SapM mutation to improve the BCG vaccine: Genomic, transcriptomic and preclinical safety characterization.

The Mycobacterium bovis Bacille Calmette Guérin (BCG) vaccine shows variable efficacy in protection against adult tuberculosis (TB). Earlier, we have described a BCG mutant vaccine with a transposon insertion in the gene coding for the secreted acid phosphatase SapM, which led to enhanced long-term survival of vaccinated mice challenged with TB infection. To facilitate development of this mutation as part of a future improved live attenuated TB vaccine, we have now characterized the genome and transcriptome of this sapM::Tn mutant versus parental BCG Pasteur. Furthermore, we show that the sapM::Tn mutant had an equal low pathogenicity as WT BCG upon intravenous administration to immunocompromised SCID mice, passing this important safety test. Subsequently, we investigated the clearance of this improved vaccine strain following vaccination and found a more effective innate immune control over the sapM::Tn vaccine bacteria as compared to WT BCG. This leads to a fast contraction of IFNγ producing Th1 and Tc1 cells after sapM::Tn BCG vaccination. These findings corroborate that a live attenuated vaccine that affords improved long-term survival upon TB infection can be obtained by a mutation that further attenuates BCG. These findings suggest that an analysis of the effectiveness of innate immune control of the vaccine bacteria could be instructive also for other live attenuated TB vaccines that are currently under development, and encourage further studies of SapM mutation as a strategy in developing a more protective live attenuated TB vaccine.

Preclinical development of BCG.HIVA2auxo.int, harboring an integrative expression vector, for a HIV-TB Pediatric vaccine. Enhancement of stability and specific HIV-1 T-cell immunity.

One of the critical issues that should be addressed in the development of a BCG-based HIV vaccine is genetic plasmid stability. Therefore, to address this issue we have considered using integrative vectors and the auxotrophic mutant of BCG complemented with a plasmid carrying a wild-type complementing gene. In this study, we have constructed an integrative E. coli-mycobacterial shuttle plasmid, p2auxo.HIVAint, expressing the HIV-1 clade A immunogen HIVA. This shuttle vector uses an antibiotic resistance-free mechanism for plasmid selection and maintenance. It was first transformed into a glycine auxotrophic E. coli strain and subsequently transformed into a lysine auxotrophic Mycobacterium bovis BCG strain to generate the vaccine BCG.HIVA2auxo.int. Presence of the HIVA gene sequence and protein expression was confirmed. We demonstrated that the in vitro stability of the integrative plasmid p2auxo.HIVAint was increased 4-fold, as compared with the BCG strain harboring the episomal plasmid, and was genetically and phenotypically characterized. The BCG.HIVA2auxo.int vaccine in combination with modified vaccinia virus Ankara (MVA).HIVA was found to be safe and induced HIV-1 and Mycobacterium tuberculosis-specific interferon-γ-producing T-cell responses in adult BALB/c mice. We have engineered a more stable and immunogenic BCG-vectored vaccine using the prototype immunogen HIVA. Thus, the use of integrative expression vectors and the antibiotic-free plasmid selection system based on "double" auxotrophic complementation are likely to improve the mycobacterial vaccine stability in vivo and immunogenicity to develop not only recombinant BCG-based vaccines expressing second generation of HIV-1 immunogens but also other major pediatric pathogens to prime protective responses shortly following birth.

Sleeping Beauty and the Story of the Bacille Calmette-Guérin Vaccine.

Mycobacterium bovis BCG is the only available vaccine for protection against tuberculosis (TB). While BCG protects children from severe disease, it has little impact on pulmonary disease in adults. A recombinant BCG vaccine BCG ΔureC::hly (strain VPM1002) is in advanced clinical trials and shows promise for improved vaccine safety but little change in efficacy in animal models. A second-generation recombinant BCG vaccine with an additional deletion of the nuoG gene (BCG ΔureC::hly ΔnuoG) shows improved efficacy in a mouse model compared to that of VPM1002. BCG was first used in humans in 1921 and, like Sleeping Beauty pricked by the spinning wheel, we have slept for 100 years, showing a reluctance to invest in clinical development or in biomanufacturing capacity for TB vaccines. The advance of recombinant BCGs should awaken us from our sleep and call us to invest in new-generation TB vaccines and to protect the biomanufacture of our current BCG vaccine.

Antiandrogen Therapy with Hydroxyflutamide or Androgen Receptor Degradation Enhancer ASC-J9 Enhances BCG Efficacy to Better Suppress Bladder Cancer Progression.

Recent studies suggest that the androgen receptor (AR) might play important roles in influencing bladder cancer progression, yet its clinical application remains unclear. Here, we developed a new combined therapy with Bacillus Calmette-Guérin (BCG) and the AR degradation enhancer ASC-J9 or antiandrogen hydroxyflutamide (HF) to better suppress bladder cancer progression. Mechanism dissection revealed that ASC-J9 treatment enhanced BCG efficacy to suppress bladder cancer cell proliferation via increasing the recruitment of monocytes/macrophages that involved the promotion of BCG attachment/internalization to the bladder cancer cells through increased integrin-α5ß1 expression and IL6 release. Such consequences might then enhance BCG-induced bladder cancer cell death via increased TNFα release. Interestingly, we also found that ASC-J9 treatment could directly promote BCG-induced HMGB1 release to enhance the BCG cytotoxic effects for suppression of bladder cancer cell growth. In vivo approaches also concluded that ASC-J9 could enhance the efficacy of BCG to better suppress bladder cancer progression in BBN-induced bladder cancer mouse models. Together, these results suggest that the newly developed therapy combining BCG plus ASC-J9 may become a novel therapy to better suppress bladder cancer progress.

Dietary pyridoxine controls efficacy of vitamin B6-auxotrophic tuberculosis vaccine bacillus Calmette-Guérin ΔureC::hly Δpdx1 in mice.

UNLABELLED: The only tuberculosis (TB) vaccine in use today, bacillus Calmette-Guérin (BCG), provides insufficient protection and can cause adverse events in immunocompromised individuals, such as BCGosis in HIV(+) newborns. We previously reported improved preclinical efficacy and safety of the recombinant vaccine candidate BCG ΔureC::hly, which secretes the pore-forming listeriolysin O of Listeria monocytogenes. Here, we evaluate a second-generation construct, BCG ΔureC::hly Δpdx1, which is deficient in pyridoxine synthase, an enzyme that is required for biosynthesis of the essential cofactor vitamin B6. This candidate was auxotrophic for vitamin B6 in a concentration-dependent manner, as was its survival in vivo. BCG ΔureC::hly Δpdx1 showed markedly restricted dissemination in subcutaneously vaccinated mice, which was ameliorated by dietary supplementation with vitamin B6. The construct was safer in severe combined immunodeficiency mice than the parental BCG ΔureC::hly. A prompt innate immune response to vaccination, measured by secretion of interleukin-6, granulocyte colony-stimulating factor, keratinocyte cytokine, and macrophage inflammatory protein-1α, remained independent of vitamin B6 administration, while acquired immunity, notably stimulation of antigen-specific CD4 T cells, B cells, and memory T cells, was contingent on vitamin B6 administration. The early protection provided by BCG ΔureC::hly Δpdx1 in a murine Mycobacterium tuberculosis aerosol challenge model consistently depended on vitamin B6 supplementation. Prime-boost vaccination increased protection against the canonical M. tuberculosis H37Rv laboratory strain and a clinical isolate of the Beijing/W lineage. We demonstrate that the efficacy of a profoundly attenuated recombinant BCG vaccine construct can be modulated by external administration of a small molecule. This principle fosters the development of safer vaccines required for immunocompromised individuals, notably HIV(+) infants. IMPORTANCE: Mycobacterium tuberculosis can synthesize the essential cofactor vitamin B6, while humans depend on dietary supplementation. Unlike the lipophilic vitamins A, D, and E, water-soluble vitamin B6 is well tolerated at high doses. We generated a vitamin B6 auxotroph of the phase II clinical tuberculosis vaccine candidate bacillus Calmette-Guérin ΔureC::hly. The next-generation candidate was profoundly attenuated compared to the parental strain. Adaptive immunity and protection in mice consistently depended on increased dietary vitamin B6 above the daily required dose. Control of vaccine efficacy via food supplements such as vitamin B6 could provide a fast track toward improved safety. Safer vaccines are urgently needed for HIV-infected individuals at high risk of adverse events in response to live vaccines.

Reducing the activity and secretion of microbial antioxidants enhances the immunogenicity of BCG.

BACKGROUND: In early clinical studies, the live tuberculosis vaccine Mycobacterium bovis BCG exhibited 80% protective efficacy against pulmonary tuberculosis (TB). Although BCG still exhibits reliable protection against TB meningitis and miliary TB in early childhood it has become less reliable in protecting against pulmonary TB. During decades of in vitro cultivation BCG not only lost some genes due to deletions of regions of the chromosome but also underwent gene duplication and other mutations resulting in increased antioxidant production. METHODOLOGY/PRINCIPAL FINDINGS: To determine whether microbial antioxidants influence vaccine immunogenicity, we eliminated duplicated alleles encoding the oxidative stress sigma factor SigH in BCG Tice and reduced the activity and secretion of iron co-factored superoxide dismutase. We then used assays of gene expression and flow cytometry with intracellular cytokine staining to compare BCG-specific immune responses in mice after vaccination with BCG Tice or the modified BCG vaccine. Compared to BCG, the modified vaccine induced greater IL-12p40, RANTES, and IL-21 mRNA in the spleens of mice at three days post-immunization, more cytokine-producing CD8+ lymphocytes at the peak of the primary immune response, and more IL-2-producing CD4+ lymphocytes during the memory phase. The modified vaccine also induced stronger secondary CD4+ lymphocyte responses and greater clearance of challenge bacilli. CONCLUSIONS/SIGNIFICANCE: We conclude that antioxidants produced by BCG suppress host immune responses. These findings challenge the hypothesis that the failure of extensively cultivated BCG vaccines to prevent pulmonary tuberculosis is due to over-attenuation and suggest instead a new model in which BCG evolved to produce more immunity-suppressing antioxidants. By targeting these antioxidants it may be possible to restore BCG's ability to protect against pulmonary TB.

Comparison of the construction of unmarked deletion mutations in Mycobacterium smegmatis, Mycobacterium bovis bacillus Calmette-Guérin, and Mycobacterium tuberculosis H37Rv by allelic exchange.

Until recently, genetic analysis of Mycobacterium tuberculosis, the causative agent of tuberculosis, was hindered by a lack of methods for gene disruptions and allelic exchange. Several groups have described different methods for disrupting genes marked with antibiotic resistance determinants in the slow-growing organisms Mycobacterium bovis bacillus Calmette-Guérin (BCG) and M. tuberculosis. In this study, we described the first report of using a mycobacterial suicidal plasmid bearing the counterselectable marker sacB for the allelic exchange of unmarked deletion mutations in the chromosomes of two substrains of M. bovis BCG and M. tuberculosis H37Rv. In addition, our comparison of the recombination frequencies in these two slow-growing species and that of the fast-growing organism Mycobacterium smegmatis suggests that the homologous recombination machinery of the three species is equally efficient. The mutants constructed here have deletions in the lysA gene, encoding meso-diaminopimelate decarboxylase, an enzyme catalyzing the last step in lysine biosynthesis. We observed striking differences in the lysine auxotrophic phenotypes of these three species of mycobacteria. The M. smegmatis mutant can grow on lysine-supplemented defined medium or complex rich medium, while the BCG mutants grow only on lysine-supplemented defined medium and are unable to form colonies on complex rich medium. The M. tuberculosis lysine auxotroph requires 25-fold more lysine on defined medium than do the other mutants and is dependent upon the detergent Tween 80. The mutants described in this work are potential vaccine candidates and can also be used for studies of cell wall biosynthesis and amino acid metabolism.

Potential use of live viral and bacterial vectors for vaccines. WHO meeting, Geneva, 19-22 June, 1989.

The use of vaccinia virus vector for the delivery of antigens was first described by Moss and Paoletti and their colleagues in 1982. Such vaccines could be of particular value in developing countries because they would be cheap, stable, easy to administer and provide long-lasting immunity. WHO recognized the potential value of such a delivery system by convening two meetings, one at the National Institutes of Health, USA in November 1984 and the second at WHO headquarters, Geneva, Switzerland in September 1985, to discuss the possibility of using such products, particularly with regard to their safety. Since that time, other vehicles which could be useful for the delivery of antigens have been described. These include Escherichia coli, Salmonella typhimurium, BCG, all other poxviruses, adenovirus, herpesvirus and poliovirus. At its meeting in July 1988, the Scientific Advisory Group of Experts of the Programme for Vaccine Development (SAGE) concluded that it was appropriate to discuss the general topic of live vectors and proceeded to arrange a meeting to discuss the present position and to prepare a report on the following key issues: requirements for safety and efficacy; immunological factors which may influence efficacy; medical constraints on use. The present report results from a meeting held in Geneva from 19 to 22 June 1989.