Journal of Innate Immunity最新文献

Introduction: Interleukin (IL)-6 has an important role in limiting urinary tract infection (UTI). Mice lacking IL-6 are more susceptible to uropathogenic Escherichia coli (UPEC), including increased formation of intracellular bacterial communities (IBCs). How IL-6 promotes UPEC clearance is unknown. We hypothesize IL-6 reduces UTI susceptibility by limiting IBC formation through early mechanism of infection.

Methods: Female mice were treated with vehicle or neutralizing antibodies to inhibit IL-6 or the IL-6 receptor (IL-6R) prior to transurethral UPEC infection. In rescue experiments, murine recombinant (r)IL-6 was administered to IL-6 knockout (KO) mice. Bladder IBCs, urinary and bladder bacterial burden, and UPEC expulsion were quantified. For clinical translation, human urothelial cells were pretreated with human rIL-6 and infected with UPEC. Bacterial attachment, invasion, and expulsion were quantified.

Results: Neutralization of IL-6 or IL-6R increased bladder IBC counts compared to isotype controls. Similarly, while IL-6 KO mice exhibited higher IBC counts than wild-type controls, this phenotype was reversed by rIL-6 administration. Gentamicin protection assays confirmed increased intracellular UPEC burden and reduced bacterial expulsion in IL-6 KO bladders. Recombinant IL-6 treatment enhanced UPEC expulsion in human urothelial cells without impacting bacterial attachment or invasion.

Conclusion: IL-6 facilitates UPEC expulsion, limiting intracellular UPEC early in infection and thus the initial formation of IBCs. Since IBC formation is a bottleneck in UPEC survival during UTI, these findings identify a mechanism whereby IL-6 reduces early UPEC urothelial infectivity.

Objective: The cGAS-STING pathway is a critical sensor in the innate immune response to intracellular pathogens, yet its therapeutic potential for augmenting macrophage-mediated control of Mycobacterium tuberculosis (Mtb) remains incompletely understood. This study investigated whether pharmacological activation of the STING pathway could enhance autophagy to promote Mtb clearance in human macrophages.

Methods: Human THP-1 monocytes were differentiated into macrophages and infected with Mtb. The effects of the STING agonist MIW815 (ADU-S100) on Mtb phagocytosis, intracellular bacterial survival, and autophagic flux were assessed using a combination of molecular and cellular techniques, including qRT-PCR, western blotting, colony-forming unit (CFU) assays, and confocal immunofluorescence microscopy. The dependency on the cGAS-STING pathway was confirmed using siRNA-mediated gene silencing.

Results: Pharmacological activation of STING with ADU-S100 significantly enhanced Mtb phagocytosis and subsequent intracellular clearance. This enhanced bactericidal activity was mechanistically linked to an increase in autophagic flux, as evidenced by elevated LC3-II protein levels and significantly increased colocalization of Mtb with lysosomal compartments. Importantly, treatment with the autophagy inhibitor hydroxychloroquine or silencing of cGAS significantly reversed these phenotypes, confirming the pivotal role of the STING-autophagy axis.

Conclusion: Activating the STING pathway with ADU-S100 is a potent host-directed strategy to bolster macrophage autophagy and enhance the elimination of intracellular Mtb. This provides a strong rationale for exploring STING agonists as a novel therapeutic intervention for tuberculosis, addressing a significant and clinically relevant challenge in infectious disease.

Pseudomonas aeruginosa (P. aeruginosa) is a significant pathogen associated with chronic infections, particularly in immunocompromised individuals. Its ability to form biofilms, combined with antibiotic resistance, plays a critical role in the persistence of these infections. Peptidyl-arginine deiminases (PADs), including PAD2 and PAD4 isoforms, are involved in neutrophil phagocytic killing of P. aeruginosa. The aim of this study was to investigate the impact of PAD enzymes on biofilm development and virulence factor production by P. aeruginosa, with focus on the multidrug resistant strain, PGO2330. Crystal-violet biofilm assays and confocal scanning laser microscopy were employed to assess the effects of PADs on biofilm formation. Cell motility assays, qPCR for quorum sensing (QS) gene expression and QS-related virulence factor assays were performed. This study reports that 20 nM of PAD2 and PAD4 reduced PGO2330 biofilm formation to 67.9±5.6% (p=0.0002) and 68.2±4.2% (p=0.0002), respectively. This effect was likely due to PAD2 and PAD4 reducing PGO2330 surface attachment (p<0.0001) and twitching motility (p<0.0001 and p=0.0190, respectively). PGO2330 exposed to PAD2 and PAD4 showed reduced lasR, lasI, rhlR, rhll and mvrf gene expression and reduced levels of extracellular DNA, rhamnolipid, pyocyanin and protease activity. Overall, the results revealed that in addition to inhibiting P. aeruginosa biofilm formation, PADs decrease the production of QS-related virulence factors, advancing knowledge of the antimicrobial properties of PAD enzymes and supporting further research into the development of PAD-based therapeutics.

Background: Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by dysregulated immune responses in the gut. Macrophages, as key innate immune cells in the intestinal mucosa, play a central role in both maintaining homeostasis and driving pathology in UC.

Summary: Under physiological conditions, intestinal macrophages exhibit a unique "inflammatory anergy" phenotype, supporting epithelial integrity and immune tolerance. In UC, however, persistent inflammatory signals promote monocyte recruitment and their polarization into pro-inflammatory M1-like macrophages. These cells secrete cytokines such as TNF-α, IL-1β, IL-6, and IL-12/23, produce reactive oxygen and nitrogen species (ROS/RNS), and release matrix metalloproteinases (MMPs), collectively driving epithelial barrier disruption, tissue damage, and sustained inflammation. This review comprehensively discusses the origin, heterogeneity, and functional plasticity of intestinal macrophages, their dynamic interactions with other cells, and key regulatory signaling pathways-such as NF-κB, JAK-STAT, and the NLRP3 inflammasome-in UC.

Key messages: We evaluate current and emerging macrophage-targeted therapies, including cytokine blockade, chemokine receptor antagonism, phenotypic reprogramming, nanomedicine, and cell-based interventions. Furthermore, we highlight the limitations of the M1/M2 dichotomy and emphasize the need for single-cell and spatial transcriptomic approaches to better define macrophage subsets in human disease. Advancing the understanding of macrophage biology in UC will facilitate the development of precise immunomodulatory strategies and biomarker-based diagnostics, ultimately aiming to bridge the gap between mechanistic discovery and improved patient care.

Introduction: Hemocytes are central to honey bee (Apis mellifera) immunity, but the roles of their subtypes under combined stressors are unclear. We tested the effects of temperature and bacterial challenge on hemocyte abundance and, for the first time in honey bees, used clodronate liposomes (CLD) to selectively deplete hemocytes.

Methods: Five-day-old (Nurses) and fifteen-day-old (Foragers) honey bees were treated with CLD, control liposomes, PBS, or left untreated, then exposed at either 32°C or 22°C and challenged with Escherichia coli, or Staphylococcus aureus. Survival, hemolymph volume, total hemocyte counts, and differential hemocyte counts were monitored over seven days.

Results: The CLD application demonstrated significant reductions in granulocyte and prohemocyte populations, indicating the highest vulnerability. A temperature drop to 22ºC buffered the negative impact on survival of CLD-induced immunosuppression. While bacterial challenges universally reduced hemocyte counts, we found a fundamental age-dependent difference where nurses maintained significantly higher baseline total hemocyte counts than foragers. Furthermore, temperature did not affect overall total hemocyte counts in 5-day-old nurse bees, but in 15-day-old foragers, it significantly modulated the hemocyte response to bacterial infection.

Conclusion: Hemocyte function is subtype-specific, shaped by temperature and age, with foragers showing greater vulnerability. Clodronate liposomes provide a new tool to dissect honey bee immune-environment interactions.

Introduction: Chloroquine (CQ), a well-known antimalarial agent, has been proposed as a potential antiviral compound due to its ability to interfere with multiple cellular pathways critical for viral replication. Although CQ exhibits broad-spectrum antiviral activity, its effect on host innate immune responses remains incompletely understood. The timing of CQ administration, whether before or after infection, may lead to different immunological outcomes. Therefore, the immunomodulatory effects of CQ should be carefully evaluated before antiviral therapy.

Methods: To investigate the immunomodulatory role of CQ (50 μm), we used immunofluorescence staining, Western blotting, and reporter assays to evaluate innate immune activation in A549 cells. We established a doxycycline-inducible system to activate mitochondrial antiviral signaling (MAVS)-mediated signaling without viral infection. Plaque assays and antiviral tests were performed to measure viral replication, while cytokine array and RT-qPCR were used to quantify cytokine production. Mitochondrial morphology was assessed using immunofluorescence microscopy.

Results: CQ enhanced innate immune responses triggered by dengue virus infection and poly(I:C) stimulation. This enhancement was associated with the activation of the MAVS protein and its upstream receptors, including retinoic acid-inducible gene I and melanoma differentiation-associated protein 5. CQ strengthened MAVS-dependent antiviral signaling and increased IL-6 induction more than 13-fold. Alterations in mitochondrial morphology may contribute to this immunostimulatory effect.

Conclusion: CQ promotes MAVS-mediated antiviral and inflammatory cytokine responses, potentially through its effect on mitochondrial dynamics. These findings indicate that while CQ may enhance antiviral defense, its immune-stimulating properties should be carefully evaluated prior to its use as an antiviral agent in treating RNA virus infections.

Introduction: Repeated exposures to Mycobacterium tuberculosis (Mtb) and related species may influence host responses, which in turn may affect vaccine efficacy and could even render the host less or more susceptible to progression to active tuberculosis (TB) disease.

Methods: Using well-differentiated primary human bronchial epithelial cells (PBEC), we investigated the effect of a prior exposure of the epithelium to Mtb and Mycobacterium bovis vaccine strain Bacille Calmette-Guerin (BCG) on the intracellular infection efficiency of Mtb and Mycobacterium avium (Mav) during a second exposure and measured cytokine and antimicrobial peptide secretion.

Results: PBEC that were first exposed to BCG were significantly more resistant to subsequent infection with Mtb. A similar trend was observed in PBEC that were previously exposed to Mtb, although to a lesser magnitude compared to BCG pre-exposure. Furthermore, while the first exposure to mycobacteria induced inflammatory cytokine secretion by PBEC, cytokine secretion was dampened upon a secondary exposure to Mtb, most strongly in previously BCG-exposed cells. Secretion of the antimicrobial peptide hBD-2 was not affected by sequential exposures.

Conclusion: Repeated exposure of differentiated airway epithelial cells to mycobacteria reduced intracellular infection and inflammation.

Background: Neutrophils, previously viewed as short-lived microbial killers, are now recognized as highly adaptable regulators of innate immunity. Advances in transcriptomic, metabolic, and epigenetic profiling reveal their remarkable heterogeneity and ability to adopt microenvironment-specific phenotypes. In the lung, this plasticity gives neutrophils a double role: they fight infection but can also cause long-lasting inflammation, tissue damage, and scarring.

Summary: We review how neutrophils are activated, move, and act in lung disease, focusing on their release of proteases, production of reactive oxygen species, and formation of extracellular traps. We also describe repair-promoting neutrophil types and treatments that aim to reduce damage while keeping normal neutrophil defense intact.

Key messages: Learning how neutrophils change within the lung microenvironment will help create better and more precise treatments for lung inflammation and tissue damage.

Introduction: Group B Streptococcus (GBS) asymptomatic colonizes the female genital tract (FGT) but can contribute to adverse pregnancy outcomes including pre-term birth, chorioamnionitis, and neonatal infection. We previously observed that GBS elicits FGT cytokine responses, including IL-17, during murine vaginal colonization; yet the anti-GBS cellular immune response during colonization remained unknown. We hypothesized that GBS may induce cellular immunity, resulting in FGT clearance.

Methods: Herein, we utilize depleting antibodies and knockout mice and performed flow cytometry to investigate cellular immunes responses during GBS colonization.

Results: We found that neutrophils (effectors of the IL-17 response) are important for GBS mucosal control as neutrophil depletion promoted increased GBS burdens in FGT tissues. Flow cytometric analysis of immune populations in the vagina, cervix, and uterus revealed, however, that GBS colonization did not induce a marked increase in FGT CD45+ immune cells. We also found that that Vγ6+ γδ T cells comprise a primary source of FGT IL-17. Finally, using knockout mice, we observed that IL-17-producing γδ T cells are important for the control of GBS in the FGT during murine colonization.

Conclusions: Taken together, this work characterizes FGT cellular immunity and suggests that GBS colonization does not elicit a significant immune response, which may be a bacterial directed adaptive outcome. However, certain FGT immune cells, such as neutrophils and ɣδ T cells, contribute to host defense and control of GBS colonization.