The Recombinant Bacille Calmette-Guérin Vaccine VPM1002: Ready for Clinical Efficacy Testing

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.

Pulmonary-Resident Memory Lymphocytes: Pivotal Orchestrators of Local Immunity Against Respiratory Infections

There is increasing evidence that lung-resident memory T and B cells play a critical role in protecting against respiratory reinfection. With a unique transcriptional and phenotypic profile, resident memory lymphocytes are maintained in a quiescent state, constantly surveying the lung for microbial intruders. Upon reactivation with cognate antigen, these cells provide rapid effector function to enhance immunity and prevent infection. Immunization strategies designed to induce their formation, alongside novel techniques enabling their detection, have the potential to accelerate and transform vaccine development. Despite most data originating from murine studies, this review will discuss recent insights into the generation, maintenance and characterisation of pulmonary resident memory lymphocytes in the context of respiratory infection and vaccination using recent findings from human and non-human primate studies.

A review of the BCG vaccine and other approaches toward tuberculosis eradication

Despite aggressive eradication efforts, Tuberculosis (TB) remains a global health burden, one that disproportionally affects poorer, less developed nations. The only vaccine approved for TB, the Bacillus of Calmette and Guérin (BCG) vaccine remains controversial because it's stated efficacy has been cited as anywhere from 0 to 80%. Nevertheless, there have been exciting discoveries about the mechanism of action of the BCG vaccine that suggests it has a role in immunization schedules today. We review recent data suggesting the vaccine imparts protection against both tuberculosis and non-tuberculosis pathogens via a newly discovered immune system called trained immunity. BCG's efficacy also appears to be tied to its affect on granulocytes at the epigenetic and hematopoietic stem cell levels, which we discuss in this article at length. We also write about how the different strains of the BCG vaccine elicit different immune responses, suggesting that certain BCG strains are more immunogenic than others. Finally, our review delves into how the current vaccine is being reformulated to be more efficacious, and track the development of the next generation vaccines against TB.

Thirty years of recombinant BCG: new trends for a centenary vaccine

Introduction: Global perception of the potential for Bacille Calmette-Guérin (BCG), and consequently recombinant BCG (rBCG), in a variety of prophylactic and therapeutic applications has been increasing. A century of information on BCG, and three decades of experience with rBCG, has generated solid knowledge in this field.Area covered: Here, we review the current state of knowledge of BCG and rBCG development. Molecular tools have facilitated the expression of a variety of molecules in BCG, with the aim of improving its efficacy as a tuberculosis vaccine, generating polyvalent vaccines against other pathogens, including viruses, bacteria, and parasites, and developing immunotherapy approaches against noninvasive bladder cancer. BCG's recently appraised heterologous effects and prospects for expanding its application to other diseases are also addressed.Expert opinion: There are high expectations for new tuberculosis vaccines currently undergoing advanced clinical trials, which could change the prospects of the field. Systems biology could reveal effective biomarkers of protection, which would greatly support vaccine development. The development of appropriate large-scale production processes would further support implementation of new vaccines and rBCG products. The next few years should consolidate the broader applications of BCG and produce insights into improvements using the recombinant BCG technology.

COVID-19 pandemic: SARS-CoV-2 specific vaccines and challenges, protection via BCG trained immunity, and clinical trials

Introduction: The coronavirus disease 2019 (COVID-19) pandemic continues to spread worldwide and vaccination remains the most effective approach to control COVID-19. Currently, at least ten COVID-19 vaccines have been authorized under emergency authorization. However, these vaccines still face many challenges.Areas covered: This study reviews the concept and mechanisms of trained immunity induced by the Bacille Calmette Guérin (BCG) vaccine and identifies questions that should be answered before the BCG vaccine could be used to combat COVID-19 pandemic. Moreover, we present for the first time the details of current BCG vaccine clinical trials, which are underway in various countries, to assess its effectiveness in combating the COVID-19 pandemic. Finally, we discuss the challenges of COVID-19 vaccines and opportunities for the BCG vaccine. The literature was found by searching the PubMed (https://pubmed.ncbi.nlm.nih.gov/), Web of Science (www.webofknowledge.com), Embase (https://www.embase.com), and CNKI (https://www.cnki.net/) databases. The date was set as the default parameter for each database.Expert opinion: The advantages of the BCG vaccine can compensate for the shortcomings of other COVID-19 vaccines. If the efficacy of the BCG vaccine against COVID-19 is confirmed by these clinical trials, the BCG vaccine may be essential to resolve the challenges faced by COVID-19 vaccines.

High-dose Mycobacterium tuberculosis aerosol challenge cannot overcome BCG-induced protection in Chinese origin cynomolgus macaques; implications of natural resistance for vaccine evaluation

This study describes the use of cynomolgus macaques of Chinese origin (CCM) to evaluate the efficacy and immunogenicity of the BCG vaccine against high dose aerosol Mycobacterium tuberculosis challenge. Progressive disease developed in three of the unvaccinated animals within 10 weeks of challenge, whereas all six vaccinated animals controlled disease for 26 weeks. Three unvaccinated animals limited disease progression, highlighting the intrinsic ability of this macaque species to control disease in comparison to macaques of other species and genotypes. Low levels of IFNγ were induced by BCG vaccination in CCM suggesting that IFNγ alone does not provide a sufficiently sensitive biomarker of vaccination in this model. An early response after challenge, together with the natural bias towards terminal effector memory T-cell populations and the contribution of monocytes appears to enhance the ability of CCM to naturally control infection. The high dose aerosol challenge model of CCM has value for examination of the host immune system to characterise control of infection which would influence future vaccine design. Although it may not be the preferred platform for the assessment of prophylactic vaccine candidates, the model could be well suited for testing post-exposure vaccination strategies and drug evaluation studies.

A century of BCG: Impact on tuberculosis control and beyond

BCG turns 100 this year and while it might not be the perfect vaccine, it has certainly contributed significantly towards eradication and prevention of spread of tuberculosis (TB). The search for newer and better vaccines for TB is an ongoing endeavor and latest results from trials of candidate TB vaccines such as M72AS01 look promising. However, recent encouraging data from BCG revaccination trials in adults combined with studies on mucosal and intravenous routes of BCG vaccination in non-human primate models have renewed interest in BCG for TB prevention. In addition, several well-demonstrated non-specific effects of BCG, for example, prevention of viral and respiratory infections, give BCG an added advantage. Also, BCG vaccination is currently being widely tested in human clinical trials to determine whether it protects against SARS-CoV-2 infection and/or death with detailed analyses and outcomes from several ongoing trials across the world awaited. Through this review, we attempt to bring together information on various aspects of the BCG-induced immune response, its efficacy in TB control, comparison with other candidate TB vaccines and strategies to improve its efficiency including revaccination and alternate routes of administration. Finally, we discuss the future relevance of BCG use especially in light of its several heterologous benefits.

BCG-induced protection against Mycobacterium tuberculosis infection: Evidence, mechanisms, and implications for next-generation vaccines

The tuberculosis (TB) vaccine Bacillus Calmette-Guérin (BCG) was introduced 100 years ago, but as it provides insufficient protection against TB disease, especially in adults, new vaccines are being developed and evaluated. The discovery that BCG protects humans from becoming infected with Mycobacterium tuberculosis (Mtb) and not just from progressing to TB disease provides justification for considering Mtb infection as an endpoint in vaccine trials. Such trials would require fewer participants than those with disease as an endpoint. In this review, we first define Mtb infection and disease phenotypes that can be used for mechanistic studies and/or endpoints for vaccine trials. Secondly, we review the evidence for BCG-induced protection against Mtb infection from observational and BCG re-vaccination studies, and discuss limitations and variation of this protection. Thirdly, we review possible underlying mechanisms for BCG efficacy against Mtb infection, including alternative T cell responses, antibody-mediated protection, and innate immune mechanisms, with a specific focus on BCG-induced trained immunity, which involves epigenetic and metabolic reprogramming of innate immune cells. Finally, we discuss the implications for further studies of BCG efficacy against Mtb infection, including for mechanistic research, and their relevance to the design and evaluation of new TB vaccines.

The BCG Vaccine for COVID-19: First Verdict and Future Directions

Despite of the rapid development of the vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it will take several months to have enough doses and the proper infrastructure to vaccinate a good proportion of the world population. In this interim, the accessibility to the Bacille Calmette-Guerin (BCG) may mitigate the pandemic impact in some countries and the BCG vaccine offers significant advantages and flexibility in the way clinical vaccines are administered. BCG vaccination is a highly cost-effective intervention against tuberculosis (TB) and many low-and lower-middle-income countries would likely have the infrastructure, and health care personnel sufficiently familiar with the conventional TB vaccine to mount full-scale efforts to administer novel BCG-based vaccine for COVID-19. This suggests the potential for BCG to overcome future barriers to vaccine roll-out in the countries where health systems are fragile and where the effects of this new coronavirus could be catastrophic. Many studies have reported cross-protective effects of the BCG vaccine toward non-tuberculosis related diseases. Mechanistically, this cross-protective effect of the BCG vaccine can be explained, in part, by trained immunity, a recently discovered program of innate immune memory, which is characterized by non-permanent epigenetic reprogramming of macrophages that leads to increased inflammatory cytokine production and consequently potent immune responses. In this review, we summarize recent work highlighting the potential use of BCG for the treatment respiratory infectious diseases and ongoing SARS-CoV-2 clinical trials. In situations where no other specific prophylactic tools are available, the BCG vaccine could be used as a potential adjuvant, to decrease sickness of SARS-CoV-2 infection and/or to mitigate the effects of concurrent respiratory infections.

CD8 T Cells Show Protection against Highly Pathogenic Simian Immunodeficiency Virus (SIV) after Vaccination with SIV Gene-Expressing BCG Prime and Vaccinia Virus/Sendai Virus Vector Boosts

Because both AIDS and tuberculosis are serious health threats in middle/low-income countries, development of a dual vaccine against them would be highly beneficial. To approach the goal, here we first assessed a urease-deficient bacillus Calmette-Guérin (BCG) for improvement of immunogenicity against both Mycobacterium tuberculosis and SIV. Second, we demonstrated the usefulness of Asian-origin cynomolgus monkeys for development of a preclinical AIDS vaccine by direct comparison with Indian rhesus macaques as the only validated hosts that identically mirror the outcomes of clinical trials, since the availability of Indian rhesus macaques is limited in countries other than the United States. Finally, we report the protective effect of a vaccination regimen comprising BCG, the highly attenuated vaccinia virus LC16m8Δ strain, and nontransmissible Sendai virus as safe vectors expressing SIV genes using repeated mucosal challenge with highly pathogenic SIVmac251. Identification of CD8⁺ T cells as a protective immunity suggests a future direction of AIDS vaccine development.

Toward development of a dual vaccine for human immunodeficiency virus type 1 (HIV-1) and tuberculosis infections, we developed a urease-deficient bacillus Calmette-Guérin (BCG) strain Tokyo172 (BCGΔurease) to enhance its immunogenicity. BCGΔurease expressing a simian immunodeficiency virus (SIV) Gag induced BCG antigen-specific CD4⁺ and CD8⁺ T cells more efficiently and more Gag-specific CD8⁺ T cells. We evaluated its protective efficacy against SIV infection in cynomolgus monkeys of Asian origin, shown to be as susceptible to infection with SIVmac251 as Indian rhesus macaques. Priming with recombinant BCG (rBCG) expressing SIV genes was followed by a boost with SIV gene-expressing LC16m8Δ vaccinia virus and a second boost with SIV Env-expressing Sendai virus. Eight weeks after the second boost, monkeys were repeatedly challenged with a low dose of SIVmac251 intrarectally. Two animals out of 6 vaccinees were protected, whereas all 7 control animals were infected without any early viral controls. In one vaccinated animal, which had the most potent CD8⁺ T cells in an in vitro suppression activity (ISA) assay of SIVmac239 replication, plasma viremia was undetectable throughout the follow-up period. Protection was confirmed by the lack of anamnestic antibody responses and detectable cell-associated provirus in various organs. Another monkey with a high ISA acquired a small amount of SIV, but it later became suppressed below the detection limit. Moreover, the ISA score correlated with SIV acquisition. On the other hand, any parameter relating anti-Env antibody was not correlated with the protection.

IMPORTANCE Because both AIDS and tuberculosis are serious health threats in middle/low-income countries, development of a dual vaccine against them would be highly beneficial. To approach the goal, here we first assessed a urease-deficient bacillus Calmette-Guérin (BCG) for improvement of immunogenicity against both Mycobacterium tuberculosis and SIV. Second, we demonstrated the usefulness of Asian-origin cynomolgus monkeys for development of a preclinical AIDS vaccine by direct comparison with Indian rhesus macaques as the only validated hosts that identically mirror the outcomes of clinical trials, since the availability of Indian rhesus macaques is limited in countries other than the United States. Finally, we report the protective effect of a vaccination regimen comprising BCG, the highly attenuated vaccinia virus LC16m8Δ strain, and nontransmissible Sendai virus as safe vectors expressing SIV genes using repeated mucosal challenge with highly pathogenic SIVmac251. Identification of CD8⁺ T cells as a protective immunity suggests a future direction of AIDS vaccine development.

PE_PGRS33, an Important Virulence Factor of Mycobacterium tuberculosis and Potential Target of Host Humoral Immune Response

PE_PGRS proteins are surface antigens of Mycobacterium tuberculosis (Mtb) and a few other pathogenic mycobacteria. The PE_PGRS33 protein is among the most studied PE_PGRSs. It is known that the PE domain of PE_PGRS33 is required for the protein translocation through the mycobacterial cell wall, where the PGRS domain remains available for interaction with host receptors. Interaction with Toll like receptor 2 (TLR2) promotes secretion of inflammatory chemokines and cytokines, which are key in the immunopathogenesis of tuberculosis (TB). In this review, we briefly address some key challenges in the development of a TB vaccine and attempt to provide a rationale for the development of new vaccines aimed at fostering a humoral response against Mtb. Using PE_PGRS33 as a model for a surface-exposed antigen, we exploit the availability of current structural data using homology modeling to gather insights on the PGRS domain features. Our study suggests that the PGRS domain of PE_PGRS33 exposes four PGII sandwiches on the outer surface, which, we propose, are directly involved through their loops in the interactions with the host receptors and, as such, are promising targets for a vaccination strategy aimed at inducing a humoral response.

Targeting Autophagy as a Strategy for Developing New Vaccines and Host-Directed Therapeutics Against Mycobacteria

Mycobacterial disease is an immense burden worldwide. This disease group includes tuberculosis, leprosy (Hansen's disease), Buruli Ulcer, and non-tuberculous mycobacterial (NTM) disease. The burden of NTM disease, both pulmonary and ulcerative, is drastically escalating globally, especially in developed countries such as America and Australia. Mycobacteria's ability to inhibit or evade the host immune system has contributed significantly to its continued prevalence. Pre-clinical studies have highlighted promising candidates that enhance endogenous pathways and/or limit destructive host responses. Autophagy is a cell-autonomous host defense mechanism by which intracytoplasmic cargos can be delivered and then destroyed in lysosomes. Previous studies have reported that autophagy-activating agents, small molecules, and autophagy-activating vaccines may be beneficial in restricting intracellular mycobacterial infection, even with multidrug-resistant strains. This review will examine how mycobacteria evade autophagy and discusses how autophagy could be exploited to design novel TB treatment strategies, such as host-directed therapeutics and vaccines, against Mycobacterium tuberculosis and NTMs.

Induction of Trained Immunity by Recombinant Vaccines

Vaccines represent an important strategy to protect humans against a wide variety of pathogens and have even led to eradicating some diseases. Although every vaccine is developed to induce specific protection for a particular pathogen, some vaccine formulations can also promote trained immunity, which is a non-specific memory-like feature developed by the innate immune system. It is thought that trained immunity can protect against a wide variety of pathogens other than those contained in the vaccine formulation. The non-specific memory of the trained immunity-based vaccines (TIbV) seems beneficial for the immunized individual, as it may represent a powerful strategy that contributes to the control of pathogen outbreaks, reducing morbidity and mortality. A wide variety of respiratory viruses, including respiratory syncytial virus (hRSV) and metapneumovirus (hMPV), cause serious illness in children under 5 years old and the elderly. To address this public health problem, we have developed recombinant BCG vaccines that have shown to be safe and immunogenic against hRSV or hMPV. Besides the induction of specific adaptive immunity against the viral antigens, these vaccines could generate trained immunity against other respiratory pathogens. Here, we discuss some of the features of trained immunity induced by BCG and put forward the notion that recombinant BCGs expressing hRSV or hMPV antigens have the capacity to simultaneously induce specific adaptive immunity and non-specific trained immunity. These recombinant BCG vaccines could be considered as TIbV capable of inducing simultaneously the development of specific protection against hRSV or hMPV, as well as non-specific trained-immunity-based protection against other pathogenic viruses.

Is mapping the BCG vaccine-induced immune responses the key to improving the efficacy against tuberculosis?

In recent years, the century-old Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccine against tuberculosis (TB) has been re-evaluated for its capacity to stem the global tide of TB. There is increasing evidence that the efficacy of BCG can be improved by the modified administration methods and schedules. Here, we first discuss recent approaches of vaccine administration, revaccination or boosting that have been used to try to improve the efficacy of BCG against TB. We then dive deeper into studies investigating the immune correlates of protection and describe studies that have investigated BCG-specific T-cell responses and the influence of environmental exposures. These studies all highlight that there is still a lot to learn about the immune response induced by BCG, both in terms of phenotype and specificity, which has been surprisingly understudied. We argue that several critical gaps in knowledge exist and must be addressed by future research to rationally improve the efficacy of BCG, including comprehensive, proteome-wide understanding of the epitopes derived from BCG recognized by BCG-vaccinated individuals, the phenotype of responding antigen-specific T cells and how previous exposure to environmental mycobacteria affect these parameters and thus influence vaccine efficacy. The development of modern techniques allows us to answer some of these questions to better understand how BCG works in terms of both protection against TB and the immune response that it triggers.

New tuberculosis vaccines: advances in clinical development and modelling

Tuberculosis remains a major source of morbidity and mortality worldwide, with 10 million cases and 1.5 million deaths in 2018. Achieving 'End TB' prevention and care goals by 2035 will likely require a new tuberculosis vaccine. The tuberculosis vaccine development pipeline has seen encouraging progress; however, questions around their population impact and implementation remain. Mathematical modelling investigates these questions to inform vaccine development and deployment strategies. We provide an update on the current vaccine development pipeline, and a systematic literature review of mathematical modelling of the epidemiological impact of new tuberculosis vaccines. Fourteen prophylactic tuberculosis vaccine candidates are currently in clinical trials. Two candidates have shown promise in phase II proof-of-concept efficacy trials: M72/AS01_E demonstrated 49.7% (95% CI; 2.1, 74.2) protection against tuberculosis disease, and BCG revaccination demonstrated 45.4% (95% CI; 6.4, 68.1) protection against sustained Mycobacterium tuberculosis infection. Since the last modelling review, new studies have investigated the epidemiological impact of differential vaccine characteristics, age targeting and spatial/risk group targeting. Critical research priorities for M72/AS01_E include completing the currently in-design trial, powered to improve the precision of efficacy estimates, include uninfected populations and further assess safety and immunogenicity in HIV-infected people. For BCG revaccination, the priority is completing the ongoing confirmation of efficacy trial. Critical modelling gaps remain on the full value proposition of vaccines, comparisons with other interventions and more realistic implementation strategies. Using carefully designed trials and modelling, we must prepare for success, to ensure that new vaccines will be promptly received by those most in need.

Can BCG be useful to mitigate the COVID-19 pandemic? A Canadian perspective

There is ample evidence from in vitro, animal and human studies that the Bacillus Calmette-Guerin (BCG) vaccine epigenetically reprograms innate immunity to provide “off target” protection against pathogens other than mycobacteria. This process has been termed “trained immunity”. Although recent ecological studies suggested an association between BCG policies and the frequency or severity of COVID-19 in different countries, the interpretation of these results is challenging. For this reason, a case-control study aiming to test this hypothesis has been initiated in Quebec. Several phase III clinical trials are underway, including one in Canada, to assess the efficacy of BCG against SARS-CoV-2 infection (results expected in 2021). In the past, BCG has been widely used in Canada but current indications are restricted to high-risk individuals and communities experiencing TB outbreaks as well as for the treatment of bladder cancer. The potential implication of BCG as an interim measure to mitigate COVID-19 is the subject of widespread discussion in the scientific community and can be considered for the vulnerable population in Canada. To conclude, BCG vaccination should be placed on the agenda of research funding agencies, scientific advisory committees on immunization and federal/provincial/territorial public health authorities.

Vaccines Against Tuberculosis: Problems and Prospects (Review)

Despite the efforts of the global medical and scientific community, tuberculosis remains the leading cause of death from infectious diseases. The expectation of success associated with the development of new anti-TB drugs was not justified, and the attention of researchers was largely drawn to the creation of new mycobacterial strains for vaccination against tuberculosis. The proposed review contains current information on the existing vaccine strains and the development of new, genetically engineered strains for the prevention of tuberculosis and the prevention and treatment of other diseases. The review includes relevant information on the correlation between BCG vaccination and the frequency and severity of COVID-19 infection.

Integrating fish models in tuberculosis vaccine development

Tuberculosis is a chronic infection by Mycobacterium tuberculosis that results in over 1.5 million deaths worldwide each year. Currently, there is only one vaccine against tuberculosis, the Bacillus Calmette–Guérin (BCG) vaccine. Despite widespread vaccination programmes, over 10 million new M. tuberculosis infections are diagnosed yearly, with almost half a million cases caused by antibiotic-resistant strains. Novel vaccination strategies concentrate mainly on replacing BCG or boosting its efficacy and depend on animal models that accurately recapitulate the human disease. However, efforts to produce new vaccines against an M. tuberculosis infection have encountered several challenges, including the complexity of M. tuberculosis pathogenesis and limited knowledge of the protective immune responses. The preclinical evaluation of novel tuberculosis vaccine candidates is also hampered by the lack of an appropriate animal model that could accurately predict the protective effect of vaccines in humans. Here, we review the role of zebrafish (Danio rerio) and other fish models in the development of novel vaccines against tuberculosis and discuss how these models complement the more traditional mammalian models of tuberculosis.

Summary: In this Review, we discuss how zebrafish (Danio rerio) and other fish models can complement the more traditional mammalian models in the development of novel vaccines against tuberculosis.

Targeting Unconventional Host Components for Vaccination-Induced Protection Against TB

The current tuberculosis (TB) vaccine, Bacille Calmette-Guerin (BCG), is effective in preventing TB in young children but was developed without a basic understanding of human immunology. Most modern TB vaccine candidates have targeted CD4⁺ T cell responses, thought to be important for protection against TB disease, but not known to be sufficient or critical for protection. Advances in knowledge of host responses to TB afford opportunities for developing TB vaccines that target immune components not conventionally considered. Here, we describe the potential of targeting NK cells, innate immune training, B cells and antibodies, and Th17 cells in novel TB vaccine development. We also discuss attempts to target vaccine immunity specifically to the lung, the primary disease site in humans.

BCG vaccine and COVID-19: implications for infection prophylaxis and cancer immunotherapy

The COVID-19 pandemic has killed over 400 000 people globally. Ecological evidence indicates that countries with national universal BCG vaccination programs for tuberculosis (TB) prevention have a much lower incidence of severe COVID-19 and mortality compared with those that do not have such programs. BCG is a century old vaccine used for TB prevention via infant/childhood vaccination in lowto middle-income countries with high infection prevalence rate and is known to reduce all-cause neonatal mortality. BCG remains the standard immunotherapy treatment for patients with high-risk non-muscle invasive bladder cancer globally for more than 44 years. Several trials are, therefore, investigating BCG as a prophylactic against COVID-19 in healthcare workers and the elderly. In this commentary, we discuss the potential mechanisms that may underlie BCG associated heterologous protection with a focus on tertiary lymphoid structure (TLS) organogenesis. Given the significance of TLSs in mucosal immunity, their association with positive prognosis and response to immune checkpoint blockade with a critical role of Type I interferon (IFN-1) in inducing these, we also discuss potentiating TLS formation as a promising approach to enhance anti-tumor immunity. We propose that lessons learned from BCG immunotherapy success could be applied to not only augment such microbe-based therapeutics but also lead to similar adjunctive IFN-1 activating approaches to improve response to immune checkpoint blockade therapy in cancer.

The Incidence of Tuberculosis in Infants, Siaya District, Western Kenya

BACKGROUND

Infants are a target population for new tuberculosis (TB) vaccines. TB incidence estimates are needed to guide the design of trials. To determine the TB incidence and cohort retention among young children using comprehensive diagnostic methods in a high burden area.

METHODS

Infants 0-42 days were enrolled. Through 4 monthly follow-up and unscheduled (sick) visits up to the age of 2 years, infants with presumptive TB based on a history of contact, TB symptoms or pre-determined hospitalization criteria were admitted to a case verification ward. Two induced sputa and gastric aspirates were collected for culture and GeneXpert. Mantoux and HIV tests were done. Clinical management was based on the Keith Edwards score. Cases were classified into microbiologically confirmed or radiologic, diagnosed by blinded expert assessment. Cox regression was used to identify risk factors for incident TB and study retention.

RESULTS

Of 2900 infants enrolled, 927 (32%) developed presumptive TB, 737/927 (80%) were investigated. Sixty-nine TB cases were diagnosed (bacteriologic and radiologic). All TB incidence was 2/100 person-years of observation (pyo) (95% CI: 1.65-2.65). Nine were bacteriologic cases, incidence 0.3/100 pyo. The radiologic TB incidence was 1.82/100 pyo. Bacteriologic TB was associated with infant HIV infection, higher Keith Edwards scores. Completeness of 4-month vaccinations and HIV infection were positively associated with retention.

CONCLUSIONS

TB incidence was high. An all TB endpoint would require a sample size of a few thousand children, but tens of thousands, when limited to bacteriologic TB.

Towards new TB vaccines

Mycobacterium tuberculosis remains the leading cause of death attributed to a single infectious organism. Bacillus Calmette-Guerin (BCG), the standard vaccine against M. tuberculosis, is thought to prevent only 5% of all vaccine-preventable deaths due to tuberculosis, thus an alternative vaccine is required. One of the principal barriers to vaccine development against M. tuberculosis is the complexity of the immune response to infection, with uncertainty as to what constitutes an immunological correlate of protection. In this paper, we seek to give an overview of the immunology of M. tuberculosis infection, and by doing so, investigate possible targets of vaccine development. This encompasses the innate, adaptive, mucosal and humoral immune systems. Though MVA85A did not improve protection compared with BCG alone in a large-scale clinical trial, the correlates of protection this has revealed, in addition to promising results from candidate such as VPM1002, M72/ASO1E and H56:IC31 point to a brighter future in the field of TB vaccine development.

Trained Immunity: a Tool for Reducing Susceptibility to and the Severity of SARS-CoV-2 Infection

SARS-CoV-2 infection is mild in the majority of individuals but progresses into severe pneumonia in a small proportion of patients. The increased susceptibility to severe disease in the elderly and individuals with co-morbidities argues for an initial defect in anti-viral host defense mechanisms. Long-term boosting of innate immune responses, also termed “trained immunity,” by certain live vaccines (BCG, oral polio vaccine, measles) induces heterologous protection against infections through epigenetic, transcriptional, and functional reprogramming of innate immune cells. We propose that induction of trained immunity by whole-microorganism vaccines may represent an important tool for reducing susceptibility to and severity of SARS-CoV-2.

Results of the phase I open label clinical trial SAKK 06/14 assessing safety of intravesical instillation of VPM1002BC, a recombinant mycobacterium Bacillus Calmette Guérin (BCG), in patients with non-muscle invasive bladder cancer and previous failure of conventional BCG therapy

Background: VPM1002BC is a modified mycobacterium Bacillus Calmette Guérin (BCG) for the treatment of non-muscle invasive bladder cancer (NMIBC). The genetic modifications are expected to result in better immunogenicity and less side effects. We report on patient safety and immunology of the first intravesical application of VPM1002BC in human.

Methods: Six patients with BCG failure received a treatment of 6 weekly instillations with VPM1002BC. Patients were monitored for adverse events (AE), excretion of VPM1002BC and cytokines, respectively.

Results: No DLT (dose limiting toxicity) occurred during the DLT-period. No grade ≥3 AEs occurred. Excretion of VPM1002BC in the urine was limited to less than 24 hours. Plasma levels of TNFα significantly increased after treatment and blood-derived CD4+ T cells stimulated with PPD demonstrated significantly increased intracellular GM-CSF and IFN expression.

Conclusion: The intravesical application of VPM1002BC is safe and well tolerated by patients and results in a potential Th1 weighted immune response.

Tuberculosis vaccine: A journey from BCG to present

Tuberculosis (TB) is the leading cause of death worldwide due to an infectious disease, causing around 1.6 million deaths each year. This situation has become more complicated by the emergence of drug-resistant Mycobacterium tuberculosis (M.tb) and HIV-TB co-infection, which has significantly worsened TB prognosis and treatment. Despite years of intensive research, Bacille Calmette-Guerin (BCG) remains the only licensed vaccine and has variable efficacy. It provides protection against childhood TB but is not effective in adult pulmonary TB. As a result of intense research in understanding TB vaccinology, there are many new vaccine candidates in clinical development and many more in pre-clinical trials which aim either to replace or boost BCG vaccine. This review discusses the history of BCG vaccine development and summarizes limitations of the current vaccine strategy and recent advances in improving BCG immunization along with other new vaccines in clinical trials which are promising candidates for the future tuberculosis vaccinology program.

The Future of Vaccines for Tuberculosis

Exciting clinical results from 2 clinical TB vaccine trials were published in 2018. These, plus promising preclinical candidates form a healthy pipeline of potential vaccines against the leading cause of death from a single infectious agent. The only licensed vaccine, the BCG, continues to be an important tool in protecting against severe forms of TB in children, but has not stopped the diseases causing 1.3 million deaths per year. This review provides an overview of the current TB vaccine pipeline, highlighting recent findings, describes work relating to epidemiologic impact of vaccines, and discusses the future of TB vaccine development.

Moving tuberculosis vaccines from theory to practice

Tuberculosis (TB) vaccine research has reached a unique point in time. Breakthrough findings in both the basic immunology of Mycobacterium tuberculosis infection and the clinical development of TB vaccines suggest, for the first time since the discovery of the Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine more than a century ago, that a novel, efficacious TB vaccine is imminent. Here, we review recent data in the light of our current understanding of the immunology of TB infection and discuss the identification of biomarkers for vaccine efficacy and the next steps in the quest for an efficacious vaccine that can control the global TB epidemic.

Vaccination Against Tuberculosis: Revamping BCG by Molecular Genetics Guided by Immunology

Tuberculosis (TB) remains a major health threat. Although a vaccine has been available for almost 100 years termed Bacille Calmette-Guérin (BCG), it is insufficient and better vaccines are urgently needed. This treatise describes first the basic immunology and pathology of TB with an emphasis on the role of T lymphocytes. Better understanding of the immune response to Mycobacterium tuberculosis (Mtb) serves as blueprint for rational design of TB vaccines. Then, disease epidemiology and the benefits and failures of BCG vaccination will be presented. Next, types of novel vaccine candidates are being discussed. These include: (i) antigen/adjuvant subunit vaccines; (ii) viral vectored vaccines; and (III) whole cell mycobacterial vaccines which come as live recombinant vaccines or as dead whole cell or multi-component vaccines. Subsequently, the major endpoints of clinical trials as well as administration schemes are being described. Major endpoints for clinical trials are prevention of infection (PoI), prevention of disease (PoD), and prevention of recurrence (PoR). Vaccines can be administered either pre-exposure or post-exposure with Mtb. A central part of this treatise is the description of the viable BCG-based vaccine, VPM1002, currently undergoing phase III clinical trial assessment. Finally, new approaches which could facilitate design of refined next generation TB vaccines will be discussed.

Tuberculosis vaccine development: from classic to clinical candidates

Bacillus Calmette-Guérin (BCG) has been in use for nearly 100 years and is the only licensed TB vaccine. While BCG provides protection against disseminated TB in infants, its protection against adult pulmonary tuberculosis (PTB) is variable. To achieve the ambitious goal of eradicating TB worldwide by 2050, there is an urgent need to develop novel TB vaccines. Currently, there are more than a dozen novel TB vaccines including prophylactic and therapeutic at different stages of clinical research. This literature review provides an overview of the clinical status of candidate TB vaccines and discusses the challenges and future development trends of novel TB vaccine research in combination with the efficacy of evaluation of TB vaccines, provides insight for the development of safer and more efficient vaccines, and may inspire new ideas for the prevention of TB.

Bacillus Calmette-Guérin (BCG) Therapy for Bladder Cancer: An Update

Physicians treating patients affected by nonmuscle-invasive bladder cancer (NMIBC) have been in shock during the last six years since manufacturing restrictions on the production of the first-option medicine, Mycobacterium bovis Bacillus Calmette-Guérin (BCG), have resulted in worldwide shortages. This shortage of BCG has led to a rethinking of the established treatment guidelines for the rationing of the administration of BCG. Some possible schedule modifications consist of a decrease in the length of maintenance treatment, a reduction in the dose of BCG in intravesical instillations or the use of different BCG substrains. All these strategies have been considered valuable in times of BCG shortage. In addition, the lack of availability of BCG has also led to the general recognition of the need to find new treatment options for these patients so that they are not dependent on a single treatment. Few alternatives are committed to definitively replacing BCG intravesical instillations, but several options are being evaluated to improve its efficacy or to combine it with other chemotherapeutic or immunotherapeutic options that can also improve its effect. In this article, we review the current state of the treatment with BCG in terms of all of the aforementioned aspects.

Integrating Biomaterials and Immunology to Improve Vaccines Against Infectious Diseases

Despite the success of vaccines in preventing many infectious diseases, effective vaccines against pathogens with ongoing challenges - such as HIV, malaria, and tuberculosis - remain unavailable. The emergence of new pathogen variants, the continued prevalence of existing pathogens, and the resurgence of yet other infectious agents motivate the need for new, interdisciplinary approaches to direct immune responses. Many current and candidate vaccines, for example, are poorly immunogenic, provide only transient protection, or create risks of regaining pathogenicity in certain immune-compromised conditions. Recent advances in biomaterials research are creating new potential to overcome these challenges through improved formulation, delivery, and control of immune signaling. At the same time, many of these materials systems - such as polymers, lipids, and self-assembly technologies - may achieve this goal while maintaining favorable safety profiles. This review highlights ways in which biomaterials can advance existing vaccines to safer, more efficacious technologies, and support new vaccines for pathogens that do not yet have vaccines. Biomaterials that have not yet been applied to vaccines for infectious disease are also discussed, and their potential in this area is highlighted.

Clinical Development of New TB Vaccines: Recent Advances and Next Steps

Mycobacterium tuberculosis (Mtb) kills more people worldwide than any single infectious pathogen, yet the only vaccine licensed against tuberculosis, Bacille Calmette Guerin (BCG) is approaching its centenary. Two recent advances in clinical tuberculosis vaccine development have invigorated the field. BCG revaccination of interferon-gamma release assay (IGRA) negative adolescents provided 45% protection against sustained Mtb infection defined by IGRA conversion; and the protein-subunit vaccine M72/AS01_E provided 50% protection against progression from Mtb infection to tuberculosis disease in IGRA-positive adults. These findings provide encouraging evidence for pre-exposure and post-exposure approaches to vaccination against tuberculosis, both of which may be necessary to rapidly interrupt the cycle of Mtb transmission and sustain long-term impact on global tuberculosis control. New trials are needed to demonstrate efficacy of M72/AS01_E with greater precision, in a wider age range, in diverse epidemic settings, and in populations that include Mtb-uninfected and HIV-infected persons. Modeling the impact of mass campaigns with M72/AS01_E and other fast-follower vaccine candidates will be crucial to make the use case and demonstrate public health value for TB endemic countries. The size and scope of the next generation of efficacy trials, and the need to expand and accelerate the existing clinical development pipeline, will require public and private consortium funding and concerted political will.

Animal Models of Tuberculosis Vaccine Research: An Important Component in the Fight against Tuberculosis

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis, is one of the top ten infectious diseases worldwide, and is the leading cause of morbidity from a single infectious agent. M. tuberculosis can cause infection in several species of animals in addition to humans as the natural hosts. Although animal models of TB disease cannot completely simulate the occurrence and development of human TB, they play an important role in studying the pathogenesis, immune responses, and pathological changes as well as for vaccine research. This review summarizes the commonly employed animal models, including mouse, guinea pig, rabbit, rat, goat, cattle, and nonhuman primates, and their characteristics as used in TB vaccine research, and provides a basis for selecting appropriate animal models according to specific research needs. Furthermore, some of the newest animal models used for TB vaccine research (such as humanized animal models, zebrafish, Drosophila, and amoeba) are introduced, and their characteristics and research progress are discussed.

[New vaccines against tuberculosis]

With about 10 million active disease cases and 1.5 million deaths in 2018, tuberculosis (TB) remains one of the most threatening infectious diseases. Yet, the World Health Organization (WHO) aims to reduce morbidity and mortality by 90 and 95%, respectively, between 2015 and 2035. Although diagnostics, therapeutics, and a vaccine are available, it is beyond doubt that better intervention measures are needed to accomplish this ambitious goal. The vaccine bacille Calmette-Guérin (BCG) partially protects infants against TB, but it is virtually ineffective against pulmonary TB in adolescents and adults. The efficacy of this vaccine, however, has not yet been fully exploited. In addition, new vaccine candidates are currently being assessed in clinical trials.Because a quarter of all people are latently infected with Mycobacterium tuberculosis (Mtb), new vaccines must be applied not only prior to infection (pre-exposure vaccination) but also after infection (postexposure vaccination). Prevention of infection, prevention of disease, and prevention of recurrence are currently assessed as clinical endpoints. Because protection against TB is primarily mediated by T lymphocytes, TB vaccine development focuses on protective T cell responses. Protein adjuvant formulations, viral vectors, and killed and live bacterial vaccines are currently being assessed in clinical trials. Moreover, therapeutic vaccination is clinically tested, notably in adjunct to canonical drug therapy to multiresistant TB. It is likely that a single vaccine cannot accomplish the various indications and that different vaccination strategies are required.

Mucosal delivery of tuberculosis vaccines: a review of current approaches and challenges

Introduction: Tuberculosis (TB) remains a major health threat and it is now clear that the current vaccine, BCG, is unable to arrest the global TB epidemic. A new vaccine is needed to either replace or boost BCG so that a better level of protection could be achieved. The route of entry of Mycobacterium tuberculosis, the causative organism, is via inhalation making TB primarily a respiratory disease. There is therefore good reason to hypothesize that a mucosally delivered vaccine against TB could be more effective than one delivered via the systemic route.

Areas covered: This review summarizes the progress that has been made in the area of TB mucosal vaccines in the last few years. It highlights some of the strengths and shortcomings of the published evidence and aims to discuss immunological and practical considerations in the development of mucosal vaccines.

Expert opinion: There is a growing body of evidence that the mucosal approach to vaccination against TB is feasible and should be pursued. However, further key studies are necessary to both improve our understanding of the protective immune mechanisms operating in the mucosa and the technical aspects of aerosolized delivery, before such a vaccine could become a feasible, deployable strategy.

Preclinical assessment of a new live attenuated Mycobacterium tuberculosis Beijing-based vaccine for tuberculosis

Tuberculosis still claims more lives than any other pathogen, and a vaccine better than BCG is urgently needed. One of the challenges for novel TB vaccines is to protect against all Mycobacterium tuberculosis lineages, including the most virulent ones, such as the Beijing lineage. Here we developed a live attenuated M. tuberculosis mutant derived from GC1237, a Beijing strain responsible for tuberculosis outbreaks in the Canary Islands. The mutant strain is inactivated both in the Rv1503c gene, responsible for surface glycolipid synthesis, and in the two-component global regulator PhoPR. This double mutant is as safe as BCG in immunodeficient SCID mice. In immune-competent mice and guinea pigs, the mutant is as protective as BCG against M. tuberculosis strains of common lineage 4 (Euro-American). By contrast, in mice the vaccine is protective against a M. tuberculosis strain of lineage 2 (East-Asian, Beijing), while BCG is not. These results highlight differences in protection efficacy of live attenuated M. tuberculosis-derived vaccine candidates depending on their genetic background, and provide insights for the development of novel live vaccines against TB, especially in East-Asian countries where M. tuberculosis strains of the Beijing family are highly dominant.

Construction and Characterization of the Mycobacterium tuberculosis sigE fadD26 Unmarked Double Mutant as a Vaccine Candidate

Despite the great increase in the understanding of the biology and pathogenesis of Mycobacterium tuberculosis achieved by the scientific community in recent decades, tuberculosis (TB) still represents one of the major threats to global human health. The only available vaccine (Mycobacterium bovis BCG) protects children from disseminated forms of TB but does not effectively protect adults from the respiratory form of the disease, making the development of new and more-efficacious vaccines against the pulmonary forms of TB a major goal for the improvement of global health. Among the different strategies being developed to reach this goal is the construction of attenuated strains more efficacious and safer than BCG. We recently showed that a sigE mutant of M. tuberculosis was more attenuated and more efficacious than BCG in a mouse model of infection. In this paper, we describe the construction and characterization of an M. tuberculosis sigE fadD26 unmarked double mutant fulfilling the criteria of the Geneva Consensus for entering human clinical trials. The data presented suggest that this mutant is even more attenuated and slightly more efficacious than the previous sigE mutant in different mouse models of infection and is equivalent to BCG in a guinea pig model of infection.

BCG-Induced Cross-Protection and Development of Trained Immunity: Implication for Vaccine Design

The Bacillus Calmette-Guérin (BCG) is a live attenuated tuberculosis vaccine that has the ability to induce non-specific cross-protection against pathogens that might be unrelated to the target disease. Vaccination with BCG reduces mortality in newborns and induces an improved innate immune response against microorganisms other than Mycobacterium tuberculosis, such as Candida albicans and Staphylococcus aureus. Innate immune cells, including monocytes and natural killer (NK) cells, contribute to this non-specific immune protection in a way that is independent of memory T or B cells. This phenomenon associated with a memory-like response in innate immune cells is known as "trained immunity." Epigenetic reprogramming through histone modification in the regulatory elements of particular genes has been reported as one of the mechanisms associated with the induction of trained immunity in both, humans and mice. Indeed, it has been shown that BCG vaccination induces changes in the methylation pattern of histones associated with specific genes in circulating monocytes leading to a "trained" state. Importantly, these modifications can lead to the expression and/or repression of genes that are related to increased protection against secondary infections after vaccination, with improved pathogen recognition and faster inflammatory responses. In this review, we discuss BCG-induced cross-protection and acquisition of trained immunity and potential heterologous effects of recombinant BCG vaccines.

Tuberculosis Vaccine Development: Progress in Clinical Evaluation

Tuberculosis (TB) is the leading killer among all infectious diseases worldwide despite extensive use of the Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine. A safer and more effective vaccine than BCG is urgently required. More than a dozen TB vaccine candidates are under active evaluation in clinical trials aimed to prevent infection, disease, and recurrence. After decades of extensive research, renewed promise of an effective vaccine against this ancient airborne disease has recently emerged. In two innovative phase 2b vaccine clinical trials, one for the prevention of Mycobacterium tuberculosis infection in healthy adolescents and another for the prevention of TB disease in M. tuberculosis-infected adults, efficacy signals were observed. These breakthroughs, based on the greatly expanded knowledge of the M. tuberculosis infection spectrum, immunology of TB, and vaccine platforms, have reinvigorated the TB vaccine field. Here, we review our current understanding of natural immunity to TB, limitations in BCG immunity that are guiding vaccinologists to design novel TB vaccine candidates and concepts, and the desired attributes of a modern TB vaccine. We provide an overview of the progress of TB vaccine candidates in clinical evaluation, perspectives on the challenges faced by current vaccine concepts, and potential avenues to build on recent successes and accelerate the TB vaccine research-and-development trajectory.

Tuberculosis: Current Status, Diagnosis, Treatment and Development of Novel Vaccines

Tuberculosis (TB) is an infectious disease that mainly affects the lungs and spreads to other organs of the body through the haematogenous route. It is one of the ten major causes of mortality worldwide. India has the highest incidence of new- and multidrug-resistant (MDR) - TB cases in the world. Bacille Calmette-Guerin (BCG) is the vaccine commonly available against TB. BCG does offer some protection against serious forms of TB in childhood but its protective effect wanes with age. Many new innovative strategies are being trailed for the development of effective and potent vaccines like mucosal- and epitope-based vaccines, which may replace BCG or boost BCG responses. The use of nanotechnology for diagnosis and treatment of TB is also in the pipeline along with many other vaccines, which are under clinical trials. Further, in-silico models were developed for finding new drug targets and designing drugs against Mycobacterium tuberculosis (Mtb). These models offer the benefit of computational experiments which are easy, inexpensive and give quick results. This review will focus on the available treatments and new approaches to develop potent vaccines for the treatment of TB.

Insights and challenges in tuberculosis vaccine development

Tuberculosis kills more people than any other pathogen and the need for a universally effective vaccine has never been greater. An effective vaccine will be a key tool in achieving the targets set by WHO in the End TB Strategy. Tuberculosis vaccine development is difficult and slow. Substantial progress has been made in research and development of tuberculosis vaccines in the past 20 years, and two clinical trial results from 2018 provide reason for optimism. However, many challenges to the successful licensure and deployment of an effective tuberculosis vaccine remain. The development of new tools for vaccine evaluation might facilitate these processes, and continued collaborative working and sustained funding will be essential.

Antibodies and tuberculosis: finally coming of age?

Are antibodies important for protection against tuberculosis? The jury has been out for more than 100 years. B cell depletion in experimental Mycobacterium tuberculosis infection failed to identify a major role for these cells in immunity to tuberculosis. However, recent identification of naturally occurring antibodies in humans that are protective during M. tuberculosis infection has reignited the debate. Here, we discuss the evidence for a protective role for antibodies in tuberculosis and consider the feasibility of designing novel tuberculosis vaccines targeting humoral immunity.

Mycobacterium bovis BCG in metastatic melanoma therapy

Melanoma is the most aggressive form of skin cancer, with a high mortality rate and with 96,480 new cases expected in 2019 in the USS. BRAF^V600E, the most common driver mutation, is found in around 50% of melanomas, contributing to tumor growth, angiogenesis, and metastatic progression. Dacarbazine (DTIC), an alkylate agent, was the first chemotherapeutic agent approved by the US Food and Drug Administration (FDA) used as a standard treatment. Since then, immunotherapies have been approved for metastatic melanoma (MM) including ipilimumab and pembrolizumab checkpoint inhibitors that help decrease the risk of progression. Moreover, Mycobacterium bovis Bacillus Calmette-Guerin (BCG) serves as an adjuvant therapy that induces the recruitment of natural killer NK, CD4⁺, and CD8⁺ T cells and contributes to antitumor immunity. BCG can be administered in combination with chemotherapeutic and immunotherapeutic agents and can be genetically manipulated to produce recombinant BCG (rBCG) strains that express heterologous proteins or overexpress immunogenic proteins, increasing the immune response and improving patient survival. In this review, we highlight several studies utilizing rBCG immunotherapy for MM in combination with other therapeutic agents.

The Incidence of Non-Tuberculous Mycobacteria in Infants in Kenya

There is inadequate understanding of the epidemiology of Non-Tuberculous Mycobacteria (NTM) among infants in high tuberculosis burden countries. The objective of this study was to document the incidence and diversity of NTM disease or colonisation in sputum specimens from infants with presumptive TB, the risk factors, and clinical characteristics, in a high TB and HIV burden setting in Western Kenya. A cohort of 2900 newborns was followed for 1–2 years to assess TB incidence. TB investigations included collection of induced sputa and gastric aspirates for culture and speciation by HAIN®, Tuberculin Skin Testing (TST), HIV testing, and chest radiography. The American Thoracic Society Criteria (ATS) were applied to identify NTM disease. Among 927 (32% of 2900) with presumptive TB, 742 (80%) were investigated. NTM were isolated from 19/742 (2.6%) infants. M. fortuitum was most frequently speciated (32%). Total person-time was 3330 years. NTM incidence was 5.7/1,000 person-years, 95% CI (3.5, 8.7). Infants diagnosed with TB were more likely to have NTM isolation (odds ratio 11.5; 95% CI 3.25, 41.0). None of the infants with NTM isolated met the criteria for NTM disease. The incidence of NTM isolation was comparable to similar studies in Africa. NTM isolation did not meet ATS criteria for disease and could represent colonisation. TB disease appears to be structural lung disease predisposing to NTM colonisation.

Current challenges and opportunities for bacillus Calmette-Guérin replacement vaccine candidates

Bacillus Calmette-Guérin (BCG) remains the only licensed vaccine against human tuberculosis (TB). BCG is a live-attenuated strain of Mycobacterium bovis, with limitations in efficacy against respiratory TB, the most common form of the disease responsible for transmission. However, continues to be used in the immunization programmes of different countries in the absence of another alternative. In order to improve BCG efficacy against pulmonary TB, in the current clinical TB vaccine pipeline, there are live-attenuated TB vaccines to replace BCG. This review discusses the current status of the development of live vaccine candidates designed to replace BCG from the rational strategies and immunological challenges to its clinical trial and identify key areas in the next years considered essential to confer improved safety and efficacy over BCG.

BCG Vaccination Prevents Reactivation of Latent Lymphatic Murine Tuberculosis Independently of CD4+ T Cells

Tuberculosis (TB) is a major global public health problem causing significant mortality and morbidity. In addition to ~10.4 million cases of active TB annually, it is estimated that about two billion people are latently infected with Mycobacterium tuberculosis (Mtb), the causative agent of TB. Reactivation of latent Mtb infection is the leading cause of death in patients with immunodeficiency virus (HIV) infection. The low efficiency of the only licensed anti-TB vaccine, Bacille Calmette–Guérin (BCG) to reduce pulmonary TB in adults contributes to this problem. Here we investigated if vaccination with conventional BCG or the genetically modified experimental BCGΔBCG1419c strain can prevent reactivation of latent lymphatic TB in a mouse model of induced reactivation, following the depletion of CD4⁺ T cells, as it occurs in HIV⁺ individuals. Vaccination with conventional BCG or BCGΔBCG1419c prevented reactivation of Mtb from the infected lymph node and the systemic spread of Mtb to spleen and lung. Prevention of reactivation was independent of vaccination route and was accompanied by reduced levels of circulating inflammatory cytokines and the absence of lung pathology. Our results demonstrate that vaccine-induced CD4⁺ T cells are not essential to prevent reactivation of latent lymphatic murine TB, and highlight the need to better understand how non-CD4⁺ immune cell populations participate in protective immune responses to control latent TB.

Designing tuberculosis vaccine efficacy trials - lessons from recent studies

INTRODUCTION

Tuberculosis (TB) is the leading infectious killer globally and new TB vaccines will be crucial to ending the epidemic. Since the introduction in 1921 of the only currently licensed TB vaccine, BCG, very few novel vaccine candidates or strategies have advanced into clinical efficacy trials. Areas covered: Recently, however, two TB vaccine efficacy trials with novel designs have reported positive results and are now driving new momentum in the field. They are the first Prevention of Infection trial, evaluating the H4:IC31 candidate or BCG revaccination in high-risk adolescents and a Prevention of Disease trial evaluating the M72/AS01_E candidate in M.tuberculosis-infected, healthy adults. These trials are briefly reviewed, and lessons learned are proposed to help inform the design of future efficacy trials. The references cited were chosen by the author based on PubMed searches to provide context for the opinions expressed in this Perspective article. Expert opinion: The opportunities created by these two trials for gaining critically important knowledge are game-changing for TB vaccine development. Their results clearly establish feasibility in the relatively near term of developing novel, effective vaccines that could be crucial to ending the TB epidemic.