The Experts below are selected from a list of 12345 Experts worldwide ranked by ideXlab platform
Stewart T Cole - One of the best experts on this subject based on the ideXlab platform.
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differential effects of prior exposure to environmental mycobacteria on vaccination with Mycobacterium Bovis BCG or a recombinant BCG strain expressing rd1 antigens
2005Co-Authors: Caroline Demangel, Thierry Garnier, Ida Rosenkrands, Stewart T ColeAbstract:In silico analysis reveals that most protective antigens expressed by the antituberculous vaccine Mycobacterium Bovis BCG (BCG) are conserved in M. avium, supporting the hypothesis that exposure to environmental mycobacteria generates cross-reactive immune responses blocking BCG activity. We investigated the impact of sensitization with M. avium, M. scrofulaceum, or M. vaccae on the protective efficacy of a recombinant BCG strain expressing RD1 antigens (BCG::RD1), using a mouse model of experimental tuberculosis (TB). No evidence that the RD1-encoded antigens ESAT-6, CFP-10, and PPE68 were expressed by these environmental strains could be demonstrated by Western blot analysis. Mice sensitized with each of these strains did not prime cellular immune responses cross-reacting with the immunodominant ESAT-6. Importantly, clearance of BCG::RD1 from the lungs and spleens of mice exposed to each of the environmental strains before vaccination was minimal compared to that of BCG. In mice sensitized with M. avium, increased persistence of BCG::RD1 correlated with stronger antimycobacterial gamma interferon responses and enhanced protection against aerosol infection with M. tuberculosis, compared to BCG. In contrast, animals exposed to M. scrofulaceum or M. vaccae prior to vaccination with BCG or BCG::RD1 were better protected against TB than were the unsensitized controls. Our results suggest that the inhibitory effect of environmental mycobacteria on the protective efficacy of BCG depends critically on the extent of cross-recognition of antigens shared with the vaccine. In hosts sensitized with M. avium, potent immunogenicity of ESAT-6 and increased persistence of BCG::RD1 may allow this recombinant vaccine to overcome preexisting antimycobacterial responses.
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loss of rd1 contributed to the attenuation of the live tuberculosis vaccines Mycobacterium Bovis BCG and Mycobacterium microti
2002Co-Authors: Priscille Brodin, Michel Huerre, Stewart T ColeAbstract:Although large human populations have been safely immunized against tuberculosis with two live vaccines, Mycobacterium Bovis BCG or Mycobacterium microti, the vole bacillus, the molecular basis for the avirulence of these vaccine strains remains unknown. Comparative genomics has identified a series of chromosomal deletions common to both virulent and avirulent species but only a single locus, RD1, that has been deleted from M. Bovis BCG and M. microti. Restoration of RD1, by gene knock-in, resulted in a marked change in colonial morphology towards that of virulent tubercle bacilli. Three RD1-encoded proteins were localized in the cell wall, and two of them, the immunodominant T-cell antigens ESAT-6 and CFP-10, were also found in culture supernatants. The BCG::RD1 and M. microti::RD1 knock-ins grew more vigorously than controls in immunodeficient mice, inducing extensive splenomegaly and granuloma formation. Increased persistence and partial reversal of attenuation were observed when immunocompetent mice were infected with the BCG::RD1 knock-in, whereas BCG controls were cleared. Knocking-in five other RD loci did not affect the virulence of BCG. This study describes a genetic lesion that contributes to safety and opens new avenues for vaccine development.
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comparative genomics uncovers large tandem chromosomal duplications in Mycobacterium Bovis BCG pasteur
2000Co-Authors: Roland Brosch, Stephen V Gordon, Carmen Buchrieser, Alexander S Pym, Thierry Garnier, Stewart T ColeAbstract:On direct comparison of minimal sets of ordered clones from bacterial artificial chromosome (BAC) libraries representing the complete genomes of Mycobacterium tuberculosis H37Rv and the vaccine strain, Mycobacterium Bovis BCG Pasteur, two major rearrangements were identified in the genome of M. Bovis BCG Pasteur. These were shown to correspond to two tandem duplications, DU1 and DU2, of 29 668 bp and 36 161 bp, respectively. While DU1 resulted from a single duplication event, DU2 apparently arose from duplication of a 100 kb genomic segment that subsequently incurred an internal deletion of 64 kb. Several lines of evidence suggest that DU2 may continue to expand, since two copies were detected in a subpopulation of BCG Pasteur cells. BCG strains harbouring DU1 and DU2 are diploid for at least 58 genes and contain two copies of oriC, the chromosomal origin of replication. These findings indicate that these genomic regions of the BCG genome are still dynamic. Although the role of DU1 and DU2 in the attenuation and/or altered immunogenicity of BCG is yet unknown, knowledge of their existence will facilitate quality control of BCG vaccine lots and may help in monitoring the efficacy of the world's most widely used vaccine.
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physical mapping of Mycobacterium Bovis BCG pasteur reveals differences from the genome map of Mycobacterium tuberculosis h37rv and from m Bovis
1996Co-Authors: Wolfgang J Philipp, Shamila Nair, Gerard Guglielmi, Micheline Lagranderie, Brigitte Gicquel, Stewart T ColeAbstract:A Dral restriction map of the approximately 4.35 Mb circular chromosome of the vaccine strain Mycobacterium Bovis BCG Pasteur was constructed by linking all 21 Dral fragments, ranging in size from 6 to 820 kb, using specific clones that spanned the Dral recognition sites as hybridization probes. The positions of 20 known genes were also established. Comparison of the resultant genome map with that of the virulent tubercle bacillus Mycobacterium tuberculosis H37Rv revealed extensive global conservation of the genomes of these two members of the M. tuberculosis complex. Possible sites of evolutionary rearrangements were localized on the chromosome of M. Bovis BCG Pasteur by comparing the Asnl restriction profile with that of M. tuberculosis H37Rv. When selected cosmids from the corresponding areas of the genome of M. tuberculosis H37Rv were used as hybridization probes to examine different BCG strains, wild-type M. Bovis and M. tuberculosis H37Rv, a number of deletions up to 10 kb in size, insertions and other polymorphisms were detected. In addition to the known deletions covering the genes for the protein antigens ESAT-6 and mpt64, other genetic loci exhibiting polymorphisms or rearrangements were detected in M. Bovis BCG Pasteur.
Nathalie Winter - One of the best experts on this subject based on the ideXlab platform.
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Mycobacterium Bovis BCG-infected neutrophils and dendritic cells cooperate to induce specific T cell responses in humans and mice
2008Co-Authors: Celine Morel, Brigitte Gicquel, Edgar Badell, Valérie Abadie, Macarena Robledo, Nicolas Setterblad, Jean Claude Gluckman, Sarah Boudaly, Nathalie WinterAbstract:Neutrophils are increasingly thought to modulate dendritic cell (DC) functions. We investigated the role of the neutrophil-DC partnership in the response to Mycobacterium Bovis BCG-the vaccine used against tuberculosis. We compared neutrophil-DC crosstalk in humans and mice, searching for functional differences. In both species, neutrophils captured fluorescent BCG-enhanced green fluorescent protein (EGFP) and were more phagocytic than DC. Non-apoptotic BCG-infected neutrophils clustered with immature DC, establishing intimate contacts with dendrites, at which fluorescent intact bacilli were observed. Physical interactions between neutrophils and DC were required for DC activation. Human BCG-infected DC produced interleukin (IL)-10, an inhibitory cytokine, whereas DC exposed to BCG-infected neutrophils produced low to undetectable amounts of the cytokine. Mouse BCG-infected neutrophils induced sustained IL-2 production by DC. Human DC exposed to BCG-infected neutrophils stimulated recall T cell reactivity from vaccinated donors. Mouse DC infected with recombinant ovalburnin (OVA)-producing BCG (rBCG(ova)) elicited proliferation of TCR-OVA-transgenic CD4 and CD8 T cells. Moreover, exposing DC to rBCG(ova)-infected neutrophils enhanced OVA presentation. Thus, in mice and humans, neutrophils help DC to cross-present BCG antigens to T cells. Our results suggest that this "menage a trois" involving neutrophils, DC and T cells plays a major role in the immune response to BCG.
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Recombinant Mycobacterium Bovis BCG expressing the Sm14 antigen of Schistosoma mansoni protects mice from cercarial challenge
2004Co-Authors: Paula B. Varaldo, Liciana C.c. Leite, Waldely O. Dias, Eliane N. Miyaji, Fabio I.g. Torres, Vera C. Gebara, Geraldo R.g. Armoa, Adriano S. Campos, Denise C.s. Matos, Nathalie WinterAbstract:The Sm14 antigen of Schistosoma mansoni was cloned and expressed in Mycobacterium Bovis BCG as a fusion with the Mycobacterium fortuitum P-lactamase protein under the control of its promoter, pBlaF*; the protein was localized in the bacterial cell wall. The rBCG-Sm14 strain was shown to be relatively stable in cultured murine and bovine monocytes in terms of infectivity, bacterial persistence, and plasmid stability. The immunization of mice with rBCG-Sm14 showed no induction of anti-Sm14 antibodies; however, splenocytes of immunized mice released increased levels of gamma interferon upon stimulation with recombinant Sm14 (rSm14), indicating an induction of a Th1-predominant cellular response against Sm14. Mice immunized with one or two doses of rBCG-Sm14 and challenged with live S. mansoni cercaria showed a 48% reduction in worm burden, which was comparable to that obtained by immunization with three doses of rSm14 purified from Escherichia coli. The data presented here further enhance the status of Sm14 as a promising candidate antigen for the control of schistosomiasis and indicate that a one-dose regimen of rBCG-Sm14 could be considered a convenient means to overcome many of the practical problems associated with the successful implementation of a multiple-dose vaccine schedule in developing countries.
Adrian V S Hill - One of the best experts on this subject based on the ideXlab platform.
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boosting with poxviruses enhances Mycobacterium Bovis BCG efficacy against tuberculosis in guinea pigs
2005Co-Authors: Alison Williams, N P Goonetilleke, Helen Mcshane, Simon Clark, Graham J Hatch, Sarah C Gilbert, Adrian V S HillAbstract:Tuberculosis is rising in the developing world due to poor health care, human immunodeficiency virus type 1 infection, and the low protective efficacy of the Mycobacterium Bovis BCG vaccine. A new vaccination strategy that could protect adults in the developing world from tuberculosis could have a huge impact on public health. We show that BCG boosted by poxviruses expressing antigen 85A induced unprecedented 100% protection of guinea pigs from high-dose aerosol challenge with Mycobacterium tuberculosis, suggesting a strategy for enhancing and prolonging the efficacy of BCG.
Peter Sander - One of the best experts on this subject based on the ideXlab platform.
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deletion of zmp1 improves Mycobacterium Bovis BCG mediated protection in a guinea pig model of tuberculosis
2015Co-Authors: Peter Sander, Simon Clark, Agnese Petrera, Cristina Vilaplana, Michael Meuli, Petra Selchow, Andrea Zelmer, Deepa Mohanan, Nuria Andreu, Emma RaynerAbstract:Having demonstrated previously that deletion of zinc metalloprotease zmp1 in Mycobacterium Bovis BCG increased immunogenicity of BCG vaccines, we here investigated the protective efficacy of BCG zmp1 deletion mutants in a guinea pig model of tuberculosis infection. zmp1 deletion mutants of BCG provided enhanced protection by reducing the bacterial load of tubercle bacilli in the lungs of infected guinea pigs. The increased efficacy of BCG due to zmp1 deletion was demonstrated in both BCG Pasteur and BCG Denmark indicating that the improved protection by zmp1 deletion is independent from the BCG sub-strain. In addition, unmarked BCG Δzmp1 mutant strains showed a better safety profile in a CB-17 SCID mouse survival model than the parental BCG strains. Together, these results support the further development of BCG Δzmp1 for use in clinical trials.
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Mycobacterium Bovis BCG reca deletion mutant shows increased susceptibility to dna damaging agents but wild type survival in a mouse infection model
2001Co-Authors: Thomas Dick, Peter Sander, K G Papavinasasundaram, Evangelos Stavropoulos, Kerstin Ellrott, B Springer, Joseph M Colston, Erik C BottgerAbstract:Pathogenic microorganisms possess antioxidant defense mechanisms for protection from reactive oxygen metabolites which are generated during the respiratory burst of phagocytic cells. These defense mechanisms include enzymes such as catalase, which detoxifies reactive oxygen species, and DNA repair systems, which repair damage resulting from oxidative stress. To (i) determine the relative importance of the DNA repair system when oxidative stress is encountered by the Mycobacterium tuberculosis complex during infection of the host and to (ii) provide improved mycobacterial hosts as live carriers to express foreign antigens, the recA locus was inactivated by allelic exchange in Mycobacterium Bovis BCG. The recA mutants are sensitive to DNA-damaging agents and show increased susceptibility to metronidazole, the first lead compound active against the dormant M. tuberculosis complex. Surprisingly, the recA genotype does not affect the in vitro dormancy response, nor does the defect in the DNA repair system lead to attenuation as determined in a mouse infection model. The recA mutants will be a valuable tool for further development of BCG as an antigen delivery system to express foreign antigens and as a source of a genetically stable vaccine against tuberculosis.
William R. Jacobs - One of the best experts on this subject based on the ideXlab platform.
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priming with a recombinant pantothenate auxotroph of Mycobacterium Bovis BCG and boosting with mva elicits hiv 1 gag specific cd8 t cells
2012Co-Authors: Rosamund Chapman, William R. Jacobs, Enid G Shephard, Helen Stutz, Nicola Douglass, Vasan K Sambandamurthy, Irene Garcia, Bernhard Ryffel, Annalise WilliamsonAbstract:A safe and effective HIV vaccine is required to significantly reduce the number of people becoming infected with HIV each year. In this study wild type Mycobacterium Bovis BCG Pasteur and an attenuated pantothenate auxotroph strain (BCGΔpanCD) that is safe in SCID mice, have been compared as vaccine vectors for HIV-1 subtype C Gag. Genetically stable vaccines BCG[pHS400] (BCG-Gag) and BCGΔpanCD[pHS400] (BCGpan-Gag) were generated using the Pasteur strain of BCG, and a panothenate auxotroph of Pasteur respectively. Stability was achieved by the use of a codon optimised gag gene and deletion of the hsp60-lysA promoter-gene cassette from the episomal vector pCB119. In this vector expression of gag is driven by the mtrA promoter and the Gag protein is fused to the Mycobacterium tuberculosis 19 kDa signal sequence. Both BCG-Gag and BCGpan-Gag primed the immune system of BALB/c mice for a boost with a recombinant modified vaccinia virus Ankara expressing Gag (MVA-Gag). After the boost high frequencies of predominantly Gag-specific CD8+ T cells were detected when BCGpan-Gag was the prime in contrast to induction of predominantly Gag-specific CD4+ T cells when priming with BCG-Gag. The differing Gag-specific T-cell phenotype elicited by the prime-boost regimens may be related to the reduced inflammation observed with the pantothenate auxotroph strain compared to the parent strain. These features make BCGpan-Gag a more desirable HIV vaccine candidate than BCG-Gag. Although no Gag-specific cells could be detected after vaccination of BALB/c mice with either recombinant BCG vaccine alone, BCGpan-Gag protected mice against a surrogate vaccinia virus challenge.
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recombinant Mycobacterium Bovis BCG prime recombinant adenovirus boost vaccination in rhesus monkeys elicits robust polyfunctional simian immunodeficiency virus specific t cell responses
2009Co-Authors: Mark Cayabyab, Birgit Koriothschmitz, Yue Sun, Angela Carville, Harikrishnan Balachandran, Ayako Miura, Kevin R Carlson, Adam P Buzby, Barton F Haynes, William R. JacobsAbstract: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 106 to 108 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.
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protection elicited by two glutamine auxotrophs of Mycobacterium tuberculosis and in vivo growth phenotypes of the four unique glutamine synthetase mutants in a murine model
2006Co-Authors: Sunhee Lee, Bo Young Jeon, Sheldon L Morris, Svetoslav Bardarov, Mei Chen, William R. JacobsAbstract:We generated four individual glutamine synthetase (GS) mutants (ΔglnA1, ΔglnA2, ΔglnA3, and ΔglnA4) and one triple mutant (ΔglnA1EA2) of Mycobacterium tuberculosis to investigate the roles of GS enzymes. Subcutaneous immunization with the ΔglnA1EA2 and ΔglnA1 glutamine auxotrophic mutants conferred protection on C57BL/6 mice against an aerosol challenge with virulent M. tuberculosis, which was comparable to that provided by Mycobacterium Bovis BCG vaccination.
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in vivo growth characteristics of leucine and methionine auxotrophic mutants of Mycobacterium Bovis BCG generated by transposon mutagenesis
1995Co-Authors: R A Mcadam, Torin R Weisbrod, Jennifer L Martin, J D Scuderi, Amanda M Brown, Jeffrey D Cirillo, Barry R Bloom, William R. JacobsAbstract:Insertional mutagenesis in Mycobacterium Bovis BCG, a member of the slow-growing M. tuberculosis complex, was accomplished with transposons engineered from the Mycobacterium smegmatis insertion element IS1096. Transposons were created by placing a kanamycin resistance gene in several different positions in IS1096, and the resulting transposons were electroporated into BCG on nonreplicating plasmids. These analyses demonstrated that only one of the two open reading frames was necessary for transposition. A library of insertions was generated. Southern analysis of 23 kanamycin-resistant clones revealed that the transposons had inserted directly, with no evidence of cointegrate formation, into different restriction fragments in each clone. Sequence analysis of nine of the clones revealed junctional direct 8-bp repeats with only a slight similarity in target sites. These results suggest that IS1096-derived transposons transposed into the BCG genome in a relatively random fashion. Three auxotrophs, two for leucine and one for methionine, were isolated from the library of transposon insertions in BCG. They were characterized by sequencing and found to be homologous to the leuD gene of Escherichia coli and a sulfate-binding protein of cyanobacteria, respectively. When inoculated intravenously into C57BL/6 mice, the leucine auxotrophs, in contrast to the parent BCG strain or the methionine auxotroph, showed an inability to grow in vivo and were cleared within 7 weeks from the lungs and spleen.
