Disulfiram's journey from rubber vulcanization to T-cell activation.

Disulfiram, a drug prescribed for the treatment of alcohol use disorders for more than 60 years, has recently been repurposed for cancer treatment. New work in The EMBO Journal now describes a disulfiram role in immunotherapy of cancer, involving direct binding to Lck to mediate activation of tumor-infiltrating T cells.

The transcription factor IRF1 dictates the IL-21-dependent anticancer functions of TH9 cells.

The TH9 subset of helper T cells was initially shown to contribute to the induction of autoimmune and allergic diseases, but subsequent evidence has suggested that these cells also exert antitumor activities. However, the molecular events that account for their effector properties are elusive. Here we found that the transcription factor IRF1 enhanced the effector function of TH9 cells and dictated their anticancer properties. Under TH9-skewing conditions, interleukin 1ß (IL-1ß) induced phosphorylation of the transcription factor STAT1 and subsequent expression of IRF1, which bound to the promoters of Il9 and Il21 and enhanced secretion of the cytokines IL-9 and IL-21 from TH9 cells. Furthermore, IL-1ß-induced TH9 cells exerted potent anticancer functions in an IRF1- and IL-21-dependent manner. Our findings thus identify IRF1 as a target for controlling the function of TH9 cells.

The unfolded protein response links tumor aneuploidy to local immune dysregulation.

Aneuploidy is a chromosomal abnormality associated with poor prognosis in many cancer types. Here, we tested the hypothesis that the unfolded protein response (UPR) mechanistically links aneuploidy and local immune dysregulation. Using a single somatic copy number alteration (SCNA) score inclusive of whole-chromosome, chromosome arm, and focal alterations in a pan-cancer analysis of 9,375 samples in The Cancer Genome Atlas (TCGA) database, we found an inverse correlation with a cytotoxicity (CYT) score across disease stages. Co-expression patterns of UPR genes changed substantially between SCNAlow and SCNAhigh groups. Pathway activity scores showed increased activity of multiple branches of the UPR in response to aneuploidy. The PERK branch showed the strongest association with a reduced CYT score. The conditioned medium of aneuploid cells transmitted XBP1 splicing and caused IL-6 and arginase 1 transcription in receiver bone marrow-derived macrophages and markedly diminished the production of IFN-γ and granzyme B in activated human T cells. We propose the UPR as a mechanistic link between aneuploidy and immune dysregulation in the tumor microenvironment.

Distinct prognostic value of circulating anti-telomerase CD4+ Th1 immunity and exhausted PD-1+/TIM-3+ T cells in lung cancer.

BACKGROUND: Despite the critical roles of Th1-polarised CD4+ T cells in cancer immunosurveillance, the translation of their potential to clinical use remains challenging. Here, we investigate the clinical relevance of circulating antitumor Th1 immunity in non-small cell lung cancer (NSCLC). METHODS: The circulating antitumor Th1 response was assessed by the ELISpot assay in 170 NSCLC patients using a mixture of HLA class II-restricted peptides from telomerase (TERT). Phenotyping of blood immune cells was performed by flow cytometry. RESULTS: TERT-reactive CD4 T-cell response was detected in 35% of NSCLC patients before any treatment. Functional analysis showed that these cells were effector memory and Th1 polarised capable to produce effector cytokines, such as IFN-γ, TNF-α and IL-2. The presence of anti-TERT Th1 response was inversely correlated with the level of exhausted PD-1+/TIM-3+CD4 T cells. The level of these two immune parameters differentially affected the survival, so that increased level of anti-TERT Th1 response and low rate of exhausted PD-1+TIM-3+CD4+ T cells were associated with a better prognosis. CONCLUSIONS: Systemic anti-TERT Th1 response plays a strong antitumor protective role in NSCLC. This study underlines the potential interest of monitoring circulating antitumor Th1 response for patients' stratification and therapy decision.

Transcriptional analysis links B cells and TERT expression to favorable prognosis in head and neck cancer.

Telomerase reverse transcriptase (TERT) is a conserved self-tumor antigen overexpressed in ∼85% of tumor cells and is immunogenic in cancer patients. The effect of TERT expression on the regulation of intratumor adaptive immunity has not yet been investigated. We used RNA sequencing data from The Cancer Genome Atlas (TCGA) in 11 solid tumor types to investigate potential interactions between TERT expression, and B and T cell infiltrate in the tumor microenvironment. We found a positive correlation between TERT expression, B and T cells in four cancer types with the strongest association in head and neck squamous cell carcinoma (HSNCC). In HNSCC a Bhigh/TERThigh signature was associated with improved progression-free survival (PFS) (P = 0.0048). This effect was independent of HPV status and not shared in comparable analysis by other conserved tumor antigens (NYESO1, MUC1, MAGE, and CEA). Bhigh/TERThigh HNSCC tumors also harbored evidence of tertiary lymphoid structure (TLS) such as signatures for germinal center (GC) and switched memory B cells, central memory CD4 and effector memory CD8 T cells. Bhigh/TERThigh HNSCC tumors also showed an up-regulation of genes and pathways related to B and T cell activation, proliferation, migration, and cytotoxicity, while factors associated with immunosuppression and cancer cell invasiveness were down-regulated. In summary, our study uncovers a new association between high TERT expression and high B cell infiltrate in HNSCC, suggesting a potential benefit from therapeutic strategies that invigorate intratumor TERT-mediated T-B cooperation.

Targeting human telomerase reverse transcriptase with recombinant lentivector is highly effective to stimulate antitumor CD8 T-cell immunity in vivo.

The success of active immunotherapy is based on the vaccine's ability to overcome immune tolerance through recalibrating the immune system so that it is able to recognize tumor antigens as foreign rather than self. In this study, we used a lentiviral vector system to target human telomerase reverse transcriptase (lv-hTERT), a widely expressed tumor antigen. Immunization of HLA-A*0201 transgenic HHD mice with recombinant lv-hTERT vector induces potent and diversified cytotoxic T lymphocyte responses that recognize in vitro murine tumor cells, which overexpress telomerase. Compared with peptide-based vaccinations, the lv-hTERT vector triggers better and more sustained CD8(+) T-cell response against self/TERT epitope in vivo. The study found that the additional use of a heterologous boosted vaccination drastically improves self/TERT-specific CD8 responses in lv-hTERT primed mice. Both primary and long-lasting self/TERT-specific CD8(+) T-cell responses induced with Iv-hTERT vector required the presence of CD4 T cells in vivo. This lv-hTERT-based active immunotherapy efficiently inhibits the growth of telomerase expressing tumors (B16/HLA-A2.1 murine melanoma) in HHD mice. These data show that targeting hTERT with lentivector is highly effective in stimulating a broad range of CD8 T-cell immunity that can be exploited for cancer immunotherapy.

The angiogenic growth factor and biomarker midkine is a tumor-shared antigen.

The angiogenic factor Midkine (MDK) is overexpressed in various human malignant tumors, although its expression is low or undetectable in normal adult tissues. Its expression in tumors and its detection in plasma have been associated with poor disease outcome, whereas its blockade was found to contribute to tumor regression. By weekly stimulation of T lymphocytes harvested in HLA-A2 healthy donors, we derived CD8 T cell lines specific for several MDK peptides. The T cell response was mostly dominated by two nonamer peptides localized in the signal peptide and in the C-terminal part of the protein, as assessed by IFN-gamma ELISPOT and HLA-A2 tetramer labeling. Peptide-specific T cell lines recognized cells transfected with an MDK-encoded plasmid and tumor cell lines naturally expressing the MDK protein, but not untransfected cells. T cell presentation of the two MDK epitopes was found to be TAP dependent. Experiments performed in HLA-A2 transgenic mice demonstrated the capacity of the two identified CD8 T cell epitopes to elicit a cytotoxic response. Altogether, our data show that the secreted MDK protein is a candidate vaccine for multiple cancers.

The Unfolded Protein Response at the Tumor-Immune Interface.

The tumor-immune interface has surged to primary relevance in an effort to understand the hurdles facing immune surveillance and cancer immunotherapy. Reports over the past decades have indicated a role for the unfolded protein response (UPR) in modulating not only tumor cell fitness and drug resistance, but also local immunity, with emphasis on the phenotype and altered function of immune cells such as myeloid cells and T cells. Emerging evidence also suggests that aneuploidy correlates with local immune dysregulation. Recently, we reported that the UPR serves as a link between aneuploidy and immune cell dysregulation in a cell nonautonomous way. These new findings add considerable complexity to the organization of the tumor microenvironment (TME) and the origin of its altered function. In this review, we summarize these data and also discuss the role of aneuploidy as a negative regulator of local immunity.

Chemoradiation triggers antitumor Th1 and tissue resident memory-polarized immune responses to improve immune checkpoint inhibitors therapy.

BACKGROUND: Multiple synergistic combination approaches with cancer drugs are developed to overcome primary resistance to immunotherapy; however, the mechanistic rationale to combine chemoradiotherapy (CRT) with immune checkpoint inhibitors remains elusive. METHODS: This study described the immunological landscape of tumor microenvironment (TME) exposed to CRT. Tumor samples from patients with rectal cancer (n=43) treated with neoadjuvant CRT or radiotherapy were analyzed by nanostring and immunohistochemistry. Studies in mice were performed using three syngeneic tumors (TC1, CT26 and MC38). Tumor-bearing mice were treated either with platinum-based CRT, radiotherapy or chemotherapy. Anti-CTLA-4 and/or anti-Programmed Cell Death Receptor-1 (PD-1) therapy was used in combination with CRT. The therapy-exposed TME was screened by RNA sequencing and flow cytometry and tumor-infiltrating T lymphocyte functionality was evaluated by interferon (IFN)-γ ELIspot and intracellular cytokine staining. RESULTS: Front-to-front comparison analysis revealed the synergistic effect of CRT to establish a highly inflamed and Th1-polarized immune signature in the TME of patients and mice. In both settings, CRT-exposed TMEs were highly enriched in newly-infiltrated tumor-specific CD8+ T cells as well as tissue resident memory CD103+CD8+ T cells. In mice, CD8 T cells were involved in the antitumor response mediated by CRT and were primed by CRT-activated CD103+ dendritic cells. In the three tumor models, we showed that concurrent combination of CRT with a dual CTLA-4 and PD-1 blockade was required to achieve an optimal antitumor effect and to establish a broad and long-lasting protective antitumor T cell immunity. CONCLUSIONS: Our results highlight the ability of CRT to stimulate strong antitumor T-cell-mediated immunity and tissue resident memory T activation in TME, to foster immune checkpoint inhibitors action. These findings have implications in clinic for the design clinical trials combining chemoradiation with immunotherapy.

Telomerase and CD4 T Cell Immunity in Cancer.

Telomerase reverse transcriptase (TERT) is a conserved self-tumor antigen which is overexpressed in most tumors and plays a critical role in tumor formation and progression. As such, TERT is an antigen of great relevance to develop widely applicable immunotherapies. CD4 T cells play a major role in the anti-cancer response alone or with other effector cells such as CD8 T cells and NK cells. To date, efforts have been made to identify TERT peptides capable of stimulating CD4 T cells that are also able to bind diverse MHC-II alleles to ease immune status monitoring and immunotherapies. Here, we review the current status of TERT biology, TERT/MHC-II immunobiology, and past and current vaccine clinical trials. We propose that monitoring CD4 T cell immunity against TERT is a simple and direct way to assess immune surveillance in cancer patients and a new way to predict the response to immune checkpoint inhibitors (ICPi). Finally, we present the initial results of a systematic discovery of TERT peptides able to bind the most common HLA Class II alleles worldwide and show that the repertoire of MHC-II TERT peptides is wider than currently appreciated.

Modulation of Determinant Factors to Improve Therapeutic Combinations with Immune Checkpoint Inhibitors.

Immune checkpoint inhibitors (ICPi) have shown their superiority over conventional therapies to treat some cancers. ICPi are effective against immunogenic tumors. However, patients with tumors poorly infiltrated with immune cells do not respond to ICPi. Combining ICPi with other anticancer therapies such as chemotherapy, radiation, or vaccines, which can stimulate the immune system and recruit antitumor T cells into the tumor bed, may be a relevant strategy to increase the proportion of responding patients. Such an approach still raises the following questions: What are the immunological features modulated by immunogenic therapies that can be critical to ensure not only immediate but also long-lasting tumor protection? How must the combined treatments be administered to the patients to harness their full potential while limiting adverse immunological events? Here, we address these points by reviewing how immunogenic anticancer therapies can provide novel therapeutic opportunities upon combination with ICPi. We discuss their ability to create a permissive tumor microenvironment through the generation of inflamed tumors and stimulation of memory T cells such as resident (TRM) and stem-cell like (TSCM) cells. We eventually underscore the importance of sequence, dose, and duration of the combined anticancer therapies to design optimal and successful cancer immunotherapy strategies.

Immunoregulation and Clinical Implications of ANGPT2/TIE2+ M-MDSC Signature in Non-Small Cell Lung Cancer.

Myeloid-derived suppressor cells (MDSC) promote immunosuppression and are a target in the field of immuno-oncology. Accumulation of MDSCs is associated with poor prognosis and resistance to immunotherapy for several cancers. Here, we describe an accumulation of a subset of circulating monocytic MDSCs (M-MDSC) overexpressing TIE2, the receptor for angiopoietin-2 (ANGPT2), in patients with non-small cell lung cancer (NSCLC). Greater numbers of circulating TIE2+ M-MDSCs were detected in patients with NSCLC compared with healthy subjects, and this accumulation correlated with ANGPT2 concentration in blood. The presence of an ANGPT2-rich environment was associated with impairment of preexisting T-cell responses against tumor-associated antigens (TAA) in patients with NSCLC. We demonstrated that ANGPT2 sensitizes TIE2+ M-MDSCs such that these cells suppress TAA-specific T cells. In patients with NSCLC, upregulation of the ANGPT2/TIE2+ M-MDSC signature in blood was associated with a poor prognosis. Our results identify the ANGPT2/TIE2+ M-MDSC axis as a participant in tumor immune evasion that should be taken into account in future cancer immunotherapy.

Cleaved Caspase-3 Transcriptionally Regulates Angiogenesis-Promoting Chemotherapy Resistance.

Caspases are well known for their role in apoptosis. Recently, nonapoptotic roles of caspases have been identified, however, these noncanonical roles are not well documented and the mechanisms involved are not fully understood. Here, we studied the role of cleaved caspase-3 using human- and mouse-proficient caspase-3 cancer cell lines and human-deficient caspase-3 cancer cells. Cleaved caspase-3 functioned as a transcription factor and directly bound to DNA. A DNA-binding domain was identified in the small subunit of caspase-3 and an active conformation was essential for caspase-3 transcriptional activity. Caspase-3 DNA binding enhanced angiogenesis by upregulating the expression of proangiogenic genes and by activating pathways that promoted endothelial cell activation. Some proapoptotic genes were downregulated in caspase-3-proficient cells. Inhibiting caspase-3 increased the efficacy of chemotherapy and decreased spontaneous tumor development. These data highlight a novel nonapoptotic role of caspase-3 and suggest that cleaved caspase-3 could be a new therapeutic target in cancer. SIGNIFICANCE: These findings report a noncanonical function of caspase-3 by demonstrating its ability to transcriptionally regulate the VEGFR pathway.

Circulating NKp46+ Natural Killer cells have a potential regulatory property and predict distinct survival in Non-Small Cell Lung Cancer.

Natural killer (NK) cells are innate effector lymphocytes widely involved in cancer immunosurveillance. In this study, we described three circulating NK cell subsets in patients with non-small cell lung cancer (NSCLC). Compared to healthy donors (HD), lower rate of the cytotoxic CD56dim CD16+ NK cells was found in NSCLC patients (76.1% vs 82.4%, P = 0.0041). In contrast, the rate of CD56bright NK cells was similar between patients and HD. We showed in NSCLC patients a higher rate of a NK cell subset with CD56dim CD16- phenotype (16.7% vs 9.9% P = 0.0001). The degranulation property and cytokines production were mainly drive by CD56dim CD16- NK cell subset in patients. Analysis of natural cytotoxicity receptors (NCRs) expression identified four distinct clusters of patients with distinct NK cell subset profiles as compared to one major cluster in HD. Notably the cluster characterized by a low circulating level of NKp46+ NK cell subsets was absent in HD. We showed that the rate of circulating NKp46+ CD56dim CD16+ NK cells influenced the patients' survival. Indeed, the median overall survival in patients exhibiting high versus low level of this NK cell subset was 16 and 27 months respectively (P = 0.02). Finally, we demonstrated that blocking NKp46 receptor in vitro was able to restore spontaneous tumor specific T cell responses in NSCLC patients. In conclusion, this study showed a distinct distribution and phenotype of circulating NK cell subsets in NSCLC. It also supports the regulatory role of NKp46+ NK cell subset in NSCLC patients.

Personalized identification of tumor-associated immunogenic neoepitopes in hepatocellular carcinoma in complete remission after sorafenib treatment.

Sorafenib, a multi-targeted kinase inhibitor, is the current standard systemic treatment for advanced hepatocellular carcinoma. Sorafenib has anti-angiogenic and anti-proliferative properties and is also known to favor anti-tumor T cell responses by reducing the population of immunosuppressive cells such as Treg and MDSC. Anti-tumor immune responses, especially mediated by CD4+ T-cells, are critical for tumor cells eradication and therapies modulating those responses are appealing in a growing number of cancers. Here, we report and investigate the case of a patient diagnosed with an advanced HCC treated by sorafenib who experienced a complete histological response. We aimed to identify immunogenic peptides derived from tumor mutated proteins that stimulated CD4+ T cells responses thus favoring the exceptional recovery process of this patient. Tumor neoantigens were identified using whole exome sequencing of normal and tumor tissue and peptide MHC binding prediction algorithms. Among 442 tumor-specific somatic variants, 50 missense mutations and 20 neoepitopes predicted to bind MHC-II were identified. Candidate neoepitopes immunogenicity was assessed by IFN-γ ELISpot after culture of patient's PBMCs in presence of synthetic neopeptides. CD4+ memory T cell responses were detected against a mutated IL-1ßS230F peptide and two additional neoepitopes from HELZ2V241M and MLL2A4458V suggesting that efficient anti-tumor immune response occurred in this patient. These results showed that T cells can recognize neoantigens and may lead to the cancer elimination after immunomodulation in the tumor-microenvironment induced by sorafenib. This observation indicates that other immunotherapies in combination with sorafenib could potentially increase the response rate in HCC at advanced stage.

PD-1/PD-L1 pathway: an adaptive immune resistance mechanism to immunogenic chemotherapy in colorectal cancer.

BACKGROUND: Chemotherapy is currently evaluated in order to enhance the efficacy of immune checkpoint blockade (ICB) therapy in colorectal cancer. However, the mechanisms by which these drugs could synergize with ICB remains unclear. The impact of chemotherapy on the PD-1/PD-L1 pathway and the resulting anticancer immune responses was assessed in two mouse models of colorectal cancer and validated in tumor samples from metastatic colorectal cancer patients that received neoadjuvant treatment. We demonstrated that 5-Fluorouracil plus Oxaliplatin (Folfox) drove complete tumor cure in mice when combined to anti-PD-1 treatment, while each monotherapy failed. This synergistic effect relies on the ability of Folfox to induce tumor infiltration by activated PD-1+ CD8 T cells in a T-bet dependent manner. This effect was concomitantly associated to the expression of PD-L1 on tumor cells driven by IFN-γ secreted by PD-1+ CD8 T cells, indicating that Folfox triggers tumor adaptive immune resistance. Finally, we observed an induction of PD-L1 expression and high CD8 T cell infiltration in the tumor microenvironment of colorectal cancer patients treated by Folfox regimen. Our study delineates a molecular pathway involved in Folfox-induced adaptive immune resistance in colorectal cancer. The results strongly support the use of immune checkpoint blockade therapy in combination with chemotherapies like Folfox.

Selective degradation of PU.1 during autophagy represses the differentiation and antitumour activity of TH9 cells.

Autophagy, a catabolic mechanism that involves degradation of cellular components, is essential for cell homeostasis. Although autophagy favours the lineage stability of regulatory T cells, the contribution of autophagy to the differentiation of effector CD4 T cells remains unclear. Here we show that autophagy selectively represses T helper 9 (TH9) cell differentiation. CD4 T cells lacking Atg3 or Atg5 have increased interleukin-9 (IL-9) expression upon differentiation into TH9 cells relative to Atg3- or Atg5-expressing control cells. In addition, the TH9 cell transcription factor, PU.1, undergoes K63 ubiquitination and degradation through p62-dependent selective autophagy. Finally, the blockade of autophagy enhances TH9 cell anticancer functions in vivo, and mice with T cell-specific deletion of Atg5 have reduced tumour outgrowth in an IL-9-dependent manner. Overall, our findings reveal an unexpected function of autophagy in the modulation of TH9 cell differentiation and antitumour activity, and prompt potential autophagy-dependent modulations of TH9 activity for cancer immunotherapy.Autophagy is a cellular process for recycling cell constituents, and is essential for T cell activation, but its function in T cell polarization is still unclear. Here the authors show that autophagy induces the degradation of transcription factor PU.1 to negatively modulate TH9 homeostasis and antitumour immunity.

Identification of a novel PD-L1 positive solid tumor transplantable in HLA-A*0201/DRB1*0101 transgenic mice.

HLA-A*0201/DRB1*0101 transgenic mice (A2/DR1 mice) have been developed to study the immunogenicity of tumor antigen-derived T cell epitopes. To extend the use and application of this mouse model in the field of antitumor immunotherapy, we described a tumor cell line generated from a naturally occurring tumor in A2/DR1 mouse named SARC-L1. Histological and genes signature analysis supported the sarcoma origin of this cell line. While SARC-L1 tumor cells lack HLA-DRB1*0101 expression, a very low expression of HLA-A*0201 molecules was found on these cells. Furthermore they also weakly but constitutively expressed the programmed death-ligand 1 (PD-L1). Interestingly both HLA-A*0201 and PD-L1 expressions can be increased on SARC-L1 after IFN-γ exposure in vitro. We also obtained two genetically modified cell lines highly expressing either HLA-A*0201 or both HLA-A*0201/ HLA-DRB1*0101 molecules referred as SARC-A2 and SARC-A2DR1 respectively. All the SARC-L1-derived cell lines induced aggressive subcutaneous tumors in A2DR1 mice in vivo. The analysis of SARC-L1 tumor microenvironment revealed a strong infiltration by T cells expressing inhibitory receptors such as PD-1 and TIM-3. Finally, we found that SARC-L1 is sensitive to several drugs commonly used to treat sarcoma and also susceptible to anti-PD-L1 monoclonal antibody therapy in vivo. Collectively, we described a novel syngeneic tumor model A2/DR1 mice that could be used as preclinical tool for the evaluation of antitumor immunotherapies.

Immunoprevalence and magnitude of HLA-DP4 versus HLA-DR-restricted spontaneous CD4(+) Th1 responses against telomerase in cancer patients.

Cumulative evidence supports that CD4(+) Th1 cells play a key role in antitumor immunity. We previously reported the presence of spontaneous HLA-DR-restricted CD4(+) Th1 responses against telomerase reverse transcriptase (TERT) in various cancers by using promiscuous HLA-DR epitopes. Here, we described novel highly immunogenic HLA-DP4-binding epitopes from TERT named TERT541-555, TERT573-587, TERT613-627 and TERT911-925 and addressed the question about the immunoprevalence and magnitude of the naturally occurring antitumor CD4(+) T cell responses restricted by HLA-DP4 or HLA-DR, the two most common HLA class II. Direct comparative study of spontaneous anti-TERT CD4(+) T cell responses in a cohort of 87 lung cancer patients showed that HLA-DP4 and HLA-DR sustained specific Th1 responses in 10.1% and 25.2% of cancer patients respectively (p = 0.01). The magnitude of the HLA-DR-restricted responses was two to three times significantly higher than HLA-DP one (p = 0.005). Similar results were found in other cancers such as melanoma, breast cancer, renal cell carcinoma and colon cancer. Thus, our results describe for the first time in a large cohort of cancer patients a high immunoprevalence of HLA-DR-restricted spontaneous anti-TERT Th1 immunity compared to HLA-DP restriction. These results provide a new tool for comprehensive monitoring of antitumor CD4(+) Th1 response in various cancers.

Immunogenicity evaluation of a rationally designed polytope construct encoding HLA-A*0201 restricted epitopes derived from Leishmania major related proteins in HLA-A2/DR1 transgenic mice: steps toward polytope vaccine.

BACKGROUND: There are several reports demonstrating the role of CD8 T cells against Leishmania species. Therefore peptide vaccine might represent an effective approach to control the infection. We developed a rational polytope-DNA construct encoding immunogenic HLA-A2 restricted peptides and validated the processing and presentation of encoded epitopes in a preclinical mouse model humanized for the MHC-class-I and II. METHODS AND FINDINGS: HLA-A*0201 restricted epitopes from LPG-3, LmSTI-1, CPB and CPC along with H-2Kd restricted peptides, were lined-up together as a polytope string in a DNA construct. Polytope string was rationally designed by harnessing advantages of ubiquitin, spacers and HLA-DR restricted Th1 epitope. Endotoxin free pcDNA plasmid expressing the polytope was inoculated into humanized HLA-DRB1*0101/HLA-A*0201 transgenic mice intramuscularly 4 days after Cardiotoxin priming followed by 2 boosters at one week interval. Mice were sacrificed 10 days after the last booster, and splenocytes were subjected to ex-vivo and in-vitro evaluation of specific IFN-γ production and in-vitro cytotoxicity against individual peptides by ELISpot and standard chromium-51 (51Cr) release assay respectively. 4 H-2Kd and 5 HLA-A*0201 restricted peptides were able to induce specific CD8 T cell responses in BALB/C and HLA-A2/DR1 mice respectively. IFN-γ and cytolytic activity together discriminated LPG-3-P1 as dominant, LmSTI-1-P3 and LmSTI-1-P6 as subdominant with both cytolytic activity and IFN-γ production, LmSTI-1-P4 and LPG-3-P5 as subdominant with only IFN-γ production potential. CONCLUSIONS: Here we described a new DNA-polytope construct for Leishmania vaccination encompassing immunogenic HLA-A2 restricted peptides. Immunogenicity evaluation in HLA-transgenic model confirmed CD8 T cell induction with expected affinities and avidities showing almost efficient processing and presentation of the peptides in relevant preclinical model. Further evaluation will determine the efficacy of this polytope construct protecting against infectious challenge of Leishmania. Fortunately HLA transgenic mice are promising preclinical models helping to speed up immunogenicity analysis in a human related mouse model.