Induction of CD4+ regulatory T cells by stimulation with Staphylococcal Enterotoxin C2 through different signaling pathways

Streptococcal pyrogenic exotoxin a induces regulatory T cells via TNF-α-TNFR2 signaling

Bacterial superantigens are potent immune activators that trigger T cell proliferation and intensive release of cytokines, leading to toxic shock syndrome. Also, they impair host immune responses, increasing bacterial carriage and transmission. Several studies proposed that superantigens can induce regulatory T (Treg) cells, which may suppress immune responses against bacterial infection. However, the mechanism of Treg cell induction by superantigens is still elusive. We here demonstrated that streptococcal pyrogenic exotoxin A (SPEA) promoted human CD4+CD25+Foxp3+ T cell induction in a dose- and time-dependent manner and the induction required antigen-presenting cells (APCs). SPEA-induced CD4+CD25+ T cells could suppress allogeneic T cell proliferation and IL-2 secretion. Flow cytometric analyses demonstrated high expression of TNFR2 on SPEA-induced CD4+CD25+Foxp3+ T cells. Blocking the interaction between TNF-⍺ and TNFR2 reduced SPEA-induced CD25+Foxp3+ Treg cells. Our present study suggests a mechanism that the TNF-⍺ and TNFR2 axis is required for the induction of human CD4+CD25+Foxp3+ Treg cells by SPEA, which implicates a potential strategy to enhance the clearance of Group A streptococcus infection through reducing Treg cell induction by the inhibition of TNFR2 signaling.

T cell related osteoimmunology in fracture healing: Potential targets for augmenting bone regeneration

Last decade has witnessed increasing evidence which highlights the roles of immune cells in bone regeneration. Numerous immune cell types, including macrophages, T cells, and neutrophils are involved in fracture healing by orchestrating a series of events that modulate bone formation and remodeling. In this review, the role of T cell immunity in fracture healing has been summarized, and the modulatory effects of T cell immunity in inflammation, bone formation and remodeling have been highlighted. The review also summarizes the specific roles of different T cell subsets, including CD4+ T cells, CD8+ T cells, regulatory T cells, T helper 17 cells, and γδ T cells in modulating fracture healing. The current therapeutics targeting T cell immunity to enhance fracture healing have also been reviewed, aiming to provide insights from a translational standpoint. Overall, this work discusses recent advances and challenges in the interdisciplinary research field of T cell related osteoimmunology and its implications in fracture healing.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Delayed unions or non-unions of bone fractures remain a challenge in clinical practice. Developing a deep understanding of the roles of immune cells, including T cells, in fracture healing will facilitate the advancement of novel therapeutics of fracture nonunion. This review summarizes the current understanding of different T cell subsets involved in various phases of fracture healing, providing insights for targeting T cells as an alternative strategy to enhance bone regeneration.

Continuous Oral Administration of the Superantigen Staphylococcal Enterotoxin C2 Activates Intestinal Immunity and Modulates the Gut Microbiota in Mice

Staphylococcal Enterotoxin C2 (SEC2), a classical superantigen, is an antitumor immunotherapy agent. However, the injectable formulation of SEC2 limits its clinical application. Here, it is reported that oral administration of SEC2 activates the intestinal immune system and benefits intestinal health in a mouse model. These results indicate that intact SEC2 is detected in the stomach, intestine, and serum after oral administration. Continuous oral administration of SEC2 activates immune cells in gut-associated lymphoid tissues, promoting extensive differentiation and proliferation of CD4+ and CD8+ T cells and CD19+ B cells, leading to increased production of cytokines and secretory immunoglobulin A. SEC2 also enhances intestinal barrier function, as demonstrated by an increased villus length/crypt depth ratio and elevated expression of mucins and tight junction proteins. Additionally, SEC2 indirectly influenced gut microbiota, reinforcing potential probiotics and short-chain fatty acid synthesis. Enhanced differentiation of T and B cells in the spleen, coupled with elevated serum interleukin-2 levels, suggests systemic immune enhancement following oral administration of SEC2. These findings provide a scientific basis for the development of SEC2 as an oral immunostimulant for immune enhancement and anti-tumor immunotherapy.

Generation of Novel Tumour-Selective SEA Superantigen-Based Peptides with Improved Safety and Efficacy for Precision Cancer Immunotherapy

Bacterial superantigens are T-cell-stimulatory protein molecules which produce massive cytokines and cause human diseases. Due to their ability to activate up to 20% of resting T-cells, they have effectively killed T-cell-dependent tumours in vivo. However, the intrinsic toxicity of whole SAg molecules highlights the urgent need to develop more effective and safer SAg-based immunotherapy. With its unique approach, our study is a significant step towards developing safer tumour-targeted superantigen peptides (TTSP). We identified the T-cell activation function regions on the SEA superantigen and produced variants with minimal lethality, ensuring a safer approach to cancer treatment. This involved the creation of twenty 50-amino-acid-long overlapping peptides covering the full-length SEA superantigen (P1-P20). We then screened these peptides for T-cell activation, successfully isolating two peptides (P5 and P15) with significant T-cell activation. These selected peptides were used to design and synthesise tumour-targeted superantigen peptides, which were linked to a cancer-specific third loop (L3) of transforming growth factor-α (TGF-α), TGFαL3 from either a C' or N' terminal with an eight-amino-acid flexible linker in between. We also produced several P15 variants by changing single amino acids or by amino acid deletions. The novel molecules were then investigated for cytokine production and tumour-targeted killing. The findings from our previous study and the current work open up new avenues for peptide-based immunotherapy, particularly when combined with other immunotherapy techniques, thereby ensuring effective and safer cancer treatment.

Immunosuppressive Signaling Pathways as Targeted Cancer Therapies

Immune response has been shown to play an important role in defining patient prognosis and response to cancer treatment. Tumor-induced immunosuppression encouraged the recent development of new chemotherapeutic agents that assists in the augmentation of immune responses. Molecular mechanisms that tumors use to evade immunosurveillance are attributed to their ability to alter antigen processing/presentation pathways and the tumor microenvironment. Cancer cells take advantage of normal molecular and immunoregulatory machinery to survive and thrive. Cancer cells constantly adjust their genetic makeup using several mechanisms such as nucleotide excision repair as well as microsatellite and chromosomal instability, thus giving rise to new variants with reduced immunogenicity and the ability to continue to grow without restrictions. This review will focus on the central molecular signaling pathways involved in immunosuppressive cells and briefly discuss how cancer cells evade immunosurveillance by manipulating antigen processing cells and related proteins. Secondly, the review will discuss how these pathways can be utilized for the implementation of precision medicine and deciphering drug resistance.

Immunosuppressive Signaling Pathways as Targeted Cancer Therapies

Immune response has been shown to play an important role in defining patient prognosis and response to cancer treatment. Tumor-induced immunosuppression encouraged the recent development of new chemotherapeutic agents that assists in the augmentation of immune responses. Molecular mechanisms that tumors use to evade immunosurveillance are attributed to their ability to alter antigen processing/presentation pathways and the tumor microenvironment. Cancer cells take advantage of normal molecular and immunoregulatory machinery to survive and thrive. Cancer cells constantly adjust their genetic makeup using several mechanisms such as nucleotide excision repair as well as microsatellite and chromosomal instability, thus giving rise to new variants with reduced immunogenicity and the ability to continue to grow without restrictions. This review will focus on the central molecular signaling pathways involved in immunosuppressive cells and briefly discuss how cancer cells evade immunosurveillance by manipulating antigen processing cells and related proteins. Secondly, the review will discuss how these pathways can be utilized for the implementation of precision medicine and deciphering drug resistance.