Mapping the global use of different BCG vaccine strains

The contribution of non-conventional T cells and NK cells in the mycobacterial-specific IFNγ response in Bacille Calmette-Guérin (BCG)-immunized infants

BACKGROUND

The Mycobacterium bovis Bacille Calmette-Guérin (BCG) vaccine is given to >120 million infants each year worldwide. Most studies investigating the immune response to BCG have focused on adaptive immunity. However the importance of TCR-gamma/delta (γδ) T cells and NK cells in the mycobacterial-specific immune response is of increasing interest.

METHODS

Participants in four age-groups were BCG-immunized. Ten weeks later, in vitro BCG-stimulated blood was analyzed for NK and T cell markers, and intracellular IFNgamma (IFNγ) by flow cytometry. Total functional IFNγ response was calculated using integrated median fluorescence intensity (iMFI).

RESULTS

In infants and children, CD4 and CD4-CD8- (double-negative (DN)) T cells were the main IFNγ-expressing cells representing 43-56% and 27-37% of total CD3+ IFNγ+ T cells respectively. The iMFI was higher in DN T cells compared to CD4 T cells in all age groups, with the greatest differences seen in infants immunized at birth (p=0.002) or 2 months of age (p<0.0001). When NK cells were included in the analysis, they accounted for the majority of total IFNγ-expressing cells and, together with DN Vδ2 γδ T cells, had the highest iMFI in infants immunized at birth or 2 months of age.

CONCLUSION

In addition to CD4 T cells, NK cells and DN T cells, including Vδ2 γδ T cells, are the key populations producing IFNγ in response to BCG immunization in infants and children. This suggests that innate immunity and unconventional T cells play a greater role in the mycobacterial immune response than previously recognized and should be considered in the design and assessment of novel tuberculosis vaccines.

BCG immunotherapy for bladder cancer--the effects of substrain differences

Genetic mutations have been progressively introduced to BCG by repeated serial passage over many decades of its culture and global dissemination. Thus, marked differences exist in the phenotype, antigenicity, reactogenicity, and clinical characteristics of the numerous substrains of BCG currently in use for bladder cancer immunotherapy. These differences influence proposed mycobacterial antitumour mechanisms and toxicity, potentially resulting in variations in clinical efficacy and adverse effects. However, although there is evidence of substrain-related differences in the clinical efficacy of BCG as a tuberculosis vaccine, evidence of an effect on bladder cancer immunotherapy remains elusive, owing to the lack of appropriately powered head-to-head comparative clinical trials, the nonstandardization of BCG manufacture, and variation in treatment protocols--possibly itself a response to underlying substrain differences. Advances in our understanding of mycobacterial genetics, structure and function, and host-pathogen interactions might explain differences in clinical practice and outcomes. These advances are guiding the identification of biomarkers for reactogenicity and efficacy, and the rational design of immunotherapeutic strategies to eliminate the use of live bacilli for bladder cancer therapy.

BCG vaccine in Korea

The anti-tuberculosis Bacille de Calmette et Guérin (BCG) vaccine was developed between 1905 and 1921 at Pasteur Institutes of Lille in France, and was adopted by many countries. BCG strains comprise natural mutants of major virulence factors of Mycobacterium tuberculosis and that BCG sub-strains differ markedly in virulence levels. The tuberculosis became endemic in Korea after the Korean War (1950s). The BCG strain, which was donated by Pasteur Institutes, was brought to Korea in 1955, and the first domestic BCG vaccine was produced by the National Defense Research Institute (NDRI), current Korea Centers for Disease Control and Prevention (KCDC), in 1960. Since 1987, BCG manufacture work was handed over to the Korean Institute of Tuberculosis (KIT), the freeze-dried BCG vaccine was manufactured at a scale required to meet the whole amount of domestic consumption. However, since 2006, the manufacture of BCG vaccine suspended and the whole amount of BCG was imported at this point of time. Now KIT is planning to re-produce the BCG vaccine in Korea under the supervision of KCDC, this will be render great role to National Tuberculosis Control Program (NTP) and provide initiating step for developing new tuberculosis vaccines in Korea.

Targeting essential cell wall lipase Rv3802c for potential therapeutics against tuberculosis

Cell wall and lipid metabolism plays a vital role in the survival and infection of Mycobacterium tuberculosis. Increase in the incidences of life-threatening multidrug-resistant (MDR) and extreme drug-resistant (XDR) tuberculosis worsens the existing scenario and urge the need of new druggable targets and new drugs. Targeting Rv3802c, an essential cell wall lipase, can open up a new arsenal to fight the dreadful opportunistic pathogen. Our current study highlights the essentiality of Rv3802c. Its 3D structure is predicted for the first time which provides insight in identifying the ligand binding sites. Our analysis showed Rv3802c is highly conserved throughout mycobacterial species with no significant sequence homolog found in human proteome. Virtual screening followed by comparative docking studies of Rv3802c with its closest human structural homolog has been carried out to identify potential inhibitors effective towards mycobacterial proteins. Two diverse molecules from ZINC database, ZINC26726377 and ZINC43866786 have been identified as potential inhibitors effective towards Rv3802c based on the difference in predicted binding free energy of -3.99 and -3.28kcal/mol respectively. Rv3802c is a promising drug target and also a step towards understanding and targeting the pathogen's cell wall and lipid metabolism simultaneously to combat tuberculosis.

Genome-wide association studies of tuberculosis in Asians identify distinct at-risk locus for young tuberculosis

Tuberculosis (TB) is one of the most devastating chronic infectious diseases, but the role of host genetics in disease development after infection in this disease remains unidentified. Genome-wide association studies (GWASs) in Thais and Japanese were carried out and separately analyzed, attempted replication, then, combined by meta-analysis were not yielding any convincing association evidences; these results suggested that moderate to high effect-size genetic risks are not existed for TB per se. Because of failure in replication attempt of the top 50 single-nucleotide polymorphisms (SNPs) identified form meta-analysis data, we empirically split TB cases into young TB case/control data sets (GWAS-T(young)=137/295 and GWAS-J(young)=60/249) and old TB case/control data sets (GWAS-T(old)=300/295 and GWAS-J(old)=123/685), re-analyzed GWAS based on age-stratified data and replicated the significant findings in two independent replication samples (young TB; Rep-T(young)=155/249, Rep-J(young)=41/462 and old TB; Rep-T(old)=212/187, Rep-J(old)=71/619). GWAS and replication studies conducted in young TB identified at-risk locus in 20q12. Although the locus is located in inter-genic region, the nearest genes (HSPEP1-MAFB) from this locus are promising candidates for TB susceptibility. This locus was also associated with anti-TNF responsiveness, drug with increased susceptibility for TB. Moreover, eight SNPs in an old TB meta-analysis and six SNPs in young TB meta-analysis provided replication evidences but did not survive genome-wide significance.These findings suggest that host genetic risks for TB are affected by age at onset of TB, and this approach may accelerate the identification of the major host factors that affect TB in human populations.

The influence of BCG vaccine strain on mycobacteria-specific and non-specific immune responses in a prospective cohort of infants in Uganda

BACKGROUND

Globally, BCG vaccination varies in efficacy and has some non-specific protective effects. Previous studies comparing BCG strains have been small-scale, with few or no immunological outcomes and have compared TB-specific responses only. We aimed to evaluate both specific and non-specific immune responses to different strains of BCG within a large infant cohort and to evaluate further the relationship between BCG strain, scarring and cytokine responses.

METHODS

Infants from the Entebbe Mother and Baby Study (ISRCTN32849447) who received BCG-Russia, BCG-Bulgaria or BCG-Denmark at birth, were analysed by BCG strain group. At one year, interferon-gamma (IFN-γ), interleukin (IL)-5, IL-13 and IL-10 responses to mycobacteria-specific antigens (crude culture filtrate proteins and antigen 85) and non-mycobacterial stimuli (tetanus toxoid and phytohaemagglutinin) were measured using ELISA. Cytokine responses, scar frequency, BCG associated adverse event frequency and mortality rates were compared across groups, with adjustments for potential confounders.

RESULTS

Both specific and non-specific IFN-γ, IL-13 and IL-10 responses in 1341 infants differed between BCG strain groups including in response to stimulation with tetanus toxoid. BCG-Denmark immunised infants showed the highest cytokine responses. The proportion of infants who scarred differed significantly, with BCG scars occurring in 52.2%, 64.1% and 92.6% of infants immunised with BCG Russia, BCG-Bulgaria and BCG-Denmark, respectively (p<0.001). Scarred infants had higher IFN-γ and IL-13 responses to mycobacterial antigens only than infants without a scar. The BCG-Denmark group had the highest frequency of adverse events (p=0.025). Mortality differences were not significant.

CONCLUSIONS

Both specific and non-specific immune responses to the BCG vaccine differ by strain. Scarring after BCG vaccination is also strain-dependent and is associated with higher IFN-γ and IL-13 responses to mycobacterial antigens. The choice of BCG strain may be an important factor and should be evaluated when testing novel vaccine strategies that employ BCG in prime-boost sequences, or as a vector for other vaccine antigens.

In vitro culture medium influences the vaccine efficacy of Mycobacterium bovis BCG

The varied rates of protection induced by Mycobacterium bovis BCG vaccine against tuberculosis has been attributed to many factors such as genetic variability among BCG strains, rapid clearance of BCG in some populations, and different levels of previous exposure of vaccinated populations to environmental mycobacteria. However, the methods and conditions employed to prepare this vaccine for human usage by various manufacturers have not been investigated as potential factors contributing to the variation in vaccine efficacy. A review of the literature indicates discrepancies between the approach for growing BCG vaccine in the laboratory to assess immune responses and protective ability in animal models, and that employed for production of the vaccine for administration to humans. One of the major differences is in the growth medium used for routine propagation in the laboratory and the one used for bulk vaccine production by manufacturers. Here we compared the immunogenicity of the BCG vaccine grown in Middlebrook 7H9 medium, the most commonly used medium in laboratory studies, against that grown in Sauton medium, which is used for growing BCG by most manufacturers. Our results showed clear differences in the behavior of BCG grown in these different culture media. Compared to BCG grown in Middlebrook 7H9 medium, BCG grown in Sauton media was more persistent inside macrophages, more effective at inhibiting apoptosis of infected cells, induced stronger inflammatory responses and stimulated less effective immunity against aerosol challenge with a virulent Mtb strain. These findings suggested that the growth medium used for producing BCG vaccine is an important factor that deserves increased scrutiny in ongoing efforts to produce more consistently effective vaccines against Mtb.

Proteomic profile of culture filtrate from the Brazilian vaccine strain Mycobacterium bovis BCG Moreau compared to M. bovis BCG Pasteur

Background

Bacille Calmette-Guerin (BCG) is currently the only available vaccine against tuberculosis (TB) and comprises a heterogeneous family of sub-strains with genotypic and phenotypic differences. The World Health Organization (WHO) affirms that the characterization of BCG sub-strains, both on genomic and proteomic levels, is crucial for a better comprehension of the vaccine. In addition, these studies can contribute in the development of a more efficient vaccine against TB. Here, we combine two-dimensional electrophoresis (2DE) and mass spectrometry to analyse the proteomic profile of culture filtrate proteins (CFPs) from M. bovis BCG Moreau, the Brazilian vaccine strain, comparing it to that of BCG Pasteur. CFPs are considered of great importance given their dominant immunogenicity and role in pathogenesis, being available for interaction with host cells since early infection.

Results

The 2DE proteomic map of M. bovis BCG Moreau CFPs in the pH range 3 - 8 allowed the identification of 158 spots corresponding to 101 different proteins, identified by MS/MS. Comparison to BCG Pasteur highlights the great similarity between these BCG strains. However, quantitative analysis shows a higher expression of immunogenic proteins such as Rv1860 (BCG1896, Apa), Rv1926c (BCG1965c, Mpb63) and Rv1886c (BCG1923c, Ag85B) in BCG Moreau when compared to BCG Pasteur, while some heat shock proteins, such as Rv0440 (BCG0479, GroEL2) and Rv0350 (BCG0389, DnaK), show the opposite pattern.

Conclusions

Here we report the detailed 2DE profile of CFPs from M. bovis BCG Moreau and its comparison to BCG Pasteur, identifying differences that may provide relevant information on vaccine efficacy. These findings contribute to the detailed characterization of the Brazilian vaccine strain against TB, revealing aspects that may lead to a better understanding of the factors leading to BCG's variable protective efficacy against TB.

The BCG World Atlas: a database of global BCG vaccination policies and practices

Madhu Pai and colleagues introduce the BCG World Atlas, an open access, user friendly Web site for TB clinicians to discern global BCG vaccination policies and practices and improve the care of their patients.