Recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) expressing mouse IL-18 augments Th1 immunity and macrophage cytotoxicity

Nano-Bacillus Calmette-Guérin immunotherapies for improved bladder cancer treatment

Cancer immunotherapy has rapidly become the fourth mainstream treatment alternative after surgery, radiotherapy, and chemotherapy, with some promising results. It aims to kill tumor cells by mobilizing or stimulating cytotoxic immune cells. However, the clinical applications of tumor immunotherapies are limited owing to a lack of adequate delivery pathways and high toxicity. Recently, nanomaterials and genetic engineering have shown great potential in overcoming these limitations by protecting the delivery of antigens, activating targeted T cells, modulating the immunosuppressive tumor microenvironment, and improving the treatment efficacy. Bacillus Calmette-Guérin (BCG) is a live attenuated Mycobacterium bovis vaccine used to prevent tuberculosis, which was first reported to have antitumor activity in 1927. BCG therapy can activate the immune system by inducing various cytokines and chemokines, and its specific immune and inflammatory responses exert antitumor effects. BCG was first used during the 1970s as an intravesical treatment agent for bladder cancer, which effectively improved immune antitumor activity and prevented tumor recurrence. More recently, nano-BCG and genetically engineered BCG have been proposed as treatment alternatives for bladder cancer due to their ability to induce stronger and more stable immune responses. In this study, we outline the development of nano-BCG and genetically engineered BCG for bladder cancer immunotherapy and review their potential and associated challenges.

Detailed Structural Analysis of the Immunoregulatory Polysaccharides from the Mycobacterium Bovis BCG

Bacillus Calmette-Guérin polysaccharide and nucleic acid (BCG-PSN), extracted from Mycobacterium bovis, is an immunoregulatory medicine commonly used in clinic. However, the structural characteristics and potential pharmacological efficacy of the polysaccharides from BCG-PSN remain unclear. Herein, two polysaccharides (BCG-1 and BCG-2) were purified and their structures were characterized. Monosaccharide composition analysis combined with methylation analysis and NMR data indicated that BCG-1 and BCG-2 were an α-D-(1→4)-mannan with (1→2)-linked branches, and an α-D-(1→4)-glucan with (1→6)-linked branches, respectively. Herein, the mannan from BCG-PSN was first reported. Bioactivity assays showed that BCG-1 and BCG-2 dose-dependently and potently increased the production of inflammatory mediators (NO, TNF-α, IL-6, IL-1β, and IL-10), as well as their mRNA expressions in RAW264.7 cells; both have similar or stronger effects compared with BCG-PSN injection. These data suggest that BCG-1 and BCG-2 are very likely the active ingredients of BCG-PSN.

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.

Mycobacterium bovis Wild-Type BCG or Recombinant BCG Secreting Murine IL-18 (rBCG/IL-18) Strains in Driving Immune Responses in Immunocompetent or Immunosuppressed Mice

Mycobacterium tuberculosis infections remain a global health problem in immunosuppressed patients. The effectiveness of BCG (Bacillus Calmette−Guérin), an anti-tuberculosis vaccine, is unsatisfactory. Finding a new vaccine candidate is a priority. We compared numerous immune markers in BCG-susceptible C57BL/6 and BCG-resistant C3H mice who had been injected with 0.9% NaCl (control) or with wild-type BCG or recombinant BCG secreting interleukin (IL)-18 (rBCG/IL-18) and in immunized mice who were immunocompromised with cyclophosphamide (CTX). The inoculation of rBCG/IL-18 in immunocompetent mice increased the percentage of bone marrow myeloblasts and promyelocytes, which were further elevated in the rBCG/IL-18/CTX-treated mice: C57BL/6 mice—3.0% and 11.4% (control) vs. 18.6% and 42.4%, respectively; C3H mice—1.1% and 7.7% (control) vs. 18.4% and 44.9%, respectively, p < 0.05. The bone marrow cells showed an increased mean fluorescence index (MFI) in the CD34 adhesion molecules: C57BL/6 mice—4.0 × 103 (control) vs. 6.2 × 103; C3H mice—4.0 × 103 (control) vs. 8.0 × 103, p < 0.05. Even in the CTX-treated mice, the rBCG/IL-18 mobilized macrophages for phagocytosis, C57BL/6 mice—4% (control) vs. 8%; C3H mice—2% (control) vs. 6%, and in immunocompetent mice, C57BL/6 induced the spleen homing of effector memory CD4+ and CD8+ T cells (TEM), 15% (control) vs. 28% and 8% (control) vs. 22%, respectively, p < 0.05. In conclusion, rBCG/IL-18 effectively induced selected immune determinants that were maintained even in immunocompromised mice.

FimH confers mannose-targeting ability to Bacillus Calmette-Guerin for improved immunotherapy in bladder cancer

BACKGROUND

Bladder cancer is a common disease worldwide with most patients presenting with the non-muscle-invasive form (NMIBC) at initial diagnosis. Postoperational intravesical instillation of BCG is carried out for patients with high-risk disease to reduce tumor recurrence and progression to muscle invasive disease. However, BCG can also have side effects or be ineffective in some patients because it cannot enter the cancer cells. Thus, to improve the efficacy of BCG immunotherapy is the long-term pursuit of the bladder cancer field.

METHODS

To increase the adhesion of BCG to the urothelium we overexpressed FimH, a mannose binding protein naturally used by uropathogenic Escherichia coli to adhere to human urothelium, onto the surface of BCG. The adhesion/internalization ability of rBCG-S.FimH was examined in mouse bladder by fluorescence microscopy. Preclinical evaluation of antitumor efficacy was carried out in orthotopic mouse models of bladder cancer and in human peripheral blood mononuclear cells. Mechanistic studies were carried out using toll-like receptor 4 (TLR4) knockout mice. Immune cells and cytokines in the serum, tumor and lymph nodes were analyzed by flow cytometry, PCR, ELISA and ELISPOT.

RESULTS

rBCG-S.FimH exhibited markedly improved adhesion and more rapid internalization into urothelial cells than wild-type BCG, resulting in more potent antitumor activity in orthotopic murine models of bladder cancer. To our surprise, rBCG-S.FimH elicited a much more prominent Th1-biased immune response known to be positively correlated with BCG efficacy. Mechanistic studies using TLR4 knockout mouse showed that rBCG-S.FimH could induce enhanced dendritic cell activation and tumor antigen-specific immune response in a TLR4-dependent manner. Furthermore, human peripheral blood mononuclear cells stimulated by rBCG-S.FimH also showed better tumoricidal effects than those using wild-type BCG.

CONCLUSION

rBCG-S.FimH is a novel BCG strain with significantly improved efficacy against bladder cancer. Since intravesical BCG immunotherapy is the first-line treatment for NMIBC, which accounts for more than 70% of all bladder cancer cases, our results provide a compelling rationale for clinical development.

The inhibitory effect of rBCG on EB virus-positive tumours using an EB virus fusion gene

At present, studies have found that latent Epstein-Barr virus (EBV) infection is associated with a variety of human tumours, and a vaccine is not available in this field. In this research, RT-PCR was used to obtain BZLF1 (immediately expressed early antigen Z) and LMP2 (latent membrane protein 2) cDNA from EBV. A ZLP2 fusion gene containing a linker sequence that encoded the polypeptide (Gly₄Ser)₃ was obtained using the sequence splicing overlap extension method. Then, ZLP2 was inserted into pMV261 cells, and the recombinant plasmid pMV-ZLP2 was transformed into BCG competent cells. After EB virus-positive tumour cell (NPRC18) cancer models were established with C57BL/6 J mice, tumour weight, tumour formation time and mouse survival conditions were analyzed, and flow cytometry was used to analyze the quantities of CD8 + and CD4 + T cells. HE staining was used to detect and analyze lymphocyte infiltration, and statistical analysis was used to analyze the immunological effect of recombinant BCG (rBCG). Compared with the control group, rBCG could significantly prolong the survival time of mice, slow tumour growth and delay tumour formation time. Recombinant BCG exhibits an obvious immune effect in mice and an inhibitory effect on EBV-positive cancer.Key points• AZLP2 fusion gene with BZLF1 and LMP2 of EB virus was constructed.• ZLP2 fusion gene was expressed with rBCG.• rBCG with ZLP2 has an obvious effect on EBV-positive cancer.

BCG as a Vector for Novel Recombinant Vaccines against Infectious Diseases and Cancers

Bacillus Calmette-Guérin (BCG) has been widely used globally as a prophylactic vaccine to protect against tuberculosis (TB) for about a century [...].

The multifaceted immune regulation of bladder cancer

Bladder cancer is an important public health concern owing to its prevalence, high recurrence risk and treatment failures. Maintaining the equilibrium between prompt and effective immunity and an excessive and protracted immune response is critical for successful immune defence. This delicate balance is ensured by intrinsic or extrinsic immunoregulatory mechanisms. Intrinsic control of immune cell activation is mediated by stimulatory and inhibitory receptors expressed on the effector cell itself, whereas extrinsic control is mediated via other immune cells by cell-cell contact and/or secretion of inhibitory factors. Tumours can exacerbate these immunosuppressive pathways, fostering a tolerant microenvironment. These mechanisms have previously been poorly described in urothelial carcinoma, but a growing body of evidence highlights the key role of immune regulation in bladder cancer. This process includes immune checkpoints (mostly programmed cell death 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1)), as well as regulatory T cells, myeloid-derived suppressor cells, tumour-associated macrophages and type 2 innate and adaptive lymphocytes. For each component, quantitative and qualitative alterations, clinical relevance and potential targeting strategies are currently being explored. An improved understanding of immune regulation pathways in bladder cancer development, recurrence and progression will help in the design of novel diagnostic and prognostic tools as well as treatments.

Mycobacterium bovis BCG in metastatic melanoma therapy

Melanoma is the most aggressive form of skin cancer, with a high mortality rate and with 96,480 new cases expected in 2019 in the USS. BRAF^V600E, the most common driver mutation, is found in around 50% of melanomas, contributing to tumor growth, angiogenesis, and metastatic progression. Dacarbazine (DTIC), an alkylate agent, was the first chemotherapeutic agent approved by the US Food and Drug Administration (FDA) used as a standard treatment. Since then, immunotherapies have been approved for metastatic melanoma (MM) including ipilimumab and pembrolizumab checkpoint inhibitors that help decrease the risk of progression. Moreover, Mycobacterium bovis Bacillus Calmette-Guerin (BCG) serves as an adjuvant therapy that induces the recruitment of natural killer NK, CD4⁺, and CD8⁺ T cells and contributes to antitumor immunity. BCG can be administered in combination with chemotherapeutic and immunotherapeutic agents and can be genetically manipulated to produce recombinant BCG (rBCG) strains that express heterologous proteins or overexpress immunogenic proteins, increasing the immune response and improving patient survival. In this review, we highlight several studies utilizing rBCG immunotherapy for MM in combination with other therapeutic agents.

Next-Generation Vaccines Based on Bacille Calmette-Guérin

Tuberculosis (TB), caused by the intracellular bacterium Mycobacterium tuberculosis (Mtb), remains a major health threat. A live, attenuated mycobacterium known as Bacille Calmette-Guérin (BCG), derived from the causative agent of cattle TB, Mycobacterium bovis, has been in clinical use as a vaccine for 90 years. The current incidence of TB demonstrates that BCG fails to protect sufficiently against pulmonary TB, the major disease manifestation and source of dissemination. The protective efficacy of BCG is on average 50% but varies substantially with geographical location and is poorer in those with previous exposure to mycobacteria. BCG can also cause adverse reactions in immunocompromised individuals. However, BCG has contributed to reduced infant TB mortality by protecting against extrapulmonary TB. In addition, BCG has been associated with reduced general childhood mortality by stimulating immune responses. In order to improve the efficacy of BCG, two major strategies have been employed. The first involves the development of recombinant live mycobacterial vaccines with improved efficacy and safety. The second strategy is to boost BCG with subunit vaccines containing Mtb antigens. This article reviews recombinant BCG strains that have been tested against TB in animal models. This includes BCG strains that have been engineered to induce increased immune responses by the insertion of genes for Mtb antigens, mammalian cytokines, or host resistance factors, the insertion of bacterial toxin-derived adjuvants, and the manipulation of bacterial genes in order to increase antigen presentation and immune activation. Subunit vaccines for boosting BCG are also briefly discussed.

Deletion of BCG Hip1 protease enhances dendritic cell and CD4 T cell responses

Dendritic cells (DCs) play a key role in the generation of CD4 T cell responses to pathogens. Mycobacterium tuberculosis (Mtb) harbors immune evasion mechanisms that impair DC responses and prevent optimal CD4 T cell immunity. The vaccine strain Mycobacterium bovis Bacille Calmette-Guérin (BCG) shares many of the immune evasion proteins utilized by Mtb, but the role of these proteins in DC and T cell responses elicited by BCG is poorly understood. We previously reported that the Mtb serine protease, Hip1, promotes sub-optimal DC responses during infection. Here, we tested the hypothesis that BCG Hip1 modulates DC functions and prevents optimal antigen-specific CD4 T cell responses that limit the immunogenicity of BCG. We generated a strain of BCG lacking hip1 (BCGΔhip1) and show that it has superior capacity to induce DC maturation and cytokine production compared with the parental BCG. Furthermore, BCGΔhip1-infected DCs were more effective at driving the production of IFN-γ and IL-17 from antigen-specific CD4 T cells in vitro. Mucosal transfer of BCGΔhip1-infected DCs into mouse lungs induced robust CD4 T cell activation in vivo and generated antigen-specific polyfunctional CD4 T cell responses in the lungs. Importantly, BCGΔhip1-infected DCs enhanced control of pulmonary bacterial burden following Mtb aerosol challenge compared with the transfer of BCG-infected DCs. These results reveal that BCG employs Hip1 to impair DC activation, leading to attenuated lung CD4 T cell responses with limited capacity to control Mtb burden after challenge.

Mycobacterium bovis Bacillus Calmette-Guérin Alters Melanoma Microenvironment Favoring Antitumor T Cell Responses and Improving M2 Macrophage Function

Intralesional Mycobacterium bovis bacillus Calmette-Guérin (BCG) has long been a relatively inexpensive therapy for inoperable cutaneous metastatic melanoma (CMM), although intralesional BCG skin mechanisms remain understudied. We analyzed intralesional BCG-treated CMM lesions combined with in vitro studies to further investigate BCG-altered pathways. Since macrophages play a pivotal role against both cancer and mycobacterial infections, we hypothesized BCG regulates macrophages to promote antitumor immunity. Tumor-associated macrophages (M2) infiltrate melanomas and impair antitumor immunity. BCG-treated, in vitro-polarized M2 (M2-BCG) showed transcriptional changes involving inflammation, immune cell recruitment, cross talk, and activation pathways. Mechanistic network analysis indicated M2-BCG potential to improve interferon gamma (IFN-γ) responses. Accordingly, frequency of IFN-γ-producing CD4+ T cells responding to M2-BCG vs. mock-treated M2 increased (p < 0.05). Moreover, conditioned media from M2-BCG vs. M2 elevated the frequency of granzyme B-producing CD8+ tumor-infiltrating lymphocytes (TILs) facing autologous melanoma cell lines (p < 0.01). Furthermore, transcriptome analysis of intralesional BCG-injected CMM relative to uninjected lesions showed immune function prevalence, with the most enriched pathways representing T cell activation mechanisms. In vitro-infected MM-derived cell lines stimulated higher frequency of IFN-γ-producing TIL from the same melanoma (p < 0.05). Our data suggest BCG favors antitumor responses in CMM through direct/indirect effects on tumor microenvironment cell types including macrophages, T cells, and tumor itself.

Recombinant Bacille Calmette-Guérin coexpressing Ag85B-IFN-γ enhances the cell-mediated immunity in C57BL/6 mice

The only available vaccine against pulmonary tuberculosis is Bacille Calmette-Guérin (BCG). As the efficacy reported of the vaccine is not up to the mark, there is an urgent need to develop improved anti-tuberculosis vaccines. Antigen 85B (Ag85B) is a very promising vaccine candidate molecule of Mycobacterium tuberculosis and interferon (IFN)-γ and has been considered the most attractive correlate of protective immunity. The aim of this study was to construct a novel recombinant BCG (rBCG) to secrete Ag85B and mouse IFN-γ under control of the Mycobacterial heat shock protein 60 (hsp60) promoter and the antigen signal sequence. Second aim of the present study is to evaluate the immune response in C57BL/6 elicted by the new rBCG. Expression of the fusion protein was readily detectable by western blotting and IFN-γ bioactivity was detected indirectly by enzyme-linked immunosorbent assay (ELISA). Compared with BCG, rBCG::Ag85B-IFN-γ was substantially more active in inducing the production of IFN-γ and tumor necrosis factor (TNF)-α from mouse splenocytes. ELISA analysis for IgG, IgG1 and IgG2c showed that rBCG::Ag85B-IFN-γ induced higher titer of Ag85B and facilitated Th1 type immune response. rBCG::Ag85B-IFN-γ also improved nitric oxide production levels and enhanced antigen-specific splenocyte proliferation. Moreover, rBCG::Ag85B-IFN-γ induced human monocytes such as THP-1 cells to enhance expression of CD80, CD86, CD40 and HLA-DR. Flow cytometry analysis confirmed that rBCG::Ag85B-IFN-γ significantly activated CD4⁺ T cells. Assessing combinations of IFN-γ, TNF-α and interleukin-2 at the single-cell level by multiparameter flow cytometry, we found that rBCG::Ag85B-IFN-γ improved the multifunctional T cells level in comparison to BCG. In conclusion, the present study indicates that rBCG::Ag85B-IFN-γ increases cell mediated immune response and is a potential candidate vaccine for immunotherapeutic protocols against pulmonary tuberculosis.

BCG and protection against inflammatory and auto-immune diseases

INTRODUCTION

Bacillus Calmette-Guérin (BCG) is the only available vaccine against tuberculosis. Although its protective efficacy against pulmonary tuberculosis is still under debate, it provides protection against other mycobacterial diseases. BCG is also an effective therapy against superficial bladder cancer and potentially decreases overall childhood mortality. Areas covered: The purpose of this paper is to provide a state-of-the-art summary of the beneficial effects of BCG in inflammatory and auto-immune diseases. As a strong inducer of Th1 type immunity, BCG has been reported to protect against atopic conditions, such as allergic asthma, a Th2-driven disorder. Its protective effect has been well documented in mice, but still awaits definitive evidence in humans. Similarly, murine studies have shown a protective effect of BCG against auto-immune diseases, such as multiple sclerosis and insulin-dependent diabetes, but studies in humans have come to conflicting conclusions. Expert commentary: Studies in mice have shown a beneficial effect of the BCG vaccine against allergic asthma, multiple sclerosis and diabetes. However, the understanding of its mechanism is still fragmentary and requires further in depth research. Some observational or intervention studies in humans have also suggested a beneficial effect, but definitive evidence for this requires confirmation in carefully conducted prospective studies.

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.

Independent Replication of Published Germline Polymorphisms Associated with Urinary Bladder Cancer Prognosis and Treatment Response

BACKGROUND

Many studies investigated the prognostic or predictive relevance of single nucleotide polymorphisms (SNPs) in biologically plausible genes in urinary bladder cancer (UBC) patients. Most published SNP associations have never been replicated in independent patient series.

OBJECTIVE

To independently replicate all previously reported associations between germline SNPs and disease prognosis or treatment response in UBC.

METHODS

A Pubmed search was performed to identify studies published by July 1, 2014 reporting on germline SNP associations with UBC prognosis or treatment response. For the replication series, consisting of 1,284 non-muscle-invasive bladder cancer (NMIBC) and 275 muscle-invasive or metastatic bladder cancer (MIBC) patients recruited through the Netherlands Cancer Registry, detailed clinical data were retrieved from medical charts. Patients were genotyped using a genome-wide SNP array. SNP association with recurrence-free, progression-free, and overall survival (OS) within specific patient and treatment strata was tested using Cox regression analyses.

RESULTS

For only six of the 114 evaluated SNPs, the association with either UBC prognosis or treatment response was replicated at the p <  0.05 level: rs1799793 (ERCC2) and rs187238 (IL18) for BCG recurrence; rs6678136 (RGS4) and rs11585883 (RGS5) for NMIBC progression; rs12035879 (RGS5) and rs2075786 (TERT) for MIBC OS.

CONCLUSIONS

Non-replicated genetic associations in the literature require cautious interpretation. This single replication does not provide definitive proof of association for the six SNPs, and non-replication of other SNPs may result from population-specific effects or the retrospective patient enrollment.

Dendritic Cell Activity Driven by Recombinant Mycobacterium bovis BCG Producing Human IL-18, in Healthy BCG Vaccinated Adults

Tuberculosis remains an enormous global burden, despite wide vaccination coverage with the Bacillus Calmette-Guérin (BCG), the only vaccine available against this disease, indicating that BCG-driven immunity is insufficient to protect the human population against tuberculosis. In this study we constructed recombinant BCG producing human IL-18 (rBCGhIL-18) and investigated whether human IL-18 produced by rBCGhIL-18 modulates DC functions and enhances Th1 responses to mycobacterial antigens in humans. We found that the costimulatory CD86 and CD80 molecules were significantly upregulated on rBCGhIL-18-infected DCs, whereas the stimulation of DCs with nonrecombinant BCG was less effective. In contrast, both BCG strains decreased the DC-SIGN expression on human DCs. The rBCGhIL-18 increased IL-23, IL-10, and IP-10 production by DCs to a greater extent than nonrecombinant BCG. In a coculture system of CD4⁺ T cells and loaded DCs, rBCGhIL-18 favoured strong IFN-γ but also IL-10 production by naive T cells but not by memory T cells. This was much less the case for nonrecombinant BCG. Thus the expression of IL-18 by recombinant BCG increases IL-23, IP-10, and IL-10 expression by human DCs and enhances their ability to induce IFN-γ and IL-10 expression by naive T cells, without affecting the maturation phenotype of the DCs.

Evolving immunotherapy strategies in urothelial cancer

The treatment of nonmuscle-invasive urothelial carcinoma with bacillus Calmette-Guérin (BCG) represents the importance of immunotherapy in the treatment of cancer. Despite its clinical efficacy, up to 30% of patients will ultimately experience progression to muscle-invasive disease. This, along with an improved understanding of the biologic pathways involved, has led to efforts to improve, enhance, or alter the immune response in the treatment of urothelial carcinoma. A number of novel therapeutic approaches currently are being pursued, including recombinant BCG to induce T helper type 1 (Th1) immune responses, nonlive Mycobacterium agents, targeted agents toward cancer-associated antigens, immune-modulating vaccines, and adoptive T-cell therapies. Here, we review the current and future immunotherapy treatment options for patients with urothelial cancer.

Immunomodulatory effects of recombinant BCG expressing MSP-1C of Plasmodium falciparum on LPS- or LPS+IFN-γ-stimulated J774A.1 cells

Macrophage phagocytosis is the first line of defense of the innate immune system against malaria parasite infection. This study evaluated the immunomodulatory effects of BCG and recombinant BCG (rBCG) strains expressing the C-terminus of the merozoite surface protein-1 (MSP-1C) of Plasmodium falciparum on mouse macrophage cell line J774A.1 in the presence or absence of lipopolysaccharide (LPS) or LPS + IFN-γ. The rBCG strain significantly enhanced phagocytic activity, production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, nitric oxide (NO), and inducible nitric oxide synthase (iNOS) as compared with parental BCG strain, and these activities increased in the presence of LPS and LPS+IFN-γ. Furthermore, the rBCG strain also significantly reduced the macrophage viability as well as the rBCG growth suggesting the involvement of macrophage apoptosis. Taken together, these data indicate that the rBCG strain has an immunomodulatory effect on macrophages, thus strengthen the rational use of rBCG to control malaria infection.

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.

The mechanism of action of BCG therapy for bladder cancer--a current perspective

Bacillus Calmette-Guérin (BCG) has been used to treat non-muscle-invasive bladder cancer for more than 30 years. It is one of the most successful biotherapies for cancer in use. Despite long clinical experience with BCG, the mechanism of its therapeutic effect is still under investigation. Available evidence suggests that urothelial cells (including bladder cancer cells themselves) and cells of the immune system both have crucial roles in the therapeutic antitumour effect of BCG. The possible involvement of bladder cancer cells includes attachment and internalization of BCG, secretion of cytokines and chemokines, and presentation of BCG and/or cancer cell antigens to cells of the immune system. Immune system cell subsets that have potential roles in BCG therapy include CD4(+) and CD8(+) lymphocytes, natural killer cells, granulocytes, macrophages, and dendritic cells. Bladder cancer cells are killed through direct cytotoxicity by these cells, by secretion of soluble factors such as TRAIL (tumour necrosis factor-related apoptosis-inducing ligand), and, to some degree, by the direct action of BCG. Several gaps still exist in our knowledge that should be addressed in future efforts to understand this biotherapy of cancer.

A novel subset of helper T cells promotes immune responses by secreting GM-CSF

Helper T cells are crucial for maintaining proper immune responses. Yet, they have an undefined relationship with one of the most potent immune stimulatory cytokines, granulocyte macrophage-colony-stimulating factor (GM-CSF). By depleting major cytokines during the differentiation of CD4(+) T cells in vitro, we derived cells that were found to produce large amounts of GM-CSF, but little of the cytokines produced by other helper T subsets. By their secretion of GM-CSF, this novel subset of helper T cells (which we have termed ThGM cells) promoted the production of cytokines by other T-cell subtypes, including type 1 helper T cell (Th1), type 2 helper T cell (Th2), type 1 cytotoxic T cell (Tc1), type 2 cytotoxic T cell (Tc2), and naive T cells, as evidenced by the fact that antibody neutralization of GM-CSF abolished this effect. ThGM cells were found to be highly prone to activation-induced cell death (AICD). Inhibitors of TRAIL or granzymes could not block AICD in ThGM cells, whereas inhibition of FasL/Fas interaction partially rescued ThGM cells from AICD. Thus, ThGM cells are a novel subpopulation of T helper cells that produce abundant GM-CSF, exhibit exquisite susceptibility to apoptosis, and therefore play a pivotal role in the regulation of the early stages of immune responses.

Antitumor effects of human interferon-alpha 2b secreted by recombinant bacillus Calmette-Guérin vaccine on bladder cancer cells

OBJECTIVE

Our objective was to construct a recombinant bacillus Calmette-Guérin vaccine (rBCG) that secretes human interferon-alpha 2b (IFNα-2b) and to study its immunogenicity and in vitro antitumor activity against human bladder cancer cell lines T24 and T5637.

METHODS

The signal sequence BCG Ag85B and the gene IFNα-2b were amplified from the genome of BCG and human peripheral blood, respectively, by polymerase chain reaction (PCR). The two genes were cloned in Escherichia coli-BCG shuttle-vector pMV261 to obtain a new recombinant plasmid pMV261-Ag85B-IFNα-2b. BCG was transformed with the recombinant plasmid by electroporation and designated rBCG-IFNα-2b. Mononuclear cells were isolated from human peripheral blood (PBMCs) and stimulated with rBCG-IFNα-2b or wild type BCG for 3 d, and then cultured with human bladder cancer cell lines T24 and T5637. Their cytotoxicities were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

RESULTS

BCG was successfully transformed with the recombinant plasmid pMV261-Ag85B-IFNα-2b by electroporation and the recombinant BCG (rBCG-IFNα-2b) was capable of synthesizing and secreting cytokine IFNα-2b. PBMC proliferation was enhanced significantly by rBCG-IFNα-2b, and the cytotoxicity of PBMCs stimulated by rBCG-IFNα-2b to T24 and T5627 was significantly stronger in comparison to wild type BCG.

CONCLUSIONS

A recombinant BCG, secreting human IFNα-2b (rBCG-IFNα-2b), was constructed successfully and was superior to control wild type BCG in inducing immune responses and enhancing cytotoxicity to human bladder cancer cell lines T24 and T5637. This suggests that rBCG-IFNα-2b could be a promising agent for bladder cancer patients in terms of possible reductions in both clinical dosage and side effects of BCG immunotherapy.

Co-immunization of plasmid DNA encoding IL-12 and IL-18 with Bacillus Calmette-Guérin vaccine against progressive tuberculosis

PURPOSE

Bacillus Calmette-Guérin (BCG) vaccine has widely been used to immunize against tuberculosis, but its protective efficacy is variable in adult pulmonary tuberculosis, while it is not efficiently protective against progressive infection of virulent Mycobacterium tuberculosis strains. In this study, the protective effects of plasmid DNA vaccine constructs encoding IL-12 or IL-18 with the BCG vaccine were evaluated against progressive infection of M. tuberculosis, using mouse aerosol challenge model.

MATERIALS AND METHODS

Plasmid DNA vaccine constructs encoding IL-12 or IL-18 were constructed and mice were immunized with the BCG vaccine or with IL-12 DNA or IL-18 DNA vaccine constructs together with the BCG vaccine.

RESULTS

The BCG vaccine induced high level of interferon gamma (IFN-γ) but co-immunization of IL-12 or IL-18 DNA vaccine constructs with the BCG vaccine induced significantly higher level of IFN-γ than a single BCG vaccine. The BCG vaccine was highly protective at early stage of M. tuberculosis infection, but its protective efficacy was reduced at later stage of infection. The co-immunization of IL-12 DNA vaccine constructs with the BCG vaccine was slightly more protective at early stage of infection and was significantly more protective at later stage infection than a single BCG vaccine.

CONCLUSION

Co-immunization of IL-12 DNA vaccine with the BCG vaccine induced more protective immunity and was more effective for protection against progressive infection of M. tuberculosis.

Recombinant BCG coexpressing Ag85B, CFP10, and interleukin-12 induces multifunctional Th1 and memory T cells in mice

Mycobacterium tuberculosis (MTB) continues to be a leading cause of human deaths due to an infectious agent. Current efforts are focused on making better TB vaccines. We describe the generation and immunological characterization of recombinant BCG (rBCG). This rBCG was generated by incorporating an expression plasmid encoding two mycobacterial antigens (Ag85B and CFP10) and human interleukin (IL)-12 into a BCG strain. Immunogenicity studies in mice showed that rBCG coexpressing Ag85B, CFP10, and IL-12 (rBCG::Ag85B-CFP10-IL-12) induces a robust immune response in mice. The rBCG vaccine promotes a T-cell response against MTB that is characterized by a high proportion of polyfunctional and memory T cells in spleen and lung. Our results showed strong immunogenicity and mycobacterial growth inhibition of rBCG::Ag85B-CFP10 plus IL-12 than that of BCG vaccine.

Th1 cytokine-secreting recombinant Mycobacterium bovis bacillus Calmette-Guérin and prospective use in immunotherapy of bladder cancer

Intravesical instillation of Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been used for treating bladder cancer for 3 decades. However, BCG therapy is ineffective in approximately 30–40% of cases. Since evidence supports the T helper type 1 (Th1) response to be essential in BCG-induced tumor destruction, studies have focused on enhancing BCG induction of Th1 immune responses. Although BCG in combination with Th1 cytokines (e.g., interferon-α) has demonstrated improved efficacy, combination therapy requires multiple applications and a large quantity of cytokines. On the other hand, genetic manipulation of BCG to secrete Th1 cytokines continues to be pursued with considerable interest. To date, a number of recombinant BCG (rBCG) strains capable of secreting functional Th1 cytokines have been developed and demonstrated to be superior to BCG. This paper discusses current rBCG research, concerns, and future directions with an intention to inspire the development of this very promising immunotherapeutic modality for bladder cancer.

MUC1-based recombinant Bacillus Calmette-Guerin vaccines as candidates for breast cancer immunotherapy

IMPORTANCE OF THE FIELD

The challenge in breast cancer vaccine development is to find the best combination of antigen, adjuvant and delivery system to produce a strong and long-lasting immune response. Mucin 1 (MUC1) is a potential candidate target for breast cancer immunotherapy. Bacillus Calmette-Guerin (BCG) is used widely in human vaccines. Furthermore, it can potentially offer unique advantages for developing a safe and effective multi-vaccine vehicle. Due to these properties, the development of MUC1 based recombinant BCG (rBCG) vaccines for breast cancer immunotherapy has gained great momentum in recent years.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss the recent progress in MUC1-based breast cancer immunotherapy and to highlight the advantages of MUC1-based rBCG vaccines as the new breast cancer vaccines.

WHAT THE READER WILL GAIN

Several promising MUC1-based rBCG vaccines have been shown to induce MUC1-specific antitumor immune responses in pre-clinical studies. This review updates and evaluates this very important and rapidly developing field, and provides a critical perspective and information source for its potential clinical applications.

TAKE HOME MESSAGE

MUC1-based rBCG vaccines have been shown to elicit an effective anti-tumor immune response in vivo demonstrating its potential utility in breast cancer treatment.

Mycobacterium bovis bacillus Calmette-Guérin-induced macrophage cytotoxicity against bladder cancer cells

Many details of the molecular and cellular mechanisms involved in Mycobacterium bovis bacillus Calmette-Guérin (BCG) immunotherapy of bladder cancer have been discovered in the past decades. However, information on a potential role for macrophage cytotoxicity as an effector mechanism is limited. Macrophages play pivotal roles in the host innate immunity and serve as a first line of defense in mycobacterial infection. In addition to their function as professional antigen-presenting cells, the tumoricidal activity of macrophages has also been studied with considerable interest. Studies have shown that activated macrophages are potent in killing malignant cells of various tissue origins. This review summarizes the current understanding of the BCG-induced macrophage cytotoxicity toward bladder cancer cells with an intention to inspire investigation on this important but underdeveloped research field.

IL-18 does not increase allergic airway disease in mice when produced by BCG

Whilst BCG inhibits allergic airway responses in murine models, IL-18 has adversary effects depending on its environment. We therefore constructed a BCG strain producing murine IL-18 (BCG-IL-18) and evaluated its efficiency to prevent an asthma-like reaction in mice. BALB/cByJ mice were sensitized (day (D) 1 and D10) by intraperitoneal injection of ovalbumin (OVA)-alum and primary (D20–22) and secondary (D62, 63) challenged with OVA aerosols. BCG or BCG-IL-18 were intraperitonealy administered 1 hour before each immunization (D1 and D10). BCG-IL-18 and BCG were shown to similarly inhibit the development of AHR, mucus production, eosinophil influx, and local Th2 cytokine production in BAL, both after the primary and secondary challenge. These data show that IL-18 did not increase allergic airway responses in the context of the mycobacterial infection, and suggest that BCG-IL-18 and BCG are able to prevent the development of local Th2 responses and therefore inhibit allergen-induced airway responses even after restimulation.

Recombinant BCG as a vaccine vehicle to protect against tuberculosis

Mycobacterium bovis Bacille Calmette Guérin (BCG) was first administered to humans in 1921 and has subsequently been delivered to an estimated 3 billion individuals, with a low incidence of serious complications. The vaccine is immunogenic and is stable and cheap to produce. Additionally, the vaccine can be engineered to express foreign molecules in a functional form, and this has driven the development of BCG as a recombinant vector to protect against infectious diseases and malignancies such as cancer. However, it is now clear that the existing BCG vaccine has proved insufficient to control the spread of tuberculosis, and a major focus of tuberculosis vaccine development programs is the construction and testing of modified forms of BCG. This review summarizes the strategies employed to develop recombinant forms of BCG and describes the potential of these vaccines to stimulate protective immunity and protect against Mycobacterium tuberculosis infection.

Interleukin-10 inhibits Mycobacterium bovis bacillus Calmette-Guérin (BCG)-induced macrophage cytotoxicity against bladder cancer cells

The mechanisms underlying bacillus Calmette-Guérin (BCG) immunotherapy of bladder cancer currently remain elusive. Previously, we demonstrated that macrophages were cytotoxic to bladder cancer cells upon BCG stimulation in vitro. However, macrophages from C57BL/6 mice were less potent than those from C3H/HeN mice for the killing of bladder cancer cells. This study was to determine whether interleukin (IL)-10 produced by macrophages in response to BCG is a causative factor for the reduced cytotoxicity in BCG-stimulated C57BL/6 macrophages. Thioglycollate-elicited peritoneal macrophages were prepared and analysed for the BCG induction of cytotoxicity, cytokines and nitric oxide (NO) in vitro. Compared to BCG-stimulated C3H/HeN macrophages, BCG-stimulated C57BL/6 macrophages exhibited reduced killing of bladder cancer MBT-2 cells and MB49 cells. Studies demonstrated further that BCG-stimulated C57BL/6 macrophages produced a high level of IL-10, which correlated with reduced production of tumour necrosis factor (TNF)-alpha, IL-6 and NO. Neutralizing endogenous IL-10 during BCG stimulation increased C57BL/6 macrophage cytotoxicity against MB49 cells by 3.2-fold, along with increased production of TNF-alpha by 6.4-fold and NO by 3.6-fold, respectively. Macrophages from C57BL/6 IL-10(-/-) mice also exhibited increased killing of MB49 cells and production of TNF-alpha and NO upon BCG stimulation. In addition, supplementation of exogenous recombinant IL-10 reduced BCG-induced C3H/HeN macrophage cytotoxicity against both MBT-2 cells and MB49 cells in a dose-dependent manner. These results reveal the inhibitory role of IL-10 in BCG-induced macrophage cytotoxicity, suggesting that blockage of IL-10 may potentially enhance the effect of BCG in the treatment of bladder cancer patients.

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.

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.

Promises and challenges for the development of Listeria monocytogenes-based immunotherapies

Active immunotherapy has shown great promise in preclinical models for the treatment of infectious and malignant disease. Yet, these promising results have not translated into approved therapies. One of the major deficits of active immunotherapies tested to date in advanced clinical studies has been their inability to stimulate both arms of the immune system appropriately. The interest in using recombinant bacteria as vaccine vectors for active immunotherapy derives in part from their ability to stimulate multiple innate immune pathways and, at the same time, to deliver antigen for presentation to the adaptive immune system. This review will focus on the development of live-attenuated and killed strains of the intracellular bacterium Listeria monocytogenes for treatment of chronic infections and cancer. Early clinical trials intended to demonstrate safety as well as proof of concept have recently been initiated in several indications. Advances in molecular engineering as well as successes and challenges for clinical development of L. monocytogenes-based vaccines will be discussed.

Celecoxib has potent antitumour effects as a single agent and in combination with BCG immunotherapy in a model of urothelial cell carcinoma

OBJECTIVES

Prostaglandin E2 (PGE2) is a potent immune modulator and known to suppress both tumour antigen-specific helper T (TH1) cells and the generation of cytotoxic T lymphocytes (CTLs). We hypothesised that a combination of the cyclooxygenase 2 (COX-2) selective inhibitor celecoxib and intravesical bacillus Calmette-Guérin (BCG), an effective tumour immunoprophylaxis and ablative therapy for non-muscle-invasive bladder cancer, would be more effective than BCG alone.

METHODS

We assessed urinary levels of PGE2 in humans receiving BCG and in a murine model of urothelial cell carcinoma (UCC). The cytokine response to BCG plus celecoxib was assessed in murine dendritic cells (DCs) in vitro and tumour ablation was assessed in an orthotopic MBT2 murine bladder cancer model.

RESULTS

Administration of intravesical BCG resulted in elevated urinary PGE2 levels in patients with high-grade superficial UCC and in a mouse model of UCC. In vitro, activation of DCs with BCG stimulated COX-2 up-regulation and release of the archetypal tolerogenic factors, PGE2 and interleukin 10. In a superficial mouse model of UCC, combination of celecoxib and intravesical BCG therapy resulted in increased tumour infiltration of CD4+ T cells and improved efficacy when compared to BCG alone. Further, celecoxib demonstrated marked antitumour efficacy when administered in the absence of BCG immunotherapy.

CONCLUSIONS

This study demonstrates that a combination strategy involving BCG immunotherapy and celecoxib may be more therapeutically beneficial than stand-alone intravesical therapy.

Effects of DNA- and Mycobacterium bovis BCG-based delivery of the Flt3 ligand on protective immunity to Mycobacterium tuberculosis

The control of intracellular pathogens such as Mycobacterium tuberculosis is dependent on the activation and maintenance of pathogen-reactive T cells. Dendritic cells (DCs) are the major antigen-presenting cells initiating antimycobacterial T-cell responses in vivo. To investigate if immunization strategies that aim to optimize DC function can improve protective immunity against virulent mycobacterial infection, we exploited the ability of the hematopoietic growth factor Fms-like tyrosine kinase 3 ligand (Flt3L) to expand the number of DCs in vivo. A DNA fusion of the genes encoding murine Flt3L and M. tuberculosis antigen 85B stimulated enhanced gamma interferon (IFN-gamma) release by T cells and provided better protection against virulent M. tuberculosis than DNA encoding the single components. Vaccination of mice with a recombinant Mycobacterium bovis BCG strain secreting Flt3L (BCG:Flt3L) led to early expansion of DCs compared to immunization with BCG alone, and this effect was associated with increased stimulation of BCG-reactive IFN-gamma-secreting T cells. BCG and BCG:Flt3L provided similar protective efficacies against low-dose aerosol M. tuberculosis; however, immunization of immunodeficient mice revealed that BCG:Flt3L was markedly less virulent than conventional BCG. These results demonstrate the potential of in vivo targeting of DCs to improve antimycobacterial vaccine efficacy.

Clinical and experimental approaches to the pathophysiology of interleukin-18 in cancer progression

Interleukin-18 (IL-18, interferon [IFN]-gamma-inducing factor) is a proinflammatory cytokine converted to a biologically active molecule by interleukin (IL)-1beta converting enzyme (caspase-1). A wide range of normal and cancer cell types can produce and respond to IL-18 through a specific receptor (IL-18R) belonging to the toll-like receptor family. The activity of IL-18 is regulated by IL-18-binding protein (IL-18bp), a secreted protein possessing the ability to neutralize IL-18 and whose blood level is affected by renal function and is induced by IFNgamma. IL-18 plays a central role in inflammation and immune response, contributing to the pathogenesis and pathophysiology of infectious and inflammatory diseases. Because immune-stimulating effects of IL-18 have antineoplastic properties, IL-18 has been proposed as a novel adjuvant therapy against cancer. However, IL-18 increases in the blood of the majority of cancer patients and has been associated with disease progression and, in some cancer types, with metastatic recurrence risk and poor clinical outcome and survival. Under experimental conditions, cancer cells can also escape immune recognition, increase their adherence to the microvascular wall and even induce production of angiogenic and tumor growth-stimulating factors via IL-18-dependent mechanism. This is particularly visible in melanoma cells. Thus, the role of IL-18 in cancer progression and metastasis remains controversial. This review examines the clinical correlations and biological effects of IL-18 during cancer development and highlights recent experimental insights into prometastatic and proangiogenic effects of IL-18 and the use of IL-18bp against cancer progression.