Construction of bacterial ghosts for transfer and expression of a chimeric hepatitis C virus gene in macrophages

Bacteria-mediated cancer therapy: A versatile bio-sapper with translational potential

Bacteria are important symbionts for humans, which sustain substantial influences on our health. Interestingly, some bastrains have been identified to have therapeutic applications, notably for antitumor activity. Thereby, oncologists have developed various therapeutic models and investigated the potential antitumor mechanisms for bacteria-mediated cancer therapy (BCT). Even though BCT has a long history and exhibits remarkable therapeutic efficacy in pre-clinical animal models, its clinical translation still lags and requires further breakthroughs. This review aims to focus on the established strains of therapeutic bacteria and their antitumor mechanisms, including the stimulation of host immune responses, direct cytotoxicity, the interference on cellular signal transduction, extracellular matrix remodeling, neoangiogenesis, and metabolism, as well as vehicles for drug delivery and gene therapy. Moreover, a brief discussion is proposed regarding the important future directions for this fantastic research field of BCT at the end of this review.

Bacterial navigation for tumor targeting and photothermally-triggered bacterial ghost transformation for spatiotemporal drug release

Cancer chemotherapy is confronted with challenges regarding the effective delivery of chemotherapeutics into tumor cells after systemic administration. Herein, we propose a strategy to load drugs into probiotic E. coli Nissle 1917 (EcN) for self-guided navigation to tumor tissues and subsequently release the drugs with in situ transformation into bacterial ghosts (BGs). Chemotherapeutic agent 5-fluorouracil (FU) and macrophage phenotype regulator zoledronic acid (ZOL) are loaded into EcN through electroporation, followed by decoration of Au nanorods on the ECN surface to construct EcN_Z/F@Au. High loading levels of 5FU (8.8%) and ZOL (10.5%) are achieved as well as high retention rates of bacterial viability (87%) and motion velocity (88%). Under near infrared (NIR) illumination the photothermal effect of Au nanorods elevates the local temperature to induce the transformation of live EcN into BGs. The created transmembrane channels initiate the gradual drug release from BGs, thus representing the first attempt to control the drug release via a biological evolution. An intermittent NIR illumination causes stepwise increases in the BG formation and drug release, which could implement an external on-off control and spatiotemporal drug release. Self-guided motion of EcN promotes efficient extravasation across blood vessels and preferential accumulation of drugs in tumors. In addition to the chemotherapeutic effect of FU, the local release of ZOL from EcN_Z/F@Au enhances valid polarization of tumor-associated macrophages toward the M1 phenotype and an effective production of proinflammatory cytokines, leading to a synergistic efficacy on tumor growth inhibition. Thus, this study demonstrates a feasible strategy to integrate chemotherapy, immunotherapy, and photothermal effects in a concise manner for effective cancer treatment with few side effects. STATEMENT OF SIGNIFICANCE: Bacteria are capable to trace and colonize in hypoxic tumor tissues. Bacterial drug carriers indicate limitations in efficient drug loading and effective release modulation. Herein, we propose a strategy to load drugs into bacteria for self-guided delivery and subsequently release the drugs in tumors with in situ transformation into bacterial ghost (BGs). Drugs are loaded into live bacteria through electroporation and Au nanorods are decorated on the bacterial surface, wherein the photothermal effect, chemotherapy, and immunotherapy are integrated in a concise manner. NIR illmumination of Au nanorods elevates the local temparature, induces the BG tranformation, and activates the spatiotemporal drug release, representing the first attempt of release modulation via a biological evolution.

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.

Design and immune characterization of a novel Neisseria gonorrhoeae DNA vaccine using bacterial ghosts as vector and adjuvant

Gonorrhea, an important sexually transmitted disease, is becoming a growing public health problem around the globe. Vaccination is considered the best long-term approach for control of infection. In this study, we designed a novel Neisseria gonorrhoeae (N. gonorrhoeae) DNA vaccine delivered by bacterial ghosts and characterized its immune responses in vitro and in vivo. Our results demonstrate that bacterial ghosts greatly promoted BMDCs maturation and activation. Bacterial ghosts loaded with N. gonorrhoeae DNA vaccine were efficiently taken up by mouse macrophage RAW264.7 cells. Furthermore, oral immunization with the ghost vaccine candidate elicited greater CD4⁺ and CD8⁺ T cell responses and induced higher IgG responses than N. gonorrhoeae DNA vaccine alone. In addition, mice immunized with the vaccine candidate responded with a significant rise in bactericidal antibody titer. These results suggest that bacterial ghosts may function as a vaccine adjuvant by promoting BMDCs maturation, which in turn enhances the immune responses to the vaccine antigens. This study also highlights the potential of using bacterial ghosts as antigen delivery system in the development of an efficacious gonorrhea vaccine.