Peptide-specific Cytotoxic T Lymphocytes Research Articles

Identification of a new HLA-A*0201-restricted cytotoxic T lymphocyte epitope from TC2N.

Identification of cytotoxic T lymphocyte (CTL) epitopes from tumor related antigens is a promising approach for malignant tumor immunotherapy. TC2N, a recently identified tumor associated antigen from human glioblastoma, is regarded as a promising target of tumor-specific immunotherapy. As one of the most widely used histocompatibility molecules in Chinese is HLA-A*0201, we were able to identify the TC2N peptides that are provided by this molecular type. A panel of antigenic peptides produced from TC2N were predicted by using a computer tool. The binding affinities of three peptides with the highest predicted score to the HLA-A*0201 molecule were evaluated after synthesis. In vitro and in vivo stimulation of the main T-cell response against the predicted peptides. The results demonstrated that TC2N (152-160) was able to release IFN-γ and lyse U251 cells in vitro as well as in vivo by eliciting peptide-specific CTLs. Our results indicated that peptide TC2N (152-160) (RLYGSVCDL) was a novel HLA-A2.1-restricted CTL epitope capable of inducing TC2N specific CTLs in vitro. As TC2N might qualify as a viable target for immunotherapeutic approaches for patients with GBM, we speculated that the newly identified epitope RLYGSVCDL would be of potential use in peptide-based, cancer-specific immunotherapy against GBM.

Randomized phase I/II study of vascular endothelial growth factor receptor peptide vaccines for patients with hepatocellular carcinoma.

We evaluated the safety and efficacy of vascular endothelial growth factor receptor (VEGFR)-targeted peptide vaccines for the immunization of patients with unresectable hepatocellular carcinoma (HCC) who had responded to transarterial chemoembolization. Twenty-two patients were randomized 1:1 to receive VEGFR-targeted peptides or placebo. The primary end-point was the safety assessment of the immunization. The secondary end-points were evaluation of immunological responses and clinical outcomes. No severe adverse events were induced by the study agents. Among the 12 patients in the vaccine group, a VEGFR1-specific cytotoxic T lymphocyte (CTL) response was induced in eight (66.7%) patients and a VEGFR2-specific CTL response was induced in 10 (83.3%). The median progression-free survival (PFS) and overall survival (OS) rates were 4.8 and 52.0months, respectively, in the vaccine group, and 2.7 and 21.8months, respectively, in the placebo group. No statistically significant differences were found between the two groups (PFS p=0.925, OS p=0.190). When divided into two groups according to immunoreactivity, the median PFS of patients with and without a strong immune response to VEGFR1 were 7.4 and 2.7months, and that to VEGFR2 were 10.6 and 2.7months, respectively; there were significant differences according to the immune response. Immunotherapy with peptide vaccines targeting VEGFR1 and VEGFR2 was well tolerated with no serious adverse events. It also effectively induced peptide-specific CTLs in patients with unresectable HCC.

Abstract 2995: Cross-presented serine proteases as immunotherapy targets for lung cancer and osteosarcoma

Abstract Background: Immunotherapy is the standard of care for many solid tumor malignancies. However, due to a paucity of known tumor antigens in non-small cell lung cancer (NSCLC) and osteosarcoma (OS), identification of novel immunogenic antigens is needed. Our group has experience with neutrophil serine proteases (NSP) derived from the azurophilic granules of polymorphonuclear leukocytes (PMN), specifically, cathepsin (CG), proteinase 3 (P3), and neutrophil elastase (NE). We have identified two HLA-A2 (HLA-A*0201)-restricted nonameric peptides: CG1 (FLLPTGAEA), derived from CG, and PR1 (VLQELNVTV), derived from NE and P3. We have previously shown that CG1 and PR1 are effective targets in hematological malignancies and that PR1 can be a target for some solid tumor malignancies. Here, we extend our findings to demonstrate that CG1 and PR1 can be immunotherapeutic targets for NSCLC and OS. Methods: Healthy donor PMN were isolated from buffy coats using double Ficoll gradient centrifugation. To evaluate uptake, malignant cells were pulsed with PMN lysates, harvested, permeabilized, and stained with anti-CG, anti-NE or anti-P3. To evaluate cross-presentation, cells were cultured with PMN lysates, harvested and stained with CG1 TCR-like antibody, or PR1 TCR-like antibody (8F4). Flow cytometry was performed using the Fortessa X-20 Cell Analyzer. CG1- or PR1-specific cytotoxic T-lymphocyte (CTL) were expanded from healthy donor peripheral blood mononuclear cells. Standard cytotoxicity assays were used to evaluate the lysis of target cells co-cultured with CG1- or PR1-specific CTL. Results: We have previously demonstrated that NE and P3 are taken up and cross-presented by NSCLC and become targets for PR1-CTL, thus in this study, we investigate if NSCLC cells take up CG, and whether OS cells take up NE and P3, resulting in enhanced cytotoxicity by peptide-specific CTLs. We first employed The Cancer Cell Line Encyclopedia to show the absence of NSP’s in NSCLC and OS cell lines. RT-PCR confirmed lack of endogenous CG mRNA expression in NSCLC and OS, and lack of NE and P3 in OS cell lines. Next, we analyzed antigen cross-presentation and showed that NSCLC cells take up and cross-present CG, leading a 13.3-fold increase in CG1-CTL killing of NSCLC cells pulsed with CG versus non-pulsed cells. In addition, OS cells take up and cross-present NE and P3, with a 13.1-fold increase in PR1-CTL killing of OS cells that were pulsed with NE and P3 vs. non-pulsed cells. Conclusion: Our data define two novel HLA-A2 restricted peptides that can be targeted in NSCLC and OS. Specifically, CG1 and PR1 are presented on the surfaces of NSCLC and OS, increasing their susceptibility to killing by CG1 and PR1 specific CTL. Our work represents a novel link between innate and adaptive immune responses in solid tumors and identifies potential antigen targets for CTL, peptide vaccines, and TCR-like antibodies in the setting of NSCLC and OS. Citation Format: Amber Gibson, Pariya Sukhumalchandra, Celine Kerros, Na Qiao, Anne Philips, Mao Zhang, Sami Alkoutami, Scott Semelsberger, Yoshimi Lu, Lauren Byers, Ze Tian, Chunhua Shi, Jun Yan, Dongxing Zha, Alejandro Marinos, Anne Sergeeva, Hong He, Lisa St. John, Jeffrey J. Molldrem, Gheath Alatrash. Cross-presented serine proteases as immunotherapy targets for lung cancer and osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2995.

Tyrosinase-Related Protein2 Peptide with Replacement of N-Terminus Residue by Cysteine Binds to H-2Kb and Induces Antigen-Specific Cytotoxic T Lymphocytes after Conjugation with CpG-DNA.

Recent studies have shown the potent efficacy of peptide-based vaccines for cancer immunotherapy. Immunological performance is optimized through the co-delivery of adjuvant and antigenic peptide molecules to antigen-presenting cells simultaneously. In our previous study, we showed that a conjugate consisting of 40-mer CpG-DNA and an antigenic ovalbumin peptide through disulfide bonding could efficiently induce ovalbumin-specific cytotoxic T lymphocyte (CTL) responses in vivo. In this study, based on the conjugation design, we prepared a conjugate consisting of 30-mer CpG-DNA (CpG30) and a cancer antigenic peptide of Tyrosinase-related protein 2 (TRP2180-188) using a cysteine residue attached at the N-terminus of TRP2180-188. However, the immunization of mice with this conjugate did not induce efficient TRP2180-188-specific immune responses. It was thought that the resultant peptide (10-mer) cleaved from the conjugate might be too long to fit into the H-2Kb molecule because the optimal length for binding to it is 8-9 amino acids. We newly designed a conjugate consisting of CpG30 and the C-TRP2181-188 peptide (9-mer), in which the N-terminal serine residue of TRP2180-188 is replaced by a cysteine. By adjusting the peptide length, we succeeded in inducing strong TRP2180-188 peptide-specific CTL activity upon immunization with the CpG30-C-TRP2181-188 conjugate. Furthermore, various CpG30-C-TRP2181-188 conjugates having other CpG-DNA sequences or cysteine analogues also induced the same level of CTL activity. Therefore, CpG-C-peptide conjugates prepared by replacement of the amino acid residue at the N-terminus with a cysteine residue could be a new and effective platform for peptide vaccines for targeting specific antigens of cancers and infectious diseases.

On the development of a neoantigen vaccine for the prevention of Lynch Syndrome

Lynch Syndrome (LS) is an autosomal dominant genetic condition that causes a high risk of colorectal cancer. The hallmark of LS is genetic instability as a result of mismatch repair (MMR) deficiency, particularly in repetitive low complexity regions called microsatellites (MS). MLH1-/- mice deficient in MMR are prone to developing tumors in the colon, upon oral administration of dextran sodium sulfate (DSS), at a rate of more than 70%. Using this LS mouse model, we found a novel tumor neo-antigen from a deletion mutation of the coding MS in the SENP6 gene that prevented tumorigenesis or hindered tumor growth rate in immunized mice. This was accomplished via high throughput exome sequencing of DSS-induced colorectal tumors in the MLH1-/- mice and predicting the most highly immunogenic mutant gene products processed and presented as antigens in C57BL/6 MHC-I molecules. Throughout our study, we were able to prove the validity of the vaccine by analyzing the colorectal tumors in immunized DSS-treated mice using either our epitope, called Sp6D1, or an unrelated peptide as a negative control. Tumors developed in this context were found to be antigenic and Sp6D1-specific CD8+ tumor infiltrating lymphocytes were detected by flow cytometry and cytotoxic T lymphocytes (CTL) killing assays. Additionally, immunohistochemistry showed that tumor-adjacent tertiary lymphoid organs were a potentially significant source of CD8+ lymphocytes. Altogether, our results indicate that there may be a protective effect to patients carrying LS mutations through the induction of a peptide-specific CTL response from the use of neoepitope vaccination.

Heat Shock Protein 105 as an Immunotherapeutic Target for Patients With Cervical Cancer.

Heat shock protein 105 (HSP105) is overexpressed in various cancers, but not in normal tissues. We investigated the expression levels of HSP105 in cervical cancer and the efficacy of immunotherapy targeting HSP105. Previously, we established human leukocyte antigen-A*02:01 (HLA-A2) restricted HSP105 peptide-specific cytotoxic T lymphocyte (CTL) clones from a colorectal cancer patient vaccinated with an HSP105 peptide. Herein, we evaluated the expression of HSP105 in cervical cancer and cervical intraepithelial neoplasia. Moreover, we tested the effectiveness of an HLA-A2-restricted HSP105 peptide-specific CTL clone against cervical cancer cell lines. HSP105 was expressed in 95% (19/20) of examined cervical cancer tissues. Moreover, the HSP105 peptide-specific CTL clone recognized HSP105- and HLA-A*02:01-positive cervical cancer cell lines and also showed that cytotoxicity against the cervical cancer cell lines depends on HSP105 peptide and HLA class I restricted manners. HSP105 could be an effective target for immunotherapy in patients with cervical cancer.

GRIK2 is a target for bladder cancer stem-like cell-targeting immunotherapy.

Recent studies have revealed that treatment-resistant cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) can be targeted by cytotoxic T lymphocytes (CTLs). CTLs recognize antigenic peptides derived from tumor-associated antigens; thus, the identification of tumor-associated antigens expressed by CSCs/CICs is essential. Human leucocyte antigen (HLA) ligandome analysis using mass spectrometry enables the analysis of naturally expressed antigenic peptides; however, HLA ligandome analysis requires a large number of cells and is challenging for CSCs/CICs. In this study, we established a novel bladder CSC/CIC model from a bladder cancer cell line (UM-UC-3 cells) using an ALDEFLUOR assay. CSCs/CICs were isolated as aldehyde dehydrogenase (ALDH)-high cells and several ALDHhigh clone cells were established. ALDHhigh clone cells were enriched with CSCs/CICs by sphere formation and tumorigenicity in immunodeficient mice. HLA ligandome analysis and cap analysis of gene expression using ALDHhigh clone cells revealed a distinctive antigenic peptide repertoire in bladder CSCs/CICs, and we found that a glutamate receptor, ionotropic, kainite 2 (GRIK2)-derived antigenic peptide (LMYDAVHVV) was specifically expressed by CSCs/CICs. A GRIK2 peptide-specific CTL clone recognized GRIK2-overexpressing UM-UC-3 cells and ALDHhigh clone cells, indicating that GRIK2 peptide can be a novel target for bladder CSC/CIC-targeting immunotherapy.

Phase II open-label study of S-588410 as maintenance monotherapy after first-line platinum-containing chemotherapy in patients with advanced or metastatic urothelial carcinoma.

440 Background: S-588410 is a cancer peptide vaccine composed of 5 human leukocyte antigen (HLA)-A*24:02-restricted epitope peptides derived from 5 cancer-testis antigens: DEPDC1, MPHOSPH1, URLC10, CDCA1 and KOC1; all of which are highly expressed in urothelial carcinoma. This study aimed to evaluate the effect of S-588410 maintenance therapy on peptide-specific cytotoxic T-lymphocyte (CTL) induction in patients with advanced or metastatic urothelial carcinoma after first-line platinum-based chemotherapy. Methods: An open-label, multicenter phase II trial was performed across 62 sites in Japan, the United Kingdom, France and Bulgaria (EudraCT 2013-005274-22). Eligible patients had completed ≥4 cycles of first-line platinum-based chemotherapy without disease progression. HLA-A*24:02-positive patients received S-588410 (1 mg of each of 5 peptides mixed with Montanide ISA 51 VG) subcutaneously weekly for 12 weeks, then every 2 weeks for up to 2 years. HLA-A*24:02-negative patients were enrolled in an observation group and did not receive study drug. The primary endpoint for the S-588410 group was the CTL induction rate at 12 weeks, defined as the proportion of patients who showed increased CTL activity for ≥1 peptide. Secondary endpoints included CTL induction rate after 1 year, antitumor effect defined by immune-related response criteria, progression-free survival (PFS), overall survival (OS), and safety. Results: A total of 81 patients with platinum-sensitive advanced or metastatic urothelial carcinoma were enrolled (S-588410 group, n=45; observation group, n=36) between April 2014 and November 2017. Most patients were male and Asian with a mean age of 67 years. CTLs were induced in 42 (93.3%) patients who received S-588410 for 12 weeks (P<0.0001, one-sided binomial test where the CTL induction rate is ≤50% as the null hypothesis). The CTL induction rate steadily increased to 95.6% within 48 weeks. CTL activity was high for the DEPDC1, MPHOSPH1 and URLC10 peptides. The response rate (immune-related complete response [CR] or partial response [PR]) was 8.9% (4/45 patients) in the S-588410 group and 0% in the observation group. Tumor imaging showed gradual (PR, n=3) and durable (CR, n=1) tumor shrinkage after ≥36 weeks in the S-588410 group. Median PFS was 18.1 weeks in the S-588410 group and 12.5 weeks in the observation group. Median OS was 71 and 99 weeks, respectively. The most frequent treatment-emergent adverse event was injection site reaction (42/45 patients [93.3%]; Grades 1–3). Pyrexia, rash and pruritus were also observed in the S-588410 group, but not the observation group. Conclusions: S-588410 showed a potent immune response and acceptable safety profile in patients with advanced or metastatic urothelial carcinoma, potentially offering a clinical benefit as post-chemotherapy maintenance therapy. Clinical trial information: EudraCT 2013-005274-22.

Use of B cell–bound HLA-A2 class I monomers to generate high-avidity, allo-restricted CTLs against the leukemia-associated protein Wilms tumor antigen

AbstractRecent studies have detected Wilms tumor antigen (WT1)-specific cytotoxic T lymphocytes (CTLs) in patients with acute myelogenous leukemia (AML) and chronic myelogenous leukemia (CML) and demonstrated that most of these CTLs were low avidity. Although HLA-mismatched donors can mount high-avidity CTLs against HLA-A2-presented peptides of WT1, a dominant anti-alloimmune response usually obscures detection of peptide-specific CTLs. Here we explored the feasibility of using recombinant HLA-A2 monomers containing single peptide epitopes as immunogens to generate peptide-specific CTLs from allogeneic donors. We demonstrate that the coating of HLA-A2- B lymphocytes with A2/peptide monomers provides a strong stimulus for autologous peptide-specific CTLs. After 3 to 5 rounds of stimulation a population of CD8+ T cells binding A2/peptide tetramers is easily detectable by fluorescence-activated cell sorting analysis. Furthermore, sorted A2/WT1 tetramer-positive CTLs display strong cytotoxic activity against leukemia cells expressing WT1 endogenously but not against WT1- human tumor cells. Thus, HLA/peptide monomers may be useful to isolate peptide-specific donor lymphocytes for treatment of patients with leukemia after HLA-mismatched transplantation. (Blood. 2004;103:4613-4615)

Exploratory open-label clinical study to determine the S-588410 cancer peptide vaccine-induced tumor-infiltrating lymphocytes and changes in the tumor microenvironment in esophageal cancer patients

Cancer vaccines induce cancer-specific T-cells capable of eradicating cancer cells. The impact of cancer peptide vaccines (CPV) on the tumor microenvironment (TME) remains unclear. S-588410 is a CPV comprising five human leukocyte antigen (HLA)-A*24:02-restricted peptides derived from five cancer testis antigens, DEPDC1, MPHOSPH1, URLC10, CDCA1 and KOC1, which are overexpressed in esophageal cancer. This exploratory study investigated the immunologic mechanism of action of subcutaneous S-588410 emulsified with MONTANIDE ISA51VG adjuvant (median: 5 doses) by analyzing the expression of immune-related molecules, cytotoxic T-lymphocyte (CTL) response and T-lymphocytes bearing peptide-specific T-cell receptor (TCR) sequencing in tumor tissue or blood samples from 15 participants with HLA-A*24:02-positive esophageal cancer. Densities of CD8+, CD8+ Granzyme B+, CD8+ programmed death-1-positive (PD-1+) and programmed death-ligand 1-positive (PD-L1+) cells were higher in post- versus pre-vaccination tumor tissue. CTL response was induced in all patients for at least one of five peptides. The same sequences of peptide-specific TCRs were identified in post-vaccination T-lymphocytes derived from both tumor tissue and blood, suggesting that functional peptide-specific CTLs infiltrate tumor tissue after vaccination. Twelve (80%) participants had treatment-related adverse events (AEs). Injection site reaction was the most frequently reported AE (grade 1, n = 1; grade 2, n = 11). In conclusion, S-588410 induces a tumor immune response in esophageal cancer. Induction of CD8+ PD-1+ tumor-infiltrating lymphocytes and PD-L1 expression in the TME by vaccination suggests S-588410 in combination with anti-PD-(L)1 antibodies may offer a clinically useful therapy.Trial registration UMIN-CTR registration identifier: UMIN000023324.

ESR1 mutations provide novel targets for breast cancer immunotherapy.

3135 Background: Estrogen receptor (ER)-positive breast cancer is not considered immunogenic. Standard treatment is endocrine therapy to include aromatase inhibitors (AI). However, constitutively activating mutations in estrogen receptor alpha ( ESR1) emerge with treatment making tumors resistant to AI therapy. While these mutations represent a pathway of resistance, they also represent potential neoepitopes that can be targeted with immunotherapy. Here we characterize the role of ESR1 mutations as novel targets for breast cancer immunotherapy. Methods: Immunogenic epitopes derived from mutated ESR1 (i.e. D538G, Y537S and E380Q) were identified in silico using the Immune Epitope Database and by determining overlapping peptides. In vitro T2 binding assays were used to measure the affinities of these peptides to HLA class-I, specifically HLA-A*0201. Dissociation assays were employed to characterize the stability of the peptide-HLA complex. Peptide-HLA-A*0201 tetramer staining was used to determine the expansion potential of peptide-specific cytotoxic T lymphocytes (CTL) from peripheral blood of healthy females. Cytotoxicity assays were used to determine the ability of peptide-specific CTLs to lyse cells presenting mutated ESR1-derived peptides. Results: We identified 22 nonameric and decameric peptides derived from the most common ESR1 mutations; 10/22 demonstrated high affinity (i.e. IC50 < 500nM) binding to HLA-A*0201. The 3 highest predicted peptides demonstrated low IC50 values (13 nM, 19.5 nM and 56.6 nM), indicating very tight binding to HLA-*0201. In vitro assays confirmed high affinity binding for 10 of the 22 in silico-predicted peptides with an average fold change of 1.52 compared to non-pulsed T2 cells, and a median dissociation half-life of 6.45 hours. Tetramer staining of peptide specific CTLs from normal donor peripheral blood mononuclear cells showed relatively high expansion frequencies, with the highest three frequencies noted for D538G (1.04%), Y537S (0.49%) and V392I (0.27%). Using 4-hour in vitro cytotoxicity assays, in comparison with non-pulsed T2 cells, there was significantly higher lysis of peptide pulsed T2 cells that were cocultured with matching peptide-specific CTL: D538G (67.1 % vs 36.9%, P < 0.001), Y537S (59.5% vs 37.5%, P < 0.01), and E380Q (36.3% vs 7.8%, P < 0.001). Conclusions: These data confirm the immunogenicity of epitopes derived from the most common ESR1 mutations. Further investigation of these peptides as part of novel immunotherapies, to include vaccine strategies is warranted.

Mixed 20-peptide cancer vaccine in combination with docetaxel and dexamethasone for castration-resistant prostate cancer: a randomized phase II trial

A novel cancer vaccine consisting of 20 mixed peptides (KRM-20) was designed to induce cytotoxic T lymphocytes (CTL) against twelve different tumor-associated antigens. The aim of this phase II trial was to examine whether KRM-20 in combination with docetaxel and dexamethasone enhances the antitumor effects in patients with castration-resistant prostate cancer (CRPC). In this double-blind, placebo-controlled, randomized phase II study, we enrolled chemotherapy-naïve patients with CRPC from ten medical centers in Japan. Eligible patients were randomly assigned 1:1 centrally to receive either KRM-20 combined with docetaxel and dexamethasone (n = 25) or placebo with docetaxel and dexamethasone (n = 26). The primary endpoint was the difference in prostate-specific antigen (PSA) decline between each treatment. The rates of > 50% PSA decline in the two arms were similar (56.5% versus 53.8%; P = 0.851). Human leukocyte antigen (HLA)-matched peptide-specific immunoglobulin G (P = 0.018) and CTL (P = 0.007) responses in the KRM-20 arm significantly increased after treatment. The addition of KRM-20 did not increase toxicity. There were no between-group differences in progression-free or overall survival (OS). The addition of KRM-20 was safe, and similar PSA decline and HLA-matched peptide-specific CTL and IgG responses increased in combination with docetaxel and dexamethasone in CRPC patients. Subgroup analysis suggested that this treatment is favorable for CRPC patients with ≥ 26% lymphocytes or PSA levels of < 11.2 ng/ml, but further clinical trials comparing OS are required.

Two unique HLA-A*0201 restricted peptides derived from cyclin E as immunotherapeutic targets in leukemia.

Immunotherapy targeting leukemia-associated antigens has shown promising results. Because of the heterogeneity of leukemia, vaccines with a single peptide have elicited only a limited immune response. Targeting several peptides together elicited peptide-specific cytotoxic T lymphocytes (CTLs) in leukemia patients, and this was associated with clinical responses. Thus, the discovery of novel antigens is essential. In the current study, we investigated cyclin E as a novel target for immunotherapy. Cyclin E1 and cyclin E2 were found to be highly expressed in hematologic malignancies, according to reverse transcription polymerase chain reaction and western blot analysis. We identified two HLA-A*0201 binding nonameric peptides, CCNE1M from cyclin E1 and CCNE2L from cyclin E2, which both elicited the peptide-specific CTLs. The peptide-specific CTLs specifically kill leukemia cells. Furthermore, CCNE1M and CCNE2L CTLs were increased in leukemia patients who underwent allogeneic hematopoietic stem cell transplantation, and this was associated with desired clinical outcomes. Our findings suggest that cyclin E1 and cyclin E2 are potential targets for immunotherapy in leukemia.

Development TACI and Bcma Dual-Antigen Targeted Immunotherapy for Multiple Myeloma

Introduction: Despite recent advances in treatment for multiple myeloma(MM), there remains a need for novel therapeutic approaches. Recently, we have reported that antigen-specific CD8+ cytotoxic T lymphocytes (CTL) with anti-MM activity can be induce by immunogenic peptides to XBP1 (X-box binding protein 1), CD138 (Syndecan-1) and CS1 (SLAMF7). Based on these results, multicenter Phase 1/2a trials are completed in patients with smoldering multiple myeloma (SMM) (JAMA Oncol.2018) and on-going in patients with SMM or triple negative breast cancer, alone and in combination with checkpoint inhibitors, lenalidomide, and HDAC6 inhibitor. We here expand the breadth and extent of MM-specific immunotherapies by targeting additional tumor-associated antigens, including B-cell maturation antigen (BCMA) and transmembrane activator and CAML interactor (TACI), TNF receptor family proteins which are involved in maturation of B-cells and highly expressed in MM. Purpose: We aim to develop a dual antigen targeted immunotherapeutic approach to induce central memory-specific anti-MM immunity and improve patient outcome. Results: We demonstrated that engineered BCMA72-80 (YLMFLLRKI) and BCMA54-62 (YILWTCLGL) peptides can evoke BCMA-specific CTL and their specific activities against MM (Bae et al. 2019). Here, we report the identification of a novel heteroclitic TACI peptide with improved HLA-A2 binding/stability compared to the native TACI peptides. The heteroclitic TACI peptide induces antigen-specific memory CD8+ CTL with robust anti-tumor activities (CD107a degranulation, Granzyme B upregulation, Th1 cytokine production) against HLA-A2+ MM (U266, McCAR) cells, but not against HLA-A2- MM (OPM2, RPMI) nor HLA-A2+ breast cancer (MDA-MB231) cells. In response to HLA-A2+ MM cells, the heteroclitic TACI peptide-specific CTL showed the antigen-specific proliferation of CD8+ CTL expressing costimulatory molecules (CD28 &gt; 41BB &gt; CD40L), which was directly associated with functional anti-tumor activity. These results suggest that the heteroclitic TACI peptide identified is a potential novel therapeutic option to effectively generate TACI-specific CD8+ memory CTL targeting MM. In on-going studies, we are evaluating a combination of immunogenic heteroclitic peptides specific to BCMA and TACI to induce highly functional antigen-specific immune responses by CD8+ Tc and CD4+ Th cells to efficiently target tumor cells. Conclusions: A novel heteroclitic TACI peptide can induce MM-specific central memory CD8+ CTL with robust poly-functional anti-tumor activities. These results provide the framework for therapeutic application targeting combination TACI and BCMA antigens in MM patients, alone and in combination with checkpoint inhibitors, epigenetic regulators and immune modulators, to both enhance anti-MM immunity and improve patient outcome. Disclosures Richardson: Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding. Munshi:Oncopep: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Adaptive: Consultancy; Abbvie: Consultancy. Anderson:Oncopep: Other: Scientific Founder; Amgen: Consultancy, Speakers Bureau; Sanofi-Aventis: Other: Advisory Board; Bristol-Myers Squibb: Other: Scientific Founder; Janssen: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau.

IMMU-23. TARGETING METASTATIC AND CNS TUMORS VIA MANNAN-BAM, TLR LIGANDS AND ANTI-CD40 ANTIBODY

Abstract Immunotherapy based on activation of innate immunity has been tested in syngeneic mouse tumor models via intratumoral administration of the following components: phagocytosis-stimulating ligands (Mannan-BAM), toll-like receptor (TLR) agonists, and immunostimulant anti-CD40 antibody (abbreviated as MBTA). In this study, syngeneic colon carcinoma (CT26) and glioma (GL261) models were established to assess MBTA’s efficacy in generating immune responses against distal metastatic lesions and CNS tumors. Additionally, we investigated if therapeutic delivery of MBTA could be optimized beyond intratumoral delivery. In the colon carcinoma model, intratumoral injection of MBTA significantly reduced all metastatic CT26 tumor growth rate and induced complete remission (CR) in 33% (3/9) of treated animals. In the glioma model, subcutaneous injection of GL261 cells incubated with MBTA resulted in the complete regression of intracranial gliomas in 87.5% (7/8) of treated animals. Therapeutic effect of MBTA was abrogated in CD4+ and CD8+ lymphocyte depleted mice. Tumor infiltrating leukocyte analyses demonstrated significantly increased CD8+ cytotoxic T-lymphocytes (CTL) in metastatic tumors with higher percentages of TNFα and IFNγ positive cells. Further assessments with MHC I tetramers revealed significantly increased CT26-associated peptide (AH1) specific CTLs in the blood of MBTA treated animals. All animals that achieved complete remission in the colon carcinoma model resisted subsequent peripheral and intracranial challenges with CT26 cells, confirming the induction of immunological memory against CT26 tumors. Collectively, our investigation demonstrates that MBTA can effectively induce a tumor-specific adaptive immune response that can target tumors located in the periphery and within the CNS.

Abstract A017: Immunologic efficacy of heat shock protein 105 peptide vaccine in patients with advanced colorectal and esophageal cancer

Abstract Purpose: Heat shock protein 105 (HSP105) is overexpressed in a variety of human cancers, including colorectal cancer (CRC) and esophageal cancer (EC). We identified HLA-A24 or A2-restricted HSP105 peptides that can induce HSP105 peptide-specific cytotoxic T lymphocytes (CTLs) (EP1536006, JP5112615, JP5291641, US9,404,925) and curried out a phase I clinical trial of HLA-A24 or A2-restricted HSP105 peptide vaccine in patients with CRC or EC (UMIN ID000017809). In this study, we aimed to demonstrate the immunological efficacy of the novel vaccine. Experimental design: 30 patients (HLA-A24 group; 15 patients, HLA-A2 group; 15 patients) with advanced CRC or EC were enrolled. Two types of vaccine (A24-1 and A24-7 or A2-7 and A2-12) were administered into the patients, matching HLA-types. Immunological responses were analyzed by ex vivo and in vitro IFN-γ ELISPOT assay using peripheral blood mononuclear cells before and after vaccination, and cytokines produced by HSP105-specific CTLs were measured by Cytometric Bead Array assay. We also analyzed the correlation between immunological responses and prognosis. Result: HSP105 peptide vaccines induced HSP105 peptide-specific CTLs in 15 of 30 patients. In HLA-A24 group, there were 7 patients with the induction only in ex vivo and almost all patients (n=13) showed skin reactions of vaccine sites. By contrast, in HLA-A2 group, there were 4 patients with the induction in ex vivo and 6 patients in in vitro, respectively, and only 6 patients with skin reactions of vaccine sites. In all patients, the existence of skin reaction correlated with the induction in ex vivo (p&amp;lt;0.01). The progression-free survival (PFS) and overall survival (OS) were significantly longer in patients with the induction (n=15) than in those without (n=15) (P&amp;lt;0.01, respectively). The peptide-specific CTL frequency correlated with OS and could be a predictive marker of PFS and OS. Furthermore, HSP105 peptide-specific cytokine production was observed in various tissues of 8 patients, such as vaccine injected sites skins, metastatic and primary tumors. It suggested that HSP105-specific CTLs not only accumulated at injected sites but also infiltrated into tumor tissues. Additionally, we succeeded in establishing two types of highly functional HSP105 peptide-specific CTL clones and sequenced the T-cell receptors (TCRs) of these clones. Conclusion: Our results suggested that HSP105 peptide vaccine could improve the prognosis of patients with advanced CRC and EC by inducing the antitumor immune responses. To further extend the efficacy, we are developing TCR-engineered T-cell therapy using TCR sequences obtained from HSP105 peptide-specific CTL clones and intratumoral injection method of this vaccine. Citation Format: Yasuhiro Shimizu, Toshiaki Yoshikawa, Kojima Takashi, Kayoko Shoda, Kazuto Nosaka, Shoichi Mizuno, Satoshi Wada, Yuki Fujimoto, Tetsuro Sasada, Kenichi Kohashi, Hideaki Bando, Itaru Endo, Tetsuya Nakatsura. Immunologic efficacy of heat shock protein 105 peptide vaccine in patients with advanced colorectal and esophageal cancer [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A017.

Identification of a novel HLA-A24-restricted cytotoxic T lymphocyte epitope peptide derived from mesothelin in pancreatic cancer.

Pancreatic cancer involves highly malignant tumors, and the development of new therapeutic strategies is critical. Mesothelin is overexpressed in infiltrating pancreatic cancer cells and plays an important role in the invasion and migration processes. In this study, we focused on mesothelin as a tumor-specific antigen target for a pancreatic cancer vaccine. We first investigated the mesothelin-derived epitope peptide restricted to HLA-A*2402. A total of 19 candidate peptides were synthesized, and we then determined their potential to induce peptide-specific cytotoxic T lymphocytes (CTLs). Peptide-specific CTLs were induced by five peptides derived from mesothelin, and these CTLs successfully exhibited peptide-specific IFN-γ production. After the expansion of each CTL, two CTL lines were established, which were induced by mesothelin-10-5 peptide (AFYPGYLCSL). These CTL lines exhibited peptide-specific cytotoxicity and IFN-γ production. Moreover, we were able to generate mesothelin-10-5 peptide-specific CTL clones. These CTL clones also had specific cytotoxic activity against HLA-A*2402-positive pancreatic cancer cells that endogenously expressed mesothelin. These results indicate that the mesothelin-10-5 peptide is a novel HLA-A*2402 restricted CTL epitope and that it is a promising candidate target for antigen-specific immunotherapy against pancreatic cancers.

Phenotype of p53 wild-type epitope-specific T cells in the circulation of patients with head and neck cancer

CD8+ cytotoxic T-cell (CTL) specific for non-mutated, wild type (wt) sequence p53 peptides derived from wt or mutant p53 molecules expressed in head and neck squamous cell carcinomas (HNSCC) have been detected in the circulation of patients with this disease. The frequency and differentiation/maturation phenotypes of these anti-tumor specific CTL can reflect the host’s immunologic response. Therefore, we investigated the frequency and phenotypes of wt sequence p53 peptide-specific CTL in patients with HNSCC (n = 33) by flow cytometric analysis using HLA-A*0201 tetrameric peptides (tet) complexed with the wt sequence p53264–272 or p53149–157 peptide and co-staining with phenotypic markers. One main finding was that increasing frequencies of tet+ CD8+ T cells in patients’ circulation correlated with increased frequencies of inactive naïve tet+ cells, while those with effector memory and terminally differentiated phenotypes, which are associated with positive anti-tumor immune responses, decreased. We also found that the frequency of circulating tet+ CD8+ T cells negatively correlated with p53 expression in tumor tissues and tumor stage. Our findings support further clinical-based investigations to define the frequencies and phenotypes of wt sequence p53 peptide-specific CD8+ T cells to predict disease severity, enhance selection of patients for inclusion in vaccination trials and highlight prerequisites to enhance immune susceptibility by activation of inactive naïve tet+ T cells and/or enhancing circulating effector T cell activity by checkpoint blockage.

Abstract 2565: EBV peptide-derived vaccine significantly enhanced in vitro cytotoxicity against EBV-positive B-cell lymphoma (EBV-BL) treatment using TMV-based delivery system

Abstract Background: EBV latent proteins (LMP-1/2) increase the chemoresistance in Burkitt Lymphoma (BL) cells by constitutively activating the CD40 receptor. It has also been demonstrated that B- cell lymphoma resistant to rituximab is a result of LMP-1 induced miR-155 expression and survival mediated by AKT phosphorylation (Hong et al.Gene Ther, 2012). EBV peptides delivered by a virus carrier (Tobacco mosaic virus;TMV) has the potential to boost immunity and stimulate potent T cell responses against EBV-associated antigens and induce a virus specific T cell response against EBV infected malignant cells (Miles/Cairo et al. BJH,2012, Kemnade/McCormick et al. Vaccine, 2014).We previously observed that obinutuzumab (Anti-CD20 mAb) significantly enhanced cell death and increased overall survival against BL (Awasthi/Cairo et al. BJH, 2015) in xenografted NSG mice. However, synergistic effects of obinutuzumab in-combination with LMP1/2-peptide vaccine against mature-B-NHL are unknown. Objective: To determine the efficacy of peptide specific cytotoxic T-lymphocytes (CTL) or the EBV vaccine alone/ in-combination with obinutuzumab against mature-B-NHL Methods: Raji4RH (provided by M. Barth, MD, Roswell Park Cancer Institute) and Raji cells (ATCC, USA) were cultured in 10% RPMI. Tumor cells were incubated with TMV-RIED IgG (LMP2) with obinutuzumab (100ug/ml) for 4 hrs with NK cells. Cytotoxicity was determined by DELFIA cytotoxicity assay at 10:1 E:T ratio. Further, to generate LMP1/LMP2 peptide specific cytotoxic T cells (CTL), mature dendritic cells were pulsated with TMV-conjugated LMP1/LMP2 peptides for 24 hrs. PBMC isolated T cells were mixed with APC (LMPs-mature -DCs) at 1:20 ratio for activation and maturation. LMP-peptide specific CTLs were investigated in-vitro for cytotoxicity efficacy against BL cell lines. Results: LMP1 and LMP2 peptide were successfully conjugated with TMV. TMV conjugated and purified serum vaccine was tested against BL cell lines. Conjugated serum vaccine (LMP2-(RIED-TMV) +obinutuzumab+NK, compared to obinutuzumab+NK or vaccine+NK alone significantly enhanced in-vitro cytotoxicity 62.67±7.82% vs. 53.66±6.43% vs. 50.8±5.2% (p=0.04 and 0.02), respectively against BL (Raji). Furthermore, cytotoxicity of CTL (LMP1-MSD-TMV) or (LMP2-TYG-TMV) cells were significantly enhanced compare to IL2 treated T cells only, 58.5±8.6% or 48.56±15.18% vs. 21.42±13.3% in Raji (P=0.01, 0.02), and 57.8±7.9% or 45.52±19.4% vs. 14.48±4.2% in Raji4RH (P=0.003, 0.002), respectively. Conclusion: Our preliminary data indicates that LMP1 (MSD-TMV) and LMP2 (TYG-TMV) successfully conjugated with TMV and TMV-conjugated peptide specific CTL cells significantly enhanced cytotoxicity against BL cell lines compared to T cells only. Citation Format: Aradhana Awasthi Tiwari, Alison McCormick, Dina Edani, Aaron Newman, Christeen Azmy, Janet Ayello, Christian Klein, Mitchell S. Cairo. EBV peptide-derived vaccine significantly enhanced in vitro cytotoxicity against EBV-positive B-cell lymphoma (EBV-BL) treatment using TMV-based delivery system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2565.

Quantitative T-cell repertoire analysis of peripheral blood mononuclear cells from lung cancer patients following long-term cancer peptide vaccination.

Therapeutic cancer peptide vaccination is an immunotherapy designed to elicit cytotoxic T-lymphocyte (CTL) responses in patients. A number of therapeutic vaccination trials have been performed, nevertheless there are only a few reports that have analyzed the T-cell receptors (TCRs) expressed on tumor antigen-specific CTLs. Here, we use next-generation sequencing (NGS) to analyze TCRs of vaccine-induced CTL clones and the TCR repertoire of bulk T cells in peripheral blood mononuclear cells (PBMCs) from two lung cancer patients over the course of long-term vaccine therapy. In both patients, vaccination with two epitope peptides derived from cancer/testis antigens (upregulated lung cancer 10 (URLC10) and cell division associated 1 (CDCA1)) induced specific CTLs expressing various TCRs. All URLC10-specific CTL clones tested showed Ca2+ influx, IFN-γ production, and cytotoxicity when co-cultured with URLC10-pulsed tumor cells. Moreover, in CTL clones that were not stained with the URLC10/MHC-multimer, the CD3 ζ chain was not phosphorylated. NGS of the TCR repertoire of bulk PBMCs demonstrated that the frequency of vaccine peptide-specific CTL clones was near the minimum detectable threshold level. These results demonstrate that vaccination induces antigen-specific CTLs expressing various TCRs at different time points in cancer patients, and that some CTL clones are maintained in PBMCs during long-term treatment, including some with TCRs that do not bind peptide/MHC-multimer.