Salmonella enterica Serovar Typhimurium Increases Functional PD-L1 Synergistically with Gamma Interferon in Intestinal Epithelial Cells via Salmonella Pathogenicity Island 2

Exploiting bacteria for cancer immunotherapy

Immunotherapy has revolutionized the treatment of cancer but continues to be constrained by limited response rates, acquired resistance, toxicities and high costs, which necessitates the development of new, innovative strategies. The discovery of a connection between the human microbiota and cancer dates back 4,000 years, when local infection was observed to result in tumour eradication in some individuals. However, the true oncological relevance of the intratumoural microbiota was not recognized until the turn of the twentieth century. The intratumoural microbiota can have pivotal roles in both the pathogenesis and treatment of cancer. In particular, intratumoural bacteria can either promote or inhibit cancer growth via remodelling of the tumour microenvironment. Over the past two decades, remarkable progress has been made preclinically in engineering bacteria as agents for cancer immunotherapy; some of these bacterial products have successfully reached the clinical stages of development. In this Review, we discuss the characteristics of intratumoural bacteria and their intricate interactions with the tumour microenvironment. We also describe the many strategies used to engineer bacteria for use in the treatment of cancer, summarizing contemporary data from completed and ongoing clinical trials. The work described herein highlights the potential of bacteria to transform the landscape of cancer therapy, bridging ancient wisdom with modern scientific innovation.

Upregulation of Immune checkpoint PD-L1 in Colon cancer cell lines and activation of T cells by Leuconostoc mesenteroides

Globally colorectal cancer ranks as the third most widespread disease and the third leading cause of cancer-associated mortality. Immunotherapy treatments like PD-L1 blockade have been used to inhibit the PD-L1 legend, which boosts the activity of cytotoxic T lymphocytes. Recently, studies suggest that some probiotics could potentially enhance the effectiveness of immunotherapy treatments for cancer patients. We found that in Caco-2 and HT-29 cells, the live Leuconostoc mesenteroides treatment resulted an increase in the PD-L1 expression and this treatment stimulated interferon-gamma (IFN-γ) production in Jurkat T-cells. Due to the well-established ability of IFN-γ to enhance PD-L1 expression, the combination of IFN-γ and L. mesenteroides was used in colon cancer cell lines and a resulting remarkable increase of over tenfold in PD-L1 expression was obtained. Interestingly, when L. mesenteroides and IFN-γ are present, the blockage of PD-L1 using PD-L1 antibodies not only improved the viability of Jurkat T-cells but also significantly boosted the levels of IFN-γ and IL-2, the T-cells activation marker cytokines. In addition to upregulating PD-L1, L. mesenteroides also activated Toll-like receptors (TLRs) and NOD-like receptors (NODs) pathways, specifically through TLR2 and NOD2, while also exerting a suppressive effect on autophagy in colon cancer cell lines. In conclusion, our findings demonstrate a significant upregulation of PD-L1 expression in colon cancer cells upon co-culturing with L. mesenteroides. Moreover, the presence of PD-L1 antibodies during co-culturing activates Jurkat T cells. The observed enhancement in PD-L1 expression may be attributed to the inhibition of the Autophagy pathway or activation of the hippo pathway. KEY POINTS: Co-culturing L. mesenteroides increases PD-L1 gene and protein transaction in colon cancer. L. mesenteroides existing enhances T cells viability and activity. GPCR41/42 is a possible link between L. mesenteroides, YAP-1 and PD-L1.

Lysates from the probiotic bacterium Streptococcus thermophilus enhances the survival of T cells and triggers programmed cell death in neuroblastoma cells

Neuroblastoma is the most common brain solid tumor in infancy. Despite the availability of numerous approaches like immunotherapy, surgery, chemotherapy, and radiotherapy, neuroblastoma frequently develops resistance and recurs. Immunotherapy is one of the most promising approaches and PD-L1 antibody blocking is the phenomena used to inhibit PD-1 receptors to increase and improve cytotoxic T cells toward cancer. Numerous studies underlined the critical role of probiotics on immune system development and modulation in addition to possible role in inducing apoptosis in cancer cells. In this study, a Streptococcus thermophilus strain, isolated from a local yogurt, was used as it is considered a potential probiotic due to its tolerance lower pH, bile acid, antibiotic suitability, and blood hemolysis. Our results showed that S. thermophilus lysates played as an immune checkpoint modulator at 25 µg/ml dose boosting PD-L1 transcripts and protein levels in SH-SY5Y neuroblastoma cell line. Interestingly, co-culture between SH-SY5Y and Jurkat T cells in the presence of blocking PD-L1 antibodies increased Jurkat T-cell viability compering to control without lysate. On the other hand, annexin-V/7-AAD, qPCR and western blot results showed that S. thermophilus lysates at 200 and 400 µg/ml decreased SH-SY5Y cell viability and increased apoptotic marker genes transcription and caspase-3 and caspase-9 protein expression.

Intracellular Fusobacterium nucleatum infection attenuates antitumor immunity in esophageal squamous cell carcinoma

Currently, the influence of the tumor microbiome on the effectiveness of immunotherapy remains largely unknown. Intratumoural Fusobacterium nucleatum (Fn) functions as an oncogenic bacterium and can promote tumor progression in esophageal squamous cell carcinoma (ESCC). Our previous study revealed that Fn is a facultative intracellular bacterium and that its virulence factor Fn-Dps facilitates the intracellular survival of Fn. In this study, we find that Fn DNA is enriched in the nonresponder (NR) group among ESCC patients receiving PD-1 inhibitor and that the serum antibody level of Fn is significantly higher in the NR group than in the responder (R) group. In addition, Fn infection has an opposite impact on the efficacy of αPD-L1 treatment in animals. Mechanistically, we confirm that Fn can inhibit the proliferation and cytokine secretion of T cells and that Fn-Dps binds to the PD-L1 gene promoter activating transcription factor-3 (ATF3) to transcriptionally upregulate PD-L1 expression. Our results suggest that it may be an important therapeutic strategy to eradicate intratumoral Fn infection before initiating ESCC immunotherapies.

Significance of PD1 Alternative Splicing in Celiac Disease as a Novel Source for Diagnostic and Therapeutic Target

Background

We have focused on the alteration of the PD-1/PD-L1 pathway in celiac disease and discussed the roles of the PD1 pathway in regulating the immune response. We explored the idea that the altered mRNA splicing process in key regulatory proteins could represent a novel source to identify diagnostic, prognostic, and therapeutic targets in celiac disease.

Methods

We characterized the PD1 mRNA variants' profile in CD patients and in response to gluten peptides' incubation after in vitro experiments. Total RNA from whole blood was isolated, and the coding region of the human PD-1 mRNA was amplified by cDNA PCR.

Results

PCR amplification of the human PD-1 coding sequence revealed an association between the over-expression of the sPD-1 protein and the PD-1Δex3 transcript in celiac disease. Thus, we have found three novel alternative spliced isoforms, two of which result in a truncated protein and the other isoform with a loss of 14 aa of exon 2 and complete exon 3 (Δ3) which could encode a new soluble form of PD1 (sPD-1).

Conclusions

Our study provides evidence that dietary gluten can modulate processes required for cell homeostasis through the splicing of pre-mRNAs encoding key regulatory proteins, which represents an adaptive mechanism in response to different nutritional conditions.

Perspectives on Oncolytic Salmonella in Cancer Immunotherapy-A Promising Strategy

Since the first reported spontaneous regression of tumors in patients with streptococcus infection, cancer biological therapy was born and it evolved into today's immunotherapy over the last century. Although the original strategy was unable to impart maximal therapeutic benefit at the beginning, it laid the foundations for the development of immune checkpoint blockade and CAR-T which are currently used for cancer treatment in the clinics. However, clinical applications have shown that current cancer immunotherapy can cause a series of adverse reactions and are captious for patients with preexisting autoimmune disorders. Salmonellae was first reported to exert antitumor effect in 1935. Until now, numerous studies have proved its potency as an antitumor agent in the near future. In this review, we summarize the currently available data on the antitumor effects of Salmonella, and discussed a possibility of integrating Salmonella into cancer immunotherapy to overcome current obstacles.

Escherichia coli K12 Upregulates Programmed Cell Death Ligand 1 (PD-L1) Expression in Gamma Interferon-Sensitized Intestinal Epithelial Cells via the NF-κB Pathway

Programmed cell death ligand-1 (PD-L1) is an immune checkpoint protein which is used by tumor cells for immune evasion. PD-L1 is upregulated in inflamed intestinal tissues. The intestinal tract is colonized by millions of bacteria, most of which are commensal bacterial species. We hypothesized that under inflammatory conditions, some commensal bacterial species contribute to increased PD-L1 expression in intestinal epithelium and examined this hypothesis. Human intestinal epithelial HT-29 cells with and without interferon (IFN)-γ sensitization were incubated with six strains of four enteric bacterial species. The mRNA and protein levels of PD-L1 in HT-29 cells were examined using quantitative real-time PCR and flow cytometry, respectively. The levels of interleukin (IL)-1β, IL-18, IL-6, IL-8, and tumor necrosis factor (TNF)-α secreted by HT-29 cells were measured using enzyme-linked immunosorbent assay. Apoptosis of HT-29 cells was measured using a caspase 3/7 assay. We found that Escherichia coli K12 significantly upregulated both PD-L1 mRNA and protein in IFN-γ-sensitized HT-29 cells. E. coli K12 induced the production of IL-8 in HT-29 cells, however, IL-8 did not affect HT-29 PD-L1 expression. Inhibition of the nuclear factor-kappa B pathway significantly reduced E. coli K12-induced PD-L1 expression in HT-29 cells. The other two E. coli strains and two enteric bacterial species did not significantly affect PD-L1 expression in HT-29 cells. Enterococcus faecalis significantly inhibited PD-L1 expression due to induction of cell death. Data from this study suggest that some gut bacterial species have the potential to affect immune function under inflammatory conditions via upregulating epithelial PD-L1 expression.

Differential expression of programmed death-1 and its ligand, programmed death ligand-1 in oral squamous cell carcinoma with and without oral submucous fibrosis

OBJECTIVE

The aim of our study was to investigate the expression of programmed death ligand-1 (PD-L1)/programmed death-1 (PD-1) between oral squamous cell carcinoma (OSCC) patients with and without oral submucous fibrosis (OSF), and its correlation with clinic-pathologic features and its prognostic value.

METHODS

PD-L1 and PD-1 expression was evaluated by immunohistochemical staining, double immunofluorescent staining and real-time PCR, and the correlation of PD-L1/PD-1 expression with clinical outcome was assessed.

RESULTS

The level of PD-L1 expression was significantly higher in OSCC with OSF than in OSCC without OSF (p = 0.006). Moreover, PD-L1 expression was strongly correlated with lymph node metastasis (p = 0.016), and advanced tumor stage (p = 0.030). Increased PD-L1 expression was positively correlated with the incidence of OSCC with OSF (p = 0.006, p = 0.008, respectively). PD-L1 expression was an independent marker of unfavorable prognosis (p = 0.035, p = 0.048, respectively). High PD-L1 expression had a significantly worse outcome in OSCC patients with OSF (p = 0.014). Double immunofluorescent staining showed that OSCC with OSF were more strongly expressed both PD-L1 and PD-1 than OSCC without OSF. Moreover, the expression of PD-L1 were upregulated in OSCC tissues than normal control (p = 0.0422), and both PD-L1 and PD-1 was significantly higher in OSCC with OSF than OSCC without OSF tissues (p = 0.0043 and, p = 0.0012, respectively).

CONCLUSIONS

The present study suggested that PD-L1 may be an unfavorable indicator for prognosis. PD-L1/PD-1 signaling might play an important role in the malignant transformation of OSF, and targeting PD-L1/PD-1 signaling may be a new therapeutic strategy for OSCC, especially in OSCC patients with OSF.

Fighting Persistence: How Chronic Infections with Mycobacterium tuberculosis Evade T Cell-Mediated Clearance and New Strategies To Defeat Them

Chronic bacterial infections are caused by pathogens that persist within their hosts and avoid clearance by the immune system. Treatment and/or detection of such pathogens is difficult, and the resulting pathologies are often deleterious or fatal. There is an urgent need to develop protective vaccines and host-directed therapies that synergize with antibiotics to prevent pathogen persistence and infection-associated pathologies. However, many persistent pathogens, such as Mycobacterium tuberculosis, actively target the very host pathways activated by vaccination. These immune evasion tactics blunt the effectiveness of immunization strategies and are impeding progress to control these infections throughout the world. Therefore, it is essential that M. tuberculosis immune evasion-related pathogen virulence strategies are considered to maximize the effectiveness of potential new treatments. In this review, we focus on how Mycobacterium tuberculosis infects antigen-presenting cells and evades effective immune clearance by the adaptive response through (i) manipulating antigen presentation, (ii) repressing T cell-activating costimulatory molecules, and (iii) inducing ligands that drive T cell exhaustion. In this context, we will examine the challenges that bacterial virulence strategies pose to developing new vaccines. We will then discuss new approaches that will help dissect M. tuberculosis immune evasion mechanisms and devise strategies to bypass them to promote long-term protection and prevent disease progression.

The well-evolved pathogen

Stan Falkow looked at the world with his eyes peering from the outer membrane of a gram-negative bacterium. It was a great vantage point from which to dream about the possible superpowers these organisms might have. He mused about these dreams with his trainees who sometimes found through rigorous scientific exploration that the superpowers really were there! Stan also realized that bacterial pathogenesis by definition was a two-way street, and that masterful understanding of bacterial virulence factors also required a masterful understanding of host cell processes against which the virulence factors were deployed. In my own scientific journey, I have sought to explore bacterial-host interactions that result in subtle alterations of the host's adaptive immune response. Here, as an example, I describe an interaction between Chlamydia trachomatis and host T cells that may contribute to the establishment of persistent infection.

Salmonella SPI-2 type III secretion system-dependent inhibition of antigen presentation and T cell function

Salmonella enterica serovars infect a broad range of mammalian hosts, including humans, causing both gastrointestinal and systemic diseases. Effective immune responses to Salmonella infections depend largely on CD4+ T cell activation by dendritic cells (DCs). Bacteria are internalised by intestinal DCs and respond by translocating effectors of the Salmonella pathogenicity island 2 (SPI-2) type III secretion system (T3SS) into host cells. In this review, we discuss processes that are hijacked by SPI-2 T3SS effectors and how this affects DC biology and the activation of T cell responses.