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

A rare case of osteoarticular tuberculosis and tuberculous osteomyelitis of the left foot without pulmonary involvement

Tuberculosis (TB) of the musculoskeletal system is an uncommon manifestation, accounting for only 1-3% of all TB cases and typically affects the spine and large joints. Isolated TB of the foot is even rarer, comprising less than 10% of osteoarticular TB. Tuberculous osteomyelitis, where the infection is limited to the bone without joint involvement, is an even more uncommon presentation. A 55-year-old male with a history of fall presented with chronic left foot pain and swelling. Initial workup led to a misdiagnosis of Charcot foot. Despite treatment with analgesics and intra-articular platelet-rich plasma injections, symptoms still persisted for several months. MRI revealed inflammation in multiple joints with bone damage (erosions & edema) along with reduced joint space in talonavicular joint and Mycobacterium tuberculosis was identified on interferon gamma release assay. The patient was ultimately diagnosed with diffuse osteoarticular tuberculosis and tuberculous osteomyelitis of the left foot and commenced on anti-tubercular therapy. After few months symptoms were resolved and patient was tested negative for TB. Our case highlights the importance of maintaining a high index of suspicion for osteoarticular tuberculosis, even in the absence of pulmonary involvement, especially in immunocompromised patients like diabetics. This case emphasizes the importance of a multidisciplinary approach for accurate diagnosis and effective management of such challenging presentation.

Bacillus Calmette-Guérin (BCG) Vaccine in America and Overseas: A Narrative Review

This narrative review examines the role of the Bacillus Calmette-Guérin (BCG) vaccine in global tuberculosis (TB) control efforts, with particular emphasis on the differences in vaccination policies between countries, such as the US, where routine BCG administration is not practiced. A significant complication of the BCG vaccine is false positive results in the tuberculin skin test (TST), often leading to misdiagnoses and unnecessary treatments. To address these issues, interferon-gamma release assays (IGRAs) have emerged as a more specific diagnostic tool that reduces false positives associated with prior BCG vaccination. However, despite advancements, public health challenges persist in accurately detecting latent and active TB, particularly in populations previously vaccinated with BCG. This review synthesizes existing literature to assess these challenges, emphasizing the need for updated policies and improved diagnostic tools for BCG-vaccinated populations in the US and globally. Recommendations include integrating IGRAs into routine practice and tailoring TB control strategies to mitigate the diagnostic complications of BCG.

Tuberculosis vaccine - A timely analysis of the drawbacks for the development of novel vaccines

The BCG vaccine, Bacille Calmette Guerin, holds the distinction of being the most widely administered vaccine. Remarkably, a century has passed since its discovery; however, puzzlingly, questions persist regarding the effectiveness of the immune response it triggers. After years of diligent observation, it has been deduced that BCG imparts immunity primarily to a specific age group, namely children. This prompts a significant query: the rationale behind BCG's limited efficacy against TB in particular age groups and populations remains elusive. Beyond vaccinations, drug therapy has emerged as an alternative route for TB prevention. Nonetheless, this approach faces challenges in the contemporary landscape, marked by the emergence of new instances of MDR-TB and XDR-TB, compounded by the financial burden of treatment. It's noteworthy that BCG remains the sole WHO-approved vaccine for TB. This comprehensive review delves into several aspects, encompassing the immune response during infection, the shortcomings of BCG in conferring immunity, and the various factors contributing to its limitations. Within this discourse, we explore potential explanations for the observed deficiencies of the BCG vaccine and consider how these insights could catalyze the development of future vaccines. The current landscape of novel vaccine development for TB is illuminated, including a spotlight on the latest vaccine candidates.

Vaccines and Vaccine Response in the Small Bowel Transplant Patient

Vaccines should be regularly administered and their efficiency controlled, before and after intestinal transplantation. The household and health care providers should also be immunized, to further prevent transmission. Universal vaccination providing " herd immunity" should be enforced. Recommendations are given about timing, indications, and contraindications of each individual vaccine, before and after transplantation.

Effects of non-tuberculous mycobacteria on BCG vaccine efficacy: A narrative review

The Mycobacterium tuberculosis bacterial pathogen is responsible for the ongoing global tuberculosis (TB) epidemic. Bacille Calmette-Guérin (BCG), the only currently approved TB vaccine, is successful in preventing disseminated disease in newborns. However, it has a variable efficacy against pulmonary TB in adults. This protective effect of the vaccine varies greatly among different populations and geographical areas, which the increased exposure of particular populations to non-tuberculous mycobacteria (NTM) is considered as one of the reasons for this issue. Numerous studies have shown that exposure to NTM species causes the host immune system to be improperly primed. It has also been suggested that NTM species may be blamed for reduction in BCG vaccine effectiveness against M. tuberculosis. The increased exposure of certain populations to NTM has diverse effects on BCG efficacy. Moreover, the exposure to NTM can induce opposite effects on BCG efficacy depending on the NTM exposure route and survivability. A detailed understanding of the impact of NTM exposure on the efficacy of the BCG vaccine is essential for ongoing efforts to develop new TB vaccines as it may ultimately be a crucial success factor. The aim of this study was to review the findings of the studies focusing on the effects of NTM on BCG vaccine efficacy in animal models.

Epidemiology and antimicrobial resistance of Mycobacterium spp. in the United Arab Emirates: a retrospective analysis of 12 years of national antimicrobial resistance surveillance data

Introduction

The Eastern Mediterranean Regional Office (EMRO) region accounts for almost 8% of all global Mycobacterium tuberculosis (TB) cases, with TB incidence rates ranging from 1 per 100,000 per year in the United Arab Emirates (UAE) to 204 per 100,000 in Djibouti. The national surveillance data from the Middle East and North Africa (MENA) region on the epidemiology and antimicrobial resistance trends of TB, including MDR-TB remains scarce.

Methods

A retrospective 12-year analysis of N = 8,086 non-duplicate diagnostic Mycobacterium tuberculosis complex (MTB complex) isolates from the UAE was conducted. Data were generated through routine patient care during the 2010-2021 years, collected by trained personnel and reported by participating surveillance sites to the UAE National Antimicrobial Resistance (AMR) Surveillance program. Data analysis was conducted with WHONET, a windows-based microbiology laboratory database management software developed by the World Health Organization Collaborating Center for Surveillance of Antimicrobial Resistance, Boston, United States (https://whonet.org/).

Results

A total of 8,086 MTB-complex isolates were analyzed. MTB-complex was primarily isolated from respiratory samples (sputum 80.1%, broncho-alveolar lavage 4.6%, pleural fluid 4.1%). Inpatients accounted for 63.2%, including 1.3% from ICU. Nationality was known for 84.3% of patients, including 3.8% Emiratis. Of UAE non-nationals, 80.5% were from 110 countries, most of which were Asian countries. India accounted for 20.8%, Pakistan 13.6%, Philippines 12.7%, and Bangladesh 7.8%. Rifampicin-resistant MTB-complex isolates (RR-TB) were found in 2.8% of the isolates, resistance to isoniazid, streptomycin, pyrazinamide, and ethambutol, was 8.9, 6.9, 3.4 and 0.4%, respectively. A slightly increasing trend of resistance among MTB-complex was observed for rifampicin from 2.5% (2010) to 2.8% (2021).

Conclusion

Infections due to MTB-complex are relatively uncommon in the United Arab Emirates compared to other countries in the MENA region. Most TB patients in the UAE are of Asian origin, mainly from countries with a high prevalence of TB. Resistance to first line anti-tuberculous drugs is generally low, however increasing trends for MDR-TB mainly rifampicin linked resistance is a major concern. MDR-TB was not associated with a higher mortality, admission to ICU, or increased length of hospitalization as compared to non-MDR-TB.

An Immunoinformatics-Based Study of Mycobacterium tuberculosis Region of Difference-2 Uncharacterized Protein (Rv1987) as a Potential Subunit Vaccine Candidate for Preliminary Ex Vivo Analysis

Mycobacterium tuberculosis (Mtb) is the pathogen that causes tuberculosis and develops resistance to many of the existing drugs. The sole licensed TB vaccine, BCG, is unable to provide a comprehensive defense. So, it is crucial to maintain the immunological response to eliminate tuberculosis. Our previous in silico study reported five uncharacterized proteins as potential vaccine antigens. In this article, we considered the uncharacterized Mtb H37Rv regions of difference (RD-2) Rv1987 protein as a promising vaccine candidate. The vaccine quality of the protein was analyzed using reverse vaccinology and immunoinformatics-based quality-checking parameters followed by an ex vivo preliminary investigation. In silico analysis of Rv1987 protein predicted it as surface localized, secretory, single helix, antigenic, non-allergenic, and non-homologous to the host protein. Immunoinformatics analysis of Rv1987 by CD4 + and CD8 + T-cells via MHC-I and MHC-II binding affinity and presence of B-cell epitope predicted its immunogenicity. The docked complex analysis of the 3D model structure of the protein with immune cell receptor TLR-4 revealed the protein's capability for potential interaction. Furthermore, the target protein-encoded gene Rv1987 was cloned, over-expressed, purified, and analyzed by mass spectrometry (MS) to report the target peptides. The qRT-PCR gene expression analysis shows that it is capable of activating macrophages and significantly increasing the production of a number of key cytokines (TNF-α, IL-1β, and IL-10). Our in-silico analysis and ex vivo preliminary investigations revealed the immunogenic potential of the target protein. These findings suggest that the Rv1987 be undertaken as a potent subunit vaccine antigen and that further animal model immuno-modulation studies would boost the novel TB vaccine discovery and/or BCG vaccine supplement pipeline.

Bacillus Calmette-Guérin (BCG) Revaccination and Protection Against Tuberculosis: A Systematic Review

Bacillus Calmette-Guérin (BCG) vaccination remains a cornerstone in global efforts to combat tuberculosis (TB), a persistent public health threat worldwide. The purpose of this systematic review is to find out how well BCG revaccination protects against TB. This systematic review synthesized recent studies investigating the efficacy of BCG vaccination in preventing TB infection and disease. A total of 15 relevant publications were identified through a comprehensive search across multiple databases, including Cochrane Library, PubMed, Medline, and Scopus. The inclusion criteria encompassed studies involving humans, written in English, and categorized as case-control, cohort, meta-analysis, or full-text. Studies were selected based on their relevance to BCG revaccination and protection against TB, and a standardized data extraction form was used to gather pertinent information from each study. Quality assessment was conducted using established tools to evaluate the rigor, study design, and risk of bias in each included study. The findings revealed significant insights into BCG's effectiveness across different populations and age groups. Several studies demonstrated a substantial reduction in latent TB infection (LTBI) and incidence rates of TB following BCG vaccination. However, the protective efficacy of BCG revaccination varied across studies and populations, with some indicating modest protection against TB disease development, particularly in high-risk populations like healthcare workers. Furthermore, investigations into the immunological mechanisms underlying BCG's protective efficacy provided valuable insights into cytokine/chemokine profiles and immunomodulatory properties.

Construction and expression of Mycobacterium tuberculosis fusion protein SHR3 and its immunogenicity analysis in combination with various adjuvants

Tuberculosis (TB) today remains the leading cause of global deaths due to infectious bacterial pathogens. The Bacillus Calmette-Guérin (BCG) vaccine is the only vaccine clinically used to prevent TB. However, its limitations in preventing latent infection and TB reactivation mean that it does not provide comprehensive protection. In this study, we successfully constructed and expressed the multistage fusion protein, SHR3, and used whole blood IFN-γ release assay (WBIA) with flow cytometry to detect antigen specificity, further confirmed by enzyme-linked immunosorbent assay (ELISA). SHR3 and its subfractional proteins stimulated the level of IFN-γ production by lymphocytes from M. tb-infected patients, inducing the production of single-positive and double-positive CD4+ and CD8+ T cells with IFN-γ and IL-2, at levels significantly higher than those of healthy controls. The fusion protein and complex adjuvant group (SHR3/DMT) induced mice to produce significantly higher levels of IgG antibodies and their subclasses, with IgG2a/IgG1 results showing a convergent Th1-type response; mice in the BCG + SHR3/DMT group induced secretion of the highest levels of IL-2, and TNF-α, irrespective of stimulation with purified protein derivative or SHR3. These findings suggest that SHR3/DMT could be a potential subunit vaccine candidate that may serve as an effective booster vaccine after BCG primary immunization.

IV BCG Vaccination and Aerosol BCG Revaccination Induce Mycobacteria-Responsive γδ T Cells Associated with Protective Efficacy against M. tb Challenge

Intravenously (IV) delivered BCG provides superior tuberculosis (TB) protection compared with the intradermal (ID) route in non-human primates (NHPs). We examined how γδ T cell responses changed in vivo after IV BCG vaccination of NHPs, and whether these correlated with protection against aerosol M. tuberculosis challenge. In the circulation, Vδ2 T cell populations expanded after IV BCG vaccination, from a median of 1.5% (range: 0.8-2.3) of the CD3+ population at baseline, to 5.3% (range: 1.4-29.5) 4 weeks after M. tb, and were associated with TB protection. This protection was related to effector and central memory profiles; homing markers; and production of IFN-γ, TNF-α and granulysin. In comparison, Vδ2 cells did not expand after ID BCG, but underwent phenotypic and functional changes. When Vδ2 responses in bronchoalveolar lavage (BAL) samples were compared between routes, IV BCG vaccination resulted in highly functional mucosal Vδ2 cells, whereas ID BCG did not. We sought to explore whether an aerosol BCG boost following ID BCG vaccination could induce a γδ profile comparable to that induced with IV BCG. We found evidence that the aerosol BCG boost induced significant changes in the Vδ2 phenotype and function in cells isolated from the BAL. These results indicate that Vδ2 population frequency, activation and function are characteristic features of responses induced with IV BCG, and the translation of responses from the circulation to the site of infection could be a limiting factor in the response induced following ID BCG. An aerosol boost was able to localise activated Vδ2 populations at the mucosal surfaces of the lung. This vaccine strategy warrants further investigation to boost the waning human ID BCG response.

Immunological effects of the PE/PPE family proteins of Mycobacterium tuberculosis and related vaccines

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (Mtb), and its incidence and mortality are increasing. The BCG vaccine was developed in the early 20th century. As the most widely administered vaccine in the world, approximately 100 million newborns are vaccinated with BCG every year, which has saved tens of millions of lives. However, due to differences in region and race, the average protective rate of BCG in preventing tuberculosis in children is still not high in some areas. Moreover, because the immune memory induced by BCG will weaken with the increase of age, it is slightly inferior in preventing adult tuberculosis, and BCG revaccination cannot reduce the incidence of tuberculosis again. Research on the mechanism of Mtb and the development of new vaccines against TB are the main strategies for preventing and treating TB. In recent years, Pro-Glu motif-containing (PE) and Pro-Pro-Glu motif-containing (PPE) family proteins have been found to have an increasingly important role in the pathogenesis and chronic protracted infection observed in TB. The development and clinical trials of vaccines based on Mtb antigens are in progress. Herein, we review the immunological effects of PE/PPE proteins and the development of common PE/PPE vaccines.

BCG mediated protection of the lung against experimental SARS-CoV-2 infection

The observation of reduced COVID-19 incidence and severity in populations receiving neonatal intradermal BCG vaccination vaccine raised the question of whether BCG can induce non-specific protection against the SARS-CoV-2 (SCV2) virus. Subsequent epidemiologic studies and clinical trials have largely failed to support this hypothesis. Furthermore, in small animal model studies all investigators have failed to observe resistance to viral challenge in response to BCG immunization by the conventional and clinically acceptable intradermal or subcutaneous routes. Nevertheless, BCG administered by the intravenous (IV) route has been shown to strongly protect both hamsters and mice against SCV2 infection and disease. In this Perspective, we review the current data on the effects of BCG vaccination on resistance to COVID-19 as well as summarize recent work in rodent models on the mechanisms by which IV administered BCG promotes resistance to the virus and discuss the translational implications of these findings.

Ending the TB pandemic: the urgency of a new and improved TB vaccine and the World Health Organization's TB Vaccine Accelerator Council

We support the World Health Organization (WHO) recent decision to create a council to accelerate the development of a tuberculosis (TB) vaccine. With over 10 million new cases and 1.4 million deaths in 2020 alone, new and improved vaccines are urgently needed. Recent advancements in TB vaccine research offer hope, but a lack of funding, coordination and understanding of immune responses have impeded progress. A TB Vaccine Accelerator Council aims to bring together resources and expertise to overcome these obstacles and speed up development. Support and investment in research are crucial to ultimately eradicate TB and achieve the WHO goal of ending TB by 2035.

Liposomal delivery system/adjuvant for tuberculosis vaccine

As reported by the World Health Organization, about 10 million individuals were infected with tuberculosis (TB) worldwide. Moreover, approximately 1.5 million people died of TB, of which 214,000 were infected with HIV simultaneously. Due to the high infection rate, the need for effective TB vaccination is highly felt. Until now, various methodologies have been proposed for the development of a protein subunit vaccine for TB. These vaccines have shown higher protection than other vaccines, particularly the Bacillus culture vaccine. The delivery system and safety regulator are common characteristics of effective adjuvants in TB vaccines and the clinical trial stage. The present study investigates the current state of TB adjuvant research focusing on the liposomal adjuvant system. Based on our findings, the liposomal system is a safe and efficient adjuvant from nanosize to microsize for vaccinations against TB, other intracellular infections, and malignancies. Clinical studies can provide valuable feedback for developing novel TB adjuvants, which ultimately enhance the impact of adjuvants on next-generation TB vaccines.

Mycobacterium tuberculosis and SARS-CoV-2 co-infections: The knowns and unknowns

Health impacts of Mycobacterium tuberculosis (Mtb) and SARS-CoV-2 co-infections are not fully understood. Both pathogens modulate host responses and induce immunopathology with extensive lung damage. With a quarter of the world's population harboring latent TB, exploring the relationship between SARS-CoV-2 infection and its effect on the transition of Mtb from latent to active form is paramount to control this pathogen. The effects of active Mtb infection on establishment and severity of COVID-19 are also unknown, despite the ability of TB to orchestrate profound long-lasting immunopathologies in the lungs. Absence of mechanistic studies and co-infection models hinder the development of effective interventions to reduce the health impacts of SARS-CoV-2 and Mtb co-infection. Here, we highlight dysregulated immune responses induced by SARS-CoV-2 and Mtb, their potential interplay, and implications for co-infection in the lungs. As both pathogens master immunomodulation, we discuss relevant converging and diverging immune-related pathways underlying SARS-CoV-2 and Mtb co-infections.

Peptide microarray-based identification of dormancy-associated Mycobacterium tuberculosis antigens inducing immune responses among latent tuberculosis infection individuals in Thailand

Multi-stage tuberculosis (TB) vaccines composed of active- and dormancy-associated antigens are promising to trigger the immune protection against all TB stages. However, scientists are still in quest of the suitable vaccine candidates. In this study, we identified the potential targets for this vaccine in a high TB burden country, Thailand. Peptide microarray was applied to gauge IgA and IgG antibodies specific to 16,730 linear epitopes of 52 dormancy-associated Mycobacterium tuberculosis (M. tb) proteins in three study groups: active tuberculosis (ATB), latent tuberculosis infection (LTBI) and endemic healthy control (EHC). Preferential IgA recognition against epitopes of dormancy-associated proteins was identified in LTBI group. Validation of these findings revealed that LTBI subjects exhibited the greater levels of Rv2659c- and Rv1738-specific IgA than those of household contacts, but less than did ATB subjects. Frequencies of IFNγ-producing CD4⁺ and CD8⁺ T cells induced by proteins Rv2659c and Rv1738 were higher in LTBI than ATB individuals. The results indicated that LTBI group in a high TB burden country demonstrated cell-mediated immune response to proteins Rv2659c and Rv1738 stronger than those of ATB. These immune responses likely contribute to natural protection against dormant M. tb and might be potential targets for a multi-stage TB vaccine.

Galleria mellonella-intracellular bacteria pathogen infection models: the ins and outs

Galleria mellonella (greater wax moth) larvae are used widely as surrogate infectious disease models, due to ease of use and the presence of an innate immune system functionally similar to that of vertebrates. Here, we review G. mellonella-human intracellular bacteria pathogen infection models from the genera Burkholderia, Coxiella, Francisella, Listeria, and Mycobacterium. For all genera, G. mellonella use has increased understanding of host-bacterial interactive biology, particularly through studies comparing the virulence of closely related species and/or wild-type versus mutant pairs. In many cases, virulence in G. mellonella mirrors that found in mammalian infection models, although it is unclear whether the pathogenic mechanisms are the same. The use of G. mellonella larvae has speeded up in vivo efficacy and toxicity testing of novel antimicrobials to treat infections caused by intracellular bacteria: an area that will expand since the FDA no longer requires animal testing for licensure. Further use of G. mellonella-intracellular bacteria infection models will be driven by advances in G. mellonella genetics, imaging, metabolomics, proteomics, and transcriptomic methodologies, alongside the development and accessibility of reagents to quantify immune markers, all of which will be underpinned by a fully annotated genome.

Oral Bacille Calmette-Guérin (BCG) vaccination induces long-term potentiation of memory immune response to Ovalbumin airway challenge in mice

The Bacille Calmette-Guérin (BCG) is a potent immunomodulator. It was initially used by oral administration, but it is mostly used subcutaneously nowadays. This study shows that oral BCG vaccination modifies the immune response to a second non-related antigen (Ovalbumin) systemic immunization. Airway Ovalbumin challenge six months after the systemic intraperitoneal immunization resulted in a potent γδ⁺ T cell response in the lungs biased to IFN-γ and IL-17 production ex vivo and a mixed Th1, Th2, and Th17 T cells upon further stimulation with anti-CD3 mAb in vitro. Higher percentages of CD4⁺ T cells accompanied the augmented T cell response in oral BCG vaccinated mice. Also, the proportion of Foxp-3⁺ Tregs was diminished compared to PBS-gavaged and OVA-immunized mice. The anti-OVA-specific antibody response was also influenced by oral exposure to BCG so that these mice produced more IgG2a and less IgE detected in the sera. These results suggest that oral BCG vaccination can modify future immune responses to vaccines and improve immunity to pathogen infections, especially in the mucosal interfaces.

BCG-induced trained immunity enhances acellular pertussis vaccination responses in an explorative randomized clinical trial

Acellular pertussis (aP) booster vaccines are central to pertussis immunization programs, although their effectiveness varies. The Bacille Calmette-Guérin (BCG) vaccine is a prototype inducer of trained immunity, which enhances immune responses to subsequent infections or vaccinations. While previous clinical studies have demonstrated that trained immunity can protect against heterologous infections, its effect on aP vaccines in humans is unknown. We conducted a clinical study in order to determine the immunological effects of trained immunity on pertussis vaccination. Healthy female volunteers were randomly assigned to either receive BCG followed by a booster dose of tetanus-diphteria-pertussis inactivated polio vaccine (Tdap-IPV) 3 months later (BCG-trained), BCG + Tdap-IPV concurrently, or Tdap-IPV followed by BCG 3 months later. Primary outcomes were pertussis-specific humoral, T- and B-cell responses and were quantified at baseline of Tdap-IPV vaccination and 2 weeks thereafter. As a secondary outcome in the BCG-trained cohort, ex vivo leukocyte responses were measured in response to unrelated stimuli before and after BCG vaccination. BCG vaccination 3 months prior to, but not concurrent with, Tdap-IPV improves pertussis-specific Th1-cell and humoral responses, and also increases total memory B cell responses. These responses were correlated with enhanced IL-6 and IL-1β production at the baseline of Tdap-IPV vaccination in the BCG-trained cohort. Our study demonstrates that prior BCG vaccination potentiates immune responses to pertussis vaccines and that biomarkers of trained immunity are the most reliable correlates of those responses.