reactions. The amount of antigens thus formed determines the potency.


Principle of Haptenization (Wong et al. Frontiers in Pharmacology 2015)

By using 38 substances the group successfully demonstrated that the new methods could correctly predict the potency for 35 substances (92%). The methods were recently published in the journal Toxicology in Vitro and presented at the 10th Congress on Alternatives and Animal Use in the Life Sciences in Seattle, where they met with great interest.

Together with the already established and accepted methods (DPRA, KeratinoSensTM or LuSens and h-CLAT – OCED Guideline Nr. 442C, D or E), qDPRA and kinetic DPRA could recognize skin-sensitizing substances and determine their potency. This means that future assessment of skin-sensitizing effects could in fact be conducted completely without the use of animal tests.

The Globally Harmonized System of Classification, Labelling and Packaging of Chemicals (GHS) subdivides skin-sensitizing substances in the subcategories GHS 1A and 1B for stronger and weaker skin-sensitizing effects.

The development department Alternative Methods at BASF comprises more than 50 staff members in 5 laboratories, has more than 20 methods in use and almost as many again under development. The company’s research and its interest in the adoption of these methods into test guidelines have made a substantial contribution to replacing animal experiments in the areas of skin irritation, skin corrosion, eye irritation, serious eye damage and skin sensitization.

Original publication:
Wareing B, Urbisch D, Kolle SN, Honarvar N, Sauer UG, Mehling A & Landsiedel R (2017): Prediction of skin sensitization potency sub-categories using peptide reactivity data. Toxicology in vitro. 21. August 2017. https://doi.org/10.1016/j.tiv.2017.08.015

Further information:
Guidance Document on the Reporting of Defined Approaches and Individual Information Sources to be Used within Integrated Approaches to Testing and Assessment (IATA) for Skin Sensitization, Nr. 256, ENV/JM/MONO(2016)29)
OECD TG 442C: http://www.oecd-ilibrary.org/environment/test-no-442c-in-chemico-skin-sensitisation_9789264229709-en;jsessionid=1c2323dvhzrsi.x-oecd-live-02
OECD TG 442E: http://www.oecd-ilibrary.org/environment/test-no-442e-in-vitro-skin-sensitisation_9789264264359-en;jsessionid=1c2323dvhzrsi.x-oecd-live-02
OECD TG 442 D: http://www.oecd-ilibrary.org/environment/test-no-442d-in-vitro-skin-sensitisation_9789264229822-en;jsessionid=1c2323dvhzrsi.x-oecd-live-02