Nanotechnology's frontier in combatting infectious and inflammatory diseases: prevention and treatment

Inflammation-associated diseases encompass a range of infectious diseases and non-infectious inflammatory diseases, which continuously pose one of the most serious threats to human health, attributed to factors such as the emergence of new pathogens, increasing drug resistance, changes in living environments and lifestyles, and the aging population. Despite rapid advancements in mechanistic research and drug development for these diseases, current treatments often have limited efficacy and notable side effects, necessitating the development of more effective and targeted anti-inflammatory therapies. In recent years, the rapid development of nanotechnology has provided crucial technological support for the prevention, treatment, and detection of inflammation-associated diseases. Various types of nanoparticles (NPs) play significant roles, serving as vaccine vehicles to enhance immunogenicity and as drug carriers to improve targeting and bioavailability. NPs can also directly combat pathogens and inflammation. In addition, nanotechnology has facilitated the development of biosensors for pathogen detection and imaging techniques for inflammatory diseases. This review categorizes and characterizes different types of NPs, summarizes their applications in the prevention, treatment, and detection of infectious and inflammatory diseases. It also discusses the challenges associated with clinical translation in this field and explores the latest developments and prospects. In conclusion, nanotechnology opens up new possibilities for the comprehensive management of infectious and inflammatory diseases.

Comparison of the immune effects of the Chlamydia abortus MOMP antigen displayed in different parts of bacterial ghosts

Bacterial ghosts (BGs) are promising vaccine platforms owing to their high adjuvant properties and delivery efficiency. Heterologous antigens can be anchored to different parts of BGs using genetic engineering strategies to prepare vaccines. However, several key issues need to be resolved, including the efficient preparation of BGs and determining the optimal anchoring position of exogenous antigens in the BGs. Here, we prepared an efficient temperature-controlled lysis system using lysis gene E of phage PhiX174 and used the major outer membrane protein (MOMP) of Chlamydia abortus (C. abortus) as a model antigen to explore the optimal display location of exogenous antigens in BGs. We demonstrated that the constructed recombinant temperature-controlled lysis plasmid can still stably inhibit E gene expression at 37°C, and the lysis efficiency of E. coli can reach above 99.9%. Four recombinant MOMP Escherichia coli (E. coli) ghost vaccines were constructed using different anchor sequences. These vaccines all induced strong specific antibody responses and secrete high levels of IFN-γ in immunized mice and significantly increased the clearance of C. abortus in a mouse infection model. Notably, the strongest immune effect was observed when MOMP was displayed on the surface of E. coli ghosts (rECG-InpN-M), which resulted in the clearance of C. abortus in mice 6 days earlier than that with the recombinant MOMP vaccine. Altogether, we constructed an efficient BG temperature-controlled lysis system and provided a feasible strategy for developing a BG delivery platform with enhanced immune effects.

Nucleic acid vaccination strategies for ovarian cancer

High grade serous carcinoma (HGSC) is one of the most lethal ovarian cancers that is characterised by asymptomatic tumour growth, insufficient knowledge of malignant cell origin and sub-optimal detection. HGSC has been recently shown to originate in the fallopian tube and not in the ovaries. Conventional treatments such as chemotherapy and surgery depend upon the stage of the disease and have resulted in higher rates of relapse. Hence, there is a need for alternative treatments. Differential antigen expression levels have been utilised for early detection of the cancer and could be employed in vaccination strategies using nucleic acids. In this review the different vaccination strategies in Ovarian cancer are discussed and reviewed. Nucleic acid vaccination strategies have been proven to produce a higher CD8+ CTL response alongside CD4+ T-cell response when compared to other vaccination strategies and thus provide a good arena for antitumour immune therapy. DNA and mRNA need to be delivered into the intracellular matrix. To overcome ineffective naked delivery of the nucleic acid cargo, a suitable delivery system is required. This review also considers the suitability of cell penetrating peptides as a tool for nucleic acid vaccine delivery in ovarian cancer.

Construction and In Vitro Evaluation of a Tumor Acidic pH-Targeting Drug Delivery System Based on Escherichia coli Nissle 1917 Bacterial Ghosts

Synthetic nanocarriers are a promising therapeutic delivery strategy. However, these systems are often hampered by inherent disadvantages such as strong biotoxicity and poor biocompatibility. To overcome these issues, biological carriers with commonly used chemotherapy drugs have been developed. In this work, engineered bacterial ghosts (BGs) originated from probiotic Escherichia coli Nissle 1917 (EcN) were devised to specifically target acidic extracellular environments of tumor tissue. To improve the production efficiency and safety, a novel lysis protein E from phage α3 was applied to produce EcN BGs under high growth densities in high quality. In addition, the acidity-triggered rational membrane (ATRAM) peptides were displayed in EcN BGs to facilitate specific cancer cell internalization within the acidic tumor microenvironment before drug release. In conclusion, the engineered EcN BGs offer a promising means for bionic bacteria construction for hepatocellular carcinoma therapy.

Recent Progress Towards a Gonococcal Vaccine

Gonorrhea is a global health concern. Its etiological agent, Neisseria gonorrhoeae, rapidly acquires antimicrobial resistance and does not confer protective immunity as a consequence of infection. Attempts to generate an effective vaccine for gonorrhea have thus far been unsuccessful, as many structures on the bacterial envelope have the propensity to rapidly change, thus complicating recognition by the human immune system. In response to recent efforts from global health authorities to spur the efforts towards development of a vaccine, several new and promising steps have been made towards this goal, aided by advancements in computational epitope identification and prediction methods. Here, we provide a short review of recent progress towards a viable gonococcal vaccine, with a focus on antigen identification and characterization, and discuss a few of the tools that may be important in furthering these efforts.

Protective Immunity against Listeria monocytogenes in Rats, Provided by HCl- and NaOH-Induced Listeria monocytogenes Bacterial Ghosts (LMGs) as Vaccine Candidates

Listeria monocytogenes (Lm) bacterial ghosts (LMGs) were produced by the minimum inhibitory concentration (MIC) of HCl, H₂SO₄, and NaOH. Acid and alkali effects on the LMGs were compared by in vitro and in vivo analyses. Scanning electron microscope showed that all chemicals form lysis pores on the Lm cell envelopes. Real-time qPCR revealed a complete absence of genomic DNA in HCl- and H₂SO₄-induced LMGs but not in NaOH-induced LMGs. HCl-, H₂SO₄- and NaOH-induced LMGs showed weaker or missing protein bands on SDS-PAGE gel when compared to wild-type Lm. Murine macrophages exposed to the HCl-induced LMGs showed higher cell viability than those exposed to NaOH-induced LMGs or wild-type Lm. The maximum level of cytokine expression (TNF-α, iNOS, IFN-γ, and IL-10 mRNA) was observed in the macrophages exposed to NaOH-induced LMGs, while that of IL-1β mRNA was observed in the macrophages exposed to HCl-induced LMGs. To investigate LMGs as a vaccine candidate, mice were divided into PBS buffer-injected, HCl- and NaOH-induced LMGs immunized groups. Mice vaccinated with HCl- and NOH-induced LMGs, respectively, significantly increased in specific IgG antibodies, bactericidal activities of serum, and CD4⁺ and CD8⁺ T-cell population. Antigenic Lm proteins reacted with antisera against HCl- and NOH-induced LMGs, respectively. Bacterial loads in HCl- and NaOH-induced LMGs immunized mice were significantly lower than PBS-injected mice after virulent Lm challenges. It suggested that vaccination with LMGs induces both humoral and cell-mediated immune responses and protects against virulent challenges.

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.

Hydrochloric acid-treated Bacillus subtilis ghosts induce IL-1 beta, IL-6, and TNF-alpha in murine macrophage

Background

Bacterial ghosts (BGs) are empty cell envelopes commonly generated using Gram-negative bacteria; they represent a potential platform for efficient adjuvant and vaccine delivery systems. However, the efficient production of BGs from bacteria in a short period of time is challenging.

Objective

The purpose of this study was to investigate the possibility of producing BGs in the Gram-positive Bacillus subtilis using various chemicals, and the potential application of BGs as a novel immunomodulatory agent.

Results

In this study, Bacillus subtilis ghosts (BSGs) were generated, for the first time to the best of our knowledge, using the minimum inhibitory concentration (MIC) of hydrochloric acid (HCl; 6.25 mg/mL), sulfuric acid (H₂SO₄; 3.125 mg/mL), and nitric acid (HNO₃; 6.25 mg/mL). Among the BSGs generated using these chemicals, HCl-induced BSGs were completely DNA-free as confirmed by real-time polymerase chain reaction. Scanning electron microscopy showed the formation of transmembrane lysis tunnel structures in HCl-induced BSGs. Murine macrophages exposed to the HCl-induced BSGs at a concentration of 1 × 10⁵ CFU/mL showed a cell viability of 97.8%. Additionally, HCl-induced BSGs upregulated the expression of pro-inflammatory cytokines including interleukin (IL)-1β, tumor necrosis factor alpha, and IL-6. Furthermore, we found differences in the protein expression profiles between intact live bacteria and BSGs using two-dimensional electrophoresis coupled with peptide mass fingerprinting/matrix-assisted laser desorption/ionization-time of flight mass spectrometry analysis.

Conclusion

These data suggest that the HCl-induced BSGs may be potentially safe and effective candidates for inactivated bacterial vaccines and/or immunostimulants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13273-022-00221-5.

Bacteria from Infectious Particles to Cell Based Anticancer Targeted Drug Delivery Systems

Bacterial ghosts (BGs) are empty cell envelopes of nonliving evacuated bacterial cells. They are free from their cytoplasmic contents; however, they sustain their cellular 3D morphology and antigenic structures, counting on bioadhesive properties. Lately, they have been tested as an advanced drug delivery system (DDS) for different materials like DNA, peptides, or drugs, either single components or combinations. Different studies have revealed that, BG DDS were paid the greatest attention in recent years. The current review explores the impact of BGs on the field of drug delivery and drug targeting. BGs have a varied area of applications, including vaccine and tumor therapy. Moreover, the use of BGs, their synthesis, their uniqueness as a delivery system and application principles in cancer are discussed. Furthermore, the safety issues of BGs and stability aspects of using ghost bacteria as delivery systems are discussed. Future perspective efforts that must be followed for this important system to continue to grow are important and promising.

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.

Design, development, and evaluation of the efficacy of a nucleic acid-free version of a bacterial ghost candidate vaccine against avian pathogenic E. coli (APEC) O78:K80 serotype

One of the major bacterial infectious diseases in the poultry industry is avian pathogenic Escherichia coli (APEC), which causes colibacillosis in chickens. To develop a novel nucleic acid-free bacterial ghost (BG) vaccine against the O78:K80 serotype of APEC, in this study we constructed a plasmid that harbored E-lysis and S nuclease (SNUC). Following the expression, the O78:K80 bacteria lost all of their cytoplasmic content and nucleic acids by enzymatic digestion. The functionality of these two proteins in the production procedure of bacterial ghosts was confirmed by monitoring the number of colonies, scanning electron microscopy imaging, gel electrophoresis of genomic DNA, and qPCR on the plasmid content of bacterial ghosts. The protective efficacy of the ghost vaccine generated from O78:K80 serotype of APEC was tested in chickens by injection and inhalation routes and compared with that in chickens that received the injection of a killed vaccine. The O78:K80 BG vaccine candidate, used as injection and inhalation, in comparison with the killed vaccine, triggered higher proinflammatory cytokine expression including IL-6, IL-1β, and TNFSF15; a higher level of antibody-dependent humoral (IgY and IgA) and cellular immune responses (IFNγ and lymphocyte proliferation); and lower lesion scores. According to the results of this study, we suggest that the bacterial ghost technology has the potential to be applied for the development of novel vaccines against avian colibacillosis. This technology provides an effective and reliable approach to make multivalent vaccines for more prevalent APEC strains involved in the establishment of this infectious disease in the poultry industry.

Recombinant Vibrio parahaemolyticus ghosts protect zebrafish against infection by Vibrio species

Aquatic animals are frequently threated by bacterial pathogens. The most economic and efficient protection against bacterial infection are through vaccine immunization. The various serotypes of the pathogens, such as Vibrios, hurdle the development of the vaccines, especially polyvalent vaccines. Here, we demonstrate that recombinant bacterial ghost is a good candidate for multivalent vaccine. By expressing PhiX174 gene E alone or co-expressing the gene E with two genes encoding outer membrane proteins (VP1667 and VP2369) in V. parahaemolyticus, we generated the recombinant V. parahaemolyticus ghosts VPG and rVPGs respectively. Fish immunized with either VPG or rVPG showed increased survival against the infection by either V. parahaemolyticus or V. alginolyticus, with a better protective effect by immunization with rVPG. Our furthermore studies show that rVPG stimulates stronger innate immune responses by increasing the expression of tnfα, il1β, il6, il8 and il10 as well as that of c3b, lyz, and tlr5, the key players linking the innate and adaptive immune responses upon microbial stimulation. In summary, VPG and rVPG can protect zebrafish against the infection from at least two Vibrio species, suggesting its potential value for further aquaculture vaccines development.

Enhancement of immune responses by co-administration of bacterial ghosts-mediated Neisseria gonorrhoeae DNA vaccines

AIM

Gonorrhoea remains a leading public health burden and the development of vaccine against gonorrhoea becomes more urgent. Here, a novel Neisseria gonorrhoeae DNA vaccine delivered by Salmonella enteritidis ghosts was developed and the immune responses of the vaccine candidate were evaluated.

METHODS AND RESULTS

Neisseria gonorrhoeae nspA gene was cloned into the pVAX1 vector. The constructed recombinant plasmid pVAX1-nspA was loaded into the lyophilized SE ghosts to produce SE ghosts (pVAX1-nspA). Then, the immune responses induced by SE ghosts (pVAX1-nspA) alone and co-administrated with SE ghosts (pVAX1-porB) were evaluated in mouse model. Co-administered SE ghosts (pVAX1-nspA) and SE ghosts (pVAX1-porB) could elicited significantly higher levels of specific IgG antibody responses and lymphocyte proliferative responses than the control groups. Furthermore, the group co-administered SE ghosts (pVAX1-nspA) and SE ghosts (pVAX1-porB) had the highest bactericidal antibody titres.

CONCLUSIONS

Co-administration of SE ghosts (pVAX1-nspA) and SE ghosts (pVAX1-porB) elicited significant specific humoral and cellular immune responses.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrates the potential of co-administration of SE ghosts (pVAX1-nspA) and SE ghosts (pVAX1-porB) as an attractive vaccination regimen for gonorrhoea.

Vision of bacterial ghosts as drug carriers mandates accepting the effect of cell membrane on drug loading

The use of bacterial ghosts (BGs) for drug delivery is an extremely fascinating perspective especially with the inherited efficient target-ability to specialized tissues. Trafficking of drug molecules across the outer membrane of Gram-negative bacteria are important to be understood for both loading (influx) and drug release (efflux). In this study, Escherichia coli (E. coli) BGs were prepared using modified protocol sponge-like reduced protocol (SLRP) which was used for loading of doxorubicin (DOX). First time in the literature, different possible factors affecting DOX loading from BGs were examined in this study. These factors including drug concentration, temperature, pH gradient, incubation time and tonicity, are proposed to effect on drug loading into E. coli BGs. Results of optimum effect from accompanied factors were found to be 10 mg/mL as DOX concentration at pH 6 with tonicity of 0.7% incubated overnight at 4 °C. After gather all factors, the amount of DOX loaded inside the BGs was recorded as 37.58%. The in vitro release studies of DOX loaded BGs over time showed a burst initial release rate of 26.75% at the first 12 h followed by a period of sustained release lasting for 16 days to give maximum release rate of 58.04%. Remarkably, DOX loaded in BG showed more apoptosis (55%) than control and DOX solution. Overall, the results indicated the presence of some important factors to be controlled when loading drugs into BGs. Also, data showed the future possibility of utilizing BGs to deliver DOX to colon cancer cells.

Bioengineered smart bacterial carriers for combinational targeted therapy of solid tumours

Despite many endeavours for the development of new anticancer drugs, effective therapy of solid tumours remains a challenging issue. The current cancer chemotherapies may associate with two important limitations, including the lack/trivial specificity of treatment modalities towards diseased cells/tissues resulting in undesired side effects, and the emergence of drug-resistance mechanisms by tumour cells causing the failure of the treatment. Much attention, therefore, has currently been paid to develop smart and highly specific anticancer agents with maximal therapeutic impacts and minimal side effects. Among various strategies used to target cancer cells, bacteria-based cancer therapies (BCTs) have been validated as potential gene/drug delivery carriers, which can also be engineered to be used in diagnosis processes. They can be devised to selectively target the tumour microenvironment (TME), within which they may preferentially proliferate in the necrotic and anaerobic parts - often inaccessible to other therapeutics. BCTs are capable to sense and respond to the environmental signals, upon which they are considered as smart microrobots applicable in the controlled delivery of therapeutic agents to the TME. In this review, we aimed to provide comprehensive insights into the potentials of the bioengineered bacteria as smart and targeted bio-carriers and discuss their applications in cancer therapy.

Adjuvants and delivery systems based on polymeric nanoparticles for mucosal vaccines

Most pathogens enter the body through mucosal surfaces. Therefore, vaccination through the mucosal route can greatly enhance the mucosal immune response. Vaccination via the mucosal surface is the most effective way to trigger a protective mucosal immune response, but the vast majority of vaccines used are administered by injection. Strategies to enhance the mucosal immunity have been developed by using vaccine adjuvants, delivery systems, bacterial or viral vectors, and DNA vaccines. Appropriate vaccine adjuvants and drug delivery systems can improve the immunogenicity of antigens, induce a stronger immune response, and reduce the vaccine dose and production cost. In recent years, many studies have focused on finding safe and effective vaccine adjuvants and drug delivery systems to formulate the mucosal vaccines for solving the above problems. Great progress has also been made in vaccine adjuvants and drug delivery systems based on biodegradable polymer nanoparticles. In this paper, the research progress of the mucosal vaccine and its related adjuvants and drug delivery systems in recent years was reviewed, and the application of polymers as adjuvants and drug delivery system in vaccine was prospected. This review provides a fundamental knowledge for the application of biodegradable polymer nanoparticles as adjuvants and carriers in mucosal vaccines and shows great application prospects.

Subcutaneous Immunization of Dogs With Bordetella bronchiseptica Bacterial Ghost Vaccine

The Bordetella species are Gram-negative bacterial pathogens that colonizes mammalian respiratory tract causing respiratory diseases in humans and animals. B. bronchiseptica causes clinical conditions in many mammals including immunocompromised humans. Using the dog model of respiratory infection, it has been shown in this study that a newly developed B. bronchiseptica Bacterial Ghost (BbBG) vaccine exhibited significant protection in the face of a severe pathogenic bacterial challenge in seronegative dogs. The protein E-specific lysis mechanism was used to produce BbBGs. Bacterial Ghosts (BGs) are the empty cell envelope of Gram-negative bacterium. They are genetically processed to form a microscopic hole in their membrane, through which all the cytoplasmic contents are expelled leaving behind intact empty bacterial shells. Due to the intact surface structures of BGs, they offer the safety of inactivated but efficacy of live attenuated vaccines. In this study, seronegative dogs were vaccinated subcutaneously (s/c) with two different doses of a newly developed BbBG vaccine [lower 10^∧5 (BbBG – 5) and higher 10^∧7 (BbBG – 7)] on day 0 and 21. The animals were challenged (by aerosol) with virulent live B. bronchiseptica strains 41 days after first vaccination. The dogs vaccinated s/c with BbBG – 7 vaccine had significantly lower spontaneous coughing scores (P = 0.0001) than dogs in negative control group. Furthermore, the tested BbBG – 7 vaccine was equivalent to the positive control vaccine Bronchicine CAe in terms of safety and efficacy. For the first time, we report the successful use of liquid formulated BGs vaccines in animal studies. Earlier reported studies using BGs vaccines were performed with resuspended freeze-dried BGs preparations.

Construction of Lactobacillus casei ghosts by Holin-mediated inactivation and the potential as a safe and effective vehicle for the delivery of DNA vaccines

BACKGROUND

Bacterial ghosts (BGs) are empty bacterial cell envelopes generated by releasing the cellular contents. In this study, a phage infecting Lactobacillus casei ATCC 393 (L. casei 393) was isolated and designated Lcb. We aimed at using L. casei 393 as an antigen delivery system to express phage-derived holin for development of BGs.

RESULTS

A gene fragment encoding holin of Lcb (hocb) was amplified by polymerase chain reaction (PCR). We used L. casei 393 as an antigen delivery system to construct the recombinant strain pPG-2-hocb/L. casei 393. Then the recombinants were induced to express hocb. The immunoreactive band corresponding to hocb was observed by western-blotting, demonstrating the efficiency and specificity of hocb expression in recombinants. The measurements of optical density at 600 nm (OD₆₀₀₎ after induction showed that expression of hocb can be used to convert L. casei cells into BGs. TEM showed that the cytomembrane and cell walls of hocb expressing cells were partially disrupted, accompanied by the loss of cellular contents, whereas control cells did not show any morphological changes. SEM showed that lysis pores were distributed in the middle or at the poles of the cells. To examine where the plasmid DNA was associated, we analyzed the L. casei ghosts loading SYBR Green I labeled pCI-EGFP by confocal microscopy. The result demonstrated that the DNA interacted with the inside rather than with the outside surface of the BGs. To further analyze where the DNA were loaded, we stained BGs with MitoTracker Green FM and the loaded plasmids were detected using EGFP-specific Cy-3-labeled probes. Z-scan sections through the BGs revealed that pCI-EGFP (red) was located within the BGs (green), but not on the outside. Flow cytometry and qPCR showed that the DNA was loaded onto BGs effectively and stably.

CONCLUSIONS

Our study constructed L. casei BGs by a novel method, which may be a promising technology for promoting the further application of DNA vaccine, providing experimental data to aid the development of other Gram-positive BGs.

Bacterial components as naturally inspired nano-carriers for drug/gene delivery and immunization: Set the bugs to work?

Drug delivery is a rapidly growing area of research motivated by the nanotechnology revolution, the ideal of personalized medicine, and the desire to reduce the side effects of toxic anti-cancer drugs. Amongst a bewildering array of different nanostructures and nanocarriers, those examples that are fundamentally bio-inspired and derived from natural sources are particularly preferred. Delivery of vaccines is also an active area of research in this field. Bacterial cells and their components that have been used for drug delivery, include the crystalline cell-surface layer known as "S-layer", bacterial ghosts, bacterial outer membrane vesicles, and bacterial products or derivatives (e.g. spores, polymers, and magnetic nanoparticles). Considering the origin of these components from potentially pathogenic microorganisms, it is not surprising that they have been applied for vaccines and immunization. The present review critically summarizes their applications focusing on their advantages for delivery of drugs, genes, and vaccines.

Bacterial ghosts as adjuvant to oxaliplatin chemotherapy in colorectal carcinomatosis

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers and a major cause of cancer mortality worldwide. At late stage of the disease CRC often shows (multiple) metastatic lesions in the peritoneal cavity which cannot be efficiently targeted by systemic chemotherapy. This is one major factor contributing to poor prognosis. Oxaliplatin is one of the most commonly used systemic treatment options for advanced CRC. However, drug resistance - often due to insufficient drug delivery - is still hampering successful treatment. The anticancer activity of oxaliplatin includes besides DNA damage also a strong immunogenic component. Consequently, the aim of this study was to investigate the effect of bacterial ghosts (BGs) as adjuvant immunostimulant on oxaliplatin efficacy. BGs are empty envelopes of gram-negative bacteria with a distinct immune-stimulatory potential. Indeed, we were able to show that the combination of BGs with oxaliplatin treatment had strong synergistic anticancer activity against the CT26 allograft, resulting in prolonged survival and even a complete remission in this murine model of CRC carcinomatosis. This synergistic effect was based on an enhanced induction of immunogenic cell death and activation of an efficient T-cell response leading to long-term anti-tumor memory effects. Taken together, co-application of BGs strengthens the immunogenic component of the oxaliplatin anticancer response and thus represents a promising natural immune-adjuvant to chemotherapy in advanced CRC.

Current challenges for cancer vaccine adjuvant development

INTRODUCTION

Although much progress has been made in the last decade(s) toward development of effective cancer vaccines, there are still important obstacles to therapeutic successes. New generations of cancer vaccines will benefit from a combination adjuvant approach that targets multiple branches of the immune response.

AREAS COVERED

Herein we describe how combinatorial adjuvant strategies can help overcome important obstacles to cancer vaccine development, including antigen immunogenicity and tumor immune suppression. Tumor antigens may be both tolerogenic and may utilize active mechanisms to suppress host immunity, including downregulation of MHC molecules to evade recognition and upregulation of immune inhibitory receptors, to subvert an effective immune response. The current cancer vaccine literature was surveyed to identify advancements in the understanding of the biological mechanisms underlying poor antigen immunogenicity and tumor immune evasion, as well as adjuvant strategies designed to overcome them.

EXPERT COMMENTARY

Poor immunogenicity of tumor antigens and tumor immune evasion mechanisms make the design of cancer vaccines challenging. Growing understanding of the tumor microenvironment and associated immune responses indicate the importance of augmenting not only the effector response, but also overcoming the endogenous regulatory response and tumor evasion mechanisms. Therefore, new vaccines will benefit from multi-adjuvanted approaches that simultaneously stimulate immunity while preventing inhibition.

Protective immunity of grass carp induced by DNA vaccine encoding capsid protein gene (vp7) of grass carp reovirus using bacterial ghost as delivery vehicles

Grass carp reovirus (GCRV) is one of the most pathogenic aquareovirus and can cause lethal hemorrhagic disease in grass carp (Ctenopharyngodon idella). However, management of GCRV infection remains a challenge. Therefore, it is necessary to find effective means for the control of its infection. The uses of bacterial ghost (BG, non-living bacteria) as carriers for DNA delivery have received considerable attentions in veterinary and human vaccines studies. Nevertheless, there is still no report about intramuscular administration of bacterial ghost-based DNA vaccines in fish. In the current study, a novel vaccine based on Escherichia coli DH5α bacterial ghost (DH5α-BG), delivering a major capsid protein gene (vp7) of grass carp reovirus encoded DNA vaccine was developed to enhance the efficacy of a vp7 DNA vaccine against GCRV in grass carp. The grass carp was injected intramuscularly by different treatments -i) naked pcDNA-vp7 (containing plasmid 1, 2.5 and 5 μg, respectively), ii) DH5α-BG/pcDNA-vp7 (containing plasmid 1, 2.5 and 5 μg, respectively) and iii) naked pcDNA, DH5α-BG or phosphate buffered saline. The immune responses and disease resistance of grass carp were assessed in different groups, and results indicated that the antibody levels, serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, acid phosphatase (ACP) activity and alkaline phosphatase (AKP) activity and immune-related genes were significantly enhanced in fish immunized with DH5α-BG/pcDNA-vp7 vaccine (DNA dose ranged from 2.5 to 5 μg). In addition, the relative percentage survival were significantly enhanced in fish immunized with DH5α-BG/pcDNA-vp7 vaccine and the relative percentage survival reached to 90% in DH5α-BG/pcDNA-vp7 group than that of naked pcDNA-vp7 (42.22%) at the highest DNA dose (5 μg) after 14 days of post infection. Moreover, the level of pcDNA-vp7 plasmid was higher in DH5α-BG/pcDNA-vp7 groups than naked pcDNA-vp7 groups in muscle and kidneys tissues after 21 days. Overall, those results suggested that DH5α bacterial ghost based DNA vaccine might be used as a promising vaccine for aquatic animals to fight against GCRV infection.

The study of H. pylori putative candidate factors for single- and multi-component vaccine development

Helicobacter pylori has grown to colonize inside the stomach of nearly half of the world's population, turning into the most prevalent infections in the universe. Medical care failures noticeably confirm the need for a vaccine to hinder or deal with H. pylori. This review is planned to discuss the most known factors as a vaccine candidate, including single (AhpC, BG, CagA, KatA, Fla, Hsp, HWC, Lpp, LPS, NAP, OMP, OMV, SOD, Tpx, Urease, VacA) and multi-component vaccines. Many promising results in the field of single and multivalent vaccine can be seen, but there is no satisfactory outcome and neither a prophylactic nor a therapeutic vaccine to treat or eradicate the infection in human has been acquired. Hence, selecting suitable antigen is an important factor as an appropriate adjuvant. Taken all together, the development of efficient anti-H. pylori vaccines relies on the fully understanding of the interactions between H. pylori and its host immune system. Therefore, more work should be done on epitope mapping, analysis of molecular structure, and determination of the antigen determinant region as well due to design a vaccine, preferably a multi-component vaccine to elicit specific CD4 T-cell responses that are required for H. pylori vaccine efficacy.

A bacterial ghost improves the immunological efficacy of a Newcastle disease virus inactivated vaccine

Newcastle disease (ND) is one of the most common contagious viral infectious diseases of poultry. Vaccination is an effective way to protect chickens from Newcastle disease virus (NDV), and large efforts have been made to acquire not only new vaccines but also new adjuvants to improve the efficiency of existing inactivated vaccines. Here, we observed the adjuvanticity of the bacterial ghost (BG) on the effectiveness of inactivated NDV vaccine in a chicken model. We found that BG, as an adjuvant with inactivated NDV vaccine, substantially strengthened the ND-specific antibody response and protection against lethal challenge in a chicken model, reduced viral shedding, strengthened the time duration of antibody titers, produced an available immunization effect with a low dose of vaccine, and improved serum IL-2 and IFN-γ concentrations. Our results demonstrate that BG significantly improved the immunogenicity of an inactivated NDV vaccine and is a new immune adjuvant candidate.

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.

Bacterial ghosts as adjuvants in syngeneic tumour cell lysate-based anticancer vaccination in a murine lung carcinoma model

Instead of relying on external anticancer factors for treatment, immunotherapy utilizes the host's own immune system and directs it against given tumour antigens. This study demonstrated that it is possible to overcome the documented immunosuppressive properties of tumour cell lysate by supplementing it with appropriate adjuvant. Lewis lung carcinoma (LLC)‑challenged C57BL/6 mice were treated with LLC cryo‑lysate mixed with either bacterial ghosts (BGs) generated from E. coli Nissle 1917 or B. subtilis 70 kDa protein as adjuvants. Median and overall survival, the size of metastatic foci in lung tissue and levels of circulating CD8a+ T cells were evaluated and compared to the untreated control mice or mice treated with LLC lysate alone. After primary tumour removal, a course of three subcutaneous vaccinations with LLC lysate supplemented with BGs led to a significant increase in overall survival (80% after 84 days of follow‑up vs. 40% in untreated control mice), a significant increase in circulating CD8a+ T cells (16.57 vs. 12.6% in untreated control mice) and a significant decrease in metastasis foci area and incidence. LLC lysate supplemented with B. subtilis protein also improved the inspected parameters in the treated mice, when compared against the untreated control mice, but not to a significant degree. Therefore, whole cell lysate supplemented with BGs emerges as an immunostimulatory construct with potential clinical applications in cancer treatment.

Characterization of Chemically-Induced Bacterial Ghosts (BGs) Using Sodium Hydroxide-Induced Vibrio parahaemolyticus Ghosts (VPGs)

Acellular bacterial ghosts (BGs) are empty non-living bacterial cell envelopes, commonly generated by controlled expression of the cloned lysis gene E of bacteriophage PhiX174. In this study, Vibrio parahaemolyticus ghosts (VPGs) were generated by chemically-induced lysis and the method is based on minimum inhibitory concentration (MIC) of sodium hydroxide (NaOH), acetic acid, boric acid, citric acid, maleic acid, hydrochloric acid, and sulfuric acid. The MIC values of the respective chemicals were 3.125, 6.25, <50.0, 25.0, 6.25, 1.56, and 0.781 mg/mL. Except for boric acid, the lysis efficiency reached more than 99.99% at 5 min after treatment of all chemicals. Among those chemicals, NaOH-induced VPGs appeared completely DNA-free, which was confirmed by quantitative real-time PCR. Besides, lipopolysaccharides (LPS) extracted from the NaOH-induced VPGs showed no distinctive band on SDS-PAGE gel after silver staining. On the other hand, LPS extracted from wild-type bacterial cells, as well as the organic acids-induced VPGs showed triple major bands and LPS extracted from the inorganic acids-induced VPGs showed double bands. It suggests that some surface structures in LPS of the NaOH-induced VPGs may be lost, weakened, or modified by the MIC of NaOH. Nevertheless, Limulus amoebocyte lysate assay revealed that there is no significant difference in endotoxic activity between the NaOH-induced VPGs and wild-type bacterial cells. Macrophages exposed to the NaOH-induced VPGs at 0.5 × 10⁶ CFU/mL showed cell viability of 97.9%, however, the MIC of NaOH did not reduce the cytotoxic effect of wild-type bacterial cells. Like Escherichia coli LPS, the NaOH-induced VPGs are an excellent activator of pro-inflammatory cytokines (IL-1β and iNOS), anti-inflammatory cytokine (IL-10), and dual activities (IL-6) in the stimulated macrophage cells. On the other hand, the induction of TNF-α mRNA was remarkable in the macrophages exposed with wild-type cells. Scanning electron microscopy showed the formation of trans-membrane lysis tunnel structures in the NaOH-induced VPGs. SDS-PAGE and agarose gel electrophoresis also confirmed that cytoplasmic proteins and genomic DNA released from the VPGs to culture medium through the lysis tunnel structures. Taken together, all these data indicate that the NaOH-induced VPGs show the potency of a safe, economical, and effective inactivated bacterial vaccine candidate.

Genetic engineering of probiotic Escherichia coli Nissle 1917 for clinical application

Escherichia coli strain Nissle 1917 (EcN) has been used as a probiotic. Genetic engineering has enhanced the utility of EcN in several vaccine and pharmaceutical preparations. We discuss in this mini review the genetics and physical properties of EcN. We also discuss the numerous genetic engineering strategies employed for EcN-based vaccine development, including recombinant plasmid transfer, genetic engineering of cryptic plasmids or the EcN chromosome, EcN bacterial ghosts and its outer membrane vesicles. We also provide a current update on the progress and the challenges regarding the use of EcN in vaccine development.

Magnetic Ganoderma lucidum spore microspheres: A novel material to immobilize CotA multicopper oxidase for dye decolorization

In this study, hollow microspheres were obtained from Ganoderma lucidum spores. Then the hollow microspheres were loaded with Fe3O4 nanoparticles to prepare novel magnetic spore microspheres. TEM images and X-ray diffractometry demonstrated that the Fe3O4 nanoparticles were incorporated throughout the spore microsphere. CotA multicopper oxidase was chosen as biomacromolecule to study the loading ability of the magnetic spore microspheres. The combination of the CotA enzyme with the microsphere was observed by laser scanning confocal microscope. The loaded amount of CotA on the microspheres was 75mg/g when the CotA concentration was 1.2mg/mL and the activity recovery of the immobilized CotA was 81%. The magnetic microspheres loaded with CotA, which can be easily and quickly recovered by an external magnetic field, were used for dye decolorization. After 1h decolorization, 99% of the indigo carmine has been removed by 10mg microspheres. In addition, the immobilized CotA retained 75% of activity after 10 consecutive cycles, which indicated that the magnetic spore microspheres are good support material for immobilization of the enzyme.

In vitro responses of chicken macrophage-like monocytes following exposure to pathogenic and non-pathogenic E. coli ghosts loaded with a rational design of conserved genetic materials of influenza and Newcastle disease viruses

Avian influenza virus (AIV) and Newcastle disease virus (NDV) are two important viral diseases in the poultry industry. Therefore, new disease-fighting strategies, especially effective genetic vaccination, are in high demand. Bacterial Ghost (BG) is a promising platform for delivering genetic materials to macrophages, cells that are among the first to encounter these viruses. However, there is no investigation on the immune response of these macrophage-targeted treatments. Here, we investigated the effect of genetic materials of AIV and NDV on the gene expression profile of important pro-inflammatory cytokines, a chemokine, a transcription factor, major histocompatibility complexes, and the viability of the chicken macrophage-like monocyte cells (CMM). Our genetic construct contained the external domain of matrix protein 2 and nucleoprotein gene of AIV, and immunodominant epitopes of fusion and hemagglutinin-neuraminidase proteins of NDV (hereinafter referred to as pAIV-Vax), delivered via the pathogenic and non-pathogenic BGs (Escherichia coli O78K80 and E. coli TOP10 respectively). The results demonstrated that both types of BGs were able to efficiently deliver the construct to the CMM, although the pathogenic strain derived BG was a significantly better stimulant and delivery vehicle. Both BGs were safe regarding LPS toxicity and did not induce any cell death. Furthermore, the loaded BGs were more powerful in modulating the pro-inflammatory cytokines' responses and antigen presentation systems in comparison to the unloaded BGs. Nitric oxide production of the BG-stimulated cells was also comparable to those challenged by the live bacteria. According to the results, the combination of pAIV-Vax construct and E. coli O78K80 BG is promising in inducing a considerable innate and adaptive immune response against AIV-NDV and perhaps the pathogenic E. coli, provided that the current combination be a potential candidate for in vivo testing regarding the development of an effective trivalent DNA vaccine against avian influenza and Newcastle disease, as well as a bacterial ghost vaccine against avian pathogenic E. coli (APEC).

Evaluation of protective efficacy of a novel inactivated Salmonella Pullorum ghost vaccine against virulent challenge in chickens

Salmonella Gallinarum biovar Pullorum is the causative agent of pullorum disease in poultry, an acute systemic disease that results in a high mortality rate in young chickens. Vaccines have been considered in many developing countries where levels of infection are high and eradication is not a realistic option. An attenuated strain combined with protein E-mediated cell lysis was used to generate a safety enhanced Salmonella Pullorum ghost vaccine. Immune responses and protection induced by ghost vaccine in chickens were investigated following a prime-boost immunization administered via intramuscular and oral routes. Chickens from vaccinated groups showed significant increases in antigen-specific IgG, especially after booster immunization. Lymphocyte proliferation responses were also significantly increased in all immunized groups at 2-weeks post-final vaccination. The Salmonella Pullorum ghost vaccine provided satisfactory protection against virulent Salmonella Pullorum infection, as shown by the robust stimulation of both humoral and cell-mediated immune responses as well as the reduction in the number of bacterial recovered post-challenge. Moreover, the immune effects and survival rates indicated intramuscular injection is more efficient than oral vaccination. In conclusion, our results suggest that Salmonella Pullorum ghosts may be used as a safe and effective novel inactivated vaccine candidate to protect against virulent Salmonella Pullorum infection.

Fed-Batch Production of Bacterial Ghosts Using Dielectric Spectroscopy for Dynamic Process Control

The Bacterial Ghost (BG) platform technology evolved from a microbiological expression system incorporating the ϕX174 lysis gene E. E-lysis generates empty but structurally intact cell envelopes (BGs) from Gram-negative bacteria which have been suggested as candidate vaccines, immunotherapeutic agents or drug delivery vehicles. E-lysis is a highly dynamic and complex biological process that puts exceptional demands towards process understanding and control. The development of a both economic and robust fed-batch production process for BGs required a toolset capable of dealing with rapidly changing concentrations of viable biomass during the E-lysis phase. This challenge was addressed using a transfer function combining dielectric spectroscopy and soft-sensor based biomass estimation for monitoring the rapid decline of viable biomass during the E-lysis phase. The transfer function was implemented to a feed-controller, which followed the permittivity signal closely and was capable of maintaining a constant specific substrate uptake rate during lysis phase. With the described toolset, we were able to increase the yield of BG production processes by a factor of 8–10 when compared to currently used batch procedures reaching lysis efficiencies >98%. This provides elevated potentials for commercial application of the Bacterial Ghost platform technology.

Delivery of a Chlamydial Adhesin N-PmpC Subunit Vaccine to the Ocular Mucosa Using Particulate Carriers

Trachoma, caused by the intracellular bacterium Chlamydia trachomatis (Ct), remains the world's leading preventable infectious cause of blindness. Recent attempts to develop effective vaccines rely on modified chlamydial antigen delivery platforms. As the mechanisms engaged in the pathology of the disease are not fully understood, designing a subunit vaccine specific to chlamydial antigens could improve safety for human use. We propose the delivery of chlamydia-specific antigens to the ocular mucosa using particulate carriers, bacterial ghosts (BGs). We therefore characterized humoral and cellular immune responses after conjunctival and subcutaneous immunization with a N-terminal portion (amino acid 1-893) of the chlamydial polymorphic membrane protein C (PmpC) of Ct serovar B, expressed in probiotic Escherichia coli Nissle 1917 bacterial ghosts (EcN BGs) in BALB/c mice. Three immunizations were performed at two-week intervals, and the immune responses were evaluated two weeks after the final immunization in mice. In a guinea pig model of ocular infection animals were immunized in the same manner as the mice, and protection against challenge was assessed two weeks after the last immunization. N-PmpC was successfully expressed within BGs and delivery to the ocular mucosa was well tolerated without signs of inflammation. N-PmpC-specific mucosal IgA levels in tears yielded significantly increased levels in the group immunized via the conjunctiva compared with the subcutaneously immunized mice. Immunization with N-PmpC EcN BGs via both immunization routes prompted the establishment of an N-PmpC-specific IFNγ immune response. Immunization via the conjunctiva resulted in a decrease in intensity of the transitional inflammatory reaction in conjunctiva of challenged guinea pigs compared with subcutaneously and non-immunized animals. The delivery of the chlamydial subunit vaccine to the ocular mucosa using a particulate carrier, such as BGs, induced both humoral and cellular immune responses. Further investigations are needed to improve the immunization scheme and dosage.

Escherichia coli Nissle 1917 bacterial ghosts retain crucial surface properties and express chlamydial antigen: an imaging study of a delivery system for the ocular surface

To target chronic inflammatory ocular surface diseases, a drug delivery platform is needed that is safe, possesses immunomodulatory properties, and can be used either for drug delivery, or as a foreign antigen carrier. A new therapeutic approach that we have previously proposed uses nonliving bacterial ghosts (BGs) as a carrier-delivery system which can be engineered to carry foreign antigens and/or be loaded with therapeutic drugs. The parent strain chosen for development of our BG delivery system is the probiotic Escherichia coli strain Nissle 1917 (EcN), whose intrinsic properties trigger the innate immune system with the flagella and fimbriae used to attach and stimulate epithelial cells. In previous studies, we have shown that EcN BGs are safe for the ocular surface route, but evidence that EcN BGs retain flagella and fimbriae after transformation, has never been visually confirmed. In this study, we used different visualization techniques to determine whether flagella and fimbriae are retained on EcN BGs engineered either for drug delivery or as a foreign antigen carrier. We have also shown by immunoelectron microscopy that EcN retains two foreign antigens after processing to become EcN BGs. Furthermore, we demonstrated that BGs derived from EcN and expressing a foreign antigen attachment to conjunctival epithelial cells in vitro without causing reduced cell viability. These results are an important step in constructing a delivery system based on a nonliving probiotic that is suitable for use in ocular surface diseases pairing immunomodulation and targeted delivery.

Helicobacter pylori outer inflammatory protein DNA vaccine-loaded bacterial ghost enhances immune protective efficacy in C57BL/6 mice

Helicobacter pylori (H. pylori) infection is associated with incidents of gastrointestinal diseases in half of the human population. However, management of its infection remains a challenge. Hence, it is necessary to develop an efficient vaccine to fight against this pathogen. In the present study, a novel vaccine based on the production of attenuated Salmonella typhimurium bacterial ghost (SL7207-BG), delivering H. pylori outer inflammatory protein gene (oipA) encoded DNA vaccine was developed, and the efficiency was evaluated in C57BL/6 mice. Significant higher levels of IgG2a/IgG1 antibodies and IFN-γ/IL-4 cytokines were detected after mice were oral administered with oipA DNA vaccine loaded SL7207-BG, indicating that a mixed Th1/Th2 immune response was elicited. When challenged with infective doses H. pylori strain SS1, the ghost based vaccine was capable of reducing bacterium colonization in the vaccinated mice. In addition, codon-optimized oipA plasmid loaded SL7207-BG significantly eliminates H. pylori colonization density in mice model. Thus, it has been demonstrated that this novel bacterial ghost based DNA vaccine could be used as a promising vaccine candidate for the control of H. pylori infection.

Cell-penetrating peptides mediated protein cross-membrane delivery and its use in bacterial vector vaccine

It is an attractive strategy to develop a recombinant bacterial vector vaccine by expressing exogenous protective antigen to induce the immune response, and the main concern is how to enhance the cellular internalization of antigen produced by bacterial vector. Cell-penetrating peptides (CPPs) are short cationic/amphipathic peptides which facilitate cellular uptake of various molecular cargoes and therefore have great potentials in vector vaccine design. In this work, eleven different CPPs were fused to the C-terminus of EGFP respectively, and the resultant EGFP-CPP fusion proteins were expressed and purified to assay their cross-membrane transport in macrophage J774 A.1 cells. Among the tested CPPs, TAT showed an excellent capability to deliver the cargo protein EGFP into cytoplasm. In order to establish an efficient antigen delivery system in Escherichia coli, the EGFP-TAT synthesis circuit was combined with an in vivo inducible lysis circuit PviuA-E in E. coli to form an integrated antigen delivery system, the resultant E. coli was proved to be able to lyse upon the induction of a mimic in vivo signal and thus release intracellular EGFP-TAT intensively, which were assumed to undergo a more efficient intracellular delivery by CPP to evoke protective immune responses. Based on the established antigen delivery system, the protective antigen gene flgD from an invasive intracellular fish pathogen Edwardsiella tarda EIB202, was applied to establish an E. coli recombinant vector vaccine. This E. coli vector vaccine presented superior immune protection (RPS = 63%) under the challenge with E. tarda EIB202, suggesting that the novel antigen delivery system had great potential in bacterial vector vaccine applications.

Evaluation the surface antigen of the Salmonella typhimurium ATCC 14028 ghosts prepared by "SLRP"

Recently, bacterial ghosts (BGs) were prepared using a protocol based on critical chemical concentrations. It has been given the name "sponge like" (SL) protocol and used in its reduced form "sponge like reduced protocol" (SLRP). While specific antibody for Salmonella is available on the market under the commercial names (of some kits) such as Febrile Antigen Kit (N.S. BIO-TEC), we used the described Kit to investigate the validity of the SLRP. In this study, using SLRP we succeeded to prepare STGs with correct surface antigens could interact with their specific antibodies. Additionally the study has included oral vaccination with STGs with challenge test. The rats serums have been evaluated against both of the O and H antigens. The antigen-antibody interaction (agglutination) results of both the SLRP and the animal experiments prove that we have correct STGs able to immunize the rats against viable Salmonella. STGs could be used as vaccine and as adjuvant and in the antibodies and in the diagnostic kits production. This study is an additional step for the establishment of correct BGs for immunological purposes.

Immune adjuvants as critical guides directing immunity triggered by therapeutic cancer vaccines

Tumor growth is controlled by natural antitumor immune responses alone or by augmented immune reactivity resulting from different forms of immunotherapy, which has demonstrated clinical benefit in numerous studies, although the overall percentage of patients with durable clinical responses remains limited. This is attributed to the heterogeneity of the disease, the inclusion of late-stage patients with no other treatment options and advanced tumor-associated immunosuppression, which may be consolidated by certain types of chemotherapy. Despite variable responsiveness to distinct types of immunotherapy, therapeutic cancer vaccination has shown meaningful efficacy for a variety of cancers. A key step during cancer vaccination involves the appropriate modeling of the functional state of dendritic cells (DCs) capable of co-delivering four critical signals for proper instruction of tumor antigen-specific T cells. However, the education of DCs, either directly in situ, or ex vivo by various complex procedures, lacks standardization. Also, it is questioned whether ex vivo-prepared DC vaccines are superior to in situ-administered adjuvant-guided vaccines, although both approaches have shown success. Evaluation of these variables is further complicated by a lack of consensus in evaluating vaccination clinical study end points. We discuss the role of signals needed for the preparation of classic in situ and modern ex vivo DC vaccines capable of proper reprogramming of antitumor immune responses in patients with cancer.

Recent progress towards development of a Shigella vaccine

The burden of dysentery due to shigellosis among children in the developing world is still a major concern. A safe and efficacious vaccine against this disease is a priority, since no licensed vaccine is available. This review provides an update of vaccine achievements focusing on subunit vaccine strategies and the forthcoming strategies surrounding this approach. In particular, this review explores several aspects of the pathogenesis of shigellosis and the elicited immune response as being the basis of vaccine requirements. The use of appropriate Shigella antigens, together with the right adjuvants, may offer safety, efficacy and more convenient delivery methods for massive worldwide vaccination campaigns.

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.

New perspectives into bacterial DNA transfer to human cells

The type IV secretion system (T4SS) VirB/D4 of the facultative intracellular pathogen Bartonella henselae is known to translocate bacterial effector proteins into human cells. Two recent reports on DNA transfer into human cells have demonstrated the versatility of this bacterial secretion system for macromolecular substrate transfer. Moreover, these findings have opened the possibility for developing new tools for DNA delivery into specific human cell types. DNA can be introduced into these cells covalently attached to a site-specific integrase with potential target sequences in the human genome. This novel DNA delivery system is discussed in the context of existing methods for genetic modification of human cells.