Recombinant Mycobacterium bovis BCG expressing pertussis toxin subunit S1 induces protection against an intracerebral challenge with live Bordetella pertussis in mice

BCG therapy in bladder cancer and its tumor microenvironment interactions

SUMMARYBacillus Calmette-Guérin (BCG) has been the standard treatment for non-muscle-invasive bladder cancer for over 30 years. Despite its proven efficacy, challenges persist, including unclear mechanisms of action, resistance in 30%-50% of patients, and significant side effects. This review presents an updated and balanced discussion of the antitumor mechanisms of BCG, focusing on its direct effects on bladder cancer and its interactions with various cell types within the bladder tumor microenvironment. Notably, recent research on the interactions between BCG and the bladder microbiome is also incorporated. We further summarize and analyze the latest preclinical and clinical studies regarding both intrinsic and adaptive resistance to BCG in bladder cancer. Based on the current understanding of BCG's therapeutic principles and resistance mechanisms, we systematically explore strategies to improve BCG-based tumor immunotherapy. These include the development of recombinant BCG, combination therapy with different drugs, optimization of therapeutic regimens and management, and the exploration of new approaches by targeting changes in the bladder microbiota and its metabolites. These measures aim to effectively address the BCG resistance in bladder cancer, reduce its toxicity, and ultimately enhance the clinical anti-tumor efficacy. Bacterial therapy, represented by genetically engineered oncolytic bacteria, has gradually emerged in the field of cancer treatment in recent years. As the only bacterial drug successfully approved for oncology use, BCG has provided decades of clinical experience. By consolidating lessons from BCG's successes and limitations, we hope to provide valuable insights for the development and application of bacterial therapies in cancer treatment.

Exploring BCG to deliver avidin fusion antigens from Schistosoma mansoni

BACKGROUND

Bacillus Calmette-Guérin (BCG) is one of the most successful vaccines in the world and evidence suggests it can be used as a bacterial vector to deliver heterologous antigens.

OBJECTIVES

We evaluated whether BCG could be biotinylated and used as a carrier of Schistosoma mansoni antigen tetraspanin-2 (TSP-2) fused with rhizavidin, an avidin analog.

METHODS

BCG was grown and biotinylated. The recombinant protein Rzv:TSP-2 was produced and purified from Escherichia coli. The biotinylation and antigen coupling was analysed by flow cytometry, enzyme-linked immunosorbent assay (ELISA) and Western blot. Vaccine immunogenicity was tested in immunised mice by the assessment of lung and splenic T cells.

FINDINGS

BCG can be biotinylated, which in turn, can be coupled with Rzv:TSP-2. After a series of optimisations which involved molarity of the biotin, ratio of BCG:reagent and the concentration of Rzv:TSP-2 used, almost 50% of the bacteria were biotinylated and 35% coupled with antigen. Although a clear adjuvant effect of BCG was observed, evaluation of immune response in immunised mice demonstrated an overall low immunogenicity of the BCG-Rzv:TSP-2.

MAIN CONCLUSION

These results demonstrated the use of BCG as a carrier of avidin-tagged antigens. Further optimisations are needed in order to strengthen the stability of tagged proteins in order to produce antigen-specific immune responses.

Comparison Between Simple Batch and Fed-Batch Bioreactor Cultivation of Recombinant BCG

Background/Objectives: Tuberculosis continues to be a significant global health concern, causing 1.3 million deaths in 2022, particularly affecting children under 5 years old. The Bacillus Calmette-Guérin (BCG) vaccine, developed in 1921, remains the primary defense against tuberculosis but requires modernized production methods. The recombinant BCG-pertussis strain shows potential in providing dual protection against tuberculosis and whooping cough, especially for vulnerable newborns, and enhanced efficacy against bladder cancer. Implementing submerged cultivation techniques for rBCG-pertussis production can offer increased productivity and standardization. Methods: This study explores a fed-batch cultivation strategy with pH-stat control to feed L-glutamic acid through the acid pump into 1 L bioreactor. Three pH values were evaluated for fed-batch and a simple batch without pH control was done for comparison. The viable cell concentration was compared before and after freeze-drying samples harvested during the cultures. Results: L-glutamic acid was identified as the preferred substrate for rBCG-pertussis. While the fed-batch strategy did not enhance the maximum specific growth rate compared to simple batch cultivation, it did improve the specific growth rate after day 4 in the pH 7.4-controlled fed-batch cultures, thereby reducing the cultivation time. Fed-batch cultures controlled at three pH levels exhibited lower optical density than the simple batch, although the viable cell counts were similar. Notably, samples harvested after day 8 from the simple batch cultures showed a reduction in CFU/mL after freeze-drying, whereas all fed-batch samples exhibited high recovery of viable cell counts post lyophilization. Conclusions: The additional glutamate supplied to the fed-batch cultures may have protected the cells during the lyophilization process.

Current Understanding of Bacillus Calmette-Guérin-Mediated Trained Immunity and Its Perspectives for Controlling Intracellular Infections

The bacillus Calmette-Guérin (BCG) is an attenuated bacterium derived from virulent Mycobacterium bovis. It is the only licensed vaccine used for preventing severe forms of tuberculosis in children. Besides its specific effects against tuberculosis, BCG administration is also associated with beneficial non-specific effects (NSEs) following heterologous stimuli in humans and mice. The NSEs from BCG could be related to both adaptive and innate immune responses. The latter is also known as trained immunity (TI), a recently described biological feature of innate cells that enables functional improvement based on metabolic and epigenetic reprogramming. Currently, the mechanisms related to BCG-mediated TI are the focus of intense research, but many gaps are still in need of elucidation. This review discusses the present understanding of TI induced by BCG, exploring signaling pathways that are crucial to a trained phenotype in hematopoietic stem cells and monocytes/macrophages lineage. It focuses on BCG-mediated TI mechanisms, including the metabolic-epigenetic axis and the inflammasome pathway in these cells against intracellular pathogens. Moreover, this study explores the TI in different immune cell types, its ability to protect against various intracellular infections, and the integration of trained innate memory with adaptive memory to shape next-generation vaccines.

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.

Recombinant BCG to Enhance Its Immunomodulatory Activities

The bacillus Calmette-Guérin (BCG) is an attenuated Mycobacterium bovis derivative that has been widely used as a live vaccine against tuberculosis for a century. In addition to its use as a tuberculosis vaccine, BCG has also been found to have utility in the prevention or treatment of unrelated diseases, including cancer. However, the protective and therapeutic efficacy of BCG against tuberculosis and other diseases is not perfect. For three decades, it has been possible to genetically modify BCG in an attempt to improve its efficacy. Various immune-modulatory molecules have been produced in recombinant BCG strains and tested for protection against tuberculosis or treatment of several cancers or inflammatory diseases. These molecules include cytokines, bacterial toxins or toxin fragments, as well as other protein and non-protein immune-modulatory molecules. The deletion of genes responsible for the immune-suppressive properties of BCG has also been explored for their effect on BCG-induced innate and adaptive immune responses. Most studies limited their investigations to the description of T cell immune responses that were modified by the genetic modifications of BCG. Some studies also reported improved protection by recombinant BCG against tuberculosis or enhanced therapeutic efficacy against various cancer forms or allergies. However, so far, these investigations have been limited to mouse models, and the prophylactic or therapeutic potential of recombinant BCG strains has not yet been illustrated in other species, including humans, with the exception of a genetically modified BCG strain that is now in late-stage clinical development as a vaccine against tuberculosis. In this review, we provide an overview of the different molecular engineering strategies adopted over the last three decades in order to enhance the immune-modulatory potential of BCG.

Auxotrophic Mycobacterium bovis BCG: Updates and Perspectives

Mycobacterium bovis BCG has been used for a century as the only licensed vaccine against tuberculosis. Owing to its strong adjuvant properties, BCG has also been employed as an oncological immunotherapeutic as well as a live vaccine vector against other pathogens. However, BCG vaccination has limited efficacy in protecting against adult forms of tuberculosis (TB), raises concerns about its safety in immunocompromised populations, compromises the diagnosis of TB through the tuberculin test and lacks predictability for successful antigen expression and immune responses to heterologous antigens. Together, these factors propelled the construction and evaluation of auxotrophic BCG strains. Auxotrophs of BCG have been developed from mutations in the genes required for their growth using different approaches and have shown the potential to provide a model to study M. tuberculosis, a more stable, safe, and effective alternative to BCG and a vector for the development of recombinant live vaccines, especially against HIV infection. In this review, we provide an overview of the strategies for developing and using the auxotrophic BCG strains in different scenarios.

Recombinant BCG Expressing the Subunit 1 of Pertussis Toxin Induces Innate Immune Memory and Confers Protection against Non-Related Pathogens

BCG has shown the ability to induce protection against unrelated pathogens, which likely depends on an immune mechanism known as innate immune memory or trained immunity. In this study, we evaluated the induction of innate memory by a recombinant BCG strain expressing the genetically detoxified S1 subunit of the pertussis toxin (rBCG-S1PT). In vitro pre-exposure of naïve murine macrophages to rBCG-S1PT increased their innate/inflammatory response (IL-6, TNF-α, and IL-10) to a subsequent challenge with unrelated pathogens, as compared to pre-exposure to wild-type BCG. Following LPS challenge, mice immunized with rBCG-S1PT produced higher levels of IFN-γ, while the release of other inflammatory cytokines was comparable to that measured after BCG immunization. SCID mice previously immunized with rBCG-S1PT and challenged with pathogenic Candida albicans displayed a similar survival curve as BCG-immunized mice but a lower CFU burden in the kidneys, suggesting an innate memory-dependent control of C. albicans infection. This study highlights the potential of recombinant BCG to increase innate immune memory and, ultimately, non-specific protection, more effectively than wild-type BCG. To our knowledge, this is the first report describing the potential of a recombinant BCG strain to strengthen innate immune memory responses.

Engineering a new vaccine platform for heterologous antigen delivery in live-attenuated Mycobacterium tuberculosis

Live vaccines are attractive vehicles for antigen delivery as a strategy to immunize against heterologous pathogens. The live vaccine MTBVAC is based on rational attenuation of Mycobacterium tuberculosis with the objective of improving BCG protection against pulmonary tuberculosis. However, the development of recombinant mycobacteria as antigen-presenting microorganisms has been hindered due to their fastidious genetic manipulation. In this study, we used MTBVAC as a genetic platform to deliver diphtheria, tetanus, or pertussis toxoids, which are the immunogenic constituents of the DTP vaccine. When using nonoptimal genetic conditions, the expression of these immunogens was barely detectable. Accordingly, we pursued a rational, step-by-step optimization of the genetic components to achieve the expression and secretion of these toxoids. We explored variants of the L5 mycobacteriophage promoter to ensure balanced antigen expression and plasmid stability. Optimal signal sequences were identified by comparative proteomics of MTBVAC and its parental strain. It was determined that proteins secreted by the Twin Arginine Translocation pathway displayed higher secretion in MTBVAC, and the Ag85A secretion sequence was selected as the best candidate. Because the coding regions of diphtheria, tetanus, and pertussis toxoids significantly differ in G + C content relative to mycobacterial genes, their codon usage was optimized. We also placed a 3xFLAG epitope in frame with the C-terminus of these toxoids to facilitate protein detection. Altogether, these optimizations resulted in the secretion of DTP antigens by MTBVAC, as demonstrated by western blot and MRM-MS. Finally, we examined specific antibody responses in mice vaccinated with recombinant MTBVAC expressing DTP antigens.

SARS-CoV-2 vaccine development and how Brazil is contributing

The SARS-CoV-2 coronavirus pandemic calls for coordinated efforts by the scientific community for the development of vaccines. The most advanced strategies have focused on modifications of technologies that were already under development for other viruses, such as SARS, MERS, and even Influenza. Classic and new technologies, such as inactivated and attenuated viruses (non-replicative and replicative), DNA and mRNA vaccines, and nanoparticles containing SARS-CoV-2 antigens, are some of the strategies currently investigated. Although there is a very high expectation for the effectiveness of the most advanced vaccine candidates, there are still no established correlates of protection. Previous experience in vaccine development for other pathogens shows that differences in vaccine formulation can result in diverse immune responses and consequently, different protective properties. Therefore the importance of continuing investigations on a broad range of strategies. Expertise in vaccine development in Brazil was refocused to the new coronavirus. Impressive collaboration between institutions will support further developments until we have available a safe, effective, and economically viable vaccine. Established competence and collaborations will allow preparedness for future challenges and can also be used to address local issues as neglected infectious diseases.

BCG vaccination improves DTaP immune responses in mice and is associated with lower pertussis incidence in ecological epidemiological studies

BACKGROUND

The Bacillus Calmette-Guérin (BCG), the only vaccine against tuberculosis (TB) currently in use, has shown beneficial effects against unrelated infections and to enhance immune responses to vaccines. However, there is little evidence regarding the influence of BCG vaccination on pertussis.

METHODS

Here, we studied the ability of BCG to improve the immune responses to diphtheria, tetanus, and acellular (DTaP) or whole-cell pertussis (DTwP) vaccination in a mouse model. We included MTBVAC, an experimental live-attenuated vaccine derived from Mycobacterium tuberculosis, in our studies to explore if it presents similar heterologous immunity as BCG. Furthermore, we explored the potential effect of routine BCG vaccination on pertussis incidence worldwide.

FINDINGS

We found that both BCG and MTBVAC when administered before DTaP, triggered Th1 immune responses against diphtheria, tetanus, and pertussis in mice. Immunization with DTaP alone failed to trigger a Th1 response, as measured by the production of IFN-γ. Humoral responses against DTaP antigens were also enhanced by previous immunization with BCG or MTBVAC. Furthermore, exploration of human epidemiological data showed that pertussis incidence was 10-fold lower in countries that use DTaP and BCG compared to countries that use only DTaP.

INTERPRETATION

BCG vaccination may have a beneficial impact on the protection against pertussis conferred by DTaP. Further randomized controlled trials are needed to properly define the impact of BCG on pertussis incidence in a controlled setting. This could be a major finding that would support changes in immunization policies.

FUNDING

This work was supported by the Ministry of "Economía y Competitividad"; European Commission H2020 program, "Gobierno de Aragón"; CIBERES; "Fundação Butantan"; Instituto de Salud Carlos III and "Fondo FEDER".

Vaccines for COVID-19: perspectives from nucleic acid vaccines to BCG as delivery vector system

This article discusses standard and new disruptive strategies in the race to develop an anti-COVID-19 vaccine. We also included new bioinformatic data from our group mapping immunodominant epitopes and structural analysis of the spike protein. Another innovative approach reviewed here is the use of BCG vaccine as priming strategy and/or delivery system expressing SARS-CoV-2 antigens.

Characterisation of alternative expression vectors for recombinant Bacillus Calmette-Guérin as live bacterial delivery systems

BACKGROUND

Bacillus Calmette-Guérin (BCG) is considered a promising live bacterial delivery system. However, several proposals for rBCG vaccines have not progressed, mainly due to the limitations of the available expression systems.

OBJECTIVES

To obtain a set of mycobacterial vectors using a range of promoters with different strengths based on a standard backbone, previously shown to be stable.

METHODS

Mycobacterial expression vectors based on the pLA71 vector as backbone, were obtained inserting different promoters (P_AN, P_αAg, P_Hsp60, P_BlaF* and P_L5) and the green fluorescence protein (GFP) as reporter gene, to evaluate features such as their relative strengths, and the in vitro (inside macrophages) and in vivo stability.

FINDINGS

The relative fluorescence observed with the different vectors showed increasing strength of the promoters: P_AN was the weakest in both Mycobacterium smegmatis and BCG and P_BlaF* was higher than P_Hsp60 in BCG. The relative fluorescence observed in a macrophage cell line showed that P_BlaF* and P_Hsp60 were comparable. It was not possible to obtain strains transformed with the extrachromosomal expression vector containing the P_L5 in either species.

MAIN CONCLUSION

We have obtained a set of potentially stable mycobacterial vectors with a arrange of expression levels, to be used in the development of rBCG vaccines.

Recombinant Production of a Novel Fusion Protein: Listeriolysin O Fragment Fused to S1 Subunit of Pertussis Toxin

Background:

Some resources have suggested that genetically inactivated PTs bear a more protective effect than chemically inactivated products. This study aimed to produce new version of PT, by cloning an inactive PTS1 in a fusion form with N-terminal half of the LLO pore-forming toxin.

Methods:

Deposited pdb structure file of the PT was used to model an extra disulfide bond. Codon-optimized ORF of the PTS1 was used to make recombinant constructs of PTS1 and LLO-PTS1 in the pPSG-IBA35 vector. The recombinant PTS1 and LLO-PTS1 proteins were expressed in BL21 DE3 and SHuffle T7 strains of E. coli and purified by affinity chromatography. Cytotoxic effects of the recombinant proteins were examined in the MCF-7 cell line.

Results:

The purity of the products proved to be more than 85%, and the efficiency of the disulfide bond formation in SHuffle T7 strain was higher than BL21 DE3 strain. No cytotoxicity of the recombinant proteins was observed in MCF-7 cells. Soluble recombinant PTS1 and LLO-PTS1 proteins were produced in SHuffle T7 strain of E. coli with high efficiency of disulfide bonds formation.

Conclusion:

The LLO-PTS1 with corrected disulfide bonds was successfully expressed in E. coli SHuffleT7 strain. Due to the safety for human cells, this chimeric molecule can be an option to prevent pertussis disease if its immunostimulatory effects would be confirmed in the future.

Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections

Well-adapted pathogens have evolved to survive the many challenges of a robust immune response. Defending against all host antimicrobials simultaneously would be exceedingly difficult, if not impossible, so many co-evolved organisms utilize immunomodulatory tools to subvert, distract, and/or evade the host immune response. Bordetella spp. present many examples of the diversity of immunomodulators and an exceptional experimental system in which to study them. Recent advances in this experimental system suggest strategies for interventions that tweak immunity to disrupt bacterial immunomodulation, engaging more effective host immunity to better prevent and treat infections. Here we review advances in the understanding of respiratory pathogens, with special focus on Bordetella spp., and prospects for the use of immune-stimulatory interventions in the prevention and treatment of infection.

BCG-Induced Cross-Protection and Development of Trained Immunity: Implication for Vaccine Design

The Bacillus Calmette-Guérin (BCG) is a live attenuated tuberculosis vaccine that has the ability to induce non-specific cross-protection against pathogens that might be unrelated to the target disease. Vaccination with BCG reduces mortality in newborns and induces an improved innate immune response against microorganisms other than Mycobacterium tuberculosis, such as Candida albicans and Staphylococcus aureus. Innate immune cells, including monocytes and natural killer (NK) cells, contribute to this non-specific immune protection in a way that is independent of memory T or B cells. This phenomenon associated with a memory-like response in innate immune cells is known as "trained immunity." Epigenetic reprogramming through histone modification in the regulatory elements of particular genes has been reported as one of the mechanisms associated with the induction of trained immunity in both, humans and mice. Indeed, it has been shown that BCG vaccination induces changes in the methylation pattern of histones associated with specific genes in circulating monocytes leading to a "trained" state. Importantly, these modifications can lead to the expression and/or repression of genes that are related to increased protection against secondary infections after vaccination, with improved pathogen recognition and faster inflammatory responses. In this review, we discuss BCG-induced cross-protection and acquisition of trained immunity and potential heterologous effects of recombinant BCG vaccines.

Potential of recombinant Mycobacterium paragordonae expressing HIV-1 Gag as a prime vaccine for HIV-1 infection

Recombinant Mycobacterium strains such as recombinant BCG (rBCG) have received considerable attention for the HIV-1 vaccine development. Recently, we described a temperature-sensitive Mycobacterium paragordonae (Mpg) strain as a novel live tuberculosis vaccine that is safer and showed an enhanced protective effect against mycobacterial infection compared to BCG. We studied the possibility of developing a vaccine against HIV-1 infection using rMpg strain expressing the p24 antigen (rMpg-p24). We observed that rMpg-p24 can induce an increased p24 expression in infected antigen presenting cells (APCs) compared to rBCG-p24. We also observed that rMpg-p24 can induce enhanced p24 specific immune responses in vaccinated mice as evidenced by increased p24-specific T lymphocyte proliferation, gamma interferon induction, antibody production and cytotoxic T lymphocyte (CTL) responses. Furthermore, an rMpg-p24 prime and plasmid DNA boost showed an increased CTL response and antibody production compared to rBCG or rMpg alone. In summary, our study indicates that a live rMpg-p24 strain induced enhanced immune responses against HIV-1 Gag in vaccinated mice. Thus, rMpg-p24 may have potential as a preventive prime vaccine in a heterologous prime-boost regimen for HIV-1 infection.

In vitro Evidence of Human Immune Responsiveness Shows the Improved Potential of a Recombinant BCG Strain for Bladder Cancer Treatment

The live attenuated mycobacterial strain BCG, in use as vaccine against tuberculosis, is considered the gold standard for primary therapy of carcinoma in situ of the bladder. Despite its limitations, to date it has not been surpassed by any other treatment. Our group has developed a recombinant BCG strain expressing the detoxified S1 pertussis toxin (rBCG-S1PT) that proved more effective than wild type BCG (WT-BCG) in increasing survival time in an experimental mouse model of bladder cancer, due to the well-known adjuvant properties of pertussis toxin. Here, we investigated the capacity of rBCG-S1PT to stimulate human immune responses, in comparison to WT-BCG, using an in vitro stimulation assay based on human whole blood cells that allows for a comprehensive evaluation of leukocyte activation. Blood leukocytes stimulated with rBCG-S1PT produced increased levels of IL-6, IL-8, and IL-10 as compared to WT-BCG, but comparable levels of IL-1β, IL-2, IFN-γ, and TNF-α. Stimulation of blood cells with the recombinant BCG strain also enhanced the expression of CD25 and CD69 on human CD4+ T cells. PBMC stimulated with rBCG-S1PT induced higher cytotoxicity to MB49 bladder cancer cells than WT-BCG-stimulated PBMC. These results suggest that the rBCG-S1PT strain is able to activate an immune response in human leukocytes that is higher than that induced by WT-BCG for parameters linked to better prognosis in bladder cancer (regulation of immune and early inflammatory responses), while fully comparable to WT-BCG for classical inflammatory parameters. This establishes rBCG-S1PT as a new highly effective candidate as immunotherapeutic agent against bladder cancer.

A Bivalent Recombinant Mycobacterium bovis BCG Expressing the S1 Subunit of the Pertussis Toxin Induces a Polyfunctional CD4+ T Cell Immune Response

Background

A recombinant BCG strain expressing the genetically detoxified S1 subunit of pertussis toxin 9K/129G (rBCG-S1PT), previously constructed by our research group, demonstrated the ability to develop high protection in mouse models of pertussis challenge which correlated with the induction of a Th1 immune response pattern. The Th1 immune response induced by rBCG-S1PT treatment was also confirmed in the murine orthotopic bladder cancer model, in which the intravesical instillation of rBCG-S1PT resulted in an improved antitumor effect. Based on these observations, we hypothesize that the reengineering of the S1PT expression in BCG could increase the efficiency of the protective Th1 immune response in order to develop a new alternative of immunotherapy in bladder cancer treatment.

Objectives

To construct rBCG strains expressing S1PT from extrachromosomal (rBCG-S1PT) and integrative vectors (rBCG-Sli), or their combination, generating the bivalent strain (rBCG-S1+S1i), and to evaluate the respective immunogenicity of rBCG strains in mice.

Methods

Mycobacterial plasmids were constructed by cloning the s1pt gene under integrative and extrachromosomal vectors and used to transform BCG, individually or in combination. Antigen expression and localization were confirmed by Western blot. Mice were immunized with wild-type BCG or the rBCG strains, and cytokines quantification and flow cytometry analysis were performed in splenocytes culture stimulated with mycobacterial-specific proteins.

Findings

S1PT expression was confirmed in all rBCG strains. The extrachromosomal vector directs S1PT to the cell wall-associated fraction, while the integrative vector directs its expression mainly to the intracellular fraction. Higher levels of IFN-γ were observed in the splenocytes culture from the group immunized with rBCG-S1i in comparison to BCG or rBCG-S1PT. rBCG-S1+S1i showed higher levels of CD4⁺ IFN-γ⁺ and double-positive CD4⁺ IFN-γ⁺ TNF-α⁺ T cells.

Conclusions

rBCG-S1+S1i was able to express the two forms of S1PT and elicited higher induction of polyfunctional CD4⁺ T cells, indicating enhanced immunogenicity and suggesting its use as immunotherapy for bladder cancer.

Development of a Live Recombinant BCG Expressing Human Immunodeficiency Virus Type 1 (HIV-1) Gag Using a pMyong2 Vector System: Potential Use As a Novel HIV-1 Vaccine

Even though the rate of new human immunodeficiency virus type 1 (HIV-1) infections is gradually decreasing worldwide, an effective preventive vaccine for HIV-1 is still urgently needed. The recombinant Mycobacterium bovis BCG (rBCG) is promising for the development of an HIV-1 vaccine. Recently, we showed that a recombinant Mycobacterium smegmatis expressing HIV-1 gag in a pMyong2 vector system (rSmeg-pMyong2-p24) increased the efficacy of a vaccine against HIV-1 in mice. Here, we evaluated the potential of an rBCG expressing HIV-1 p24 antigen Gag in pMyong2 (rBCG-pMyong2-p24) in a vaccine application for HIV-1 infection. We found that rBCG-pMyong2-p24 elicited an enhanced HIV-1 p24 Gag expression in rBCG and infected antigen-presenting cells. We also found that compared to rBCG-pAL-p24 in a pAL5000 derived vector system, rBCG-pMyong2-p24 elicited enhanced p24-specific immune responses in vaccinated mice as evidenced by higher levels of HIV-1 Gag-specific CD4 and CD8 T lymphocyte proliferation, gamma interferon ELISPOT cell induction, antibody production, and cytotoxic T lymphocytes (CTL) responses. Furthermore, rBCG-pMyong2-p24 showed a higher level of p24-specific Ab production than rSmeg-pMyong2-p24 in the same pMyong2 vector system. In conclusion, our data indicated that a live recombinant BCG expressing HIV-1 Gag using a pMyong2 vector system, rBCG-pMyong2-p24 elicited an enhanced immune response against HIV-1 infections in a mouse model system. So, rBCG-pMyong2-p24 may have the potential as a prime vaccine in a heterologous prime-boost vaccine strategy for HIV-1 infection.

A Combination of Recombinant Mycobacterium bovis BCG Strains Expressing Pneumococcal Proteins Induces Cellular and Humoral Immune Responses and Protects against Pneumococcal Colonization and Sepsis

Pneumococcal diseases remain a substantial cause of mortality in young children in developing countries. The development of potentially serotype-transcending vaccines has been extensively studied; ideally, such a vaccine should include antigens that are able to induce protection against colonization (likely mediated by interleukin-17A [IL-17A]) and invasive disease (likely mediated by antibody). The use of strong adjuvants or alternative delivery systems that are able to improve the immunological response of recombinant proteins has been proposed but poses potential safety and practical concerns in children. We have previously constructed a recombinant Mycobacterium bovis BCG strain expressing a pneumococcal surface protein A (PspA)-PdT fusion protein (rBCG PspA-PdT) that was able to induce an effective immune response and protection against sepsis in a prime-boost strategy. Here, we constructed two new rBCG strains expressing the pneumococcal proteins SP 0148 and SP 2108, which confer IL-17A-dependent protection against pneumococcal colonization in mouse models. Immunization of mice with rBCG 0148 or rBCG 2108 in a prime-boost strategy induced IL-17A and gamma interferon (IFN-γ) production. The combination of these rBCG strains with rBCG PspA-PdT (rBCG Mix), followed by a booster dose of the combined recombinant proteins (rMix) induced an IL-17A response against SP 0148 and SP 2108 and a humoral response characterized by increased levels of IgG2c against PspA and functional antibodies against pneumolysin. Furthermore, immunization with the rBCG Mix prime/rMix booster (rBCG Mix/rMix) provides protection against pneumococcal colonization and sepsis. These results suggest the use of combined rBCG strains as a potentially serotype-transcending pneumococcal vaccine in a prime-boost strategy, which could provide protection against pneumococcal colonization and sepsis.

Recombinant BCG vaccines: molecular features and their influence in the expression of foreign genes

Recombinant Mycobacterium bovis BCG vaccines (rBCG) were first developed in the 1990s as a means of expressing antigens from multiple pathogens. This review examines the key structural factors of recombinant M. bovis that influence the expression of the heterologous antigens and the generation of genetic and functional stability in rBCG, which are crucial for inducing strong and lasting immune responses. The fundamental aim of this paper is to provide an overview of factors that affect the expression of recombinant proteins in BCG and the generation of the immune response against the target antigens, including mycobacterial promoters, location of foreign antigens, and stability of the vectors. The reporter systems that have been employed for evaluation of these molecular features in BCG are also reviewed here.

Recombinant BCG Expressing LTAK63 Adjuvant induces Superior Protection against Mycobacterium tuberculosis

In order to develop an improved BCG vaccine against tuberculosis we have taken advantage of the adjuvant properties of a non-toxic derivative of Escherichia coli heat labile enterotoxin (LT), LTAK63. We have constructed rBCG strains expressing LTAK63 at different expression levels. Mice immunized with BCG expressing low levels of LTAK63 (rBCG-LTAK63_lo) showed higher Th1 cytokines and IL-17 in the lungs, and when challenged intratracheally with Mycobacterium tuberculosis displayed a 2.0–3.0 log reduction in CFU as compared to wild type BCG. Histopathological analysis of lung tissues from protected mice revealed a reduced inflammatory response. Immunization with rBCG-LTAK63_lo also protected against a 100-fold higher challenge dose. Mice immunized with rBCG-LTAK63_lo produced an increase in TGF-β as compared with BCG after challenge, with a corresponding reduction in Th1 and Th17 cytokines, as determined by Real Time RT-PCR. Furthermore, rBCG-LTAK63_lo also displays protection against challenge with a highly virulent Beijing isolate. Our findings suggest that BCG with low-level expression of the LTAK63 adjuvant induces a stronger immune response in the lungs conferring higher levels of protection, and a novel mechanism subsequently triggers a regulatory immune response, which then limits the pathology. The rBCG-LTAK63_lo strain can be the basis of an improved vaccine against tuberculosis.

Recombinant Mycobacterium smegmatis with a pMyong2 vector expressing Human Immunodeficiency Virus Type I Gag can induce enhanced virus-specific immune responses

Recently, we have developed a novel Mycobacterium-Escherichia coli shuttle vector system using pMyong2, which can provide an enhanced expression of heterologous genes in recombinant Mycobacterium smegmatis (rSmeg). To investigate the usefulness of rSmeg using pMyong2 in vaccine application, we vaccinated M. smegmatis with pMyong2 system expressing Human Immunodeficiency Virus Type I (HIV-1) Gag p24 antigen (rSmeg-pMyong2-p24) into mice and examined its cellular and humoral immune responses against HIV gag protein. We found that rSmeg-pMyong2-p24 expressed higher levels of Gag protein in bacteria, macrophage cell line (J774A.1) and mouse bone marrow derived dendritic cells (BMDCs) compared to rSmeg strains using two other vector systems, pAL5000 derived vector (rSmeg-pAL-p24) and the integrative plasmid, pMV306 (rSmeg-pMV306-p24). Inoculation of mice with rSmeg-pMyong2-p24 elicited more effective immunity compared to the other two rSmeg strains, as evidenced by higher levels of HIV-1 Gag-specific CD4 and CD8 T lymphocyte proliferation, interferon gamma ELISPOT cell induction, and antibody production. Furthermore, rSmeg-pMyong2-p24 showed a higher level of cytotoxic T cell response against target cells expressing Gag p24 proteins. Our data suggest that Mycobacterium-Escherichia coli shuttle vector system with pMyong2 may provide an advantage in vaccine application of rSmeg over other vector systems.

Recombinant BCG expressing a PspA-PdT fusion protein protects mice against pneumococcal lethal challenge in a prime-boost strategy

Pneumococcal proteins have been evaluated as genetically-conserved potential vaccine candidates. We have previously demonstrated that a fragment of PspA in fusion with PdT (rPspA-PdT) induced protective immune responses in mice. However, purified proteins have shown poor immunogenicity and often require the combination with strong adjuvants and booster doses. Here, we investigated the use of a Bacillus Calmette-Guérin (BCG) strain, a well-established prophylactic vaccine for tuberculosis with known adjuvant properties, for delivery of the PspA-PdT fusion protein. Immunization of mice in a prime-boost strategy, using rPspA-PdT as a boost, demonstrated that rBCG PspA-PdT/rPspA-PdT was able to induce an antibody response against both proteins, promoting an IgG1 to IgG2 antibody isotype shift. Sera from rBCG PspA-PdT/rPspA-PdT immunized mice showed antibodies able to bind to the pneumococcal surface and promoted higher complement deposition when compared with WT-BCG/rPspA-PdT or a single dose of rPspA-PdT. In addition, these antisera inhibited the cytolytic activity of Ply. Production of interleukin-6 (IL-6), gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) was increased in splenocytes culture. Furthermore, a higher expression of CD69 early activation molecule was observed on splenic CD4⁺ T cells from mice immunized with rBCG PspA-PdT before and after the protein booster dose. Finally, immunization with rBCG PspA-PdT/rPspA-PdT protected mice against pneumococcal lethal challenge. These results support the further investigation of recombinant BCG strains to express pneumococcal proteins, which could be administered in early stages of life and lead to protective pneumococcal immunity in infants and children.

Nonmuscle invasive bladder cancer: a primer on immunotherapy

Intravesical Bacillus Calmette-Guérin (BCG) has long been the gold standard treatment of nonmuscle invasive bladder cancer. Recently, there has been an emergence of novel immunotherapeutic agents, which have shown promise in the treatment of urothelial cell carcinoma. These agents aim to augment, modify, or enhance the immune response. Such strategies include recombinant BCG, monoclonal antibodies, vaccines, gene therapy, and adoptive T-cell therapy. Here, we review the emerging immunotherapeutics in the treatment of nonmuscle invasive bladder cancer.

Novel immunotherapeutic approaches to the treatment of urothelial carcinoma

Immunotherapy has long played a role in urothelial cancers with the use of bacille Calmette Guérin (BCG) being a mainstay in the treatment of nonmuscle invasive bladder cancer. Novel therapeutic approaches have not significantly impacted mortality in this population and so a renaissance in immunotherapy has resulted. This includes recombinant BCG, oncolytic viruses, monoclonal antibodies, vaccines, and adoptive T-cell therapy. Herein, we provide a review of the current state of the art and future therapies regarding immunotherapeutic strategies for urothelial carcinoma.

Protein Complex Production in Alternative Prokaryotic Hosts

Research for multiprotein expression in nonconventional bacterial and archaeal expression systems aims to exploit particular properties of "alternative" prokaryotic hosts that might make them more efficient than E. coli for particular applications, especially in those areas where more conventional bacterial hosts traditionally do not perform well. Currently, a wide range of products with clinical or industrial application have to be isolated from their native source, often microorganisms whose growth present numerous problems owing to very slow growth phenotypes or because they are unculturable under laboratory conditions. In those cases, transfer of the gene pathway responsible for synthesizing the product of interest into a suitable recombinant host becomes an attractive alternative solution. Despite many efforts dedicated to improving E. coli systems due to low cost, ease of use, and its dominant position as a ubiquitous expression host model, many alternative prokaryotic systems have been developed for heterologous protein expression mostly for biotechnological applications. Continuous research has led to improvements in expression yield through these non-conventional models, including Pseudomonas, Streptomyces and Mycobacterium as alternative bacterial expression hosts. Advantageous properties shared by these systems include low costs, high levels of secreted protein products and their safety of use, with non-pathogenic strains been commercialized. In addition, the use of extremophilic and halotolerant archaea as expression hosts has to be considered as a potential tool for the production of mammalian membrane proteins such as GPCRs.

Applications of bacillus Calmette-Guerin and recombinant bacillus Calmette-Guerin in vaccine development and tumor immunotherapy

Bacillus Calmette-Guerin (BCG) vaccines are attenuated live strains of Mycobacterium bovis and are among the most widely used vaccines in the world. BCG is proven to be effective in preventing severe infant meningitis and miliary tuberculosis. Intravesical instillation of BCG is also a standard treatment for non-muscle invasive bladder cancer. In the past few decades, recombinant BCG (rBCG) technology had been extensively applied to develop vaccine candidates for a variety of infectious diseases, including bacterial, viral, and parasite infections, and to improve the efficacy of BCG in bladder cancer therapy. This review is intended to show the vast applications of BCG and recombinant BCG (rBCG) in the prevention of infectious diseases and cancer immunotherapy, with a special emphasis on recent approaches and trends on both pre-clinical and clinical levels.

A new recombinant BCG vaccine induces specific Th17 and Th1 effector cells with higher protective efficacy against tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) that is a major public health problem. The vaccine used for TB prevention is Mycobacterium bovis bacillus Calmette-Guérin (BCG), which provides variable efficacy in protecting against pulmonary TB among adults. Consequently, several groups have pursued the development of a new vaccine with a superior protective capacity to that of BCG. Here we constructed a new recombinant BCG (rBCG) vaccine expressing a fusion protein (CMX) composed of immune dominant epitopes from Ag85C, MPT51, and HspX and evaluated its immunogenicity and protection in a murine model of infection. The stability of the vaccine in vivo was maintained for up to 20 days post-vaccination. rBCG-CMX was efficiently phagocytized by peritoneal macrophages and induced nitric oxide (NO) production. Following mouse immunization, this vaccine induced a specific immune response in cells from lungs and spleen to the fusion protein and to each of the component recombinant proteins by themselves. Vaccinated mice presented higher amounts of Th1, Th17, and polyfunctional specific T cells. rBCG-CMX vaccination reduced the extension of lung lesions caused by challenge with Mtb as well as the lung bacterial load. In addition, when this vaccine was used in a prime-boost strategy together with rCMX, the lung bacterial load was lower than the result observed by BCG vaccination. This study describes the creation of a new promising vaccine for TB that we hope will be used in further studies to address its safety before proceeding to clinical trials.

Recombinant bacillus Calmette-Guérin in urothelial bladder cancer immunotherapy: current strategies

Bacillus Calmette-Guérin (BCG) has been used in the intravesical treatment of urothelial bladder cancer (UBC) for three decades. Despite its efficacy, intravesical BCG therapy is associated with some limitations such as side effects and BCG failure, which have inspired multiple ways to improve it. Recent advances have focused on recombinant BCG (rBCG) which provides a novel tactic for modification of BCG. To date, a number of rBCG strains have been developed and demonstrated to encourage efficacy and safety in preclinical and clinical studies. This review summarizes current rBCG strategies, concerns and future directions in UBC immunotherapy with an intention to encourage further research and eventually to inform clinical decisions.

Genetically detoxified pertussis toxin (PT-9K/129G): implications for immunization and vaccines

Pertussis toxin (PT) is one of the major virulence factors of Bordetella pertussis and the primary component of all pertussis vaccines available to date. Because of its various noxious effects the toxin needs to be detoxified. In all currently available vaccines, detoxification is achieved by treatment with high quantity of chemical agents such as formaldehyde, glutaraldehyde or hydrogen peroxide. Although effective in detoxification, this chemical treatment alters dramatically the immunological properties of the toxin. In contrast, PT genetically detoxified through the substitution of two residues necessary for its enzymatic activity maintains all functional and immunological properties. This review describes in detail the characteristics of this PT-9K/129G mutant and shows that it is non-toxic and a superior immunogen compared with chemically detoxified PT. Importantly, data from an efficacy trial show that the PT-9K/129G-based vaccine induces earlier and longer-lasting protection, further supporting the hypothesis that PT-9K/129G represents an ideal candidate for future pertussis vaccine formulations.

Expression, Purification and Characterization of Three Overlapping Immunodominant Recombinant Fragments from Bordetella pertussis Filamentous Hemagglutinin

BACKGROUND

Filamentous hemagglutinin (FHA) is one of the most important immunoprotective antigens of Bordetella pertussis (B. pertussis) and a major component of the acellular pertussis vaccine. In the present study, three overlapping recombinant fragments from the immunodominant region of FHA were produced and their immunogenicity was investigated.

METHODS

Three overlapping coding sequences of FHA antigen were amplified from B. pertussis genomic DNA by PCR. Amplified fragments were expressed in Escherichia coli (E. coli) BL21(DE3) strain and purified through His-tag using Nickel-based chromatography. Purified fragments were characterized by SDS-PAGE and Western blotting techniques. In vitro peripheral blood mononuclear cells (PBMC) proliferation and IFN-γ production were assessed in a limited number of healthy adults vaccinated with a commercial acellular pertussis vaccine in response to all purified FHA fragments by H3-Thymidine incorporation and ELISA, respectively.

RESULTS

Recombinant FHA segments were successfully cloned and produced at high levels in E. coli BL21(DE3). SDS-PAGE and Western blot analyses confirmed their purity and reactivity. All three recombinant fragments together with a commercial native FHA were able to induce in vitro PBMC proliferation and IFN-γ production.

CONCLUSION

Our preliminary results suggest that these overlapping recombinant FHA fragments are immunogenic and may prove to be immuno-protective.

Recombinant vaccines and the development of new vaccine strategies

Vaccines were initially developed on an empirical basis, relying mostly on attenuation or inactivation of pathogens. Advances in immunology, molecular biology, biochemistry, genomics, and proteomics have added new perspectives to the vaccinology field. The use of recombinant proteins allows the targeting of immune responses focused against few protective antigens. There are a variety of expression systems with different advantages, allowing the production of large quantities of proteins depending on the required characteristics. Live recombinant bacteria or viral vectors effectively stimulate the immune system as in natural infections and have intrinsic adjuvant properties. DNA vaccines, which consist of non-replicating plasmids, can induce strong long-term cellular immune responses. Prime-boost strategies combine different antigen delivery systems to broaden the immune response. In general, all of these strategies have shown advantages and disadvantages, and their use will depend on the knowledge of the mechanisms of infection of the target pathogen and of the immune response required for protection. In this review, we discuss some of the major breakthroughs that have been achieved using recombinant vaccine technologies, as well as new approaches and strategies for vaccine development, including potential shortcomings and risks.

Immunization of mice with Lactobacillus casei expressing a beta-intimin fragment reduces intestinal colonization by Citrobacter rodentium

Enteropathogenic Escherichia coli (EPEC) is a common cause of diarrhea in children from developing countries. Intimate adhesion of the bacteria to intestinal cells occurs via binding of the adhesin intimin to the TIR receptor exposed on cell surfaces. Here, Lactobacillus casei expressing a fragment of β-intimin (L. casei-Int(cv)) was tested as mucosal vaccines in mice against intestinal colonization with the murine pathogen Citrobacter rodentium. Oral or sublingual immunization of C57BL/6 mice with L. casei-Int(cv) induced anti-Int(cv) IgA in feces but no IgG in sera. Conversely, anti-Int(cv) IgG was induced in the sera of mice after sublingual immunization with purified Int(cv). All vaccines were able to decrease C. rodentium recovery from feces. However, this reduction was more evident and sustained over time in mice immunized with L. casei-Int(cv) by the sublingual route. These mice also displayed an increase in interleukin 6 (IL-6) and gamma interferon (IFN-γ) secretion by spleen cells 10 days after infection. Additionally, oral or sublingual immunization of C3H/HePas mice, which are highly susceptible to C. rodentium infection, with L. casei-Int(cv) induced anti-Int(cv) antibodies and significantly increased survival after challenge. Immunohistological analysis of colon sections revealed that C. rodentium was located in deep fractions of the tissue from C3H/HePas mice immunized with L. casei whereas superficial staining was observed in colon sections from mice immunized with L. casei-Int(cv.) The results indicate that vaccines composed of L. casei expressing intimin may represent a promising approach and that the C3H/HePas infection model with C. rodentium can be used to evaluate potential vaccines against EPEC.

Immunological Links to Nonspecific Effects of DTwP and BCG Vaccines on Infant Mortality

A number of mainly observational studies suggest that many African females below the age of one year die each year from the nonspecific effects of vaccination with diphtheria-tetanus toxoids and killed (whole-cell) Bordetella pertussis (DTwP). In contrast, similar studies suggest that many African females and males may have their lives saved each year by the nonspecific immunological benefits of Bacillus Calmette-Guerin (BCG) vaccination. From an immunological point of view, we hypothesise that the adverse effects of DTwP vaccine may occur because of the Th2-polarising effect of the aluminium phosphate adjuvant in the vaccine and because intramuscular administration of the vaccine may cause chronic inflammation at the site of injection. However, the Th1-polarising effect of BCG is likely to be beneficial. Sexual dimorphism affecting immune functions and vitamin A supplementation may influence both the deleterious and beneficial nonspecific effects of immunisation.

Fusion expression and immunogenicity of Bordetella pertussis PTS1-FHA protein: implications for the vaccine development

Mutants of pertussis toxin (PT) S1 subunit and filamentous hemagglutinin (FHA) type I immunodominant domain from Bordetella pertussis (B. pertussis) are considered to be effective candidate antigens for acellular pertussis vaccines; however, the substantial progress is hampered in part for the lack of a suitable in vitro expression system. In this paper, the gene sequences of a S1 mutant C180-R9K/E129G (mS1) and a truncated peptide named Fs from FHA type I immunodominant domain were linked together and constructed to pET22b expression vector as a fusion gene; after inducing with IPTG, it was highly expressed in E. coli BL21 (DE3) as inclusion body. The fusion protein FsmS1 was purified from cell lysates and refolded successfully. The result of Western blotting indicate that it was able to react with both anti-S1 and anti-FHA McAbs; antiserum produced from New Zealand white rabbits immunized with this protein was able to recognize both native PT and FHA antigens as determined by western blotting. These data have provided a novel feasible method to produce PT S1 subunit and FHA type I immunodominant domain in large scale in vitro, which is implicated for the development of multivalent subunit vaccines candidate against B. pertussis infection.

Oral immunogenicity of tomato-derived sDPT polypeptide containing Corynebacterium diphtheriae, Bordetella pertussis and Clostridium tetani exotoxin epitopes

DPT vaccine, designed to immunize against diphtheria, pertussis, and tetanus, has been shown to be effective in humans. Nevertheless, dissatisfaction with the whole-cell preparations is due to the reactogenicity, which has to lead to the development of new safer formulations. Previously, we described the expression in tomato of a plant-optimized synthetic gene encoding the recombinant polypeptide sDPT, containing mainly immunoprotective epitopes of the diphtheria, pertussis and tetanus exotoxins and two adjuvants. In this study, we examined whether the ingestion of tomato-derived sDPT protein induces specific antibodies in mice after three weekly doses scheme. A positive group immunized with DPT toxoids was included. Specific antibody levels were assessed in serum, gut and lung. Sera tested for IgG antibody response to pertussis, tetanus and diphtheria toxin showed responses to the foreign antigens; interestingly, the response to diphtheria epitope was similar to those observed in the positive group. We found higher IgG1 than IgG2a responses in serum. A modest IgG response was observed in the tracheopulmonary fluid. High response of IgA against tetanus toxin was evident in gut, which was statistically comparable to that obtained in the positive group. The levels of response in these groups were higher than those in mice that received wild-type tomato. These findings support the concept of using transgenic tomatoes expressing sDPT polypeptide as model for edible vaccine against diphtheria, pertussis, and tetanus.

Enhancement of Th1 lung immunity induced by recombinant Mycobacterium bovis Bacillus Calmette-Guerin attenuates airway allergic disease

Mycobacterium bovis Bacillus Calmette-Guerin (BCG) has been shown to down-regulate experimental allergic asthma, a finding that reinforced the hygiene hypothesis. We have previously found that recombinant BCG (rBCG) strain that express the genetically detoxified S1 subunit of pertussis toxin (rBCG-S1PT) exerts an adjuvant effect that enhances Th1 responses against BCG proteins. Here we investigated the effect of this rBCG-S1PT on the classical ovalbumin-induced mouse model of allergic lung disease. We found that rBCG-S1PT was more effective than wild-type BCG in preventing Th2-mediated allergic immune responses. The inhibition of allergic lung disease was not associated with increased concentration of suppressive cytokines or with an increased number of pulmonary regulatory T cells but was positively correlated with the increase in IFN-gamma-producing T cells and T-bet expression in the lung. In addition, an IL-12-dependent mechanism appeared to be important to the inhibition of lung allergic disease. The inhibition of allergic inflammation was found to be restricted to the lung because when allergen challenge was given by the intraperitoneal route, rBCG-S1PT administration failed to inhibit peritoneal allergic inflammation and type 2 cytokine production. Our work offers a nonclassical interpretation for the hygiene hypothesis indicating that attenuation of lung allergy by rBCG could be due to the enhancement of local lung Th1 immunity induced by rBCG-S1PT. Moreover, it highlights the possible use of rBCG strains as multipurpose immunomodulators by inducing specific immunity against microbial products while protecting against allergic asthma.

Construction of an unmarked recombinant BCG expressing a pertussis antigen by auxotrophic complementation: protection against Bordetella pertussis challenge in neonates

Mycobacterium bovis BCG has long been investigated as a candidate for heterologous antigen presentation. We have previously described an rBCG-Pertussis that confers protection against challenge with Bordetella pertussis in neonate and adult mice. In order to obtain stable expression in vivo, we constructed an unmarked BCG lysine auxotrophic and a complementation vector containing the lysine and the genetically detoxified S1 pertussis toxin genes, both under control of the same promoter. Complemented BCG-Delta lysine growth and expression of the pertussis antigen were stable, without the use of an antibiotic marker. Our results show that the complemented rBCG-Delta lysA-S1PT-lysA(+)(kan(-)), which is now suitable to be evaluated in clinical trials, maintains similar characteristics of the original rBCG-pNL71S1PT strain, such as the antigen expression level, cellular immune response and protection against the same model challenge in neonatal-immunized mice.

Recombinant Mycobacterium bovis BCG

The Bacillus Calmette-Guerin (BCG) is an attenuated strain of Mycobacterium bovis that has been broadly used as a vaccine against human tuberculosis. This live bacterial vaccine is able to establish a persistent infection and induces both cellular and humoral immune responses. The development of mycobacterial genetic systems to express foreign antigens and the adjuvanticity of BCG are the basis of the potential use of this attenuated mycobacterium as a recombinant vaccine. Over the years, a range of strategies has been developed to allow controlled and stable expression of viral, bacterial and parasite antigens in BCG. Herein, we review the strategies developed to express heterologous antigens in BCG and the immune response elicited by recombinant BCG constructs. In addition, the use of recombinant BCG as an immunomodulator and future perspectives of BCG as a recombinant vaccine vector are discussed.

Construction of EGFP-tagged rBCG of E.tenella and distribution in chickens

Chicken coccidiosis is a major parasitic disease with substantial economic burden to the poultry industry. Enhanced green fluorescent protein (EGFP) tagged recombinant Bacille Calmette-Guerin (rBCG), as a fusion protein with coccidian rhomboid antigen was constructed to track rBCG in vivo in chickens in this study. Immunization of chickens with one dose of rBCG pMV361-Rho/EGFP induced humoral immune response. The colonization of rBCG in liver, spleen, lung, kidney and caecum was observed by laser confocal microscopy. Real-time quantitative RT-PCR showed a rise expression level of rhomboid protein on the 7th day and a peak on the 14th day and disappearance on the 28th day after immunization. These results have significant implications for the development of rBCG vaccines against avian coccidiosis.

Recombinant Mycobacterium bovis BCG prime-recombinant adenovirus boost vaccination in rhesus monkeys elicits robust polyfunctional simian immunodeficiency virus-specific T-cell responses

While mycobacteria have been proposed as vaccine vectors because of their persistence and safety, little has been done systematically to optimize their immunogenicity in nonhuman primates. We successfully generated recombinant Mycobacterium bovis BCG (rBCG) expressing simian immunodeficiency virus (SIV) Gag and Pol as multigenic, nonintegrating vectors, but rBCG-expressing SIV Env was unstable. A dose and route determination study in rhesus monkeys revealed that intramuscular administration of rBCG was associated with local reactogenicity, whereas intravenous and intradermal administration of 10(6) to 10(8) CFU of rBCG was well tolerated. After single or repeat rBCG inoculations, monkeys developed high-frequency gamma interferon enzyme-linked immunospot responses against BCG purified protein derivative. However, the same animals developed only modest SIV-specific CD8(+) T-cell responses. Nevertheless, high-frequency SIV-specific cellular responses were observed in the rBCG-primed monkeys after boosting with recombinant adenovirus 5 (rAd5) expressing the SIV antigens. These cellular responses were of greater magnitude and more persistent than those generated after vaccination with rAd5 alone. The vaccine-elicited cellular responses were predominantly polyfunctional CD8(+) T cells. These findings support the further exploration of mycobacteria as priming vaccine vectors.

The therapeutic potential of recombinant BCG expressing the antigen S1PT in the intravesical treatment of bladder cancer

PURPOSE

Bacillus Calmette-Guerin (BCG) continues to be employed as the most effective immunotherapy against superficial bladder cancer. We have developed an rBCG-S1PT strain that induces a stronger cellular immune response than BCG. This preclinical study was designed to test the potential of rBCG-S1PT as an immunotherapeutic agent for intravesical bladder cancer therapy.

MATERIALS AND METHODS

A tumor was induced in C57BL/6 mice after chemical cauterization of the bladder and inoculation of the tumor cell line MB49. Next, mice were treated by intravesical instillation with BCG, rBCG-S1PT, or PBS once a week for 4 weeks. After 35 days, the bladders were removed and weighed, Th1 (IL-2, IL-12, INOS, INF-gamma, TNF-alpha), and Th2 (IL-5, IL-6, IL-10, TGF-beta) cytokine mRNA responses in individual mice bladders were measured by quantitative real time PCR, and the viability of MB49 cells in 18-hour coculture with splenocytes from treated mice was assessed. In an equivalent experiment, animals were observed for 60 days to quantify their survival.

RESULTS

Both BCG and rBCG-S1PT immunotherapy resulted in bladder weight reduction, and rBCG-S1PT increased survival time compared with the control group. There were increases in TNF-alpha in the BCG treated group, as well as increases in TNF-alpha and IL-10 mRNA in the rBCG-S1PT group. The viability of MB49 cells cocultured with splenocytes from rBCG-S1PT-treated mice was lower than in both the BCG and control groups.

CONCLUSIONS

rBCG-S1PT therapy improved outcomes and lengthened survival times. These results indicate that rBCG could serve as a useful substitute for wild-type BCG.