Poly-functional and long-lasting anticancer immune response elicited by a safe attenuated Pseudomonas aeruginosa vector for antigens delivery

Therapeutic potential of Pseudomonas aeruginosa-mannose sensitive hemagglutinin (PA-MSHA) in cancer treatment

Pseudomonas aeruginosa is a Gram-negative bacteria and it has been demonstrated that immunization with the outer membrane proteins of the microbe produces most of the relevant human antibodies. The peritrichous P. aeruginosa strain with MSHA fimbriae (PA-MSHA strain) has been found to be effective in the inhibition of growth and proliferation of different types of cancer cells. Furthermore, it has been revealed that PA-MSHA exhibits cytotoxicity because of the presence of MSHA and therefore it possesses anti-carcinogenic ability against different types of human cancer cell lines including, gastric, breast, hepatocarcinoma and nasopharyngeal cells. Studies have revealed that PA-MSHA exhibits therapeutic potential against cancer growth by induction of apoptosis, arrest of cell cycle, activating NF-κB/TLR5 pathway, etc. In China, PA-MSHA injections have been approved for the treatment of malignant tumor patients from very long back. The present review article demonstrates the therapeutic potential of PA-MSHA against various types of human cancers and explains the underlying mechanism.

Engineering a dual vaccine against COVID-19 and tuberculosis

The COVID-19 pandemic, caused by SARS-CoV-2 virus, has been one of the top public health threats across the world over the past three years. Mycobacterium bovis BCG is currently the only licensed vaccine for tuberculosis, one of the deadliest infectious diseases in the world, that is caused by Mycobacterium tuberculosis. In the past decades, recombinant M.bovis BCG has been studied as a novel vaccine vector for other infectious diseases in humans besides tuberculosis, such as viral infections. In the current study, we generated a recombinant M. bovis BCG strain AspikeRBD that expresses a fusion protein consisting of M. tb Ag85A protein and the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein using synthetic biology technique. Our results show that the recombinant M. bovis BCG strain successfully expressed this fusion protein. Interestingly, the recombinant M. bovis BCG strain AspikeRBD significantly induced SARS-CoV-2 spike-specific T cell activation and IgG production in mice when compared to the parental M.bovis BCG strain, and was more potent than the recombinant M.bovis BCG strain expressing SARS-CoV-2 spike RBD alone. As expected, the recombinant M. bovis BCG strain AspikeRBD activated an increased number of M. tb Ag85A-specific IFNγ-releasing T cells and enhanced IgG production in mice when compared to the parental M.bovis BCG strain or the BCG strain expressing SARS-CoV-2 spike RBD alone. Taken together, our results indicate a potential application of the recombinant M. bovis BCG strain AspikeRBD as a novel dual vaccine against SARS-CoV-2 and M. tb in humans.

Pseudomonas aeruginosa in Cancer Therapy: Current Knowledge, Challenges and Future Perspectives

Drug resistance, undesirable toxicity and lack of selectivity are the major challenges of conventional cancer therapies, which cause poor clinical outcomes and high mortality in many cancer patients. Development of alternative cancer therapeutics are highly required for the patients who are resistant to the conventional cancer therapies, including radiotherapy and chemotherapy. The success of a new cancer therapy depends on its high specificity to cancer cells and low toxicity to normal cells. Utilization of bacteria has emerged as a promising strategy for cancer treatment. Attenuated or genetically modified bacteria were used to inhibit tumor growth, modulate host immunity, or deliver anti-tumor agents. The bacteria-derived immunotoxins were capable of destructing tumors with high specificity. These bacteria-based strategies for cancer treatment have shown potent anti-tumor effects both in vivo and in vitro, and some of them have proceeded to clinical trials. Pseudomonas aeruginosa, a Gram-negative bacterial pathogen, is one of the common bacteria used in development of bacteria-based cancer therapy, particularly known for the Pseudomonas exotoxin A-based immunotoxins, which have shown remarkable anti-tumor efficacy and specificity. This review concisely summarizes the current knowledge regarding the utilization of P. aeruginosa in cancer treatment, and discusses the challenges and future perspectives of the P. aeruginosa-based therapeutic strategies.

In Situ Tumor Vaccination with Nanoparticle Co-Delivering CpG and STAT3 siRNA to Effectively Induce Whole-Body Antitumor Immune Response

The success of immunotherapy with immune checkpoint inhibitors (ICIs) in a subset of individuals has been very exciting. However, in many cancers, responses to current ICIs are modest and are seen only in a small subsets of patients. Herein, a widely applicable approach that increases the benefit of ICIs is reported. Intratumoral administration of augmenting immune response and inhibiting suppressive environment of tumors-AIRISE-02 nanotherapeutic that co-delivers CpG and STAT3 siRNA-results in not only regression of the injected tumor, but also tumors at distant sites in multiple tumor model systems. In particular, three doses of AIRISE-02 in combination with systemic ICIs completely cure both treated and untreated aggressive melanoma tumors in 63% of mice, while ICIs alone do not cure any mice. A long-term memory immune effect is also reported. AIRISE-02 is effective in breast and colon tumor models as well. Lastly, AIRISE-02 is well tolerated in mice and nonhuman primates. This approach combines multiple therapeutic agents into a single nanoconstruct to create whole-body immune responses across multiple cancer types. Being a local therapeutic, AIRISE-02 circumvents regulatory challenges of systemic nanoparticle delivery, facilitating rapid translation to the clinic. AIRISE-02 is under investigational new drug (IND)-enabling studies, and clinical trials will soon follow.

Edible Oxya chinensis sinuosa-Derived Protein as a Potential Nutraceutical for Anticancer Immunity Improvement

Oxya chinensis sinuosa (Ocs) is consumed as representative edible insects in Asia, but its function in various immune systems remains unclear. This study aimed to demonstrate the immunomodulatory effect, particularly on the innate and adaptive immune response, of Ocs protein (Ocs-P) and to investigate its function as a potent anticancer immunostimulant when administered during the progression stage of colon carcinoma in tumor-bearing mice. Our in vitro results demonstrated that Ocs-P treatment induces phenotypic alteration (increased expression of surface molecules and production of Th1-polarizing cytokines and decreased antigen uptake ability) of dendritic cells (DCs) through the activation of MAPK and NF-κB-dependent signaling pathways. Additionally, Ocs-P-stimulated DCs initiated differentiation of naive T cells into IFN-γ-producing Th1-type T cells effectively and activated cytotoxic CD8⁺ T cell response. In colon carcinoma-bearing mouse models, oral administration of Ocs-P inhibited tumor growth and restored the expression of decreased surface molecules in lineage^-CD11c⁺MHC-II⁺ splenic DCs. Furthermore, Ocs-P administration enhanced the generation of multifunctional CD4⁺ and CD8⁺ T cells expressing Th1-type cytokines (TNF-α, IFN-γ, and IL-2) and the degranulation marker (CD107a). Collectively, these results suggest that Ocs-P demonstrates an immunostimulatory effect and may induce powerful anticancer immunity.

Mechanistic research holds promise for bacterial vaccines and phage therapies for Pseudomonas aeruginosa

Vaccines for Pseudomonas aeruginosa have been of longstanding interest to immunologists, bacteriologists, and clinicians, due to the widespread prevalence of hospital-acquired infection. As P. aeruginosa becomes increasingly antibiotic resistant, there is a dire need for novel treatments and preventive vaccines. Despite intense efforts, there currently remains no vaccine on the market to combat this dangerous pathogen. This article summarizes current and past vaccines under development that target various constituents of P. aeruginosa. Targeting lipopolysaccharides and O-antigens have shown some promise in preventing infection. Recombinant flagella and pili that target TLR5 have been utilized to combat P. aeruginosa by blocking its motility and adhesion. The type 3 secretion system components, such as needle-like structure PcrV or exotoxin PopB, are also potential vaccine targets. Outer membrane proteins including OprF and OprI are newer representatives of vaccine candidates. Live attenuated vaccines are a focal point in this review, and are also considered for novel vaccines. In addition, phage therapy is revived as an effective option for treating refractory infections after failure with antibiotic treatment. Many of the aforementioned vaccines act on a single target, thus lacking a broad range of protection. Recent studies have shown that mixtures of vaccines and combination approaches may significantly augment immunogenicity, thereby increasing their preventive and therapeutic potential.

Live-Attenuated Bacterial Vectors for Delivery of Mucosal Vaccines, DNA Vaccines, and Cancer Immunotherapy

Vaccines save millions of lives each year from various life-threatening infectious diseases, and there are more than 20 vaccines currently licensed for human use worldwide. Moreover, in recent decades immunotherapy has become the mainstream therapy, which highlights the tremendous potential of immune response mediators, including vaccines for prevention and treatment of various forms of cancer. However, despite the tremendous advances in microbiology and immunology, there are several vaccine preventable diseases which still lack effective vaccines. Classically, weakened forms (attenuated) of pathogenic microbes were used as vaccines. Although the attenuated microbes induce effective immune response, a significant risk of reversion to pathogenic forms remains. While in the twenty-first century, with the advent of genetic engineering, microbes can be tailored with desired properties.

In this review, I have focused on the use of genetically modified bacteria for the delivery of vaccine antigens. More specifically, the live-attenuated bacteria, derived from pathogenic bacteria, possess many features that make them highly suitable vectors for the delivery of vaccine antigens. Bacteria can theoretically express any heterologous gene or can deliver mammalian expression vectors harboring vaccine antigens (DNA vaccines). These properties of live-attenuated microbes are being harnessed to make vaccines against several infectious and noninfectious diseases. In this regard, I have described the desired features of live-attenuated bacterial vectors and the mechanisms of immune responses manifested by live-attenuated bacterial vectors. Interestingly anaerobic bacteria are naturally attracted to tumors, which make them suitable vehicles to deliver tumor-associated antigens thus I have discussed important studies investigating the role of bacterial vectors in immunotherapy. Finally, I have provided important discussion on novel approaches for improvement and tailoring of live-attenuated bacterial vectors for the generation of desired immune responses.

Enhanced differentiation of human pluripotent stem cells into cardiomyocytes by bacteria-mediated transcription factors delivery

Virus-mediated expression of defined transcription factor (TF) genes can effectively induce cellular reprogramming. However, sustained expression of the TFs often hinders pluripotent stem cell (PSC) differentiation into specific cell types, as each TF exerts its effect on PSCs for a defined period of time during differentiation. Here, we applied a bacterial type III secretion system (T3SS)-based protein delivery tool to directly translocate TFs in the form of protein into human PSCs. This transient protein delivery technique showed high delivery efficiency for hPSCs, and it avoids potential genetic alterations caused by the introduction of transgenes. In an established cardiomyocyte de novo differentiation procedure, five transcriptional factors, namely GATA4, MEF2C, TBX5, ESRRG and MESP1 (abbreviated as GMTEM), were translocated at various time points. By detecting the expression of cardiac marker genes (Nkx2.5 and cTnT), we found that GMTEM proteins delivered on mesoderm stage of the cardiomyocytes lineage differentiation significantly enhanced both the human ESC and iPSC differentiation into cardiomyocytes, while earlier or later delivery diminished the enhancing effect. Furthermore, all of the five factors were required to enhance the cardiac differentiation. This work provides a virus-free strategy of transient transcription factors delivery for directing human stem cell fate without jeopardizing genome integrity, thus safe for biomedical applications.

Live bacterial vaccine vector and delivery strategies of heterologous antigen: A review

Live bacteria, including attenuated bacteria and probiotics, can be engineered to deliver target antigen to excite the host immune system. The preponderance of these live bacterial vaccine vectors is that they can stimulate durable humoral and cellular immunity. Moreover, delivery strategies of heterologous antigen in live bacterial promote the applications of new vaccine development. Genetic technologies are evolving, which potentiate the developing of heterologous antigen delivery systems, including bacterial surface display system, bacterial secretion system and balanced lethal vector system. Although the live bacterial vaccine vector is a powerful adjuvant, certain disadvantages, such as safety risk, must also be taken into account. In this review, we compare the development of representative live bacterial vectors, and summarize the main characterizations of the various delivery strategies of heterologous antigen in live vector vaccines.

Killed but metabolically active Pseudomonas aeruginosa-based vaccine induces protective humoral- and cell-mediated immunity against Pseudomonas aeruginosa pulmonary infections

Pseudomonas aeruginosa (Pa) is a significant cause of morbidity and mortality, especially in cystic fibrosis patients. Its eradication is difficult due to a wide phenotypic adaptability and an increase of its resistance to antibiotics. After the failure of several recombinant vaccines which mainly triggered humoral response, live-attenuated vaccines received attention thanks to their ability to elicit a broad immunity with both humoral- and cell-mediated responses, essential to fight this pathogen. In this study, we developed an innovative and safer live-attenuated Pa vaccine based on a Killed But Metabolically Active (KBMA) attenuation method. KBMA Pa has been further rationally designed to overexpress beneficial effectors like the type 3 secretion system apparatus. We demonstrated that KBMA Pa elicits a high and broad humoral response in mice against several antigens of particular interest such as OprF and PcrV proteins. Moreover, we assessed cytokines in the serum of immunized mice and showed that KBMA Pa elicits Th1, Th2 and especially Th17 pathways of cell-mediated immune responses. Th17 pathway involvement was also confirmed after specific stimulation of helper T cells in immunized mice. Finally, we showed that this vaccine is safe and has a protective effect in a murine acute pulmonary infectious challenge. In conclusion, KBMA Pa is a new platform with high potential for the development of a vaccine against Pa.

Bacterial type III secretion system as a protein delivery tool for a broad range of biomedical applications

A protein delivery tool based on bacterial type III secretion system (T3SS) has been broadly applied in biomedical researches. In this review, we summarize various applications of the T3SS-mediate protein delivery which enables translocation of proteins directly into mammalian cells without protein purification. Some of the remarkable advancements include delivery of antigens for therapeutic vaccines, nucleases for genome editing, transcription factors for cellular reprogramming and stem cells differentiation, and signaling molecules for post-translational proteomics studies. With continued improvement of the T3SS-mediated protein delivery tools, even wider application of the technology is anticipated.

Rationale redesign of type III secretion systems: toward the development of non-pathogenic E. coli for in vivo delivery of therapeutic payloads

Transkingdom secretion systems that bacteria use to inject proteins directly into the cytosol of mammalian host cells play an essential role in the virulence of many Gram-negative bacterial pathogens. Current efforts are underway to repurpose these machines as novel therapeutics; type III secretion systems as vectors for the delivery of proteins of therapeutic value including heterologous antigens for vaccine development and type IV secretion systems as vectors for DNA. While initial studies focused on the use of attenuated or replication incompetent pathogens, the recent development of non-pathogenic Escherichia coli that encode programmable type III secretion systems expands possibilities for the in vivo directed delivery of therapeutic payloads.