STUDIES TO EVALUATE THE POTENTIAL FOR ENVIRONMENTAL&THERAPEUTIC AGENTS TO INDUCE IMMUNOTOXICITY - In vitro hypersensitivity

潜在致敏物的体外危险识别技术对国家毒理学规划越来越重要。在21财年，BRT又筛选了几种化学品，以完成机构合作伙伴提名的化学品数据集。国家毒理学规划与EPA、CSPC和其他联邦机构合作，编制了一份227种化学物质的清单，用于体外测试可能引起致敏和超敏反应的化学物质。这些化合物是根据体内数据的可用性来提名的，以探索几种体外方法的适用性，包括：1)DPRA -直接肽反应性测定法；2)角质蛋白-角质细胞活化；3) h-CLAT -人类细胞系激活试验。这些试验作为NTP体外测试电池的工具箱，用于评估化学物质引起致敏的可能性。美国环境保护署（EPA）在其最近发表的该类化学品风险评估中使用了异硫代唑啉酮类化学品体外超敏评估的数据。国家毒理学规划收到了这些体外研究的4份最终报告，这些报告已与机构间合作者分享。另有5份报告正在最后定稿过程中。在21财年，与一家商业供应商签订了一项研究合作协议，以评估GARDskin检测方法在预测混合物和化合物的皮肤致敏潜力方面的效用，而使用其他体外测试方法可能在技术上具有挑战性。这种测试方法使用基因表达谱来区分皮肤增敏剂和非增敏剂。使用该分析对来自机构合作伙伴研究的31种化学品进行了评估。这些研究的测试阶段和数据评价已经完成，正在起草一份报告。国家毒理学规划正在资助BRT参与亲电过敏原筛选试验（EASA）的验证试验。该试验在无细胞评估中使用非蛋白/肽探针来测量测试物质与生物学上重要分子“反应”的能力，以识别亲电性过敏性接触性皮炎的危害。研究方案于21财年制定，测试阶段将于22财年开始。

In vitro techniques for hazard identification for potential sensitizers have been of increasing importance to the NTP. In FY21, BRT screened several additional chemicals to complete the data set for chemicals nominated by agency partners. The NTP, in collaboration with the EPA, CSPC, and other federal agencies, had compiled a list of 227 chemicals for in vitro testing for the potential to cause sensitization and hypersensitivity. These compounds were nominated based on the availability of in vivo data to explore the applicability domain for several in vitro approaches including the: 1) DPRA – Direct Peptide Reactivity Assay; 2) Keratinosens – keratinocyte activation; and the 3) h-CLAT – Human cell line activation test. These assays serve as the toolbox for the NTP in vitro testing battery that is being used to evaluate the potential for chemicals to cause sensitization. Data from the in vitro hypersensitivity assessment for the isothiozolinone chemicals were used by the EPA in their recently published risk assessment for this chemical class. The NTP has received 4 final reports from these in vitro studies which have been shared with interagency collaborators. An additional 5 reports are in the process of being finalized. A research collaboration agreement with a commercial vendor was established in FY21 to assess the utility of the GARDskin assay to predict the skin sensitization potential of mixtures and compounds which may be technically challenging to evaluate using other in vitro test methods. This test method uses gene expression profiling to discriminate skin sensitizers from non-sensitizers. A total of 31 chemicals from the agency partners studies were evaluated using the assay. The testing phase and data evaluation for these studies is complete and a report is being drafted. NTP is funding BRT participation in validation trials for the Electrophilic Allergen Screening Assay (EASA). This assay uses non-protein/peptide probes in a cell-free assessment to measure the ability of a test substance to “react” with biologically important molecules for the identification of electrophilic allergic contact dermatitis hazards. Study protocols were established in FY21, and the testing phase will begin in FY22.