Fusion of the Human Cytomegalovirus pp65 antigen with both ubiquitin and ornithine decarboxylase additively enhances antigen presentation to CD8(+) T cells in human dendritic cells

Cisplatin resistance driver claspin is a target for immunotherapy in urothelial carcinoma

Bladder cancer is a major and fatal urological disease. Cisplatin is a key drug for the treatment of bladder cancer, especially in muscle-invasive cases. In most cases of bladder cancer, cisplatin is effective; however, resistance to cisplatin has a significant negative impact on prognosis. Thus, a treatment strategy for cisplatin-resistant bladder cancer is essential to improve the prognosis. In this study, we established a cisplatin-resistant (CR) bladder cancer cell line using an urothelial carcinoma cell lines (UM-UC-3 and J82). We screened for potential targets in CR cells and found that claspin (CLSPN) was overexpressed. CLSPN mRNA knockdown revealed that CLSPN had a role in cisplatin resistance in CR cells. In our previous study, we identified human leukocyte antigen (HLA)-A*02:01-restricted CLSPN peptide by HLA ligandome analysis. Thus, we generated a CLSPN peptide-specific cytotoxic T lymphocyte clone that recognized CR cells at a higher level than wild-type UM-UC-3 cells. These findings indicate that CLSPN is a driver of cisplatin resistance and CLSPN peptide-specific immunotherapy may be effective for cisplatin-resistant cases.

Identification of Naturally Processed Epitope Region Using Artificial APC Expressing a Single HLA Class I Allotype and mRNA of HCMV pp65 Antigen Fragments

Recently, long synthetic peptides or in silico-predicted epitope peptides have been used to identify T cell epitopes, but these approaches may not be suitable for investigating naturally processed epitopes. Here, mRNAs, including fragments or predicted epitope sequences of HCMV pp65 antigen, were generated by in vitro transcription following transcriptionally active PCR. Then, artificial antigen-presenting cells (aAPCs) expressing a single HLA allotype were transfected with mRNAs to identify epitopes in donors with T cell responses that recognize pp65 antigen restricted to HLA-A*02:01, -A*02:06, or -B*07:02. T cells restricted to a particular HLA allotype showed positive responses in some of the 10 fragment antigens. Among predicted epitopes within these positive fragments, three epitopes of HLA-A*02:01, -A*02:06, and -B*07:02 were confirmed. In addition, T cells expanded by anti-CD3 stimulation for two weeks could also be effectively used for the identification of these T cell epitopes, although there were individual differences. These results demonstrated that fragment antigens and epitopes can be rapidly generated using mRNA, and naturally processed antigenic regions can be detected using aAPCs without a T cell cloning procedure. This method will help to identify novel T cell epitopes for developing immunotherapy and vaccines against infectious diseases and cancer.

GM-CSF Promotes the Expansion and Differentiation of Cord Blood Myeloid-Derived Suppressor Cells, Which Attenuate Xenogeneic Graft-vs.-Host Disease

Myeloid-derived suppressor cells (MDSCs) are increased in tumor patients. Studies have shown generation of MDSCs from human peripheral blood mononuclear cells (PBMCs) by various cytokine combinations. However, large scale expansion of human MDSCs has not been demonstrated or applied in clinic settings. We investigated which cytokine combinations among GM-CSF/SCF, G-CSF/SCF, or M-CSF/SCF efficiently expand and differentiate human MDSCs following culture CD34⁺ cells of umbilical cord blood (CB). GM-CSF/SCF showed the greatest expansion of MDSCs. Up to 10⁸ MDSCs (HLA-DR^lowCD11b⁺CD33⁺) could be produced from 1 unit of CB following 6 weeks of continuous culture. MDSCs produced from culture of CD34⁺ cells with GM-CSF/SCF for 6 weeks had the greatest suppressive function of T cell proliferation and had the highest expression of immunosuppressive molecules including iNOS, arginase 1 and IDO compared to those differentiated with G-CSF/SCF or M-CSF/SCF. MDSCs secreted IL-10, TGB-β, and VEGF. The infusion of expanded MDSCs significantly prolonged the survival and decreased the GVHD score in a NSG xenogeneic model of GVHD. Injected MDSCs increased IL-10 and TGF-β but decreased the level of TNF-α and IL-6 in the serum of treated mice. Notably, FoxP3 expressing regulatory T (Treg) cells were increased while IFN-γ (Th1) and IL-17 (Th17) producing T cells were decreased in the spleen of MDSC treated mice compared to untreated GVHD mice. Our results demonstrate that human MDSCs are generated from CB CD34⁺ cells using GM-CSF/SCF. These MDSCs exhibited potent immunosuppressive function, suggesting that they are useable as a treatment for inflammatory diseases such as GVHD.

Simultaneous in vitro generation of CD8 and CD4 T cells specific to three universal tumor associated antigens of WT1, survivin and TERT and adoptive T cell transfer for the treatment of acute myeloid leukemia

Previously, we found that most patients with acute myeloid leukemia (AML) expressed at least one of the leukemic associated antigens (LAAs) WT1, survivin and TERT, and different combinations of the three LAAs predicted negative clinical outcomes. Multi-tumor antigen-specific T cells were generated to overcome antigenic variation and may be sufficient to maximize antitumoral effects. To generate triple antigen-specific (Tri)-T cells that recognize three LAAs, dendritic cells (DCs) were transfected with three tumor antigen-encoding RNAs. These DCs were used to stimulate both CD8 and CD4 T cells and to overcome the limitation of known human leukocyte antigen-restricted epitopes. The sum of the antigen-specific T cell frequencies was higher in the Tri-T cells than in the T cells that recognized a single antigen. Furthermore, the Tri-T cells were more effective against leukemic blasts that expressed all three LAAs compared with blasts that expressed one or two LAAs, suggesting a proportional correlation between IFN-γ secretion and LAA expression. Engrafted leukemic blasts in the bone marrow of mice significantly decreased in the presence of Tri-T cells. This technique represents an effective immunotherapeutic strategy in AML.

A synthetic human cytomegalovirus pp65-IE1 fusion antigen efficiently induces and expands virus specific T cells

Infection with human cytomegalovirus (HCMV) can cause severe complications in newborns and immunocompromised patients, and a prophylactic or therapeutic vaccine against HCMV is not available. Here, we generated a HCMV vaccine candidate fulfilling the regulatory requirements for GMP-compliant production and clinical testing. A novel synthetic fusion gene consisting of the coding sequences of HCMV pp65 and IE1 having a deleted nuclear localization sequence and STAT2 binding domain was introduced into the genome of the attenuated vaccinia virus strain MVA. This recombinant MVA, MVA-syn65_IE1, allowed for the production of a stable ∼120kDa syn65_IE1 fusion protein upon tissue culture infection. MVA-syn65_IE1 infected CD40-activated B cells activated and expanded pp65- and IE1-specific T cells derived from HCMV-seropositive donors to at least equal levels as control recombinant MVA expressing single genes for pp65 or IE1. Additionally, we show that MVA-syn65_IE1 induced HCMV pp65- and IE1-epitope specific T cells in HLA-A2.1-/HLA-DR1-transgenic H-2 class I-/class II-knockout mice. Thus, MVA-syn65_IE1 represents a promising vaccine candidate against HCMV and constitutes a basis for the generation of a multivalent vaccine targeting relevant pathogens in immunocompromised patients.

Expression, Polyubiquitination, and Therapeutic Potential of Recombinant E6E7 from HPV16 Antigens Fused to Ubiquitin

Ubiquitin-proteasome system plays an essential role in the immune response due to its involvement in the antigen generation and presentation to CD8⁺ T cells. Hereby, ubiquitin fused to antigens has been explored as an immunotherapeutic strategy that requires the activation of cytotoxic T lymphocytes. Here we propose to apply this ubiquitin fusion approach to a recombinant vaccine against human papillomavirus 16-infected cells. E6E7 multi-epitope antigen was fused genetically at its N- or C-terminal end to ubiquitin and expressed in Escherichia coli as inclusion bodies. The antigens were solubilized using urea and purified by nickel affinity chromatography in denatured condition. Fusion of ubiquitin to E6E7 resulted in marked polyubiquitination in vitro mainly when fused to the E6E7 N-terminal. When tested in a therapeutic scenario, the fusion of ubiquitin to E6E7 reinforced the anti-tumor protection and increased the E6/E7-specific cellular immune responses. Present results encourage the investigation of the adjuvant potential of the ubiquitin fusion to recombinant vaccines requiring CD8⁺ T cells.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

Engineering dendritic cells to enhance cancer immunotherapy

Cancer immunotherapy aims to establish immune-mediated control of tumor growth by priming T-cell responses to target tumor-associated antigens. Three signals are required for T-cell activation: (i) presentation of cognate antigen in self MHC molecules; (ii) costimulation by membrane-bound receptor-ligand pairs; and (iii) soluble factors to direct polarization of the ensuing immune response. The ability of dendritic cells (DCs) to provide all three signals required for T-cell activation makes them an ideal cancer vaccine platform. Several strategies have been developed to enhance and control antigen presentation, costimulation, and cytokine production. In this review, we discuss progress toward developing DC-based cancer vaccines by genetic modification using RNA, DNA, and recombinant viruses. Furthermore, the ability of DC-based vaccines to activate natural killer (NK) and B-cells, and the impact of gene modification strategies on these populations is described. Clinical trials using gene-modified DCs have shown modest results, therefore, further considerations for DC manipulation to enhance their clinical efficacy are also discussed.