Induction of Progenitor Exhausted Tissue-Resident Memory CD8+ T Cells Upon Salmonella Typhi Porins Adjuvant Immunization Correlates With Melanoma Control and Anti-PD-1 Immunotherapy Cooperation

Salmonella-based therapeutic strategies: improving tumor microenvironment and bringing new hope for cancer immunotherapy

Immunotherapy has revolutionized cancer treatment, yet its effectiveness is limited by immunosuppressive tumor microenvironment (TME). To overcome this challenge, innovative strategies to effectively modulate the TME are urgently needed. Over the past decades, bacteria-mediated cancer immunotherapy has recaptured increasing attention, driven by advances in synthetic biology, genetic engineering and our knowledge of host-pathogen interactions. Among various bacterial species, Salmonella has emerged as a leading candidate with significant therapeutic potential due to its broad-spectrum anti-tumor activity, tumor-targeting ability, immunomodulatory effects, oncolytic properties, genetic programmability, and engineering flexibility. These characteristics enable Salmonella to reshape the immunosuppressive TME, thereby enhancing anti-tumor efficacy. This review elaborates the regulatory effects of Salmonella on key components of the TME, the versatile engineering strategies for optimizing Salmonella's ability to modulate the TME, and recent advancements in combination cancer therapies. We also summarize current clinical applications and discuss challenges of developing safer and more effective Salmonella-based cancer immunotherapy.

TCellSI: A novel method for T cell state assessment and its applications in immune environment prediction

T cell is an indispensable component of the immune system and its multifaceted functions are shaped by the distinct T cell types and their various states. Although multiple computational models exist for predicting the abundance of diverse T cell types, tools for assessing their states to characterize their degree of resting, activation, and suppression are lacking. To address this gap, a robust and nuanced scoring tool called T cell state identifier (TCellSI) leveraging Mann-Whitney U statistics is established. The TCellSI methodology enables the evaluation of eight distinct T cell states-Quiescence, Regulating, Proliferation, Helper, Cytotoxicity, Progenitor exhaustion, Terminal exhaustion, and Senescence-from transcriptome data, providing T cell state scores (TCSS) for samples through specific marker gene sets and a compiled reference spectrum. Validated against sizeable pseudo-bulk and actual bulk RNA-seq data across a range of T cell types, TCellSI not only accurately characterizes T cell states but also surpasses existing well-discovered signatures in reflecting the nature of T cells. Significantly, the tool demonstrates predictive value in the immune environment, correlating T cell states with patient prognosis and responses to immunotherapy. For better utilization, the TCellSI is readily accessible through user-friendly R package and web server (https://guolab.wchscu.cn/TCellSI/). By offering insights into personalized cancer therapies, TCellSI has the potential to improve treatment outcomes and efficacy.

Potential mechanisms of cancer stem-like progenitor T-cell bio-behaviours

In situations involving continuous exposure to antigens, such as chronic infections or cancer, antigen-specific CD8+ T cells can become dysfunctional or exhausted. This change is marked by increased expression levels of inhibitory receptors (PD-1 and Tim-3). Stem-like progenitor exhausted (Tpex) cells, a subset of exhausted cells that express TCF-1 and are mainly found in the lymph nodes, demonstrate the ability to self-renew and exhibit a high rate of proliferation. Tpex cells can further differentiate into transitional intermediate exhausted (Tex-int) cells and terminally exhausted (Tex-term) cells. Alternatively, they can directly differentiate into Tex-term cells. Tpex cells are the predominant subset that respond to immune checkpoint inhibitors (ICI), making them a prime candidate for improving the efficacy of ICI therapy. This review article aimed to present the latest developments in the field of Tpex formation, expansion, and differentiation in the context of cancer, as well as their responses to ICIs in cancer immunotherapy. Consequently, it may be possible to develop novel treatments that exclusively target Tpex cells, thus improving overall treatment outcomes. KEY POINTS: Tpex cells are located in lymph nodes and TLS. Several pathways control the differentiation trajectories of Tpex cells, including epigenetic factors, transcription factors, cytokines, age, sex, etc.

TCF1-positive and TCF1-negative TRM CD8 T cell subsets and cDC1s orchestrate melanoma protection and immunotherapy response

BACKGROUND

Melanoma, the most lethal form of skin cancer, has undergone a transformative treatment shift with the advent of checkpoint blockade immunotherapy (CBI). Understanding the intricate network of immune cells infiltrating the tumor and orchestrating the control of melanoma cells and the response to CBI is currently of utmost importance. There is evidence underscoring the significance of tissue-resident memory (TRM) CD8 T cells and classic dendritic cell type 1 (cDC1) in cancer protection. Transcriptomic studies also support the existence of a TCF7+ (encoding TCF1) T cell as the most important for immunotherapy response, although uncertainty exists about whether there is a TCF1+TRM T cell due to evidence indicating TCF1 downregulation for tissue residency activation.

METHODS

We used multiplexed immunofluorescence and spectral flow cytometry to evaluate TRM CD8 T cells and cDC1 in two melanoma patient cohorts: one immunotherapy-naive and the other receiving immunotherapy. The first cohort was divided between patients free of disease or with metastasis 2 years postdiagnosis while the second between CBI responders and non-responders.

RESULTS

Our study identifies two CD8+TRM subsets, TCF1+ and TCF1-, correlating with melanoma protection. TCF1+TRM cells show heightened expression of IFN-γ and Ki67 while TCF1- TRM cells exhibit increased expression of cytotoxic molecules. In metastatic patients, TRM subsets undergo a shift in marker expression, with the TCF1- subset displaying increased expression of exhaustion markers. We observed a close spatial correlation between cDC1s and TRMs, with TCF1+TRM/cDC1 pairs enriched in the stroma and TCF1- TRM/cDC1 pairs in tumor areas. Notably, these TCF1- TRMs express cytotoxic molecules and are associated with apoptotic melanoma cells. Both TCF1+ and TCF1- TRM subsets, alongside cDC1, prove relevant to CBI response.

CONCLUSIONS

Our study supports the importance of TRM CD8 T cells and cDC1 in melanoma protection while also highlighting the existence of functionally distinctive TCF1+ and TCF1- TRM subsets, both crucial for melanoma control and CBI response.

The cholera toxin B subunit induces trained immunity in dendritic cells and promotes CD8 T cell antitumor immunity

Introduction

Innate immune training is a metabolic, functional, and epigenetic long-term reprogramming of innate cells triggered by different stimuli. This imprinting also reaches hematopoietic precursors in the bone marrow to sustain a memory-like phenotype. Dendritic cells (DCs) can exhibit memory-like responses, enhanced upon subsequent exposure to a pathogen; however, whether this imprinting is lineage and stimulus-restricted is still being determined. Nevertheless, the functional consequences of DCs training on the adaptive and protective immune response against non-infectious diseases remain unresolved.

Methods

We evaluated the effect of the nontoxic cholera B subunit (CTB), LPS and LTA in the induction of trained immunity in murine DCs revealed by TNFa and LDH expression, through confocal microscopy. Additionally, we obtained bone marrow DCs (BMDCs) from mice treated with CTB, LPS, and LTA and evaluated training features in DCs and their antigen-presenting cell capability using multiparametric cytometry. Finally, we design an experimental melanoma mouse model to demonstrate protection induced by CTB-trained DCs in vivo.

Results

CTB-trained DCs exhibit increased expression of TNFa, and metabolic reprogramming indicated by LDH expression. Moreover, CTB training has an imprint on DC precursors, increasing the number and antigen-presenting function in BMDCs. We found that training by CTB stimulates the recruitment of DC precursors and DCs infiltration at the skin and lymph nodes. Interestingly, training-induced by CTB promotes a highly co-stimulatory phenotype in tumor-infiltrating DCs (CD86+) and a heightened functionality of exhausted CD8 T cells (Ki67+, GZMB+), which were associated with a protective response against melanoma challenge in vivo.

Conclusion

Our work indicates that CTB can induce innate immune training on DCs, which turns into an efficient adaptive immune response in the melanoma model and might be a potential immunotherapeutic approach for tumor growth control.

Rab37 mediates trafficking and membrane presentation of PD-1 to sustain T cell exhaustion in lung cancer

BACKGROUND

Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor expressed on the surface of T cells. High expression of PD-1 leads to T-cell dysfunction in the tumor microenvironment (TME). However, the mechanism of intracellular trafficking and plasma membrane presentation of PD-1 remains unclear.

METHODS

Multiple databases of lung cancer patients were integratively analyzed to screen Rab proteins and potential immune-related signaling pathways. Imaging and various biochemical assays were performed in Jurkat T cells, splenocytes, and human peripheral blood mononuclear cells (PBMCs). Rab37 knockout mice and specimens of lung cancer patients were used to validate the concept.

RESULTS

Here, we identify novel mechanisms of intracellular trafficking and plasma membrane presentation of PD-1 mediated by Rab37 small GTPase to sustain T cell exhaustion, thereby leading to poor patient outcome. PD-1 colocalized with Rab37-specific vesicles of T cells in a GTP-dependent manner whereby Rab37 mediated dynamic trafficking and membrane presentation of PD-1. However, glycosylation mutant PD-1 delayed cargo recruitment to the Rab37 vesicles, thus stalling membrane presentation. Notably, T cell proliferation and activity were upregulated in tumor-infiltrating T cells from the tumor-bearing Rab37 knockout mice compared to those from wild type. Clinically, the multiplex immunofluorescence-immunohistochemical assay indicated that patients with high Rab37+/PD-1+/TIM3+/CD8+ tumor infiltrating T cell profile correlated with advanced tumor stages and poor overall survival. Moreover, human PBMCs from patients demonstrated high expression of Rab37, which positively correlated with elevated levels of PD-1+ and TIM3+ in CD8+ T cells exhibiting reduced tumoricidal activity.

CONCLUSIONS

Our results provide the first evidence that Rab37 small GTPase mediates trafficking and membrane presentation of PD-1 to sustain T cell exhaustion, and the tumor promoting function of Rab37/PD-1 axis in T cells of TME in lung cancer. The expression profile of Rab37high/PD-1high/TIM3high in tumor-infiltrating CD8+ T cells is a biomarker for poor prognosis in lung cancer patients.

The immune checkpoint protein PD-1: Its emerging regulatory role in memory T cells

Immunological memory helps the body rapidly develop immune defense when it re-encounters a bacterial or viral strain or encounters a similar mutation in healthy cells. The immune checkpoint molecule programmed cell death 1 (PD-1) influences memory T cell differentiation. However, the mechanism by which PD-1 regulates the development and maintenance of memory T cells and its impact on memory T cells function remain unclear. In this review, we first discuss the structure and function of PD-1 and then summarize the roles of PD-1 as a marker of tumor memory T cells and in tumor immunotherapy. We also discuss the potential mechanisms through which PD-1 regulates memory T cells development and maintenance during immune diseases such as viral infection-mediated diseases, psoriasis, and rheumatoid arthritis, and list the effects of PD-1 on memory T cells in pregnancy and their function in maternal-fetal immune balance. A complete understanding of how PD-1 influences the development, maintenance, and function of memory T cells will provide new insights into the prevention and treatment of immune-related diseases.

Bacteria-based immunotherapy for cancer: a systematic review of preclinical studies

Immunotherapy has been emerging as a powerful strategy for cancer management. Recently, accumulating evidence has demonstrated that bacteria-based immunotherapy including naive bacteria, bacterial components, and bacterial derivatives, can modulate immune response via various cellular and molecular pathways. The key mechanisms of bacterial antitumor immunity include inducing immune cells to kill tumor cells directly or reverse the immunosuppressive microenvironment. Currently, bacterial antigens synthesized as vaccine candidates by bioengineering technology are novel antitumor immunotherapy. Especially the combination therapy of bacterial vaccine with conventional therapies may further achieve enhanced therapeutic benefits against cancers. However, the clinical translation of bacteria-based immunotherapy is limited for biosafety concerns and non-uniform production standards. In this review, we aim to summarize immunotherapy strategies based on advanced bacterial therapeutics and discuss their potential for cancer management, we will also propose approaches for optimizing bacteria-based immunotherapy for facilitating clinical translation.

Lumican is a potential predictor on the efficacy of concurrent chemoradiotherapy in cervical squamous cell carcinoma

Purpose

To identify new novel biomarkers for predicting the efficacy of concurrent chemoradiotherapy(CCRT) in cervical squamous cell carcinoma(CESC).

Methods

Gene expression datasets GSE56363, GSE5787, and GSE168009 were analyzed to identify candidate genes to predict the efficacy of CCRT in CESC. Single-cell RNA sequencing (scRNA-seq) data from GSE168652 and CESC patients in The Cancer Genome Atlas(TCGA) were systematically analyzed to explore possible molecular mechanisms. Kaplan-Meier evaluated the correlation between LUM (Lumican) and prognostic significance. The expression of LUM protein in biopsy tissues before CCRT was detected by immunohistochemistry in 15 CESC patients.

Results

LUM mRNA levels were significantly upregulated in nonresponders of CESC.patients receiving CCRT and positively correlated with poor therapeutic effect. Furthermore, high expression of LUM influenced the immune microenvironment in CESC patient-derived organoids treated with CCRT. LUM overexpression in CESC cells induced resistance to CCRT, potentially via immune landscape modulation. Gene Set Enrichment Analysis (GSEA) revealed that possible mechanisms underlying resistance to CCRT might involve the PARs and IL1 signaling pathway affecting the immune landscape.

Conclusions

High LUM expression is correlated with poor efficacy in CESC patients receiving CCRT, possibly through the PARs and IL1 signaling pathway affecting the immune landscape.

A CD8+ T cell-associated immune gene panel for prediction of the prognosis and immunotherapeutic effect of melanoma

Background

Skin cutaneous melanoma (SKCM) is the most frequently encountered tumor of the skin. Immunotherapy has opened a new horizon in melanoma treatment. We aimed to construct a CD8⁺ T cell-associated immune gene prognostic model (CDIGPM) for SKCM and unravel the immunologic features and the benefits of immunotherapy in CDIGPM-defined SKCM groups.

Method

Single-cell SKCM transcriptomes were utilized in conjunction with immune genes for the screening of CD8⁺ T cell-associated immune genes (CDIGs) for succeeding assessment. Thereafter, through protein-protein interaction (PPI) networks analysis, univariate COX analysis, and multivariate Cox analysis, six genes (MX1, RSAD2, IRF2, GBP2, IFITM1, and OAS2) were identified to construct a CDIGPM. We detected cell proliferation of SKCM cells transfected with IRF2 siRNA. Then, we analyzed the immunologic features and the benefits of immunotherapy in CDIGPM-defined groups.

Results

The overall survival (OS) was much better in low-CDIGPM group versus high CDIGPM group in TCGA dataset and GSE65904 dataset. On the whole, the results unfolded that a low CDIGPM showed relevance to immune response-correlated pathways, high expressions of CTLA4 and PD-L1, a high infiltration rate of CD8⁺ T cells, and more benefits from immunotherapy.

Conclusion

CDIGPM is an good model to predict the prognosis, the potential immune escape from immunotherapy for SKCM, and define immunologic and molecular features.

Mining the Immunopeptidome for Antigenic Peptides in Cancer

Although harnessing the immune system for cancer therapy has shown success, response to immunotherapy has been limited. The immunopeptidome of cancer cells presents an opportunity to discover novel antigens for immunotherapy applications. These neoantigens bind to MHC class I and class II molecules. Remarkably, the immunopeptidome encompasses protein post-translation modifications (PTMs) that may not be evident from genome or transcriptome profiling. A case in point is citrullination, which has been demonstrated to induce a strong immune response. In this review, we cover how the immunopeptidome, with a special focus on PTMs, can be utilized to identify cancer-specific antigens for immunotherapeutic applications.

Control of Dendritic Cell Function Within the Tumour Microenvironment

The tumour microenvironment (TME) presents a major block to anti-tumour immune responses and to effective cancer immunotherapy. The inflammatory mediators such as cytokines, chemokines, growth factors and prostaglandins generated in the TME alter the phenotype and function of dendritic cells (DCs) that are critical for a successful adaptive immune response against the growing tumour. In this mini review we discuss how tumour cells and the surrounding stroma modulate DC maturation and trafficking to impact T cell function. Fibroblastic stroma and the associated extracellular matrix around tumours can also provide physical restrictions to infiltrating DCs and other leukocytes. We discuss interactions between the inflammatory TME and infiltrating immune cell function, exploring how the inflammatory TME affects generation of T cell-driven anti-tumour immunity. We discuss the open question of the relative importance of antigen-presentation site; locally within the TME versus tumour-draining lymph nodes. Addressing these questions will potentially increase immune surveillance and enhance anti-tumour immunity.

CD4+ and CD8+ Circulating Memory T Cells Are Crucial in the Protection Induced by Vaccination with Salmonella Typhi Porins

Salmonella enterica serovar Typhi (S. Typhi) porins, OmpC and OmpF, are potent inducers of the immune response against S. Typhi in mice and humans. Vaccination with porins induces the protection against 500 LD₅₀ of S. Typhi, life-lasting bactericidal antibodies and effector T cell responses in mice; however, the nature of the memory T cell compartment and its contribution to protection remains unknown. In this work, we firstly observed that vaccination with porins induces in situ (skin) CD4+ and CD8+ T cell responses. Analysis of the porin-specific functional responses of skin CD4+ and CD8+ T cells showed IFN-gamma- and IL-17-producing cells in both T cell populations. The memory phenotype of porin-specific T cells indicated the presence of resident and effector memory phenotypes in the skin, and a central memory phenotype in the skin-draining lymph node. In addition, we demonstrated that vaccination with porins via skin reduces the bacterial burden following challenge. Finally, evaluating the role of the circulating T cell memory population in protection, we showed that circulating memory CD4+ and CD8+ T cells are crucial in porin-mediated protection against S. Typhi. Overall, this study highlights the importance of inducing circulating memory T cell responses in order to achieve the optimal protection provided by porins, showing a mechanism that could be sought in the rational development of vaccines.