Timothy J Break

On-going Mechanical Damage from Mastication Drives Homeostatic Th17 Cell Responses at the Oral Barrier.

&NA; Immuno‐surveillance networks operating at barrier sites are tuned by local tissue cues to ensure effective immunity. Site‐specific commensal bacteria provide key signals ensuring host defense in the skin and gut. However, how the oral microbiome and tissue‐specific signals balance immunity and regulation at the gingiva, a key oral barrier, remains minimally explored. In contrast to the skin and gut, we demonstrate that gingiva‐resident T helper 17 (Th17) cells developed via a commensal colonization‐independent mechanism. Accumulation of Th17 cells at the gingiva was driven in response to the physiological barrier damage that occurs during mastication. Physiological mechanical damage, via induction of interleukin 6 (IL‐6) from epithelial cells, tailored effector T cell function, promoting increases in gingival Th17 cell numbers. These data highlight that diverse tissue‐specific mechanisms govern education of Th17 cell responses and demonstrate that mechanical damage helps define the immune tone of this important oral barrier. Graphical Abstract Figure. No caption available. HighlightsDistinct signals shape the Th17 cell network at the oral barrierOral barrier Th17 cells develop independently of commensal microbe colonizationPhysiologic damage through mastication promotes the generation of oral Th17 cellsBarrier damage triggers oral Th17‐cell‐mediated protective immunity and inflammation &NA; The signals regulating immunity at the gingiva, a key oral barrier, remain unclear. Dutzan et al. show that oral barrier Th17 cells are induced in response to mastication rather than commensal colonization, identifying physiologic mechanical damage as a unique tissue‐specific cue conditioning local immunity and inflammation at the oral barrier.

CXCR1-mediated neutrophil degranulation and fungal killing promote Candida clearance and host survival.

CXCR1 as a mediator of neutrophil fungal killing and host defense against systemic fungal infection in mice and humans. Candida camera The yeast Candida albicans can live symbiotically in human gut and skin, but when it penetrates the mucosal barrier and enters the bloodstream, it can cause life-threatening systemic infection. Now, Swamydas et al. provide a look at how neutrophils control Candida. They show that the neutrophil-selective chemokine receptor Cxcr1 plays a critical role in antifungal host defense. Mice lacking Cxcr1 were more susceptible to systemic candidiasis because of defective neutrophil-mediated fungal killing. Neutrophils from humans with a mutant CXCR1 allele also had defective fungal response. These data suggest that Cxcr1 is critical for innate host defense against fungal infection. Systemic Candida albicans infection causes high morbidity and mortality and is now the leading cause of nosocomial bloodstream infection in the United States. Neutropenia is a major risk factor for poor outcome in infected patients; however, the molecular factors that mediate neutrophil trafficking and effector function during infection are poorly defined. Using a mouse model of systemic candidiasis, we found that the neutrophil-selective CXC chemokine receptor Cxcr1 and its ligand, Cxcl5, are highly induced in the Candida-infected kidney, the target organ in the model. To investigate the role of Cxcr1 in antifungal host defense in vivo, we generated Cxcr1−/− mice and analyzed their immune response to Candida. Mice lacking Cxcr1 exhibited decreased survival with enhanced Candida growth in the kidney and renal failure. Increased susceptibility of Cxcr1−/− mice to systemic candidiasis was not due to impaired neutrophil trafficking from the blood into the infected kidney but was the result of defective killing of the fungus by neutrophils that exhibited a cell-intrinsic decrease in degranulation. In humans, the mutant CXCR1 allele CXCR1-T276 results in impaired neutrophil degranulation and fungal killing and was associated with increased risk of disseminated candidiasis in infected patients. Together, our data demonstrate a biological function for mouse Cxcr1 in vivo and indicate that CXCR1-dependent neutrophil effector function is a critical innate protective mechanism of fungal clearance and host survival in systemic candidiasis.

CX3CR1 Is Dispensable for Control of Mucosal Candida albicans Infections in Mice and Humans

ABSTRACT Candida albicans is part of the normal commensal microbiota of mucosal surfaces in a large percentage of the human population. However, perturbations of the hosts immune response or bacterial microbiota have been shown to predispose individuals to the development of opportunistic Candida infections. It was recently discovered that a defect in the chemokine receptor CX3CR1 increases susceptibility of mice and humans to systemic candidiasis. However, whether CX3CR1 confers protection against mucosal C. albicans infection has not been investigated. Using two different mouse models, we found that Cx3cr1 is dispensable for the induction of interleukin 17A (IL-17A), IL-22, and IL-23 in the tongue after infection, as well as for the clearance of mucosal candidiasis from the tongue or lower gastrointestinal (GI) tract colonization. Furthermore, the dysfunctional human CX3CR1 allele CX3CR1-M280 was not associated with development of recurrent vulvovaginal candidiasis (RVVC) in women. Taken together, these data indicate that CX3CR1 is not essential for protection of the host against mucosal candidiasis, underscoring the dependence on different mammalian immune factors for control of mucosal versus systemic Candida infections.

Mononuclear phagocyte-mediated antifungal immunity: the role of chemotactic receptors and ligands

Over the past two decades, fungal infections have emerged as significant causes of morbidity and mortality in patients with hematological malignancies, hematopoietic stem cell or solid organ transplantation and acquired immunodeficiency syndrome. Besides neutrophils and CD4+ T lymphocytes, which have long been known to play an indispensable role in promoting protective antifungal immunity, mononuclear phagocytes are now being increasingly recognized as critical mediators of host defense against fungi. Thus, a recent surge of research studies has focused on understanding the mechanisms by which resident and recruited monocytes, macrophages and dendritic cells accumulate and become activated at the sites of fungal infection. Herein, we critically review how a variety of G-protein coupled chemoattractant receptors and their ligands mediate mononuclear phagocyte recruitment and effector function during infection by the most common human fungal pathogens.

Batf3-dependent CD103(+) dendritic cell accumulation is dispensable for mucosal and systemic antifungal host defense.

Dendritic cells (DCs) are critical for defense against a variety of pathogens and the formation of adaptive immune responses. The transcription factor Batf3 is critical for the development of CD103(+)CD11b(-) DCs, which promote IL-12-dependent protective immunity during viral and parasitic infections, dampen Th2 immunity during helminthic infection, and exert detrimental effects during bacterial infection. Whether CD103(+) DCs modulate immunity during systemic or mucosal fungal disease remains unknown. Herein, we report that Batf3 is critical for accumulation of CD103(+) DCs in the kidney and tongue at steady state, for their expansion during systemic and oropharyngeal candidiasis, and for tissue-specific production of IL-12 in kidney but not tongue during systemic and oropharyngeal candidiasis, respectively. Importantly, deficiency of CD103(+) DCs does not impair survival or fungal clearance during systemic or oropharyngeal candidiasis, indicating that Batf3-dependent CD103(+) DC accumulation mediates pathogen- and tissue-specific immune effects.

VT-1161 protects mice against oropharyngeal candidiasis caused by fluconazole-susceptible and -resistant Candida albicans

Background Candida albicans, the most common human fungal pathogen, causes chronic mucosal infections in patients with inborn errors of IL-17 immunity that rely heavily on chronic, often lifelong, azole antifungal agents for treatment. However, a rise in azole resistance has predicated a need for developing new antifungal drugs. Objectives To test the in vitro and in vivo efficacy of VT-1161 and VT-1129 in the treatment of oropharyngeal candidiasis with azole-susceptible or -resistant C. albicans strains. Methods MICs of VT-1161, VT-1129 and nine licensed antifungal drugs were determined for 31 Candida clinical isolates. The drug concentrations in mouse serum and tongues were measured following oral administration. IL-17-signalling-deficient Act1-/- mice were infected with fluconazole-susceptible or fluconazole-resistant C. albicans strains, and the amount of mucosal fungal burden was determined after fluconazole or VT-1161 treatment. Results Fourteen isolates (45%) were not fluconazole susceptible (MIC ≥4 mg/L). VT-1161 and VT-1129 showed significant in vitro activity against the majority of the 31 mucosal clinical isolates (MIC50 0.03 and 0.06 mg/L, respectively), including Candida glabrata (MIC50, 0.125 and 0.25 mg/L, respectively). After oral doses, VT-1161 and VT-1129 concentrations in mouse serum and tongues were well above their MIC50 values. VT-1161 was highly effective as treatment of both fluconazole-susceptible and -resistant oropharyngeal candidiasis in Act1-/- mice. Conclusions VT-1129 and VT-1161 exhibit significant in vitro activity against Candida strains, including fluconazole-resistant C. albicans and C. glabrata. VT-1161 administration in mice results in significant mucosal drug accumulation and eradicates infection caused by fluconazole-susceptible and -resistant Candida strains.

PD-L1 up-regulation restrains Th17 cell differentiation in STAT3 loss- and STAT1 gain-of-function patients.

Patients with hypomorphic mutations in STAT3 and patients with hypermorphic mutations in STAT1 share several clinical and cellular phenotypes suggesting overlapping pathophysiologic mechanisms. We, therefore, examined cytokine signaling and CD4+ T cell differentiation in these cohorts to characterize common pathways. As expected, differentiation of Th17 cells was impaired in both cohorts. We found that STAT1 was hyperphosphorylated in response to cytokine stimulation in both cohorts and that STAT1-dependent PD-L1 up-regulation—known to inhibit Th17 differentiation in mouse models—was markedly enhanced as well. Overexpression of SOCS3 strongly inhibited phosphorylation of STAT1 and PD-L1 up-regulation, suggesting that diminished SOCS3 expression may lead to the observed effects. Defects in Th17 differentiation could be partially overcome in vitro via PD-L1 inhibition and in a mouse model of STAT3 loss-of-function by crossing them with PD-1 knockout mice. PD-L1 may be a potential therapeutic target in several genetic diseases of immune deficiency affecting cytokine signaling.

CD8+ T cells produce a dialyzable antigen-specific activator of dendritic cells

Cellular lysates from PPD+ donors have been reported to transfer tuberculin reactivity to naïve recipients, but not diphtheria reactivity, and vice versa. A historically controversial topic, the terms “transfer factor” and “DLE” were used to characterize the reactivity‐transferring properties of lysates. Intrigued by these reported phenomena, we found that the cellular extract derived from antigen‐specific memory CD8+ T cells induces IL‐6 from antigen‐matched APCs. This ultimately elicits IL‐17 from bystander memory CD8+ T cells. We have identified that dialyzable peptide sequences, S100a9, and the TCR β chain from CD8+ T cells contribute to the molecular nature of this activity. We further show that extracts from antigen‐targeted T cells enhance immunity to Staphylococcus aureus and Candida albicans. These effects are sensitive to immunization protocols and extraction methodology in ways that may explain past discrepancies in the reproducibility of passive cellular immunity.

VT-1598 inhibits the in vitro growth of mucosal Candida strains and protects against fluconazole-susceptible and -resistant oral candidiasis in IL-17 signalling-deficient mice

Background Chronic mucocutaneous candidiasis (CMC) treatment often induces drug resistance, posing long-term challenges. A novel broad-spectrum fungal CYP51 inhibitor, VT-1598, specifically targets fungal CYP51, but not human CYP enzymes. Objectives To determine the efficacy of VT-1598 in the treatment of oral Candida infection caused by fluconazole-susceptible and -resistant clinical isolates. Methods The MICs of VT-1598 and fluconazole for 28 Candida isolates recovered from patients with inherited CMC were determined using CLSI M27-A3 and M27-S4 guidelines. Plasma and tongue VT-1598 or fluconazole concentrations were measured in mice following oral administration to determine tissue distribution. Tongue fungal load was determined in IL-17 signalling-deficient Act1-/- mice following sublingual Candida albicans infection and oral treatment with fluconazole or VT-1598. Results Among the 28 Candida isolates, 10 (36%) had fluconazole MICs of ≥4 mg/L, whereas VT-1598 demonstrated potent in vitro activity against all isolates (MIC90, 0.125 mg/L). After oral administration, VT-1598 levels in mouse plasma and tongue were significantly greater than those of fluconazole. In vivo, VT-1598 exhibited significant efficacy against fluconazole-susceptible and -resistant C. albicans, even at low drug doses. Furthermore, after a 10 day washout period, tongue fungal burdens in fluconazole-treated mice returned to vehicle control levels, whereas, in contrast, they were undetectable in mice treated with VT-1598. Conclusions VT-1598 effectively controls in vitro growth of mucosally derived Candida clinical isolates, including fluconazole-resistant strains. In vivo, VT-1598 eliminates C. albicans, even after a long washout period or at low doses. Therefore, VT-1598 is a promising drug candidate that may significantly improve treatment options for CMC patients.

VT-1598 Inhibits the in vitro Growth of Mucosal Candida Isolates and Protects Against Oropharyngeal Candidiasis in IL-17 Deficient Mice

Abstract Background Patients with chronic mucocutaneous candidiasis (CMC) often develop azole-resistant Candida infections, making treatment difficult due to lack of oral antifungal drug options. VT-1598 is a novel broad-spectrum fungal CYP51 inhibitor designed for exquisite selectivity for the fungal target versus human CYP enzymes to circumvent classic azole side effects like drug–drug interactions. We report the efficacy of VT-1598 in the treatment of oral Candida infection (including by azole-resistant strains). Methods The in vitro MIC values of 28 Candida species isolated from patients with CMC due to AIRE mutations were tested against VT-1598 and fluconazole (FLC), using CLSI broth microdilution M27-S4. Plasma VT-1598 levels were measured using LC–MS/MS with electrospray ionization. Tongue fungal load was determined in IL-17 deficient Act1- /- mice following sublingual C. albicans infection and once-daily oral treatment for 4 days with 25 mg/kg FLC or 3.2, 8, and 20 mg/kg VT-1598 starting 18 hours post-infection. Results Among 28 Candida isolates tested (22 C. albicans, three C. glabrata, and one each of C. utilis, C. dubiliensis, and C. krusei), 10 (36%) were not susceptible to FLC, based on CLSI breakpoints (>4 mg/ml). Remarkably, all 28 isolates were highly susceptible to VT-1598 (MIC50 and MIC90, 0.06 and 0.125 mg/ml, respectively). Oral administration of VT-1598 led to mean drug levels in mouse plasma (2.0, 3.0, and 11 mg/ml at the low, mid, and high doses, respectively) that were higher than the MIC values. In vivo, VT-1598 was significantly more effective, compared with FLC, against FLC-susceptible and -resistant C. albicans, and led to elimination of fungal growth even at the lowest tested dose (3.2 mg/kg). After a 10-day washout period from the last dose, mice treated with VT-1598 did not have mucosal fungal growth, while mice treated with FLC had tongue fungal loads similar to vehicle control. Conclusion VT-1598 shows in vitro activity against mucosally derived Candida, including FLC-resistant strains. In vivo, VT-1598 achieves high plasma concentrations and eliminates viable C. albicans, even at low doses and after an extended washout period. These data indicate that VT-1598 may be a significantly improved treatment option for patients with CMC. Disclosures C. M. Yates, Viamet Pharmaceuticals, Inc.: Employee, Salary. O. J. Cohen, Viamet Pharmaceuticals, Inc.: Employee, Salary. R. J. Schotzinger, Viamet Pharmaceuticals, Inc.: Employee, Salary. E. P. Garvey, Viamet Pharmaceuticals, Inc.: Employee, Salary. M. Lionakis, Viamet Pharmaceuticals: Research support (CRADA), Research support