Report on a WHO Consultation on the characterisation of BCG strains, Imperial College, London 15–16 December 2003

Genome sequences of BCG Pasteur ATCC 35734 and its derivative, the vaccine candidate BCGΔBCG1419c

BACKGROUND

Bacillus Calmette-Guérin (BCG) remains the only vaccine to prevent tuberculosis (TB) during childhood, with relatively low to no efficacy against pulmonary TB in adolescents and adults. BCG consists of close to 15 different substrains, where genetic variations among them might contribute to the variable protective efficacy afforded against pulmonary TB. We have shown that the vaccine candidate, BCGΔBCG1419c, which is based on BCG Pasteur, improved protection against chronic TB in murine models, as well as against pulmonary and extrapulmonary TB in guinea pigs. Here, to confirm deletion of the BCG1419c gene and to detect possible genetic variations occurring as a consequence of the spontaneous mutations that may arise during in vitro culture of mycobacteria, the genomes of BCG Pasteur ATCC 35734 and its isogenic derivative, BCGΔBCG1419c, were sequenced and subjected to a comparative analysis between them and against BCG Pasteur 1173P2.

RESULTS

The complete catalog of variants in genes relative to the reference genome BCG Pasteur 1173P2 (GenBank NC008769) showed that the parental strain BCG Pasteur ATCC 35734, from which the mutant BCGΔBCG1419c originated, showed five synonymous mutations, three missense mutations, and five codon insertions, whereas the BCGΔBCG1419c mutant reported the same changes. When BCG Pasteur ATCC 35734 and BCGΔBCG1419c were compared, we confirmed that the latter was devoid of the BCG1419c gene, with only one unanticipated SNP at position 2, 828, 791  which we consider has no role in vaccine properties reported thus far.

CONCLUSION

We provide evidence that the mutagenesis performed to remove BCG1419c from BCG Pasteur ATCC 35734 solely deleted this gene, and that compared with the reference strain BCG Pasteur 1173P2, few changes were present confirming that they are BCG Pasteur strains, and that changes in immunogenicity or efficacy observed thus far in BCGΔBCG1419c are most likely derived solely from the elimination of the BCG1419c gene.

BCG-Based Vaccines Elicit Antigen-Specific Adaptive and Trained Immunity against SARS-CoV-2 and Andes orthohantavirus

Background:Mycobacterium bovis Bacillus Calmette-Guérin (BCG) is a live attenuated vaccine mainly administered to newborns and used for over 100 years to prevent the disease caused by Mycobacterium tuberculosis (M. tb). This vaccine can induce immune response polarization towards a Th1 profile, which is desired for counteracting M. tb, other mycobacteria, and unrelated intracellular pathogens. The vaccine BCG has been used as a vector to express recombinant proteins and has been shown to protect against several diseases, particularly respiratory viruses. Methods: BCG was used to develop recombinant vaccines expressing either the Nucleoprotein from SARS-CoV-2 or Andes orthohantavirus. Mice were immunized with these vaccines with the aim of evaluating the safety and immunogenicity parameters. Results: Immunization with two doses of 1 × 10⁸ CFU or one dose of 1 × 10⁵ CFU of these BCGs was safe in mice. A statistically significant cellular immune response was induced by both formulations, characterized as the activation of CD4⁺ and CD8⁺ T cells. Stimulation with unrelated antigens resulted in increased expression of activation markers by T cells and secretion of IL-2 and IFN-γ, while increased secretion of IL-6 was found for both recombinant vaccines; all of these parameters related to a trained immunity profile. The humoral immune response elicited by both vaccines was modest, but further exposure to antigens could increase this response. Conclusions: The BCG vaccine is a promising platform for developing vaccines against different pathogens, inducing a marked antigen-specific immune response.

An Update on Tuberculosis Vaccines

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a leading cause of mortality and morbidity due to a single infectious agent. Aerosol infection with Mtb can result in a range of responses from elimination, active, incipient, subclinical, and latent Mtb infections (LTBI), depending on the host's immune response and the dose and nature of infecting bacilli. Currently, BCG is the only vaccine approved to prevent TB. Although BCG confers protection against severe forms of childhood TB, its use in adults and those with comorbid conditions, such as HIV infection, is questionable. Novel vaccines, including recombinant BCG (rBCG), were developed to improve BCG's efficacy and use as an alternative to BCG in a vulnerable population. The first-generation rBCG vaccines had different Mtb antigens and were tested as a prime, prime-boost, or immunotherapeutic intervention. The novel vaccines target one or more of the following requirements, namely prevention of infection (POI), prevention of disease (POD), prevention of recurrence (POR), and therapeutic vaccines to treat a TB disease. Several vaccine candidates currently in development are classified into four primary categories: live attenuated whole-cell vaccine, inactivated whole-cell vaccine, adjuvanted protein subunit vaccine, and viral-vectored vaccine. Each vaccine's immunogenicity, safety, and efficacy are tested in preclinical animal models and further validated through various phases of clinical trials. This chapter summarizes the various TB vaccine candidates under different clinical trial stages and promises better protection against TB.

Management of Bacille Calmette-Guérin Lymphadenitis and Abscess in Immunocompetent Children: A Systematic Review

BACKGROUND

There is no consensus on managing common adverse reactions to Bacille Calmette-Guérin (BCG) vaccination. We systematically reviewed the management of BCG-associated regional lymphadenitis and injection site abscess in immunocompetent individuals.

METHODS

Searches of Medline, Embase and PubMed were done until November 2020. Randomized controlled trials (RCTs) and cohort studies that compared management strategies for complications of intradermal BCG vaccination were included.

RESULTS

Of 1338 individual articles, 15 met inclusion criteria. Six RCTs, 4 prospective and 4 retrospective cohort studies compared management in 1022 children with BCG-associated lymphadenitis. For nonsuppurative lymphadenitis, no antimicrobial was found to significantly impact on time to resolution or prevention of suppuration. For suppurative lymphadenitis, there was some evidence that needle aspiration shortens time to resolution and prevents sinus tract formation. Surgical excision (mainly offered for persistent suppurative lymphadenitis) generally had favorable outcome. Two cohort studies (including 1 aforementioned) compared management strategies in up to 36 children with BCG injection site abscess; one showed no difference in outcome in children treated with antibiotics and the other reported complete resolution without treatment.

CONCLUSIONS

Evidence does not support a role for antimicrobial therapy in the management of localized reactions to BCG vaccination in immunocompetent children. Needle aspiration may shorten the recovery period for BCG-associated suppurative lymphadenitis. BCG injection site abscess usually heals without treatment. However, studies are limited and cases are not well defined. Growing research into novel BCG applications provides opportunities to investigate optimal management strategies for adverse reactions in a prospective manner using active safety surveillance.

COVID-19 and Beyond: Exploring Public Health Benefits from Non-Specific Effects of BCG Vaccination

Bacille Calmette–Guérin (BCG) vaccination, widely used throughout the world to protect against infant tuberculous meningitis and miliary tuberculosis (TB), can provide broad non-specific protection against infectious respiratory diseases in certain groups. Interest in BCG has seen a resurgence within the scientific community as the mechanisms for non-specific protection have begun to be elucidated. The impact of the COVID-19 pandemic on nearly every aspect of society has profoundly illustrated the pressure that respiratory infections can place on a national healthcare system, further renewing interest in BCG vaccination as a public health policy to reduce the burden of those illnesses. However, the United States does not recommend BCG vaccination due to its variable effectiveness against adult TB, the relatively low risk of Mycobacterium tuberculosis infection in most of the United States, and the vaccine’s interference with tuberculin skin test reactivity that complicates TB screening. In this review, we explore the broad immune training effects of BCG vaccination and literature on the effects of BCG vaccination on COVID-19 spread, disease severity, and mortality. We further discuss barriers to scheduled BCG vaccination in the United States and how those barriers could potentially be overcome.

Bacillus Calmette-Guérin Retains Clinically Relevant Viability for up to 72 Hours After Reconstitution: Potential Implications for Clinical Practice in Times of Shortage

There have been repeated supply shortages of bacillus Calmette-Guérin (BCG), the gold-standard immunotherapy for patients with high-grade non-muscle-invasive bladder cancer (NMIBC). Organizations have issued guidance on coping with this shortage, including administering split-dose BCG such that one vial may treat up to three patients. However, logistical implementation of this strategy in a real-world setting is hampered by the recommendation to use BCG within 2 h of reconstitution. We assessed BCG viability in terms of colony-forming units (CFUs) and demonstrated that viability remained constant for at least 8 h after reconstitution (decline at 8 h of 9.1% for lot 1 [p =  0.3] and 4.8% for lot 2 [p =  0.2]). While the viability at 24 h was lower, it did not drop to a level below that of reducing the BCG dose to one-third (67% for lot 1 and 60% for lot 2) and remained close to 50% for at least 72 h. An in vitro model using co-culture of BCG and leukocytes with a BCG-sensitive cell line (RT4-V6) demonstrated no decrease in the cytotoxic potential of BCG at 72 h. In times of shortage, BCG vials may be split and administered for up to at least 8 h (or even 72 h) after reconstitution, allowing more patients to benefit from BCG while placing less strain on the logistics of clinical practice. PATIENT SUMMARY: The current supply of and increased demand for bacillus Calmette-Guérin (BCG), used in the treatment of bladder cancer, have led to repeated BCG shortages. One way to address this is to provide a reduced BCG dose to allow more patients to be treated. In this study we found that BCG viability remains clinically relevant up to 72 h after reconstitution, thus allowing for more patients to be treated from a single vial.

The double-sided effects of Mycobacterium Bovis bacillus Calmette-Guérin vaccine

Bacillus Calmette-Guérin (BCG), the only vaccine proven to be effective against tuberculosis (TB), is the most commonly used vaccine globally. In addition to its effects on mycobacterial diseases, an increasing amount of epidemiological and experimental evidence accumulated since its introduction in 1921 has shown that BCG also exerts non-specific effects against a number of diseases, such as non-mycobacterial infections, allergies and certain malignancies. Recent Corona Virus Disease 2019 (COVID-19) outbreak has put BCG, a classic vaccine with significant non-specific protection, into the spotlight again. This literature review briefly covers the diverse facets of BCG vaccine, providing new perspectives in terms of specific and non-specific protection mechanisms of this old, multifaceted, and controversial vaccine.

The Strange Case of BCG and COVID-19: The Verdict Is Still up in the Air

COVID-19, caused by a novel coronavirus, SARS-CoV-2, contributes significantly to the morbidity and mortality in humans worldwide. In the absence of specific vaccines or therapeutics available, COVID-19 cases are managed empirically with the passive immunity approach and repurposing of drugs used for other conditions. Recently, a concept that bacilli Calmette-Guerin (BCG) vaccination could confer protection against COVID-19 has emerged. The foundation for this widespread attention came from several recent articles, including the one by Miller et al. submitted to MedRxiv, a pre-print server. The authors of this article suggest that a correlation exists between countries with a prolonged national BCG vaccination program and the morbidity/mortality due to COVID-19. Further, clinical BCG vaccination trials are currently ongoing in the Netherlands, Australia, the UK, and Germany with the hope of reducing mortality due to COVID-19. Although BCG vaccination helps protect children against tuberculosis, experimental studies have shown that BCG can also elicit a non-specific immune response against viral and non-mycobacterial infections. Here, we summarize the pros and cons of BCG vaccination and critically analyze the evidence provided for the protective effect of BCG against COVID-19 and highlight the confounding factors in these studies.

Molecular methods in diagnostics of post-BCG vaccine adverse events

INTRODUCTION

Bacillus Calmette-Guérin (BCG) is the only tuberculosis vaccine available and although it has been routinely used for more than 80 years, its protective effect varies depending on the age and the form of tuberculosis. Due to the close analogy between the vaccine strain and other species of the Mycobacterium tuberculosis complex, molecular methods are recommended for differential diagnosis of post-BCG complications. The aim of the study was to assess usefulness of molecular methods in diagnosis of post-BCG vaccine adverse events (VAEs).

MATERIAL AND METHODS

M. tuberculosis complex strains obtained in 2011-2017 from 68 ill children were subjected to molecular analysis.

RESULTS

Molecular analysis of 68 strains showed 100% agreement between the results in the GenoType MTBC method and the multiplex PCR method. For the strains isolated from 45 patients with suspected VAE, M. bovis BCG was obtained, whereas the strains isolated from the remaining 23 children were identified as M. tuberculosis. The analysis confirmed the close relationship between the result of identification and the type of material as well as the patient's age.

CONCLUSIONS

The use of genetic methods enables quick and detailed diagnostics of infections caused by M. bovis BCG, which allows for the confirmation or exclusion of VAE.

Micro-PET imaging of [18F]fluoroacetate combined with [18F]FDG to differentiate chronic Mycobacterium tuberculosis infection from an acute bacterial infection in a mouse model: a preliminary study

BACKGROUND

Mycobacterium tuberculosis (TB) infection is one of the deadliest infectious diseases worldwide and is responsible for 1.7 million deaths per year. The increase in multidrug-resistant TB poses formidable challenges to the global control of tuberculosis. TB infection could easily yield false-positive results in fluorine-18-fluorodeoxyglucose ([F]FDG) PET imaging for cancer detection because of its high [F]FDG uptake. We describe the combined [F]FDG PET with fluorine-18-fluoroacetate ([F]FAC), a promising analog of carbon-11-acetate, for targeting glycolysis and de novo lipogenesis, respectively, to determine the metabolic differences between chronic TB infection and acute infection.

MATERIALS AND METHODS

Six-month-old BALB/c mice were inoculated with Mycobacterium bovis to induce chronic TB infection, and Escherichia coli as well as Staphylococcus aureus to induce acute infection for an in-vivo imaging study. Eighteen days after inoculation for chronic TB infection and 5 days for acute infection, both [F]FDG and [F]FAC micro-PET were performed on the infected mice. Analysis of variance and the Tukey honest ad-hoc test were carried out to determine differences among treatment with different bacterial infections.

RESULTS

TB infection showed much lower [F] FAC accumulation than acute infection. However, both TB infection and acute infection exhibited high [F]FAC accumulation.

CONCLUSION

The marked metabolic differences in de novo lipogenesis and glycolysis in [F]FDG and [F]FAC uptakes in micro-PET imaging, respectively, help to differentiate chronic TB infection from acute infection.

Use of the Human Vaccine, Mycobacterium bovis Bacillus Calmette Guérin in Deer

The only vaccine ever approved for human tuberculosis was developed a century ago from an isolate of Mycobacterium bovis derived from a tuberculous cow. Initial safety and efficacy studies of an attenuated version of this isolate were conducted in cattle and other animals. In 1921 the first human, an infant, was orally dosed with this attenuated strain that came to be known as M. bovis bacillus Calmette-Guérin (BCG); named for Albert Calmette and Camille Guérin, the two French scientists that developed the strain. Since 1921, billions of people have been vaccinated with BCG making it the oldest, most widely used, and safest vaccine in use today. It is also the tuberculosis vaccine most studied for use in wildlife, including deer. While BCG vaccination of deer may not reliably prevent infection, it consistently decreases lesion severity, minimizing large, necrotic lesions, which often contain large numbers of bacilli. It is believed that decreased lesion severity correlates with decreased disease transmission; however, this hypothesis remains to be proven. Safety studies in white-tailed deer show BCG may persist in lymphoid tissues for up to 12 months; a factor to be considered in deer used for food. Beyond efficacy and safety, methods of vaccine delivery to free-ranging deer are also under investigation, both in the laboratory and in the field. The ideal delivery method is effective, efficient and safe for non-target species, including livestock. Ingestion of BCG by cattle is of special concern as such cattle may present as "false positives" using currently approved diagnostic methods, thus interfering with efforts by animal health agencies to monitor cattle for tuberculosis. An effective BCG vaccine for deer would be of value in regions where free-ranging deer represent a potential source of M. bovis for livestock. Such a vaccine would also be beneficial to farmed deer where M. bovis represents a serious threat to trade and productivity.

Evolution and Strain Variation in BCG

BCG vaccines were derived by in vitro passage, during the years 1908-1921, at the Pasteur Institute of Lille. Following the distribution of stocks of BCG to vaccine production laboratories around the world, it was only a few decades before different BCG producers recognized that there were variants of BCG, likely due to different passaging conditions in the different laboratories. This ultimately led to the lyophilization of stable BCG products in the 1950s and 1960s, but not before considerable evolution of the different BCG strains had taken place. The application of contemporary research methodologies has now revealed genomic, transcriptomic and proteomic differences between BCG strains. These molecular differences in part account for phenotypic differences in vitro between BCG strains, such as their variable secretion of antigenic proteins. Yet, the relevance of BCG variability for immunization policy remains elusive. In this chapter we present an overview of what is known about BCG evolution and its resulting strain variability, and provide some speculation as to the potential relevance for a vaccine given to over 100 million newborns each year.

A Birth Cohort Study of Maternal and Infant Serum PCB-153 and DDE Concentrations and Responses to Infant Tuberculosis Vaccination

BACKGROUND

Reasons for the highly variable and often poor protection conferred by the Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine are multifaceted and poorly understood.

OBJECTIVES

We aimed to determine whether early-life exposure to PCBs (polychlorinated biphenyls) and DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] reduces 6-month infant BCG vaccine response.

METHODS

Data came from families participating in a prospective birth cohort in eastern Slovakia. At birth, maternal and cord blood were collected for chemical analyses, and infants were immunized with BCG. Blood was collected from infants for chemical analyses and to determine 6-month BCG-specific immunoglobulin (Ig) G and IgA levels. Multivariable linear regression models were fit to examine chemical-BCG associations among approximately 500 mother-infant pairs, with adjustment for confounders.

RESULTS

The median 6-month infant concentration of the prevalent congener PCB-153 was 113 ng/g lipid [interquartile range (IQR): 37-248], and 388 ng/g lipid (IQR: 115-847) for DDE. Higher 6-month infant concentrations of PCB-153 and DDE were strongly associated with lower 6-month BCG-specific antibody levels. For instance, BCG-specific IgG levels were 37% lower for infants with PCB-153 concentrations at the 75th percentile compared to the 25th percentile (95% CI: -42, -32; p < 0.001). Results were similar in magnitude and precision for DDE. There was also evidence of PCB-DDE additivity, where exposure to both compounds reduced anti-BCG levels more than exposure to either compound alone.

CONCLUSIONS

The associations observed in this study indicate that environmental exposures may be overlooked contributors to poorer responses to BCG vaccine. The overall association between these exposures and tuberculosis incidence is unknown.

CITATION

Jusko TA, De Roos AJ, Lee SY, Thevenet-Morrison K, Schwartz SM, Verner MA, Palkovicova Murinova L, Drobná B, Kočan A, Fabišiková A, Čonka K, Trnovec T, Hertz-Picciotto I, Lawrence BP. 2016. A birth cohort study of maternal and infant serum PCB-153 and DDE concentrations and responses to infant tuberculosis vaccination. Environ Health Perspect 124:813-821; http://dx.doi.org/10.1289/ehp.1510101.

The establishment of sub-strain specific WHO Reference Reagents for BCG vaccine

As the latest addition to the sub-strain specific WHO Reference Reagents of BCG vaccine, an international collaborative study was completed to evaluate the suitability of a candidate BCG Moreau-RJ sub-strain as a WHO Reference Reagent of BCG vaccine. This follows the recent replacement of the WHO 1st International Reference Preparation for BCG vaccine, by three sub-strain specific WHO Reference Reagents of BCG vaccine (Danish 1331, Tokyo 172-1 and Russian BCG-I) in order to complete the coverage of most predominant sub-strains used for BCG vaccine production and distribution for use worldwide. The study used cultural viable count and modified ATP assays to quantify the preparation and multiplex PCR to confirm the identity of the sub-strain. The establishment of this WHO Reference Reagent of BCG vaccine of Moreau-RJ sub-strain was approved by the WHO Expert Committee on Biological Standardization meeting in October 2012. This preparation is available for distribution by NIBSC-MHRA, UK. The data from real-time stability monitoring demonstrated that these Reference Reagents of BCG vaccine are very stable in storage condition at -20°C. They serve as the valuable source of BCG Reference Reagents for use as comparators (1) for viability assays (such as cultural viable count and modified ATP assays); (2) for in vivo assays (such as the absence of virulent mycobacteria, dermal reactivity and protection assays) in the evaluation of candidate TB vaccines in non-clinical models; (3) for identity assays using molecular biology techniques.

Multiplex-PCR as an identity assay for Mycobacterium bovis BCG Moreau descendants

In the study, we assessed the identity of locally produced BCG vaccine via screening for the presence of genetic markers specific for particular Mycobacterium bovis BCG substrains - RD8, RD2, senX3-regX3, RD14, RD16, ΔRD1, DU2, a second copy of IS6110, mutation D322G in phoR, and deletions in fadD26-ppsA and Rv3887c regions. In order to increase the specificity of the multiplex-PCR test for locally produced BCG vaccine, we have modified previously developed primer sets by the introduction of a primer pair specific for deletion in Rv3887c. The modified multiplex-PCR specifically and reproducibly distinguished both BCG Moreau sublineages, and allowed, with no decrease in power, differentiation of BCG substrains of different origin. The growing knowledge of genetic differences among BCG vaccine strains enables improvements in the specificity of identity tests that will be useful both for routine release of vaccines and potential applications in clinical practice. Modified multiplex-PCR accompanied by PFGE analysis can serve as specific tools to monitor consistency in BCG manufacture.

Report of an International collaborative study to establish the first WHO reference reagents for BCG vaccines of three different sub-strains

The WHO First International Reference Preparation for BCG vaccine is over forty years old and is no longer available for distribution due to stock depletion and its significant loss of viability. International consultations identified a demand for replacement with sub-strain specific BCG preparations. An International collaborative study was carried out to evaluate three candidates for WHO Reference Reagent for BCG vaccine of Danish 1331, Russian BCG-I and Tokyo 172-1 sub-strains. These candidates were quantified for viability using both cultural viable count and modified ATP assays. The proposal for the establishment of these First WHO Reference Reagents for BCG vaccines was discussed in the WHO Expert Committee on Biological Standardization meeting, October 2009.

Report of an international collaborative study to evaluate the suitability of multiplex PCR as an identity assay for different sub-strains of BCG vaccine

Current methods for the identification of BCG vaccine in quality control settings involve acid-fast staining with microscopic examination. However, this method is unable to distinguish the many different sub-strains of BCG, or to differentiate BCG strains from virulent members of the Mycobacterium tuberculosis complex. A multiplex PCR (mPCR) which uses six target regions in mycobacteria has been developed to identify specific sub-strains of BCG. This study reports the findings from an international collaborative study to assess the accuracy, robustness and reproducibility of this mPCR method to differentiate BCG sub-strains. The method was found to fulfil these criteria successfully and was able to distinguish BCG sub-strains in vaccine preparations. The majority of the participants in the study generated the expected PCR product profiles indicating the method is also robust.

WHO Informal Consultation on standardization and evaluation of BCG vaccines Geneva, Switzerland 22-23 September 2009

The current World Health Organization Requirements for BCG vaccine are in need of revision to address the diversity of sub-strains used for production, potential improvements of quality control assays for lot release, and the establishment of sub-strain specific Reference Reagents. A consultation meeting was organized to discuss issues regarding the standardization and evaluation of BCG vaccines in the forum of regulators, BCG vaccine manufacturers, developers of selected new live tuberculosis (TB) vaccines and researchers. The development of new recombinant BCG and live attenuated TB vaccines and the characterisation of different BCG sub-strains using state-of-the-art technologies were also reviewed. The objective of the meeting was to revise and update the current recommendations focused on the scope, terminology, manufacturing issues, and the incorporation of new reference reagents and new quality control tests.

Vaccines and biosimilarity: a solution or a problem?

Biosimilarity is a significant issue for vaccines and a reasonable approach to this could facilitate licensing of follow-on products of similar design. However, the definitions and guideline criteria developed for similar versions of biotherapeutics may be too restrictive for vaccines, as the molecular composition of their active substances can rarely be defined precisely, and immunogenicity is an essential rather than an undesirable characteristic. Similarity in antigenic composition may be more relevant. The criteria that determine biosimilarity need more careful definition; superficial similarity may conceal significant differences in performance that can only be disclosed by careful clinical evaluation. These issues have been reviewed in detail for current types of bacterial and viral vaccines. For truly biosimilar products, limited clinical studies could be acceptable provided that they permit side-by-side comparison with the original product or another suitable reference. The prospect of the development of biosimilar products also emphasizes the need for improved regulatory tests capable of detecting subtle but biologically significant differences in vaccines. The need for an acceptable definition of biosimilarity and guidelines relevant to vaccines is emphasized.

Mapping the global use of different BCG vaccine strains

Bacille Calmette-Guérin (BCG) vaccine is one of the oldest and most commonly administered vaccines worldwide. Different BCG vaccine strains exist as a result of genetic changes that occurred during repeated subculture in different countries before lyophilisation was introduced for storage of seed lots in the 1960s. Increasing evidence suggests that these genetically divergent BCG vaccine strains are associated with different protective efficacy against tuberculosis (TB), different rates of adverse events and variable susceptibility to anti-tuberculous drugs. Information on which BCG vaccine strains are used in each country worldwide has not previously been collated. This report summarises data from the EuroTB network and from WHO/UNICEF in the first map depicting the BCG vaccine strains used globally. In 83 (44%) of 188 countries, more than one BCG vaccine strain was used during the five year period. In the countries that used only one strain, BCG Denmark was used in 32, BCG Russia/Bulgaria in 30, BCG Japan in eight, BCG Connaught in two. Twelve countries used their locally-produced BCG vaccine strains. The considerable variation in BCG vaccine strains used worldwide highlights the importance of documenting the particular vaccine strain used on an individual, local and national level. This is important for the interpretation of changes in the epidemiology of adverse events after BCG immunisation, for the management of adverse events after BCG immunisation, to interpret differences in the protective efficacy of BCG, and to inform the design of trials investigating novel TB vaccines.

Novel genome polymorphisms in BCG vaccine strains and impact on efficacy

Bacille Calmette-Guérin (BCG) is an attenuated strain of Mycobacterium bovis currently used as a vaccine against tuberculosis. Global distribution and propagation of BCG has contributed to the in vitro evolution of the vaccine strain and is thought to partially account for the different outcomes of BCG vaccine trials. Previous efforts by several molecular techniques effectively identified large sequence polymorphisms among BCG daughter strains, but lacked the resolution to identify smaller changes. In this study, we have used a NimbleGen tiling array for whole genome comparison of 13 BCG strains. Using this approach, in tandem with DNA resequencing, we have identified six novel large sequence polymorphisms including four deletions and two duplications in specific BCG strains. Moreover, we have uncovered various polymorphisms in the phoP-phoR locus. Importantly, these polymorphisms affect genes encoding established virulence factors including cell wall complex lipids, ESX secretion systems, and the PhoP-PhoR two-component system. Our study demonstrates that major virulence factors are different among BCG strains, which provide molecular mechanisms for important vaccine phenotypes including adverse effect profile, tuberculin reactivity and protective efficacy. These findings have important implications for the development of a new generation of vaccines.

Differential productions of lipid virulence factors among BCG vaccine strains and implications on BCG safety

Safety of BCG is a major concern in countries with a high burden of HIV/AIDS. Current BCG vaccine comprises of a heterogeneous group of substrains showing genotypic differences. The impact of these differences on BCG efficacy and safety remains unknown. Here we show that three BCG substrains, BCG-Japan, -Moreau, and -Glaxo, do not produce phthiocerol dimycocerosates (PDIMs) and phenolic glycolipids (PGLs), two cell wall lipids known to be important for the virulence of Mycobacterium tuberculosis and Mycobacterium bovis, suggesting that these BCG strains are more attenuated than others. We found that there is a good correlation between the ability of BCG strains to produce these two lipids and the propensity of BCG to induce complications following vaccination in children, which provides a partial explanation for the molecular mechanisms of BCG reactogenicity. Our finding has important implications for national immunization programmes particularly in HIV endemic countries. We suggest that PDIMs/PGLs analysis could offer a practical means for assessing the safety of various BCG vaccine strains currently used in the world.

Quantification of two variant strains contained in freeze-dried Japanese BCG vaccine preparation by real-time PCR

Japanese bacillus Calmette-Guerin (BCG) vaccine preparation contains two types of variant strains, Type I, which has a 22-base-pair deletion in the RD16 region, and Type II, which has an identical sequence to those of other BCG strains. In this study, we established a method to quantify the percentage of variant strain Type II contained in freeze-dried BCG product with real-time PCR. With this method we examined the master seed lot Tokyo 172, two secondary seed lots, Tokyo 172-1 and Tokyo 172-2, which were produced from Tokyo 172, and four commercial lots produced form Tokyo 172-1. Tokyo 172, Tokyo 172-1, and Tokyo 172-2 contained 55.1%, 19.5%, and 3.6% of Type II variant strain, respectively. Commercial lots contained 1.5%, 4.5%, 7.4%, and 4.3% of Type II variant strain, respectively. These results indicated that the two variant strains contained in the master seed lot continued to coexist in subsequently produced lots with a decrease in population of variant strain Type II. This method would be useful for quality control of commercial Japanese BCG vaccine preparations.

Dose-dependent immune response to Mycobacterium bovis BCG vaccination in neonates

In 10-week-old infants vaccinated at birth with Japanese Mycobacterium bovis BCG, the number of dermal needle penetrations correlated positively with frequency of proliferating CD4(+) T cells in whole blood following BCG stimulation for 6 days but did not correlate with secreted cytokine levels after 7 h or interferon CD4(+) T-cell frequency after 12 h of BCG stimulation.

Oral vaccination of brushtail possums with BCG: Investigation into factors that may influence vaccine efficacy and determination of duration of protection

AIMS

To determine factors that may influence the efficacy of an oral pelleted vaccine containing Mycobacterium bovis bacille Calmette-Guérin (BCG) to induce protection of brushtail possums against tuberculosis. To determine the duration of protective immunity following oral administration of BCG.

METHODS

In Study 1, a group of possums (n=7) was immunised by feeding 10 pellets containing dead Pasteur BCG, followed 15 weeks later with a single pellet of live Pasteur BCG. At that time, four other groups of possums (n=7 per group) were given a single pellet of live Pasteur BCG orally, a single pellet of live Danish BCG orally, 10 pellets of live Pasteur BCG orally, or a subcutaneous injection of live Pasteur BCG. For the oral pelleted vaccines, BCG was formulated into a lipid matrix, and each pellet contained approximately 107 colony forming units (cfu) of BCG, while the vaccine injected subcutaneously contained 106 cfu of BCG. A sixth, non-vaccinated, group (n=7) served as a control. All possums were challenged by the aerosol route with a low dose of virulent M. bovis 7 weeks after vaccination, and killed 7-8 weeks after challenge. Protection against challenge with M. bovis was assessed from pathological and bacteriological findings. In Study 2, lipid-formulated live Danish BCG was administered orally to three groups of possums (10-11 per group), and these possums were challenged with virulent M. bovis 8, 29 or 54 weeks later. The possums were killed 7 weeks after challenge, to assess protection in comparison to a non-vaccinated group.

RESULTS

The results from Study 1 showed that vaccine efficacy was not adversely affected by feeding dead BCG prior to live BCG. Feeding 10 vaccine pellets induced a level of protection similar to feeding a single pellet. Protection was similar when feeding possums a single pellet containing the Pasteur or Danish strains of BCG. All vaccinated groups had significantly reduced pathological changes or bacterial counts when compared to the non-vaccinated group. In Study 2, oral administration of Danish BCG induced protection against challenge with M. bovis, which persisted for at least 54 weeks after vaccination. Some protection was observed in possums challenged 54 weeks after vaccination, but this protection was significantly less than that observed in groups vaccinated 29 or 8 weeks prior to challenge. There was a strong relationship between the proportion of animals producing positive lymphocyte proliferation responses to M. bovis antigens and protection against challenge with M. bovis.

CONCLUSIONS

Factors considered potentially capable of interfering with vaccination, including feeding dead BCG to possums prior to feeding live BCG, feeding multiple doses of BCG at one time, and changing strains of BCG, were shown not to interfere with the acquisition of protective immune responses in possums. Protection against tuberculosis was undiminished up to 29 weeks after vaccination with BCG administered orally. It is concluded that vaccination of possums by feeding pellets containing BCG is a robust and efficient approach to enhance the resistance of these animals to tuberculosis.

BCG Moreau Rio de Janeiro: an oral vaccine against tuberculosis - review

The vaccine Bacillus of Calmette Guérin (BCG) was originally developed in France as an oral vaccine against tuberculosis. The oral use of this vaccine was replaced by the parenteral route in almost all countries after the Lubeck disaster. In contrast, Brazil retained the oral delivery of the vaccine until the mid-seventies when it was replaced by the intradermal route. This change in route of delivery was mainly secondary to pressure by medical practitioners based on the poor responses of oral immunized subjects to purified protein derivative (PPD) skin tests. Even after the change of route of delivery, Ataulpho de Paiva Foundation continued making the oral vaccine. Currently, BCG Moreau has been described as one of the most immunogenic and with fewer side effects than other BCGs. The genomics, proteomics and vaccine trials for oral BCG Moreau Rio de Janeiro are currently under investigation. In this review, we intend to describe the history of BCG Moreau Rio de Janeiro in Brazil.