Biology subjects

Almeida-Santos, J.

Publications and source records attributed to Almeida-Santos, J..

5 recordsLinked to original sources

bioRxiv2022

Temporal profiling of CD4 T-cell activation and differentiation upon SARS-CoV-2 spike protein immunisation

CD4 T-cells require T-cell receptor (TCR) signalling for their activation and differentiation. Foxp3+ regulatory T-cells (Treg) are dependent on TCR signals for their differentiation and suppressive function. However, it is not fully known how TCR signalling controls the differentiation of polyclonal CD4 T-cells upon antigen recognition at the single-cell level in vivo. In this study, using Nr4a3-Tocky (Timer-of-cell-kinetics-and-activity), which analyses temporal changes of antigen-reactive T-cells following TCR signalling, we investigated T-cell response to Spike protein fragments (S1a, S1b, S2a, and S2b) upon immunisation. We show that S1a and S2a induced the differentiation of PD1hiCXCR5+ T follicular helper (Tfh) cells, which is related to CD4 T-cell immunogenicity. In contrast, S1b induced CD25hiGITRhiPD-1int Treg, which intermittently received TCR signalling. Using Foxp3-Tocky, which analyses Foxp3 transcriptional dynamics, the S1b-reactive Treg sustained Foxp3 transcription over time, which is a hallmark of activated Treg. Foxp3 fate-mapping showed that the S1b-reactive Treg were derived not from pre-existing thymic Treg, suggesting Foxp3 induction in non-Treg cells. Thus, the current study reveals temporally dynamic differentiation of CD4 T-cells and Treg upon immunisation in the polyclonal TCR repertoire.

immunology↗

bioRxiv2022

Single-cell level temporal profiling of tumour-reactive T cells under immune checkpoint blockade

The blockade of the immune checkpoints PD-1 and CTLA-4 enhances T cell response. However, it is largely unknown how antigen-reactive T cells regulate their checkpoint expression in vivo and whether and how the checkpoint blockade can change activation dynamics of tumour-reactive T cells. To address this, here we used Nr4a3-Timer-of-cell-kinetics-and-activity (Tocky), which allows analysis of temporal changes of activated T cells following TCR signalling in vivo. By analysing melanoma-bearing Nr4a3 Tocky mice, we elucidate hidden dynamics of tumour-reactive T cells in the steady-state. Checkpoint blockade depleted highly activated effector Treg, while promoting unique effector T cell populations, and thus differentially modulating activation of tumour-reactive T cell populations. Furthermore, multidimensional analysis and seamless analysis of Tocky and scRNA-seq revealed a full spectrum of T cell dynamics in response to tumour burden and treatment with checkpoint blockade. Lastly, we propose a rational design of combinatorial therapy to further enhance T cell activities.

immunology↗

bioRxiv2020

T-cell hyperactivation and paralysis in severe COVID-19 infection revealed by single-cell analysis

Severe COVID-19 patients can show respiratory failure, T-cell reduction, and cytokine release syndrome (CRS), which can be fatal in both young and aged patients and is a major concern of the pandemic. However, the pathogenetic mechanisms of CRS in COVID-19 are poorly understood. Here we show single cell-level mechanisms for T-cell dysregulation in severe SARS-CoV-2 infection, and thereby demonstrate the mechanisms underlying T-cell hyperactivation and paralysis in severe COVID-19 patients. By in silico sorting CD4+ T-cells from a single cell RNA-seq dataset, we found that CD4+ T-cells were highly activated and showed unique differentiation pathways in the lung of severe COVID-19 patients. Notably, those T-cells in severe COVID-19 patients highly expressed immunoregulatory receptors and CD25, whilst repressing the expression of the transcription factor FOXP3 and interestingly, both the differentiation of regulatory T-cells (Tregs) and Th17 was inhibited. Meanwhile, highly activated CD4+ T-cells express PD-1 alongside macrophages that express PD-1 ligands in severe patients, suggesting that PD-1-mediated immunoregulation was partially operating. Furthermore, we show that CD25+ hyperactivated T-cells differentiate into multiple helper T-cell lineages, showing multifaceted effector T-cells with Th1 and Th2 characteristics. Lastly, we show that CD4+ T-cells, particularly CD25-expressing hyperactivated T-cells, produce the protease Furin, which facilitates the viral entry of SARS-CoV-2. Collectively, CD4+ T-cells from severe COVID-19 patients are hyperactivated and FOXP3-mediated negative feedback mechanisms are impaired in the lung, while activated CD4+ T-cells continue to promote further viral infection through the production of Furin. Therefore, our study proposes a new model of T-cell hyperactivation and paralysis that drives pulmonary damage, systemic CRS and organ failure in severe COVID-19 patients.

immunology↗

bioRxiv2020

Interruption of thymic activity in adults improves responses to tumor immunotherapy

The thymus produces precursors of both effectors and regulatory T cells (Tconv and Treg, respectively) whose interactions prevents autoimmunity while allowing efficient protective immune responses. Tumors express a composite of self- and tumor-specific antigens and engage both Tconv and Treg cells. Along the aging process, the thymus involutes, and tumor incidence increases, a correlation proposed previously to be causal and the result of effector cell decline. In this work, we directly tested whether interruption of thymic activity in adult mice affects Foxp3 expressing Treg composition and function, and alters tumor immune surveillance. Young adult mice, on two different genetic backgrounds, were surgically thymectomized (TxT) and analyzed or challenged 2 months later. Cellular analysis revealed a 10-fold decrease in both Tconv and Treg numbers and a bias for activated cells. The persisting Treg displayed reduced stability of Foxp3 expression and, as a population, showed compromised return to homeostasis upon induced perturbations. We next tested the growth of three tumor models from different origin and presenting distinct degrees of spontaneous immunogenicity. In none of these conditions adult TxT facilitated tumor growth. Rather TxT enhanced the efficacy of anti-tumor immunotherapies targeting Treg and/or the checkpoint CTLA4, as evidenced by increased frequency of responder mice and decreased intra-tumoral Treg to CD8+IFN{gamma}+ cell ratio. Together, our findings point to a scenario where abrogation of thymic activities affects preferentially the regulatory over the ridding arm of the immune activities elicited by tumors, and argues that higher incidence of tumors with age cannot be solely attributed to thymic output decline.

immunology↗

bioRxiv2019

A weak Foxp3 hypomorph enhances spontaneous and therapeutic immune surveillance of cancer in mice

It is well established that therapeutic impairment of Foxp3+ regulatory T cells (Treg) in mice and humans favors immune rejection of solid tumors. Less explored are the genetic associations between Foxp3 allelic variants and tumor incidence, only sporadically reported in human studies. In this work, we tested and demonstrate that Foxp3fGFP, an allele classified as hypomorphic in Th1 inflammatory contexts but not affecting health at steady state, confers increased anti-tumor immunity. Our conclusions stem out of the analysis of three tumor models of different tissue origin, in two murine genetic backgrounds. When compared to wild type animals, mice carrying the Foxp3fGFP allele spontaneously delay, reduce or prevent primary tumor growth, decrease metastasis growth and potentiate the response to anti-CTLA4 monotherapy. These findings suggest that allelic variance at the Foxp3 locus may have significant impact on cancer incidence and/or the success of cancer-immunotherapies in humans.

cancer biology↗