An unmet need: Harmonization of IL-7 and IL-15 combination for the ex vivo generation of minimally differentiated T cells

T cell-based adoptive cell transfer therapy is now clinically used to fight cancer with CD19-targeting chimeric antigen receptor T cells. The use of other T cell-based immunotherapies relying on antigen-specific T cells, genetically modified or not, is expanding in various neoplastic diseases. T cell manufacturing has evolved through sophisticated processes to produce T cells with improved therapeutic potential. Clinical-grade manufacturing processes associated with these therapies must meet pharmaceutical requirements and therefore be standardized. Here, we focus on the use of cytokines to expand minimally differentiated T cells, as well as their standardization and harmonization in research and clinical settings.

Validation of a method evaluating T cell metabolic potential in compliance with ICH Q2 (R1)

BACKGROUND

Metabolic cell features are able to give reliable information on cell functional state. Thus, metabolic potential assessment of T cells in malignancy setting represents a promising area, especially in adoptive cell therapy procedures. Easy to set up and convenient Seahorse technology have recently been proposed by Agilent Technologies and it could be used to monitor T cells metabolic potential. However, this method demonstrates an inter-assay variability and lacks practices standardization.

RESULTS

We aimed to overcome these shortcomings thanks to a lymphoblastic derived JURKAT cell line seeding in each experiment to standardize the Seahorse process. We used an adapted XF Cell MitoStress Kit protocol, consisting in the evaluation of basal, stressed and maximal glycolysis and oxidative phosphorylation related parameters, through sequential addition of oligomycin and carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) to a glucose containing medium. Data were acquired and analyzed through Agilent Seahorse XFe96 analyzer. Indeed, we validated this method in the light of ICH Q2 (R1) guidelines. We were able to confirm the specificity and accuracy of the method. We also demonstrated the precision, linearity and range of the method in our experimental conditions.

CONCLUSION

The validation of the method consisting in a JURKAT cell line experimental incorporation as a control material contributes to improve the Seahorse technology's robustness. These results lay the groundwork for the implementation of this technology to optimize T cell based cellular therapy products production process and monitoring.

CD4 T cells target colorectal cancer antigens upregulated by oxaliplatin

Immune checkpoint blockade has proven its efficacy in hypermutated subtypes of metastatic colorectal cancers (mCRC). Immunogenic potential can also be observed with conventional chemotherapies, but this property has never been explored thoroughly in CRC patients. The CRC therapeutic arsenal includes oxaliplatin, a well-characterized platinum drug already described as immunogenic. Here, we investigated the impact of the oxaliplatin-based treatment on mCRC immunopeptidome. We demonstrated that oxaliplatin-resistant CRC cell lines overexpressed telomerase reverse transcriptase (TERT), colorectal-associated-tumor antigen-1 (COA-1) and mesothelin tumor-associated antigens. We identified new HLA class-II-restricted and promiscuous peptides derived from COA-1 and mesothelin. The two naturally processed peptides COA-1_331-345 and Meso_366-380 appear to be the most immunogenic in mCRC patients. A prospective cohort of 162 mCRC patients enabled us to explore the impact of oxaliplatin exposure on the antitumor-specific immune response. Interestingly, chemotherapy-naive mCRC patients present high immune CD4 T-cell responses directed against TERT, COA-1 and mesothelin-derived peptides. These antitumor T-cell responses were maintained after 3 months of oxaliplatin-based treatment. Altogether, these findings highlight the interest of immunostimulatory agents to improve the management of chemoresistant mCRC patients. Finally, the high frequency of immune responses targeting the new immunogenic peptides derived from COA-1 and mesothelin support their use in immunomonitoring strategies.

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-1βS230F 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.

Isolation and Characterization of an HLA-DRB1*04-Restricted HPV16-E7 T Cell Receptor for Cancer Immunotherapy

High-risk human papillomavirus (HPV) infection is a causal factor in oropharyngeal and gynecological malignancies, and development of HPV-targeted immunotherapy could be used to treat patients with these cancers. T cell-mediated adoptive immunotherapy targeting E6 and E7, two HPV16 proteins consistently expressed in tumor cells, appears to be both attractive and safe. However, isolation of HPV-specific T cells is difficult owing to the low frequency of these cell precursors in the peripheral blood. In addition, HPV-positive cancer cells often down-regulate major histocompatibility complex (MHC) class I expression ex vivo, limiting the efficacy of MHC class I-restricted approaches. Of particular interest is that both CD4 and CD8 T cells can mediate the responses. Given that CD4 T cells play a critical role in coordinating effective antitumor responses, the generation of a T helper response in patients with HPV16-associated malignancies would unleash the ultimate potential of immunotherapy. In this view, T-cell receptor (TCR) gene transfer could be a relevant strategy to generate HPV16-E7-specific and MHC class II-restricted T cells in sufficient numbers. An HPV16-E7/HLA-DRB1*04 TCR has been isolated from a cancer patient with complete response, and retroviral particles encoding this TCR have been produced. The transgenic TCR is highly expressed in transduced T cells, with a functional inducible caspase-9 suicide gene safety cassette. TCR transgenic T cells are HPV16-E7_70-89 specific and HLA-DRB1*04 restricted, as determined by interferon (IFN)-γ secretion. CD8 and CD4 T cells are equivalently transduced and secrete interleukin-2 and IFN-γ when cultured with appropriate targets. We also demonstrate that TCR transgenic T cells recognize the endogenously processed and presented HPV16-E7_70-89 peptide. In conclusion, our data indicate that the production of MHC class II-restricted HPV16-E7-specific T cells is feasible through TCR gene transfer and could be used for immunotherapy.

SALL4 oncogene is an immunogenic antigen presented in various HLA-DR contexts

Purpose: To investigate the immunoprevalence of SALL4-derived peptides in healthy volunteers and cancer patients. Experimental Design: A multistep approach including prediction algorithms was used to design in silico SALL4-derived peptides theoretically able to bind on common HLA-DR and HLA-A/B molecules. The presence of T-cell responses after a long term T-cell assay (28 days) against SALL4 was monitored in 14 healthy donors and the presence of T-cell responses after a short term T-cell assay (10 days) was monitored in 67 cancer patients using IFN-γ ELISPOT assay. A T-cell clone specific for the immunoprevalent A18 K-derived peptide was isolated, characterized and used as a tool to characterize the natural processing of A18 K. Results: A SALL4 specific T-cell repertoire was present in healthy donors (8/14) and cancer patients (29/67) after short term T-cell assay. We further identified two immunoprevalant SALL4-derived peptides, R18 A and A18 K, which bind MHC-class II. In parallel, an A18 K specific Th1 clone recognized monocyte derived Dendritic Cell (moDC) loaded with SALL4 containing cell lysate. The level of IFN-γ secreted by specific T-cell clone was greater in presence of moDC loaded with SALL4 containing cell lysate (49.23 ± 14.02%) than with moDC alone (18.03 ± 3.072%) (p = 0.0477) Conclusion: These results show for the first time immunogenicity of SALL4 oncogenic protein-derived peptides, especially A18 K and R18 A peptides and make them potential targets for personalized medicine. Thus, SALL4 possess major characteristics of a tumor antigen.

IL-21-Induced MHC Class II+ NK Cells Promote the Expansion of Human Uncommitted CD4+ Central Memory T Cells in a Macrophage Migration Inhibitory Factor-Dependent Manner

NK cells are critical for innate immunity-mediated protection. The main roles of NK cells rely on their cytotoxic functions or depend on the tuning of Th1 adaptive immunity by IFN-γ. However, the precise influence of inflammatory cytokines on NK cell and CD4 T lymphocyte interactions was never investigated. In this study, we provide evidence that IL-21, a cytokine produced during chronic inflammation or infectious diseases, promotes the differentiation of a specific subset of NK cells coexpressing CD86 and HLA-DR and lacking NKp44. More importantly, IL-21-propagated HLA-DR(+) NK cells produce macrophage migration inhibitory factor and provide costimulatory signaling during naive CD4(+) T cell priming inducing the differentiation of uncommitted central memory T cells. Central memory T cells expanded in the presence of HLA-DR(+) NK cells are CXCR3(+)CCR6(-)CCR4(-)CXCR5(-) and produce IL-2, as well as low levels of TNF-α. Costimulation of CD4(+) T cells by HLA-DR(+) NK cells prevents the acquisition of effector memory phenotype induced by IL-2. Moreover, we identified this population of NK HLA-DR(+) macrophage migration inhibitory factor(+) cells in inflammatory human appendix. Collectively, these results demonstrate a novel function for IL-21 in tuning NK and CD4(+) T cell interactions promoting a specific expansion of central memory lymphocytes.

Early immune response against retrovirally transduced herpes simplex virus thymidine kinase-expressing gene-modified T cells coinfused with a T cell-depleted marrow graft: an altered immune response?

Administration of herpes simplex thymidine kinase (HSV-tk)-expressing, gene-modified T cells (GMCs) with T cell-depleted bone marrow transplantation (TCD-BMT) can allow modulation of posttransplantation alloreactivity. Twelve patients received 2 x 10(5) to 2 x 10(6) CD3+ donor GMCs per kilogram with HLA-identical sibling TCD-BMT. Despite extensive T cell depletion of bone marrow, an intensive conditioning regimen, and immunosuppressive graft-versus-host disease (GvHD) prophylaxis, infusion at the time of TCD-BMT of this low number of GMCs sufficed to induce a rapid GMC-specific immune response, as detected by interferon- enzyme- linked immunospot assay in six of eight patients, preferentially targeting HSV-tk. Maximal responses were reached early (median time, 49 [35-68] days post-BMT), with a subsequent rapid and significant decrease in five of six evaluable patients. Immune responses were negatively correlated with the maximal circulating GMC counts. However, such immune response did not result in the elimination of circulating GMCs and was not associated with measurable ex vivo cytotoxic activity against GMCs. Furthermore, alloreactive GMCs still could induce GCV-sensitive GvHD in one patient despite an ongoing immune response. Overall, infusion of HSV-tk-expressing GMCs at the time of BMT results in an early immune response. Such immune response may be altered and may not prevent persistent GCV-sensitive alloreactivity.

Alloreactivity of ex vivo-expanded T cells is correlated with expansion and CD4/CD8 ratio

Background We have demonstrated previously that retroviral-mediated transfer of a suicide gene into bone marrow (BM) donor T cells allows an efficient control of graft-versus-host disease (GvHD) after allogeneic BM transplantation. However, the 12 days of ex vivo culture required for the production of gene-modified cells (GMC), including soluble CD3 monoclonal antibody (MAb)-mediated activation and expansion with interleukin (IL)-2, induced a decrease of GMC alloreactivity and a reversal of their CD4/CD8 ratio. Improving the culture protocol in order to maintain the highest alloreactivity is of critical importance in obtaining an optimal graft-versus-leukemia (GvL) effect. Methods Peripheral blood mononuclear cells were activated with soluble CD3 MAb or CD3 and CD28 MAb co-immobilized on beads and expanded for 12 days in the presence of IL-2, IL-7 or IL-15 before analysis of alloreactivity and phenotype. Results Replacing the CD3 MAb by CD3/CD28 beads led to similar in vitro alloreactivity but improved the expansion and in vivo alloreactivity of GMC. Replacing the IL-2 with IL-7, but not IL-15, or decreasing IL-2 or IL-7 concentrations, improved the in vitro alloreactivity of expanded cells but was associated with lower expansion. Indeed, the alloreactivity of expanded cells was negatively correlated with cell expansion and positively correlated with CD4/CD8 ratio and CD8 expression level. Discussion Quantitative (i.e. low CD4/CD8 ratio) and qualitative (e.g. low CD8 expression) defects may account for the decreased alloreactivity of GMC. Using CD3/CD28 beads and/or IL-7 is more beneficial than CD3 MAb and IL-2 for preventing perturbations of the alloreactivity and phenotype of GMC.

Regulatory T-cell expansion and function do not account for the impaired alloreactivity of ex vivo-expanded T cells

CD3- and CD28-activated T cells expanded for 12 days ex vivo to produce suicide gene-modified T cells are hyporesponsive to alloantigens. To investigate whether this impaired alloreactivity is a result of preferential expansion of regulatory T (Treg) cells, we compared peripheral blood mononuclear cells (PBMC) activated with CD3 and CD28 antibodies co-immobilized on beads and expanded for 12 days with interleukin (IL)-2 (Co(CD3/CD28) cells) to the respective unactivated PBMC in terms of proliferation, cytokine production, and expression of Treg markers [cytotoxic T-lymphocyte antigen 4 (CTLA4), glucocorticoid-induced tumour necrosis factor receptor (GITR) and forkhead box P3 (FoxP3)] after allostimulation. Alloreactive cells were identified by carboxyfluoresceine succinimidyl ester staining dilution. Alloreactive cells in Co(CD3/CD28) cells had a lower proliferative response and a lower potential for IL-2 and interferon-gamma secretion than did those in PBMC, demonstrating a functional impairment of alloreactive cells during ex vivo expansion. Expression of Treg markers transiently increased during ex vivo expansion and was unaffected by depletion of CD25(+) cells (containing Treg cells) before ex vivo PBMC expansion. Such prior CD25(+) depletion did not restore the alloreactivity of Co(CD3/CD28) cells. After allostimulation, expression of Treg markers was restricted to proliferative (alloreactive) cells among PBMC or Co(CD3/CD28) cells. Lastly, CD4(+) CD25(+) cells purified from Co(CD3/CD28) cells lacked suppressive activity when used as a third party, in contrast to CD4(+) CD25(+) cells purified from PBMC. In conclusion, the impaired alloreactivity of T cells expanded ex vivo is not a result of preferential Treg cell expansion and/or enhanced suppressive Treg activity.