Identification of HLA-A2 restricted T-cell epitopes within the conserved region of the immunoglobulin G heavy-chain in patients with multiple myeloma

Objective: The aim of this study is the identification of HLA‐A2 restricted T‐cell epitopes in the conserved region of the immunoglobulin‐G‐heavy‐chain (IgG_H) that can be used for immunotherapy in multiple myeloma (MM) patients. Methods: After the IgG_H gene sequence was scanned for HLA‐A2 restricted T‐cell epitopes with a high binding affinity to the MHC‐I‐complex, promising nona‐peptides were synthesized. Peptide specific CD8 ⁺ T‐cells were generated from peripheral blood mononuclear cells (PBMC) of healthy donors (HD) and patients with MM using peptide pulsed dendritic cells (DC) in vitro. The activation and cytotoxicity of CD8 ⁺ T‐cells was analyzed by IFN‐α ELISpot‐assay and ⁵¹Chromium release‐assay. HLA‐A2 restriction was proven by blocking T‐cell activation with anti‐HLA‐A2 antibodies. Results: Two HLA‐A2 restricted T‐cell epitopes–TLVTVSSAS derived from the IgG_H‐framework‐region 4 (FR4) and LMISRTPEV from the constant region (CR)‐induced expansion of specific CD8 ⁺ T‐cells from PBMC in two of three (TLVTVSSAS) and one of three (LMISRTPEV) HD respectively. Specific T‐cells were induced from PBMC in two of six (TLVTVSSAS) and eight of 19 (LMISRTPEV) patients with MM. Specific CD8 ⁺ T‐cells also lysed peptide‐pulsed target cells in ⁵¹Chromium release‐assay. LMISRTPEV specific CD8 ⁺ T‐cells from MM patients lysed specifically the HLA‐A2 ⁺ IgG myeloma cell line XG‐6. Conclusion: We identified two HLA‐A2 restricted T‐cell epitopes–TLVTVSSAS and LMISRTPEV–which can yield an expansion of CD8 ⁺ T‐cells with the ability to kill peptide‐loaded target cells and HLA‐A2 ⁺ IgG⁺ myeloma cells. We conclude that TLVTVSSAS and LMISRTPEV could be T‐cell epitopes for immunotherapy in MM patients.     

Identification of an HLA-A*0201-restricted CD8+ T-cell epitope SSp-1 of SARS-CoV spike protein

A novel coronavirus, severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV), has been identified as the causal agent of SARS. Spike (S) protein is a major structural glycoprotein of the SARS virus and a potential target for SARS-specific cell-mediated immune responses. A panel of S protein-derived peptides was tested for their binding affinity to HLA-A*0201 molecules. Peptides with high affinity for HLA-A*0201 were then assessed for their capacity to elicit specific immune responses mediated by cytotoxic T lymphocytes (CTLs) both in vivo, in HLA-A2.1/K(b) transgenic mice, and in vitro, from peripheral blood lymphocytes (PBLs) harvested from healthy HLA-A2.1(+) donors. SARS-CoV protein-derived peptide-1 (SSp-1 RLNEVAKNL), induced peptide-specific CTLs both in vivo (transgenic mice) and in vitro (human PBLs), which specifically released interferon-gamma (IFN-gamma) upon stimulation with SSp-1-pulsed autologous dendritic cells (DCs) or T2 cells. SSp-1-specific CTLs also lysed major histocompatibility complex (MHC)-matched tumor cell lines engineered to express S proteins. HLA-A*0201-SSp-1 tetramer staining revealed the presence of significant populations of SSp-1-specific CTLs in SSp-1-induced CD8(+) T cells. We propose that the newly identified epitope SSp-1 will help in the characterization of virus control mechanisms and immunopathology in SARS-CoV infection, and may be relevant to the development of immunotherapeutic approaches for SARS.     

Induction of HM1.24 peptide-specific cytotoxic T lymphocytes by using peripheral-blood stem-cell harvests in patients with multiple myeloma

HM1.24 antigen is preferentially overexpressed in multiple myeloma (MM) cells but not in normal cells. To explore the potential of HM1.24 as a target for cellular immunotherapy, we selected 4 HM1.24-derived peptides that possess binding motifs for HLA-A2 or HLA-A24 by using 2 computer-based algorithms. The ability of these peptides to generate cytotoxic T lymphocytes (CTLs) was examined in 20 healthy donors and 6 patients with MM by a reverse immunologic approach. Dendritic cells (DCs) were induced from peripheral-blood mononuclear cells of healthy donors or peripheral-blood stem-cell (PBSC) harvests from patients with MM, and autologous CD8(+) T cells were stimulated with HM1.24 peptide-pulsed DCs. Both interferon-gamma-producing and cytotoxic responses were observed after stimulation with either HM1.24-126 or HM1.24-165 peptides in HLA-A2 or HLA-A24 individuals. The peptide-specific recognition of these CTLs was further confirmed by tetramer assay and cold target inhibition assay. Importantly, HM1.24-specific CTLs were also induced from PBSC harvests from patients with MM and these CTLs were able to kill MM cells in an HLA-restricted manner. These results indicate the existence of functional DCs and HM1.24-specific CTL precursors within PBSC harvests and provide the basis for cellular immunotherapy in combination with autologous PBSC transplantation in MM.     

Testing recombinant adeno-associated virus-gene loading of dendritic cells for generating potent cytotoxic T lymphocytes against a prototype self-antigen,multiple myeloma HM1.24

Recent studies demonstrate that recombinant adeno-associated virus (rAAV)-based antigen loading of dendritic cells (DCs) generates significant and rapid (one stimulation per week) cytotoxic T-lymphocyte (CTL) responses in vitro against viral antigens. As a more extensive analysis of the rAAV system, we have used a self-antigen, HM1.24, expressed in multiple myeloma (MM). Again, with one stimulation, significant major histocompatibility complex (MHC) class 1-restricted, anti-HM1.24-specific CTL killing was demonstrated against MM cells. Furthermore, higher expression of interferon-gamma (IFN-gamma) in T cells and higher expression levels of, in order of significance, CD80 (2.6- to 3.8-fold increase), CD86, and CD40 on DCs were also observed. The use of synthetic HM1.24-positive target cells further demonstrated the antigen specificity of these CTLs. There was also no evidence of natural killer cell involvement. These data extend our earlier studies and suggest that the rAAV-loading of DCs may be a particularly good protocol for generating CTLs against self-antigens, which may not otherwise be considered good targets because of their low immunogenicity. We also show that HM1.24 may be an effective antigen for targeting MM.     

CD52 is not a promising immunotherapy target for most patients with multiple myeloma

The aim of our study was to evaluate CD52 as a target molecule for antibody therapy for multiple myeloma. Twenty consecutive bone marrow samples from myeloma patients were studied by flow cytometry using antibodies against CD45, CD38, CD138, CD3, CD19, and CD52. Most myeloma cells did not express CD52; CD52 expression was found only in a small subpopulation of plasma cells with a CD45+CD38++ phenotype. In contrast, the major fraction of myeloma cells (CD45-CD38++) was CD52-. Treatment of myeloma patients with anti-CD52 antibodies with the aim to reduce the number of myeloma cells in the CD45+CD38++ subfraction, which possibly contains a proliferative progenitor cell pool, would be at best a highly experimental approach. We conclude that CD52 is not a promising target for antibody-based therapies for most patients with multiple myeloma.     

Identification of HLA-A2-restricted T-cell epitopes derived from the MUC1 tumor antigen for broadly applicable vaccine therapies.

The tumor-associated antigen MUC1 is overexpressed on various hematological and epithelial malignancies and is therefore a suitable candidate for broadly applicable vaccine therapies. It was demonstrated that major histocompatibility complex (MHC)-unrestricted cytotoxic T cells can recognize epitopes of the MUC1 protein core localized in the tandem repeat domain. There is increasing evidence now that MHC-restricted T cells can also be induced after immunization with the MUC1 protein or segments of the core tandem repeat. Using a computer analysis of the MUC1 amino acid sequence, we identified two novel peptides with a high binding probability to the HLA-A2 molecule. One of the peptides is derived from the tandem repeat region and the other is derived from the leader sequence of the MUC1 protein, suggesting that, in contrast to previous reports, the MUC1-directed immune responses are not limited to the extracellular tandem repeat domain. Cytotoxic T cells (CTL) were generated from several healthy donors by primary in vitro immunization using peptide-pulsed dendritic cells. The addition of a Pan-HLA-DR binding peptide PADRE as a T-helper epitope during the in vitro priming resulted in an increased cytotoxic activity of the MUC1-specific CTL and a higher production of cytokines such as interleukin-12 and interferon-gamma in the cell cultures, demonstrating the importance of CD4 cells for an efficient CTL priming. The peptide induced CTL lysed tumors endogenously expressing MUC1 in an antigen-specific and HLA-A2-restricted fashion, including breast and pancreatic tumor cells as well as renal cell carcinoma cells, showing that these peptides are shared among many tumors. The use of MUC1-derived peptides could provide a broadly applicable approach for the development of dendritic cell-based vaccination therapies.     

ALK as a novel lymphoma-associated tumor antigen: identification of 2 HLA-A2.1-restricted CD8+ T-cell epitopes

Oncogenic anaplastic lymphoma kinase (ALK) fusion proteins (NPM/ALK and associated variants) are expressed in about 60% of anaplastic large cell lymphomas (ALCLs) but are absent in normal tissues. In this study, we investigated whether ALK, which is expressed at high levels in lymphoma cells, could be a target for antigen-specific cell-mediated immunotherapy. A panel of ALK-derived peptides was tested for their binding affinity to HLA-A*0201 molecules. Binding peptides were assessed for their capacity to elicit a specific immune response mediated by cytotoxic T lymphocytes (CTLs) both in vivo, in HLA-A*0201 transgenic mice, and in vitro in the peripheral blood lymphocytes (PBLs) from healthy donors. Two HLA-A*0201-restricted CTL epitopes, p280-89 (SLAMLDLLHV) and p375-86 (GVLLWEIFSL), both located in the ALK kinase domain were identified. The p280-89- and p375-86-induced peptide-specific CTL lines were able to specifically release interferon-gamma (IFN-gamma) on stimulation with ALK peptide-pulsed autologous Epstein-Barr virus-transformed B cells (LCLs) or T2 cells. Anti-ALK CTLs lysed HLA-matched ALCL and neuroblastoma cell lines endogenously expressing ALK proteins. CTL activity was inhibited by anti-HLA-A2 monoclonal antibody CR11.351, consistent with a class I-restricted mechanism of cytotoxicity. These results show the existence of functional anti-ALK CTL precursors within the peripheral T-cell repertoire of healthy donors, clearly indicating ALK as a tumor antigen and ALK-derived peptides, p280-89 and p375-86, as suitable epitopes for the development of vaccination strategies.     

Sperm protein 17 (Sp17) is a suitable target for immunotherapy of multiple myeloma

Sperm protein 17 (Sp17) is a protein recently identified as a novel cancer-testis (CT) antigen in multiple myeloma (MM). Because this tumor antigen demonstrates a very restricted normal tissue expression, Sp17 may be an excellent target for tumor vaccine of MM. In this study, we determined the ability to generate Sp17-specific HLA class I-restricted cytotoxic T lymphocytes (CTLs) from the peripheral blood of 4 patients with MM, 3 consecutive Sp17(+) patients, and 1 Sp17(-) patient. Dendritic cells were generated from monocytes of 4 patients with MM and used to present a recombinant Sp17 protein to autologous T cells. Following 4 rounds of antigen stimulation, the CTLs were tested for their ability to kill autologous targets in an Sp17-dependent and HLA-class I- restricted manner in standard cytotoxicity assays. Despite previous chemotherapy and the immunosuppression so often associated with MM, CTL generation was successful in all 4 patients, irrespective of the Sp17 status of their tumors. Most importantly, the CTLs were able to lyse autologous tumor cells that expressed Sp17. Tumor cell lysis in all cases appeared to be mainly mediated by perforin and could be blocked by concanamycin A. We conclude that Sp17 is a suitable target for immunotherapy of MM. Our findings provide the basis for a clinical study aimed at inducing a cellular immune response directed at Sp17(+) MM.     

Interleukin-6, a new target for therapy in multiple myeloma?

Summary During the past few years much insight has been gained into the immunobiology of multiple myeloma. It has become evident that the growth of myeloma cells is regulated by cytokines, notably interleukin-6. In this paper a brief review is given of the evidence derived from in vitro as well as in vivo observations that interleukin-6 is involved in the pathogenesis of multiple myeloma, and the implications of these findings for the development of new therapeutic strategies are discussed.     

Investigational agents in immunotherapy: a new horizon for the treatment of multiple myeloma

The treatment of multiple myeloma (MM) has gone through several major advances over the last 5 years with the introduction of next generation proteasome inhibitors (PI; carfilzomib, ixazomib) and immunomodulatory derivatives (IMiD; pomalidomide), with these new agents having a substantial impact on patient outcome. However, despite these advances, MM remains a highly resistant disease given its propensity for clonal heterogeneity and its complex interaction with the surrounding bone marrow microenvironment. Almost all patients eventually relapse despite therapeutic responses to a PI, IMiD or both. With the regulatory approval of the monoclonal antibodies Daratumumab and Elotuzumab in 2015, impressive and durable responses are being observed, even in heavily pre‐treated patients who have exhausted other therapeutic options, suggesting immunological approaches in this setting have real merit. This review will focus on newer monoclonal antibodies and chimeric‐antigen receptor (CAR) T cell strategies currently under investigation and in various stages of clinical development.     

Prediction of HLA-A2-restricted CTL epitope specific to HCC by SYFPEITHI combined with polynomial method

AIM: To predict the HLA-A2-restricted CTL epitopes of tumor antigens associated with hepatocellular carcinoma (HCC). METHODS: MAGE-1, MAGE-3, MAGE-8, P53 and AFP were selected as objective antigens in this study for the close association with HCC. The HLA-A*0201 restricted CTL epitopes of objective tumor antigens were predicted by SYFPEITHI prediction method combined with the polynomial quantitative motifs method. The threshold of polynomial scores was set to -24. RESULTS: The SYFPEITHI prediction values of all possible nonamers of a given protein sequence were added together and the ten high-scoring peptides of each protein were chosen for further analysis in primary prediction. Thirty-five candidates of CTL epitopes (nonamers) derived from the primary prediction results were selected by analyzing with the polynomial method and compared with reported CTL epitopes. CONCLUSION: The combination of SYFPEITHI prediction method and polynomial method can improve the prediction efficiency and accuracy. These nonamers may be useful in the design of therapeutic peptide vaccine for HCC and as immunotherapeutic strategies against HCC after identified by immunology experiment.     

Identification of an immunogenic DKK1 long peptide for immunotherapy of human multiple myeloma

Dickkopf-1 (DKK1), broadly expressed by tumor cells from human multiple myeloma (MM) and other cancers but absent from most normal tissues, may be an ideal target for immunotherapy. Our previous studies have shown that DKK1 (peptide)-specific cytotoxic T lymphocytes can effectively lyse primary MM cells in vitro. To develop DKK1-based vaccines that can be easily and inexpensively made and used by all patients, we identified a DKK1 long peptide (LP), DKK1_3-76-LP, that contains 74 amino acids and epitopes that can potentially bind to all major MHC class I and II molecules. Using HLA-A*0201- and HLA-DR*4-transgenic mouse models, we found that DKK1-specific CD4⁺ and CD8⁺ T-cell responses, detected by DKK1 short peptide (P20 and P66v)-HLA-A*0201 tetramer staining and cytotoxic assay for CD8⁺ T cells or by carboxyfluorescein diacetate succinimidyl ester (CSFE) dilution and IFN-g secretion for CD4⁺ T cells, respectively, can be induced in vivo by immunizing mice with the DKK1_3-76-LP. In addition, DKK1_3-76-LP also induced anti-DKK1 humoral immunity in the transgenic mice and the DKK1 antibodies were functional. Finally, DKK1_3-76-LP stimulated human blood T cells ex vivo to generate DKK1-specific CD4⁺ and CD8⁺ T-cell responses from 8 out of 10 MM patients with different MHC backgrounds. The generated DKK1-specific CD8⁺ cells efficiently lysed autologous MM cells from these patients. Thus, these results confirm the immunogenicity of the DKK1_3-76-LP in eliciting DKK1-specific CD4⁺ and CD8⁺ T-cell responses in vitro and in vivo, and suggest that the DKK1_3-76-LP can be used for immunotherapy of MM and other cancers.     

CD48 as a novel molecular target for antibody therapy in multiple myeloma

Monoclonal antibody (mAb) drugs are desirable for the improvement of multiple myeloma (MM) treatment. In this study, we found for the first time that CD48 was highly expressed on MM plasma cells. In 22 out of 24 MM patients, CD48 was expressed on more than 90% of MM plasma cells at significantly higher levels than it was on normal lymphocytes and monocytes. CD48 was only weakly expressed on some CD34(+) haematopoietic stem/progenitor cells, and not expressed on erythrocytes or platelets. We next examined whether CD48 could serve as a target antigen for mAb therapy against MM. A newly generated in-house anti-CD48 mAb induced mild antibody-dependent cell-mediated cytotoxicity and marked complement-dependent cytotoxicity against not only MM cell lines but also primary MM plasma cells in vitro. Administration of the anti-CD48 mAb significantly inhibited tumour growth in severe combined immunodeficient mice inoculated subcutaneously with MM cells. Furthermore, anti-CD48 mAb treatment inhibited growth of MM cells transplanted directly into murine bone marrow. Finally and importantly, we demonstrated that the anti-CD48 mAb did not damage normal CD34(+) haematopoietic stem/progenitor cells. These results suggest that the anti-CD48 mAb has the potential to become an effective therapeutic mAb against MM.     

Comprehensive mapping of HLA-A0201-restricted CD8 T-cell epitopes on PDC-E2 in primary biliary cirrhosis

Growing evidence has implicated the involvement of autoreactive T lymphocytes in the pathogenesis of primary biliary cirrhosis (PBC). We have recently taken advantage of motif prediction analysis of HLA-A*0201 and identified the first major histocompatibility complex (MHC) class I restricted epitope, amino acids 159 to 167 on E2 components of pyruvate dehydrogenase complexes (PDC-E2), the major mitochondrial antigens in PBC. The mechanisms involved in the selection of epitope peptide(s) that comprise the PDC-E2-specific autoreactive cytotoxic T lymphocytes (CTLs) are unknown and likely involve other epitopes on PDC-E2 restricted by MHC class I molecules. To address this issue, a comprehensive mapping of the CTL epitope repertoire on the PDC-E2 molecule that binds HLA-A*0201 was performed to provide further clues regarding the role of CTLs. We used the T2 cell line to screen 79 overlapping 15mer peptides, spanning the entire PDC-E2 molecule. Six of the 79 peptides exhibited significantly higher binding activity to HLA-A*0201 than the other 15mer peptides. Two of these 6 peptides induced CTL lines from patients with PBC. Fine mapping with N-terminus or C-terminus truncated peptides identified 10mer peptide, PDC-E2 amino acids 165 to 174, which is a novel CD8 epitope restricted by HLA-A*0201. In conclusion, using a combination of the 15mer peptide library screening with the T2 binding assay and also the induction of CTL lines with candidate peptides, we have defined a novel HLA-A*0201-restricted epitope PDC-E2 165 to 174 in patients with PBC. These data will become important in the development of altered peptide ligands to modulate disease activity.