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Objective Vaccinated patients with cancer in follow-up studies showed a high seropositivity rate but impaired antibody titres and T cell responses following mRNA vaccine against COVID-19. Besides clinical characteristics and the type of anticancer treatment before vaccination, the identification of patients susceptible to non-response following vaccination using immunological markers is worth to be investigated.Methods and analysis All patients (n=138, solid cancers) were included in the CACOV-VAC Study comprising three cohorts ((neo)-adjuvant, metastatic and surveillance). Immune responses were assessed using, respectively, anti-receptor-binding domain (RBD) SARS-CoV-S-IgG assay and interferon-γ ELISpot assay 3 months following the prime vaccination dose. Immunophenotyping of T cells and immunosuppressive cells from peripheral blood was performed before the prime dose. The serological threshold 3563 AU/mL was used to discriminate non-responders or suboptimal responders versus responders.Results Most patients achieved seroconversion after receiving the two doses of vaccine (97.6%). The median serological level of anti-RBD SARS-CoV-S-IgG was equal to 3029 for patients at the metastatic stage. The patient’s age was the main demographic characteristic that influenced vaccine efficacy. Among the immunological parameters measured at baseline, lower TIGIT (T cell immunoreceptor with Ig and ITIM domains) expression on CD8 T cells was associated with a better vaccine immunogenicity both in terms of humoral and cellular immune responses.Conclusion Despite a high seroconversion rate, median serological levels of patients with cancer, particularly elderly patients, were below the threshold equal to 3563 AU/mL considered as a humoral correlate of protection against SARS-CoV-2. Our findings suggest that the inhibitory receptor TIGIT might be an interesting predictive biomarker of COVID-19 vaccine immunogenicity and beyond in an anticancer vaccine context.Trial registration number ClinicalTrials.gov Registry (NCT04836793).

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.

Background CAR-T cells immunotherapy is a breakthrough in the treatment of hematological malignancies such as acute lymphoblastic leukemia (ALL) and B-cell malignancies. However, CAR-T therapies face major hurdles such as the lack of tumor-specific antigen (TSA), and immunosuppressive tumor microenvironment sometimes caused by the tumorous expression of immune checkpoints (ICPs) such as HLA-G. Indeed, HLA-G is remarkable because it is both a potent ICP and a TSA. HLA-G tumor expression causes immune escape by impairing innate and adaptive immune responses and by inducing a suppressive microenvironment. Yet, to date, no immunotherapy targets it.Methods We have developed two anti-HLA-G third-generation CARs based on new anti-HLA-G monoclonal antibodies.Results Anti-HLA-G CAR-T cells were specific for immunosuppressive HLA-G isoforms. HLA-G-activated CAR-T cells polarized toward T helper 1, and became cytotoxic against HLA-G+ tumor cells. In vivo, anti-HLA-G CAR-T cells were able to control and eliminate HLA-G+ tumor cells. The interaction of tumor-HLA-G with interleukin (IL)T2-expressing T cells is known to result in effector T cell functional inhibition, but anti-HLA-G CAR-T cells were insensitive to this inhibition and still exerted their function even when expressing ILT2. Lastly, we show that anti-HLA-G CAR-T cells differentiated into long-term memory effector cells, and seemed not to lose function even after repeated stimulation by HLA-G-expressing tumor cells.Conclusion We report for the first time that HLA-G, which is both a TSA and an ICP, constitutes a valid target for CAR-T cell therapy to specifically target and eliminate both tumor cells and HLA-G+ suppressive cells.

Background Clinical benefit from programmed cell death 1 receptor (PD-1) inhibitors relies on reinvigoration of endogenous antitumor immunity. Nonetheless, robust immunological markers, based on circulating immune cell subsets associated with therapeutic efficacy are yet to be validated.Methods We isolated peripheral blood mononuclear cell from three independent cohorts of melanoma and Merkel cell carcinoma patients treated with PD-1 inhibitor, at baseline and longitudinally after therapy. Using multiparameter flow cytometry and cell sorting, we isolated four subsets of CD8+ T cells, based on PD-1 and TIGIT expression profiles. We performed phenotypic characterization, T cell receptor sequencing, targeted transcriptomic analysis and antitumor reactivity assays to thoroughly characterize each of these subsets.Results We documented that the frequency of circulating PD-1+TIGIT+ (DPOS) CD8+ T-cells after 1 month of anti-PD-1 therapy was associated with clinical response and overall survival. This DPOS T-cell population was enriched in highly activated T-cells, tumor-specific and emerging T-cell clonotypes and T lymphocytes overexpressing CXCR5, a key marker of the CD8 cytotoxic follicular T cell population. Additionally, transcriptomic profiling defined a specific gene signature for this population as well as the overexpression of specific pathways associated with the therapeutic response.Conclusions Our results provide a convincing rationale for monitoring this PD-1+TIGIT+ circulating population as an early cellular-based marker of therapeutic response to anti-PD-1 therapy.

Background The positive role of CD8+ tumor-infiltrating lymphocytes (TIL) in patients with colorectal cancer (CRC) has been well described but the prognostic value of CD4 T cell subsets remained to be investigated. In this study, we expanded TIL from surgically resected liver metastases of patients with CRC and characterized the phenotype and the prognostic value of expanded-CD4 T cells.Methods Liver metastases were surgically resected from 23 patients with CRC. Tumors were enzymatically digested and cultured in high dose of interleukin-2 for up to 5 weeks. T cell phenotype and reactivity of cultured-T cells were measured by flow cytometry and correlated with patients’ clinical outcomes.Results We successfully expanded 21 over 23 TIL from liver metastases of patients with CRC. Interestingly, we distinguished two subsets of expanded T cells based on T cell immunoglobulin mucin domain-containing protein 3 (TIM-3) expression. Medians fold expansion of expanded T cells after rapid expansion protocol was higher in CD3+TIM-3low cultures. In an attempt to investigate the correlation between the phenotype of expanded CD4 T cells and clinical outcomes, we observed on one hand that the level of Tregs in culture as well as the expression of both PD1 and TIM-3 by expanded T cells was not correlated to the clinical outcomes. Interestingly, on the other hand, cultures containing high levels of Th17 cells were associated with a poor prognosis (p=0.0007).Conclusions Our data confirmed the presence of Th17 cells in expanded T cells from liver metastases. Among CD4 T cell characteristics investigated, TIM-3 but not programmed cell death protein 1 predicted the expansion capacity of TIL while only the Th17 phenotype showed correlation with patients’ survival, suggesting a particular role of this T cell subset in CRC immune contexture.Trial registration number NCT02817178.