Conditioning of naive CD4(+) T cells for enhanced peripheral Foxp3 induction by nonspecific bystander inflammation.

Inflammation induced during infection can both promote and suppress immunity. This contradiction suggests that inflammatory cytokines affect the immune system in a context-dependent manner. Here we show that nonspecific bystander inflammation conditions naive CD4(+) T cells for enhanced peripheral Foxp3 induction and reduced effector differentiation. This results in inhibition of immune responses in vivo via a Foxp3-dependent effect on antigen-specific naive CD4(+) T cell precursors. Such conditioning may have evolved to allow immunity to infection while limiting subsequent autoimmunity caused by release of self-antigens in the wake of infection. Furthermore, this phenomenon suggests a mechanistic explanation for the idea that early tuning of the immune system by infection affects the long-term quality of immune regulation.

The class A scavenger receptor, macrophage receptor with collagenous structure, is the major phagocytic receptor for Clostridium sordellii expressed by human decidual macrophages.

Clostridium sordellii is an emerging pathogen associated with highly lethal female reproductive tract infections following childbirth, abortion, or cervical instrumentation. Gaps in our understanding of the pathogenesis of C. sordellii infections present major challenges to the development of better preventive and therapeutic strategies against this problem. We sought to determine the mechanisms whereby uterine decidual macrophages phagocytose this bacterium and tested the hypothesis that human decidual macrophages use class A scavenger receptors to internalize unopsonized C. sordellii. In vitro phagocytosis assays with human decidual macrophages incubated with pharmacological inhibitors of class A scavenger receptors (fucoidan, polyinosinic acid, and dextran sulfate) revealed a role for these receptors in C. sordellii phagocytosis. Soluble macrophage receptor with collagenous structure (MARCO) receptor prevented C. sordellii internalization, suggesting that MARCO is an important class A scavenger receptor in decidual macrophage phagocytosis of this microbe. Peritoneal macrophages from MARCO-deficient mice, but not wild-type or scavenger receptor AI/II-deficient mice, showed impaired C. sordellii phagocytosis. MARCO-null mice were more susceptible to death from C. sordellii uterine infection than wild-type mice and exhibited impaired clearance of this bacterium from the infected uterus. Thus, MARCO is an important phagocytic receptor used by human and mouse macrophages to clear C. sordellii from the infected uterus.

TAK-676: A Novel Stimulator of Interferon Genes (STING) Agonist Promoting Durable IFN-dependent Antitumor Immunity in Preclinical Studies.

Oncology therapies targeting the immune system have improved patient outcomes across a wide range of tumor types, but resistance due to an inadequate T-cell response in a suppressive tumor microenvironment (TME) remains a significant problem. New therapies that activate an innate immune response and relieve this suppression may be beneficial to overcome this hurdle. TAK-676 is a synthetic novel stimulator of interferon genes (STING) agonist designed for intravenous administration. Here we demonstrate that TAK-676 dose-dependently triggers activation of the STING signaling pathway and activation of type I interferons. Furthermore, we show that TAK-676 is a highly potent modulator of both the innate and adaptive immune system and that it promotes the activation of dendritic cells, natural killer cells, and T cells in preclinical models. In syngeneic murine tumor models in vivo, TAK-676 induces dose-dependent cytokine responses and increases the activation and proliferation of immune cells within the TME and tumor-associated lymphoid tissue. We also demonstrate that TAK-676 dosing results in significant STING-dependent antitumor activity, including complete regressions and durable memory T-cell immunity. We show that TAK-676 is well tolerated, exhibits dose-proportional pharmacokinetics in plasma, and exhibits higher exposure in tumor. The intravenous administration of TAK-676 provides potential treatment benefit in a broad range of tumor types. Further study of TAK-676 in first-in-human phase I trials is ongoing. Significance: TAK-676 is a novel systemic STING agonist demonstrating robust activation of innate and adaptive immune activity resulting in durable antitumor responses within multiple syngeneic tumor models. Clinical investigation of TAK-676 is ongoing.

TcsL is an essential virulence factor in Clostridium sordellii ATCC 9714.

Clostridium sordellii is an important pathogen of humans and animals, causing a range of diseases, including myonecrosis, sepsis, and shock. Although relatively rare in humans, the incidence of disease is increasing, and it is associated with high mortality rates, approaching 70%. Currently, very little is known about the pathogenesis of C. sordellii infections or disease. Previous work suggested that the lethal large clostridial glucosylating toxin TcsL is the major virulence factor, but a lack of genetic tools has hindered our ability to conclusively assign a role for TcsL or, indeed, any of the other putative virulence factors produced by this organism. In this study, we have developed methods for the introduction of plasmids into C. sordellii using RP4-mediated conjugation from Escherichia coli and have successfully used these techniques to insertionally inactivate the tcsL gene in the reference strain ATCC 9714, using targetron technology. Virulence testing revealed that the production of TcsL is essential for the development of lethal infections by C. sordellii ATCC 9714 and also contributes significantly to edema seen during uterine infection. This study represents the first definitive identification of a virulence factor in C. sordellii and opens the way for in-depth studies of this important human pathogen at the molecular level.

Non-toxigenic Clostridium sordellii: clinical and microbiological features of a case of cholangitis-associated bacteremia.

Toxigenic Clostridium sordellii strains are increasingly recognized to cause highly lethal infections in humans that are typified by a toxic shock syndrome (TSS). Two glucosylating toxins, lethal toxin (TcsL) and hemorrhagic toxin (TcsH) are believed to be important in the pathogenesis of TSS. While non-toxigenic strains of C. sordellii demonstrate reduced cytotoxicity in vitro and lower virulence in animal models of infection, there are few data regarding their behavior in humans. Here we report a non-TSS C. sordellii infection in the context of a polymicrobial bacterial cholangitis. The C. sordellii strain associated with this infection did not carry either the TcsL-encoding tcsL gene or the tcsH gene for TcsH. In addition, the strain was neither cytotoxic in vitro nor lethal in a murine sepsis model. These results provide additional correlative evidence that TcsL and TcsH increase the risk of mortality during C. sordellii infections.

Acute blockade of IL-25 in a colitis associated colon cancer model leads to increased tumor burden.

Chronic inflammation within the gastrointestinal tract results in an increased risk for developing colorectal cancer. Epithelial cytokines, including interleukin-25 (IL-25), are produced in the colon and are critical for protection from parasites, but can also be pathogenic in the context of inflammatory bowel diseases and allergy. Whether IL-25 is involved in the progression from inflammation to cancer is still largely unexplored. Using a well-established murine model for colitis-induced colon cancer; we aimed to determine the role of IL-25 in this process. We found that acute IL-25 blockade resulted in greater tumor burdens compared to isotype control treated mice. Histologically, α-IL-25 treated mice had increased colitis scores compared to mice receiving isotype control antibody, as well as decreased eosinophilia. This is the first study to explore the therapeutic potential of using an IL-25 blocking antibody during a chronic inflammatory setting. Taken together these data suggest that IL-25 plays an inhibitory role in the growth and development of colonic tumors.

Thymic stromal lymphopoietin-mediated epicutaneous inflammation promotes acute diarrhea and anaphylaxis.

Atopic dermatitis (AD) and food allergy are closely linked; however, the mechanisms that guide the progression of AD to allergic inflammatory responses at other mucosal surfaces, including the gastrointestinal tract, are not well understood. Here, we determined that exposure of mice that have been epicutaneously sensitized with thymic stromal lymphopoietin (TSLP) and antigen to repeated oral doses of the same antigen induced acute diarrhea and anaphylaxis. In this model, loss of TSLP signaling specifically in DCs led to loss of induced allergic diarrhea through lack of sensitization. While TSLP responses were not required during oral allergen challenge, CD4(+) T cells were required and transferred disease when introduced into naive hosts. In addition, oral exposure to the antigen prior to skin sensitization blocked development of allergic disease. Finally, mice lacking the receptor for IL-25 failed to develop acute diarrhea and anaphylaxis, highlighting a role for IL-25 in the initiation of type 2 immunity in the intestine. These results demonstrate a role for TSLP and IL-25 in the atopic march from skin sensitization to food allergic responses and provide a model system for the generation of potential therapeutic interventions.

EP4 and EP2 receptor activation of protein kinase A by prostaglandin E2 impairs macrophage phagocytosis of Clostridium sordellii.

PROBLEM: Clostridium sordellii causes endometrial infections, but little is known regarding host defenses against this pathogen. METHOD OF STUDY: We tested the hypothesis that the immunoregulatory lipid prostaglandin (PG) E2 suppresses human macrophage clearance of C. sordellii through receptor-induced increases in intracellular cyclic adenosine monophosphate (cAMP). The THP-1 macrophage cell line was used to quantify C. sordellii phagocytosis. RESULTS: PGE2 increased cAMP levels, activated protein kinase A (PKA), and inhibited the class A scavenger receptor-dependent phagocytosis of C. sordellii. Activation of the EP2 and EP4 receptors increased intracellular cAMP and inhibited phagocytosis, with evidence favoring a more important role for EP4 over EP2. This was supported by EP receptor expression data and the use of pharmacological receptor antagonists. In addition, the PKA isoform RI appeared to be more important than RII in mediating the suppression of ingestion of C. sordellii. CONCLUSION: The endogenous lipid mediator PGE2 impairs human innate immune responses against C. sordellii.

Pseudo-outbreak of Clostridium sordellii infection following probable cross-contamination in a hospital clinical microbiology laboratory.

We report a pseudo-outbreak of infection caused by Clostridium sordellii, an uncommon human pathogen. The pseudo-outbreak involved 6 patients and was temporally associated with a change by the clinical microbiology laboratory in the protocol of handling anaerobic culture specimens. All isolates were genetically indistinguishable from a laboratory reference strain used for quality control.