The status of tuberculosis vaccine development

A multistage Sendai virus vaccine incorporating latency-associated antigens induces protection against acute and latent tuberculosis

One-quarter of the world's population is infected with Mycobacterium tuberculosis (Mtb). After initial exposure, more immune-competent persons develop asymptomatic latent tuberculosis infection (LTBI) but not active diseases, creates an extensive reservoir at risk of developing active tuberculosis. Previously, we constructed a novel recombinant Sendai virus (SeV)-vectored vaccine encoding two dominant antigens of Mtb, which elicited immune protection against acute Mtb infection. In this study, nine Mtb latency-associated antigens were screened as potential supplementary vaccine candidate antigens, and three antigens (Rv2029c, Rv2028c, and Rv3126c) were selected based on their immune-therapeutic effect in mice, and their elevated immune responses in LTBI human populations. Then, a recombinant SeV-vectored vaccine, termed SeV986A, that expresses three latency-associated antigens and Ag85A was constructed. In murine models, the doses, titers, and inoculation sites of SeV986A were optimized, and its immunogenicity in BCG-primed and BCG-naive mice were determined. Enhanced immune protection against the Mtb challenge was shown in both acute-infection and latent-infection murine models. The expression levels of several T-cell exhaustion markers were significantly lower in the SeV986A-vaccinated group, suggesting that the expression of latency-associated antigens inhibited the T-cell exhaustion process in LTBI infection. Hence, the multistage quarter-antigenic SeV986A vaccine holds considerable promise as a novel post-exposure prophylaxis vaccine against tuberculosis.

Immune responses induced by Mycobacterium tuberculosis heat-resistant antigen (Mtb-HAg) upon co-administration with Bacillus Calmette-Guérin in mice

OBJECTIVES

To preliminarily assess the immunogenicity of Mtb-HAg in mice and the synergistic effect provided by HAg when co-immunised with BCG.

METHODS

Mice were randomly grouped for different immunisations and then spleens were aseptically removed and lymphocytes were extracted for immediate detection of cytokines transcript levels and stimulation index(SI), cytokine secretion and multifunctional antigen-specific T cells were detected after incubation for different times.

RESULTS

HAg extracted from active Mtb is a group of mixed polypeptides with molecular weights of (10-14) kDa. It can significantly stimulate lymphocytes proliferation and increase SI. Injection of HAg alone and in combination with BCG induced significantly higher numbers of multifunctional antigen-specific T cells including CD4+ IFN-γ+, CD4+ IL-2+, CD8+ IFN-γ+, and CD8+ IL-2+ cells than that in BCG-treated mice. Co-immunisation induced the secretion of higher levels of IFN-γ, TNF-α, IL-2 and IL-4 and increased their mRNA expression levels. Significant increases in the transcription levels of IL-10, IL-12 and IL-17 were observed in the co-immunised group with the assistance of HAg.

CONCLUSION

We demonstrated that HAg has favourable immunogenicity, triggers a stronger Th1-type immune response and proposed the hypothesis that HAg can be used as a BCG booster to further enhance the benefits of BCG.

Phase 1 Open-Label Dose Escalation Trial for the Development of a Human Bacillus Calmette-Guérin Challenge Model for Assessment of Tuberculosis Immunity In Vivo

BACKGROUND

A controlled human infection model for assessing tuberculosis (TB) immunity can accelerate new vaccine development.

METHODS

In this phase 1 dose escalation trial, 92 healthy adults received a single intradermal injection of 2 × 106 to 16 × 106 colony-forming units of Bacillus Calmette-Guérin (BCG). The primary endpoints were safety and BCG shedding as measured by quantitative polymerase chain reaction, colony-forming unit plating, and MGIT BACTEC culture.

RESULTS

Doses up to 8 × 106 were safe, and there was evidence for increased BCG shedding with dose escalation. The MGIT time-to-positivity assay was the most consistent and precise measure of shedding. Power analyses indicated that 10% differences in MGIT time to positivity (area under the curve) could be detected in small cohorts (n = 30). Potential biomarkers of mycobacterial immunity were identified that correlated with shedding. Transcriptomic analysis uncovered dose- and time-dependent effects of BCG challenge and identified a putative transcriptional TB protective signature. Furthermore, we identified immunologic and transcriptomal differences that could represent an immune component underlying the observed higher rate of TB disease incidence in males.

CONCLUSIONS

The safety, reactogenicity, and immunogenicity profiles indicate that this BCG human challenge model is feasible for assessing in vivo TB immunity and could facilitate the vaccine development process.

CLINICAL TRIALS REGISTRATION

NCT01868464 (ClinicalTrials.gov).

Live Attenuated Vaccines against Tuberculosis: Targeting the Disruption of Genes Encoding the Secretory Proteins of Mycobacteria

Tuberculosis (TB), a chronic infectious disease affecting humans, causes over 1.3 million deaths per year throughout the world. The current preventive vaccine BCG provides protection against childhood TB, but it fails to protect against pulmonary TB. Multiple candidates have been evaluated to either replace or boost the efficacy of the BCG vaccine, including subunit protein, DNA, virus vector-based vaccines, etc., most of which provide only short-term immunity. Several live attenuated vaccines derived from Mycobacterium tuberculosis (Mtb) and BCG have also been developed to induce long-term immunity. Since Mtb mediates its virulence through multiple secreted proteins, these proteins have been targeted to produce attenuated but immunogenic vaccines. In this review, we discuss the characteristics and prospects of live attenuated vaccines generated by targeting the disruption of the genes encoding secretory mycobacterial proteins.

High-resolution African HLA resource uncovers HLA-DRB1 expression effects underlying vaccine response

How human genetic variation contributes to vaccine effectiveness in infants is unclear, and data are limited on these relationships in populations with African ancestries. We undertook genetic analyses of vaccine antibody responses in infants from Uganda (n = 1391), Burkina Faso (n = 353) and South Africa (n = 755), identifying associations between human leukocyte antigen (HLA) and antibody response for five of eight tested antigens spanning pertussis, diphtheria and hepatitis B vaccines. In addition, through HLA typing 1,702 individuals from 11 populations of African ancestry derived predominantly from the 1000 Genomes Project, we constructed an imputation resource, fine-mapping class II HLA-DR and DQ associations explaining up to 10% of antibody response variance in our infant cohorts. We observed differences in the genetic architecture of pertussis antibody response between the cohorts with African ancestries and an independent cohort with European ancestry, but found no in silico evidence of differences in HLA peptide binding affinity or breadth. Using immune cell expression quantitative trait loci datasets derived from African-ancestry samples from the 1000 Genomes Project, we found evidence of differential HLA-DRB1 expression correlating with inferred protection from pertussis following vaccination. This work suggests that HLA-DRB1 expression may play a role in vaccine response and should be considered alongside peptide selection to improve vaccine design.

mRNA-based therapeutics: looking beyond COVID-19 vaccines

Recent advances in mRNA technology and its delivery have enabled mRNA-based therapeutics to enter a new era in medicine. The rapid, potent, and transient nature of mRNA-encoded proteins, without the need to enter the nucleus or the risk of genomic integration, makes them desirable tools for treatment of a range of diseases, from infectious diseases to cancer and monogenic disorders. The rapid pace and ease of mass-scale manufacturability of mRNA-based therapeutics supported the global response to the COVID-19 pandemic. Nonetheless, challenges remain with regards to mRNA stability, duration of expression, delivery efficiency, and targetability, to broaden the applicability of mRNA therapeutics beyond COVID-19 vaccines. By learning from the rapidly expanding preclinical and clinical studies, we can optimise the mRNA platform to meet the clinical needs of each disease. Here, we will summarise the recent advances in mRNA technology; its use in vaccines, immunotherapeutics, protein replacement therapy, and genomic editing; and its delivery to desired specific cell types and organs for development of a new generation of targeted mRNA-based therapeutics.

Mtb HLA-E-tetramer-sorted CD8+ T cells have a diverse TCR repertoire

HLA-E molecules can present self- and pathogen-derived peptides to both natural killer (NK) cells and T cells. T cells that recognize HLA-E peptides via their T cell receptor (TCR) are termed donor-unrestricted T cells due to restricted allelic variation of HLA-E. The composition and repertoire of HLA-E TCRs is not known so far. We performed TCR sequencing on CD8+ T cells from 21 individuals recognizing HLA-E tetramers (TMs) folded with two Mtb-HLA-E-restricted peptides. We sorted HLA-E Mtb TM+ and TM- CD8+ T cells directly ex vivo and performed bulk RNA-sequencing and single-cell TCR sequencing. The identified TCR repertoire was diverse and showed no conservation between and within individuals. TCRs selected from our single-cell TCR sequencing data could be activated upon HLA-E/peptide stimulation, although not robust, reflecting potentially weak interactions between HLA-E peptide complexes and TCRs. Thus, HLA-E-Mtb-specific T cells have a highly diverse TCR repertoire.

Exploring the immunogenicity of Rv2201-519: A T-cell epitope-based antigen derived from Mycobacterium tuberculosis AsnB with implications for tuberculosis infection detection and vaccine development

Research dedicated to diagnostic reagents and vaccine development for tuberculosis (TB) is challenging due to the paucity of immunodominant antigens that can predict disease risk and exhibit protective potential. Therefore, it is crucial to identify T-cell epitope-based Mycobacterium tuberculosis (MTB) antigens characterized by specific and prominent recognition by the immune system. In this study, we constructed a T-cell epitope-rich tripeptide-splicing fragment (nucleotide positions 131-194, 334-377, and 579-643) of Rv2201 (also known as the 72 kDa AsnB)from the MTB genome, ultimately yielding the recombinant protein Rv2201-519 in Escherichia coli BL21 (DE3). Subsequently, we gauged the recombinant protein's ability to detect tuberculosis infection through ELISpot and assessed its immunostimulatory effect on mouse models using flow cytometry and ELISA. Our results indicated that Rv2201-519 possessed promising sensitivity; however, the sensitivity was lower than that of a commercial diagnostic kit containing ESAT-6, CFP-10, and Rv3615c (80.56 % vs. 94.44 %). The Rv2201-519 group exhibited a propensity for a CD4+ Th1 cell immune response in inoculated BALB/c mice that manifested as higher levels of antigen-specific IgG production (IgG2a/IgG1 > 1). In comparison to Ag85B, Rv2201-519 induced a more robust Th1-type cellular immune response as evidenced by a notable rise in the ratio of IFN-γ/IL-4 and IL-12 cytokine production and increased CD4+ T cell activation with a higher percentage of CD4+IFN-γ+ T cells. Rv2201-519 also induced a higher level of IL-6 compared with Ag85B, a higher percentage of CD8+ T cells specific for Rv2201-519, and a lower percentage of CD8+IL-4+ T cells. Collectively, the current evidence suggests that Rv2201-519 could potentially serve as an immunodominant protein for tuberculosis infection screening, laying the groundwork for further evaluation in recombinant Bacillus Calmette-Guérin (BCG) and subunit vaccines against MTB challenges in future studies.

The role of Bach2 in regulating CD8 + T cell development and function

Bach2 was initially discovered in B cells, where it was revealed to control the transcription involved in cell differentiation. Bach2 is intimately connected to CD8 + T lymphocytes in various differentiation states and subsets according to recent findings. Bach2 can regulate primitive T cells, stimulate the development and differentiation of memory CD8 + T cells, inhibit the differentiation of effector CD8 + T cells, and play a significant role in the exhaustion of CD8 + T cells. The appearance and development of diseases are tightly linked to irregular CD8 + T cell differentiation and function. Accordingly, Bach2 offers novel approaches and possible targets for the clinical treatment of associated disorders based on research on these pathways. Here, we summarize the role of Bach2 in the function and differentiation of CD8 + T cells and its potential clinical applications.

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.

Lung IL-17A-Producing CD4+ T Cells Correlate with Protection after Intrapulmonary Vaccination with Differentially Adjuvanted Tuberculosis Vaccines

Tuberculosis (TB), caused by Mycobacterium tuberculosis, results in approximately 1.6 million deaths annually. BCG is the only TB vaccine currently in use and offers only variable protection; however, the development of more effective vaccines is hindered by a lack of defined correlates of protection (CoP) against M. tuberculosis. Pulmonary vaccine delivery is a promising strategy since it may promote lung-resident immune memory that can respond rapidly to respiratory infection. In this study, CysVac2, a subunit protein previously shown to be protective against M. tuberculosis in mouse models, was combined with either Advax® adjuvant or a mixture of alum plus MPLA and administered intratracheally into mice. Peripheral immune responses were tracked longitudinally, and lung-local immune responses were measured after challenge. Both readouts were then correlated with protection after M. tuberculosis infection. Although considered essential for the control of mycobacteria, induction of IFN-γ-expressing CD4+ T cells in the blood or lungs did not correlate with protection. Instead, CD4+ T cells in the lungs expressing IL-17A correlated with reduced bacterial burden. This study identified pulmonary IL-17A-expressing CD4+ T cells as a CoP against M. tuberculosis and suggests that mucosal immune profiles should be explored for novel CoP.

Berlin nodules: About 3 cases

INTRODUCTION

Granulomatous uveitis is mainly defined by the nature of keratic precipitates and iris nodules. Anterior chamber (AC) granulomas, also known as Berlin nodules (BN), are circumscribed granulomatous nodules that form in the iridocorneal angle (ICA) in response to intraocular inflammation.

CASES DESCRIPTION

We present three representative cases of anterior uveitis with berlin nodules to insist on the clinical features of this entity. Case 1: A female adult was referred to our department for bilateral redness and gradual blurry vision. Slit-lamp examination of both eyes (OU) found a yellow-white nodular mass at 6 o'clock on the peripheral iris with irido-crystalline synechiae, vitreous haze and blurred fundus. Purified protein derivative skin test revealed an induration of 20 mm. A diagnosis of presumed ocular tuberculosis was made. The patient received antituberculosis drugs and steroids with good evolution. Case 2: An 11-year-old girl presented for redness and pain OU. Anterior segment examination showed circumciliary congestion, epithelial microcystic edema OU and pearly vascularized lesion against the cornea in the right eye. Fundus examination was unremarkable. A diagnosis of definite ocular sarcoidosis was made based on accessory salivary glands biopsy. The patient was treated with teroids and controlled twice a week. Case 3: A 26-year-old male presented with a redness and pain of the left eye. The slit-lamp examination showed fine keratic precipitates with pearly white nodules within the AC. Fundus examination showed a chorioretinal lesion and occlusive vasculitis. Chest CT was consistent with milliary tuberculosis. Adequate therapy was initiated with favorable outcome.

CONCLUSION

BN can be associated with various ocular manifestations of several diseases. They may be the first manifestation of systemic conditions and seem to be well managed with topical steroids.

Push forward LC-MS-based therapeutic drug monitoring and pharmacometabolomics for anti-tuberculosis precision dosing and comprehensive clinical management

The spread of tuberculosis (TB), especially multidrug-resistant TB and extensively drug-resistant TB, has strongly motivated the research and development of new anti-TB drugs. New strategies to facilitate drug combinations, including pharmacokinetics-guided dose optimization and toxicology studies of first- and second-line anti-TB drugs have also been introduced and recommended. Liquid chromatography-mass spectrometry (LC-MS) has arguably become the gold standard in the analysis of both endo- and exo-genous compounds. This technique has been applied successfully not only for therapeutic drug monitoring (TDM) but also for pharmacometabolomics analysis. TDM improves the effectiveness of treatment, reduces adverse drug reactions, and the likelihood of drug resistance development in TB patients by determining dosage regimens that produce concentrations within the therapeutic target window. Based on TDM, the dose would be optimized individually to achieve favorable outcomes. Pharmacometabolomics is essential in generating and validating hypotheses regarding the metabolism of anti-TB drugs, aiding in the discovery of potential biomarkers for TB diagnostics, treatment monitoring, and outcome evaluation. This article highlighted the current progresses in TDM of anti-TB drugs based on LC-MS bioassay in the last two decades. Besides, we discussed the advantages and disadvantages of this technique in practical use. The pressing need for non-invasive sampling approaches and stability studies of anti-TB drugs was highlighted. Lastly, we provided perspectives on the prospects of combining LC-MS-based TDM and pharmacometabolomics with other advanced strategies (pharmacometrics, drug and vaccine developments, machine learning/artificial intelligence, among others) to encapsulate in an all-inclusive approach to improve treatment outcomes of TB patients.

The functions and applications of extracellular vesicles derived from Mycobacterium tuberculosis

Extracellular vesicles (EVs) originating from bacteria function critical roles in bacterial biologic physiology and host-pathogen interactions. Mycobacterium tuberculosis (M. tuberculosis) produces EVs both in vitro and in vivo, with membrane-bound nanoparticles facilitating the transmission of biological molecules including lipids, proteins, nucleic acids and glycolipids, while interacting remotely with the host. Although studies of EVs in mycobacterial infections is still in its infancy, it has already revealed an entirely new aspect of M. tuberculosis-host interactions that may have implications for tuberculosis (TB) pathogenesis. In this review, we discuss the significant functions of M. tuberculosis EVs in elucidating the mechanisms underlying vesicle biogenesis and modulating cellular immune responses, as well as the recent advances and challenges in the development of novel preventive and therapeutic or diagnostic strategies against TB.

Recent advance in the development of tuberculosis vaccines in clinical trials and virus-like particle-based vaccine candidates

Tuberculosis (TB) remains a serious public health threat around the world. An effective vaccine is urgently required for cost-effective, long-term control of TB. However, the only licensed vaccine Bacillus Calmette-Guerin (BCG) is limited to prevent TB for its highly variable efficacy. Substantial progress has been made in research and development (R&D) of TB vaccines in the past decades, and a dozen vaccine candidates, including live attenuated mycobacterial vaccines, killed mycobacterial vaccines, adjuvanted subunit vaccines, viral vector vaccines, and messenger RNA (mRNA) vaccines were developed in clinical trials to date. Nevertheless, many challenges to the successful authorization for the use and deployment of an effective tuberculosis vaccine remain. Therefore, it is still necessary and urgent to continue exploring new vaccine construction approaches. Virus-like particles (VLPs) present excellent prospects in the field of vaccine development because of their helpful immunological features such as being safe templates without containing viral nucleic acid, repetitive surface geometry, conformational epitopes similar to natural viruses, and enhancing both innate and adaptive immune responses. The marketization process of VLP vaccines has never stopped despite VLP vaccines face several shortcomings such as their complex and slow development process and high production cost, and several VLP-based vaccines, including vaccines against Human papillomavirus (HPV), Hepatitis B Virus (HBV) and malaria, are successfully licensed for use at the market. In this review, we provide an update on the current progress regarding the development of TB vaccines in clinical trials and seek to give an overview of VLP-based TB vaccine candidates.

Assessing vaccine-mediated protection in an ultra-low dose Mycobacterium tuberculosis murine model

Despite widespread immunization with Bacille-Calmette-Guérin (BCG), the only currently licensed tuberculosis (TB) vaccine, TB remains a leading cause of mortality globally. There are many TB vaccine candidates in the developmental pipeline, but the lack of a robust animal model to assess vaccine efficacy has hindered our ability to prioritize candidates for human clinical trials. Here we use a murine ultra-low dose (ULD) Mycobacterium tuberculosis (Mtb) challenge model to assess protection conferred by BCG vaccination. We show that BCG confers a reduction in lung bacterial burdens that is more durable than that observed after conventional dose challenge, curbs Mtb dissemination to the contralateral lung, and, in a small percentage of mice, prevents detectable infection. These findings are consistent with the ability of human BCG vaccination to mediate protection, particularly against disseminated disease, in specific human populations and clinical settings. Overall, our findings demonstrate that the ultra-low dose Mtb infection model can measure distinct parameters of immune protection that cannot be assessed in conventional dose murine infection models and could provide an improved platform for TB vaccine testing.

Construction and evaluation of a novel multi-antigenic Mycobacterium tuberculosis subunit vaccine candidate BfrB-GrpE/DPC

Tuberculosis poses a significant threat to human health due to the lack of an effective vaccine. Although promising progress has been made in the development of tuberculosis vaccines, new vaccines that broaden the antigenic repertoire need to be developed to eradicate this illness. In this study, we used Mycobacterium tuberculosis ferritin BfrB and heat-shock protein GrpE to construct a novel multi-antigenic fusion protein, BfrB-GrpE (BG). BG protein was stably overexpressed in the soluble form in Escherichia coli at a high yield and purified via sequential salt fractionation and hydrophobic chromatography. Purified BG was emulsified in an adjuvant containing N, N'-dimethyl-N, N'-dioctadecylammonium bromide, polyinosinic-polycytidylic acid, and cholesterol (DPC) to construct the BG/DPC vaccine, which stimulated strong cellular and humoral immune responses in mice. Moreover, combination of BG with our previously developed vaccine, Mtb10.4-HspX (MH), containing antigens from both the proliferating and dormant stages, significantly reduced the bacterial counts in the lungs and spleens of M. tuberculosis-infected mice. Importantly, mice that received BG + MH/DPC after M. tuberculosis H37Rv infection survived slightly better (100% survival) than those that received the BCG vaccine (80% survival), although the difference was not statistically significant. Our findings can aid in the selection of antigens and optimization of vaccination regimens to improve the efficacy of tuberculosis vaccines.

Vaccination with mycobacterial lipid loaded nanoparticle leads to lipid antigen persistence and memory differentiation of antigen-specific T cells

Mycobacterium tuberculosis (Mtb) infection elicits both protein and lipid antigen-specific T cell responses. However, the incorporation of lipid antigens into subunit vaccine strategies and formulations has been underexplored, and the characteristics of vaccine-induced Mtb lipid-specific memory T cells have remained elusive. Mycolic acid (MA), a major lipid component of the Mtb cell wall, is presented by human CD1b molecules to unconventional T cell subsets. These MA-specific CD1b-restricted T cells have been detected in the blood and disease sites of Mtb-infected individuals, suggesting that MA is a promising lipid antigen for incorporation into multicomponent subunit vaccines. In this study, we utilized the enhanced stability of bicontinuous nanospheres (BCN) to efficiently encapsulate MA for in vivo delivery to MA-specific T cells, both alone and in combination with an immunodominant Mtb protein antigen (Ag85B). Pulmonary administration of MA-loaded BCN (MA-BCN) elicited MA-specific T cell responses in humanized CD1 transgenic mice. Simultaneous delivery of MA and Ag85B within BCN activated both MA- and Ag85B-specific T cells. Notably, pulmonary vaccination with MA-Ag85B-BCN resulted in the persistence of MA, but not Ag85B, within alveolar macrophages in the lung. Vaccination of MA-BCN through intravenous or subcutaneous route, or with attenuated Mtb likewise reproduced MA persistence. Moreover, MA-specific T cells in MA-BCN-vaccinated mice differentiated into a T follicular helper-like phenotype. Overall, the BCN platform allows for the dual encapsulation and in vivo activation of lipid and protein antigen-specific T cells and leads to persistent lipid depots that could offer long-lasting immune responses.

The Use of Viral Vectors for Gene Therapy and Vaccination in Tuberculosis

Tuberculosis (TB), an infection caused by Mycobacterium tuberculosis (Mtb), is one of the primary causes of death globally. The treatment of TB is long and based on several drugs, producing problems in compliance and toxicity, increasing Mtb resistance to first-line antibiotics that result in multidrug-resistant TB and extensively drug-resistant TB. Thus, the need for new anti-TB treatments has increased. Here, we review some model strategies to study gene therapy based on the administration of a recombinant adenovirus that encodes diverse cytokines, such as IFNγ, IL12, GM/CSF, OPN, TNFα, and antimicrobial peptides to enhance the protective immune response against Mtb. These models include a model of progressive pulmonary TB, a model of chronic infection similar to latent TB, and a murine model of pulmonary Mtb transmission to close contacts. We also review new vaccines that deliver Mtb antigens via particle- or virus-based vectors and trigger protective immune responses. The results obtained in this type of research suggest that this is an alternative therapy that has the potential to treat active TB as an adjuvant to conventional antibiotics and a promising preventive treatment for latent TB reactivation and Mtb transmission. Moreover, Ad vector vaccines are adequate for preventing infectious diseases, including TB.

Advances in protein subunit vaccines against tuberculosis

Tuberculosis (TB), also known as the "White Plague", is caused by Mycobacterium tuberculosis (Mtb). Before the COVID-19 epidemic, TB had the highest mortality rate of any single infectious disease. Vaccination is considered one of the most effective strategies for controlling TB. Despite the limitations of the Bacille Calmette-Guérin (BCG) vaccine in terms of protection against TB among adults, it is currently the only licensed TB vaccine. Recently, with the evolution of bioinformatics and structural biology techniques to screen and optimize protective antigens of Mtb, the tremendous potential of protein subunit vaccines is being exploited. Multistage subunit vaccines obtained by fusing immunodominant antigens from different stages of TB infection are being used both to prevent and to treat TB. Additionally, the development of novel adjuvants is compensating for weaknesses of immunogenicity, which is conducive to the flourishing of subunit vaccines. With advances in the development of animal models, preclinical vaccine protection assessments are becoming increasingly accurate. This review summarizes progress in the research of protein subunit TB vaccines during the past decades to facilitate the further optimization of protein subunit vaccines that may eradicate TB.

Modeling of MT. P495, an mRNA-based vaccine against the phosphate-binding protein PstS1 of Mycobacterium tuberculosis

Tuberculosis (TB) is a contagious disease that predominantly affects the lungs, but can also spread to other organs via the bloodstream. TB affects about one-fourth population of the world. With age, the effectiveness of Bacillus Calmette-Guérin (BCG), the only authorized TB vaccine, decreases. In the quest for a prophylactic and immunotherapeutic vaccine, in this study, a hypothetical mRNA vaccine is delineated, named MT. P495, implementing in silico and immunoinformatics approaches to evaluate key aspects and immunogenic epitopes across the PstS1, a highly conserved periplasmic protein of Mycobacterium tuberculosis (Mtb). PstS1 elicited the potential to generate 99.9% population coverage worldwide. The presence of T- and B-cell epitopes across the PstS1 protein were validated using several computational prediction tools. Molecular docking and dynamics simulation confirmed stable epitope-allele interaction. Immune cell response to the antigen clearance rate was verified by the in silico analysis of immune simulation. Codon optimization confirmed the efficient translation of the mRNA in the host cell. With Toll-like receptors, the vaccine exhibited stable and strong interactions. Findings suggest that the MT. P495 vaccine probably will elicit specific immune responses against Mtb. This mRNA vaccine model is a ready source for further wet-lab validation to confirm the efficacy of this proposed vaccine candidate.

Vaccination with mycobacterial lipid loaded nanoparticle leads to lipid antigen persistence and memory differentiation of antigen-specific T cells

Mycobacterium tuberculosis (Mtb) infection elicits both protein and lipid antigen-specific T cell responses. However, the incorporation of lipid antigens into subunit vaccine strategies and formulations has been underexplored, and the characteristics of vaccine-induced Mtb lipid-specific memory T cells have remained elusive. Mycolic acid (MA), a major lipid component of the Mtb cell wall, is presented by human CD1b molecules to unconventional T cell subsets. These MA-specific CD1b-restricted T cells have been detected in the blood and disease sites of Mtb-infected individuals, suggesting that MA is a promising lipid antigen for incorporation into multicomponent subunit vaccines. In this study, we utilized the enhanced stability of bicontinuous nanospheres (BCN) to efficiently encapsulate MA for in vivo delivery to MA-specific T cells, both alone and in combination with an immunodominant Mtb protein antigen (Ag85B). Pulmonary administration of MA-loaded BCN (MA-BCN) elicited MA-specific T cell responses in humanized CD1 transgenic mice. Simultaneous delivery of MA and Ag85B within BCN activated both MA- and Ag85B-specific T cells. Notably, pulmonary vaccination with MA-Ag85B-BCN resulted in the persistence of MA, but not Ag85B, within alveolar macrophages in the lung. Vaccination of MA-BCN through intravenous or subcutaneous route, or with attenuated Mtb likewise reproduced MA persistence. Moreover, MA-specific T cells in MA-BCN-vaccinated mice differentiated into a T follicular helper-like phenotype. Overall, the BCN platform allows for the dual encapsulation and in vivo activation of lipid and protein antigen-specific T cells and leads to persistent lipid depots that could offer long-lasting immune responses.

Assessing vaccine-mediated protection in an ultra-low dose Mycobacterium tuberculosis murine model

Despite widespread immunization with Bacille-Calmette-Guerin (BCG), the only currently licensed tuberculosis (TB) vaccine, TB remains a leading cause of mortality globally. There are many TB vaccine candidates in the developmental pipeline, but the lack of a robust animal model to assess vaccine efficacy has hindered our ability to prioritize candidates for human clinical trials. Here we use a murine ultra-low dose (ULD) Mycobacterium tuberculosis (Mtb) challenge model to assess protection conferred by BCG vaccination. We show that BCGconfers a reduction in lung bacterial burdens that is more durable than that observed afterconventional dose challenge, curbs Mtb dissemination to the contralateral lung, and, in a smallpercentage of mice, prevents detectable infection. These findings are consistent with the ability of human BCG vaccination to mediate protection, particularly against disseminated disease, in specific human populations and clinical settings. Overall, our findings demonstrate that the ultra-low dose Mtb infection model can measure distinct parameters of immune protection that cannot be assessed in conventional dose murine infection models and could provide an improved platform for TB vaccine testing.

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.

Vaccines against Tuberculosis: Where Are We Now?

Tuberculosis (TB) is among the top 10 leading causes of death in low-income countries. Statistically, TB kills more than 30,000 people each week and leads to more deaths than any other infectious disease, such as acquired immunodeficiency syndrome (AIDS) and malaria. TB treatment is largely dependent on BCG vaccination and impacted by the inefficacy of drugs, absence of advanced vaccines, misdiagnosis improper treatment, and social stigma. The BCG vaccine provides partial effectiveness in demographically distinct populations and the prevalence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB incidences demands the design of novel TB vaccines. Various strategies have been employed to design vaccines against TB, such as: (a) The protein subunit vaccine; (b) The viral vector vaccine; (c) The inactivation of whole-cell vaccine, using related mycobacteria, (d) Recombinant BCG (rBCG) expressing Mycobacterium tuberculosis (M.tb) protein or some non-essential gene deleted BCG. There are, approximately, 19 vaccine candidates in different phases of clinical trials. In this article, we review the development of TB vaccines, their status and potential in the treatment of TB. Heterologous immune responses generated by advanced vaccines will contribute to long-lasting immunity and might protect us from both drug-sensitive and drug-resistant TB. Therefore, advanced vaccine candidates need to be identified and developed to boost the human immune system against TB.

Immunogenicity and efficacy analyses of EPC002, ECA006, and EPCP009 protein subunit combinations as tuberculosis vaccine candidates

Tuberculosis (TB) is the leading cause of death from infectious diseases worldwide, and developing a new TB vaccine is a priority for TB control. Combining multiple immunodominant antigens to form a novel multicomponent vaccine with broad-spectrum antigens to induce protective immune responses is a trend in TB vaccine development. In this study, we used T-cell epitope-rich protein subunits to construct three antigenic combinations: EPC002, ECA006, and EPCP009. Fusion expression of purified protein EPC002f (CFP-10-linker-ESAT-6-linker-nPPE18), ECA006f (CFP-10-linker-ESAT-6-linker-Ag85B), and EPCP009f (CFP-10-linker-ESAT-6-linker-nPPE18-linker-nPstS1) and recombinant purified protein mixtures EPC002m (mix of CFP-10, ESAT-6, and nPPE18), ECA006m (mix of CFP-10, ESAT-6, and Ag85B), and EPCP009m (mix of CFP-10, ESAT-6, nPPE18, and nPstS1) were used as antigens, formulated with alum adjuvant, and the immunogenicity and efficacy were analyzed using immunity experiments with BALB/c mice. All protein-immunized groups elicited higher levels of humoral immunity, including IgG and IgG1. The IgG2a/IgG1 ratio of the EPCP009m-immunized group was the highest, followed by that of the EPCP009f-immunized group, which was significantly higher than the ratios of the other four groups. The multiplex microsphere-based cytokine immunoassay revealed that EPCP009f and EPCP009m induced the production of a wider range of cytokines than EPC002f, EPC002m, ECA006f, and ECA006m, which included Th1-type (IL-2, IFN-γ, TNF-α), Th2-type (IL-4, IL-6, IL-10), Th17-type (IL-17), and other proinflammatory cytokines (GM-CSF, IL-12). The enzyme-linked immunospot assays demonstrated that the EPCP009f- and EPCP009m-immunized groups had significantly higher amounts of IFN-γ than the other four groups. The in vitro mycobacterial growth inhibition assay demonstrated that EPCP009m inhibited Mycobacterium tuberculosis (Mtb) growth most strongly, followed by EPCP009f, which was significantly better than that of the other four vaccine candidates. These results indicated that EPCP009m containing four immunodominant antigens exhibited better immunogenicity and Mtb growth inhibition in vitro and may be a promising candidate vaccine for the control of TB.

PP19128R, a Multiepitope Vaccine Designed to Prevent Latent Tuberculosis Infection, Induced Immune Responses In Silico and In Vitro Assays

Background: Latent tuberculosis infection (LTBI) is the primary source of active tuberculosis (ATB), but a preventive vaccine against LTBI is lacking. Methods: In this study, dominant helper T lymphocyte (HTL), cytotoxic T lymphocyte (CTL), and B-cell epitopes were identified from nine antigens related to LTBI and regions of difference (RDs). These epitopes were used to construct a novel multiepitope vaccine (MEV) based on their antigenicity, immunogenicity, sensitization, and toxicity. The immunological characteristics of the MEV were analyzed with immunoinformatics technology and verified by enzyme-linked immunospot assay and Th1/Th2/Th17 cytokine assay in vitro. Results: A novel MEV, designated PP19128R, containing 19 HTL epitopes, 12 CTL epitopes, 8 B-cell epitopes, toll-like receptor (TLR) agonists, and helper peptides, was successfully constructed. Bioinformatics analysis showed that the antigenicity, immunogenicity, and solubility of PP19128R were 0.8067, 9.29811, and 0.900675, respectively. The global population coverage of PP19128R in HLA class I and II alleles reached 82.24% and 93.71%, respectively. The binding energies of the PP19128R-TLR2 and PP19128R-TLR4 complexes were -1324.77 kcal/mol and -1278 kcal/mol, respectively. In vitro experiments showed that the PP19128R vaccine significantly increased the number of interferon gamma-positive (IFN-γ⁺) T lymphocytes and the levels of cytokines, such as IFN-γ, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-10. Furthermore, positive correlations were observed between PP19128R-specific cytokines in ATB patients and individuals with LTBI. Conclusions: The PP19128R vaccine is a promising MEV with excellent antigenicity and immunogenicity and no toxicity or sensitization that can induce robust immune responses in silico and in vitro. This study provides a vaccine candidate for the prevention of LTBI in the future.

Virus-like Magnetic Mesoporous Silica Particles as a Universal Vaccination Platform against Pathogenic Infections

Vaccination is the most important way of population protection from life-threatening pathogenic infections. However, its efficiency is frequently compromised by a failure of strong antigen presentation and immune activation. Herein, we developed virus-like magnetic mesoporous silica nanoparticles as a universal vaccination platform (termed MagParV) for preventing pathogenic infections. This platform was constructed by integrating synthetic biology-based endoplasmic reticulum-targeting vesicles with magnetic mesoporous silica particles. This platform exhibited high antigen-loading capacity, strongly targeting the endoplasmic reticulum and promoting antigen presentation in dendritic cells. After prime-boost vaccination, the antigen-loading MagParV with AMF drastically elicited specific antibody production against corresponding antigens of fungal, bacterial, and viral pathogens. A systemic infection model further revealed that the platform effectively protected the mice from severe fungal systemic infections. This study realized synthetic biology-facilitated green manufacturing of vaccines, which is promising for magnetism-activated vaccination against different kinds of pathogenic infections.

Combination of Circulating Cell-Free DNA and Positron Emission Tomography to Distinguish Non-Small Cell Lung Cancer from Tuberculosis

OBJECTIVE

Non-small cell lung cancer (NSCLC) holds high metabolic tumor burden and circulating cell-free DNA (cfDNA) levels, and the relationship between metabolic tumor burden and cfDNA in NSCLC and the underlying mechanism of their interaction therein remain poorly characterized. Our aim was to evaluate the clinical value of cfDNA and metabolic tumor burden by positron emission tomography-computed tomography (PET/CT) for NSCLC differential diagnosis from tuberculosis in patients with solitary pulmonary nodules.

METHODS

Metabolic tumor burden values in humans (subjects with NSCLC, subjects with tuberculosis, and healthy control subjects) and relevant mouse models were detected by preoperative 18F-fluorodeoxyglucose PET (18F-FDG PET/CT) and [3H]-2-deoxy-DG uptake, respectively. The cfDNA levels were detected by quantifying serum cfDNA fragments from the ALU (115 bp) gene using reverse transcription-polymerase chain reaction. RNA sequence was performed to determine the underlying target genes and knocked down or inhibited the target genes in vivo and in vitro to determine the mechanism therein.

RESULTS

Metabolic tumor burden correlated with serum cfDNA levels in NSCLC subjects but not in tuberculosis subjects or healthy controls. Mouse models showed a similar phenomenon. In addition, the RNA sequence showed that glucose transporter 1 (GLU1), factor-related apoptosis ligand (FasL), caspase 8, and caspase 3 were significantly increased in NSCLC mouse tumors compared with those in tuberculosis mouse masses. Inhibiting the metabolic tumor burden by blocking or knocking down GLU1 markedly reduced the expression of FasL, the phosphorylation of caspase 8/caspase 3, and serum cfDNA levels/apoptosis percentage in vivo and in vitro. Furthermore, the use of a combination of cfDNA and metabolic tumor burden allowed better ability to distinguish NSCLC subjects from those with tuberculosis or healthy controls than either method used alone.

CONCLUSION

Metabolic tumor burden promotes the formation of circulating cfDNA through GLU1-mediated apoptosis in NSCLC, and the combination of cfDNA and metabolic tumor burden could be valuable for distinguishing NSCLC from tuberculosis.

Safety and immunogenicity of a thermostable ID93 + GLA-SE tuberculosis vaccine candidate in healthy adults

Adjuvant-containing subunit vaccines represent a promising approach for protection against tuberculosis (TB), but current candidates require refrigerated storage. Here we present results from a randomized, double-blinded Phase 1 clinical trial (NCT03722472) evaluating the safety, tolerability, and immunogenicity of a thermostable lyophilized single-vial presentation of the ID93 + GLA-SE vaccine candidate compared to the non-thermostable two-vial vaccine presentation in healthy adults. Participants were monitored for primary, secondary, and exploratory endpoints following intramuscular administration of two vaccine doses 56 days apart. Primary endpoints included local and systemic reactogenicity and adverse events. Secondary endpoints included antigen-specific antibody (IgG) and cellular immune responses (cytokine-producing peripheral blood mononuclear cells and T cells). Both vaccine presentations are safe and well tolerated and elicit robust antigen-specific serum antibody and Th1-type cellular immune responses. Compared to the non-thermostable presentation, the thermostable vaccine formulation generates greater serum antibody responses (p < 0.05) and more antibody-secreting cells (p < 0.05). In this work, we show the thermostable ID93 + GLA-SE vaccine candidate is safe and immunogenic in healthy adults.

Advances in development of new tuberculosis vaccines

PURPOSE OF REVIEW

Tuberculosis (TB) remains a global public health emergency and caused 1.6 million deaths in 2021. The aim of this review is to provide recent updates on advances in TB vaccine development for prevention and adjunct therapy.

RECENT FINDINGS

Targets use indications guiding late stage TB vaccine development have been established, namely: (i) Prevention of disease (PoD), (ii) Prevention of recurrent disease (PoR), (iii) Prevention of established infection in previously uninfected patients (PoI), and (iv) Adjunctive immunotherapy. Novel approaches include vaccines designed to induce immune responses beyond established CD4+, Th1-biased T cell immunity, novel animal models for use in challenge/protection studies, and controlled human infection models to generate vaccine efficacy data.

SUMMARY

Recent efforts at developing effective TB vaccines for prevention and adjunct treatment utilising new targets and technologies have yielded 16 candidate vaccines demonstrating proof of concept for inducing potentially protective immune responses to TB which is currently under evaluation in different stages of clinical trials.

Antibodies Targeting the Cell Wall Induce Protection against Virulent Mycobacterium bovis Infection

Accumulating evidence indicates that antibodies can protect against some intracellular pathogens. Mycobacterium bovis is an intracellular bacterium, and its cell wall (CW) is essential for its virulence and survival. However, the questions of whether antibodies play a protective role in immunity against M. bovis infection and what effects antibodies specific to the CW of M. bovis have still remain unclear. Here, we report that antibodies targeting the CW of an isolated pathogenic M. bovis strain and that of an attenuated bacillus Calmette-Guérin (BCG) strain could induce protection against virulent M. bovis infection in vitro and in vivo. Further research found that the antibody-induced protection was mainly achieved by promoting Fc gamma receptor (FcγR)-mediated phagocytosis, inhibiting bacterial intracellular growth, and enhancing the fusion of phagosomes and lysosomes, and it also depended on T cells for its efficacy. Additionally, we analyzed and characterized the B-cell receptor (BCR) repertoires of CW-immunized mice via next-generation sequencing. CW immunization stimulated BCR changes in the complementarity determining region 3 (CDR3) isotype distribution, gene usage, and somatic hypermutation. Overall, our study validates the idea that antibodies targeting the CW induce protection against virulent M. bovis infection. This study highlights the importance of antibodies targeting the CW in the defense against tuberculosis. IMPORTANCE M. bovis is the causative agent of animal tuberculosis (TB) and human TB. Research on M. bovis is of great public health significance. Currently, TB vaccines are mainly aimed at eliciting protection by enhancement of cell-mediated immunity, and there are few studies on protective antibodies. This is the first report of protective antibodies against M. bovis infection, and the antibodies had both preventive and even therapeutic effects in an M. bovis infection mouse model. Additionally, we reveal the relationship between CDR3 gene diversity and the immune characteristics of the antibodies. These results will provide valuable advice for the rational development of TB vaccines.

Characterizing the Spectrum of Latent Mycobacterium tuberculosis in the Cynomolgus Macaque Model: Clinical, Immunologic, and Imaging Features of Evolution

Mycobacterium tuberculosis infection outcomes have been described as active tuberculosis or latent infection but a spectrum of outcomes is now recognized. We used a nonhuman primate model, which recapitulates human infection, to characterize the clinical, microbiologic, and radiographic patterns associated with developing latent M. tuberculosis infection. Four patterns were identified. "Controllers" had normal erythrocyte sedimentation rate (ESR) without M. tuberculosis growth in bronchoalveolar lavage or gastric aspirate (BAL/GA). "Early subclinicals" showed transient ESR elevation and/or M. tuberculosis growth on BAL/GA for 60 days postinfection, "mid subclinicals" were positive for 90 days, and "late subclinicals" were positive intermittently, despite the absence of clinical disease. Variability was noted regarding granuloma formation, lung/lymph node metabolic activity, lung/lymph node bacterial burden, gross pathology, and extrapulmonary disease. Like human M. tuberculosis infection, this highlights the heterogeneity associated with the establishment of latent infection, underscoring the need to understand the clinical spectrum and risk factors associated with severe disease.

Spatial-temporal analysis of pulmonary tuberculosis among students in the Zhejiang Province of China from 2007-2020

Background

Pulmonary tuberculosis (PTB) is a serious chronic communicable disease that causes a significant disease burden in China; however, few studies have described its spatial epidemiological features in students.

Methods

Data of all notified PTB cases from 2007 to 2020 in the student population were collected in the Zhejiang Province, China using the available TB Management Information System. Analyses including time trend, spatial autocorrelation, and spatial-temporal analysis were performed to identify temporal trends, hotspots, and clustering, respectively.

Results

A total of 17,500 PTB cases were identified among students in the Zhejiang Province during the study period, accounting for 3.75% of all notified PTB cases. The health-seeking delay rate was 45.32%. There was a decreasing trend in PTB notifications throughout the period; clustering of cases was seen in the western area of Zhejiang Province. Additionally, one most likely cluster along with three secondary clusters were identified by spatial-temporal analysis.

Conclusion

Although was a downward trend in PTB notifications among students during the time period, an upward trend was seen in bacteriologically confirmed cases since 2017. The risk of PTB was higher among senior high school and above than of junior high school. The western area of Zhejiang Province was the highest PTB risk settings for students, and more comprehensive interventions should be strengthened such as admission screening and routine health monitoring to improve early identification of PTB.

Exploring the role of secretory proteins in the human infectious diseases diagnosis and therapeutics

Secretory proteins are playing important role during the host-pathogen interaction to develop the infection or protection into the cell. Pathogens developing infectious disease to human being are taken up by host macrophages or number of immune cells, play an important role in physiological, developmental and immunological function. At the same time, infectious agents are also secreting various proteins to neutralize the resistance caused by host cells and also helping the pathogens to develop the infection. Secretory proteins (secretome) are only developed at the time of host-pathogen interaction, therefore they become very important to develop the targeted and potential therapeutic strategies. Pathogen specific secretory proteins released during interaction with host cell provide opportunity to develop point of care and rapid diagnostic kits. Proteins secreted by pathogens at the time of interaction with host cell have also been found as immunogenic in nature and numbers of vaccines have been developed to control the spread of human infectious diseases. This chapter highlights the importance of secretory proteins in the development of diagnostic and therapeutic strategies to fight against human infectious diseases.

A novel multi-component protein vaccine ECP001 containing a protein polypeptide antigen nPstS1 riching in T-cell epitopes showed good immunogenicity and protection in mice

Tuberculosis (TB) is an infectious disease that seriously affects human health. Until now, the only anti-TB vaccine approved for use is the live attenuated Mycobacterium bovis (M. bovis) vaccine - BCG vaccine, but its protective efficacy is relatively low and does not provide satisfactory protection against TB in adults. Therefore, there is an urgent need for more effective vaccines to reduce the global TB epidemic. In this study, ESAT-6, CFP-10, two antigens full-length and the T-cell epitope polypeptide antigen of PstS1, named nPstS1, were selected to form one multi-component protein antigens, named ECP001, which include two types, one is a mixed protein antigen named ECP001m, the other is a fusion expression protein antigen named ECP001f, as candidates for protein subunit vaccines. were prepared by constructing one novel subunit vaccine by mixing or fusing the three proteins and combining them with aluminum hydroxide adjuvant, and the immunogenicity and protective properties of the vaccine was evaluated in mice. The results showed that ECP001 stimulated mice to produce high titre levels of IgG, IgG1 and IgG2a antibodies; meanwhile, high levels of IFN-γ and a broad range of specific cytokines were secreted by mouse splenocytes; in addition, ECP001 inhibited the proliferation of Mycobacterium tuberculosis in vitro with a capacity comparable to that of BCG. It can be concluded that ECP001 is a novel effective multicomponent subunit vaccine candidate with potential as BCG Initial Immunisation-ECP001 Booster Immunisation or therapeutic vaccine for M. tuberculosis infection.

Monoclonal antibodies to lipoarabinomannan/arabinomannan - characteristics and implications for tuberculosis research and diagnostics

Antibodies to the mycobacterial surface lipoglycan lipoarabinomannan (LAM) and its related capsular polysaccharide arabinomannan (AM) are increasingly important for investigations focused on both understanding mechanisms of protection against Mycobacterium tuberculosis (Mtb) and developing next-generation point-of-care tuberculosis (TB) diagnostics. We provide here an overview of the growing pipeline of monoclonal antibodies (mAbs) to LAM/AM. Old and new methodologies for their generation are reviewed and we outline and discuss their glycan epitope specificity and other features with implications for the TB field.

Bioinformatics analysis and consistency verification of a novel tuberculosis vaccine candidate HP13138PB

Background

With the increasing incidence of tuberculosis (TB) and the shortcomings of existing TB vaccines to prevent TB in adults, new TB vaccines need to be developed to address the complex TB epidemic.

Method

The dominant epitopes were screened from antigens to construct a novel epitope vaccine termed HP13138PB. The immune properties, structure, and function of HP13138PB were predicted and analyzed with bioinformatics and immunoinformatics. Then, the immune responses induced by the HP13138PB were confirmed by enzyme-linked immunospot assay (ELISPOT) and Th1/Th2/Th17 multi-cytokine detection kit.

Result

The HP13138PB vaccine consisted of 13 helper T lymphocytes (HTL) epitopes, 13 cytotoxic T lymphocytes (CTL) epitopes, and 8 B-cell epitopes. It was found that the antigenicity, immunogenicity, and solubility index of the HP13138PB vaccine were 0.87, 2.79, and 0.55, respectively. The secondary structure prediction indicated that the HP13138PB vaccine had 31% of α-helix, 11% of β-strand, and 56% of coil. The tertiary structure analysis suggested that the Z-score and the Favored region of the HP13138PB vaccine were -4.47 88.22%, respectively. Furthermore, the binding energies of the HP13138PB to toll-like receptor 2 (TLR2) was -1224.7 kcal/mol. The immunoinformatics and real-world experiments showed that the HP13138PB vaccine could induce an innate and adaptive immune response characterized by significantly higher levels of cytokines such as interferon-gamma (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-4 (IL-4), and IL-10.

Conclusion

The HP13138PB is a potential vaccine candidate to prevent TB, and this study preliminarily evaluated the ability of the HP13138PB to generate an immune response, providing a precursor target for developing TB vaccines.

Polymorphisms and gene expression of Notch4 in pulmonary tuberculosis

Background

Tuberculosis (TB) is a serious public health problem to human health, but the pathogenesis of TB remains elusive.

Methods

To identify novel candidate genes associated with TB susceptibility, we performed a population-based case control study to genotype 41SNPs spanning 21 genes in 435 pulmonary TB patients and 375 health donors from China.

Results

We found Notch4 gene rs206018 and rs422951 polymorphisms were associated with susceptibility to pulmonary tuberculosis. The association was validated in another independent cohort including 790 TB patients and 1,190 healthy controls. Moreover, we identified that the rs206018 C allele was associated with higher level of Notch4 in PBMCs from pulmonary TB patients. Furthermore, Notch4 expression increased in TB patients and higher Notch4 expression correlated with the severer pulmonary TB. Finally, we explored the origin and signaling pathways involved in the regulation of Notch4 expression in response to Mycobacterium tuberculosis (Mtb) infection. We determine that Mtb induced Notch4 and its ligand Jagged1expression in macrophages, and Notch4 through TLR2/P38 signaling pathway and Jagged1 through TLR2/ERK signaling pathway.

Conclusion

Our work further strengthens that Notch4 underlay an increased risk of TB in humans and is involved in the occurrence and development of TB, which could serve as a novel target for the host-targeted therapy of TB.

Nanomaterials in tuberculosis DNA vaccine delivery: historical perspective and current landscape

Vaccinations, especially DNA vaccines that promote host immunity, are the most effective interventions for tuberculosis (TB) control. However, the vaccine delivery system exhibits a significant impact on the protective effects of the vaccine. Recently, effective nanomaterial-based delivery systems (including nanoparticles, nanogold, nanoliposomes, virus-like particles, and virus carriers) have been developed for DNA vaccines to control TB. This review highlights the historical development of various nanomaterial-based delivery systems for TB DNA vaccines, along with the emerging technologies. Nanomaterial-based vaccine delivery systems could enhance the efficacy of TB vaccination; therefore, this summary could guide nanomaterial selection for optimal and safe vaccine delivery, facilitating the design and development of highly effective TB vaccines.

Construction and expression of Mycobacterium tuberculosis fusion protein AR2 and its immunogenicity in combination with various adjuvants to form vaccine

Tuberculosis (TB) is recognized as a highly infectious disease worldwide, and Bacille Calmette-Guerin (BCG) remains the only TB vaccine licensed for clinical use. As there is little evidence that BCG is effective in adults, there is an urgent need for a safe and effective vaccine to control TB in adults. In this study, we tested the immunomodulatory efficiency of the fusion protein AR2. whole blood IFN-γ release assay (WBIA) was used to detect antigen specificity. The immunogenicity of the vaccine was tested in C57BL/6 mice, and confirmed by enzyme-linked immunosorbent assay (ELISA), flow cytometry, and qRT-PCR. The fusion protein AR2 was successfully constructed and expressed. The level of IFN-γ in the peripheral blood of subjects stimulated by AR2 was significantly higher than in those induced by all subcomponent proteins. AR2-specific IgG and the Th1 cytokines IFN-γ, TNF-α, and iNOS were significantly increased in the group treated with the fusion protein and compound adjuvant (AR2+DMC). Likewise, the number of IFN-γ⁺ CD4⁺, IFN-γ⁺CD8⁺, and IL-4⁺ CD8⁺ T lymphocytes increased significantly. The combination of the fusion protein and the compound adjuvant (AR2+DMC) may be a suitable candidate for an enhanced TB vaccine. This study provides theoretical and experimental support for future research to enhance the effectiveness of TB vaccines and provides an experimental basis for evaluating the influence of different adjuvants on vaccine efficacy.

Subsequent AS01-adjuvanted vaccinations induce similar transcriptional responses in populations with different disease statuses

Transcriptional responses to adjuvanted vaccines can vary substantially among populations. Interindividual diversity in levels of pathogen exposure, and thus of cell-mediated immunological memory at baseline, may be an important determinant of population differences in vaccine responses. Adjuvant System AS01 is used in licensed or candidate vaccines for several diseases and populations, yet the impact of pre-existing immunity on its adjuvanticity remains to be elucidated. In this exploratory post-hoc analysis of clinical trial samples (clinicalTrials.gov: NCT01424501), we compared gene expression patterns elicited by two immunizations with the candidate tuberculosis (TB) vaccine M72/AS01, between three groups of individuals with different levels of memory responses to TB antigens before vaccination. Analyzed were one group of TB-disease-treated individuals, and two groups of TB-disease-naïve individuals who were (based on purified protein derivative [PPD] skin-test results) stratified into PPD-positive and PPD-negative groups. Although TB-disease-treated individuals displayed slightly stronger transcriptional responses after each vaccine dose, functional gene signatures were overall not distinctly different between groups. Considering the similarities with the signatures found previously for other AS01-adjuvanted vaccines, many features of the response appeared to be adjuvant-driven. Across groups, cell proliferation-related signals at 7 days post-dose 1 were associated with increased anti-M72 antibody response magnitudes. These early signals were stronger in the TB-disease-treated group as compared to both TB-disease-naïve groups. Interindividual homogeneity in gene expression levels was also higher for TB-disease-treated individuals post-dose 1, but increased in all groups post-dose 2 to attain similar levels between the three groups. Altogether, strong cell-mediated memory responses at baseline accelerated and amplified transcriptional responses to a single dose of this AS01-adjuvanted vaccine, resulting in more homogenous gene expression levels among the highly-primed individuals as compared to the disease-naïve individuals. However, after a second vaccination, response heterogeneity decreased and was similar across groups, irrespective of the degree of immune memory acquired at baseline. This information can support the design and analysis of future clinical trials evaluating AS01-adjuvanted vaccines.

BCGΔBCG1419c increased memory CD8+ T cell-associated immunogenicity and mitigated pulmonary inflammation compared with BCG in a model of chronic tuberculosis

Previously, we reported that a hygromycin resistant version of the BCGΔBCG1419c vaccine candidate reduced tuberculosis (TB) disease in BALB/c, C57BL/6, and B6D2F1 mice infected with Mycobacterium tuberculosis (Mtb) H37Rv. Here, the second-generation version of BCGΔBCG1419c (based on BCG Pasteur ATCC 35734, without antibiotic resistance markers, and a complete deletion of BCG1419c) was compared to its parental BCG for immunogenicity and protective efficacy against the Mtb clinical isolate M2 in C57BL/6 mice. Both BCG and BCGΔBCG1419c induced production of IFN-γ, TNF-α, and/or IL-2 by effector memory (CD44⁺CD62L^-), PPD-specific, CD4⁺ T cells, and only BCGΔBCG1419c increased effector memory, PPD-specific CD8⁺ T cell responses in the lungs and spleens compared with unvaccinated mice before challenge. BCGΔBCG1419c increased levels of central memory (CD62L⁺CD44⁺) T CD4⁺ and CD8⁺ cells compared to those of BCG-vaccinated mice. Both BCG strains elicited Th1-biased antigen-specific polyfunctional effector memory CD4⁺/CD8⁺ T cell responses at 10 weeks post-infection, and both vaccines controlled Mtb M2 growth in the lung and spleen. Only BCGΔBCG1419c significantly ameliorated pulmonary inflammation and decreased neutrophil infiltration into the lung compared to BCG-vaccinated and unvaccinated mice. Both BCG strains reduced pulmonary TNF-α, IFN-γ, and IL-10 levels. Taken together, BCGΔBCG1419c increased memory CD8+T cell-associated immunogenicity and mitigated pulmonary inflammation compared with BCG.

Toll-like receptor-mediated innate immune responses by recognition of the recombinant dormancy-associated Mycobacterium tuberculosis proteins Rv2659c and Rv1738

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) poses a major threat to the global public health. Importantly, latent tuberculosis infection (LTBI) still impedes the elimination of TB incidence since it has a substantial risk to develop active disease. A multi-stage subunit vaccine comprising active and latency antigens of Mtb has been raised as the promising vaccine to trigger immune protection against all stages of TB. Therefore, the discovery of new antigens that could trigger broad immune response is essential. While current development of TB vaccine mainly focuses on protective immunity mediated by adaptive immune response, the knowledge on triggering the innate immune response by antigens is still limited. We showed that recombinant dormancy-associated Mtb proteins Rv2659c and Rv1738 were recognized by human innate immune recognition molecules, Toll-like receptors (TLRs) 2 and 4 by using HEK-Blue™ hTLR2/hTLR4 systems. We further demonstrated that these two proteins activated phosphorylated NF-κB p65 (Ser536) in the human CD14+ blood cells. We also investigated that these two proteins significantly induced level of pro- and anti-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-10 and TNF-α) which were mediated through TLR2 and TLR4 pathways in human peripheral blood mononuclear cells (hPBMCs). These findings suggest that proteins Rv2659c and Rv1738 stimulated innate immune response targeting TLR2 and TLR4 to produce inflammatory cytokines, and their benefits would be valuable for the development of an effective prophylactic tuberculosis vaccine.

Que reste-t-il du BCG 100 ans après ?

Le BCG a fêté ses 100 ans en juillet 2021, en pleine pandémie de COVID-19, alors qu'une baisse des prises en charge de cas de tuberculose avait lieu suite à la diminution des activités de dépistage à travers le monde. Si le développement vaccinal permet d'envisager un vaccin plus efficace et mieux toléré que le BCG, on peut retenir que celui-ci réduit, lorsqu'il est administré dans l'enfance, le risque de tuberculose maladie mais aussi de mortalité toute cause, notamment dans les pays à faibles revenus. Son impact chez l'adulte reste moins évident. Cependant, l'effet protecteur observé vis-à-vis d'autres pathogènes (pressenti par Calmette lui-même) a conduit à évaluer l'efficacité de la revaccination par le BCG à l’âge adulte.

Immunomodulatory effect of mycobacterial outer membrane vesicles coated nanoparticles

Tuberculosis (TB) is one of the most widely prevalent infectious diseases that cause significant mortality. Bacillus Calmette-Guérin (BCG), the current TB vaccine used in clinics, shows variable efficacy and has safety concerns for immunocompromised patients. There is a need to develop new and more effective TB vaccines. Outer membrane vesicles (OMVs) are vesicles released by Mycobacteria that contain several lipids and membrane proteins and act as a good source of antigens to prime immune response. However, the use of OMVs as vaccines has been hampered by their heterogeneous size and low stability. Here we report that mycobacterial OMVs can be stabilized by coating over uniform-sized 50 nm gold nanoparticles. The OMV-coated gold nanoparticles (OMV-AuNP) show enhanced uptake and activation of macrophages and dendritic cells. Proteinase K and TLR inhibitor studies demonstrated that the enhanced activation was attributed to proteins present on OMVs and was mediated primarily by TLR2 and TLR4. Mass spectrometry analysis revealed several potential membrane proteins that were common in both free OMVs and OMV-AuNP. Such strategies may open up new avenues and the utilization of novel antigens for developing TB vaccines.

Bridging the Gap in End Tuberculosis Targets in the Elderly Population in Eastern China: Observational Study From 2015 to 2020

BACKGROUND

With a progressive increase in the aging process, the challenges posed by pulmonary tuberculosis (PTB) are also increasing for the elderly population.

OBJECTIVE

This study aimed to identify the epidemiological distribution of PTB among the elderly, forecast the achievement of the World Health Organization's 2025 goal in this specific group, and predict further advancement of PTB in the eastern area of China.

METHODS

All notified active PTB cases aged ≥65 years from Zhejiang Province were screened and analyzed. The general epidemiological characteristics were depicted and presented using the ArcGIS software. Further prediction of PTB was performed using R and SPSS software programs.

RESULTS

Altogether 41,431 cases aged ≥65 years were identified by the surveillance system from 2015 to 2020. After excluding extrapulmonary TB cases, we identified 39,832 PTB cases, including laboratory-confirmed (23,664, 59.41%) and clinically diagnosed (16,168, 40.59%) PTB. The notified PTB incidence indicated an evident downward trend with a reduction of 30%; however, the incidence of bacteriologically positive cases was steady at approximately 60/100,000. Based on the geographical distribution, Quzhou and Jinhua Cities had a higher PTB incidence among the elderly. The delay in PTB diagnosis was identified, and a significantly prolonged treatment course was observed in the elderly. Moreover, a 50% reduction of PTB incidence by the middle of 2024 was predicted using a linear regression model. It was found that using the exponential smoothing model would be better to predict the PTB trend in the elderly than a seasonal autoregressive integrated moving average model.

CONCLUSIONS

More comprehensive and effective interventions such as active PTB screening combined with physical checkup and succinct health education should be implemented and strengthened in the elderly. A more systematic assessment of the PTB epidemic trend in the elderly population should be considered to incorporate more predictive factors.

Pediatric Tuberculosis Management: A Global Challenge or Breakthrough?

Managing pediatric tuberculosis (TB) remains a public health problem requiring urgent and long-lasting solutions as TB is one of the top ten causes of ill health and death in children as well as adolescents universally. Minors are particularly susceptible to this severe illness that can be fatal post-infection or even serve as reservoirs for future disease outbreaks. However, pediatric TB is the least prioritized in most health programs and optimal infection/disease control has been quite neglected for this specialized patient category, as most scientific and clinical research efforts focus on developing novel management strategies for adults. Moreover, the ongoing coronavirus pandemic has meaningfully hindered the gains and progress achieved with TB prophylaxis, therapy, diagnosis, and global eradication goals for all affected persons of varying age bands. Thus, the opening of novel research activities and opportunities that can provide more insight and create new knowledge specifically geared towards managing TB disease in this specialized group will significantly improve their well-being and longevity.