Amoxicillin treatment of pneumococcal pneumonia impacts bone marrow neutrophil maturation and function.

Pneumonia caused by Streptococcus pneumoniae is a leading cause of death worldwide. A growing body of evidence indicates that the successful treatment of bacterial infections results from synergy between antibiotic-mediated direct antibacterial activity and the host's immune defenses. However, the mechanisms underlying the protective immune responses induced by amoxicillin, a ß-lactam antibiotic used as the first-line treatment of S. pneumoniae infections, have not been characterized. A better understanding of amoxicillin's effects on host-pathogen interactions might facilitate the development of other treatment options. Given the crucial role of neutrophils in the control of S. pneumoniae infections, we decided to investigate amoxicillin's impact on neutrophil development in a mouse model of pneumococcal superinfection. A single therapeutic dose of amoxicillin almost completely eradicated the bacteria and prevented local and systemic inflammatory responses. Interestingly, in this context, amoxicillin treatment did not impair the emergency granulopoiesis triggered in the bone marrow by S. pneumoniae. Importantly, treatment of pneumonia with amoxicillin was associated with a greater mature neutrophil count in the bone marrow; these neutrophils had specific transcriptomic and proteomic profiles. Furthermore, amoxicillin-conditioned, mature neutrophils in the bone marrow had a less activated phenotype and might be rapidly mobilized in peripheral tissues in response to systemic inflammation. Thus, by revealing a novel effect of amoxicillin on the development and functions of bone marrow neutrophils during S. pneumoniae pneumonia, our findings provide new insights into the impact of amoxicillin treatment on host immune responses.

Treatment of Bacterial Infections with ß-Lactams: Cooperation with Innate Immunity.

ß-Lactams are the most widely prescribed antibiotics used for the control and treatment of bacterial infections. The direct effect of ß-lactams on bacteria is well studied worldwide. In the context of infections and as a consequence of their direct activity against the pathogen, ß-lactams also regulate antibacterial immune responses. This knowledge has led to the theorem that the effectiveness of ß-lactam treatment results from the synergy between the drug and the immune response. Key players in this immune response, with an essential role in the clearance of live and dead bacteria, are the myeloid cells. In this review, we summarize the data that shed light on how ß-lactams interact with myeloid cells during bacterial infection treatment.

Antibiotic-related gut dysbiosis induces lung immunodepression and worsens lung infection in mice.

BACKGROUND: Gut dysbiosis due to the adverse effects of antibiotics affects outcomes of lung infection. Previous murine models relied on significant depletion of both gut and lung microbiota, rendering the analysis of immune gut-lung cross-talk difficult. Here, we study the effects of antibiotic-induced gut dysbiosis without lung dysbiosis on lung immunity and the consequences on acute P. aeruginosa lung infection. METHODS: C57BL6 mice received 7 days oral vancomycin-colistin, followed by normal regimen or fecal microbial transplant or Fms-related tyrosine kinase 3 ligand (Flt3-Ligand) over 2 days, and then intra-nasal P. aeruginosa strain PAO1. Gut and lung microbiota were studied by next-generation sequencing, and lung infection outcomes were studied at 24 h. Effects of vancomycin-colistin on underlying immunity and bone marrow progenitors were studied in uninfected mice by flow cytometry in the lung, spleen, and bone marrow. RESULTS: Vancomycin-colistin administration induces widespread cellular immunosuppression in both the lung and spleen, decreases circulating hematopoietic cytokine Flt3-Ligand, and depresses dendritic cell bone marrow progenitors leading to worsening of P. aeruginosa lung infection outcomes (bacterial loads, lung injury, and survival). Reversal of these effects by fecal microbial transplant shows that these alterations are related to gut dysbiosis. Recombinant Flt3-Ligand reverses the effects of antibiotics on subsequent lung infection. CONCLUSIONS: These results show that gut dysbiosis strongly impairs monocyte/dendritic progenitors and lung immunity, worsening outcomes of P. aeruginosa lung infection. Treatment with a fecal microbial transplant or immune stimulation by Flt3-Ligand both restore lung cellular responses to and outcomes of P. aeruginosa following antibiotic-induced gut dysbiosis.

Influenza infection rewires energy metabolism and induces browning features in adipose cells and tissues.

Like all obligate intracellular pathogens, influenza A virus (IAV) reprograms host cell's glucose and lipid metabolism to promote its own replication. However, the impact of influenza infection on white adipose tissue (WAT), a key tissue in the control of systemic energy homeostasis, has not been yet characterized. Here, we show that influenza infection induces alterations in whole-body glucose metabolism that persist long after the virus has been cleared. We report depot-specific changes in the WAT of IAV-infected mice, notably characterized by the appearance of thermogenic brown-like adipocytes within the subcutaneous fat depot. Importantly, viral RNA- and viral antigen-harboring cells are detected in the WAT of infected mice. Using in vitro approaches, we find that IAV infection enhances the expression of brown-adipogenesis-related genes in preadipocytes. Overall, our findings shed light on the role that the white adipose tissue, which lies at the crossroads of nutrition, metabolism and immunity, may play in influenza infection.

Gut Dysbiosis during Influenza Contributes to Pulmonary Pneumococcal Superinfection through Altered Short-Chain Fatty Acid Production.

Secondary bacterial infections often complicate viral respiratory infections. We hypothesize that perturbation of the gut microbiota during influenza A virus (IAV) infection might favor respiratory bacterial superinfection. Sublethal infection with influenza transiently alters the composition and fermentative activity of the gut microbiota in mice. These changes are attributed in part to reduced food consumption. Fecal transfer experiments demonstrate that the IAV-conditioned microbiota compromises lung defenses against pneumococcal infection. In mechanistic terms, reduced production of the predominant short-chain fatty acid (SCFA) acetate affects the bactericidal activity of alveolar macrophages. Following treatment with acetate, mice colonized with the IAV-conditioned microbiota display reduced bacterial loads. In the context of influenza infection, acetate supplementation reduces, in a free fatty acid receptor 2 (FFAR2)-dependent manner, local and systemic bacterial loads. This translates into reduced lung pathology and improved survival rates of double-infected mice. Lastly, pharmacological activation of the SCFA receptor FFAR2 during influenza reduces bacterial superinfection.

Interleukin-7 protects against bacterial respiratory infection by promoting IL-17A-producing innate T-cell response.

Interleukin-7 (IL-7) is a critical cytokine in B- and T-lymphocyte development and maturation. Recent evidence suggests that IL-7 is a preferential homeostatic and survival factor for RORγt+ innate T cells such as natural killer T (NKT) cells, γδT cells, and mucosal-associated invariant T (MAIT) cells in the periphery. Given the important contribution of these populations in antibacterial immunity at barrier sites, we questioned whether IL-7 could be instrumental in boosting the local host immune response against respiratory bacterial infection. By using a cytokine-monoclonal antibody approach, we illustrated a role for topical IL-7 delivery in increasing the pool of RORγt+ IL-17A-producing innate T cells. Prophylactic IL-7 treatment prior to Streptococcus pneumoniae infection led to better bacterial containment, a process associated with increased neutrophilia and that depended on γδT cells and IL-17A. Last, combined delivery of IL-7 and α-galactosylceramide (α-GalCer), a potent agonist for invariant NKT (iNKT) cells, conferred an almost total protection in terms of survival, an effect associated with enhanced IL-17 production by innate T cells and neutrophilia. Collectively, we provide a proof of concept that IL-7 enables fine-tuning of innate T- cell functions. This might pave the way for considering IL-7 as an innovative biotherapeutic against bacterial infection.

Therapeutic Synergy Between Antibiotics and Pulmonary Toll-Like Receptor 5 Stimulation in Antibiotic-Sensitive or -Resistant Pneumonia.

Bacterial infections of the respiratory tract constitute a major cause of death worldwide. Given the constant rise in bacterial resistance to antibiotics, treatment failure is increasingly frequent. In this context, innovative therapeutic strategies are urgently needed. Stimulation of innate immune cells in the respiratory tract [via activation of Toll-like receptors (TLRs)] is an attractive approach for rapidly activating the body's immune defenses against a broad spectrum of microorganisms. Previous studies of the TLR5 agonist flagellin in animal models showed that standalone TLR stimulation does not result in the effective treatment of pneumococcal respiratory infection but does significantly improve the therapeutic outcome of concomitant antibiotic treatment. Here, we investigated the antibacterial interaction between antibiotic and intranasal flagellin in a mouse model of pneumococcal respiratory infection. Using various doses of orally administered amoxicillin or systemically administered cotrimoxazole, we found that the intranasal instillation of flagellin (a dose that promotes maximal lung pro-inflammatory responses) induces synergistic rather than additive antibacterial effects against antibiotic-susceptible pneumococcus. We next set up a model of infection with pneumococcus that is resistant to multiple antibiotics in the context of influenza superinfection. Remarkably, the combination of amoxicillin and flagellin effectively treated superinfection with the amoxicillin-resistant pneumococcus since the bacterial clearance was increased by more than 100-fold compared to standalone treatments. Our results also showed that, in response to flagellin, the lung tissue generated an innate immune response even though it had been damaged by the influenza virus and pneumococcal infections. In conclusion, we demonstrated that the selective boosting of lung innate immunity is a conceptually advantageous approach for improving the effectiveness of antibiotic treatment and fighting antibiotic-resistant bacteria.

TLR9-mediated dendritic cell activation uncovers mammalian ganglioside species with specific ceramide backbones that activate invariant natural killer T cells.

CD1d-restricted invariant natural killer T (iNKT) cells represent a heterogeneous population of lipid-reactive T cells that are involved in many immune responses, mediated through T-cell receptor (TCR)-dependent and/or independent activation. Although numerous microbial lipid antigens (Ags) have been identified, several lines of evidence have suggested the existence of relevant Ags of endogenous origin. However, the identification of their precise nature as well as the molecular mechanisms involved in their generation are still highly controversial and ill defined. Here, we identified two mammalian gangliosides-namely monosialoganglioside GM3 and disialoganglioside GD3-as endogenous activators for mouse iNKT cells. These glycosphingolipids are found in Toll-like receptor-stimulated dendritic cells (DC) as several species varying in their N-acyl fatty chain composition. Interestingly, their ability to activate iNKT cells is highly dependent on the ceramide backbone structure. Thus, both synthetic GM3 and GD3 comprising a d18:1-C24:1 ceramide backbone were able to activate iNKT cells in a CD1d-dependent manner. GM3 and GD3 are not directly recognized by the iNKT TCR and required the Ag presenting cell intracellular machinery to reveal their antigenicity. We propose a new concept in which iNKT cells can rapidly respond to pre-existing self-molecules after stress-induced structural changes in CD1d-expressing cells. Moreover, these gangliosides conferred partial protection in the context of bacterial infection. Thus, this report identified new biologically relevant lipid self-Ags for iNKT cells.

Alteration of Flt3-Ligand-dependent de novo generation of conventional dendritic cells during influenza infection contributes to respiratory bacterial superinfection.

Secondary bacterial infections contribute to the excess morbidity and mortality of influenza A virus (IAV) infection. Disruption of lung integrity and impaired antibacterial immunity during IAV infection participate in colonization and dissemination of the bacteria out of the lungs. One key feature of IAV infection is the profound alteration of lung myeloid cells, characterized by the recruitment of deleterious inflammatory monocytes. We herein report that IAV infection causes a transient decrease of lung conventional dendritic cells (cDCs) (both cDC1 and cDC2) peaking at day 7 post-infection. While triggering emergency monopoiesis, IAV transiently altered the differentiation of cDCs in the bone marrow, the cDC1-biaised pre-DCs being particularly affected. The impaired cDC differentiation during IAV infection was independent of type I interferons (IFNs), IFN-γ, TNFα and IL-6 and was not due to an intrinsic dysfunction of cDC precursors. The alteration of cDC differentiation was associated with a drop of local and systemic production of Fms-like tyrosine kinase 3 ligand (Flt3-L), a critical cDC differentiation factor. Overexpression of Flt3-L during IAV infection boosted the cDC progenitors' production in the BM, replenished cDCs in the lungs, decreased inflammatory monocytes' infiltration and lowered lung damages. This was associated with partial protection against secondary pneumococcal infection, as reflected by reduced bacterial dissemination and prolonged survival. These findings highlight the impact of distal viral infection on cDC genesis in the BM and suggest that Flt3-L may have potential applications in the control of secondary infections.

Interleukin-22 Immunotherapy during Severe Influenza Enhances Lung Tissue Integrity and Reduces Secondary Bacterial Systemic Invasion.

Severe bacterial (pneumococcal) infections are commonly associated with influenza and are significant contributors to the excess morbidity and mortality of influenza. Disruption of lung tissue integrity during influenza participates in bacterial pulmonary colonization and dissemination out of the lungs. Interleukin-22 (IL-22) has gained considerable interest in anti-inflammatory and anti-infection immunotherapy over the last decade. In the current study, we investigated the effect of exogenous IL-22 delivery on the outcome of pneumococcal superinfection postinfluenza. Our data show that exogenous treatment of influenza virus-infected mice with recombinant IL-22 reduces bacterial dissemination out of the lungs but is without effect on pulmonary bacterial burden. Reduced systemic bacterial dissemination was linked to reinforced pulmonary barrier functions, as revealed by total protein measurement in the bronchoalveolar fluids, intratracheal fluorescein isothiocyanate-dextran tracking, and histological approaches. We describe an IL-22-specific gene signature in the lung tissue of influenza A virus (IAV)-infected (and naive) mice that might explain the observed effects. Indeed, exogenous IL-22 modulates the gene expression profile in a way that suggests reinforcement of tissue integrity. Our results open the way to alternative approaches for limiting postinfluenza bacterial superinfection, particularly, systemic bacterial invasion.

Type I IFN Receptor Signaling Controls IL7-Dependent Accumulation and Activity of Protumoral IL17A-Producing γδT Cells in Breast Cancer.

The protumoral activity of γδT17 cells has recently emerged in a wide variety of solid malignancies, including breast cancer. These cells exert their detrimental functions by promoting tumor growth, angiogenesis, and subsequent metastasis development. However, the intratumoral factors that regulate the biology of γδT17cells within the tumor microenvironment are less well understood. Here, using two experimental models of breast cancer, we reinforced the concept that tumor-infiltrating γδT17 cells are endowed with protumoral functions, which promote tumor progression and metastasis development. More importantly, we demonstrated a critical role for type I IFN signaling in controlling the preferential accumulation in the tumor bed of a peculiar subset of γδT17 cells displaying a CD27- CD3bright phenotype (previously associated with the invariant Vγ6Vδ1+ TCR). Interestingly, this effect was indirect and partially relied on the IFNAR1-dependent control of IL7 secretion, a factor that triggers proliferation and activating functions of deleterious γδT17 cells. Our work therefore identifies a key role of the type I IFN/IL7 axis in the regulation of intratumoral γδT17-cell functions and in the development of primary breast tumor growth and metastasis.Significance: Tumor-derived IL7 can represent a therapeutic target to prevent accumulation of immune cells endowed with potent protumoral activities. Cancer Res; 78(1); 195-204. ©2017 AACR.

Co-delivery of the NKT agonist α-galactosylceramide and tumor antigens to cross-priming dendritic cells breaks tolerance to self-antigens and promotes antitumor responses.

Vaccines designed to abrogate the tolerance of tumor self-antigens and amplify cytotoxic CD8+ T cells (CTLs) have promise for the treatment of cancer. Type I natural killer (NKT) cells have attracted considerable interest in the cancer therapy field. In the current study, we have exploited the unique ability of NKT cells to serve as T-helper cells to license dendritic cells (DCs) for cross priming with the aim to generate efficient CTL antitumor responses. To this end, we designed a nanoparticle-based vaccine to target cross-priming DCs via the Clec9a endocytic pathway. Our results showed for the first time that simultaneous co-delivery of the NKT agonist α-galactosylceramide and tumor self-antigens (Trp2 and gp100) to CD8α+ DCs promotes strong antitumor responses in prophylactic and therapeutic settings (advanced solid tumor model in the mouse). We attributed the vaccine's therapeutic effects to NKT cells (but not to T-helper lymphocytes) and CD8+ T cells. Efficacy was correlated with an elevated ratio between tumor antigen-specific CD8+ T cells and regulatory CD4+ T lymphocytes within the tumor. The nanoparticle-based vaccine actively targeted human CLEC9A-expressing BDCA3+ DCs - the equivalent of murine cross-priming CD8α+ DCs - and induced a strong expansion of effector memory tumor self-antigen (Melan -A)-specific CD8+ T cells from peripheral blood mononuclear cells sourced from healthy donors and melanoma patients. Together, our result shed light on novel therapeutic approaches for controlling tumor development.

Enhancement of Adjuvant Functions of Natural Killer T Cells Using Nanovector Delivery Systems: Application in Anticancer Immune Therapy.

Type I natural killer T (NKT) cells have gained considerable interest in anticancer immune therapy over the last decade. This "innate-like" T lymphocyte subset has the unique ability to recognize foreign and self-derived glycolipid antigens in association with the CD1d molecule expressed by antigen-presenting cells. An important property of these cells is to bridge innate and acquired immune responses. The adjuvant function of NKT cells might be exploited in the clinics. In this review, we discuss the approaches currently being used to target NKT cells for cancer therapy. In particular, we highlight ongoing strategies utilizing NKT cell-based nanovaccines to optimize immune therapy.

Solubilization of α-galactosylceramide in aqueous medium: Impact on Natural Killer T cell activation and antitumor responses.

The potent antitumor effect of α-galactosylceramide (α-GalCer) is based on its recognition by invariant Natural Killer T cells (iNKT) after its capture and presentation by antigen presenting cells including dendritic cells (DCs). Synthetic α-GalCer has already been tested in advanced cancer patients but no or only moderate clinical responses were obtained. To optimize α-GalCer efficacy, we have postulated that alternative formulations impacting its molecular organization in aqueous medium could modify DC uptake and iNKT-based immune responses. To this end, we have developed two strategies: (1) the formulation of α-GalCer in non-cationic liposomes and (2) the synthesis of a water-soluble α-GalCer analogue by anchoring a polyethyleneglycol moiety on its sugar head. The biological activities of these new preparations were compared to that induced by the classically used Polysorbate 20 α-GalCer micelles. Both formulations retained their uptake by DCs and activated iNKT cells both in vitro and in vivo. Despite a lower cytokine production, the formulations induced a potent immune response able to control lung murine carcinoma. In conclusion, it is possible to increase α-GalCer solubility in aqueous solution without limiting its antitumor properties.

NKT Cell Hyporesponsiveness Leads to Unrestrained Accumulation of Marginal Zone B Cells in Hypercholesterolemic Apolipoprotein E-Deficient Mice.

Recently, the role of B cells in atherosclerosis has gained more attention but studies have mainly focused on B1 and follicular B cell subsets. Therefore, the contribution of marginal zone (MZ) B cells in experimental atherosclerosis remains elusive. In the current study, we examined the MZ B cell compartment in atherosclerotic apoE-deficient (apoE-/-) mice and found that hypercholesterolemia in these mice was associated with an increased number and percentage of MZ B cells. This aberrant accumulation of MZ B cells was not associated with alterations in their development or increased proliferation but was due to decreased apoptotic cell death. This decrease in MZ B cell death in apoE-/- mice was associated with the reduced capacity of invariant NKT (iNKT) cells to produce IFN-γ and IL-4 after activation. Lowering cholesterol plasma levels with ezetimibe in apoE-/- mice reversed iNKT function and MZ B cell accumulation. To elucidate the mechanism whereby iNKT cells control MZ B cell accumulation in apoE-/- mice, we performed an adoptive transfer of iNKT cells and found that only wild-type iNKT cells but not IFN-γ-/- iNKT cells reversed MZ B cell accumulation in apoE-/- recipient mice. Our findings reveal that lipid changes associated with atherosclerotic disease induce decreased production of IFN-γ by iNKT, which in turn leads to aberrant accumulation of MZ B cells. This study further extends the importance of iNKT cells in regulating MZ B cell compartment.

Exogenous Activation of Invariant Natural Killer T Cells by α-Galactosylceramide Reduces Pneumococcal Outgrowth and Dissemination Postinfluenza.

Influenza A virus infection can predispose to potentially devastating secondary bacterial infections. Invariant natural killer T (iNKT) cells are unconventional, lipid-reactive T lymphocytes that exert potent immunostimulatory functions. Using a mouse model of postinfluenza invasive secondary pneumococcal infection, we sought to establish whether α-galactosylceramide (α-GalCer [a potent iNKT cell agonist that is currently in clinical development]) could limit bacterial superinfection. Our results highlighted the presence of a critical time window during which α-GalCer treatment can trigger iNKT cell activation and influence resistance to postinfluenza secondary pneumococcal infection. Intranasal treatment with α-GalCer during the acute phase (on day 7) of influenza virus H3N2 and H1N1 infection failed to activate (gamma interferon [IFN-γ] and interleukin-17A [IL-17A]) iNKT cells; this effect was associated with a strongly reduced number of conventional CD103+ dendritic cells in the respiratory tract. In contrast, α-GalCer treatment during the early phase (on day 4) or during the resolution phase (day 14) of influenza was associated with lower pneumococcal outgrowth and dissemination. Less intense viral-bacterial pneumonia and a lower morbidity rate were observed in superinfected mice treated with both α-GalCer (day 14) and the corticosteroid dexamethasone. Our results open the way to alternative (nonantiviral/nonantibiotic) iNKT-cell-based approaches for limiting postinfluenza secondary bacterial infections. IMPORTANCE: Despite the application of vaccination programs and antiviral drugs, influenza A virus (IAV) infection is responsible for widespread morbidity and mortality (500,000 deaths/year). Influenza infections can also result in sporadic pandemics that can be devastating: the 1918 pandemic led to the death of 50 million people. Severe bacterial infections are commonly associated with influenza and are significant contributors to the excess morbidity and mortality of influenza. Today's treatments of secondary bacterial (pneumococcal) infections are still not effective enough, and antibiotic resistance is a major issue. Hence, there is an urgent need for novel therapies. In the present study, we set out to evaluate the efficacy of α-galactosylceramide (α-GalCer)-a potent agonist of invariant NKT cells that is currently in clinical development-in a mouse model of postinfluenza, highly invasive pneumococcal pneumonia. Our data indicate that treatment with α-GalCer reduces susceptibility to superinfections and, when combined with the corticosteroid dexamethasone, reduces viral-bacterial pneumonia.

Superantigenic Yersinia pseudotuberculosis induces the expression of granzymes and perforin by CD4+ T cells.

Bacterial superantigens (SAgs) are immunostimulatory toxins that induce acute diseases mainly through the massive release of inflammatory cytokines. Yersinia pseudotuberculosis is the only Gram-negative bacterium known to produce a SAg (Y. pseudotuberculosis-derived mitogen [YPM]). This SAg binds major histocompatibility complex class II molecules on antigen-presenting cells and T cell receptors (TcR) bearing the variable region Vß3, Vß9, Vß13.1, or Vß13.2 (in humans) and Vß7 or Vß8 (in mice). We have previously shown that YPM exacerbates the virulence of Y. pseudotuberculosis in mice. With a view to understanding the mechanism of YPM's toxicity, we compared the immune response in BALB/c mice infected with a YPM-producing Y. pseudotuberculosis or the corresponding isogenic, SAg-deficient mutant. Five days after infection, we observed strong CD4(+) Vß7(+) T cell expansion and marked interleukin-4 (IL-4) production in mice inoculated with SAg-producing Y. pseudotuberculosis. These phenomena were correlated with the activation of ypm gene transcription in liver and spleen. A transcriptomic analysis revealed that the presence of YPM also increased expression of granzyme and perforin genes in the host's liver and spleen. This expression was attributed to a CD4(+) T cell subset, rather than to natural killer T (NKT) cells that display a TcR with a Vß region that is potentially recognized by YPM. Increased production of cytotoxic molecules was correlated with hepatotoxicity, as demonstrated by an increase in plasma alanine aminotransferase activity. Our results demonstrate that YPM activates a potentially hepatotoxic CD4(+) T cell population.

Targeted delivery of α-galactosylceramide to CD8α+ dendritic cells optimizes type I NKT cell-based antitumor responses.

Immunotherapy aiming at enhancing innate and acquired host immunity is a promising approach for cancer treatment. The invariant NKT (iNKT) cell ligand α-galactosylceramide (α-GalCer) holds great promise in cancer therapy, although several concerns limit its use in clinics, including the uncontrolled response it promotes when delivered in a nonvectorized form. Therefore, development of delivery systems to in vivo target immune cells might be a valuable option to optimize iNKT cell-based antitumor responses. Using dendritic cell (DC)-depleted mice, DC transfer experiments, and in vivo active cell targeting, we show that presentation of α-GalCer by DCs not only triggers optimal primary iNKT cell stimulation, but also maintains secondary iNKT cell activation after challenge. Furthermore, targeted delivery of α-GalCer to CD8α(+) DCs, by means of anti-DEC205 decorated nanoparticles, enhances iNKT cell-based transactivation of NK cells, DCs, and γδ T cells. We report that codelivery of α-GalCer and protein Ag to CD8α(+) DCs triggers optimal Ag-specific Ab and cytotoxic CD8(+) T cell responses. Finally, we show that targeting nanoparticles containing α-GalCer and Ag to CD8α(+) DCs promotes potent antitumor responses, both in prophylactic and in therapeutic settings. Our data may have important implications in tumor immunotherapy and vaccine development.

Type I NKT-cell-mediated TNF-α is a positive regulator of NLRP3 inflammasome priming.

The NLRP3 inflammasome plays a crucial role in the innate immune response to pathogens and exogenous or endogenous danger signals. Its activity must be precisely and tightly regulated to generate tailored immune responses. However, the immune cell subsets and cytokines controlling NLRP3 inflammasome activity are still poorly understood. Here, we have shown a link between NKT-cell-mediated TNF-α and NLRP3 inflammasome activity. The NLRP3 inflammasome in APCs was critical to potentiate NKT-cell-mediated immune responses, since C57BL/6 NLRP3 inflammasome-deficient mice exhibited reduced responsiveness to α-galactosylceramide. Importantly, NKT cells were found to act as regulators of NLRP3 inflammasome signaling, as NKT-cell-derived TNF-α was required for optimal IL-1ß and IL-18 production by myeloid cells in response to α-galactosylceramide, by acting on the NLRP3 inflammasome priming step. Thus, NKT cells play a role in the positive regulation of NLRP3 inflammasome priming by mediating the production of TNF-α, thus demonstrating another means by which NKT cells control early inflammation.

Activation of Type 3 innate lymphoid cells and interleukin 22 secretion in the lungs during Streptococcus pneumoniae infection.

Mucosal sites are continuously exposed to pathogenic microorganisms and are therefore equipped to control respiratory infections. Type 3 innate lymphoid cells (ILC3) are key players in antimicrobial defense in intestinal mucosa, through interleukin 17 and interleukin 22 (IL-22) production. The present study aimed at analyzing the distribution and function of ILC3 in the respiratory tract. We first observed that lung mucosa harbors a discrete population of ILC3 expressing CD127, CD90, CCR6, and the transcriptional factor RORγt. In addition, lung ILC3 were identified as a major source of IL-22 in response to interleukin 23 stimulation. During Streptococcus pneumoniae infection, ILC3 rapidly accumulated in the lung tissue to produce IL-22. In response to S. pneumoniae, dendritic cells and MyD88, an important adaptor of innate immunity, play critical functions in IL-22 production by ILC3. Finally, administration of the Toll-like receptor 5 agonist flagellin during S. pneumoniae challenge exacerbated IL-22 production by ILC3, a process that protects against lethal infection. In conclusion, boosting lung ILC3 might represent an interesting strategy to fight respiratory bacterial infections.