Innate, antigen-independent role for T cells in the activation of the immune system by Propionibacterium acnes

In Vitro Evaluation of Common Antimicrobial Solutions Used for Breast Implant Soaking and Breast Pocket Irrigation-Part 2: Efficacy Against Biofilm-Associated Bacteria

Background

Biofilm-associated bacteria have been observed in both breast implant revision and tissue expander-implant exchange surgeries. The utilization of antimicrobial solutions in breast surgery, especially those containing triple antibiotics (TAB) and/or 10% povidone-iodine (PI), may help reduce existing biofilm-associated bacteria, which is particularly important in a mature breast pocket that may contain residual bacteria from a previously colonized implant surface or, theoretically, bacteria that may arrive postoperatively through hematogenous spread.

Objectives

A series of in vitro assessments was performed to evaluate the antimicrobial utility of TAB and PI, either alone or in combination, against preformed biofilm-associated bacteria.

Methods

Preformed biofilm-associated gram-positive and gram-negative bacterial strains were exposed to TAB and PI ± TAB for up to 30 minutes in a bacterial time-kill assay. Efficacy of various dilutions of PI and the effects of serum protein on PI efficacy were also investigated.

Results

TAB was ineffective at the timeframes tested when utilized alone; when utilized in conjunction with PI, significant log reduction of all biofilm-associated bacterial species tested was achieved when treated for at least 5 minutes. PI alone at a concentration of 25% or higher was also effective, although its efficacy was negatively affected by increasing serum protein concentration only for Staphylococcus epidermidis.

Conclusions

Our data indicate that PI-containing solutions significantly reduce biofilm-associated bacteria, suggesting potential utility for breast pocket irrigation during revision or exchange surgeries. Care should be taken to minimize excessive dilution of PI to maintain efficacy.

COVID-19 vaccine and boosted immunity: Nothing ad interim to do?

Today, Coronavirus Disease 2019 (COVID-19) is a global public health emergency and vaccination measures to counter its diffusion are deemed necessary. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiological agent of the disease, unleashes a T-helper 2 immune response in those patients requiring intensive care. Here, we illustrate the immunological mechanism to train the immune system towards a more effective and less symptomatic T-helper 1 immune response, to be exploited against SARS-CoV-2.

A common microbial signature is present in the lower airways of interstitial lung diseases including sarcoidosis

Background: The etiology of pulmonary sarcoidosis is not well established. Although the mechanism triggering pulmonary sarcoidosis remains to be established, inflammatory reactions seem to play an important role in this process. Objectives: The aim of this study was to define the composition of the lower airway microbiota in the bronchoalveolar lavage (BAL) of patients affected by interstitial lung diseases, including sarcoidosis, to determine whether the bacterial signature differs among these diseases. Methods: Ten patients affected by pulmonary sarcoidosis and 9 patients affected by other interstitial lung diseases were enrolled. 16S rRNA next-generation sequencing was used to study BAL microbial composition of these patients, and were also compared with already published microbial content in higher airways of such diseases. Results: Four phyla dominated the lower airway microbiota, Bacteroidetes being the most abundant phylum in both groups (56.9%). Diversity analysis showed no significant differences between the various diseases, particularly between pulmonary sarcoidosis and other interstitial lung diseases affecting lower airways. Conclusions: Our data indicate that the bacterial lower airways microbiota share the same signature and, therefore, cannot be used as a diagnostic tool to discriminate among different interstitial lung diseases, including sarcoidosis, while microbial diversity is present when considering lower or higher respiratory airways. (Sarcoidosis Vasc Diffuse Lung Dis 2018; 35: 354-362).

Peripheral canine CD4(+)CD8(+) double-positive T cells - unique amongst others

T lymphocytes co-expressing CD4 and CD8 ("double-positive T cells") are commonly associated with a thymic developmental stage of T cells. Their first description in humans and pigs as extrathymic T cells with a memory phenotype almost 30 years ago came as a surprise. Meanwhile peripheral double-positive T cells have been described in a growing number of different species. In this review we highlight novel data from our very recent studies on canine peripheral double-positive T cells which point to unique features of double-positive T cells in the dog. In contrast to porcine CD4(+)CD8(+) T cells forming a homogenous cellular population based on their expression of CD4 and CD8α, canine CD4(+)CD8(+) T cells can be divided into three different cellular subsets with distinct expression levels of CD4 and CD8α. Double-positive T cells expressing CD8β are present in humans and dogs but absent in swine. Moreover, canine CD4(+)CD8(+) T cells can not only develop from CD4(+) single-positive T cells but also from CD8(+) single-positive T cells. Together, this places canine CD4(+)CD8(+) T cells closer to their human than porcine counterparts since human double-positive T cells also appear to be heterogeneous in their CD4 and CD8α expression and have both CD4(+) and CD8(+) T cells as progenitor cells. However, CD4(+) single-positive T cells are the more potent progenitors for canine double-positive T cells, whereas CD8(+) single-positive T cells are more potent progenitors for human double-positive T cells. Canine double-positive T cells have an activated phenotype and may have as yet unrecognized roles in vivo in immunity to infection or in inflammatory diseases such as chronic infection, autoimmunity, allergy, or cancer.

Bacterial skin commensals and their role as host guardians

Recent years' investigations of the co-evolution and functional integration of the human body and its commensal microbiota have disclosed that the microbiome has a major impact on physiological functions including protection against infections, reaction patterns in the immune system, and disposition for inflammation-mediated diseases. Two ubiquitous members of the skin microbiota, the Gram-positive bacteria Staphylococcus epidermidis and Propionibacterium acnes, are predominant on human epithelia and in sebaceous follicles, respectively. Their successful colonisation is a result of a commensal or even mutualistic lifestyle, favouring traits conferring persistency over aggressive host-damaging properties. Some bacterial properties suggest an alliance with the host to keep transient, potential pathogens at bay, such as the ability of S. epidermidis to produce antimicrobials, or the production of short-chain fatty acids by P. acnes. These features can function together with host-derived components of the innate host defence to establish and maintain the composition of a health-associated skin microbiota. However, depending largely on the host status, the relationship between the human host and S. epidermidis/P. acnes can also have parasitic features. Both microorganisms are frequently isolated from opportunistic infections. S. epidermidis is a causative agent of hospital-acquired infections, mostly associated with the use of medical devices. P. acnes is suspected to be of major importance in the pathogenesis of acne and also in a number of other opportunistic infections. In this review we will present bacterial factors and traits of these two key members of our skin microbiota and discuss how they contribute to mutualistic and parasitic properties. The elucidation of their roles in health-promoting or disease-causing processes could lead to new prophylactic and therapeutic strategies against skin disorders and other S. epidermidis/P. acnes-associated diseases, and increase our understanding of the delicate interplay of the skin microbiota with the human host.

TNFR2 maintains adequate IL-12 production by dendritic cells in inflammatory responses by regulating endogenous TNF levels

Sepsis-induced immune reactions are reduced in TNF receptor 2 (TNFR2)-deficient mice as previously shown. In order to elucidate the underlying mechanisms, the functional integrity of myeloid cells of TNFR2-deficient mice was analyzed and compared to wild type (WT) mice. The capacity of dendritic cells to produce IL-12 was strongly impaired in TNF-deficient mice, mirroring impaired production of IL-12 by WT dendritic cells in sepsis or after LPS or TNF pre-treatment. In addition, TNFR2-deficient mice were refractory to LPS pre-treatment and also to hyper-sensitization by inactivated Propionibacterium acnes, indicating habituation to inflammatory stimuli by the immune response when TNFR2 is lacking. Constitutive expression of TNF mRNA in kidney, liver, spleen, colon and lung tissue, and the presence of soluble TNFR2 in urine of healthy WT mice supported the conclusion that TNF is continuously present in naïve mice and controlled by soluble TNFR2. In TNFR2-deficient mice endogenous TNF levels cannot be balanced and the continuous exposure to enhanced TNF levels impairs dendritic cell function. In conclusion, TNF pre-exposure suppresses secondary inflammatory reactions of myeloid cells; therefore, continuous control of endogenous TNF by soluble TNFR2 seems to be essential for the maintenance of adequate sensitivity to inflammatory stimuli.

TLR9-dependent IL-23/IL-17 is required for the generation of Stachybotrys chartarum-induced hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an inflammatory lung disease that develops after repeated exposure to inhaled particulate Ag. Stachybotrys chartarum is a dimorphic fungus that has been implicated in a number of respiratory illnesses, including HP. In this study, we have developed a murine model of S. chartarum-induced HP that reproduces pathology observed in human HP, and we have hypothesized that TLR9-mediated IL-23 and IL-17 responses are required for the generation of granulomatous inflammation induced by inhaled S. chartarum. Mice that undergo i.p. sensitization and intratracheal challenge with 10(6) S. chartarum spores developed granulomatous inflammation with multinucleate giant cells, accompanied by increased accumulation of T cells. S. chartarum sensitization and challenge resulted in robust pulmonary expression of IL-17 and IL-23. S. chartarum-mediated granulomatous inflammation required intact IL-23 or IL-17 responses and required TLR9, because TLR9(-/-) mice displayed reduced IL-17 and IL-23 expression in whole lung associated with decreased accumulation of IL-17 expressing CD4(+) and γδ T cells. Compared with S. chartarum-sensitized dendritic cells (DC) isolated from WT mice, DCs isolated from TLR9(-/-) mice had a reduced ability to produce IL-23 in responses to S. chartarum. Moreover, shRNA knockdown of IL-23 in DCs abolished IL-17 production from splenocytes in response to Ag challenge. Finally, the intratracheal reconstitution of IL-23 in TLR9(-/-) mice recapitulated the immunopathology observed in WT mice. In conclusion, our studies suggest that TLR9 is critical for the development of Th17-mediated granulomatous inflammation in the lung in response to S. chartarum.

Th1 and Th17 immune responses to viable Propionibacterium acnes in patients with sarcoidosis

BACKGROUND

Propionibacterium acnes and Mycobacterium tuberculosis have emerged as probable candidates responsible for sarcoidosis. This study was conducted to investigate the Th1/Th17 responses elicited by these pathogens in sarcoidosis and to clarify the causative role of these pathogens.

METHODS

Peripheral blood mononuclear cells (PBMCs) obtained from patients with sarcoidosis and from healthy volunteers were, respectively, co-cultured with viable P. acnes, with Bacille de Calmette et Guérin (BCG) as a viable M. tuberculosis complex, and with the early secretory antigenic target (ESAT)-6. Th1 cytokine production was measured using RT-PCR and enzyme-linked immunospot (ELISPOT) assays, and interleukin (IL)-17 mRNA expression was measured by RT-PCR.

RESULTS

IL-2 secretion from PBMCs after stimulation with P. acnes was significantly higher in patients with sarcoidosis than in the controls. Similarly, IL-2 and IL-12 mRNA expression after stimulation with P. acnes was significantly higher in PBMCs from patients with sarcoidosis than in PBMCs from controls. In contrast, IL-17 mRNA expression was significantly lower in PBMCs from patients with sarcoidosis than in PBMCs from controls. No significant differences between the groups were observed in the responses to stimulation with BCG or ESAT-6.

CONCLUSION

Sarcoidosis may arise from an imbalance of Th1/Th17 immune responses against viable P. acnes, but not M. tuberculosis complex.

TLR9-dependent and independent pathways drive activation of the immune system by Propionibacterium acnes

Propionibacterium acnes is usually a relatively harmless commensal. However, under certain, poorly understood conditions it is implicated in the etiology of specific inflammatory diseases. In mice, P. acnes exhibits strong immunomodulatory activity leading to splenomegaly, intrahepatic granuloma formation, hypersensitivity to TLR ligands and endogenous cytokines, and enhanced resistance to infection. All these activities reach a maximum one week after P. acnes priming and require IFN-γ and TLR9. We report here the existence of a markedly delayed (1-2 weeks), but phenotypically similar TLR9-independent immunomodulatory response to P. acnes. This alternative immunomodulation is also IFN-γ dependent and requires functional MyD88. From our experiments, a role for MyD88 in the IFN-γ-mediated P. acnes effects seems unlikely and the participation of the known MyD88-dependent receptors, including TLR5, Unc93B-dependent TLRs, IL-1R and IL-18R in the development of the alternative response has been excluded. However, the crucial role of MyD88 can partly be attributed to TLR2 and TLR4 involvement. Either of these two TLRs, activated by bacteria and/or endogenously generated ligands, can fulfill the required function. Our findings hint at an innate immune sensitizing mechanism, which is potentially operative in both infectious and sterile inflammatory disorders.

High susceptibility to lipopolysaccharide-induced lethal shock in encephalomyocarditis virus-infected mice

Secondary bacterial infection in humans is one of the pathological conditions requiring clinical attention. In this study, we examined the effect of lipopolysaccharide (LPS) on encephalomyocarditis virus (EMCV) infected mice. All mice inoculated with EMCV at 5 days before LPS challenge died within 24 h. LPS-induced TNF-α mRNA expression was significantly increased in the brain and heart at 5 days after EMCV infection. CD11b⁺/TLR4⁺ cell population in the heart was remarkably elevated at 5 days after EMCV infection, and sorted CD11b⁺ cells at 5 days after EMCV infection produced a large amount of TNF-α on LPS stimulation in vivo and in vitro. In conclusion, we found that the infiltration of CD11b⁺ cells into infected organs is involved in the subsequent LPS-induced lethal shock in viral encephalomyocarditis. This new experimental model can help define the mechanism by which secondary bacterial infection causes a lethal shock in viral encephalomyocarditis.

Stachybotrys chartarum-induced hypersensitivity pneumonitis is TLR9 dependent

Hypersensitivity pneumonitis (HP), an inflammatory lung disease, develops after repeated exposure to inhaled particulate antigen and is characterized by a vigorous T helper type 1-mediated immune response, resulting in the release of IL-12 and interferon (IFN)-γ. These T helper type 1 cytokines may participate in the pathogenesis of HP. Stachybotrys chartarum (SC) is a dimorphic fungus implicated in a number of respiratory illnesses, including HP. Here, we have developed a murine model of SC-induced HP that reproduces pathology observed in human HP and hypothesized that toll receptor-like 9 (TLR9)-mediated dendritic cell responses are required for the generation of granulomatous inflammation induced by inhaled SC. Mice sensitized and challenged with 10(6) SC spores develop granulomatous inflammation with multinucleate giant cells, accompanied by increased accumulation of neutrophils and CD4(+) and CD8(+) T cells. SC sensitization and challenge resulted in robust pulmonary expression of tumor necrosis factor-α, IL-12, and IFN-γ. SC-mediated granulomatous inflammation required IFN-γ and was TLR9 dependent, because TLR9(-/-) mice displayed reduced peribronchial inflammation, decreased accumulation and/or activation of polymorphonuclear (PMN) and CD4(+) and CD8(+) T cells, and reduced lung expression of type 1 cytokines and chemokines. T-cell production of IFN-γ was IL-12 dependent. Our studies suggest that TLR9 is critical for dendritic cell-mediated development of a type 1 granulomatous inflammation in the lung in response to SC.

Sarcoidosis--scientific progress and clinical challenges

Sarcoidosis is an uncommon systemic inflammatory disorder characterized by noncaseating granulomatous inflammation that most commonly affects the lungs, intrathoracic lymph nodes, eyes and skin. One-third or more of patients with sarcoidosis have chronic, unremitting inflammation with progressive organ impairment. Findings of family and genetic studies indicate a genetic susceptibility to sarcoidosis, with genes in the MHC region having a dominant role. Immunologic hallmarks of the disease include highly polarized expression of cytokines produced by type 1 T helper cells and tumor necrosis factor (TNF) at sites of inflammation. Increasing evidence obtained within the past decade suggests the etiology of sarcoidosis predominantly involves microbial triggers, with the most convincing data implicating mycobacterial or propionibacterial organisms. Innate immune mechanisms, possibly involving misfolding and aggregation of serum amyloid A, might have a critical role in the pathobiology of sarcoidosis. Despite these advances, there are no clinically useful biomarkers that can assist the clinician in diagnosis, prognosis or assessment of treatment effects. Corticosteroids remain the cornerstone of therapy when organ function is threatened or progressively impaired. The role of immunosuppressive drugs and anti-TNF agents in the treatment of sarcoidosis remains uncertain, and there are no FDA-approved therapies. Meaningful progress in developing clinically useful tools and new therapies will depend on further advances in understanding the pathogenesis of sarcoidosis and its disease-specific pathways.