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Impact of in vitro evolution on antigenic diversity of Mycobacterium bovis bacillus Calmette-Guerin (BCG).

ABSTRACT: Mycobacterium bovis bacillus Calmette-Guerin (BCG), the only vaccine currently used against tuberculosis, is an attenuated derivative of M. bovis that has been propagated in vitro for more than 40 years. We have previously reported that the experimentally-verified human T cell epitopes of the M. tuberculosis complex (MTBC) are the most conserved elements of the genome; whether immune recognition is the force driving the conservation of epitopes in the MTBC is unknown. Therefore, we sequenced the genomes of 12 BCG strains to determine whether T cell epitopes were under selection pressure during BCG in vitro evolution. We constructed a genome-wide phylogeny and refined the previously-determined BCG phylogeny. Notably, we identified a new cluster between BCG Japan and BCG Russia, and repositioned the relationships of several strains within the lineage. We also compared the sequence diversity of 1530 experimentally verified human T cell epitopes in the BCG vaccines with those in the MTBC. We found 23% of the known T cell epitopes are absent, and that the majority (82%) of the absent epitopes in BCG are contained in 6 proteins encoded in 2 regions of difference (RD) unique to BCG strains. We also found that T cell epitope sequences in BCG are more conserved than non-epitope sequences in the same gene. Finally, we find evidence that epitope sequence variation in BCG potentially affects human T cell recognition. These findings provide new insight into sequence variation in a slow-growing bacterium closely related to the MTBC that has been subjected to prolonged passage outside of a mammalian host, and indicate little difference in the extent of variation in vivo and in vitro.

SUBMITTER: Copin R

PROVIDER: S-EPMC4539939 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Impact of in vitro evolution on antigenic diversity of Mycobacterium bovis bacillus Calmette-Guerin (BCG).

Copin Richard R Coscollá Mireia M Efstathiadis Efstratios E Gagneux Sebastien S Ernst Joel D JD

Vaccine 20140906 45

Mycobacterium bovis bacillus Calmette-Guerin (BCG), the only vaccine currently used against tuberculosis, is an attenuated derivative of M. bovis that has been propagated in vitro for more than 40 years. We have previously reported that the experimentally-verified human T cell epitopes of the M. tuberculosis complex (MTBC) are the most conserved elements of the genome; whether immune recognition is the force driving the conservation of epitopes in the MTBC is unknown. Therefore, we sequenced the ...[more]

PMID: 25211768

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Project description:BackgroundThe Bacillus Calmette-Guerin (BCG) vaccine has been in use for 99 years, and is regarded as one of the oldest human vaccines known today. It is recommended primarily due to its effect in preventing the most severe forms of tuberculosis, including disseminated tuberculosis and meningeal tuberculosis in children; however, its efficacy in preventing pulmonary tuberculosis and TB reactivation in adults has been questioned. Several studies however have found that asides from its role in tuberculosis prevention, the BCG vaccine also has protective effects against a host of other viral infections in humans, an effect which has been termed: heterologous, non-specific or off-target.ObjectivesAs we approach 100 years since the discovery of the BCG vaccine, we review the evidence of the non-specific protection offered by the vaccine against viral infections, discuss the possible mechanisms of action of these effects, highlight the implications these effects could have on vaccinology and summarize the recent epidemiological correlation between the vaccine and the on-going COVID-19 pandemic.ResultsSeveral epidemiological studies have established that BCG does reduce all-cause mortality in infants, and also the time of vaccination influences this effect significantly. This effect has been attributed to the protective effect of the vaccine in preventing unrelated viral infections during the neonatal period. Some of such viral infections that have been investigated include: herpes simplex virus (HSV), human Papilloma virus (HPV), yellow fever virus (YFV), respiratory syncytial virus (RSV) and influenza virus type A (H1N1). These effects are thought to be mediated via induction of innate immune memory as well as heterologous lymphocytic activation. While epidemiological studies have suggested a correlation, the potential protection of the BCG vaccine against COVID-19 transmission and mortality rates is currently unclear. Ongoing clinical trials and further research may shed more light on the subject in the future.ConclusionBCG is a multifaceted vaccine, with many numerous potential applications to vaccination strategies being employed for current and future viral infections. There however is a need for further studies into the immunologic mechanisms behind these non-specific effects, for these potentials to become reality, as we usher in the beginning of the second century since the vaccine's discovery.

Project description:Mycobacterium tuberculosis and Mycobacterium bovis bacille Calmette-Guérin (BCG) alter the maturation of their phagosomes and reside within a compartment that resists acidification and fusion with lysosomes. To define the molecular composition of this compartment, we developed a novel method for obtaining highly purified phagosomes from BCG-infected human macrophages and analyzed the phagosomes by Western immunoblotting and mass spectrometry-based proteomics. Our purification procedure revealed that BCG grown on artificial medium becomes less dense after growth in macrophages. By Western immunoblotting, LAMP-2, Niemann-Pick protein C1, and syntaxin 3 were readily detectable on the BCG phagosome but at levels that were lower than on the latex bead phagosome; flotillin-1 and the vacuolar ATPase were barely detectable on the BCG phagosome but highly enriched on the latex bead phagosome. Immunofluorescence studies confirmed the scarcity of flotillin on BCG phagosomes and demonstrated an inverse correlation between bacterial metabolic activity and flotillin on M. tuberculosis phagosomes. By mass spectrometry, 447 human host proteins were identified on BCG phagosomes, and a partially overlapping set of 289 human proteins on latex bead phagosomes was identified. Interestingly, the majority of the proteins identified consistently on BCG phagosome preparations were also identified on latex bead phagosomes, indicating a high degree of overlap in protein composition of these two compartments. It is likely that many differences in protein composition are quantitative rather than qualitative in nature. Despite the remarkable overlap in protein composition, we consistently identified a number of proteins on the BCG phagosomes that were not identified in any of our latex bead phagosome preparations, including proteins involved in membrane trafficking and signal transduction, such as Ras GTPase-activating-like protein IQGAP1, and proteins of unknown function, such as FAM3C. Our phagosome purification procedure and initial proteomics analyses set the stage for a quantitative comparative analysis of mycobacterial and latex bead phagosome proteomes.

Dataset Information

Impact of in vitro evolution on antigenic diversity of Mycobacterium bovis bacillus Calmette-Guerin (BCG).

Publications

Impact of in vitro evolution on antigenic diversity of Mycobacterium bovis bacillus Calmette-Guerin (BCG).

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