Single-cell genomics segregate different transcriptomic impacts of anti-IL-17A blockade on type 17 T-cells and regulatory immune cells in psoriasis skin

Durable psoriasis improvement has been reported in a subset of psoriasis patients after treatment withdrawal of biologics blocking IL-23/Type 17 T-cell (T17) autoimmune axis. However, it is not well understood if systemic blockade of the IL-23/T17 axis promotes immune tolerance in psoriasis skin. The purpose of the study was to find translational evidence that systemic IL-17A blockade promotes regulatory transcriptome modification in human psoriasis skin immune cell subsets. We analyzed human psoriasis lesional skin 6 mm punch biopsy tissues before and after systemic IL-17A blockade using the muti-genomics approach integrating immune cell-enriched scRNA-seq (n = 18), microarray (n = 61), and immunohistochemistry (n = 61) with repository normal control skin immune cell-enriched scRNA-seq (n = 10) and microarray (n = 8) data. For the T17 axis transcriptome, systemic IL-17A blockade depleted 100% of IL17A + T-cells and 95% of IL17F + T-cells in psoriasis skin. The expression of IL23A in DC subsets was also downregulated by IL-17A blockade. The expression of IL-17-driven inflammatory mediators (IL36G, S100A8, DEFB4A, and DEFB4B) in suprabasal keratinocytes was correlated with psoriasis severity and was downregulated by IL-17A blockade. For the regulatory DC transcriptome, the proportion of regulatory semimature DCs expressing regulatory DC markers of BDCA-3 (THBD) and DCIR (CLEC4A) was increased in posttreatment psoriasis lesional skin compared to pretreatment psoriasis lesional skin. In addition, IL-17A blockade induced higher expression of CD1C and CD14, which are markers of CD1c+ CD14+ dendritic cell (DC) subset that suppresses antigen-specific T-cell responses, in posttreatment regulatory semimature DCs compared to pretreatment regulatory semimature DCs. In conclusion, systemic IL-17A inhibition not only blocks the entire IL-23/T17 cell axis but also promotes regulatory gene expression in regulatory DCs in human psoriasis skin. 23 adult psoriasis patients received anti-IL-17A monoclonal antibody (secukinumab) injections for more than 12 weeks in the phase II clinical trial (ClinicalTrial.gov identifier: NCT03131570). Patients received the anti-IL-17A monoclonal antibody at a dose of 300 mg with injections administered once weekly at baseline and at weeks 1, 2, 3, and 4 and then every 4 weeks. For this study, psoriasis skin biopsy samples obtained from the clinical trial were further analyzed by immune cell-enriched scRNA-seq (n = 18; GSE183047), microarray (n = 61; GSE226244), and immunohistochemistry (n = 61) together with our repository normal control skin immune cell-enriched scRNA-seq data (n = 10) (16) and microarray data (n = 8). To minimize the batch effects, all the molecular experiments from the initial sample processing to cDNA library construction were performed by the same investigators under the same protocol. Lesional biopsy specimens were harvested with a 6 mm punch biopsy from areas with representative psoriasis lesions. Psoriasis lesional skin biopsy samples before anti-IL-17A monoclonal antibody injections (pretreatment) and psoriasis lesional skin biopsy samples after 12 weeks of anti-IL-17 monoclonal antibody injections (posttreatment) were compared for this study. Harvested skin samples were bisected immediately after the skin biopsy. Half of the two bisected skin tissue was incubated in a culture medium for single-cell RNA sequencing (scRNA-seq) experiments. Another half of the bisected skin tissue was snap-frozen and embedded in the Optimal Cutting Temperature (OCT) compound (Ted Pella, Redding, CA) for microarray and immunohistochemistry experiments.