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TNFRF-14/HVEM is the ligand for BTLA and CD160 negative immune co-signaling molecules as well as viral proteins. Its expression is dysregulated with an overexpression in tumors and a connection with tumors of adverse prognosis. We developed C57BL/6 mouse models co-expressing human huBTLA and huHVEM as well as antagonistic monoclonal antibodies (mAbs) that completely prevent the interactions of HVEM with its ligands. Here, we show that the anti-HVEM18-10 mAb increases primary human αβ-T cells activity alone (CIS-activity) or in the presence of HVEM-expressing lung or colorectal cancer cells in vitro (TRANS-activity). Anti-HVEM18-10 synergizes with anti-PD-L1 mAb to activate T cells in the presence of PDL-1 positive tumors, but is sufficient to trigger T cell activation in the presence of PD-L1 negative cells. In order to better understand HVEM18-10 effect in vivo and especially disentangle its CIS and TRANS effects, we developed a knock-in (KI) mouse model expressing human BTLA (huBTLA+/+) and a KI mouse model expressing both human BTLA and human HVEM (huBTLA+/+/huHVEM+/+ (DKI)). In vivo pre-clinical experiments performed in both mouse models showed that HVEM18-10 treatment was efficient to decrease human HVEM+ tumor growth. In the DKI model, anti-HVEM 18-10 treatment induces a decrease of exhausted CD8+ T cells and regulatory T cells and an increase of Effector memory CD4+ T cells within the tumor. Interestingly, mice which completely rejected tumors (± 20%) did not develop tumors upon re-challenge in both settings, therefore showing a marked T cell-memory phenotype effect. Altogether, our preclinical models validate anti-HVEM18-10 as a promising therapeutic antibody to use in clinics as a monotherapy or in combination with existing immunotherapies (anti-PD1/anti-PDL-1/anti-CTLA-4). Citation Format: Laurent GORVEL, Clemence Demerle, Marielle Mello, Sonia Pastor, Clara Degos, Ana Zarubica, Fabien Angelis, Frederic Fiore, Jacques Nunes, Bernard Malissen, Laurent Greillier, Geoffrey Guittard, Herve Luche, Fabrice Barlesi, Daniel Olive. Anti-HVEM mAb therapy improves antitumoral immunity both in vitro and in vivo, in a novel transgenic mouse model expressing human HVEM and BTLA molecules challenged with HVEM expressing tumors. [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 5184.

Identification of major cellular players involved in progression of cancer is key to success of new immunotherapies. It is however a daunting challenge due to the complex interplay between tumor cells and the immune system. Component of innate and adaptive immunity may be directed to a pro- or anti-tumor function. In order to cope with the complexity of the tumor microenvironment (TME), it is necessary to use an experimental approach characterizing the heterogeneity of cell types, the evolution of their relative proportion and their fine-tuned functional specificity. This approach should lead to the identification of new cellular biomarkers characteristics of different stages of tumor cancer progression. To decipher the impact of immunotherapy treatments, cellular phenotyping of leukocytes infiltrating TME but also those present in peripheral organs is necessary. In order to increase our understanding in the precise mode of action of anti-PD1 treatment at the cellular level in sensitive and unsensitive syngeneic models, we investigated immunophenotypes and responses to immune checkpoint inhibitor (ICI) of several hallmark tumor models (MC38, CT26, B16F10, B16-OVA, RENCA, EMT6) in immunocompetent mouse models by flow and mass cytometry. We compared growth kinetics and profiled the immune cell composition of tumor microenvironment (TME), draining lymph node (dLN) and blood in order to establish immune-phenotypic cell signatures that correlates with treatment efficacy. Supervised, unsupervised and integrative data analysis arewere used to identify significant changes across different experimental settings. Our results indicate that each model possesses a unique tumor-immune infiltrate profile that can be modulated with immunotherapies. Overall, these studies provide an important resource of highly well-characterized syngeneic tumor model and highlight the importance of tumor immune landscape changes across models that will drive selection of the most appropriate model to test novel immunotherapeutic agents and enhance our translation of knowledge from syngeneic models to human tumors. Citation Format: Anais Joachim, Emilie Maturin, Marielle Mello, Lillia Hadjem, Magali Grange, Olivier Deas, Ana Zarubica, Bernard Malissen, Hervé Luche. Deep Immuno-profiling of syngeneic tumor mouse models for preclinical studies. [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 4630.

Preclinical tumor oncology research relies historically on the analysis of mouse or human tumor cell lines implanted onto severely immune-deficient mouse models carrying nude, SCID or Rag mutations on different genetical background (C57Bl/6N, BalbC, NMRI, CB17 or NOD). These lines harbor defects in several leukocyte lineages among which Tc, Bc and NKc might be affected. Humanized mice are emerging models that have been transplanted with human cells or tissues (and/or equipped with human transgenes). Currently, the most advanced strains are the nonobese diabetic, severe combined immunodeficiency (NOD-SCID) mouse with complete disruptions in the interleukin-2 (IL-2) common γ-chain (IL2R γ null) receptor (NSG) and BALB/c Rag2−/− IL2R γ null SirpaNOD mice (BRGS).1 Juvenile chimera NSG or BRGS are reconstituted with hematopoietic progenitor cell (HPCs) from human cord blood yielding robust engraftment of a human immune system (HIS).. Recent work showing the binding of human IgG4 to mouse FcgR receptor reducing clinical efficacy of therapeutic antibodies highlights the need to characterize extensively the residual immune system present in these models prior humanization in order to precisely evaluate immunotherapies. In other to fulfill this task, we genetically modified the mouse genome introducing mutations involved in Tc, Bc and NKc development. We then immuno-phenotyped over 20 lines of mouse mutants produced from the same animal house to minimize the impact of microbiota on innate immune cell populations. High content cytometry analysis of BM, spleen, thymus and peripheral blood was performed in a standardized manner. The resource obtained of these immunotypes was used to highlight similarities and differences among these lines across several genetical background. This work has shown instrumental in selecting the most appropriate model to use for humanization followed before tumor implantation. Citation Format: Hervé Luche, Lillia Hadjem, Marielle Mello, Priscilla Canavese, Fabien Angelis, Anais Joachim, Sylvie Bouilly, Frederic Guinut, Frederic Fiore, Bernard Malissen, Ana Zarubica, Erwan Corcuff. Systematic immune-profiling of immune-deficient mouse models: A rational to select ideal host for tumor implantation. [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 5190.