Epigenetic Modification Mediates the Increase of LAG-3+ T Cells in Chronic Osteomyelitis

Osteomyelitis is associated with increased anti-inflammatory response and immune exhaustion

Introduction

Osteomyelitis (OMS) is a bone infection causing bone pain and severe complications. A balanced immune response is critical to eradicate infection without harming the host, yet pathogens manipulate immunity to establish a chronic infection. Understanding OMS-driven inflammation is essential for disease management, but comprehensive data on immune profiles and immune cell activation during OMS are lacking.

Methods

Using high-dimensional flow cytometry, we investigated the detailed innate and adaptive systemic immune cell populations in OMS and age- and sex-matched controls.

Results

Our study revealed that OMS is associated with increased levels of immune regulatory cells, namely T regulatory cells, B regulatory cells, and T follicular regulatory cells. In addition, the expression of immune activation markers HLA-DR and CD86 was decreased in OMS, while the expression of immune exhaustion markers TIM-3, PD-1, PD-L1, and VISTA was increased. Members of the T follicular helper (Tfh) cell family as well as classical and typical memory B cells were significantly increased in OMS individuals. We also found a strong correlation between memory B cells and Tfh cells.

Discussion

We conclude that OMS skews the host immune system towards the immunomodulatory arm and that the Tfh memory B cell axis is evident in OMS. Therefore, immune-directed therapies may be a promising alternative for eradication and recurrence of infection in OMS, particularly in individuals and areas where antibiotic resistance is a major concern.

Epigenetic Perspective of Immunotherapy for Cancers

Immunotherapy has brought new hope for cancer patients in recent times. However, despite the promising success of immunotherapy, there is still a need to address major challenges including heterogeneity in response among patients, the reoccurrence of the disease, and iRAEs (immune-related adverse effects). The first critical step towards solving these issues is understanding the epigenomic events that play a significant role in the regulation of specific biomolecules in the context of the immune population present in the tumor immune microenvironment (TIME) during various treatments and responses. A prominent advantage of this step is that it would enable researchers to harness the reversibility of epigenetic modifications for their druggability. Therefore, we reviewed the crucial studies in which varying epigenomic events were captured with immuno-oncology set-ups. Finally, we discuss the therapeutic possibilities of their utilization for the betterment of immunotherapy in terms of diagnosis, progression, and cure for cancer patients.

Metatranscriptome sequencing identifies Escherichia are major contributors to pathogenic functions and biofilm formation in diabetes related foot osteomyelitis

Osteomyelitis in the feet of persons with diabetes is clinically challenging and is associated with high rates of amputation. In this study RNA-sequencing was employed to explore microbial metatranscriptomes with a view to understand the relative activity and functions of the pathogen/s responsible for diabetes foot osteomyelitis (DFO). We obtained 25 intraoperative bone specimens from persons with confirmed DFO, observing that Escherichia spp. (7%), Streptomyces spp. (7%), Staphylococcus spp. (6%), Klebsiella spp. (5%) and Proteus spp. (5%) are the most active taxa on average. Data was then subset to examine functions associated with pathogenesis (virulence and toxins), biofilm formation and antimicrobial/multi-drug resistance. Analysis revealed Escherichia spp. are the most active taxa relative to pathogenic functions with K06218 (mRNA interferase relE), K03699 (membrane damaging toxin tlyC) and K03980 (putative peptidoglycan lipid II flippase murJ), K01114 (membrane damaging toxin plc) and K19168 (toxin cptA) being the most prevalent pathogenic associated transcripts. The most abundant transcripts associated with biofilm pathways included components of the biofilm EPS matrix including glycogen synthesis, cellulose synthesis, colonic acid synthesis and flagella synthesis. We further observed enrichment of a key enzyme involved in the biosynthesis of L-rhamnose (K01710 -dTDP-glucose 4,6-dehydratase rfbB, rmlB, rffG) which was present in all but four patients with DFO.

Update on lymphocyte-activation gene 3 (LAG-3) in cancers: from biological properties to clinical applications

Immunotherapy that targets checkpoints, especially programmed cell death protein 1 and programmed cell death ligand 1, has revolutionized cancer therapy regimens. The overall response rate to mono-immunotherapy, however, is limited, emphasizing the need to potentiate the efficacy of these regimens. The functions of immune cells are modulated by multiple stimulatory and inhibitory molecules, including lymphocyte activation gene 3 (LAG-3). LAG-3 is co-expressed together with other inhibitory checkpoints and plays key roles in immune suppression. Increasing evidence, particularly in the last 5 years, has shown the potential of LAG-3 blockade in anti-tumor immunity. This review provides an update on the biological properties and clinical applications of LAG-3 in cancers.

Immunoregulatory role of IL-2/STAT5/CD4+CD25+Foxp3 Treg pathway in the pathogenesis of chronic osteomyelitis

Background

This study aimed to investigate immunoregulatory role of IL-2/STAT5/CD4+CD25+Foxp3 Treg pathway in pathogenesis of chronic osteomyelitis (COM).

Methods

Sprague-Dawley (SD) rats were injected with Staphylococcus aureus to establish COM model. 4 weeks later, the lesioned bones were collected and subjected to HE staining for examination of inflammatory infiltration. Enzyme-linked immunosorbent assay (ELISA) was employed to detect IL-2 expression in peripheral blood; flow cytometry was performed to detect CD25+CD4+Foxp3 Treg cells in peripheral blood. The mRNA expression of Foxp3 and CTLA-4 was detected by RT-PCR and the protein expression of STAT5 and p-STAT5 was detected by Western Blotting in CD25+CD4+Foxp3 Treg cells.

Results

In COM group, the periosteal thickening was observed in femur, and there were a large number of inflammatory cells in medullary cavity, accompanied by bone destruction. At 1, 2 and 4 weeks, IL-2 expression significantly increased, the proportion of CD4+CD25+FoxP3 Treg cells in peripheral monocytes markedly increased, the mRNA expression of Foxp3 and CTLA-4 and p-STAT5 protein expression increased dramatically in Treg cells as compared to control group (P<0.001).

Conclusions

IL-2/STAT5/CD4+CD25+Foxp3 Treg pathway may be involved in the pathogenesis of COM, and excessive immunosuppression may lead to persistent infectious inflammation, which may become a key target for future treatment of COM.

Chronic Implant-Related Bone Infections-Can Immune Modulation be a Therapeutic Strategy?

Chronic implant-related bone infections are a major problem in orthopedic and trauma-related surgery with severe consequences for the affected patients. As antibiotic resistance increases in general and because most antibiotics have poor effectiveness against biofilm-embedded bacteria in particular, there is a need for alternative and innovative treatment approaches. Recently, the immune system has moved into focus as the key player in infection defense and bone homeostasis, and the targeted modulation of the host response is becoming an emerging field of interest. The aim of this review was to summarize the current knowledge of impaired endogenous defense mechanisms that are unable to prevent chronicity of bone infections associated with a prosthetic or osteosynthetic device. The presence of foreign material adversely affects the immune system by generating a local immune-compromised environment where spontaneous clearance of planktonic bacteria does not take place. Furthermore, the surface structure of the implant facilitates the transition of bacteria from the planktonic to the biofilm stage. Biofilm formation on the implant surface is closely linked to the development of a chronic infection, and a misled adaption of the immune system makes it impossible to effectively eliminate biofilm infections. The interaction between the immune system and bone cells, especially osteoclasts, is extensively studied in the field of osteoimmunology and this crosstalk further aggravates the course of bone infection by shifting bone homeostasis in favor of bone resorption. T cells play a major role in various chronic diseases and in this review a special focus was therefore set on what is known about an ineffective T cell response. Myeloid-derived suppressor cells (MDSCs), anti-inflammatory macrophages, regulatory T cells (T_regs) as well as osteoclasts all suppress immune defense mechanisms and negatively regulate T cell-mediated immunity. Thus, these cells are considered to be potential targets for immune therapy. The success of immune checkpoint inhibition in cancer treatment encourages the transfer of such immunological approaches into treatment strategies of other chronic diseases. Here, we discuss whether immune modulation can be a therapeutic tool for the treatment of chronic implant-related bone infections.