Soluble CD83 Inhibits T Cell Activation by Binding to the TLR4/MD-2 Complex on CD14+ Monocytes.

The transmembrane protein CD83, expressed on APCs, B cells, and T cells, can be expressed as a soluble form generated by alternative splice variants and/or by shedding. Soluble CD83 (sCD83) was shown to be involved in negatively regulating the immune response. sCD83 inhibits T cell proliferation in vitro, supports allograft survival in vivo, prevents corneal transplant rejection, and attenuates the progression and severity of autoimmune diseases and experimental colitis. Although sCD83 binds to human PBMCs, the specific molecules that bind sCD83 have not been identified. In this article, we identify myeloid differentiation factor-2 (MD-2), the coreceptor within the TLR4/MD-2 receptor complex, as the high-affinity sCD83 binding partner. TLR4/MD-2 mediates proinflammatory signal delivery following recognition of bacterial LPSs. However, altering TLR4 signaling can attenuate the proinflammatory cascade, leading to LPS tolerance. Our data show that binding of sCD83 to MD-2 alters this signaling cascade by rapidly degrading IL-1R-associated kinase-1, leading to induction of the anti-inflammatory mediators IDO, IL-10, and PGE2 in a COX-2-dependent manner. sCD83 inhibited T cell proliferation, blocked IL-2 secretion, and rendered T cells unresponsive to further downstream differentiation signals mediated by IL-2. Therefore, we propose the tolerogenic mechanism of action of sCD83 to be dependent on initial interaction with APCs, altering early cytokine signal pathways and leading to T cell unresponsiveness.

A review of the clinical experience with CMN-001, a tumor RNA loaded dendritic cell immunotherapy for the treatment of metastatic renal cell carcinoma.

Engineering dendritic cells (DCs) to treat cancer is a long sought-after goal for cell-based immunotherapies. In this review, we focus on the experience with CMN-001, formally AGS-003, a DC-based immunotherapy, employing autologous DC electroporated with autologous tumor RNA to treat subjects with metastatic renal cell carcinoma (mRCC). We will review the early clinical development of CMN-001 up to and including deployment in a multicenter phase 3 study and provide a rationale to continue the development of CMN-001 in an ongoing randomized phase 2 study. The synergy between CMN-001 and everolimus observed in the phase 3 study provides an opportunity to design a phase 2b study building on the mechanism of action of CMN-001 and underlying immune and clinical outcomes revealed in the earlier studies. The design of the phase 2b study combines CMN-001 with first-line checkpoint inhibition therapy and second line lenvatinib/everolimus in poor-risk mRCC subjects.

Results of the ADAPT Phase 3 Study of Rocapuldencel-T in Combination with Sunitinib as First-Line Therapy in Patients with Metastatic Renal Cell Carcinoma.

PURPOSE: Rocapuldencel-T is an autologous immunotherapy prepared from mature monocyte-derived dendritic cells (DC), coelectroporated with amplified tumor RNA plus CD40L RNA. This pivotal phase III trial was initiated to investigate the safety and efficacy of a combination therapy dosing regimen of Rocapuldencel-T plus sunitinib in patients with metastatic renal cell carcinoma (mRCC). PATIENTS AND METHODS: Patients received either Rocapuldencel-T plus standard of care (SOC) or SOC treatment alone. The primary objective compared overall survival (OS) between groups. Secondary objectives included safety assessments, progression-free survival (PFS), and tumor responses based on RECIST 1.1 criteria. Exploratory analyses included immunologic assessments and correlates with OS. RESULTS: Between 2013 and 2016, 462 patients were randomized 2:1, 307 to the combination group and 155 to the SOC group. Median OS in the combination group was 27.7 months [95% confidence interval (CI) 23.0-35.9] and 32.4 months (95% CI, 22.5-) in the SOC group HR of 1.10 (95% CI, 0.83-1.40). PFS was 6.0 months and 7.83 months for the combination and SOC groups, respectively [HR = 1.15 (95% CI, 0.92-1.44)]. The ORR was 42.7% (95% CI, 37.1-48.4) for the combination group and 39.4% (95% CI, 31.6-47.5) for the SOC group. Median follow up was 29 months (0.4-47.7 months). On the basis of the lack of clinical efficacy, the ADAPT trial was terminated on February 17, 2017. Immune responses were detected in 70% of patients treated with Rocapuldencel-T, and the magnitude of the immune response positively correlated with OS. In addition, we report the survival-predictive value of measuring IL-12 produced by the DC vaccine and the observation that high baseline numbers of T regulatory cells are associated with improved outcomes in DC-treated patients, but are associated with poor outcomes in patients receiving SOC treatment. No serious adverse events attributed to the study medication have been reported to date. CONCLUSIONS: Rocapuldencel-T did not improve OS in patients treated with combination therapy, although the induced immune response correlated with OS. Moreover, we identified two potential survival-predictive biomarkers for patients receiving DC based immunotherapy, IL-12 produced by the DC vaccine and higher numbers of T regulatory cells present in the peripheral blood of patients with advanced RCC.

An improved RNA amplification procedure results in increased yield of autologous RNA transfected dendritic cell-based vaccine.

Use of antigen encoding RNA transfected Dendritic cells in the field of cancer immunotherapy has been well established. The use of RNA overcomes limitations inherent to other autologous DC-based vaccines as it does not require specific HLA haplotypes, identification and characterization of antigens, and captures the broadest antigen repertoire. RNA offers yet another advantage-it could be amplified minimizing the requirement of tumor mass for autologous vaccine production, and will afford the opportunity to treat patients with minimal tumor burden. The original procedure described for RNA amplification resulted in a proportion of RNA transcribed in the antisense orientation. This study also demonstrates that the presence of double-stranded RNA correlates with the presence of antisense RNA. Alternative design of oligonucleotides that removes sequence redundancy eliminates the formation of both antisense and double-stranded RNA species. We provide further evidence that amplified RNA containing antisense and double-stranded RNA species results in lower recovery of DCs post-transfection and maturation, presumably through sequence-specific gene silencing. The removal of the double-stranded species from amplified RNA results in higher recovery of mature autologous amplified RNA transfected dendritic cells. Higher DC yield will allow for reduction of cost of vaccine manufacturing and prolonged treatment of a patient.