Outer Membrane Vesicles (OMVs) of Gram-negative Bacteria: A Perspective Update

Listeria monocytogenes and Listeriosis: The Global Enigma

Listeria monocytogenes is an intracellular, Gram-positive, non-spore-forming, non-encapsulated, facultative anaerobic, rod-shaped, and psychrotrophic food-borne pathogen that causes the infection, listeriosis, thus it attracts great attention following listeriosis outbreaks, which are often associated with high mortality rates. The prevalence of listeriosis is quite low globally; however, the most recent and deadliest outbreak occurred in South Africa, during which 216 persons lost their lives. L. monocytogenes is endowed with the potential to multiply through a wide range of harsh environmental conditions, forming biofilms on varying surfaces in the food industry, as well as having persistent and antibiotic-resistant cells, which pose a major threat and burden to the ready-to-eat food industry. A more frustrating characteristic of this bacterium is its strain divergence, alongside an increased level of antibiotic resistance registered among the strains of L. monocytogenes recovered from food, humans, and environmental sources, especially to those antibiotics involved in the treatment of human listeriosis. Antibiotic resistance exerted by and among pathogenic food-borne microbes is an ongoing public health menace that continues to be an issue. Against this background, a thorough search into different databases using various search engines was performed, which led to the gathering of salient information that was organised, chronologically, based on Listeria monocytogenes and listeriosis. Altogether, the findings elaborated in this study present up-to date knowledge on different aspects of this pathogen which will improve our understanding of the mystery associated with it and the ways to prevent and control its dissemination through ready-to-eat foods. In addition, constant monitoring of the antibiotic resistance profiles of strains of L. monocytogenes from varying sources detected changes, giving an update on the trend in antibiotic resistance. Overall, monitoring of bacterial contamination serves as the key aspect in the control of the food safety output in the food industry.

Avibacterium paragallinarum, the Causative Agent of Infectious Coryza: A Comprehensive Review

Infectious coryza (IC) caused by Avibacterium paragallinarum (AP) has risen in importance as a poultry disease over the past several years because of its increased incidence in commercial poultry in both Europe and the United States. Because of this rise in importance, more attention has been focused on diagnosis, isolation, and surveillance of this bacterial pathogen. As a result, new knowledge has been produced and published. This review was compiled with the main purpose of summarizing and presenting the updated knowledge available about AP. However, the new knowledge can only be understood in the context of previously known facts about the disease. Therefore, this review has been organized in two major parts. The first part is a review of the established knowledge about AP, followed by recent updates. In the first part, we summarize the established well-known as well as some of the less-known facts and literature about AP. The second section focuses on specifics of the latest IC outbreaks in commercial poultry in northern latitudes, particularly in Europe and in North America. Additionally, we reviewed the current geographical distribution of the disease in Asia, South America, and Africa. The crises created by emerging or re-emerging disease outbreaks ignite interest in understanding the disease and pathogen in order to combat it properly. This results in new knowledge that improves the understanding of the disease features, leading to improved disease prevention, control, and eradication. Although knowledge about AP has advanced, knowledge gaps about the disease still persist. Therefore, this review concludes with summarizing the current knowledge gaps as well as potential areas for future research.

Outer membrane vesicles in gram-negative bacteria and its correlation with pathogenesis

There is a widespread distribution of gram-negative bacteria worldwide, which are responsible for the deaths of numerous patients each year. The illnesses they cause can be localized and systemic, and these bacteria possess several key virulence factors that contribute to their pathogenicity. In recent years, several distinct mechanisms of pathogenesis have evolved that remain largely unknown to scientists and medical experts. Among these, outer membrane vesicles (OMVs) are undoubtedly one of the most significant factors influencing virulence. OMVs contain various bacterial compounds and can have diverse effects on host organisms and the immune system, potentially exacerbating disease and inflammation while evading immune responses. This review comprehensively examines the role of OMVs in bacterial pathogenesis, their interaction with host cells, and their potential biomedical applications. Understanding the molecular mechanisms governing OMV biogenesis and function could pave the way for novel antimicrobial strategies and therapeutic interventions.

Spatially resolved charge-transfer kinetics at the quantum dot-microbe interface using fluorescence lifetime imaging microscopy

Integrating the optoelectronic properties of quantum dots (QDs) with biological enzymatic systems to form microbe-semiconductor biohybrids offers promising prospects for both solar-to-chemical conversion and light-modulated biochemical processes. Developing these nano-bio hybrid systems necessitates a deep understanding of charge-transfer dynamics at the nano-bio interface. Photoexcited carrier transfer from QDs to microbes is driven by complex interactions, with emerging insights into the relevant thermodynamic and kinetic factors. The heterogeneities of both microbes and QD ensembles pose significant challenges in mechanistic understanding, which is critical for designing advanced nano-bio hybrids. We used fluorescence lifetime imaging microscopy to analyze charge transfer between a CdSe QD film and Shewanella oneidensis microbes. We correlated the spatiotemporal fluorescence data with an analytical model. Our analysis revealed two distinct distributions of QD de-excitation pathways. The characteristics of these distributions: 1) a faster transfer rate ([Formula: see text]), with a lower acceptor number ([Formula: see text]) and 2) a slower transfer rate ([Formula: see text]) with a higher acceptor number ([Formula: see text]). We assign these distributions to the indirect and direct electron transfer mechanisms, respectively. Our findings demonstrate how spectroscopic imaging can uncover fundamental electron transfer mechanisms at complex interfaces, offering valuable design principles for future nano-bio hybrids.

Recent Progress in Developing Extracellular Vesicles as Nanovehicles to Deliver Carbohydrate-Based Therapeutics and Vaccines

Cell-derived, nanoscale extracellular vesicles (EVs) have emerged as promising tools in diagnostic, therapeutic, and vaccine applications. Their unique properties including the capability to encapsulate diverse molecular cargo as well as the versatility in surface functionalization make them ideal candidates for safe and effective vehicles to deliver a range of biomolecules including gene editing cassettes, therapeutic proteins, glycans, and glycoconjugate vaccines. In this review, we discuss recent advances in the development of EVs derived from mammalian and bacterial cells for use in a delivery of carbohydrate-based protein therapeutics and vaccines. We highlight key innovations in EVs' molecular design, characterization, and deployment for treating diseases including Alzheimer's disease, infectious diseases, and cancers. We discuss challenges for their clinical translation and provide perspectives for future development of EVs within biopharmaceutical research and the clinical translation landscape.

BT1549 coordinates the in vitro IL-10 inducing activity of Bacteroides thetaiotaomicron

The intestine is home to a complex immune system that is engaged in mutualistic interactions with the microbiome that maintain intestinal homeostasis. A variety of immune-derived anti-inflammatory mediators have been uncovered and shown to be critical for maintaining these beneficial immune-microbiome relationships. Notably, the gut microbiome actively invokes the induction of anti-inflammatory pathways that limit the development of microbiome-targeted inflammatory immune responses. Despite the importance of this microbiome-driven immunomodulation, detailed knowledge of the microbial factors that promote these responses remains limited. We have previously established that the gut symbiont Bacteroides thetaiotaomicron stimulates the production of the anti-inflammatory cytokine IL-10 via soluble factors in a Toll-like receptor 2 (TLR2)-MyD88-dependent manner. Here, using TLR2 activity reporter cell lines, we show that the capacity of B. thetaiotaomicron to stimulate TLR2 activity was not critically dependent on either of the canonical heterodimeric forms of TLR2, TLR2/TLR1, or TLR2/TLR6, that typically mediate its function. Furthermore, biochemical manipulation of B. thetaiotaomicron-conditioned media suggests that IL-10 induction is mediated by a protease-resistant or non-proteogenic factor. We next uncovered that deletion of gene BT1549, a predicted secreted lipoprotein, significantly impaired the capacity of B. thetaiotaomicron to induce IL-10, while complementation in trans restored IL-10 induction, suggesting a role for BT1549 in the immunomodulatory function of B. thetaiotaomicron. Collectively, these data provide molecular insight into the pathways through which B. thetaiotaomicron operates to promote intestinal immune tolerance and symbiosis.

IMPORTANCE

Intestinal homeostasis requires the establishment of peaceful interactions between the gut microbiome and the intestinal immune system. Members of the gut microbiome, like the symbiont Bacteroides thetaiotaomicron, actively induce anti-inflammatory immune responses to maintain mutualistic relationships with the host. Despite the importance of such interactions, the specific microbial factors responsible remain largely unknown. Here, we show that B. thetaiotaomicron, which stimulates Toll-like receptor 2 (TLR2) to drive IL-10 production, can stimulate TLR2 independently of TLR1 or TLR6, the two known TLR that can form heterodimers with TLR2 to mediate TLR2-dependent responses. Furthermore, we show that IL-10 induction is likely mediated by a protease-resistant or non-proteogenic factor, and that this requires gene BT1549, a predicted secreted lipoprotein and peptidase. Collectively, our work provides insight into the molecular dialog through which B. thetaiotaomicron coordinates anti-inflammatory immune responses. This knowledge may facilitate future strategies to promote such responses for therapeutic purposes.

Inhibiting NLRP3 enhances cellular autophagy induced by outer membrane vesicles from Pseudomonas aeruginosa

The bacterium Pseudomonas aeruginosa is able to invade lung epithelial cells and survive intracellularly. During this process, it secretes outer membrane vesicles (OMVs), however, it is currently unclear how OMVs from P. aeruginosa (PA-OMVs) affect lung epithelial cells and their impact on oxidative stress, autophagy, and other physiological activities of lung epithelial cells. In this study, we found that PA-OMVs activated oxidative stress and autophagy in cells. We demonstrated that the NLRP3 (NLR family, pyrin domain containing 3) inhibitor MCC950 can enhance autophagy induced by PA-OMVs. The main function of NLRP3 is related to the body's immune response and inflammation regulation. MCC950 is the most common inhibitor of NLRP3. Additionally, we showed that PA-OMVs not only enhanced the expression of AMP-activated protein kinase, a key regulator of cellular energy homeostasis, and reactive oxygen species, which play a crucial role in cellular signaling and oxidative stress, but also significantly enhanced the expression of NLRP3. Inhibiting the expression of NLRP3 further enhanced the process of PA-OMVs induced autophagy. These results demonstrate that PA-OMVs activate both autophagy and the NLRP3 inflammasome, with NLRP3 suppressing autophagy to a certain extent, hoping to provide broad ideas for the future applications of PA-OMVs.IMPORTANCEThe discovery that lung epithelial cells exposed to outer membrane vesicles from Pseudomonas aeruginosa (PA-OMVs) activate cellular autophagy and induce protective immunity is significant. Specifically, the addition of an NLRP3 inhibitor, MCC950, has been found to decrease NLRP3 targets while simultaneously enhancing the autophagy activity induced by PA-OMVs. This finding unveils a novel theoretical framework for the development of PA-OMVs vaccines, highlighting new targets for enhancing the body's anti-infective responses. By elucidating the mechanisms through which PA-OMVs trigger autophagy and bolster immune defenses, this research opens avenues for innovative vaccine design strategies aimed at combatting infections effectively.

The role and mechanisms of Helicobacter pylori outer membrane vesicles in the pathogenesis of extra-gastrointestinal diseases

Helicobacter pylori (H. pylori) infection have been closely associated with several extra-gastrointestinal disorders. Outer membrane vesicles (OMVs), as lipid-membrane-bounded nanoparticles, are usually shed from Gram-negative both in vitro and in vivo. H. pylori is also capable of producing OMVs, which can enter the systemic circulation and be delivered to various cells, tissues or organs, eliciting a range of inflammatory and immune modulation responses. In this current review, we summarize the biogenesis and functions of H. pylori OMVs, describe the contribution of H. pylori OMVs to the generation and progression of extra-gastrointestinal diseases, such as neuronal damage, Alzheimer disease, hepatic fibrosis and atherosclerosis. We also explored the effect of H. pylori OMVs in inflammatory and immune modulation of diverse immune cells, including macrophages, mononuclear cells and dendritic cells. By elucidating the molecular mechanism of H. pylori OMVs-mediated extra-gastrointestinal diseases and immunomodulatory effect, it may promote the development of efficient treatments and vaccinations against H. pylori.

Lipopolysaccharide, arbiter of the gut-liver axis, modulates hepatic cell pathophysiology in alcoholism

Over the last four decades, clinical research and experimental studies have established that lipopolysaccharide (LPS)-a component of the outer membrane of gram-negative bacteria-is a potent hepatotoxic molecule in humans and animals. Alcohol abuse is commonly associated with LPS endotoxemia. This review highlights LPS molecular structures and modes of release from bacteria, plasma LPS concentrations, induction of microbiota dysbiosis, disruption of gut epithelial barrier, and translocation of LPS into the portal circulation impacting the pathophysiology of hepatic cells via the gut-liver axis. We describe and illustrate the portal vein circulation and its distributaries draining the gastrointestinal tract. We also elaborate on the gut-liver axis coupled with enterohepatic circulation that represents a bidirectional communication between the gut and liver. The review also updates the data on how circulating LPS is cleared in a coordinated effort between Kupffer cells, hepatocytes, and liver sinusoidal endothelial cells. Significantly, the article reviews and updates the modes/mechanisms of action by which LPS mediates the diverse pathophysiology of Kupffer cells, hepatocytes, sinusoidal endothelial cells, and hepatic stellate cells primarily in association with alcohol consumption. Specifically, we review the intricate linkages between ethanol, microbiota dysbiosis, LPS production, gut-liver axis, and pathophysiology of various hepatic cells. The maintenance of the gut barrier structural and functional integrity and microbiome homeostasis is essential in mitigating alcoholic liver disease and improving liver health.

Pivotal role of Helicobacter pylori virulence genes in pathogenicity and vaccine development

One of the most prevalent human infections is Helicobacter pylori (H. pylori), which affects more than half of the global population. Although H. pylori infections are widespread, only a minority of individuals develop severe gastroduodenal disorders. The global resistance of H. pylori to antibiotics has reached concerning levels, significantly impacting the effectiveness of treatment. Consequently, the development of vaccines targeting virulence factors may present a viable alternative for the treatment and prevention of H. pylori infections. This review aims to provide a comprehensive overview of the current understanding of H. pylori infection, with a particular focus on its virulence factors, pathophysiology, and vaccination strategies. This review discusses various virulence factors associated with H. pylori, such as cytotoxin-associated gene A (cagA), vacuolating cytotoxin gene (vacA), outer membrane proteins (OMPs), neutrophil-activated protein (NAP), urease (ure), and catalase. The development of vaccines based on these virulence characteristics is essential for controlling infection and ensuring long-lasting protection. Various vaccination strategies and formulations have been tested in animal models; however, their effectiveness and reproducibility in humans remain uncertain. Different types of vaccines, including vector-based vaccines, inactivated whole cells, genetically modified protein-based subunits, and multiepitope nucleic acid (DNA) vaccines, have been explored. While some vaccines have demonstrated promising results in murine models, only a limited number have been successfully tested in humans. This article provides a thorough evaluation of recent research on H. pylori virulence genes and vaccination methods, offering valuable insights for future strategies to address this global health challenge.

Innovative Strategies in Oncology: Bacterial Membrane Vesicle-Based Drug Delivery Systems for Cancer Diagnosis and Therapy

Outer membrane vesicles (OMVs) are double-layered structures of nanoscale lipids released by gram-negative bacteria. They have the same membrane composition and characteristics as primitive cells, which enables them to penetrate cells and tissues efficiently. These OMVs exhibit excellent membrane stability, immunogenicity, safety, and permeability (which makes it easier for them to penetrate into tumour tissue), making them suitable for developing cancer vaccines and drug delivery systems. Recent studies have focused on engineering OMVs to enhance tumour-targeting capabilities, reduce toxicity, and extend circulation time in vivo. This article reviews the latest progress in OMV engineering for tumour treatment and discusses the challenges associated with the use of OMV-based antitumour therapy in clinical practice.

Opportunities and challenges of bacterial extracellular vesicles in regenerative medicine

Extracellular vesicles (EVs) are membrane-bound vesicles that are shed or secreted from the cell membrane and enveloped by a lipid bilayer. They possess stability, low immunogenicity, and non-cytotoxicity, exhibiting extensive prospects in regenerative medicine (RM). However, natural EVs pose challenges, such as insufficient targeting capabilities, potential biosafety concerns, and limited acquisition pathways. Although engineered EVs demonstrate excellent therapeutic efficacy, challenges such as low production yield and the complexity of engineering modifications constrain their further clinical applications. Bacteria have advantages such as rapid proliferation, diverse gene editing methods, mature cultivation techniques, and relatively easy preparation of bacterial EVs (BEVs), which can be used to effectively address the challenges currently encountered in the field of EVs. This review provides a description of the biogenesis and pathophysiological functions of BEVs, and strategies for optimizing BEVs preparation to attain efficiency and safety are discussed. An analysis of natural characteristics of BEVs is also conducted to explore how to leverage their advantages or mitigate their limitations, thereby overcoming constraints on the application of BEVs in RM. In summary, engineered BEVs possess characteristics such as high production yield, excellent stability, and high drug-delivering capabilities, laying the foundation for their application in RM.

Foodborne Infections and Salmonella: Current Primary Prevention Tools and Future Perspectives

Salmonella is considered the major zoonotic and foodborne pathogen responsible for human infections. It includes the serovars causing typhoid fever (S. typhi and S. paratyphi) and the non-typhoidal salmonella (NTS) serovars (S. enteritidis and S. typhimurium), causing enteric infections known as "Salmonellosis". NTS represents a major public health burden worldwide. The consumption of S. enteritidis-contaminated animal foods is the main source of this disease in humans, and eradicating bacteria from animals remains a challenge. NTS causes various clinical manifestations, depending on the quantity of bacteria present in the food and the immune status of the infected individual, ranging from localized, self-limiting gastroenteritis to more serious systemic infections. Salmonellosis prevention is based on hygienic and behavioral rules related to food handling that aim to reduce the risk of infection. However, no vaccine against NTS is available for human use. This aspect, in addition to the increase in multidrug-resistant strains and the high morbidity, mortality, and socioeconomic costs of NTS-related diseases, makes the development of new prevention and control strategies urgently needed. The success of the vaccines used to protect against S. typhi encouraged the development of NTS vaccine candidates, including live attenuated, subunit-based, and recombinant-protein-based vaccines. In this review, we discuss the epidemiological burden of Salmonellosis and its primary prevention, focusing on the current status and future perspectives of the vaccines against NTS.

An improvised one-step OptiPrep cushion ultracentrifugation method for outer membrane vesicles isolation of Klebsiella pneumoniae

BACKGROUND

Extracellular vesicles (EVs) play a crucial role in intraspecies and interspecies communication, significantly influencing physiological and pathological processes. Outer membrane vesicles (OMVs) secreted by Gram-negative bacteria are rich in components from the parent cells and are important for bacterial communication, immune evasion, and pathogenic mechanisms. However, the extraction and purification of OMVs face numerous challenges due to their small size and heterogeneity.

RESULTS

This study proposes an innovative strategy that combines traditional differential centrifugation (DC) with one-step ultracentrifugation (ODG) to develop a dual differential gradient centrifugation (DDGC) method for extracting outer membrane vesicles from Klebsiella pneumoniae. By comparing the DC and DDGC extraction methods, we found that OMVs extracted by DDGC exhibited more typical morphology, clearer backgrounds, and more uniform particle size distribution. The lipid polysaccharide (LPS) content in OMVs extracted by DDGC was significantly higher than that obtained by DC, and the outer membrane protein content was also greater, demonstrating enhanced biological activity. Biological activity assays indicated that OMVs extracted by DDGC showed stronger cytotoxicity to A549 lung epithelial cells, a significant decrease in cell viability, and higher levels of inflammatory factor expression(IL-6, TNF-α, IL-1β, and IL-8).

CONCLUSION

Our study demonstrates the advantages of the DDGC method in extracting K. pneumoniae OMVs, showing improvements in morphology, particle size distribution, protein content, and biological activity. This provides a solid foundation for further exploration of the biological functions of OMVs and their potential applications in the biomedical field.

Anti-inflammatory Effects of Membrane Vesicles from Eubacterium rectale via the NLRP3 Signal Pathway

Eubacterium rectale (E. rectale) has the ability to attenuate systemic and intestinal inflammation. Its naturally secreted membrane vesicles (MVs) likely play a crucial role in this process. The objective of this study is to investigate the anti-inflammatory effects of E. rectale and its membrane vesicles (MVs). An inflammation model was established by inducing an inflammatory response in Raw 264.7 cells using lipopolysaccharide (LPS). Subsequently, the cells were pre-treated with E. rectale and its MVs, and the expression levels of IL-1β, IL-6, TNF-α, and IL-10 in the cells were then detected using RT-qPCR. ELISA was used to measure the secretion levels of IL-1β, while western blot analysis was employed to assess the expression of key proteins in the IL-1β pathway, specifically ASC, Caspase 1, and NLRP3. The results revealed that both E. rectale and its MVs significantly reduced the expression of the inflammatory cytokines IL-1β and TNF-α in Raw 264.7 cells, which were induced by LPS. Additionally, they markedly upregulated the expression of the anti-inflammatory cytokine IL-10 and suppressed IL-1β expression via the NLRP3-Caspase 1-ASC signaling pathway. These findings suggest that E. rectale, through its membrane vesicles, can attenuate LPS-induced NLRP3 inflammasome activation, thereby mitigating the inflammatory response in Raw 264.7 cells.

Genetically surface-modified Escherichia coli outer membrane vesicles targeting MUC1 antigen in cancer cells

Outer membrane vesicles (OMVs), non-replicating spherical liposomes derived from Gram-negative bacteria, are a promising vaccine platform and multifunctional delivery systems. Their ability to be modified via genetic engineering for the incorporation and display of heterologous proteins enhances their functionality. In this study, we demonstrated a bio-ligation approach to display single-chain variable fragments (scFv) on the OMV surface using the SpyTag/SpyCatcher system. SpyTag-fused scFv, expressed by mammalian cells, bound to OMVs with SpyCatcher-fused Lpp'OmpA after a simple incubation. Biophysical analysis indicated that the conjugated OMVs maintained their physicochemical properties. We used an scFv targeting mucin 1 protein (MUC1) for specific cell targeting. Confocal microscopy revealed that conjugated OMVs specifically bound to and were internalized by MUC1-presenting cells, but not by MUC1-deficient cells. In conclusion, this rapid and efficient bio-ligation system facilitates the display of functional scFv on OMV surfaces, offering a promising approach for targeted delivery to MUC1-expressing cancer cells.

Adjuvants for Helicobacter pylori vaccines: Outer membrane vesicles provide an alternative strategy

Helicobacter pylori (H. pylori) is a gram-negative, spiral-shaped bacterium that colonizes the human stomach, leading to various gastric diseases. The efficacy of traditional treatments, such as bismuth-based triple and quadruple therapies, has been reduced due to increasing antibiotic resistance and drug toxicity. As a result, the development of effective vaccines was proposed to control H. pylori-induced infections; however, one of the primary challenges is the lack of potent adjuvants. Although various adjuvants, both toxic (e.g. cholera toxin and Escherichia coli heat-labile toxin) and non-toxic (e.g. aluminum and propolis), have been tested for vaccine development, no clinically favorable adjuvants have been identified due to high toxicity, weak immunostimulatory effects, inability to elicit specific immune responses, or latent side effects. Outer membrane vesicles (OMVs), mainly secreted by gram-negative bacteria, have emerged as promising candidates for H. pylori vaccine adjuvants due to their potential applications. OMVs enhance mucosal immunity and Th1 and Th17 cell responses, which have been recognized to have protective effects and guarantee safety and efficacy. The development of an effective vaccine against H. pylori infection is ongoing, with clinical trials expected in the future.

Coassembly of Cell-Penetrating Peptide Octaarginine with Acetazolamide: Emergent Interactions with E. coli

The investigation of established pharmaceutical agents for recalibrating usage strongly supplements new drug development. In this work, we have prepared coassembled complexes of acetazolamide (AZM) with the cationic peptide octaarginine (R8) in an attempt to enhance its potency and scope of use. R8 and AZM in different weight ratios coassemble into remarkable nano- and microstructures such as ribbons, sheets, and stick-like structures. A combination of FTIR, XRD, SEM, and DSC has been used to characterize the R8:AZM coassemblies. The sulfonamide SO2 and NH2 groups of AZM are associated with the guanidinium amine, free amine, and terminal carbonyl groups of R8 resulting in distinctive topologies. Treatment of Escherichia coli with the complexes results in a distinctive pattern of membrane disruption and pore formation. The R8:AZM coassemblies inhibit carbonic anhydrase and E. coli growth with greater efficiency compared to bare AZM. The 1:5 w/w complex leads to pronounced outer and inner membrane rupture and significantly restricts glucose uptake by E. coli. The ability of R8 and AZM to coassemble into a distinctive set of structures based solely on differences in their relative proportions and their engagement with E. coli as more than the sum of their parts are novel facets of R8 and AZM behavior and underscore a straightforward and elegant approach for enhancing the scope of use of small molecule drugs.

Stannous fluoride protects gingival keratinocytes against infection and oxidative stress by Porphyromonas gingivalis outer membrane vesicles

Objective

To determine whether outer membrane vesicles (OMVs) of the periodontal pathogen Porphyromonas gingivalis (P. gingivalis) can infect gingival keratinocytes and stimulate reactive oxygen species (ROS) production, and to assess whether stannous fluoride (SnF2), stannous chloride (SnCl2) or 0.454% SnF2 toothpaste diluents can inhibit OMV infection.

Methods

OMVs were isolated from P. gingivalis culture and their morphology was characterized using scanning electron microscopy and transmission electron microscopy. OMVs were harvested, separated from parent bacteria, labeled with fluorescent probes, and added to proliferating gingival keratinocytes. Infection was monitored by measuring uptake of fluorescence. Free radicals and ROS were quantified by adding a separate CellROX fluorescent probe following 24 h incubation with OMVs, and automated fluorescence imaging was used to assess ROS generation rates. A dose response range of SnF2 and SnCl2 concentrations as well as 0.454% SnF2 toothpaste dilutions were added to OMVs to examine their potential to neutralize OMV infectivity and protect gingival keratinocytes from development of oxidative stress. The mechanism of SnF2 inhibition of OMV infection was studied by binding SnF2 with purified lipopolysaccharides (LPS) from the bacterial culture and examining the binding of stannous to LPS using mass spectrometry.

Results

Large numbers of OMVs were formed in P. gingivalis culture medium. They were purified along with isolating soluble LPS. Fluorescence imaging revealed that OMVs infected gingival keratinocytes and promoted oxidative stress in a dose-dependent manner. SnF2, SnCl2, and SnF2 toothpaste inhibited OMV infectivity (p < 0.05) and likewise protected gingival keratinocytes from oxidative stress (p < 0.05). Stannous precipitated LPS and OMVs from solution, forming insoluble aggregates easily isolated by centrifugation. Mass spectroscopic analysis revealed that stannous was bound to LPS in a one-to-one molecular equivalent ratio.

Conclusion

SnF2 not only kills bacteria, but also inhibits bacterial virulence factors, such as LPS and OMVs. SnF2, SnCl2 and stannous-containing toothpastes can precipitate OMVs and LPS to in principle protect gingival keratinocyte cells from infection leading to inflammation and oxidative stress.

Impact of probiotics-derived extracellular vesicles on livestock gut barrier function

Probiotic extracellular vesicles (pEVs) are biologically active nanoparticle structures that can regulate the intestinal tract through direct or indirect mechanisms. They enhance the intestinal barrier function in livestock and poultry and help alleviate intestinal diseases. The specific effects of pEVs depend on their internal functional components, including nucleic acids, proteins, lipids, and other substances. This paper presents a narrative review of the impact of pEVs on the intestinal barrier across various segments of the intestinal tract, exploring their mechanisms of action while highlighting the limitations of current research. Investigating the mechanisms through which probiotics operate via pEVs could deepen our understanding and provide a theoretical foundation for their application in livestock production.

Engineering Planar Gram-Negative Outer Membrane Mimics Using Bacterial Outer Membrane Vesicles

Antibiotic resistance is a major challenge in modern medicine. The unique double membrane structure of Gram-negative bacteria limits the efficacy of many existing antibiotics and adds complexity to antibiotic development by limiting transport of antibiotics to the bacterial cytosol. New methods to mimic this barrier would enable high-throughput studies for antibiotic development. In this study, we introduce an innovative approach to modify outer membrane vesicles (OMVs) from Aggregatibacter actinomycetemcomitans, to generate planar supported lipid bilayer membranes. Our method first involves the incorporation of synthetic lipids into OMVs using a rapid freeze-thaw technique to form outer membrane hybrid vesicles (OM-Hybrids). Subsequently, these OM-Hybrids can spontaneously rupture when in contact with SiO2 surfaces to form a planar outer membrane supported bilayer (OM-SB). We assessed the formation of OM-Hybrids using dynamic light scattering and a fluorescence quenching assay. To analyze the formation of OM-SBs from OM-Hybrids we used quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence recovery after photobleaching (FRAP). Additionally, we conducted assays to detect surface-associated DNA and proteins on OM-SBs. The interaction of an antimicrobial peptide, polymyxin B, with the OM-SBs was also assessed. These findings emphasize the capability of our platform to produce planar surfaces of bacterial outer membranes, which in turn, could function as a valuable tool for streamlining the development of antibiotics.

Prokaryotic morphological features and maintenance activities governed by seasonal productivity conditions

Prokaryotic maintenance respiration and associated metabolic activities constitute a considerable proportion of the total respiration of carbon to CO2 in the ocean's mixed layer. However, seasonal influences on prokaryotic maintenance activities in terms of morphological and metabolic adaptations at low (winter) and high productivity (summer) are still unclear. To address this, we examined the natural prokaryotic communities at the mesocosm scale to analyse the differences in their morphological features and gene expression at low and high maintenance respiration, experimentally manipulated with the specific growth rate. Here, we showed that morphological features including membrane blebbing, membrane vesicles, and cell‒cell connections occurred under high productivity. Metabolic adaptations associated with maintenance activities were observed under low productivity. Several Kyoto Encyclopedia of Genes and Genomes categories related to signal transduction, energy metabolism, and translational machinery supported maintenance activities under simulated winter conditions. Differential abundances of genes related to transporters, osmoregulation, nitrogen metabolism, ribosome biogenesis, and cold stress were observed. Our results demonstrate how specific growth rate in different seasons can influence resource allocation at the levels of morphological features and metabolic adaptations. This motivates further study of morphological features and their ecological role during high productivity, while investigations of metabolic adaptations during low productivity can advance our knowledge about maintenance activities.

Mechanisms of antimicrobial resistance in biofilms

Most bacteria in nature exist in aggregated communities known as biofilms, and cells within a biofilm demonstrate major physiological changes compared to their planktonic counterparts. Biofilms are associated with many different types of infections which can have severe impacts on patients. Infections involving a biofilm component are often chronic and highly recalcitrant to antibiotic therapy as a result of intrinsic physical factors including extracellular matrix production, low growth rates, altered antibiotic target production and efficient exchange of resistance genes. This review describes the biofilm lifecycle, phenotypic characteristics of a biofilm, and contribution of matrix and persister cells to biofilms intrinsic tolerance to antimicrobials. We also describe how biofilms can evolve antibiotic resistance and transfer resistance genes within biofilms. Multispecies biofilms and the impacts of various interactions, including cooperation and competition, between species on tolerance to antimicrobials in polymicrobial biofilm communities are also discussed.

Evaluation of the efficiency of various methods to load fluoroquinolones into Escherichia coli outer membrane vesicles as a novel antibiotic delivery platform

The development of novel antibacterial agents that are effective against Gram-negative bacteria is limited primarily by transport issues. This class of bacteria maintains a complex cell envelope consisting of two membrane bilayers, preventing the passage of most antibiotics. These drugs must therefore pass through protein channels called porins; however, many antibiotics are too large to pass through porins, and a common mechanism of acquired resistance is down-regulation of porins. To overcome this transport limitation, we have proposed the use of outer membrane vesicles (OMVs), released by Gram-negative bacteria, which deliver cargo to other bacterial cells in a porin-independent manner. In this work, we systematically studied the ability to load fluoroquinolones into purified Escherichia coli OMVs using in vivo and in vitro passive loading methods, and active loading methods such as electroporation and sonication. We observed limited loading of all of the antibiotics using passive loading techniques; sonication and electroporation significantly increased the loading, with electroporation at low voltages (200 and 400V) resulting in the greatest encapsulation efficiencies. We also demonstrated that imipenem, a carbapenem antibiotic, can be readily loaded into OMVs, and its administration via OMVs increases the effectiveness of the drug against E. coli. Our results demonstrate that small molecule antibiotics can be readily incorporated into OMVs to create novel delivery vehicles to improve antibiotic activity.

A comprehensive in silico analysis of putative outer membrane and secretory hydrolases from the pathogenic Leptospira: Possible implications in pathogenesis

Outer surface/membrane and virulent secretory proteins are primarily crucial for pathogenesis. Secreted and outer membrane hydrolases of many pathogens play an important role in attenuating the host immune system. Leptospira expresses many such proteins, and few have been characterized to display various roles, including host immune evasion. However, identification, classification, characterization, and elucidation of the possible role of Leptospira's outer membrane and secretory hydrolases have yet to be explored. In the present study, we used bioinformatics tools to predict exported proteins from the pathogenic Leptospira proteome. Moreover, we focused on secretory and outer membrane putative hydrolases from the exported proteins to generate a deeper understanding. Our analysis yielded four putative outer/secretory hydrolases, LIC_10995, LIC_11183, LIC_11463, and LIC_12988, containing α/β hydrolase fold and displayed similarity with lipase motif. Moreover, their conservation analysis of the predicted hydrolases across the spectrum of different Leptospira species showed high clustering with the pathogenic species. Outer membrane and secretory proteins with lipolytic activity may have a role in pathogenesis. This is the first bioinformatics analysis of secretory and outer membrane α/β hydrolases from leptospiral species. However, experimental studies are indeed required to unravel this possibility.

Evaluation of the effect of Helicobacter pylori -derived OMVs and released exosomes from stomach cells treated with OMVs on the expression of genes related to the TGF-β/SMAD signaling pathway in hepatocellular carcinoma

OMVs derived from Helicobacter pylori can lead to cell transformation in gastric epithelium and cancer. Additionally, exosomes (Exos) released by host cells infected with H. pylori can significantly contribute to the development of diseases such as cancer. In this study, the effects of both Exos from AGS cells treated with H. pylori-derived OMVs on the expression of genes related to the TGF-β/SMAD signaling pathway in hepatocellular carcinoma (HCC) cells were investigated. The TGF-β/SMAD pathway is one of the most important pathways that regulate the development and progression of HCC. For this purpose, after treating HepG2 cells with H. pylori-derived OMVs (directly) and Exos from AGS cells treated with H. pylori-derived OMVs (indirectly), the expression levels of TGF-β, SMAD2, SMAD3, SMAD4, and ERK genes were analyzed using Real-time PCR. The findings showed that OMVs derived from H. pylori can significantly increase the expression of genes involved in the TGF-β signaling pathway, which can affect the aggressive behavior of HepG2 cells. Additionally, exosomes secreted from AGS cells or AGS cells treated with OMVs had no effect on changing the expression of the studied genes. Therefore, only the OMVs released from H. pylori can affect the TGF-β/SMAD signaling pathway in HCC cells.

An in-depth exploration of the multifaceted roles of EVs in the context of pathogenic single-cell microorganisms

SUMMARYExtracellular vesicles (EVs) have been recognized throughout scientific communities as potential vehicles of intercellular communication in both eukaryotes and prokaryotes, thereby influencing various physiological and pathological functions of both parent and recipient cells. This review provides an in-depth exploration of the multifaceted roles of EVs in the context of bacteria and protozoan parasite EVs, shedding light on their contributions to physiological processes and disease pathogenesis. These studies highlight EVs as a conserved mechanism of cellular communication, which may lead us to important breakthroughs in our understanding of infection, mechanisms of pathogenesis, and as indicators of disease. Furthermore, EVs are involved in host-microbe interactions, offering insights into the strategies employed by bacteria and protozoan parasites to modulate host responses, evade the immune system, and establish infections.

Characterisation and Immunogenicity of Neisseria cinerea outer membrane vesicles displaying NadA, NHBA and fHbp from Neisseria meningitidis serogroup B

More affordable and effective vaccines against bacterial meningitis caused by Neisseria meningitidis serogroup B are still required for global prevention. We have previously shown that modified outer membrane vesicles (mOMVs) from commensal Neisseria cinerea can be used as a platform to induce immune responses against meningococcal antigens. The aim of the present study was to use a combination of two genetically engineered mOMVs to express multiple antigens from N. meningitidis known to be involved in protective immunity to meningococcal meningitis (different variants of factor H binding protein (fHbp), Neisseria Heparin Binding Antigen (NHBA) and Neisseria Adhesin A (NadA)). Antigen expression in the mOMVs was confirmed by Western blotting; detoxification of the lipooligosaccharide (LOS) was confirmed by measuring human Toll-like receptor 4 (hTLR4) activation using in vitro cell assays. Mice immunised with a combination of two mOMVs expressing fHbp, NHBA and NadA produced antibodies to all the antigens. Furthermore, serum bactericidal activity (SBA) was induced by the immunisation, with mOMVs expressing NadA displaying high SBA titres against a nadA+ MenB strain. The work highlights the potential of mOMVs from N. cinerea to induce functional immune responses against multiple antigens involved in the protective immune response to meningococcal disease.

Bacterial membrane vesicles: formation, functions, and roles in bacterial-phage interactions

Outer membrane vesicles (OMVs) are nano-sized vesicles actively released by Gram-negative bacteria, playing a crucial role in bacterial survival and interactions with phages. This review focuses on OMVs and succinctly delineates the stimuli instigating OMV formation, their functional repertoire, and their involvement in bacterial-phage interplays. Initially, the discussion centers on the drivers prompting OMV genesis, encompassing both extrinsic environmental pressures and intrinsic regulatory mechanisms within bacterial systems. Subsequently, a comprehensive examination of OMVs' multifaceted functions in bacterial physiology ensues, spanning signaling cascades, nutrient transport, antibiotic resilience, and evasion of immune surveillance. Particular emphasis is placed on elucidating the paramount significance of OMVs in mediating bacterial-phage dynamics. OMVs function as decoys, providing protection to bacterial hosts against phages, and concurrently promoting the spread of phage receptors, thereby rendering phage-resistant strains susceptible to phage invasion. This comprehensive review deepens our comprehension of membrane vesicles biogenesis in bacteria and their pivotal role in microbial community dynamics.

Antibiotics-free compounds for managing carbapenem-resistant bacteria; a narrative review

Carbapenem-resistant (CR) Gram-negative bacteria have become a significant public health problem in the last decade. In recent years, the prevalence of CR bacteria has increased. The resistance to carbapenems could result from different mechanisms such as loss of porin, penicillin-binding protein alteration, carbapenemase, efflux pump, and biofilm community. Additionally, genetic variations like insertion, deletion, mutation, and post-transcriptional modification of corresponding coding genes could decrease the susceptibility of bacteria to carbapenems. In this regard, scientists are looking for new approaches to inhibit CR bacteria. Using bacteriophages, natural products, nanoparticles, disulfiram, N-acetylcysteine, and antimicrobial peptides showed promising inhibitory effects against CR bacteria. Additionally, the mentioned compounds could destroy the biofilm community of CR bacteria. Using them in combination with conventional antibiotics increases the efficacy of antibiotics, decreases their dosage and toxicity, and resensitizes CR bacteria to antibiotics. Therefore, in the present review article, we have discussed different aspects of non-antibiotic approaches for managing and inhibiting the CR bacteria and various methods and procedures used as an alternative for carbapenems against these bacteria.

Exploiting human immune repertoire transgenic mice for protective monoclonal antibodies against antimicrobial resistant Acinetobacter baumannii

The use of monoclonal antibodies for the control of drug resistant nosocomial bacteria may alleviate a reliance on broad spectrum antimicrobials for treatment of infection. We identify monoclonal antibodies that may prevent infection caused by carbapenem resistant Acinetobacter baumannii. We use human immune repertoire mice (Kymouse platform mice) as a surrogate for human B cell interrogation to establish an unbiased strategy to probe the antibody-accessible target landscape of clinically relevant A. baumannii. After immunisation of the Kymouse platform mice with A. baumannii derived outer membrane vesicles (OMV) we identify 297 antibodies and analyse 26 of these for functional potential. These antibodies target lipooligosaccharide (OCL1), the Oxa-23 protein, and the KL49 capsular polysaccharide. We identify a single monoclonal antibody (mAb1416) recognising KL49 capsular polysaccharide to demonstrate prophylactic in vivo protection against a carbapenem resistant A. baumannii lineage associated with neonatal sepsis mortality in Asia. Our end-to-end approach identifies functional monoclonal antibodies with prophylactic potential against major lineages of drug resistant bacteria accounting for phylogenetic diversity and clinical relevance without existing knowledge of a specific target antigen. Such an approach might be scaled for a additional clinically important bacterial pathogens in the post-antimicrobial era.

The aryl hydrocarbon receptor and FOS mediate cytotoxicity induced by Acinetobacter baumannii

Acinetobacter baumannii is a pathogenic and multidrug-resistant Gram-negative bacterium that causes severe nosocomial infections. To better understand the mechanism of pathogenesis, we compare the proteomes of uninfected and infected human cells, revealing that transcription factor FOS is the host protein most strongly induced by A. baumannii infection. Pharmacological inhibition of FOS reduces the cytotoxicity of A. baumannii in cell-based models, and similar results are also observed in a mouse infection model. A. baumannii outer membrane vesicles (OMVs) are shown to activate the aryl hydrocarbon receptor (AHR) of host cells by inducing the host enzyme tryptophan-2,3-dioxygenase (TDO), producing the ligand kynurenine, which binds AHR. Following ligand binding, AHR is a direct transcriptional activator of the FOS gene. We propose that A. baumannii infection impacts the host tryptophan metabolism and promotes AHR- and FOS-mediated cytotoxicity of infected cells.

Outer membrane vesicles secreted from Actinobacillus pleuropneumoniae isolate disseminating the floR resistance gene to Enterobacteriaceae

Actinobacillus pleuropneumoniae, a significant respiratory pig pathogen, is causing substantial losses in the global swine industry. The resistance spectrum of A. pleuropneumoniae is expanding, and multidrug resistance is a severe issue. Horizontal gene transfer (HGT) plays a crucial role in the development of the bacterial genome by facilitating the dissemination of resistance determinants. However, the horizontal transfer of resistance genes via A. pleuropneumoniae-derived outer membrane vesicles (OMVs) has not been previously reported. In this study, we used Illumina NovaSeq and PacBio SequeI sequencing platforms to determine the whole genome sequence of A. pleuropneumoniae GD2107, a multidrug-resistant (MDR) isolate from China. We detected a plasmid in the isolate named pGD2107-1; the plasmid was 5,027 bp in size with 7 putative open reading frames (ORF) and included the floR resistance genes. The carriage of resistance genes in A. pleuropneumoniae OMVs was identified using a polymerase chain reaction (PCR) assay, and then we thoroughly evaluated the influence of OMVs on the horizontal transfer of drug-resistant plasmids. The transfer of the plasmid to recipient bacteria via OMVs was confirmed by PCR. In growth competition experiments, all recipients carrying the pGD2107-1 plasmid exhibited a fitness cost compared to the corresponding original recipients. This study revealed that OMVs could mediate interspecific horizontal transfer of the resistance plasmid pGD2107-1 into Escherichia coli recipient strains and significantly enhance the resistance of the transformants. In summary, A. pleuropneumoniae-OMVs play the pivotal role of vectors for dissemination of the floR gene spread and may contribute to more antimicrobial resistance gene transfer in other Enterobacteriaceae.

Isolation, characterization, and immunomodulatory effects of extracellular vesicles isolated from fish pathogenic Aeromonas hydrophila

Bacterial extracellular vesicles (BEVs) are natural nanocarriers that have shown great potential for biomedical applications such as biomarkers, cancer therapy, immunomodulators, vaccines, wound healing, tissue engineering, and drug carriers. In the present study, BEVs were isolated from the gram-negative bacterium, Aeromonas hydrophila using the ultracentrifugation method and denoted as AhEVs. Using transmission electron microscopy imaging, we confirmed the ultrastructure and spherical shape morphology of AhEVs. Nanoparticle-tracking analysis results showed a mean particle size of 105.5 ± 2.0 nm for AhEVs. Moreover, the particle concentration of AhEVs was 2.34 ± 0.12 × 1011 particles/mL of bacterial supernatant. AhEV-treated fathead minnow (FHM) cells did not show cytotoxicity effects up to 50 μg/mL with no significant decrease in cells. Moreover, no mortality was observed in larval zebrafish up to 50 μg/mL which indicates that the AhEVs are biocompatible at this concentration. Furthermore, fluorescent-labeled AhEVs were internalized into FHM cells. Results of qRT-PCR analysis in FHM cells revealed that cellular pro-inflammatory cytokines such as nuclear factor (NF)-κB, interferon (Ifn), Irf7, interleukin (Il) 8, and Il11 were upregulated while downregulating the expression of anti-inflammatory Il10 in a concentration-dependent manner. AhEV-treated adult zebrafish (5 μg/fish) induced toll-like receptor (tlr) 2 and tlr4; tumor necrosis factor-alpha (tnfα); heat shock protein (hsp) 70; and il10, il6, and il1β in kidney. Protein expression of NF-κB p65 and Tnfα presented amplified levels in the spleen of AhEVs-treated zebrafish. Based on the collective findings, we conclude that AhEVs exhibited morphological and physicochemical characteristics to known EVs of gram (-)ve bacteria. At biocompatible concentrations, the immunomodulatory activity of AhEVs was demonstrated by inducing different immune response genes in FHM cells and zebrafish. Hence, we suggest that AhEVs could be a novel vaccine candidate in fish medicine due to their ability to elicit strong immune responses.

Outer membrane vesicles from X-ray-irradiated Pseudomonas aeruginosa alleviate lung injury caused by P. aeruginosa infection-mediated sepsis

Pseudomonas aeruginosa infection causes pneumonia and sepsis. Previous research found that X-ray radiation can induce P. aeruginosa to release outer membrane vesicles (OMVs) of relatively consistent sizes. This study found that OMVs derived from X-ray-irradiated P. aeruginosa can significantly inhibit lung leakage, inflammatory cell infiltrating into lung, and the production of pro-inflammatory cytokines, IL-1β and TNFα caused by P. aeruginosa infection under preventive and therapeutic administration conditions. Under the same conditions, OMVs also significantly alleviated pathological characteristics of lung injury, including pulmonary edema, pulmonary hemorrhage, and alveolar wall thickening. OMVs also significantly reduced bacterial burdens in peritoneal cavity, accompanied by a reduction in the number of viable bacteria capable of forming bacterial colonies. Pretreating macrophages and neutrophils with OMVs enhances their bactericidal ability. When bacteria were cocultured with treated cells, the number of viable bacteria capable of forming bacterial colonies was significantly reduced. OMVs themselves have not been shown to cause any lung injury or affect bacterial viability. Therefore, OMVs derived from X-ray-irradiated P. aeruginosa may not only be applied in prevention and treatment of diseases associated with P. aeruginosa infection, but also served as an excellent vaccine development platform.

Engineering Planar Gram-Negative Outer Membrane Mimics Using Bacterial Outer Membrane Vesicles

Antibiotic resistance is a major challenge in modern medicine. The unique double membrane structure of gram-negative bacteria limits the efficacy of many existing antibiotics and adds complexity to antibiotic development by limiting transport of antibiotics to the bacterial cytosol. New methods to mimic this barrier would enable high-throughput studies for antibiotic development. In this study, we introduce an innovative approach to modify outer membrane vesicles (OMVs) from Aggregatibacter actinomycetemcomitans, to generate planar supported lipid bilayer membranes. Our method first involves the incorporation of synthetic lipids into OMVs using a rapid freeze-thaw technique to form outer membrane hybrid vesicles (OM-Hybrids). Subsequently, these OM-Hybrids can spontaneously rupture when in contact with SiO2 surfaces to form a planar outer membrane supported bilayer (OM-SB). We assessed the formation of OM-Hybrids using dynamic light scattering and a fluorescence quenching assay. To analyze the formation of OM-SBs from OM-Hybrids we used quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence recovery after photobleaching (FRAP). Additionally, we conducted assays to detect surface-associated DNA and proteins on OM-SBs. The interaction of an antimicrobial peptide, polymyxin B, with the OM-SBs was also assessed. These findings emphasize the capability of our platform to produce planar surfaces of bacterial outer membranes, which in turn, could function as a valuable tool for streamlining the development of antibiotics.

Cancer Nanovaccines: Nanomaterials and Clinical Perspectives

Cancer nanovaccines represent a promising frontier in cancer immunotherapy, utilizing nanotechnology to augment traditional vaccine efficacy. This review comprehensively examines the current state-of-the-art in cancer nanovaccine development, elucidating innovative strategies and technologies employed in their design. It explores both preclinical and clinical advancements, emphasizing key studies demonstrating their potential to elicit robust anti-tumor immune responses. The study encompasses various facets, including integrating biomaterial-based nanocarriers for antigen delivery, adjuvant selection, and the impact of nanoscale properties on vaccine performance. Detailed insights into the complex interplay between the tumor microenvironment and nanovaccine responses are provided, highlighting challenges and opportunities in optimizing therapeutic outcomes. Additionally, the study presents a thorough analysis of ongoing clinical trials, presenting a snapshot of the current clinical landscape. By curating the latest scientific findings and clinical developments, this study aims to serve as a comprehensive resource for researchers and clinicians engaged in advancing cancer immunotherapy. Integrating nanotechnology into vaccine design holds immense promise for revolutionizing cancer treatment paradigms, and this review provides a timely update on the evolving landscape of cancer nanovaccines.

Extracellular vesicles-Potential link between periodontal disease and diabetic complications

It has long been suggested that a bidirectional impact exists between periodontitis and diabetes. Periodontitis may affect diabetes glycemic control, insulin resistance, and diabetic complications. Diabetes can worsen periodontitis by delaying wound healing and increasing the chance of infection. Extracellular vesicles (EVs) are heterogeneous particles of membrane-enclosed spherical structure secreted by eukaryotes and prokaryotes and play a key role in a variety of diseases. This review will introduce the biogenesis, release, and biological function of EVs from a microbial and host cell perspective, discuss the functional properties of EVs in the development of periodontitis and diabetes, and explore their role in the pathogenesis and clinical application of these two diseases. Their clinical implication and diagnostic value are also discussed.

Bacteria extracellular vesicle as nanopharmaceuticals for versatile biomedical potential

Bacteria extracellular vesicles (BEVs), characterized as the lipid bilayer membrane-surrounded nanoparticles filled with molecular cargo from parent cells, play fundamental roles in the bacteria growth and pathogenesis, as well as facilitating essential interaction between bacteria and host systems. Notably, benefiting from their unique biological functions, BEVs hold great promise as novel nanopharmaceuticals for diverse biomedical potential, attracting significant interest from both industry and academia. Typically, BEVs are evaluated as promising drug delivery platforms, on account of their intrinsic cell-targeting capability, ease of versatile cargo engineering, and capability to penetrate physiological barriers. Moreover, attributing to considerable intrinsic immunogenicity, BEVs are able to interact with the host immune system to boost immunotherapy as the novel nanovaccine against a wide range of diseases. Towards these significant directions, in this review, we elucidate the nature of BEVs and their role in activating host immune response for a better understanding of BEV-based nanopharmaceuticals' development. Additionally, we also systematically summarize recent advances in BEVs for achieving the target delivery of genetic material, therapeutic agents, and functional materials. Furthermore, vaccination strategies using BEVs are carefully covered, illustrating their flexible therapeutic potential in combating bacterial infections, viral infections, and cancer. Finally, the current hurdles and further outlook of these BEV-based nanopharmaceuticals will also be provided.

Extracellular vesicles released by host epithelial cells during Pseudomonas aeruginosa infection function as homing beacons for neutrophils

BACKGROUND

Pseudomonas aeruginosa (PA) is an opportunistic pathogen that can cause sight threatening infections in the eye and fatal infections in the cystic fibrosis airway. Extracellular vesicles (EVs) are released by host cells during infection and by the bacteria themselves; however, there are no studies on the composition and functional role of host-derived EVs during PA infection of the eye or lung. Here we investigated the composition and capacity of EVs released by PA infected epithelial cells to modulate innate immune responses in host cells.

METHODS

Human telomerase immortalized corneal epithelial cells (hTCEpi) cells and human telomerase immortalized bronchial epithelial cells (HBECs) were treated with a standard invasive test strain of Pseudomonas aeruginosa, PAO1, for 6 h. Host derived EVs were isolated by qEV size exclusion chromatography. EV proteomic profiles during infection were compared using mass spectrometry and functional studies were carried out using hTCEpi cells, HBECs, differentiated neutrophil-like HL-60 cells, and primary human neutrophils isolated from peripheral blood.

RESULTS

EVs released from PA infected corneal epithelial cells increased pro-inflammatory cytokine production in naïve corneal epithelial cells and induced neutrophil chemotaxis independent of cytokine production. The EVs released from PA infected bronchial epithelial cells were also chemotactic although they failed to induce cytokine secretion from naïve HBECs. At the proteomic level, EVs derived from PA infected corneal epithelial cells exhibited lower complexity compared to bronchial epithelial cells, with the latter having reduced protein expression compared to the non-infected control.

CONCLUSIONS

This is the first study to comprehensively profile EVs released by corneal and bronchial epithelial cells during Pseudomonas infection. Together, these findings show that EVs released by PA infected corneal and bronchial epithelial cells function as potent mediators of neutrophil migration, contributing to the exuberant neutrophil response that occurs during infection in these tissues.

Cargo exchange between human and bacterial extracellular vesicles in gestational tissues: a new paradigm in communication and immune development

Host-bacteria and bacteria-bacteria interactions can be facilitated by extracellular vesicles (EVs) secreted by both human and bacterial cells. Human and bacterial EVs (BEVs) propagate and transfer immunogenic cargos that may elicit immune responses in nearby or distant recipient cells/tissues. Hence, direct colonization of tissues by bacterial cells is not required for immunogenic stimulation. This phenomenon is important in the feto-maternal interface, where optimum tolerance between the mother and fetus is required for a successful pregnancy. Though the intrauterine cavity is widely considered sterile, BEVs from diverse sources have been identified in the placenta and amniotic cavity. These BEVs can be internalized by human cells, which may help them evade host immune surveillance. Though it appears logical, whether bacterial cells internalize human EVs or human EV cargo is yet to be determined. However, the presence of BEVs in placental tissues or amniotic cavity is believed to trigger a low-grade immune response that primes the fetal immune system for ex-utero survival, but is insufficient to disrupt the progression of pregnancy or cause immune intolerance required for adverse pregnancy events. Nevertheless, the exchange of bioactive cargos between human and BEVs, and the mechanical underpinnings and health implications of such interactions, especially during pregnancy, are still understudied. Therefore, while focusing on the feto-maternal interface, we discussed how human cells take up BEVs and whether bacterial cells take up human EVs or their cargo, the exchange of cargos between human and BEVs, host cell (feto-maternal) inflammatory responses to BEV immunogenic stimulation, and associations of these interactions with fetal immune priming and adverse reproductive outcomes such as preeclampsia and preterm birth.

Potent activity of polymyxin B is associated with long-lived super-stoichiometric accumulation mediated by weak-affinity binding to lipid A

Polymyxins are gram-negative antibiotics that target lipid A, the conserved membrane anchor of lipopolysaccharide in the outer membrane. Despite their clinical importance, the molecular mechanisms underpinning polymyxin activity remain unresolved. Here, we use surface plasmon resonance to kinetically interrogate interactions between polymyxins and lipid A and derive a phenomenological model. Our analyses suggest a lipid A-catalyzed, three-state mechanism for polymyxins: transient binding, membrane insertion, and super-stoichiometric cluster accumulation with a long residence time. Accumulation also occurs for brevicidine, another lipid A-targeting antibacterial molecule. Lipid A modifications that impart polymyxin resistance and a non-bactericidal polymyxin derivative exhibit binding that does not evolve into long-lived species. We propose that transient binding to lipid A permeabilizes the outer membrane and cluster accumulation enables the bactericidal activity of polymyxins. These findings could establish a blueprint for discovery of lipid A-targeting antibiotics and provide a generalizable approach to study interactions with the gram-negative outer membrane.

Characterisation of sRNAs enriched in outer membrane vesicles of pathogenic Flavobacterium psychrophilum causing Bacterial Cold Water Disease in rainbow trout

Flavobacterium psychrophilum (Fp) causes Bacterial Cold Water Disease in salmonids. During host-pathogen interactions, gram-negative bacteria, such as Fp, release external membrane vesicles (OMVs) harbouring cargos, such as DNA, RNA and virulence factors. This study aimed to characterise the potential role of the OMVs' small RNAs (sRNAs) in the Fp-rainbow trout host-pathogen interactions. sRNAs carried within OMVs were isolated from Fp. RNA-Seq datasets from whole-cell Fp and their isolated OMVs indicated substantial enrichment of specific sRNAs in the OMVs compared to the parent cell. Many of the OMV-packaged sRNAs were located in the pathogenicity islands of Fp. Conservation of sRNAs in 65 strains with variable degrees of virulence was reported. Dual RNA-Seq of host and pathogen transcriptomes on day 5 post-infection of Fp -resistant and -susceptible rainbow trout genetic lines revealed correlated expression of OMV-packaged sRNAs and their predicted host's immune gene targets. In vitro, treatment of the rainbow trout epithelial cell line RTgill-W1 with OMVs showed signs of cytotoxicity accompanied by dynamic changes in the expression of host genes when profiled 24 h following treatment. The OMV-treated cells, similar to the Fp -resistant fish, showed downregulated expression of the suppressor of cytokine signalling 1 (SOCS1) gene, suggesting induction of phagosomal maturation. Other signs of modulating the host gene expression following OMV-treatment include favouring elements from the phagocytic, endocytic and antigen presentation pathways in addition to HSP70, HSP90 and cochaperone proteins, which provide evidence for a potential role of OMVs in boosting the host immune response. In conclusion, the study identified novel microbial targets and inherent characteristics of OMVs that could open up new avenues of treatment and prevention of fish infections.

Multivariate Analysis of Individual Bacterial Outer Membrane Vesicles Using Fluorescence Microscopy

Gram-negative bacteria produce outer membrane vesicles (OMVs) that play a critical role in cell-cell communication and virulence. OMVs have emerged as promising therapeutic agents for various biological applications such as vaccines and targeted drug delivery. However, the full potential of OMVs is currently constrained by inherent heterogeneities, such as size and cargo differences, and traditional ensemble assays are limited in their ability to reveal OMV heterogeneity. To overcome this issue, we devised an innovative approach enabling the identification of various characteristics of individual OMVs. This method, employing fluorescence microscopy, facilitates the detection of variations in size and surface markers. To demonstrate our method, we utilize the oral bacterium Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) which produces OMVs with a bimodal size distribution. As part of its virulence, A. actinomycetemcomitans secretes leukotoxin (LtxA) in two forms: soluble and surface associated with the OMVs. We observed a correlation between the size and toxin presence where larger OMVs were much more likely to possess LtxA compared to the smaller OMVs. In addition, we noted that, among the smallest OMVs (<100 nm diameter), the fractions that are toxin positive range from 0 to 30%, while the largest OMVs (>200 nm diameter) are between 70 and 100% toxin positive.

Staphylococcus Aureus Membrane Vesicles Kill Tumor Cells Through a Caspase-1-Dependent Pyroptosis Pathway

Introduction

Nanosized outer membrane vesicles (OMVs) from Gram-negative bacteria have attracted increasing interest because of their antitumor activity. However, the antitumor effects of MVs isolated from Gram-positive bacteria have rarely been investigated.

Methods

MVs of Staphylococcus aureus USA300 were prepared and their antitumor efficacy was evaluated using tumor-bearing mouse models. A gene knock-in assay was performed to generate luciferase Antares2-MVs for bioluminescent detection. Cell counting kit-8 and lactic dehydrogenase release assays were used to detect the toxicity of the MVs against tumor cells in vitro. Active caspase-1 and gasdermin D (GSDMD) levels were determined using Western blot, and the tumor inhibition ability of MVs was determined in B16F10 cells treated with a caspase-1 inhibitor.

Results

The vesicular particles of S. aureus USA300 MVs were 55.23 ± 8.17 nm in diameter, and 5 μg of MVs remarkably inhibited the growth of B16F10 melanoma in C57BL/6 mice and CT26 colon adenocarcinoma in BALB/c mice. The bioluminescent signals correlated well with the concentrations of the engineered Antares2-MVs (R2 = 0.999), and the sensitivity for bioluminescence imaging was 4 × 10-3 μg. Antares2-MVs can directly target tumor tissues in vivo, and 20 μg/mL Antares2-MVs considerably reduced the growth of B16F10 and CT26 tumor cells, but not non-carcinomatous bEnd.3 cells. MV treatment substantially increased the level of active caspase-1, which processes GSDMD to trigger pyroptosis in tumor cells. Blocking caspase-1 activation with VX-765 significantly protected tumor cells from MV killing in vitro and in vivo.

Conclusion

S. aureus MVs can kill tumor cells by activating the pyroptosis pathway, and the induction of pyroptosis in tumor cells is a promising strategy for cancer treatment.

P. aeruginosa tRNA-fMet halves secreted in outer membrane vesicles suppress lung inflammation in cystic fibrosis

Although tobramycin increases lung function in people with cystic fibrosis (pwCF), the density of Pseudomonas aeruginosa (P. aeruginosa) in the lungs is only modestly reduced by tobramycin; hence, the mechanism whereby tobramycin improves lung function is not completely understood. Here, we demonstrate that tobramycin increases 5' tRNA-fMet halves in outer membrane vesicles (OMVs) secreted by laboratory and CF clinical isolates of P. aeruginosa. The 5' tRNA-fMet halves are transferred from OMVs into primary CF human bronchial epithelial cells (CF-HBEC), decreasing OMV-induced IL-8 and IP-10 secretion. In mouse lungs, increased expression of the 5' tRNA-fMet halves in OMVs attenuated KC (murine homolog of IL-8) secretion and neutrophil recruitment. Furthermore, there was less IL-8 and neutrophils in bronchoalveolar lavage fluid isolated from pwCF during the period of exposure to tobramycin versus the period off tobramycin. In conclusion, we have shown in mice and in vitro studies on CF-HBEC that tobramycin reduces inflammation by increasing 5' tRNA-fMet halves in OMVs that are delivered to CF-HBEC and reduce IL-8 and neutrophilic airway inflammation. This effect is predicted to improve lung function in pwCF receiving tobramycin for P. aeruginosa infection.NEW & NOTEWORTHY The experiments in this report identify a novel mechanism, whereby tobramycin reduces inflammation in two models of CF. Tobramycin increased the secretion of tRNA-fMet halves in OMVs secreted by P. aeruginosa, which reduced the OMV-LPS-induced inflammatory response in primary cultures of CF-HBEC and in mouse lung, an effect predicted to reduce lung damage in pwCF.

Unveiling clinical applications of bacterial extracellular vesicles as natural nanomaterials in disease diagnosis and therapeutics

Bacterial extracellular vesicles (BEVs) are naturally occurring bioactive membrane-bound nanoparticles released by both gram-negative and gram-positive bacterial species, exhibiting a multifaceted role in mediating host-microbe interactions across various physiological conditions. Increasing evidence supports BEVs as essential mediators of cell-to-cell communicaiton, influencing bacterial pathogenicity, disease mechanisms, and modulating the host immune response. However, the extent to which these BEV-mediated actions can be leveraged to predict disease onset, guide treatment strategies, and determine clinical outcomes remains uncertain, particularly in terms of their clinical translation potentials. This review briefly describes BEV biogenesis and their internalisation by recipient cells and summarises methods for isolation and characterization, essential for understanding their composition and cargo. Further, it discusses the potential of biofluid-associated BEVs as biomarkers for various diseases, spanning both cancer and non-cancerous conditions. Following this, we outline the ongoing human clinical trials of using BEVs for vaccine development. In addition to disease diagnostics, this review explores the emerging research of using natural or engineered BEVs as smart nanomaterials for applications in anti-cancer therapy and bone regeneration. This discussion extends to key factors for unlocking the clinical potential of BEVs, such as standardization of BEV isolation and characterisation, as well as other hurdles in translating these findings to the clinical setting. We propose that addressing these hurdles through collaborative research efforts and well-designed clinical trials holds the key to fully harnessing the clinical potential of BEVs. As this field advances, this review suggests that BEV-based nanomedicine has the potential to revolutionize disease management, paving the way for innovative diagnosis, therapeutics, and personalized medicine approaches. STATEMENT OF SIGNIFICANCE: Extracellular vesicles (EVs) from both host cells and bacteria serve as multifunctional biomaterials and are emerging in the fields of biomedicine, bioengineering, and biomaterials. However, the majority of current studies focus on host-derived EVs, leaving a gap in comprehensive research on bacteria-derived EVs (BEVs). Although BEVs offer an attractive option as nanomaterials for drug delivery systems, their unique nanostructure and easy-to-modify functions make them a potential method for disease diagnosis and treatment as well as vaccine development. Our work among the pioneering studies investigating the potential of BEVs as natural nanobiomaterials plays a crucial role in both understanding the development of diseases and therapeutic interventions.

Mycobacterium abscessus extracellular vesicles increase mycobacterial resistance to clarithromycin in vitro

Nontuberculous Mycobacteria (NTM) are a group of emerging bacterial pathogens that have been identified in cystic fibrosis (CF) patients with microbial lung infections. The treatment of NTM infection in CF patients is challenging due to the natural resistance of NTM species to many antibiotics. Mycobacterium abscessus is one of the most common NTM species found in the airways of CF patients. In this study, we characterized the extracellular vesicles (EVs) released by drug-sensitive M. abscessus untreated or treated with clarithromycin (CLR), one of the frontline anti-NTM drugs. Our data show that exposure to CLR increases mycobacterial protein trafficking into EVs as well as the secretion of EVs in culture. Additionally, EVs released by CLR-treated M. abscessus increase M. abscessus resistance to CLR when compared to EVs from untreated M. abscessus. Proteomic analysis further indicates that EVs released by CLR-treated M. abscessus carry an increased level of 50S ribosomal subunits, the target of CLR. Taken together, our results suggest that EVs play an important role in M. abscessus resistance to CLR treatment.

Klebsiella pneumoniae-OMVs activate death-signaling pathways in Human Bronchial Epithelial Host Cells (BEAS-2B)

The programmed cell death pathways of apoptosis are important in mammalian cellular protection from infections. The activation of these pathways depends on the presence of membrane receptors that bind bacterial components to activate the transduction mechanism. In addition to bacteria, these mechanisms can be activated by outer membrane vesicles (OMVs). OMVs are spherical vesicles of 20-250 nm diameter, constitutively released by Gram-negative bacteria. They contain several bacterial determinants including proteins, DNA/RNA and proteins, that activate different cellular processes in host cells. This study focused on Klebsiella pneumoniae-OMVs in activating death mechanisms in human bronchial epithelial cells (BEAS-2B). Characterization of purified OMVs was achieved by scanning electron microscopy, nanoparticle tracking analysis and protein profiling. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay while apoptotic induction was measured by flow cytometry and confirmed by western blotting. The OMVs produced showed a spherical morphology, with a diameter of 137.2 ± 41 nm and a vesicular density of 7.8 × 109 particles/mL Exposure of cell monolayers to 50 μg of K. pneumoniae-OMV for 14 h resulted in approximately 25 % cytotoxicity and 41.15-41.14 % of cells undergoing early and late apoptosis. Fluorescence microscopy revealed reduced cellular density, the presence of apoptotic bodies, chromatin condensation, and nuclear membrane blebbing in residual cells. Activation of caspases -3 and -9 and dysregulation of BAX, BIM and Bcl-xL indicated the activation of mitochondria-dependent apoptosis. Furthermore, a decrease in the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase involved endoplasmic reticulum stress with the potential formation of reactive oxygen species. These findings provide evidence for the role of OMVs in apoptosis and involvement in the pathogenesis of K. pneumoniae infections.

Bacterial extracellular vesicles: biotechnological perspective for enhanced productivity

Bacterial extracellular vesicles (BEVs) are non-replicative nanostructures released by Gram-negative and Gram-positive bacteria as a survival mechanism and inter- and intraspecific communication mechanism. Due to BEVs physical, biochemical, and biofunctional characteristics, there is interest in producing and using them in developing new therapeutics, vaccines, or delivery systems. However, BEV release is typically low, limiting their application. Here, we provide a biotechnological perspective to enhance BEV production, highlighting current strategies. The strategies include the production of hypervesiculating strains through gene modification, bacteria culture under stress conditions, and artificial vesicles production. We discussed the effect of these production strategies on BEVs types, morphology, composition, and activity. Furthermore, we summarized general aspects of BEV biogenesis, functional capabilities, and applications, framing their current importance and the need to produce them in abundance. This review will expand the knowledge about the range of strategies associated with BEV bioprocesses to increase their productivity and extend their application possibilities.