T cell infiltration on local CpG-B delivery in early-stage melanoma is predominantly related to CLEC9A⁺CD141⁺cDC1 and CD14⁺antigen-presenting cell recruitment

Abstract

BackgroundWe previously reported CpG-B injection at the primary tumor excision site prior to re-excision and sentinel node biopsy to result in immune activation of the sentinel lymph node (SLN), increased melanoma-specific CD8+ T cell rates in peripheral blood, and prolonged recurrence-free survival. Here, we assessed recruitment and activation of antigen-presenting cell (APC) subsets in the SLN and at the injection site in relation to T cell infiltration.MethodsRe-excision skin specimens from patients with clinical stage I-II melanoma, collected 7 days after intradermal injection of either saline (n=10) or 8 mg CpG-B (CPG7909, n=12), were examined by immunohistochemistry, quantifying immune subsets in the epidermis, papillary, and reticular dermis. Counts were related to flow cytometric data from matched SLN samples. Additional in vitro cultures and transcriptional analyses on peripheral blood mononuclear cells (PBMCs) were performed to ascertain CpG-induced APC activation and chemokine profiles.ResultsSignificant increases in CD83+, CD14+, CD68+, and CD123+ APC were observed in the reticular dermis of CpG-B-injected skin samples. Fluorescent double/triple staining revealed recruitment of both CD123+BDCA2+ plasmacytoid dendritic cells (DCs) and BDCA3/CD141+CLEC9A+ type-1 conventional DC (cDC1), of which only the cDC1 showed considerable levels of CD83 expression. Simultaneous CpG-B-induced increases in T cell infiltration were strongly correlated with both cDC1 and CD14 counts. Moreover, cDC1 and CD14+ APC rates in the reticular dermis and matched SLN suspensions were positively correlated. Flow cytometric, transcriptional, and chemokine release analyses of PBMC, on in vitro or in vivo exposure to CpG-B, indicate a role for the activation and recruitment of both cDC1 and CD14+ monocyte-derived APCs in the release of CXCL10 and subsequent T cell infiltration.ConclusionThe CpG-B-induced concerted recruitment of cDC1 and CD14+ APC to the injection site and its draining lymph nodes may allow for both the (cross-)priming of T cells and their subsequent homing to effector sites.

Tumor-specific T cells support chemokine-driven spatial organization of intratumoral immune microaggregates needed for long survival

“…The DCs in these microaggregates were defined by their expression of CD11c, CD14, and HLA-DR but not CD68, and coexpressed CD1c, CD32b, CD36, and CD141. The presence of such inflammatory antigen presenting cells (APCs) has been linked to acute inflammatory processes, 44 45 to the survival of patients with HPV-induced cervical cancer, 46 and to immunotherapy responsiveness in HPV-induced premalignant lesions, 47 48 while the incapacity to attract these cells constituted a secondary escape mechanism to immunotherapy in a mouse model. 49 Our current findings, showing that these cells are found in higher numbers and organized in immune microaggregates when a tumor-specific T-cell response is present, sustain the notion that these cells are of major importance in tumor immunity.…”

Single-cell RNAseq and longitudinal proteomic analysis of a novel semi-spontaneous urothelial cancer model reveals tumor cell heterogeneity and pretumoral urine protein alterations

“…Therefore the administration route is key for success, as well as the presence of tumor antigens along with the adjuvant [ 86 ]. The use of these adjuvants as local immune-modulators in the neo-adjuvant setting in clinical trials is supported by publications [ 87 ]. Herein, we used peritumoral administration of CpG 1668 in vivo and observed a successful reduction of growth of 74/7 tumor graft in female hosts.…”

Longitudinal analysis of DC subsets in patients with ovarian cancer: Implications for immunotherapy

“…Recently, direct reprogramming from embryonic fibroblast has resulted in successful generation of human cDC1 (48) paving a new way for vaccination strategies. Of relevance, mechanisms of action and the clinical efficacy of multiple checkpoint inhibitors and adoptive cell therapy also depend on DC function and localization (8,14,15,(49)(50)(51)(52). Thus, our observations are not only important for the efficacy of vaccine strategies but also for other immunotherapies and even other treatments that likely rely on DC functionality.…”