In vitro skin sensitization testing of Medical Devices using GARD™

Rose-Marie Jenvert, Angelica Johansson, Olivia Larne, Emelie Danefur, Emil Altonen, Anders Jerre, Robin Gradin, Gunilla Grundström.
SenzaGen, Lund, Sweden.

Introduction
All medical devices need to be evaluated for the end point skin sensitization according to the Biological Evaluation of Medical Devices (ISO 10993-1:2018), today commonly involving in vivo assays. Here, we show that the in vitro assay GARDskin Medical Devices can classify leachables as either skin sensitizers or non-sensitizers in polar and non-polar extraction of Medical Devices.

Conclusion
GARDskin Medical Device

  • is an in vitro alternative for assessment of skin sensitization of Medical Devices
  • is compatible with the extraction vehicles salin, olive oil and sesame oil.

Link to poster

Poster presented at Eurotox, Helsinki, Sep 9, 2019.

Extended solvent selection for in vitro sensitization testing using GARD®

Olivia Larne, Ulrika I Torstensdotter Mattson, Rikard Alm, and Gunilla Grundström.
SenzaGen, Lund, Sweden.

Introduction
The GARD®skin assay is an in vitro assay developed for the assessment of skin sensitizers. It is based on SenzaCells™, a human dendritic-like cell line, and a biomarker signature analyzed by a prediction model including pattern recognition and machine learning.

During the development of the GARD®skin platform, two solvents were used: DMSO (0.1%) and water. To increase the applicability domain of GARD®skin and the possibility to dissolve certain test items, for e.g. hard to dissolve substances and UVCBs, where show a broader range of solvents compatible with GARD®skin. Also, use of higher concentrations of the tested solvents were explored for the possibility to increase test item concentrations.

Concluding highlights
GARD®skin compatible solvents:

  • Acetone
  • DMF
  • DMF/Glycerol
  • DMSO
  • Ethanol
  • Glycerol
  • Isopropanol

Increased applicability domain.

Link to poster

Poster presented at Eurotox, Helsinki, Sep 9, 2019.

 

GARD™air – A novel assay for assessment of chemical respiratory sensitizers based on a genomic platform

Henrik Johansson, Andy Forreryd, Robin Gradin, Angelica Johansson, Olivia Larne, Emil Aaltonen, Anders Jerre, Carl A.K. Borrebaeck and Malin Lindstedt
SenzaGen AB, Lund, Sweden. Department of Immunotechnology, Lund, Sweden.

Introduction
Exposure to chemicals may induce allergic hypersensitivity reactions in skin or respiratory tract. To minimize exposure, chemicals are routinely screened for their sensitizing potential. Proactive identification has historically been performed using animal models, but the use of animals for safety assessment of cosmetics was recently banned within EU. Today, similar trends are spreading both globally and across industry and market segments. Methods for specific identification of respiratory sensitizers are greatly underdeveloped, with no validated, or even widely used assay readily available. Thus, there is an urgent need for development of non-animal-based methods for hazard classification of respiratory sensitizing chemicals.

GARD– Genomic Allergen Rapid Detection – is a state of the art technology platform for assessment of chemical sensitizers (Figure 1). It is based on a dendritic cell (DC)-like cell line, thus mimicking the cell type involved in the initiation of the response leading to sensitization. Following test chemical exposure, induced transcriptional changes are measured to study the activation state of the cells. These changes are associated with the immunological decision-making role of DCs in vivo and constitutes of e.g. up-regulation of co-stimulatory molecules, induction of cellular and oxidative stress pathways and an altered phenotype associated with recognition of xenobiotic matter. By using state-of-the-art gene expression technologies, high informational content data is generated, that allows the user to get a holistic view of the cellular response induced by the test substance.

Conclusion
GARDair is a novel assay for assessment of respiratory sensitizers. It is an adaptation of the GARD platform, utilizing gene expression analysis of predictive biomarker signatures and state-of-the-art data analysis methodology. GARDair has been proven functional and is currently progressing towards industrial implementation and  regulatory acceptance with financial support from the EU programme Horizon 2020. This progress includes scientific verification of results, assay optimization, assay
transfer and formal validation by a blinded ring trial.

Link to poster

A mechanistic reinterpretation of the AOP for skin sensitisation

David W Roberts, Liverpool John Moores University, Liverpool

Introduction – Non-Animal Prediction: the 21st Century Consensus
Because of the biological complexity of the skin sensitisation process no single in chemico or in vitro assay will be an appropriate replacement for an animal-based assay such as LLNA or GPMT…
…to ensure a mechanistic basis and cover the complexity, multiple methods should be integrated into a testing strategy, in accordance with the adverse outcome pathway that describes all key events in skin sensitisation.

We need an ITS based on the KEs of the AOP…but
Is that what we really need?

Conclusion

A single assay, GARD™, predicts sensitisation potential and absence of sensitisation potential better than any of, or combinations of, the OECD guideline assays DPRA, KeratinosensTM (ARE-Nrf2 ) and h-CLAT.

We do not really need an ITS covering all KE’s of the AOP.

Link to poster

Exploration of the GARD applicability domain – Skin sensitization assessment of UVCBs

Poster presented at Eurotox 2018 in collaboration with Lubrizol

Download a copy

U. I.Torstensdotter Mattson1, C. Humfrey2, O. Larne1, H. Johansson1, L. Sweet3 1SenzaGen, Lund, Sweden, 2Lubrizol, Derbyshire, United Kingdom, 3Lubrizol, Ohio, United States of America

Conclusion

This case study demonstrates the broadening of the applicability domain of the GARD assay when assessing UVCBs.

Abstract

In this study, four test items were evaluated. All the test items were “Unknown or Variable composition, Complex reaction products and Biological materials” materials (UVCBs), which were provided by Lubrizol and selected based on existing in vivo data (internal Lubrizol data). Skin sensitizing hazard was assessed using the GARDskin assay, and the GARDpotency assay for further subcategorized the sensitizers into strong 1 A) or weak 1 B) sensitizers according to GHS/CLP classification. The GARDskin predictions for test items 1, 2, 3 and the GARDpotency classifications for test item 2 and 3 were consistent with the in vivo data, whereas test item 4 showed inconsistency between the in vitro and in vivo methods. These results indicate the importance of screening a panel of different vehicles or mixtures thereof, in order to choose the appropriate solvent For one of the Test items, the DMSO extraction procedure generates a negative prediction while the experimental vehicle mixture, Glycerol and DMF, classifies the chemical as a skin sensitizer This case study demonstrates the broadening in applicability domain of the GARDassays when assessing UVCBs.

 

Extended applicability domain with new solvent selection for the GARD platform

Jenvert RM, Larne O, Torstensdotter MattssonU. I., Johansson H, SenzaGen, Lund, Sweden

Introduction
The Genomic Allergen Rapid Detection (GARD) assay is a state of the art in vitro assay developed for the assessment of skin sensitizers. It is based on gene expression analysis of SenzaCells, a human myeloid cell line, after stimulation by the test item.
During the development of the GARD platform, two solvents were used; DMSO (0.1%) and Water. To increase the applicability domain of GARD® and the solubility of certain test items, for e.g. Medical Device extracts and UVCBs, we here show a broader range of solvents compatible with GARD.

Conclusions
Here, we show that the GARD® platform is compatible with the following solvents:
• Acetone
• Ethanol
• Glycerol
• Super refined olive oil

• DMF
• DMSO
• Water
• Isopropanol

Poster download

Exploration of the GARD® applicability domain – Sensitization assessment of UVCBs

Joint poster presented at Eurotox 2018

U. I. Torstensdotter Mattson, C. Humfrey, O. Larne, H. Johansson, L. Sweet
SenzaGen, Lund, Sweden, Lubrizol, Derbyshire, United Kingdom, Lubrizol, Ohio, United States of America

Introduction
The GARD – Genomic Allergen Rapid Detection – platform is a state of the art in vitro assay for assessment of chemical sensitizers. The GARD®skin assay is a powerful tool for assessment of chemical sensitizers, with a predictive accuracy of 94%. In this study, four UVCB test items, provided by Lubrizol and selected based on existing in vivo data (internal Lubrizol data), were evaluated. Sensitizing hazard was assessed using the GARD®skin assay, and the GARD®potency assay further subcategorized the sensitizers into strong (1A) or weak (1B) sensitizers according to GHS/CLP classification. Here we show the importance of using appropriate vehicles in order to predict a correct classification of Test items.

 

Conclusion
A UVCB Test item with poor water and DMSO solubility was assessed using a mixture of vehicles with different polarity indexes (DMF and Glycerol 1:1). This experimental vehicle mixture classified the UVCB as a skin sensitizer, being consistent with the in vivo data. This case study demonstrates the broadening of the applicability domain of the GARD -assay when assessing UVCBs.

Poster dowload

The Validation of GARD™skin and GARD™potency

Poster presented at Eurotox, 2018

Sandberg P, Johansson A, Agemark M, Gradin R, Larne O, Appelgren H, Forreryd A, Jerre A, Edwards A, Hoepflinger V, Burleson F, Gehrke H, Roggen E, Johansson H
SenzaGen, Lund, Sweden, Burleson Research Technologies, Morrisville, US, Eurofins, Munich, Germany

Introduction
The prevalence of allergic contact dermatitis (ACD) is estimated to >20% in the western world. Not only the individual is affected, but downstream socioeconomic effects are high. To minimize exposure, chemicals must be safety tested. Traditional testing strategies like the murine local lymph node assay (LLNA) comprise animals, but the regulatory authorities, public opinion and economic interests require animal-free models. The Genomic Allergen Rapid Detection skin (GARD®skin) is an in vitro assay addressing this need. Here, we present the results of the GARD®skin ring trial (OECD TGP 4.106) for validity of the assay. In addition, we show data for GARD®potency – a complementary assay developed to categorize identified senitizers as CLP 1A or 1B.

 

Conclusions

Transfer study
Transferability: 100%

Validation study
Reproducibility
WLR: 82 – 89%BLR: 92% (92 – 100%)
Test performance
– Accuracy: 94%
– Sensitivity: 93%
– Specificity: 96%

A blinded ring trial was performed to assess the functionality of the GARDskin assay. The data demonstrates that GARDskin is a powerful tool for assessment of chemical skin sensitizers, with a predictive accuracy of 94% and excellent reproducibility between laboratories.
In addition, we show that GARDpotency accurately assesses potency of identified sensitizers.

Poster download

Predicting skin sensitizers with confidence – Using conformal prediction to determine applicability domain

Objective
GARD – Genomic Allergen Rapid Detection – is a state of the art non-animal based technology platform for classification of skin sensitizing chemicals. The assay has proven to be reliable and highly accurate for identification of skin sensitizing chemicals, and consistently reports predictive performances > 90% across external test sets. The aim of the current project is to complement assessments of average model performance with an estimate of uncertainty involved in each individual prediction, thus allowing for classification of skin sensitizers with confidence.

Results
An Internal validation procedure was initially performed on samples in the GARD training set (n=38) using the strategy described in Fig. 3A. Results from this exercise is summarized in Fig. 4A. Conformal prediction by definition allows the user to determine a reasonable and acceptable significance level to guarantee a maximum error rate in predictions. The significance level was set to 15%, i.e. the model was allowed to make a maximum of 15% errors. Performance of the conformal predictor was measured by validity and efficiency. A model was valid if the number of prediction errors did not exceed the significance level, while efficiency corresponded to the percentage of single class predictions. Internal validation of the training data resulted in a valid and highly effective model (92% single classifications, 1 empty, 2 both), indicating that the ambitious significance level was at a reasonable level for the GARD® assay. Following internal validation, samples in a large external test set (n =70) was classified within the CP framework as described in Fig. 3B, which resulted in generation of a valid and highly efficient model (99% single classifications, 0 empty, 1 both) (Fig.4B). Additional data on model performance is illustrated in Table 1.

Poster download

The use of GARDskin for sensitization evaluation of cosmetic ingredients and ‘real-life’ mixtures

Renato Ivan de Ávila, Tim Lindbergh, Malin Lindstedt and Marize Campos Valadares
Lab. of Education and Research in Pharmacology and Cellular Toxicology, Faculty of Pharmacy, Federal University of Goiás, Goiânia, Goiás, Brazil.
Department of Immunotechnology, Medicon Village, Lund University, Lund, Sweden.

 

Introduction
Genomic fingerprints in dendritic cells after chemical exposure is a recent strategy in in vitro techniques for skin sensitization hazard. Within this perspective, Genomic Allergen Rapid Detection (GARDskinTM), an assay based on a support vector machine (SVM) model, was developed for identifying contact allergens using a myeloid cell line as a surrogate for dendritic cells. Predictive system behind the GARDskin™ consists on the transcriptional quantitative analysis of 200 genes, referred as the GARDskin™ prediction signature. Mechanistically, GARDskin™ is linked to key event 3 “Activation of DCs”, as defined by the Adverse Outcome Pathways for skin sensitization published in 2012 by OECD (https://read.oecd-ilibrary.org/environment/the-adverse-outcome-pathway-for-skin-sensitisation-initiated-by-covalent-binding-to-proteins_9789264221444-en#page1)

 

Resluts
Information declared on the label and lawsone and PDD levels found in ten commercial henna-based hair coloring cosmetics are show in Table 1. Since all products analyzed were declared as henna cosmetics by the manufactures, the presence of LAW, the main active phytochemical of henna, was then expected in all samples. However, HPLC analysis showed no LAW level in the product nº 2, suggesting falsification. Furthermore, the presence of PPD was declared on the products nº 2 and 8 only by the manufactures. However, this substance was detected in all products, suggesting undisclosed adulteration.

Poster:
The use of GARDskin for sensitization evaluation of cosmetic ingredients and ‘real-life’ mixtures