Immunogenicity and protective efficacy conferred by a novel recombinant Mycobacterium bovis bacillus Calmette-Guérin strain expressing interleukin-12p70 of human cytokine and Ag85A of Mycobacterium tuberculosis fusion protein

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.

Advancements in Immunology and Microbiology Research: A Comprehensive Exploration of Key Areas

Immunology and microbiology research has witnessed remarkable growth and innovation globally, playing a pivotal role in advancing our understanding of immune mechanisms, disease pathogenesis, and therapeutic interventions. This manuscript presents a comprehensive exploration of the key areas in immunology research, spanning from the utilisation of bacterial proteins as antibody reagents to the intricate realms of clinical immunology and disease management. The utilisation of bacterial immunoglobulin-binding proteins (IBPs), including protein A (SpA), protein G (SpG), and protein L (SpL), has revolutionised serological diagnostics, showing promise in early disease detection and precision medicine. Microbiological studies have shed light on antimicrobial resistance patterns, particularly the emergence of extended-spectrum beta-lactamases (ESBLs), guiding antimicrobial stewardship programmes and informing therapeutic strategies. Clinical immunology research has elucidated the molecular pathways underlying immune-mediated disorders, resulting in tailored management strategies for conditions such as severe combined immunodeficiency (SCID), neuropsychiatric systemic lupus erythematosus (NPSLE), etc. Additionally, significant efforts in vaccine development against tuberculosis and HIV are highlighted, underscoring the ongoing global pursuit of effective preventive measures against these infectious diseases. In summary, immunology and microbiology research have provided significant contributions to global healthcare, fostering collaboration, innovation, and improved patient outcomes.

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.

Immunogenicity and protective efficacy of recombinant Bacille Calmette-Guerin strains expressing mycobacterium antigens Ag85A, CFP10, ESAT-6, GM-CSF and IL-12p70

OBJECTIVE

This study aimed to evaluate the immunogenicity and protective efficacy of recombinant bacille calmette-guerin (rBCG) strains expressing Ag85A (A), CFP10 (C), ESAT6 (E), IL-12p70 (I), and fusion protein GM-CSF (G).

METHOD

rBCGs were established by integrating of A, C, E, I, G, AE, CE, IE, GC, GE and GCE into Mycobacterium bovis BCG-1173 and BCG-SH. The macro-effects of rBCGs on mice were evaluated by phenotype and weight. The immunogenicity of rBCGs was analyzed by lgG, lgG1 and lgG2a antibody titers, and IFN-γ and IL-4 contents through Enzyme-linked immunosorbent assay (ELISA). Meanwhile, the proportions of CD4⁺ and CD8⁺ T splenic lymphocytes were determined using flow cytometry. The protective efficacy of rBCGs was evaluated by bacterial load in spleen and lung tissues from immunized mice.

RESULTS

rBCGs exhibited no obvious side effects on mice. The antibody titers of lgG, lgG1 and lgG2a, proportion of CD4⁺ and CD8⁺ T cells, and concentrations of IFN-γ were found to be significantly higher in multiple-gene rBCGs than that in single-gene rBCGs (P < 0.05). Bacterial load in both spleen and lung tissues from mice infected with M. tuberculosis H37Rv were significantly reduced by rBCGs. A significantly lower bacterial load was revealed in rBCG-1173:A compared with multiple-gene rBCGs (P < 0.05).

CONCLUSION

Immunogenicity was better on multiple-gene rBCGs than on single-gene rBCGs, while excellent protective efficacy was exhibited on rBCG-1173:A and BCG-1173.