Over the past 20 years or more, investigators have been developing non-animal test methods for use in assessing the skin sensitisation potential of chemicals. In parallel with this effort, the key biological events of skin sensitisation have been well-characterised in an Adverse Outcome Pathway (AOP) proposed by the Organisation for Economic Co-operation and Development (OECD). The key molecular initiating event of this AOP is haptenation or covalent modification of epidermal proteins. In this review, the strengths and limitations of the Direct Peptide Reactivity Assay (DPRA) are described, and the more recently developed Peroxidase Peptide Reactivity Assay (PPRA). The DPRA has been formally validated and incorporated into an OECD Test Guideline (TG442C). The DPRA shows promise for assisting in hazard identification as well as for assessing skin sensitisation potency when used in an integrated testing strategy.
BasketterD.A., EvansP., FielderR.J., GerberickG.F., DearmanR.J., & KimberI. (2002). Local lymph node assay — Validation and use in practice. Food & Chemical Toxicology40, 593–598.
2.
DearmanR.J., BasketterD.A., & KimberI. (1999). Local lymph node assay — Use in hazard and risk assessment. Journal of Applied Toxicology19, 299–306.
3.
GerberickG.F., RyanC.A., KimberI., DearmanR.J., LeaL.J., & BasketterD.A. (2000). Local lymph node assay: Validation assessment for regulatory purposes. American Journal of Contact Dermatitis11, 3–18.
4.
KimberI., DearmanR.J., ScholesE.W., & BasketterD.A. (1994). The local lymph node assay: Development and applications. Toxicology93, 13–31.
5.
KimberI., DearmanR.J., BasketterD.A., RyanC.A., & GerberickG.F. (2002). The local lymph node assay: Past, present and future. Contact Dermatitis47, 315–328.
LandsteinerK., & JacobsJ. (1936). Studies on the sensitization of animals with simple chemical compounds. Journal of Experimental Medicine64, 625–639.
8.
DupuisG., & BenezraC. (eds) (1982). Allergic Con tact Dermatitis to Simple Chemicals: A Molecular Approach, 183 pp. New York, NY, USA: Marcel Dekker Inc.
9.
LepoittevinJ-P., BasketterD.A., GoossensA., & KarlbergA-T. (eds) (1998). Allergic Contact Dermatitis: The Molecular Basis, 186 pp. Berlin, Germany: Springer.
10.
GerberickF., AleksicM., BasketterD., CasatiS., KarlbergA-T., KernP., KimberI., LepoittevinJ.P., NatschA., OvigneJ.M., RovidaC., SakaguchiH., & SchultzT. (2008). Chemical reactivity measurement and the predictive identification of skin sensitisers: The report and recommendations of ECVAM Workshop 64. ATLA36, 215–242.
11.
RyanC.A., HuletteB.C., & GerberickG.F. (2001). Review: Approaches for the development of cell based in vitro methods for contact sensitization. Toxicology in Vitro15, 43–55.
12.
AhlforsS.R., SternerO., & HanssonC. (2003). Reactivity of contact allergenic haptens to amino acid residues in a model carrier peptide, and characterization of formed peptide–hapten adducts. Skin Pharmacology & Applied Skin Physiology16, 59–68.
13.
Alvarez-SanchezR., BasketterD.A., PeaseC., & LepoittevinJ-P. (2003). Studies of chemical selectivity of hapten, reactivity, and skin sensitization potency. 3. Synthesis and studies on the reactivity toward model nucleophiles of the 13C-labeled skin sensitizers, 5-chloro-2-methylisothia-zol-3-one (MCI) and 2-methylisothiazol-3-one (MI). Chemical Research in Toxicology16, 627–637.
14.
MeschkatE., BarrattM.D., & LepoittevinJ-P. (2001). Studies of the chemical selectivity of hapten, reactivity, and skin sensitization potency. 1. Synthesis and studies on the reactivity toward model nucleophiles of the (13)C-labeled skin sensitizers hex-1-ene- and hexane-1,3-sultones. Chemical Research in Toxicology14, 110–117.
15.
AleksicM., ThainE., RogerD., SaibO., DaviesM., LiJ., AptulaA., & ZazzeroniR. (2009). Reactivity profiling: Covalent modification of single nucleophile peptides for skin sensitization risk assessment. Toxicological Sciences108, 401–411.
16.
Alvarez-SanchezR., BasketterD.A., PeaseC., & LepoittevinJ-P. (2004). Covalent binding of the 13C-labeled sensitizers 5-chloro-2-methylisothia-zol-3-one (MCI) and 2-methylisothiazol-3-one (MI) to a model peptide and glutathione. Bioorganic & Medicinal Chemistry Letters14, 365–368.
17.
Alvarez-SanchezR., DivkovicM., BasketterD.A., PeaseC., PanicoM., DellA., MorrisH., & LepoittevinJ-P. (2004). Effect of glutathione on the covalent binding of the 13C-labeled skin sensitizer 5-chloro-2-methylisothiazol-3-one (MCI) to human serum albumin: Identification of adducts by NMR, MALDI-MS and nano-ES MS/MS. Chemical Research in Toxicology17, 1280–1288.
18.
AptulaA.O., PatlewiczG., RobertsD.W., & SchultzT.W. (2006). Non-enzymatic glutathione reactivity and in vitro toxicity: A non-animal approach to skin sensitization. Toxicology in Vitro20, 239–247.
19.
ChipindaI., AjibolaR.O., MorakinyoM.K., RuwonaT.B., SimoyiR.H., & SiegelP.D. (2010). Rapid and simple kinetic screening assay for electrophilic dermal sensitizers using nitrobenzen ethiol. Chemical Research in Toxicology23, 918–925.
20.
EnochS.J., RobertsD.W., & CroninM.T.D. (2009). Electrophilic reaction chemistry of low molecular weight respiratory sensitizers. Chemical Research in Toxicology22, 1447–1453.
21.
GerberickG.F., VassalloJ.D., BaileyR.E., ChaneyJ.G., MorrallS.W., & LepoittevinJ-P. (2004). Development of a peptide reactivity assay for screening contact allergens. Toxicological Sciences81, 332–343.
22.
GerberickG.F., VassalloJ.D., FoertschL.M., PriceB.B., ChaneyJ.G., & LepoittevinJ-P. (2007). Quantification of chemical peptide reactivity for screening contact allergens: A classification tree model approach. Toxicological Sciences97, 417–427.
23.
GerberickG.F., TroutmanJ.A., FoertschL.M., VassalloJ.D., QuijanoM., DobsonR.L., GoebelC., & LepoittevinJ-P. (2009). Investigation of peptide reactivity of pro-hapten skin sensitizers using a peroxidase-peroxide oxidation system. Toxicological Sciences112, 164–174.
24.
KatoH., OkamotoM., YamashitaK., NakamuraY., FukumoriY., NakaiK., & KanekoH. (2003). Peptide-binding assessment using mass spectrometry as a new screening method for skin sensitization. Journal of Toxicological Sciences28, 19–24.
25.
NatschA., GfellerH., RothauptM., & EllisG. (2007). Utility and limitations of a peptide reactivity assay to predict fragrance allergens in vitro.Toxicology in Vitro, 21, 1220–1226.
26.
NatschA., & GfellerH. (2008). LC-MS-based characterization of peptide reactivity of chemicals to improve the in vitro prediction of skin sensitization potential. Toxicological Sciences106, 464–478.
27.
SchultzT.W., YarbroughJ.W., & JohnsonE.L. (2005). Structure–activity relationships for reactivity of carbonyl-containing compounds with glutathione. SAR & QSAR in Environmental Research16, 313–322.
28.
WongC.L., LamA.L., SmithM.T., & GhassabianS. (2016). Evaluation of a high-throughput peptide reactivity format assay for assessment of the skin sensitization potential of chemical. Frontiers in Pharmacology, 7, 53 [doi: 10.3389/fphar.2016.00053].
29.
TroutmanJ.A., FoertschL.M., KernP.S., DaiH.J., QuijanoM., DobsonR.L., LalkoJ.F., LepoittevinJ-P., & GerberickG.F. (2011). The incorporation of lysine into the peroxidase peptide reactivity assay for skin sensitization assessments. Toxicological Sciences122, 422–436.
30.
EURL ECVAM (2012). Direct Peptide Reactivity Assay (DPRA) Validation Study Report, 74 pp. Ispra, Italy: European Commission Joint Research Centre, Institute for Health & Consumer Protection, European Union Reference Laboratory for Alternative Methods to Animal Testing (EURLECVAM). Available at: https://eurl-ecvam.jrc.ec.europa.eu/eurl-ecvam-recommendations (Accessed 18.09.16).
31.
NatschA., RyanC.A., FoertschL., EmterR., JaworskaJ., GerberickF., & KernP. (2007). A dataset on 145 chemicals tested in alternative assays for skin sensitization undergoing prevalidation. Journal of Applied Toxicology33, 1337–1352.
32.
HartungT., BremerS., CasatiS., CoeckeS., CorviR., FortanerS., GribaldoL., HalderM., HoffmanS., RoiA.J., PrietoP., SabbioniE., ScottL., WorthA., & ZuangV. (2004). A modular approach to the ECVAM principles on test validity. ATLA32, 467–472.
33.
EURL ECVAM (2013). EURL ECVAM Recommendation on the Direct Peptide Reactivity Assay (DPRA) for Skin Sensitisation Testing, 38 pp. Ispra, Italy: Euro pean Commission Joint Research Centre, Institute for Health & Consumer Protection, European Union Reference Laboratory for Alternative Methods to Animal Testing (EURL ECVAM). Available at: https://eurl-ecvam.jrc.ec.europa.eu/eurl-ecvam-recommendations (Accessed 18.09.16).
AdlerS., BasketterD., CretonS., PelkonenO., van BenthemJ., ZuangV., AndersenK.E., Angers-LoustauA., AptulaA., & Bal-PriceA. (2011). Alternative (non-animal) methods for cosmetics testing: Current status and future prospects — 2010. Archives of Toxicology85, 367–485.
36.
JaworskaJ., HarolA., KernP.S., & GerberickG.F. (2011). Integrating non-animal test information into an adaptive testing strategy — Skin sensitization proof of concept case. ALTEX28, 211–225.
37.
JaworskaJ., DancikY., KernP., GerberickF., & NatschA. (2013). Bayesian integrated testing strategy to assess skin sensitization potency: From theory to practice. Journal of Applied Toxicology33, 1353–1364.
38.
RobertsD.W., & AptulaA.O. (2008). Determinants of skin sensitisation potential. Journal of Applied Toxicology28, 377–387.
39.
BauchC., KolleS.N., RamirezT., EltzeT., FabianE., MehlingA., TeubnerW., van RavenzwaayB., & LandsiedelR. (2012). Putting the parts together: Combining in vitro methods to test for skin sensitizing potentials. Regulatory Toxicology & Pharmacology63, 489–504.
40.
United Nations (2011). Globally Harmonized System of Classification & Labelling of Chemicals, Fourth revised edition, ST/SG/AC.10/30Rev.4, 568 pp. Geneva, Switzerland: United Nations.
41.
van der VeenJ.W., RorijeE., EmterR., NatschA., van LoverenH., & EzendamJ. (2014). Evaluating the performance of integrated approaches for hazard identification of skin sensitizing chemicals. Regulatory Toxicology & Pharmacology69, 371–379.
42.
StricklandJ., ZangQ., ParisM., LehmannD.M., AllenD., ChoksiN., JacobsA., CaseyW., & KleinstreuerN. (2016). Multivariate models for prediction of human skin sensitization hazard. Journal of Applied Toxicology, 2 August 2016, doi: 10.1002/jat.3366.
43.
JaworskaJ., NatschA., RyanC., StricklandJ., AshikagaT., & MiyazawaM. (2013). Bayesian integrated testing strategy (ITS) for skin sensitization potency assessment: A decision support system for quantitative weight of evidence and adaptive testing strategy. Archives of Toxicology89, 2355–2383.
44.
NukadaY., MiyazawaM., KazutoshiS., SakaguchiH., & NishiyamaN. (2013). Data integration of non-animal tests for the development of a test battery to predict the skin sensitizing potential and potency of chemicals. Toxicology in Vitro27, 609–618.
45.
Tsujita-InoueK., HirotaM., AshikagaT., AtobeT., KouzukiH., & AibaS. (2014). Skin sensitization risk assessment model using artificial neural network analysis of data from multiple in vitro assays. Toxicology in Vitro28, 626–639.
