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γδ-T cells promote IFN-γ–dependent Plasmodium pathogenesis upon liver-stage infection

Publication . Ribot, Julie; Neres, Rita; Zuzarte-Luis, Vanessa; Gomes, Anita Q.; Mancio-Silva, Liliana; Mensurado, Sofia; Neves, Daniel; Monteiro Dos Santos, Miguel; Carvalho, Tânia; Landry, Jonathan J. M.; A. Rolo, Eva; Malik, Ankita; Silva, Daniel Varón; Mota, Maria M.; Silva-Santos, Bruno; Pamplona, Ana

Cerebral malaria (CM) is a major cause of death due to Plasmodium infection. Both parasite and host factors contribute to the onset of CM, but the precise cellular and molecular mechanisms that contribute to its pathogenesis remain poorly characterized. Unlike conventional αβ-T cells, previous studies on murine γδ-T cells failed to identify a nonredundant role for this T cell subset in experimental cerebral malaria (ECM). Here we show that mice lacking γδ-T cells are resistant to ECM when infected with Plasmodium berghei ANKA sporozoites, the liver-infective form of the parasite and the natural route of infection, in contrast with their susceptible phenotype if challenged with P. berghei ANKA-infected red blood cells that bypass the liver stage of infection. Strikingly, the presence of γδ-T cells enhanced the expression of Plasmodium immunogenic factors and exacerbated subsequent systemic and brain-infiltrating inflammatory αβ-T cell responses. These phenomena were dependent on the proinflammatory cytokine IFN-γ, which was required during liver stage for modulation of the parasite transcriptome, as well as for downstream immune-mediated pathology. Our work reveals an unanticipated critical role of γδ-T cells in the development of ECM upon Plasmodium liver-stage infection.

2019Journal article

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Regulation of T cell fitness and functions in tumour responses

Publication . Mensurado, Sofia; Serre, Karine Marie; Santos, Bruno Miguel de Carvalho e Silva

The immune system, mainly through the action of T cells (and NK), patrols nascent tumours and controls their progression, in a process called immunosurveillance. However, tumours still develop. The failure of tumour control by the immune system is mediated by several escape mechanisms, and the purpose of immunotherapy is to reverse that escape. Substantial advances had been made in this field with the discovery and therapeutic manipulation of immune checkpoints, which are negative regulators of T cell responses. Their discovery was so important that the two pioneer investigators, Tasuku Honjo and James Allison, received the Nobel Prize of Physiology or Medicine in 2018. Clinical blockade of these pathways has shifted the paradigm in the treatment of several types of cancer; however, the efficacy of this strategy is limited to some types of tumours and to an overall minority of patients. This limited efficacy highlights the need of unravelling new mechanisms responsible for T cell regulation in the tumour microenvironment (TME), which we undertook in this thesis. First, we studied the negative regulation of IL-17-producing γδ (γδ17) T cells, which we and others had previously shown to play paradoxical tumour-promoting roles. We used two murine cancer models consisting in the injection of a melanoma (B16) or a hepatoma (Hepa 1-6) cell line, in the peritoneal cavity or liver, respectively. These anatomic locations are favourable to the induction of γδ17 T cell responses. However, to our surprise, these cells did not expand upon tumour challenge, in comparison to tumour-free controls. Concomitantly to the absence of a γδ17 T cell response, we observed a striking accumulation of neutrophils, leading us to hypothesize that neutrophils could suppress γδ17 T cell responses. Genetic approaches, depletion strategies and in vitro studies collectively demonstrated that tumour-associated neutrophils inhibited γδ17 T cell proliferation, through the production of reactive oxygen species (ROS). Interestingly, γδ17 T cells expressed low levels of antioxidants, particularly glutathione, which rendered them particularly susceptible to oxidative stress. In sum, we unraveled a new mechanism responsible for the regulation of a critical pro-tumoural T cell subset in the tumour microenvironment. On the other hand, we also investigated mechanisms of positive regulation of T cells, towards the potentiation of their anti-tumour functions. Given that the essential amino acid, methionine, had previously been shown to be required for T cell proliferation and effector function, we tested the effect of its supplementation in tumour-bearing mice. We used an orthotopic murine triple-negative breast cancer (TNBC) model consisting in the injection of the E0771 cell line in the mammary fat pad. We found that methionine supplementation, while not having a direct effect on tumour progression, potentiated the efficacy of suboptimal anti-PD-1 treatment. The combination of anti-PD-1 with methionine led to an increased infiltration of IFNγ-producing γδ (γδIFNγ) T cells and cytotoxic CD8+ T cells in the tumour bed. Both these subsets were required for the increased efficacy of the combination therapy, with γδ T cells seemingly acting upstream of CD8+ T cells, and the latter becoming more effective tumour killers upon combined therapy. While the molecular mediators underlying the increased T cell infiltration and effector function are still to be determined, our data reveal a new avenue to potentiate the anti-tumour function of γδ and CD8+ T cells, through the combination of anti-PD-1 and methionine. In conclusion, the work presented in this thesis unravels two new mechanisms of T cell regulation in tumours: one that inhibits pro-tumoural T cells and another that potentiates anti-tumour T cell responses. We hope our findings may contribute to the (re)design of more efficacious cancer immunotherapy strategies.

2020-06Doctoral thesis

Open access

γδ T cells: pleiotropic immune effectors with therapeutic potential in cancer

Publication . Silva-Santos, Bruno; Mensurado, Sofia; Coffelt, Seth B.

The potential of cancer immunotherapy relies on the mobilization of immune cells capable of producing antitumour cytokines and effectively killing tumour cells. These are major attributes of γδ T cells, a lymphoid lineage that is often underestimated despite its major role in tumour immune surveillance, which has been established in a variety of preclinical cancer models. This situation notwithstanding, in particular instances the tumour microenvironment seemingly mobilizes γδ T cells with immunosuppressive or tumour-promoting functions, thus emphasizing the importance of regulating γδ T cell responses in order to realize their translation into effective cancer immunotherapies. In this Review we outline both seminal work and recent advances in our understanding of how γδ T cells participate in tumour immunity and how their functions are regulated in experimental models of cancer. We also discuss the current strategies aimed at maximizing the therapeutic potential of human γδ T cells, on the eve of their exploration in cancer clinical trials that may position them as key players in cancer immunotherapy.

2019Journal article

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Primary tumors limit metastasis formation through induction of IL15-mediated cross-talk between patrolling monocytes and NK cells

Publication . Kubo, Hiroshi; Mensurado, Sofia; Gonçalves-Sousa, Natacha; Serre, Karine; Silva-Santos, Bruno

Metastases are responsible for the vast majority of cancer-related deaths. Although tumor cells can become invasive early during cancer progression, metastases formation typically occurs as a late event. How the immune response to primary tumors may dictate this outcome remains poorly understood, which hampers our capacity to manipulate it therapeutically. Here, we used a two-step experimental model, based on the highly aggressive B16F10 melanoma, that temporally segregates the establishment of primary tumors (subcutaneously) and the formation of lung metastases (from intravenous injection). This allowed us to identify a protective innate immune response induced by primary tumors that inhibits experimental metastasis. We found that in the presence of primary tumors, increased numbers of natural killer (NK) cells with enhanced IFNγ, granzyme B, and perforin production were recruited to the lung upon metastasis induction. These changes were mirrored by a local accumulation of patrolling monocytes and macrophages with high expression of MHC class II and NOS2. Critically, the protective effect on metastasis was lost upon patrolling monocyte or NK cell depletion, IL15 neutralization, or IFNγ ablation. The combined analysis of these approaches allowed us to establish a hierarchy in which patrolling monocytes, making IL15 in response to primary tumors, activate NK cells and IFNγ production that then inhibit lung metastasis formation. This work identifies an innate cell network and the molecular determinants responsible for "metastasis immunosurveillance," providing support for using the key molecular mediator, IL15, to improve immunotherapeutic outcomes.

2017Journal article

Restricted access