Intracellular Bacterial Infection Research Articles

Nanoflower-Mediated Gallium-Protoporphyrin IX Complex for Intracellular Antibacterial and Immunomodulatory Effects in Macrophage-Targeted Therapy.

Intracellular bacterial infections are challenging due to immune evasion and antibiotic resistance, especially within macrophages harboring dormant bacteria. Here, a synergistic antibacterial strategy is presented using the PG3M@GaPP nanoflowers, which integrate immune modulation, iron metabolism disruption, and antibacterial photodynamic therapy (APDT) to eliminate intracellular bacteria. This nanoflower encapsulates a gallium-protoporphyrin IX complex (GaPP) within mannose-functionalized poly-l-lysine dendrimers (PG3M), enabling targeted delivery to macrophages via mannose receptor recognition. PG3M@GaPP promotes macrophage polarization to the anti-inflammatory M2 phenotype, enhancing immune modulation and bacterial uptake. The platform's positive charge facilitates endosomal escape, releasing GaPP in the acidic intracellular environment, where free iron ions compete with gallium ions to form the iron-protoporphyrin IX complex (FePP). This disrupts the gallium/iron ion balance, enhancing the Trojan horse effect of gallium ions and inducing iron metabolism-dependent bacterial death. Additionally, laser activation of GaPP generates reactive oxygen species (ROS), further amplifying bacterial killing via APDT. In vitro and in vivo experiments show that PG3M@GaPP outperforms both free GaPP and commercial antibiotics in eliminating intracellular bacteria. These nanoflowers offers an alternative, nonantibiotic approach to combat intracellular infections, addressing drug resistance and providing a promising platform for antibacterial therapies.

Antibacterial activity of the novel peptide Pac-525 with the RGD motif against intracellular Escherichia coli

Infections caused by invasive intracellular bacteria pose major therapeutic challenges due to pathogen survival and growth inside of host cells as well as the low intracellular accessibility for conventional antibiotics. The limited ability of most antibiotics to enter intracellular compartments underscores the urgent need for innovative antimicrobial agents capable of overcoming these barriers. In this study, the antibacterial peptide Pac525 was synthesized with the RGD domain to facilitate efficient penetration into eukaryotic cells. The efficacy and safety of RGD-Pac525 was evaluated in intracellular infection models, using the macrophage cell line RAW 264.7, chicken intestinal organoids, and chicken embryo tissues via the chorioallantoic membrane (CAM). Our findings from cell line experiments demonstrate that the RGD-Pac525 peptide retained the antimicrobial properties of the original peptide without compromising its efficacy. While RGD-Pac525 reduced the intracellular adherent-invasive pathogen Escherichia coli KV203 by 50% in RAW 264.7 macrophage cells, it did not adversely affect the macrophage viability. Additionally, RGD-Pac525 effectively reduced the intracellular bacterial burden in organoids, without compromising their structural integrity. In ovo bioassays, a substantial reduction in the bacterial load was observed in liver and intestinal tissues, indicating the peptide ability to achieve systemic distribution and to overcome tissue barriers. RGD-Pac525 was effective in infection models by suppressing bacterial growth. Preliminary observations suggest it may also affect host responses, indicating a potential for combined antimicrobial and therapeutic effects that warrant further studies. This study provides a compelling proof of concept for utilizing RGD-modified antimicrobial peptides for treatment of intracellular bacterial infections.

Intracellular Bacteria-Mimicking Whole-Cell Cancer Vaccine Potentiates Immune Responses via Concurrent Activation of NLRP3 Inflammasome and STING Pathway.

Whole-cell cancer vaccines can trigger broader-spectrum antitumoral immune responses. However, a lack of immunogenicity and unclear interactions with antigen-presenting cells (APCs) hinder their translation into effective personalized immunotherapies. Herein, tumor cells are engineered via layer-by-layer bimineralization integrating sequential silicification and manganese mineralization, which reprograms the APC recognition with high immunogenicity. These bacteria-mimicking cells with enhanced mechanical stiffness protect against antigen degradation and facilitate phagocytosis by APCs. The secondary Mn mineralization creates spiky-like MnO2 nanoclusters with extreme roughness that stimulate the intracellular NLRP3 inflammasome and concurrently activate the cGAS-STING pathway, which is closely related to diverse immune patterns in response to intracellular bacterial infection. As a consequence, such bimineralized tumor cells outperform other monomineralized vaccinations in terms of prophylactic and therapeutic outcomes against the development and progression of a mouse B16F10 melanoma model. This bimineralization strategy uniquely bridges materials science and immunology, offering a transformative framework for engineering immunogenic whole-cell cancer vaccines.

A TAT Peptide-Functionalized Liposome Delivery Phage System (TAT-Lip@PHM) for an Enhanced Eradication of Intracellular MRSA

Background: Intracellular bacteria frequently result in chronic and recurrent infections. MRSA is one of the most prevalent facultative intracellular bacteria in clinical infections. The drug resistance of MRSA and the difficulty of most antibiotics in entering cells result in a suboptimal clinical efficacy of antibiotics in the treatment of intracellular MRSA. Bacteriophages represent a promising alternative therapy in the context of the current antimicrobial resistance crisis. Nevertheless, the low efficiency of phage entry into cells and their rapid inactivation remain challenges in the treatment of intracellular MRSA using phages. The utilization of functionalized carriers for the delivery of phages into cells and their protection represents a feasible strategy. Methods: In this study, a new MRSA bacteriophage (vB_SauS_PHM) was isolated from hospital sewage, exhibiting the characteristics of short incubation period, large lytic amount, and good environmental tolerance. Subsequently, vB_SauS_PHM was encapsulated by TAT peptide-functionalized liposomes through microfluidic technology and size-exclusion chromatography (SEC), forming a phage delivery system, designated TAT-Lip@PHM. Results: The encapsulation rate of the phage by TAT-Lip@PHM was 20.3%, and the cell entry efficiency was ≥90% after 8 h. The 24 h eradication rate of 300 μg/mL TAT-Lip@PHM against intracellular MRSA was 94.05% (superior to the 21.24% and 44.90% of vB_SauS_PHM and Lip@PHM, respectively), while the mammalian cell activity was >85% after 24 h incubation. Conclusions: The TAT-Lip@PHM effectively delivered the phage into the cell and showed an excellent killing effect on intracellular MRSA with low cytotoxicity. This work provides a technical reference for the application of phages in the treatment of intracellular bacterial infection.

The photosensitizer DH-I-180-3 regulates intracellular bacterial growth by increasing the secretion of proinflammatory cytokines via the NF-κB- and MAPK-mediated signaling pathways and promoting phagosome maturation in Salmonella-infected mouse macrophages.

Photodynamic therapy (PDT) is a known strategy for treating cancer; in PDT, photosensitizers are activated by light stimulation and then induce reactive oxygen species (ROS) production to damage cancer tissues. Recently evidence has shown that PDT can also be used as a novel treatment strategy to control pathogenic bacteria. In previous studies, the photosensitizer DH-I-180-3 was reported to effectively regulate multidrug-resistant Mycobacterium tuberculosis growth. Here, we confirmed the effects of DH-I-180-3 on the antibacterial activity and inflammatory response of macrophages to Salmonella. Photoactivated DH-I-180-3 regulated intracellular bacterial growth in Salmonella-infected macrophages. Moreover, DH-I-180-3 increased intracellular ROS levels in Salmonella-infected macrophages. The phosphorylation of the intracellular signaling proteins IκBα and JNK1/2 was increased in DH-I-180-3-treated Salmonella-infected macrophages. Additionally, we observed that DH-I-180-3 significantly increased the mRNA expression and protein secretion of the proinflammatory cytokine TNF-α and promoted phagosome maturation by upregulating EEA1, LAMP1, and Cathepsin D in Salmonella-infected macrophages. Overall, these results demonstrate that photoactivated DH-I-180-3 enhances the bactericidal response to intracellular bacterial infection by promoting inflammatory signaling pathways and phagosome maturation. Therefore, DH-I-180-3 has the potential to be developed into PDT for treating bacterial-infection.

Palygorskite-based antibacterial composites induced intracellular S. aureus ferroptosis through SSTR2.

Palygorskite-based antibacterial composites induced intracellular S. aureus ferroptosis through SSTR2.

Host immunity and intracellular bacteria evasion mechanisms: Enhancing host-directed therapies with drug delivery systems.

Host immunity and intracellular bacteria evasion mechanisms: Enhancing host-directed therapies with drug delivery systems.

NIR-responsive bio-system with sequential antibacterial and immunomodulatory effects for the treatment of periodontitis

NIR-responsive bio-system with sequential antibacterial and immunomodulatory effects for the treatment of periodontitis

Serine protease Rv2569c inhibits inflammatory response and promotes intracellular survival of Mycobacterium tuberculosis by targeting the RhoG-NF-κB-NLRP3 pathway.

Serine protease Rv2569c inhibits inflammatory response and promotes intracellular survival of Mycobacterium tuberculosis by targeting the RhoG-NF-κB-NLRP3 pathway.

Harnessing advanced computational approaches to design novel antimicrobial peptides against intracellular bacterial infections

Harnessing advanced computational approaches to design novel antimicrobial peptides against intracellular bacterial infections

SAMHD1 deficiency enhances macrophage-mediated clearance of Salmonella Typhimurium via NF-κB activation in zebrafish.

Mutations in the gene encoding the protein containing the sterile alpha motif and the HD domain (SAMHD1) have been implicated in the occurrence of type I interferonopathies. SAMHD1 is also involved in blocking the replication of retroviruses and certain DNA viruses by reducing the intracellular amount of deoxynucleotide triphosphates (dNTPs). It has also been suggested that SAMHD1 negatively regulates interferon (IFN) and the inflammatory responses to viral infections; however, the functions and mechanisms of SAMHD1 in modulating innate immunity are still under study. In our laboratory, we have generated Samhd1-deficient zebrafish larvae using CRISPR-Cas9 and studied its role in the activation of nuclear factor kappa B (NF-κB) and the induction of type I IFN (IFN-I). It was shown that Samhd1 deficiency results in the overactivation of the IFN-I response, assayed as the increased transcript levels of the Interferon Stimulated Genes (ISGs), but only if the larvae were stimulated with suboptimal doses of IFN-I. However, Samhd1-deficient larvae showed robust spontaneous activation of NF-κB, which led to increased larval resistance to Salmonella enterica serovar Typhimurium (STM) infection. Genetic experiments further showed that the activation of NF-κB in macrophages mediated the resistance of Samhd1-deficient larvae against STM. These findings highlight the evolutionary conserved functions of SAMHD1 in the negative regulation of the inflammatory response of vertebrates and reveal, for the first time, a critical role for SAMHD1 in the regulation of NF-κB in macrophages to clear intracellular bacterial infection.

Nanoparticles in Antibacterial Therapy: A Systematic Review of Enhanced Efficacy against Intracellular Bacteria.

Intracellular bacterial infections represent a considerable therapeutic challenge due to the ability of pathogens to invade and replicate within host cells, hampering the action of the immune system and the effectiveness of conventional antibiotics. Bacteria such as Mycobacterium tuberculosis, Listeria monocytogenes, and methicillin-resistant Staphylococcus aureus (MRSA), among others, can persist within host cells, allowing them to evade the immune response and develop resistance to antibacterial treatments. A key factor in the persistence of these infections is the ability of bacteria to enter a dormant state, which reduces their susceptibility to antibiotics that affect the dividing cells. Nanotechnology is emerging as a promising solution as nanoparticle-based systems can improve the intracellular penetration of antibiotics, allow their controlled release, and reduce side effects. This review covers the development and efficacy of nanoparticle-encapsulated antibiotics in models of intracellular infections, highlighting the need to further investigate their potential to overcome the barriers of conventional therapies and improve the treatment of these complex infections.

SLAMF7 and SLAMF8 receptors shape human plasmacytoid dendritic cell responses to intracellular bacteria.

Plasmacytoid dendritic cells (pDCs), professional type I IFN-producing cells, have been implicated in host responses against bacterial infections. However, their role in host defense is debated, and the operating molecular mechanisms are unknown. Certain signaling lymphocyte activation molecule family (SLAMF) members act as microbial sensors and modulate immune functions in response to infection. Here, human blood transcriptomic analyses reveal the involvement of SLAMF7 and SLAMF8 in many infectious diseases, with elevated levels associated with type I IFN responses in salmonellosis and brucellosis patients. We further identify SLAMF7 and SLAMF8 as key regulators of human pDC function. They activate pDC maturation and cytokine production during infection with bacteria that induce acute (Salmonella) or chronic (Brucella) inflammation. SLAMF7 and SLAMF8 signal through NF-κB, IRF7, and STAT-1, and limit mitochondrial ROS accumulation upon Salmonella infection. Remarkably, this SLAMF7/8-dependent control of mitochondrial ROS levels favors bacterial persistence and NF-κB activation. Overall, our results unravel essential shared multifaceted roles of SLAMF7 and SLAMF8 in finely tuning human pDC responses to intracellular bacterial infections with potential for future diagnostic and therapeutic applications.

PH/H2O2 dual-responsive macrophage-targeted chitosaccharides nanoparticles to combat intracellular bacterial infection.

pH/H2O2 dual-responsive macrophage-targeted chitosaccharides nanoparticles to combat intracellular bacterial infection.

Core stability exercises on pain, lumbar and abdominal resistance in patients with brucellosis. Pilot study

Introduction: Brucellosis is a zoonotic intracellular bacterial infection, whose most frequent complications are low back and abdominal pain. In addition, antibiotic therapy against Brucella has side effects that can exacerbate muscular pain in the lumbar area causing a deterioration of mobility and function of the lower extremities. For all these reasons, non-pharmacological interventions through therapeutic exercise are necessary to mitigate them. Our study has evaluated the effects of exercise on pain and resistance of the lumbar and abdominal musculature in patients with brucellosis. Material and method: A prospective, randomized, single-blind clinical trial followed the Consolidated Standards of Reporting Trials (CONSORT) norms. After the screening, 24 patients with brucellosis were randomized to a core stabilization exercise training (CSE) group (n = 15) of the multifidus and transverse abdominal muscles (2 weeks / 3 sessions /10 minutes/day) and a control group (CON) (n = 9) with no training. Pre- and post-CSE testing included endurance of the lumbar and abdominal musculature, using the modified Biering-Sørensen test and abdominal crunch tests. In addition, the visual analog scale (VAS) was used to measure perceived pain in brucellosis patients. Results: The resistance of the abdominal and lumbar musculature increased significantly (P = 0.001) in the CSE group after 2 weeks of training at the baseline and to the CON. In addition, VAS decreased significantly (P = 0.001) in the CSE group with respect to the CON. Conclusion: Our results could indicate that a CSE training program significantly improves the resistance of the lumbar and abdominal musculature and decreases the perception of pain in patients with brucellosis. Therefore, it would be appropriate to recommend CSE protocols during recovery from Brucella infection

GPNMB disrupts SNARE complex assembly to maintain bacterial proliferation within macrophages

Xenophagy plays a crucial role in restraining the growth of intracellular bacteria in macrophages. However, the machinery governing autophagosome‒lysosome fusion during bacterial infection remains incompletely understood. Here, we utilize leprosy, an ideal model for exploring the interactions between host defense mechanisms and bacterial infection. We highlight the glycoprotein nonmetastatic melanoma protein B (GPNMB), which is highly expressed in macrophages from lepromatous leprosy (L-Lep) patients and interferes with xenophagy during bacterial infection. Upon infection, GPNMB interacts with autophagosomal-localized STX17, leading to a reduced N-glycosylation level at N296 of GPNMB. This modification promotes the degradation of SNAP29, thus preventing the assembly of the STX17-SNAP29-VAMP8 SNARE complex. Consequently, the fusion of autophagosomes with lysosomes is disrupted, resulting in inhibited cellular autophagic flux. In addition to Mycobacterium leprae, GPNMB deficiency impairs the proliferation of various intracellular bacteria in human macrophages, suggesting a universal role of GPNMB in intracellular bacterial infection. Furthermore, compared with their counterparts, Gpnmbfl/fl Lyz2-Cre mice presented decreased Mycobacterium marinum amplification. Overall, our study reveals a previously unrecognized role of GPNMB in host antibacterial defense and provides insights into its regulatory mechanism in SNARE complex assembly.

Quaternary ammonium chitosan-functionalized mesoporous silica nanoparticles: A promising targeted drug delivery system for the treatment of intracellular MRSA infection.

Quaternary ammonium chitosan-functionalized mesoporous silica nanoparticles: A promising targeted drug delivery system for the treatment of intracellular MRSA infection.

Self-assembling peptide with dual function of cell penetration and antibacterial as a nano weapon to combat intracellular bacteria.

Intracellular bacterial infections and antimicrobial resistance are threatening global public health systems. Antimicrobial peptides are a potential solution to combat bacterial resistance, but the design of self-assembled nanopeptides with dual functions of cell penetration and antibacterial properties to combat intracellular bacteria remains a challenge. Here, we propose a strategy to develop self-assembled nanopeptides with dual functions through the chimerization of self-assembled core, hydrophobic motif, and cell-permeable unit. The optimal nanopeptides, F3FT and N3FT, exhibited potent antibacterial activity and excellent biocompatibility. Crucially, F3FT and N3FT are able to efficiently penetrate cells and eliminate intracellular bacteria and sniping inflammation. Moreover, F3FT and N3FT kill bacteria mainly by disrupting bacterial cell membranes and inducing excessive accumulation of reactive oxygen species. F3FT and N3FT have exhibited good safety and potent therapeutic potential in vivo. This scheme of constructing nanopeptides through multifunctional domains design provides a paradigm for dealing with escalating of intracellular bacteria and antimicrobial resistance.

FcγRI plays a pro-inflammatory role in the immune response to Chlamydia respiratory infection by upregulating dendritic cell-related genes.

FcγRI plays a pro-inflammatory role in the immune response to Chlamydia respiratory infection by upregulating dendritic cell-related genes.

Executioner caspases degrade essential mediators of pathogen-host interactions to inhibit growth of intracellular Listeria monocytogenes

Cell death mediated by executioner caspases is essential during organ development and for organismal homeostasis. The mechanistic role of activated executioner caspases in antibacterial defense during infections with intracellular bacteria, such as Listeria monocytogenes, remains elusive. Cell death upon intracellular bacterial infections is considered altruistic to deprive the pathogens of their protective niche. To establish infections in a human host, Listeria monocytogenes deploy virulence mediators, including membranolytic listeriolysin O (LLO) and the invasion associated protein p60 (Iap), allowing phagosomal escape, intracellular replication and cell-to-cell spread. Here, by means of chemical and genetical modifications, we show that the executioner caspases-3 and -7 efficiently inhibit growth of intracellular Listeria monocytogenes in host cells. Comprehensive proteomics revealed multiple caspase-3 substrates in the Listeria secretome, including LLO, Iap and various other proteins crucially involved in pathogen-host interactions. Listeria secreting caspase-uncleavable LLO or Iap gained significant growth advantage in epithelial cells. With that, we uncovered an underappreciated defense barrier and a non-canonical role of executioner caspases to degrade virulence mediators, thus impairing intracellular Listeria growth.