Key recent advances in TB vaccine development and understanding of protective immune responses against Mycobacterium tuberculosis

Vaccination with Mincle agonist UM-1098 and mycobacterial antigens induces protective Th1 and Th17 responses

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the top infectious killers in the world. The only licensed vaccine against TB, Bacille Calmette-Guérin (BCG), provides variable protection against pulmonary TB, especially in adults. Hence, novel TB vaccine approaches are urgently needed. Both Th1 and Th17 responses are necessary for protection against TB, yet effective adjuvants and vaccine delivery systems for inducing robust Th1 and Th17 immunity are lacking. Herein we describe a synthetic Mincle agonist, UM-1098, and a silica nanoparticle delivery system that drives Th1/Th17 responses to Mtb antigens. Stimulation of human peripheral blood mononuclear cells (hPBMCs) with UM-1098 induced high levels of Th17 polarizing cytokines IL-6, IL-1β, IL-23 as well as IL-12p70, IL-4 and TNF-α in vitro. PBMCs from both C57BL/6 and BALB/c mice responded with a similar cytokine pattern in vitro and in vivo. Importantly, intramuscular (I.M.) vaccination with UM-1098-adjuvanted TB antigen M72 resulted in significantly higher antigen-specific IFN-γ and IL-17A levels in C57BL/6 wt mice than Mincle KO mice. Vaccination of C57BL/6 wt mice with immunodominant Mtb antigens ESAT6/Ag85B or M72 resulted in predominantly Th1 and Th17 responses and induced antigen-specific serum antibodies. Notably, in a virulent Mtb challenge model, vaccination with UM-1098 adjuvanted ESAT6/Ag85B or M72 significantly reduced lung bacterial burden when compared with unvaccinated mice and protection occurred in the absence of pulmonary inflammation. These data demonstrate that the synthetic Mincle agonist UM-1098 induces strong Th1 and Th17 immunity after vaccination with Mtb antigens and provides protection against Mtb infection in mice.

A viral vaccine design harnessing prior BCG immunization confers protection against Ebola virus

Previous studies have demonstrated the efficacy and feasibility of an anti-viral vaccine strategy that takes advantage of pre-existing CD4 + helper T (Th) cells induced by Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccination. This strategy uses immunization with recombinant fusion proteins comprised of a cell surface expressed viral antigen, such as a viral envelope glycoprotein, engineered to contain well-defined BCG Th cell epitopes, thus rapidly recruiting Th cells induced by prior BCG vaccination to provide intrastructural help to virus-specific B cells. In the current study, we show that Th cells induced by BCG were localized predominantly outside of germinal centers and promoted antibody class switching to isotypes characterized by strong Fc receptor interactions and effector functions. Furthermore, BCG vaccination also upregulated FcγR expression to potentially maximize antibody-dependent effector activities. Using a mouse model of Ebola virus (EBOV) infection, this vaccine strategy provided sustained antibody levels with strong IgG2c bias and protection against lethal challenge. This general approach can be easily adapted to other viruses, and may be a rapid and effective method of immunization against emerging pandemics in populations that routinely receive BCG vaccination.

Mycobacterium tuberculosis antigen 85B modifies BCG-induced antituberculosis immunity and favors pathogen survival

Tuberculosis is one of the deadliest infectious diseases worldwide. Mycobacterium tuberculosis has developed strategies not only to evade host immunity but also to manipulate it for its survival. We investigated whether Mycobacterium tuberculosis exploited the immunogenicity of Ag85B, one of its major secretory proteins, to redirect host antituberculosis immunity to its advantage. We found that administration of Ag85B protein to mice vaccinated with Bacillus Calmette-Guérin impaired the protection elicited by vaccination, causing a more severe infection when mice were challenged with Mycobacterium tuberculosis. Ag85B administration reduced Bacillus Calmette-Guérin-induced CD4 T-cell activation and IFN-γ, CCL-4, and IL-22 production in response to Mycobacterium tuberculosis-infected cells. On the other hand, it promoted robust Ag85B-responsive IFN-γ-producing CD4 T cells, expansion of a subset of IFN-γ/IL-10-producing CD4+FOXP3+Treg cells, differential activation of IL-17/IL-22 responses, and activation of regulatory and exhaustion pathways, including programmed death ligand 1 expression on macrophages. All this resulted in impaired intracellular Mycobacterium tuberculosis growth control by systemic immunity, both before and after the Mycobacterium tuberculosis challenge. Interestingly, Mycobacterium tuberculosis infection itself generated Ag85B-reactive inflammatory immune cells incapable of clearing Mycobacterium tuberculosis in both unvaccinated and Bacillus Calmette-Guérin-vaccinated mice. Our data suggest that Mycobacterium tuberculosis can exploit the strong immunogenicity of Ag85B to promote its own survival and spread. Since Ag85B is normally secreted by replicating bacteria and is commonly found in the lungs of the Mycobacterium tuberculosis-infected host, our findings may advance the understanding on the mechanisms of Mycobacterium tuberculosis pathogenesis and immune evasion.

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.

Antibodies as clinical tools for tuberculosis

Tuberculosis (TB) is a leading cause of morbidity and mortality worldwide. Global research efforts to improve TB control are hindered by insufficient understanding of the role that antibodies play in protective immunity and pathogenesis. This impacts knowledge of rational and optimal vaccine design, appropriate diagnostic biomarkers, and development of therapeutics. Traditional approaches for the prevention and diagnosis of TB may be less efficacious in high prevalence, remote, and resource-poor settings. An improved understanding of the immune response to the causative agent of TB, Mycobacterium tuberculosis (Mtb), will be crucial for developing better vaccines, therapeutics, and diagnostics. While memory CD4+ T cells and cells and cytokine interferon gamma (IFN-g) have been the main identified correlates of protection in TB, mounting evidence suggests that other types of immunity may also have important roles. TB serology has identified antibodies and functional characteristics that may help diagnose Mtb infection and distinguish between different TB disease states. To date, no serological tests meet the World Health Organization (WHO) requirements for TB diagnosis, but multiplex assays show promise for improving the sensitivity and specificity of TB serodiagnosis. Monoclonal antibody (mAb) therapies and serum passive infusion studies in murine models of TB have also demonstrated some protective outcomes. However, animal models that better reflect the human immune response to Mtb are necessary to fully assess the clinical utility of antibody-based TB prophylactics and therapeutics. Candidate TB vaccines are not designed to elicit an Mtb-specific antibody response, but evidence suggests BCG and novel TB vaccines may induce protective Mtb antibodies. The potential of the humoral immune response in TB monitoring and control is being investigated and these studies provide important insight into the functional role of antibody-mediated immunity against TB. In this review, we describe the current state of development of antibody-based clinical tools for TB, with a focus on diagnostic, therapeutic, and vaccine-based applications.

Comparison of the Immunogenicity and Efficacy of rBCG-EPCP009, BCG Prime-EPCP009 Booster, and EPCP009 Protein Regimens as Tuberculosis Vaccine Candidates

Bacillus Calmette-Guérin (BCG) is the only widely used prophylactic tuberculosis (TB) vaccine that can prevent severe TB in infants. However, it provides poor protection in adults, and therefore, there is ongoing research into new TB vaccines and immunization strategies with more durable immune effects. The recombinant BCG and BCG prime-protein booster are two important vaccine strategies that have recently been developed based on BCG and could improve immune responses. In this study, three immune strategies based on four protective antigens, namely, ESAT-6, CFP-10, nPPE18, and nPstS1, were applied to construct recombinant rBCG-EPCP009, EPCP009 subunit protein, and BCG prime-EPCP009 booster vaccine candidates. The short- and long-term immune effects after vaccination in Balb/c mice were evaluated based on humoral immunity, cellular immunity, and the ability of spleen cells to inhibit in vitro mycobacterial growth. At 8 and 12 weeks after the initial immunization, splenocytes from mice inoculated with the BCG prime-EPCP009 protein booster secreted higher levels of PPD- and EPCP009-specific IFN-γ, IL-2, TNF-α, IL-17, GM-CSF, and IL-12 and had a higher IFN-γ+CD4+ TEM:IL-2+CD8+ TCM cell ratio than splenocytes from mice inoculated with the rBCG-EPCP009 and EPCP009 proteins. In addition, the EPCPE009-specific IgG2a/IgG1 ratio was slightly higher in the BCG prime-EPCP009 protein booster group than in the other two groups. The in vitro mycobacterial inhibition assay showed that the splenocytes of mice from the BCG prime-EPCP009 protein booster group exhibited stronger inhibition of Mycobacterium tuberculosis (M. tuberculosis) growth than the splenocytes of mice from the other two groups. These results indicate that the BCG prime-EPCP009 protein booster exhibited superior immunogenicity and M. tuberculosis growth inhibition to the parental BCG, rBCG-EPCP009, and EPCP009 proteins under in vitro conditions. Thus, the BCG prime-EPCP009 protein booster may be important for the development of a more effective adult TB vaccine.

Conference report: WHO meeting summary on mRNA-based tuberculosis vaccine development

Tuberculosis (TB) is a global health emergency. Across the globe, approximately 2 billion people are currently infected with Mycobacterium tuberculosis (Mtb), and of those, 5-10% may progress to become ill and potentially transmit the bacterium. In 2021, nearly 10.6 million people developed TB disease and 1.6 million died. There is an urgent need for accelerated development of new TB-focused interventions, in particular, improved TB vaccines. However, progress in developing highly effective TB vaccines has been slow and is chronically under-resourced. The mRNA vaccine platform may offer an opportunity to accelerate development of new TB vaccines. In April 2023, the World Health Organization convened global experts to discuss the feasibility and potential value of mRNA-based vaccines for TB. Here we report on meeting deliberations related to the current TB vaccine pipeline and potential novel antigens, the status of efforts to identify correlates of protection, potential clinical development strategies and considerations for community acceptance of new TB vaccines based on this relatively new platform. The role of industry collaborations, ethics, social science, and responsibility to the global community regarding transparency and manufacturing capacity building were discussed through expert presentations and panel sessions. The overall conclusion of the meeting is that mRNA-based vaccines constitute a potentially powerful new tool for reducing the global burden of TB.

A novel multistage antigens ERA005f confer protection against Mycobacterium tuberculosis by driving Th-1 and Th-17 type T cell immune responses

Introduction

Tuberculosis (TB) is a major threat to human health. In 2021, TB was the second leading cause of death after COVID-19 among infectious diseases. The Bacillus Calmette-Guérin vaccine (BCG), the only licensed TB vaccine, is ineffective against adult TB. Therefore, there is an urgent need to develop new effective vaccines.

Methods

In this study, we developed a novel multistage subunit vaccine (ERA005f) comprising various proteins expressed in metabolic states, based on three immunodominant antigens (ESAT-6, Rv2628, and Ag85B). We utilized the E. coli prokaryotic expression system to express ERA005f and subsequently purified the protein using nickel affinity chromatography and anion exchange. Immunogenicity and protective efficacy of ERA005f and ERA005m were evaluated in BALB/c mice.

Results

ERA005f was consistently expressed as an inclusion body in a prokaryotic expression system, and a highly pure form of the protein was successfully obtained. Both ERA005f and ERA005m significantly improved IgG titers in the serum. In addition, mice immunized with ERA005f and ERA005m generated higher titers of antigen-specific IgG2a than the other groups. Elispot results showed that, compared with other groups, ERA005f increased the numbers of IFN-γ-secreting and IL-4-secreting T cells, especially the number of IFN-γ-secreting T cells. Meanwhile, ERA005f induced a higher number of IFN-γ+ T lymphocytes than ERA005m did. In addition, ERA005f improved the expression of cytokines, including IFN-γ, IL-12p70, TNF-α, IL-17, and GM-CSF and so on. Importantly, both ERA005f and ERA005m significantly inhibited the growth of Mtb.

Conclusion

The novel multistage antigen ERA005f elicited a strong antigen-specific humoral response and Th-1 and Th-17 cell-mediated immunity in mice. Meanwhile, it can effectively inhibit H37Rv growth in vitro, and represents a correlate of protection in vivo, indicating that ERA005f may exhibit excellent protective efficacy against Mycobacterium tuberculosis H37Rv infection. Our study suggests that ERA005f has the potential to be a promising multistage tuberculosis vaccine candidate.

Helper T cell bias following tuberculosis chemotherapy identifies opportunities for therapeutic vaccination to prevent relapse

Therapeutic vaccines have promise as adjunctive treatment for tuberculosis (TB) or as preventives against TB relapse. An important development challenge is the limited understanding of T helper (Th) cell roles during these stages of disease. A murine model of TB relapse was used to identify changes in Th populations and cytokine microenvironment. Active TB promoted expansion of Th1, Th2, Th17, and Th22 cells and cytokines in the lung. Following drug therapy, pulmonary Th17 and Th22 cells contracted, Th1 cells remained elevated, while Th cells producing IL-4 or IL-10 expanded. At relapse, Th22 cells failed to re-expand in the lung despite a moderate re-expansion of Th1 and Th17 cells and an increase in Th cytokine polyfunctionality. The dynamics of Th populations further differed by tissue compartment and disease presentation. These outcomes identify immune bias by Th subpopulations during TB relapse as candidate mechanisms for pathogenesis and targets for therapeutic vaccination.

Key advances in vaccine development for tuberculosis-success and challenges

Breakthrough findings in the clinical and preclinical development of tuberculosis (TB) vaccines have galvanized the field and suggest, for the first time since the development of bacille Calmette-Guérin (BCG), that a novel and protective TB vaccine is on the horizon. Here we highlight the TB vaccines that are in the development pipeline and review the basis for optimism in both the clinical and preclinical space. We describe immune signatures that could act as immunological correlates of protection (CoP) to facilitate the development and comparison of vaccines. Finally, we discuss new animal models that are expected to more faithfully model the pathology and complex immune responses observed in human populations.

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.

An anti-LpqH human monoclonal antibody from an asymptomatic individual mediates protection against Mycobacterium tuberculosis

Tuberculosis (TB) is an airborne disease caused by Mycobacterium tuberculosis (Mtb). Whilst a functional role for humoral immunity in Mtb protection remains poorly defined, previous studies have suggested that antibodies can contribute towards host defense. Thus, identifying the critical components in the antibody repertoires from immune, chronically exposed, healthy individuals represents an approach for identifying new determinants for natural protection. In this study, we performed a thorough analysis of the IgG/IgA memory B cell repertoire from occupationally exposed, immune volunteers. We detail the identification and selection of a human monoclonal antibody that exhibits protective activity in vivo and show that it targets a virulence factor LpqH. Intriguingly, protection in both human ex vivo and murine challenge experiments was isotype dependent, with most robust protection being mediated via IgG2 and IgA. These data have important implications for our understanding of natural mucosal immunity for Mtb and highlight a new target for future vaccine development.

Transcriptional signatures measured in whole blood correlate with protection against tuberculosis in inbred and outbred mice

Although BCG has been used for almost 100 years to immunize against Mycobacterium tuberculosis, TB remains a global public health threat. Numerous clinical trials are underway studying novel vaccine candidates and strategies to improve or replace BCG, but vaccine development still lacks a well-defined set of immune correlates to predict vaccine-induced protection against tuberculosis. This study aimed to address this gap by examining transcriptional responses to BCG vaccination in C57BL/6 inbred mice, coupled with protection studies using Diversity Outbred mice. We evaluated relative gene expression in blood obtained from vaccinated mice, because blood is easily accessible, and data can be translated to human studies. We first determined that the average peak time after vaccination is 14 days for gene expression of a small subset of immune-related genes in inbred mice. We then performed global transcriptomic analyses using whole blood samples obtained two weeks after mice were vaccinated with BCG. Using comparative bioinformatic analyses and qRT-PCR validation, we developed a working correlate panel of 18 genes that were highly correlated with administration of BCG but not heat-killed BCG. We then tested this gene panel using BCG-vaccinated Diversity Outbred mice and revealed associations between the expression of a subset of genes and disease outcomes after aerosol challenge with M. tuberculosis. These data therefore demonstrate that blood-based transcriptional immune correlates measured within a few weeks after vaccination can be derived to predict protection against M. tuberculosis, even in outbred populations.

Intravenous BCG Vaccination of Diversity Outbred Mice Results in Moderately Enhanced Protection against Challenge with Mycobacterium tuberculosis Compared to Intradermal Vaccination

Tuberculosis is still the leading cause of death globally from any infectious disease, despite the widespread use of the live attenuated vaccine Bacille Calmette Guerin (BCG). While BCG has some efficacy against disseminated TB disease in children, protection wanes into adulthood resulting in over 1.8 million TB deaths per year. This has led to efforts to develop novel vaccine candidates that either replace or boost BCG, as well as to test novel delivery mechanisms to enhance BCG's efficacy. Traditional BCG vaccination is performed as an intradermal (ID) injection but delivering BCG by an alternate route may enhance the depth and breadth of protection. Previously, we demonstrated that phenotypically and genotypically disparate Diversity Outbred (DO) mice have heterogenous responses to M. tuberculosis challenge following intradermal BCG vaccination. Here, we utilize DO mice to examine BCG-induced protection when BCG is delivered systemically via intravenous (IV) administration. We find that DO mice vaccinated with IV BCG had a greater distribution of BCG throughout their organs compared to ID-vaccinated animals. However, compared to ID-vaccinated mice, M. tuberculosis burdens in lungs and spleens were not significantly reduced in animals vaccinated with BCG IV, nor was lung inflammation significantly altered. Nonetheless, DO mice that received BCG IV had increased survival over those vaccinated by the traditional ID route. Thus, our results suggest that delivering BCG by the alternate IV route enhances protection as detected in this diverse small animal model.

Blood transcriptional correlates of BCG-induced protection against tuberculosis in rhesus macaques

Blood-based correlates of vaccine-induced protection against tuberculosis (TB) are urgently needed. Here, we analyze the blood transcriptome of rhesus macaques immunized with varying doses of intravenous (i.v.) BCG followed by Mycobacterium tuberculosis (Mtb) challenge. We use high-dose i.v. BCG recipients for "discovery" and validate our findings in low-dose recipients and in an independent cohort of macaques receiving BCG via different routes. We identify seven vaccine-induced gene modules, including an innate module (module 1) enriched for type 1 interferon and RIG-I-like receptor signaling pathways. Module 1 on day 2 post-vaccination highly correlates with lung antigen-responsive CD4 T cells at week 8 and with Mtb and granuloma burden following challenge. Parsimonious signatures within module 1 at day 2 post-vaccination predict protection following challenge with area under the receiver operating characteristic curve (AUROC) ≥0.91. Together, these results indicate that the early innate transcriptional response to i.v. BCG in peripheral blood may provide a robust correlate of protection against TB.

NOS2/miR-493-5p Signaling Regulates in the LPS-Induced Inflammatory Response in the RAW264.7 Cells

Tuberculosis (TB) is a fatal infectious disease; however, the molecular mechanisms underlying the pathogenicity of TB remain elusive. The present study aims to identify potential biomarkers associated with Mycobacterium tuberculosis (M.tb) infection by using integrated bioinformatics and in vitro validation studies. GSE50050, GSE78706, and GSE108844 data from the gene expression omnibus (GEO) database were downloaded to identify differentially expressed genes (DEGs). The functions of DEGs were further subjected to gene ontology (GO) and KEGG pathway analysis. The hub genes from the DEGs were determined based on the protein-protein interaction (PPI) network analysis. Finally, the hub genes were experimentally validated using the in vitro functional studies. A total of 26 common DEGs were identified among GSE50050, GSE78706, and GSE108844. The functional enrichment analysis showed that the common DEGs were associated with cytokines response and TB pathways. The PPI network analysis identified nine hub genes. Further in vitro studies showed that nitric oxide synthase 2 (NOS2) was up-regulated in RAW264.7 cells upon lipopolysaccharides (LPS) stimulation, which was accompanied by increased inflammatory cytokines release. Furthermore, NOS2 was found to be a target of miR-493-5p, which was confirmed by luciferase reporter assay. NOS2 was repressed by miR-493-5p overexpression and was up-regulated after miR-493-5p inhibition in RAW264.7 cells. The rescue experiments showed that LPS-induced increase in the inflammatory cytokines of the RAW264.7 cells was significantly attenuated by NOS2 knockdown and miR-493-5p overexpression. Collectively, our results for the first time demonstrated that NOS2/miR-493-5p signaling pathway may potentially involve in the inflammatory response during bacterial infection such as M. tb infection.

Tuberculosis vaccines update: Is an RNA-based vaccine feasible for tuberculosis?

OBJECTIVES

Despite concerted efforts, Mycobacterium tuberculosis (M.tb), the pathogen that causes tuberculosis (TB), continues to be a burden on global health, regaining its dubious distinction in 2022 as the world's biggest infectious killer with global COVID-19 deaths steadily declining. The complex nature of M.tb, coupled with different pathogenic stages, has highlighted the need for the development of novel immunization approaches to combat this ancient infectious agent. Intensive efforts over the last couple of decades have identified alternative approaches to improve upon traditional vaccines that are based on killed pathogens, live attenuated agents, or subunit recombinant antigens formulated with adjuvants. Massive funding and rapid advances in RNA-based vaccines for immunization have recently transformed the possibility of protecting global populations from viral pathogens, such as SARS-CoV-2. Similar efforts to combat bacterial pathogens such as M.tb have been significantly slower to implement.

METHODS

In this review, we discuss the application of a novel replicating RNA (repRNA)-based vaccine formulated and delivered in nanostructured lipids.

RESULTS

Our preclinical data are the first to report that RNA platforms are a viable system for TB vaccines and should be pursued with high-priority M.tb antigens containing cluster of differentiation (CD4+) and CD8+ T-cell epitopes.

CONCLUSION

This RNA vaccine shows promise for use against intracellular bacteria such as M.tb as demonstrated by the feasibility of construction, enhanced induction of cell-mediated and humoral immune responses, and improved bacterial burden outcomes in in vivo aerosol-challenged preclinical TB models.

Immune disturbances in female genital tuberculosis and latent genital tuberculosis

BACKGROUND

Female genital tuberculosis (FGTB), an important clinical sub-type of extra-pulmonary tuberculosis (EPTB) is responsible for about 10% cases of infertility in India. Both FGTB and latent genital tuberculosis (LGTB) can cause infertility through blockage of fallopian tubes and through altered uterine endometrial receptivity.

AIMS

This review tries to elucidates the role of various immune factors in FGTB and LGTB.

CONTENT

Various immune disturbances are observed in FGTB and LGTB like growth factors and cytokines which inhibit implantation and several inflammatory signaling pathways like mitogen activated protein kinase (MAPK), natural killer (NK) cells, nuclear factor kappa-B (NF-KB), tumor necrosis factor (TNF), and toll like receptors (TLR) signaling are dysregulated. These altered immune factors and pathways may be detected in the endometrial biopsies at the early stages of disease before permanent damage. Prompt and adequate treatment with the four anti-tubercular drugs (rifampicin [R], isoniazid [H], pyrazinamide [Z], and ethambutol [E]) can increase pregnancy rates in some of these women. Assisted reproduction especially in-vitro fertilization and embryo transfer may be required for some women.

IMPLICATIONS

Inflammatory pathways identified from the gene profiling have enabled development of potential biomarkers for early diagnosis of FGTB. Immunomodulation and novel biotechniques like stem cell transplantation, nanoparticles and host directed therapies are being tried in selected patients of FGTB and LGTB with promising results.

A Multicomponent Nucleic Acid Enzyme-Cleavable Quantum Dot Nanobeacon for Highly Sensitive Diagnosis of Tuberculosis with the Naked Eye

Clinical tuberculosis (TB) screening and diagnosis are crucial for controlling the spread of this life-threatening infectious disease. In this work, a novel, rapid, and simple colorimetric detection platform for TB was developed based on a quantum dot-based nanobeacon (QD-NB) and multicomponent nucleic acid enzyme (MNAzyme). In the presence of target DNA (IS1081 gene fragment), the recombinase polymerase amplification (RPA) was performed and the amplicons were chemically DNA-denatured and then subjected to MNAzyme reaction. RNA-cleaving MNAzyme assembly included the recognition of target DNA and hybridization with a QD-NB fluorescence probe. Under the addition of Mg²⁺, the RNA-containing QD-NB as a cleavable substrate could be broken into two DNA fragments, leading to green fluorescence release due to their departure from a black hole quencher (BHQ2). The TB detection could be achieved with the naked eye under a portable and inexpensive UV flashlight. Our results demonstrated that QD-NB-based MNAzyme colorimetric assays improved the detection sensitivity by 1 order of magnitude compared with the detection using RPA. The limit of detection (LOD) of the visual reading was as low as 2 copies/μL (3.3 amol/L). Excellent specificity and reproducibility could also be achieved. Furthermore, the practical application of the colorimetric method for TB diagnosis was verified by 36 clinical TB patients and 20 healthy individuals. The developed QD-NB-based MNAzyme colorimetric assays provided a rapid, convenient, sensitive, and accurate alternative for clinical TB screening and diagnosis.

A Structural View at Vaccine Development against M. tuberculosis

Tuberculosis (TB) is still the leading global cause of death from an infectious bacterial agent. Limiting tuberculosis epidemic spread is therefore an urgent global public health priority. As stated by the WHO, to stop the spread of the disease we need a new vaccine, with better coverage than the current Mycobacterium bovis BCG vaccine. This vaccine was first used in 1921 and, since then, there are still no new licensed tuberculosis vaccines. However, there is extremely active research in the field, with a steep acceleration in the past decades, due to the advance of technologies and more rational vaccine design strategies. This review aims to gather latest updates in vaccine development in the various clinical phases and to underline the contribution of Structural Vaccinology (SV) to the development of safer and effective antigens. In particular, SV and the development of vaccine adjuvants is making the use of subunit vaccines, which are the safest albeit the less antigenic ones, an achievable goal. Indeed, subunit vaccines overcome safety concerns but need to be rationally re-engineered to enhance their immunostimulating effects. The larger availability of antigen structural information as well as a better understanding of the complex host immune response to TB infection is a strong premise for a further acceleration of TB vaccine development.

Host blood-based biosignatures for subclinical TB and incipient TB: A prospective study of adult TB household contacts in Southern India

A large proportion of the global tuberculosis (TB) burden is asymptomatic and not detectable by symptom-based screening, driving the TB epidemic through continued M. tuberculosis transmission. Currently, no validated tools exist to diagnose incipient and subclinical TB. Nested within a large prospective study in household contacts of pulmonary TB cases in Southern India, we assessed 35 incipient TB and 12 subclinical TB cases, along with corresponding household active TB cases (n=11), and household controls (n=39) using high throughput methods for transcriptional and protein profiling. We split the data into training and test sets and applied a support vector machine classifier followed by a Lasso regression model to identify signatures. The Lasso regression model identified an 11-gene signature (ABLIM2, C20orf197, CTC-543D15.3, CTD-2503O16.3, HLADRB3, METRNL, RAB11B-AS1, RP4-614C10.2, RNA5SP345, RSU1P1, and UACA) that distinguished subclinical TB from incipient TB with a very good discriminatory power by AUCs in both training and test sets. Further, we identified an 8-protein signature comprising b-FGF, IFNγ, IL1RA, IL7, IL12p70, IL13, PDGF-BB, and VEGF that differentiated subclinical TB from incipient TB with good and moderate discriminatory power by AUCs in the training and test sets, respectively. The identified 11-gene signature discriminated well between the distinct stages of the TB disease spectrum, with very good discriminatory power, suggesting it could be useful for predicting TB progression in household contacts. However, the high discriminatory power could partly be due to over-fitting, and validation in other studies is warranted to confirm the potential of the immune biosignatures for identifying subclinical TB.

Treatments of Mycobacterium tuberculosis and Toxoplasma gondii with Selenium Nanoparticles

Toxoplasma gondii and Mycobacterium tuberculosis are pathogens that are harmful to humans. When these diseases interact in humans, the result is typically fatal to the public health. Several investigations on the relationship between M. tuberculosis and T. gondii infections have found that there is a strong correlation between them with each infection having a reciprocal effect on the other. TB may contribute to the reactivation of innate toxoplasmosis or enhance susceptibility to a new infection, and toxoplasma co-infection may worsen the severity of pulmonary tuberculosis. As a consequence, there is an earnest and urgent necessity to generate novel therapeutics that can subdue these challenges. Selenium nanostructures' compelling properties have been shown to be a successful treatment for Mycobacterium TB and Toxoplasma gondii. Despite the fact that selenium (Se) offers many health advantages for people, it also has a narrow therapeutic window; therefore, consuming too much of either inorganic or organic compounds based on selenium can be hazardous. Compared to both inorganic and organic Se, Se nanoparticles (SeNPs) are less hazardous. They are biocompatible and excellent in selectively targeting specific cells. As a consequence, this review conducted a summary of the efficacy of biogenic Se NPs in the treatment of tuberculosis (TB) and toxoplasmosis. Mycobacterium tuberculosis, Toxoplasma gondii, and their co-infection were all briefly described.

Kaempferol: Antimicrobial Properties, Sources, Clinical, and Traditional Applications

Flavonoids are a category of plant-derived compounds which exhibit a large number of health-related effects. One of the most well-known and studied flavonoids is kaempferol, which can be found in a wide variety of herbs and plant families. Apart from their anticarcinogenic and anti-inflammatory effects, kaempferol and its associated compounds also exhibit antibacterial, antifungal, and antiprotozoal activities. The development of drugs and treatment schemes based on these compounds is becoming increasingly important in the face of emerging resistance of numerous pathogens as well as complex molecular interactions between various drug therapies. In addition, many of the kaempferol-containing plants are used in traditional systems all over the world for centuries to treat numerous conditions. Due to its variety of sources and associated compounds, some molecular mechanisms of kaempferol antimicrobial activity are well known while others are still under analysis. This paper thoroughly documents the vegetal and food sources of kaempferol as well as the most recent and significant studies regarding its antimicrobial applications.

A patent review on pharmaceutical and therapeutic applications of oxadiazole derivatives for the treatment of chronic diseases (2013-2021)

INTRODUCTION

Oxadiazole is a unique class of heterocycle, possessing numerous important biomedical and therapeutic applications such as anti-bacterial, anti-cancer, anti-inflammatory, inhibitors for diverse enzymes, receptors modulators, and neuroprotective properties. The rapid development in the field of oxadiazole-containing structures is confirmed by the development of numerous clinical drugs such as doxazosin, nesapidil, pleconaril, fasiplon, ataluren, zibotentan, and prenoxdiazine as selected examples.

AREAS COVERED

This review provides a comprehensive overview of the range of biological applications of oxadiazole-containing drugs in a range of patents from 2013 to 2021. The information was collected from available data sources including SciFinder, Reaxys, MedLine, and Chemical Abstracts.

EXPERT OPINION

Oxadiazole is an established class of compounds with fascinating biological properties. The importance of oxadiazoles can be recognized by their enormous application in a wide spectrum of medicinal chemistry from anticancer, antibiotic, and antidiabetic to the use in agriculture and neuroprotection. For instance, the oxadiazole-based compounds have shown the ability to modulate a variety of receptors including the M4 receptor agonists, S1P1 receptor modulators, SSTR5 antagonists, orexin type-2 receptor agonists, liver X receptor agonists, and many more. This testifies to the special features associated with the oxadiazole scaffold making it a significant pharmacophore.

The quest for vaccine-induced immune correlates of protection against tuberculosis

Immunization strategies against tuberculosis (TB) that confer better protection than neonatal vaccination with the 101-year-old Bacille Calmette-Guerin (BCG) are urgently needed to control the epidemic, but clinical development is hampered by a lack of established immune correlates of protection (CoPs). Two phase 2b clinical trials offer the first opportunity to discover human CoPs against TB. Adolescent BCG re-vaccination showed partial protection against Mycobacterium tuberculosis (Mtb) infection, as measured by sustained IFNγ release assay (IGRA) conversion. Adult M72/AS01E vaccination showed partial protection against pulmonary TB. We describe two collaborative research programs to discover CoPs against TB and ensure rigorous, streamlined use of available samples, involving international immunology experts in TB and state-of-the-art technologies, sponsors and funders. Hypotheses covering immune responses thought to be important in protection against TB have been defined and prioritized. A statistical framework to integrate the data analysis strategy was developed. Exploratory analyses will be performed to generate novel hypotheses.

Research Advances for Virus-vectored Tuberculosis Vaccines and Latest Findings on Tuberculosis Vaccine Development

Tuberculosis (TB), caused by respiratory infection with Mycobacterium tuberculosis, remains a major global health threat. The only licensed TB vaccine, the one-hundred-year-old Bacille Calmette-Guérin has variable efficacy and often provides poor protection against adult pulmonary TB, the transmissible form of the disease. Thus, the lack of an optimal TB vaccine is one of the key barriers to TB control. Recently, the development of highly efficacious COVID-19 vaccines within one year accelerated the vaccine development process in human use, with the notable example of mRNA vaccines and adenovirus-vectored vaccines, and increased the public acceptance of the concept of the controlled human challenge model. In the TB vaccine field, recent progress also facilitated the deployment of an effective TB vaccine. In this review, we provide an update on the current virus-vectored TB vaccine pipeline and summarize the latest findings that might facilitate TB vaccine development. In detail, on the one hand, we provide a systematic literature review of the virus-vectored TB vaccines are in clinical trials, and other promising candidate vaccines at an earlier stage of development are being evaluated in preclinical animal models. These research sharply increase the likelihood of finding a more effective TB vaccine in the near future. On the other hand, we provide an update on the latest tools and concept that facilitating TB vaccine research development. We propose that a pre-requisite for successful development may be a better understanding of both the lung-resident memory T cell-mediated mucosal immunity and the trained immunity of phagocytic cells. Such knowledge could reveal novel targets and result in the innovative vaccine designs that may be needed for a quantum leap forward in vaccine efficacy. We also summarized the research on controlled human infection and ultra-low-dose aerosol infection murine models, which may provide more realistic assessments of vaccine utility at earlier stages. In addition, we believe that the success in the ongoing efforts to identify correlates of protection would be a game-changer for streamlining the triage of multiple next-generation TB vaccine candidates. Thus, with more advanced knowledge of TB vaccine research, we remain hopeful that a more effective TB vaccine will eventually be developed in the near future.

Does BCG vaccination protect against infection with M. tuberculosis?

BACKGROUND:

Protection against infection by the bacille Calmette-Guérin vaccine against Mycobacterium tuberculosis remains a subject of controversy. We investigated the association between BCG vaccination at birth and infection by M. tuberculosis.

MATERIAL AND METHODS:

This was a secondary analysis of data from tuberculin skin test (TST) surveys in Vietnamese schoolchildren between 1988 and 2001. We investigated whether a BCG scar was associated with a lower prevalence of TST positivity, adjusting for BCG-induced variation by varying cut-off values for a positive TST.

RESULTS:

We found a positive association between BCG scar and TST positivity. The strength of the association decreased with increasing TST cut-off values; however, it never inverted significantly, irrespective of geographic region and survey year.

CONCLUSION:

In Vietnam, BCG vaccination was not associated with reduced M. tuberculosis infection prevalence as measured using TST. This in contrary to a similar study conducted in Tanzania. These contradictory findings may be explained by geographical differences and the relatively high prevalence in Vietnam of the M. tuberculosis Beijing genotype, which is reported to be capable of circumventing BCG-induced immunity.

Vaccination inducing durable and robust antigen-specific Th1/Th17 immune responses contributes to prophylactic protection against Mycobacterium avium infection but is ineffective as an adjunct to antibiotic treatment in chronic disease

Mycobacterium avium complex (MAC) causing pulmonary disease in humanshas emerged worldwide. Thus, effective strategies simultaneously aiming to prevent MAC infection and accelerate therapeutic efficacy are required. To this end, subunit vaccine-induced protection against a well-defined virulent Mycobacterium avium (Mav) isolate was assessed as a preventative and therapeutic modality in murine models. Mav-derived culture filtrate antigen (CFA) was used as a vaccine antigen with glucopyranosyl lipid A stable emulsion (GLA-SE) or GLA-SE plus cyclic-di-GMP (GLA-SE/CDG), and we compared the immunogenicities, protective efficacies and immune correlates. Interestingly, CFA+GLA-SE/CDG immunization induced greater CFA-specific Th1/Th17 responses in both the lung and spleen than among the tested groups. Consequently, protective efficacy was optimally achieved with CFA+GLA-SE/CDG by significantly reducing bacterial loads along with long-lasting maintenance of antigen-specific Th1/Th17 cytokine-producing multifunctional T cell responses and relevant cytokine productions. Thus, we employed this subunit vaccine as an adjunct to antibiotic treatment. However, this vaccine was ineffective in further reducing bacterial loads. Collectively, our study demonstrates that strong Mav CFA-specific Th1/Th17 responses are critical for preventative protection against Mav infection but may be ineffective or even detrimental in an established and progressive chronic disease, indicating that different approaches to combating Mav infection are necessary according to vaccination purposes.

Accelerating research and development of new vaccines against tuberculosis: a global roadmap

To eliminate tuberculosis globally, a new, effective, and affordable vaccine is urgently needed, particularly for use in adults and adolescents in low-income and middle-income countries. We have created a roadmap that lists the actions needed to accelerate tuberculosis vaccine research and development using a participatory process. The vaccine pipeline needs more diverse immunological approaches, antigens, and platforms. Clinical development can be accelerated by validated preclinical models, agreed laboratory correlates of protection, efficient trial designs, and validated endpoints. Determining the public health impact of new tuberculosis vaccines requires understanding of a country's demand for a new tuberculosis vaccine, how to integrate vaccine implementation with ongoing tuberculosis prevention efforts, cost, and national and global demand to stimulate vaccine production. Investments in tuberculosis vaccine research and development need to be increased, with more diversity of funding sources and coordination between these funders. Open science is important to enhance the efficiency of tuberculosis vaccine research and development including early and freely available publication of study findings and effective mechanisms for sharing datasets and specimens. There is a need for increased engagement of industry vaccine developers, for increased political commitment for new tuberculosis vaccines, and to address stigma and vaccine hesitancy. The unprecedented speed by which COVID-19 vaccines have been developed and introduced provides important insight for tuberculosis vaccine research and development.

Improving Assignments for Therapeutic and Prophylactic Treatment Within TB Households. A Potential for Immuno-Diagnosis?

Delays in diagnosis and treatment of pulmonary tuberculosis (TB) can lead to more severe disease and increased transmission. Contact investigation among household contacts (HHCs) of TB patients is crucial to ensure optimal outcomes. In the context of a prospective cohort study in Palamaner, Southern India, this study attempted to assess the potential of 27 different soluble immune markers to accurately assign HHCs for appropriate treatment. A multiplex bead assay was applied on QuantiFERON (QFT)-nil supernatants collected from 89 HHCs grouped by longitudinal QFT status; M. tuberculosis (Mtb) infected (QFT positive at baseline and follow-up, n = 30), recent QFT converters (QFT-negative at baseline, n = 27) and converted to QFT-positivity within 6 months of exposure (at follow-up, n = 24) and QFT consistent negatives (n = 32). The 29 TB index cases represented Active TB. Active TB cases and HHCs with Mtb infection produced significantly different levels of both pro-inflammatory (IFNγ, IL17, IL8, IP10, MIP-1α, MIP1β, and VEGF) and anti-inflammatory (IL9 and IL1RA) cytokines. We identified a 4-protein signature (bFGF, IFNγ, IL9, and IP10) that correctly classified HHCs with Mtb infection vs. Active TB with a specificity of 92.6%, suggesting that this 4-protein signature has the potential to assign HHCs for either full-length TB treatment or preventive TB treatment. We further identified a 4-protein signature (bFGF, GCSF, IFNγ, and IL1RA) that differentiated HHCs with Mtb infection from QFT consistent negatives with a specificity of 62.5%, but not satisfactory to safely assign HHCs to no preventive TB treatment. QFT conversion, reflecting new Mtb infection, induced an elevated median concentration in nearly two-thirds (19/27) of the analyzed soluble markers compared to the levels measured at baseline. Validation in other studies is warranted in order to establish the potential of the immune biosignatures for optimized TB case detection and assignment to therapeutic and preventive treatment of Mtb infected individuals.

Protein O-mannosyltransferase Rv1002c contributes to low cell permeability, biofilm formation in vitro, and mycobacterial survival in mice

Mycobacterium tuberculosis (M. tuberculosis) Rv1002c encodes the protein O-mannosyltransferase (PMT), which catalyzes the transfer of mannose to serine or threonine residues of proteins. We explored the function of PMT in vitro and in vivo. Rv1002c protein was heterogeneously overexpressed in nonpathogenic Mycobacterium smegmatis (named as MS_Rv1002c). A series of trials including mass spectrometry, transmission electron microscope, biofilm formation and antibiotics susceptibility were performed to explore the function of PMT on bacterial survival in vitro. Mouse experiments were carried out to evaluate the virulence of PMT in vivo. PMT decreased the cell envelope permeability and promoted microbial biofilm formation. PMT enhanced the mycobacterial survival in vivo and inhibited the release of pro-inflammatory cytokines in serum. The function might be associated with an increased abundance of some mannoproteins in culture filtrate (CF). PMT is likely to be involved in mycobacterial survival both in vivo and in vitro due to increasing the mannoproteins abundance in CF.

Recombinant BCGs for tuberculosis and bladder cancer

Bacillus Calmette-Guérin (BCG) vaccine is an attenuated live strain of Mycobacterium bovis. It may be the most widely used vaccine in human history and is the only licensed human tuberculosis (TB) vaccine available. Despite its excellent safety history, a century of use in global vaccination programs, and its significant contribution to reducing TB mortality among children, the efficacy of BCG continues to be disputed due to its incomplete protection against pulmonary TB in adults. Still vaccines offer the best chance to contain the ongoing spread of multi-drug resistance TB and disease dissemination. The development of improved vaccines against TB therefore remains a high global priority. Interestingly, recent studies indicate that genetically modified BCG, or administration of existing BCG through alternate routes, or revaccination, offers improved protection, suggesting that BCG is well poised to make a comeback. Intravesical BCG is also the only approved microbial immunotherapy for any form of cancer, and is the first-line therapy for treatment-naïve non-muscle invasive bladder cancer (NMBIC), which represents a majority of the new bladder cancer cases diagnosed. However, almost a third of patients with NMIBC are either BCG unresponsive or have tumor recurrence, leading to a higher risk of disease progression. With very few advances in intravesical therapy over the past two decades for early-stage disease, and a limited pipeline of therapeutics in Phase 3 or late Phase 2 development, there is a major unmet need for improved intravesical therapies for NMIBC. Indeed, genetically modified candidate BCG vaccines engineered to express molecules that confer stronger protection against pulmonary TB or induce potent anti-tumor immunity in NMIBC have shown promise in both pre-clinical and clinical settings. This review discusses the development of second generation, genetically modified BCG candidates as TB vaccines and as anti-tumor adjuvant therapy for NMIBC.

An integrated computational framework to design a multi-epitopes vaccine against Mycobacterium tuberculosis

Tuberculosis (TB) is a highly contagious disease that mostly affects the lungs and is caused by a bacterial pathogen, Mycobacterium tuberculosis. The associated mortality rate of TB is much higher compared to any other disease and the situation is more worrisome by the rapid emergence of drug resistant strains. Bacillus Calmette-Guerin (BCG) is the only licensed attenuated vaccine available for use in humans however, many countries have stopped its use as it fails to confer protective immunity. Therefore, urgent efforts are required to identify new and safe vaccine candidates that are not only provide high immune protection but also have broad spectrum applicability. Considering this, herein, I performed an extensive computational vaccine analysis to investigate 200 complete sequenced genomes of M. tuberculosis to identify core vaccine candidates that harbor safe, antigenic, non-toxic, and non-allergic epitopes. To overcome literature reported limitations of epitope-based vaccines, I carried out additional analysis by designing a multi-epitopes vaccine to achieve maximum protective immunity as well as to make experimental follow up studies easy by selecting a vaccine that can be easily analyzed because of its favorable physiochemical profile. Based on these analyses, I identified two potential vaccine proteins that fulfill all required vaccine properties. These two vaccine proteins are diacylglycerol acyltransferase and ESAT-6-like protein. Epitopes: DSGGYNANS from diacylglycerol acyltransferase and AGVQYSRAD, ADEEQQQAL, and VSRADEEQQ from ESAT-6-like protein were found to cover all necessary parameters and thus used in a multi-epitope vaccine construct. The designed vaccine is depicting a high binding affinity for different immune receptors and shows stable dynamics and rigorous van der Waals and electrostatic binding energies. The vaccine also simulates profound primary, secondary, tertiary immunoglobulin production as well as high interleukins and interferons count. In summary, the designed vaccine is ideal to be evaluated experimentally to decipher its real biological efficacy in controlling drug resistant infections of M. tuberculosis.

Early IL-10 promotes vasculature-associated CD4+ T cells unable to control Mycobacterium tuberculosis infection

Cytokine-producing CD4⁺ T cells play a crucial role in the control of Mycobacterium tuberculosis infection; however, there is a delayed appearance of effector T cells in the lungs following aerosol infection. The immunomodulatory cytokine IL-10 antagonizes control of M. tuberculosis infection through mechanisms associated with reduced CD4⁺ T cell responses. Here, we show that IL-10 overexpression only before the onset of the T cell response impaired control of M. tuberculosis growth; during chronic infection, IL-10 overexpression reduced the CD4⁺ T cell response without affecting the outcome of infection. IL-10 overexpression early during infection did not, we found, significantly impair the kinetics of CD4⁺ T cell priming and effector differentiation. However, CD4⁺ T cells primed and differentiated in an IL-10–enriched environment displayed reduced expression of CXCR3 and, because they did not migrate into the lung parenchyma, their ability to control infection was limited. Importantly, these CD4⁺ T cells maintained their vasculature phenotype and were unable to control infection, even after adoptive transfer into low IL-10 settings. Together our data support a model wherein, during M. tuberculosis infection, IL-10 acts intrinsically on T cells, impairing their parenchymal migratory capacity and ability to engage with infected phagocytic cells, thereby impeding control of infection.

Identification of Serum Cytokine Biomarkers Associated with Multidrug Resistant Tuberculosis (MDR-TB)

Existing tools (including GeneXpert) for diagnosis of multidrug resistant TB (MDR-TB) have limited utility when sputum samples for microbiological analyses cannot be obtained. There is the need for immunological biomarkers which could serve as putative diagnostic markers of MDR-TB. We measured and compared the serum cytokine levels of inflammatory cytokines (IFN-γ, TNF-α, IL12p70, IL-17A, granzyme B) and anti-inflammatory cytokines (IL-10, IL-6, IL-4) among MDR-TB, drug-susceptible (DS)-TB and healthy controls (no-TB) using the Human Magnetic Luminex Multiplex Immunoassay. Levels of IFN-γ and IL-4 were respectively 1.5 log lower and 1.9 log higher in MDR-TB compared to DS-TB cases. Moreover, IFN-γ, TNF-α, IL-10, IL-6, and IL-4 levels were significantly higher in individuals with MDR-TB and DS-TB cases compared to healthy controls. Pairs of cytokines, IL-4 and IFN-γ (p = 0.019), IL-4 and TNF (p = 0.019), and Granzyme B and TNF-α (p = 0.019), showed significant positive correlation in MDR-TB. Serum cytokine profiles can be exploited for immunodiagnostics, as made evident by the Interferon Gamma Release Assays (IGRAs) for TB infection. Using area under the curve values, no single or multiple cytokine combinations could discriminate between DS- and MDR-TB in this study. Studies with a larger sample size and more cytokines could better address the issue.

Sterilizing immunity: New opportunities for rational TB vaccine design

Recent studies have revealed situations of high-level naturally acquired and vaccine-induced immunity against Mycobacterium tuberculosis in animal models along with examples of significantly protective immunization in humans. These discoveries offer immunologists new opportunities to define effector mechanisms that when triggered by appropriately engineered vaccines could end TB's deadly reign.

Enhancement of CD4+ T Cell Function as a Strategy for Improving Antibiotic Therapy Efficacy in Tuberculosis: Does It Work?

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) remains a major public health problem worldwide due in part to the lack of an effective vaccine and to the lengthy course of antibiotic treatment required for successful cure. Combined immuno/chemotherapeutic intervention represents a major strategy for developing more effective therapies against this important pathogen. Because of the major role of CD4⁺ T cells in containing Mtb infection, augmentation of bacterial specific CD4⁺ T cell responses has been considered as an approach in achieving this aim. Here we present new data from our own research aimed at determining whether boosting CD4⁺ T cell responses can promote antibiotic clearance. In these studies, we first characterized the impact of antibiotic treatment of infected mice on Th1 responses to major Mtb antigens and then performed experiments aimed at sustaining CD4⁺ T cell responsiveness during antibiotic treatment. These included IL-12 infusion, immunization with ESAT-6 and Ag85B immunodominant peptides and adoptive transfer of Th1-polarized CD4⁺ T cells specific for ESAT-6 or Ag85B during the initial month of chemotherapy. These approaches failed to enhance antibiotic clearance of Mtb, indicating that boosting Th1 responses to immunogenic Mtb antigens highly expressed by actively dividing bacteria is not an effective strategy to be used in the initial phase of antibiotic treatment, perhaps because replicating organisms are the first to be eliminated by the drugs. These results are discussed in the context of previously published findings addressing this concept along with possible alternate approaches for harnessing Th1 immunity as an adjunct to chemotherapy.

Emerging progress on diagnosis and treatment of female genital tuberculosis

Female genital tuberculosis (FGTB) is an infection caused by Mycobacterium tuberculosis and usually occurs secondary to pulmonary tuberculosis (TB) through the blood circulation, lymph circulation, or direct spreading from abdominal TB. FGTB is an uncommon type of TB that can destroy genital organs, and lead to menstrual disorders and infertility. The diagnosis of FGTB is often made by detection of acid-fast bacilli under microscopy, culture with endometrial biopsy, or histopathological examination of epithelioid granuloma on a biopsy. A multidrug anti-TB regimen is the major management of FGTB, including rifampicin, isoniazid, pyrazinamide, and ethambutol, while surgery is proposed in more deteriorated cases. However, the conception rate in infertile women with FGTB is still low, even after multidrug anti-TB therapy. Additionally, the risk of complications, such as ectopic pregnancy or miscarriage, remains high. In this review, we summarize the characteristics of FGTB, present current epidemiological data, and focus on its early diagnosis and effective management.

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.

Phase I Trial Evaluating the Safety and Immunogenicity of Candidate TB Vaccine MVA85A, Delivered by Aerosol to Healthy M.tb-Infected Adults

The immunogenicity of the candidate tuberculosis (TB) vaccine MVA85A may be enhanced by aerosol delivery. Intradermal administration was shown to be safe in adults with latent TB infection (LTBI), but data are lacking for aerosol-delivered candidate TB vaccines in this population. We carried out a Phase I trial to evaluate the safety and immunogenicity of MVA85A delivered by aerosol in UK adults with LTBI (NCT02532036). Two volunteers were recruited, and the vaccine was well-tolerated with no safety concerns. Aerosolised vaccination with MVA85A induced mycobacterium- and vector-specific IFN-γ in blood and mycobacterium-specific Th1 cytokines in bronchoalveolar lavage. We identified several important barriers that could hamper recruitment into clinical trials in this patient population. The trial did not show any safety concerns in the aerosol delivery of a candidate viral-vectored TB vaccine to two UK adults with Mycobacterium tuberculosis (M.tb) infection. It also systemically and mucosally demonstrated inducible immune responses following aerosol vaccination. A further trial in a country with higher incidence of LTBI would confirm these findings.

Genetics in the Host-Mycobacterium ulcerans interaction

Buruli ulcer is an emerging infectious disease associated with high morbidity and unpredictable outbreaks. It is caused by Mycobacterium ulcerans, a slow-growing pathogen evolutionarily shaped by the acquisition of a plasmid involved in the production of a potent macrolide-like cytotoxin and by genome rearrangements and downsizing. These events culminated in an uncommon infection pattern, whereby M. ulcerans is both able to induce the initiation of the inflammatory cascade and the cell death of its proponents, as well as to survive within the phagosome and in the extracellular milieu. In such extreme conditions, the host is sentenced to rely on a highly orchestrated genetic landscape to be able to control the infection. We here revisit the dynamics of M. ulcerans infection, drawing parallels from other mycobacterioses and integrating the most recent knowledge on its evolution and pathogenicity in its interaction with the host immune response.