The HaCaT/THP-1 cocultured activation test (COCAT) for skin sensitization: A study of intra-laboratory reproducibility and predictivity

Abstract

The Cocultured Activation Test (COCAT) consists of cocultured HaCaT (human keratinocyte cell line) and THP-1 cells (surrogate of antigen presenting cells). Individually, these cell lines are used to address key events 2 and 3 of the skin sensitization adverse outcome pathway (AOP). Their exposure in coculture was found to have the potential to increase their response to sensitizing chemicals, enable the detection of pro-haptens, and support the identification of skin sensi­tization potency. The present study was undertaken to assess the predictive capacity of COCAT of both skin sensitization hazard and potency and to assess the intra-laboratory reproducibility of COCAT based on the blind testing of chem­icals. Results showed a reproducibility between runs of 80% for 15 coded chemicals. Skin sensitization hazard prediction had 100% sensitivity (9/9), 75% specificity (3/4), and 92.3% accuracy (12/13), while the tests of two chemicals were inconclusive. Including additional chemicals tested during the optimization phase in addition to the blind tested chemicals, the skin sensitization UN GHS sub-categories were correctly predicted for 85.7% (12/14) sub-category 1A chemicals, 83.3% (10/12) sub-category 1B chemicals, and 92.3% (12/13) no category chemicals, resulting in an overall accuracy of 87.4% (34/39). The present study shows the COCAT to be a promising method for the identification of skin sensiti­zation hazard and potency sub-categorization according to the UN GHS classification.