Bacterial ghosts as novel efficient targeting vehicles for DNA delivery to the human monocyte-derived dendritic cells

Bacterial carrier-mediated drug delivery systems: a promising strategy in cancer therapy

Cancer is a major killer threatening modern human health and a leading cause of death worldwide. Due to the heterogeneity and complexity of cancer, traditional treatments have limited effectiveness. To address this problem, an increasing number of researchers and medical professionals are working to develop new ways to treat cancer. Bacteria have chemotaxis that can target and colonize tumor tissue, as well as activate anti-tumor immune responses, which makes them ideal for biomedical applications. With the rapid development of nanomedicine and synthetic biology technologies, bacteria are extensively used as carriers for drug delivery to treat tumors, which holds the promise of overcoming the limitations of conventional cancer treatment regimens. This paper summarizes examples of anti-cancer drugs delivered by bacterial carriers, and their strengths and weaknesses. Further, we emphasize the promise of bacterial carrier delivery systems in clinical translation.

Bacterial ghosts: A breakthrough approach to cancer vaccination

Cancer is a devastating disease worldwide with high mortality rates and is a foremost concern for society. Immunotherapy has emerged as a promising strategy for treating cancer, harnessing the power of immune system to recognize and kill tumor cells. Bacterial ghosts (BGs), a novel platform in cancer vaccination, are suitable for personalized and effective immunotherapeutic interventions. BG are empty bacterial cell envelopes generated through a controlled lysis process, leaving behind empty but structurally intact cell membranes. BGs have been used as vaccine adjuvants and vaccine delivery vehicles worldwide. They possess inherent immunogenicity, enabling them to be used for controlled release and targeted drug delivery. Recently, the potential of BGs has been explored for tumor inhibition, making them suitable carrier vehicles. This review highlights cancer immunotherapy, methods of BG preparation, characterization of BGs, the interaction of BGs with the immune system, and research progress on BG-based cancer vaccines with future insights.

Bactofection, Bacterial-Mediated Vaccination, and Cancer Therapy: Current Applications and Future Perspectives

From the first report in 1891 by Dr. Coley of the effective treatment of tumors in 1000 patients with Streptococcus and the first successful use of bacterial vectors for transferring therapeutic genes in 1980 by Dr. Schnaffer, bactofection has been shown to be a promising strategy in the fields of vaccination, gene therapy, and cancer therapy. This review describes the general theory of bactofection and its advantages, disadvantages, challenges, and expectations, compiling the most notable advances in 14 vaccination studies, 27 cancer therapy studies, and 13 clinical trials. It also describes the current scope of bactofection and promising results. The extensive knowledge of Salmonella biology, as well as the multiple adequacies of the Ty21a vaccination platform, has allowed notable developments worldwide that have mainly been reflected in therapeutic efforts against cancer. In this regard, we strongly recommend the creation of a recombinant Ty21a model that constitutively expresses the GtgE protease from S. typhimurium, allowing this vector to be used in animal trials, thus enhancing the likelihood of favorable results that could quickly transition to clinical trials. From the current perspective, it is necessary to explore a greater diversity of bacterial vectors and find the best combination of implemented attenuations, generating personalized models that guarantee the maximum effectiveness in cancer therapy and vaccination.

Deciphering the Potential of Probiotics in Vaccines

The demand for vaccines, particularly those prepared from non-conventional sources, is rising due to the emergence of drug resistance around the globe. Probiotic-based vaccines are a wise example of such vaccines which represent new horizons in the field of vaccinology in providing an enhanced and diversified immune response. The justification for incorporating probiotics into vaccines lies in the fact that that they hold the capacity to regulate immune function directly or indirectly by influencing the gastrointestinal microbiota and related pathways. Several animal-model-based studies have also highlighted the efficacy of these vaccines. The aim of this review is to collect and summarize the trends in the recent scientific literature regarding the role of probiotics in vaccines and vaccinology, along with their impact on target populations.

Recent Update on Bacteria as a Delivery Carrier in Cancer Therapy: From Evil to Allies

Cancer is associated with a comprehensive burden that significantly affects patient’s quality of life. Even though patients’ disease condition is improving following conventional therapies, researchers are studying alternative tools that can penetrate solid tumours to deliver the therapeutics due to issues of developing resistance by the cancer cells. Treating cancer is not the only the goal in cancer therapy; it also includes protecting non-cancerous cells from the toxic effects of anti-cancer agents. Thus, various advanced techniques, such as cell-based drug delivery, bacteria-mediated therapy, and nanoparticles, are devised for site-specific delivery of drugs. One of the novel methods that can be targeted to deliver anti-cancer agents is by utilising genetically modified non-pathogenic bacterial species. This is due to the ability of bacterial species to multiply selectively or non-selectively on tumour cells, resulting in biofilms that leads to disruption of metastasis process. In preclinical studies, this technology has shown significant results in terms of efficacy, and some are currently under investigation. Therefore, researchers have conducted studies on bacteria transporting the anti-cancer drug to targeted tumours. Alternatively, bacterial ghosts and bacterial spores are utilised to deliver anti-cancer drugs. Although in vivo studies of bacteria-mediated cancer therapy have shown successful outcome, further research on bacteria, specifically their targeting mechanism, is required to establish a complete clinical approach in cancer treatment. This review has focused on the up-to-date understanding of bacteria as a therapeutic carrier in the treatment of cancer as an emerging field.

Bacteria and bacterial derivatives as delivery carriers for immunotherapy

There is growing interest in the role of microorganisms in human health and disease, with evidence showing that new types of biotherapy using engineered bacterial therapeutics, including bacterial derivatives, can address specific mechanisms of disease. The complex interactions between microorganisms and metabolic/immunologic pathways underlie many diseases with unmet medical needs, suggesting that targeting these interactions may improve patient treatment. Using tools from synthetic biology and chemical engineering, non-pathogenic bacteria or bacterial products can be programmed and designed to sense and respond to environmental signals to deliver therapeutic effectors. This review describes current progress in biotherapy using live bacteria and their derivatives to achieve therapeutic benefits against various diseases.

Bacterial Ghosts-Based Vaccine and Drug Delivery Systems

Bacterial ghosts (BGs) are empty bacterial envelopes of Gram-negative bacteria produced by controlled expressions of cloned gene E, forming a lysis tunnel structure within the envelope of the living bacteria. Globally, BGs have been used as vaccine delivery systems and vaccine adjuvants. There is an increasing interest in the development of novel delivery systems that are based on BGs for biomedical applications. Due to intact reservation of bacterial cell membranes, BGs have an inherent immunogenicity, which enables targeted drug delivery and controlled release. As carrier vehicles, BGs protect drugs from interference by external factors. In recent years, there has been an increasing interest in BG-based delivery systems against tumors, inflammation, and infection, among others. Herein, we reviewed the preparation methods for BGs, interactions between BGs and the host, and further highlighted research progress in BG development.

Minicircle Biopharmaceuticals–An Overview of Purification Strategies

Minicircles are non-viral delivery vectors with promising features for biopharmaceutical applications. These vectors are plasmid-derived circular DNA molecules that are obtained in vivo in Escherichia coli by the intramolecular recombination of a parental plasmid, which generates a minicircle containing the eukaryotic therapeutic cassette of interest and a miniplasmid containing the prokaryotic backbone. The production process results thus in a complex mixture, which hinders the isolation of minicircle molecules from other DNA molecules. Several strategies have been proposed over the years to meet the challenge of purifying and obtaining high quality minicircles in compliance with the regulatory guidelines for therapeutic use. In minicircle purification, the characteristics of the strain and parental plasmid used have a high impact and strongly affect the purification strategy that can be applied. This review summarizes the different methods developed so far, focusing not only on the purification method itself but also on its dependence on the upstream production strategy used.

Bacteria as a double-action sword in cancer

Bacteria have long been known as one of the primary causative agents of cancer, however, recent studies suggest that they can be used as a promising agent in cancer therapy. Because of the limitations that conventional treatment faces due to the specific pathophysiology and the tumor environment, there is a great need for the new anticancer therapeutic agents. Bacteriotherapy utilizes live, attenuated strains or toxins, peptides, bacteriocins of the bacteria in the treatment of cancer. Moreover, they are widely used as a vector for delivering genes, peptides, or drugs to the tumor target. Interestingly, it was found that their combination with the conventional therapeutic approaches may enhance the treatment outcome. In the genome editing era, it is feasible to develop a novel generation of therapeutic bacteria with fewer side effects and more efficacy for cancer therapy. Here we review the current knowledge on the dual role of bacteria in the development of cancer as well as cancer therapy.

The development of ghost vaccines trials

INTRODUCTION

Bacterial ghosts are intact bacterial cell envelopes that are emptied of their content by gentle biological or chemical poring methods. Ghost techniques increase the safety of the killed vaccines, while maintaining their antigenicity due to mild preparation procedures. Moreover, ghost-platforms may express and/or carry several antigens or plasmid-DNA encoding for protein epitopes.

AREAS COVERED

In this review, the development in ghost-vaccine production over the last 30 years is classified and discussed. The different applications of ghost-vaccines, how they trigger the immune system, their advantages and limitations are displayed. The phage-mediated lysis, molecular manipulation of the lysis-genes, and the biotechnological production of ghosts are described. The trials are classified according to the pattern of lysis and to the type of bacteria. Further subdivision includes chronological ordered application of the ghost as alternative-killed vaccine, recombinant antigen platform, plasmid DNA carrier, adjuvants, and dendritic cell inducer. Particular trials for specific pathogens or from distinct research schools are gathered.

EXPERT OPINION

Ghosts are highly qualified to act as immune-presenting platforms that express and/or carry several recombinant and DNA vaccines, as well as, being efficient alternative-killed vaccines. The coming years will show more molecular advances to develop ghost-production and to express more antigens.

Advances on Non-Genetic Cell Membrane Engineering for Biomedical Applications

Cell-based therapeutics are very promising modalities to address many unmet medical needs, including genetic engineering, drug delivery, and regenerative medicine as well as bioimaging. To enhance the function and improve the efficacy of cell-based therapeutics, a variety of cell surface engineering strategies (genetic engineering and non-genetic engineering) are developed to modify the surface of cells or cell-based therapeutics with some therapeutic molecules, artificial receptors, and multifunctional nanomaterials. In comparison to complicated procedures and potential toxicities associated with genetic engineering, non-genetic engineering strategies have emerged as a powerful and compatible complement to traditional genetic engineering strategies for enhancing the function of cells or cell-based therapeutics. In this review, we will first briefly summarize key non-genetic methodologies including covalent chemical conjugation (surface reactive groups-direct conjugation, and enzymatically mediated and metabolically mediated indirect conjugation) and noncovalent physical bioconjugation (biotinylation, electrostatic interaction, and lipid membrane fusion as well as hydrophobic insertion), which have been developed to engineer the surface of cell-based therapeutics with various materials. Next, we will comprehensively highlight the latest advances in non-genetic cell membrane engineering surrounding different cells or cell-based therapeutics, including whole-cell-based therapeutics, cell membrane-derived therapeutics, and extracellular vesicles. Advances will be focused specifically on cells that are the most popular types in this field, including erythrocytes, platelets, cancer cells, leukocytes, stem cells, and bacteria. Finally, we will end with the challenges, future trends, and our perspectives of this relatively new and fast-developing research field.

A Salmonella Typhi ghost induced by the E gene of phage φX174 stimulates dendritic cells and efficiently activates the adaptive immune response

Previously, we genetically engineered a Salmonella Typhi bacterial ghost (STG) as a novel inactivated vaccine candidate against typhoid fever. The underlying mechanism employed by the ghost in stimulating the adaptive immune response remains to be investigated. In this study, we aimed to evaluate the immunostimulatory effect of STG on mouse bone marrow-derived dendritic cells (BMDCs) and its activation of the adaptive immune response in vitro. Immature BMDCs were stimulated with STG, which efficiently stimulated maturation events in BMDCs, as indicated by upregulated expressions of CD40, CD80, and major histocompatibility complex class II molecules on CD11⁺ BMDCs. Immature BMDCs responded to STG stimulation by significantly increasing the expression of interleukin (IL)-6, which might indicate the induction of dendritic cell maturation in vivo (p < 0.05). In addition, ghost-stimulated murine BMDCs showed significant expressions of interferon gamma and IL-4, which can drive the development of Th1 and Th2 cells, respectively, in co-cultured CD4⁺ T cells in vitro. These results suggest that STG can effectively stimulate maturation of BMDCs and facilitate subsequent immune responses via potent immunomodulatory cytokine responses.

Recent Advances of Membrane-Cloaked Nanoplatforms for Biomedical Applications

In terms of the extremely small size and large specific surface area, nanomaterials often exhibit unusual physical and chemical properties, which have recently attracted considerable attention in bionanotechnology and nanomedicine. Currently, the extensive usage of nanotechnology in medicine holds great potential for precise diagnosis and effective therapeutics of various human diseases in clinical practice. However, a detailed understanding regarding how nanomedicine interacts with the intricate environment in complex living systems remains a pressing and challenging goal. Inspired by the diversified membrane structures and functions of natural prototypes, research activities on biomimetic and bioinspired membranes, especially for those cloaking nanosized platforms, have increased exponentially. By taking advantage of the flexible synthesis and multiple functionality of nanomaterials, a variety of unique nanostructures including inorganic nanocrystals and organic polymers have been widely devised to substantially integrate with intrinsic biomoieties such as lipids, glycans, and even cell and bacteria membrane components, which endow these abiotic nanomaterials with specific biological functionalities for the purpose of detailed investigation of the complicated interactions and activities of nanomedicine in living bodies, including their immune response activation, phagocytosis escape, and subsequent clearance from vascular system. In this review, we summarize the strategies established recently for the development of biomimetic membrane-cloaked nanoplatforms derived from inherent host cells (e.g., erythrocytes, leukocytes, platelets, and exosomes) and invasive pathogens (e.g., bacteria and viruses), mainly attributed to their versatile membrane properties in biological fluids. Meanwhile, the promising biomedical applications based on nanoplatforms inspired by diverse moieties, such as selective drug delivery in targeted sites and effective vaccine development for disease prevention, have also been outlined. Finally, the potential challenges and future prospects of the biomimetic membrane-cloaked nanoplatforms are also discussed.

Oncolysate-loaded Escherichia coli bacterial ghosts enhance the stimulatory capacity of human dendritic cells

The natural adjuvant properties of bacterial ghosts (BGs) lie within the presence of intact pathogen-associated molecular patterns on their surface. BGs can improve the direct delivery, natural processing and presentation of target antigens within dendritic cells (DCs). Moreover, sensitization of human DCs by cancer cell lysate (oncolysate)-loaded BGs in the presence of IFN-α and GM-CSF enhanced DC maturation as indicated by an increased expression of maturation markers and co-stimulatory molecules, higher production of IL-12p70 and stimulation of significantly increased proliferation of both autologous CD4+ and CD8+ T cells compared to DCs matured in the presence of purified lipopolysaccharide. The induced T cells efficiently recognized oncolysate-derived tumor-associated antigens expressed by cancer cells used for the production of oncolysate. Our optimized one-step simultaneous antigen delivery and DC maturation-inducing method emerges as a promising tool for the development and implementation of next-generation cellular cancer immunotherapies.

Exosome-Based Cancer Therapy: Implication for Targeting Cancer Stem Cells

Drug resistance, difficulty in specific targeting and self-renewal properties of cancer stem cells (CSCs) all contribute to cancer treatment failure and relapse. CSCs have been suggested as both the seeds of the primary cancer, and the roots of chemo- and radio-therapy resistance. The ability to precisely deliver drugs to target CSCs is an urgent need for cancer therapy, with nanotechnology-based drug delivery system being one of the most promising tools to achieve this in the clinic. Exosomes are cell-derived natural nanometric vesicles that are widely distributed in body fluids and involved in multiple disease processes, including tumorigenesis. Exosome-based nanometric vehicles have a number of advantages: they are non-toxic, non-immunogenic, and can be engineered to have robust delivery capacity and targeting specificity. This enables exosomes as a powerful nanocarrier to deliver anti-cancer drugs and genes for CSC targeting therapy. Here, we will introduce the current explorations of exosome-based delivery system in cancer therapy, with particular focus on several exosomal engineering approaches that have improved their efficiency and specificity for CSC targeting.

Effectiveness of F18+ Fimbrial Antigens Released by a Novel Autolyzed Salmonella Expression System as a Vaccine Candidate against Lethal F18+ STEC Infection

Porcine edema disease (ED) caused by Shiga toxin 2e producing Escherichia coli expressing F18ab⁺ fimbriae (F18ab⁺STEC) frequently occurs in post-weaned piglets, resulting in a significant economic loss in swine industries worldwide. In the present study, we proposed an efficient prevention scheme against ED in which the attenuated Salmonella Typhimurium inactivated by the E-mediated cell lysis to deliver target antigens, FedF and FedA, which function in fimbrial-mediated adhesion and as a major subunit of F18ab+fimbriae, respectively. The co-expression of FedA and FedF protein with outer membrane protein A signal peptide was confirmed in the resultant strains JOL1460 and JOL1464 by immunoblot analysis. Immunization with the candidate strains in mice led to the significant generation of immunoglobulin (Ig) G, specific to both antigens and secretory IgA specific to FedF (P < 0.05). The titers of IgG isotypes, IgG1 and IgG2a, used as markers for T-helpers (Th)-2 and Th-1lymphocytes, respectively, also significantly increased in the immunized group (P < 0.05). The increase in CD3⁺CD4⁺ T lymphocyte subpopulation and in vitro proliferative activity was observed in in vivo stimulated splenocytes, which indicated the immunostimulatory effect of the candidate strains. Moreover, the immunized mice were completely protected from a lethal challenge against wild-type F18⁺STEC whereas 28% of mice died in the non-immunized group. This study demonstrated that the inactivated Salmonella system could efficiently release FedF and FedA and induce robust immune responses specific to the target antigens, which is sufficient to protect the mice from the lethal challenge.

Biomimetic strategies for targeted nanoparticle delivery

Nanoparticle‐based drug delivery and imaging platforms have become increasingly popular over the past several decades. Among different design parameters that can affect their performance, the incorporation of targeting functionality onto nanoparticle surfaces has been a widely studied subject. Targeted formulations have the ability to improve efficacy and function by positively modulating tissue localization. Many methods exist for creating targeted nanoformulations, including the use of custom biomolecules such as antibodies or aptamers. More recently, a great amount of focus has been placed on biomimetic targeting strategies that leverage targeting interactions found directly in nature. Such strategies, which have been painstakingly selected over time by the process of evolution to maximize functionality, oftentimes enable scientists to forgo the specialized discovery processes associated with many traditional ligands and help to accelerate development of novel nanoparticle formulations. In this review, we categorize and discuss in‐depth recent works in this growing field of bioinspired research.

Vibrio cholerae ghosts (VCG) exert immunomodulatory effect on dendritic cells for enhanced antigen presentation and induction of protective immunity

BACKGROUND

We previously showed that the Vibrio cholerae ghost platform (VCG; empty V. cholerae cell envelopes) is an effective delivery system for vaccine antigens promoting the induction of substantial immunity in the absence of external adjuvants. However, the mechanism by which these cell envelopes enhance immunity and stimulate a predominantly Th1 cellular and humoral immune response has not been elucidated. We hypothesized that the immunostimulatory ability of VCG involves dendritic cell (DC) activation.

OBJECTIVE

The aims of this study were: a) to investigate the ability of DCs [using mouse bone marrow-derived DCs (BMDCs) as a model system] to take up and internalize VCGs; b) to evaluate the immunomodulatory effect of internalized VCGs on DC activation and maturation and their functional capacity to present chlamydial antigen to naïve and infection-sensitized CD4+ T cells and; c) to evaluate the ability of VCGs to enhance the protective immunity of a chlamydial antigen.

RESULTS

VCGs were efficiently internalized by DCs without affecting their viability and modulated DC-mediated immune responses. VCG-pulsed DCs showed increased secretion of proinflammatory cytokines and expression of co-stimulatory molecules associated with DC maturation in response to stimulation with UV-irradiated chlamydial elementary bodies (UV-EBs). Furthermore, this interaction resulted in effective chlamydial antigen presentation to infection-sensitized but not naïve CD4+ T cells and enhancement of protective immunity.

CONCLUSIONS

The present study demonstrated that VCGs activate DCs leading to the surface expression of co-stimulatory molecules associated with DC activation and maturation and enhancement of protective immunity induced by a chlamydial antigen. The results indicate that the immunoenhancing activity of VCG for increased T-cell activation against antigens is mediated, at least in part, through DC triggering. Thus, VCGs could be harnessed as immunomodulators to target antigens to DCs for enhancement of protective immunity against microbial infections.

An immunogenic Salmonella ghost confers protection against internal organ colonization and egg contamination

The tightly regulated expression of the PhiX174 lysis gene E from a multi-copy plasmid led to the stable production of an Salmonella Enteritidis bacterial ghost. The present study was conducted to evaluate induction of the humoral and cell-mediated immune responses induced after single or double intramuscular immunization with the S. Enteritidis ghost and to assess its protective effect on colonization of the intestinal tract, visceral and reproductive organs, internal egg contamination, and egg production of laying chickens. A total of 60 chickens were equally divided into three groups (n=20); group A (non-immunized control), group B (immunized at 8 and 16 weeks of age) and group C (immunized at 16th week of age). Chickens from both immunized groups B and C demonstrated significant increases in plasma IgG, intestinal secretory IgA levels, and antigen-specific lymphocyte proliferative responses. The population of CD3+CD4+ positive T cells in the immunized chickens was also significantly increased after immunization and virulent challenge. In addition, the immunized groups B and C showed significantly higher egg production and a lower percentage of S. Enteritidis contaminated eggs after challenge compared to those of group A. A comparison of challenge strain isolation from the immunized-challenged and non-immunized-challenged layer hens showed that the double immunization group induced excellent protection against intestinal, liver, splenic, and ovarian Salmonella colonization; however, the single immunized chickens showed lower counts only in the splenic and ovarian organs. Overall, the data give compelling evidence that vaccination with the S. Enteritidis ghost induced robust protective immunity against experimental avian salmonellosis and may contribute to the reduce incidence of egg contamination.

Drug delivery strategies in the therapy of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a frequently occurring disease in young people, which is characterized by a chronic inflammation of the gastrointestinal tract. The therapy of IBD is dominated by the administration of anti-inflammatory and immunosuppressive drugs, which suppress the intestinal inflammatory burden and improve the disease-related symptoms. Established treatment strategies are characterized by a limited therapeutical efficacy and the occurrence of adverse drug reactions. Thus, the development of novel disease-targeted drug delivery strategies is intended for a more effective therapy and demonstrates the potential to address unmet medical needs. This review gives an overview about the established as well as future-oriented drug targeting strategies, including intestine targeting by conventional drug delivery systems (DDS), disease targeted drug delivery by synthetic DDS and disease targeted drug delivery by biological DDS. Furthermore, this review analyses the targeting mechanisms of the respective DDS and discusses the possible field of utilization in IBD.

Periodontal disease immunology: 'double indemnity' in protecting the host

During the last two to three decades our understanding of the immunobiology of periodontal disease has increased exponentially, both with respect to the microbial agents triggering the disease process and the molecular mechanisms of the host engagement maintaining homeostasis or leading to collateral tissue damage. These foundational scientific findings have laid the groundwork for translating cell phenotype, receptor engagement, intracellular signaling pathways and effector functions into a 'picture' of the periodontium as the host responds to the 'danger signals' of the microbial ecology to maintain homeostasis or succumb to a disease process. These findings implicate the chronicity of the local response in attempting to manage the microbial challenge, creating a 'Double Indemnity' in some patients that does not 'insure' health for the periodontium. As importantly, in reflecting the title of this volume of Periodontology 2000, this review attempts to inform the community of how the science of periodontal immunology gestated, how continual probing of the biology of the disease has led to an evolution in our knowledge base and how more recent studies in the postgenomic era are revolutionizing our understanding of disease initiation, progression and resolution. Thus, there has been substantial progress in our understanding of the molecular mechanisms of host-bacteria interactions that result in the clinical presentation and outcomes of destructive periodontitis. The science has embarked from observations of variations in responses related to disease expression with a focus for utilization of the responses in diagnosis and therapeutic outcomes, to current investigations using cutting-edge fundamental biological processes to attempt to model the initiation and progression of soft- and hard-tissue destruction of the periodontium. As importantly, the next era in the immunobiology of periodontal disease will need to engage more sophisticated experimental designs for clinical studies to enable robust translation of basic biologic processes that are in action early in the transition from health to disease, those which stimulate microenvironmental changes that select for a more pathogenic microbial ecology and those that represent a rebalancing of the complex host responses and a resolution of inflammatory tissue destruction.

Production and characterization of mouse monoclonal antibodies against lysis protein E of phiX174

Bacterial ghosts offer a new avenue for the study of inactivated vaccines. However, for many years the mechanism of genetic inactivation was controversial. To obtain mouse monoclonal antibodies (mAbs) against protein E will allow the observation of its location and dynamic expression to expand understanding of the lysis mechanism. In this study, a His-tagged ΔE fusion protein expressed in bacteria was used as the immunogen, and mAbs targeting protein E were produced by the hybridoma technique and selected by enzyme-linked immunosorbent assay using GST-E and GST-ΔE as coating proteins. Purified mAbs from mouse ascites were screened against a phage-displayed random dodecapeptide library (Ph.D.-12). After three rounds of biopanning, 30 phage clones were randomly selected and sequenced, and their amino acids were deduced. One epitope showed a good match with protein E at 57-63aa (KPLN--R) and the synthetic decapeptide Epep (VRLKPLNCSR) strongly inhibited combination of E-A5 with E fusion proteins. Immunofluorescence microscopy indicated specific immunoreactivity of E-A5 with Escherichia coli-expressed native protein E. The novel mAbs may be of great potential value in analysis of the function and lysis pathway of protein E and other relative phages and in evaluation of E as potential marker of bacterial ghosts.

Modulation of bacterial ghosts--induced nitric oxide production in macrophages by bacterial ghost-delivered resveratrol

The present study aimed to investigate the capacity of resveratrol (RV) delivered into macrophages by bacterial ghosts (BGs), representing intact empty nonliving envelopes of Gram-negative bacteria, to modulate nitric oxide (NO) production related to the presence of the pathogen-associated molecular patterns on the surface of BGs. Incubation of the murine macrophage cell line RAW 264.7 with BGs leads to a dose-dependent activation of inducible NO synthase. To modify BG-induced NO formation in RAW 264.7 cells by RV; BGs were loaded with RV (RV-BGs) and incubated with murine macrophages in a dose-dependent manner. RV-BGs delivering RV to the target macrophages significantly reduced BG-induced NO production with concentration of RV more than one order of magnitude lower than the amount of RV capable of reducing NO formation when applied directly. Moreover, no cytotoxic impact of BGs on the viability of RAW 264.7 cells added to macrophages alone or loaded with RV was detected after a mutual 24 h incubation, whereas cell viability slightly decreased (~ 10%) when RV concentrations of 30 μm alone were applied. The results obtained in the present study clearly indicate that the intracellular delivery of RV by BGs significantly enhances the total RV effect.

Involvement of long noncoding RNAs in diseases affecting the central nervous system

DNA sequences associated with protein-coding genes have been the primary focus of most genetic analyses of complex human diseases. Although we are rapidly gaining a comprehensive view of the etiology of certain central nervous system disorders, major gaps in our understanding persist. Recent studies have uncovered that many human genomic sequences are transcribed but not translated, generating an astounding diversity of noncoding RNAs (ncRNAs). This awareness should be taken into account when studying human diseases and may have profound implications on the development of novel biomarkers as well as therapies.

The Bacterial Ghost platform system: production and applications

The Bacterial Ghost (BG) platform technology is an innovative system for vaccine, drug or active substance delivery and for technical applications in white biotechnology. BGs are cell envelopes derived from Gram-negative bacteria. BGs are devoid of all cytoplasmic content but have a preserved cellular morphology including all cell surface structures. Using BGs as delivery vehicles for subunit or DNA-vaccines the particle structure and surface properties of BGs are targeting the carrier itself to primary antigen-presenting cells. Furthermore, BGs exhibit intrinsic adjuvant properties and trigger an enhanced humoral and cellular immune response to the target antigen. Multiple antigens of the native BG envelope and recombinant protein or DNA antigens can be combined in a single type of BG. Antigens can be presented on the inner or outer membrane of the BG as well as in the periplasm that is sealed during BG formation. Drugs or supplements can also be loaded to the internal lumen or periplasmic space of the carrier. BGs are produced by batch fermentation with subsequent product recovery and purification via tangential flow filtration. For safety reasons all residual bacterial DNA is inactivated during the BG production process by the use of staphylococcal nuclease A and/or the treatment with β-propiolactone. After purification BGs can be stored long-term at ambient room temperature as lyophilized product. The production cycle from the inoculation of the pre-culture to the purified BG concentrate ready for lyophilization does not take longer than a day and thus meets modern criteria of rapid vaccine production rather than keeping large stocks of vaccines. The broad spectrum of possible applications in combination with the comparably low production costs make the BG platform technology a safe and sophisticated product for the targeted delivery of vaccines and active agents as well as carrier of immobilized enzymes for applications in white biotechnology.

Enhancement of bacteriolysis of shuffled phage PhiX174 gene E

Bacterial ghosts that are generated using the regulated PhiX174 lysis gene E offer a new avenue for the study of inactivated vaccines. Here, we constructed a library of mutant gene E using a gene-shuffling technique. After screening and recombination with the prokaryotic non-fusion expression vector pBV220, two lysis plasmids were selected. Among which, a novel mutant E gene (named mE), consisting of a 74-bp non-encoding sequence at 5'-end and a 201-bp gene ΔE, significantly increased the lysis effect on prokaryotic Escherichia coli and Salmonella enteritidis. Moreover, lysis efficiency, as measured by the OD₆₀₀ value, reached 1.0 (10⁹ CFU), avoiding the bottleneck problem observed with other bacterial lysis procedures, which results in a low concentration of bacteria in suspension, and consequent low production of bacterial ghosts. Our results may provide a promising avenue for the development of bacterial ghost vaccines.

Salmonella enteritidis ghost vaccine induces effective protection against lethal challenge in specific-pathogen-free chicks

Bacterial ghosts (BGs) are empty bacterial envelopes generated by expulsion of the bacterial genome and cytoplasmic contents from bacterial cells, and the process is mediated by lysis protein E encoded on bacteriophage PhiX174. BGs represent a new approach in vaccine development and have been applied to a variety of gram-negative bacterial vaccine candidates. In this study, a BG vaccine generated from Salmonella enteritidis (S. enteritidis) strain DH091 was prepared using the highly efficient plasmid, pBV-mE. The efficacy of the BG vaccine was tested using 75 chicks (Gallus gallus) kept under specific pathogen-free (SPF) conditions. A comprehensive evaluation of the immune response, including humoral and cellular immune responses, interferon-γ (IFN-γ) and interleukin-4 (IL-4) production, and histopathology of various tissues, was performed in BG-vaccinated animals subsequently challenged with S. enteritidis. The results were compared with animals that were immunized with the inactivated vaccine. S. enteritidis ghosts not only promoted the generation of high titer antibodies and IFN-γ and IL-4 production but also stimulated a significant increase in CD8(+) and CD4(+) T lymphocytes. In particular, the dramatic increase in CD8(+) T cells indicated that the vaccine was able to induce clearance of intracellular Salmonella. The protective effects of BG vaccination in SPF chicks against 5×10(9) colony forming units of S. enteritidis were a result of the induction of a more effective immune response than that observed with the inactivated vaccine. These findings demonstrate the potential of S. enteritidis ghosts to be used as effective vaccines.

Effective gene transfer to melanoma cells using bacterial ghosts

Bacterial ghosts (BG) are cell envelopes preparations of Gram-negative bacteria devoid of cytoplasmic content produced by controlled expression of PhiX174 plasmid-encoded lysis gene E. Eight melanoma cell lines were investigated for their capacity to bind and phagocyte BG derived from Escherichia coli NM522 and Mannheimia haemolytica A23. High capability to bind BG was observed in almost all of the analyzed cell lines, furthermore cells were able to take up BG independently of the used bacterial species. Further, transfection efficiency of BG loaded with DNA in vitro was measured. The Bowes cells exhibited a high expression level of GFP and the incubation of cells with plasmid loaded BG led up to 82% transfection efficiency.

Bacterial ghosts as adjuvant particles

The development of more advanced and effective vaccines is of great interest in modern medicine. These new-generation vaccines, based on recombinant proteins or DNA, are often less reactogenic and immunogenic than traditional vaccines. Thus, there is an urgent need for the development of new and improved adjuvants. Besides many other immunostimulatory components, the bacterial ghost (BG) system is currently under investigation as a potent vaccine delivery system with intrinsic adjuvant properties. BGs are nonliving cell envelope preparations from Gram-negative cells, devoid of cytoplasmic contents, while their cellular morphology and native surface antigenic structures remain preserved. Owing to the particulate nature of BGs and the fact that they contain many well known immune-stimulating compounds, BGs have the potential to enhance immune responses against ghost-delivered target antigens.

Optimization and delivery of plasmid DNA for vaccination

Vaccination with DNA is one of the most promising novel immunization techniques against a variety of pathogens and tumors, for which conventional vaccination regimens have failed. DNA vaccines are able to stimulate both arms of the immune system simultaneously, without carrying the safety risks associated with live vaccines, therefore representing not only an alternative to conventional vaccines but also significant progress in the prevention and treatment of fatal diseases and infections. However, translation of the excellent results achieved in small animals to similar success in primates or large animals has so far proved to be a major hurdle. Moreover, biosafety issues, such as the removal of antibiotic resistance genes present in plasmid DNA used for vaccination, remain to be addressed adequately. This review describes strategies to improve the design and production of conventional plasmid DNA, including an overview of safety and regulatory issues. It further focuses on novel systems for the optimization of plasmid DNA and the development of diverse plasmid DNA delivery systems for vaccination purposes.

Bacterial ghosts as a novel advanced targeting system for drug and DNA delivery

Although there are powerful drugs against infectious diseases and cancer on the market, delivery systems are needed to decrease serious toxic and noncurative side effects. In order to enhance compliance, several delivery systems such as polymeric micro- and nanoparticles, liposomal systems and erythrocyte ghosts have been developed. Bacterial ghosts representing novel advanced delivery and targeting vehicles suitable for the delivery of hydrophobic or water-soluble drugs, are the main focus of this review. They are useful nonliving carriers, as they can carry different active substances in more than one cellular location separately and simultaneously. Bacterial ghosts combine excellent natural or engineered adhesion properties with versatile carrier functions for drugs, proteins and DNA plasmids or DNA minicircles. The simplicity of both bacterial ghost production and packaging of drugs and/or DNA makes them particularly suitable for the use as a delivery system. Further advantages of bacterial ghost delivery vehicles include high bioavailability and a long shelf life without the need of cold-chain storage due to the possibility to freeze-dry the material.

Bacterial ghosts as an oral vaccine: a single dose of Escherichia coli O157:H7 bacterial ghosts protects mice against lethal challenge

Enterohemorrhagic Escherichia coli (EHEC) is a bacterial pathogen that is associated with several life-threatening diseases for humans. The combination of protein E-mediated cell lysis to produce EHEC ghosts and staphylococcal nuclease A to degrade DNA was used for the development of an oral EHEC vaccine. The lack of genetic material in the oral EHEC bacterial-ghost vaccine abolished any hazard of horizontal gene transfer of resistance genes or pathogenic islands to resident gut flora. Intragastric immunization of mice with EHEC ghosts without the addition of any adjuvant induced cellular and humoral immunity. Immunized mice challenged at day 55 showed 86% protection against lethal challenge with a heterologous EHEC strain after single-dose oral immunization and 93.3% protection after one booster at day 28, whereas the controls showed 26.7% and 30% survival, respectively. These results indicate that it is possible to develop an efficacious single-dose oral EHEC bacterial-ghost vaccine.