Host immune responses to mycobacterial antigens and their implications for the development of a vaccine to control tuberculosis

Nanomaterial-mediated host directed therapy of tuberculosis by manipulating macrophage autophagy

Tuberculosis (TB), induced by Mycobacterium tuberculosis (Mtb) infection, remains a major public health issue worldwide. Mtb has developed complicated strategies to inhibit the immunological clearance of host cells, which significantly promote TB epidemic and weaken the anti-TB treatments. Host-directed therapy (HDT) is a novel approach in the field of anti-infection for overcoming antimicrobial resistance by enhancing the antimicrobial activities of phagocytes through phagosomal maturation, autophagy and antimicrobial peptides. Autophagy, a highly conserved cellular event within eukaryotic cells that is effective against a variety of bacterial infections, has been shown to play a protective role in host defense against Mtb. In recent decades, the introduction of nanomaterials into medical fields open up a new scene for novel therapeutics with enhanced efficiency and safety against different diseases. The active modification of nanomaterials not only allows their attractive targeting effects against the host cells, but also introduce the potential to regulate the host anti-TB immunological mechanisms, such as apoptosis, autophagy or macrophage polarization. In this review, we introduced the mechanisms of host cell autophagy for intracellular Mtb clearance, and how functional nanomaterials regulate autophagy for disease treatment. Moreover, we summarized the recent advances of nanomaterials for autophagy regulations as novel HDT strategies for anti-TB treatment, which may benefit the development of more effective anti-TB treatments.

Chemical and Biological Characterization of Mycobacterium Tuberculosis-Specific ESAT6-Like Proteins and their Potentials in the Prevention of Tuberculosis and Asthma

Early Secreted Antigenic Target 6 kDa (ESAT6) is a potent immunogenic protein secreted by the bacteria causing tuberculosis, i.e., Mycobacterium tuberculosis. Another highly immunogenic culture filtrate protein whose gene is linked to ESAT6/ESXA is known as CFP10/ESXB. Because of their high immunogenicity and specificity to M. tuberculosis, these proteins have been proposed as a vaccine to prevent tuberculosis and diagnose the active/latent disease. However, the same proteins cannot be used for prevention and diagnosis because immunized but healthy people will also show a positive response and be falsely reported as diseased. Therefore, in this review article, the search was made to identify if any other ESAT6-like proteins exist in the M. tuberculosis genome. The search identified 21 additional ESAT-like proteins, i.e., ESXC to ESXW. Immunological characterization has shown that some of them (especially ESXV) were able to induce immune responses in vitro with cells obtained from tuberculosis patients and healthy donors. When the protein ESXV was tested in different recombinant forms (expressed in Escherichia coli, mycobacterial vectors, and DNA plasmids) and injected in mice, immune responses were induced to multiple epitopes of the protein. Furthermore, immunization of mice with ESXV protected them from infection with M. tuberculosis. The same protein was also able to protect mice against the induction of asthma. These results suggest that ESXV has the potential to protect against two major diseases of the world, i.e., tuberculosis and asthma, and hence may be used as a common vaccine for both diseases.

A Dendritic Cell-Activating Rv1876 Protein Elicits Mycobacterium Bovis BCG-Prime Effect via Th1-Immune Response

The widely administered tuberculosis (TB) vaccine, Bacillus Calmette-Guerin (BCG), is the only licensed vaccine, but has highly variable efficiency against childhood and pulmonary TB. Therefore, the BCG prime-boost strategy is a rational solution for the development of new TB vaccines. Studies have shown that Mycobacterium tuberculosis (Mtb) culture filtrates contain proteins that have promising vaccine potential. In this study, Rv1876 bacterioferritin was identified from the culture filtrate fraction with strong immunoreactivity. Its immunobiological potential has not been reported previously. We found that recombinant Rv1876 protein induced dendritic cells' (DCs) maturation by MAPK and NF-κB signaling activation, induced a T helper type 1 cell-immune response, and expanded the population of the effector/memory T cell. Boosting BCG with Rv1876 protein enhanced the BCG-primed Th1 immune response and reduced the bacterial load in the lung compared to those of BCG alone. Thus, Rv1876 is a good target for the prime-boost strategy.

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

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

Fusion of Dendritic Cells Activating Rv2299c Protein Enhances the Protective Immunity of Ag85B-ESAT6 Vaccine Candidate against Tuberculosis

In Mycobacterium tuberculosis infection, naïve T cells that encounter mycobacterial antigens through dendritic cells (DCs) induce various CD4⁺ T-cell responses; therefore, appropriate DC activation is the key for protective immunity against tuberculosis. We previously found that Rv2299c-matured DCs induce Th1 differentiation with bactericidal activity. In this study, to prove that Rv2299c could enhance the protective immunity of other vaccine candidates comprising T-cell-stimulating antigens, Ag85B-ESAT6, a well-known vaccine candidate, was selected as a fusion partner of Rv2299c. Recombinant Rv2299c-Ag85B-ESAT6 protein induced DC maturation and activation. Furthermore, fusion of Rv2299c enhanced the protective efficacy of the Ag85B-ESAT6 vaccine in a mouse model and significantly higher production of TNF-α and IL-2 was detected in the lungs, spleen, and lymph nodes of the group immunized with the Rv2299c-fused protein than with Ag85B-ESAT6. In addition, fusion of Rv2299c enhanced the Ag85B-ESAT6-mediated expansion of multifunctional CD4⁺ T cells. These data suggested that the DC-activating protein Rv2299c may potentiate the protective immunity of the vaccine candidate comprising T cell antigens.

Recent progress in the design of DNA vaccines against tuberculosis

Current tuberculosis (TB) vaccines have some disadvantages and many efforts have been undertaken to produce effective TB vaccines. As a result of their advantages, DNA vaccines are promising future vaccine candidates. This review focuses on the design and delivery of novel DNA-based vaccines against TB.

The flavonoids of Sophora flavescens exerts anti-inflammatory activity via promoting autophagy of Bacillus Calmette-Guérin-stimulated macrophages

Tuberculosis (TB), a highly infectious air-borne disease, has remained a global health problem. Conventional treatment and preventions such as antibiotics and Bacilli Calmette-Guerin (BCG) vaccine can be unreliable. In view of the increasing prevalence of anti-TB drug resistance, adjunctive therapy may be necessary to shorten the recovery time. We have previously shown that flavonoids in the medicinal herb Sophora flavescens exhibit anti-inflammatory and bactericidal activities. The aim of this study was to investigate the molecular and cellular characteristics of flavonoids of S. flavescens (FSF) in BCG-stimulated macrophages for assessing their roles in anti-inflammation and autophagy. Mouse alveolar macrophage (MH-S) cell line and primary mouse peritoneal macrophages were stimulated in vitro with heat-inactivated BCG and treated with FSF, with or without autophagy inhibitor Bafilomycin A1 (BafA1). Gene expression was analyzed using quantitative PCR, and cytokine/chemokine release was analyzed by Milliplex assay and ELISA. Autophagy-related proteins were quantified by Western blot and flow cytometry, and autophagolysosomes were detected using fluorescence microscopy. In both MH-S cell line and mouse peritoneal macrophages stimulated by heat-inactivated BCG, FSF was found to up-regulate autophagy-related proteins microtubule-associated protein 1A/1B-light chain 3 (LC3) and protein 62 (p62), and suppress the induced proinflammatory cytokine TNF-α, CCL5, and IL-6. FSF actively modulates immune processes through suppressing BCG-mediated inflammation by promoting autophagy in MH-S cells and mouse peritoneal macrophages. We suggest that FSF may be useful as an adjunctive therapeutic agent for TB infection by modulating cell survival through autophagy and reducing inflammation.

PPE39 of the Mycobacterium tuberculosis strain Beijing/K induces Th1-cell polarization through dendritic cell maturation

In a previous study, we have identified MTBK_24820, the complete protein form of PPE39 in the hypervirulent Mycobacterium tuberculosis (Mtb) strain Beijing/K by using comparative genomic analysis. PPE39 exhibited vaccine potential against Mtb challenge in a murine model. Thus, in this present study, we characterize PPE39-induced immunological features by investigating the interaction of PPE39 with dendritic cells (DCs). PPE39-treated DCs display reduced dextran uptake and enhanced MHC-I, MHC-II, CD80 and CD86 expression, indicating that this PPE protein induces phenotypic DC maturation. In addition, PPE39-treated DCs produce TNF-α, IL-6 and IL-12p70 to a similar and/or greater extent than lipopolysaccharide-treated DCs in a dose-dependent manner. The activating effect of PPE39 on DCs was mediated by TLR4 through downstream MAPK and NF-κB signaling pathways. Moreover, PPE39-treated DCs promoted naïve CD4⁺ T-cell proliferation accompanied by remarkable increases of IFN-γ and IL-2 secretion levels, and an increase in the Th1-related transcription factor T-bet but not in Th2-associated expression of GATA-3, suggesting that PPE39 induces Th1-type T-cell responses through DC activation. Collectively, the results indicate that the complete form of PPE39 is a so-far-unknown TLR4 agonist that induces Th1-cell biased immune responses by interacting with DCs.This article has an associated First Person interview with the first author of the paper.

EXPRESSION OF IMMUNOGLOBULIN, GRANZYME-B AND PERFORIN AGAINST Ag85A AND Ag85B PROTEINS OF MYCOBACTERIUM TUBERCULOSIS IN BALB/C MICE

Background:

Ag85 is a protein that may maintain survival of M. tuberculosis in intracellular parts of host cells and is considered as a virulence factor. The expression of Ag85 protein can stimulate proliferation and differentiation of B- cells and T-cells in patients with tuberculosis. This research aimed to determine the ability of Ag85A and Ag85B proteins in activating the response of antibodies, granzyme-B and perforin in Balb/c mice.

Materials and Methods:

Twenty-five male Balb/c mice were assigned into five groups. Group I was treated with adjuvant, group II with Bacillus Calmette-Guerin (BCG) vaccine, group III with a combination of BCG and Ag85A, group IV with a combination of BCG and Ag85B and group V with a combination of BCG, Ag85A and Ag85B. Concentrations of immunoglobulin G, granzyme-B and perforin were examined using ELISA and the number of CD8+ T-cells and NK T-cells were checked by flow cytometry.

Results:

The highest concentration of immunoglobulin G was found in group V with 62.49±5.4327 ng/ml. The highest mean number of CD8+ T-cells, NK T-cells, granzyme-B and perforin was found in group IV with 4.32%, 1.03%, 35.11±1.7789 pg/ml and 6.19±0.2235 pg/ml, respectively. The results of One-Way ANOVA test showed that there were significant differences in immunoglobulin responses, with p<0.05. The expressions of granzyme-B and perforin were higher in mice treated with combination of BCG and recombinant proteins.

Conclusions:

Ag85 protein can be combined with the BCG vaccine to improve protection against M. tuberculosis infection.

Immunogenicity of late stage specific peptide antigens of Mycobacterium tuberculosis

Global burden of latent TB infection comprises one-third of the world population. Identifying potential Mycobacterium tuberculosis (Mtb) latency associated antigens that can generate protective immunity against the pathogen is crucial for designing an effective TB vaccine. Usually the immune system responds to a small number of amino acids as MHC Class I or Class II peptides. The precision to trigger epitope specific protective T-cell immune response could therefore be achieved with synthetic peptide-based subunit vaccine. In the present study we have considered an immunoinformatic approach using available softwares (ProPred, IEDB, NETMHC, BIMAS, Vaxijen2.0) and docking and visualizing softwares (CABSDOCK, HEX, Pymol, Discovery Studio) to select 10 peptides as latency antigens from 4 proteins (Rv2626, Rv2627, Rv2628, and Rv2032) of DosR regulon of Mtb. As Intracellular IFN-γ secreted by T cells is the most essential cytokine in Th1 mediated protective immunity, these peptides were verified as potential immunogenic epitopes in Peripheral Blood Mononuclear Cells (PBMCs) of 10 healthy contacts of TB patients (HTB) and 10 Category I Pulmonary TB patients (PTB).The antigen-specific CD4 and CD8 T cells expressing intracellular IFN-γ were analyzed using monoclonal antibodies in all subjects by multi-parameter flow cytometry. Both, PTB and HTB individuals responded to DosR peptides by showing increased frequency of IFN-γ⁺CD4 and IFN-γ⁺CD8 T cells. The T-cell responses were significantly higher in PTB patients in comparision to the HTB individuals. Additionally, our synthetic peptides and pools showed higher frequencies of IFN-γ⁺CD4 and IFN-γ⁺CD8 T cells than the peptides of Ag85B. This pilot study can be taken up further in larger sample size which may support the untapped opportunity of designing Mtb DosR inclusive peptide based post-exposure subunit vaccine.

Oxidization of TGFβ-activated kinase by MPT53 is required for immunity to Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb)-derived components are usually recognized by pattern recognition receptors to initiate a cascade of innate immune responses. One striking characteristic of Mtb is their utilization of different type VII secretion systems to secrete numerous proteins across their hydrophobic and highly impermeable cell walls, but whether and how these Mtb-secreted proteins are sensed by host immune system remains largely unknown. Here, we report that MPT53 (Rv2878c), a secreted disulfide-bond-forming-like protein of Mtb, directly interacts with TGF-β-activated kinase 1 (TAK1) and activates TAK1 in a TLR2- or MyD88-independent manner. MPT53 induces disulfide bond formation at C²¹⁰ on TAK1 to facilitate its interaction with TRAFs and TAB1, thus activating TAK1 to induce the expression of pro-inflammatory cytokines. Furthermore, MPT53 and its disulfide oxidoreductase activity is required for Mtb to induce the host inflammatory responses via TAK1. Our findings provide an alternative pathway for host signalling proteins to sense Mtb infection and may favour the improvement of current vaccination strategies.

Immunization of Vγ2Vδ2 T cells programs sustained effector memory responses that control tuberculosis in nonhuman primates

Despite the urgent need for a better tuberculosis (TB) vaccine, relevant protective mechanisms remain unknown. We previously defined protective phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP)–specific Vγ2Vδ2 T cells as a unique subset in primates, and, here, we immunized them selectively for protection against TB. A single respiratory vaccination of macaques with attenuated HMBPP-producing Listeria monocytogenes (Lm ΔactA prfA*), but not an HMBPP-lacking ΔgcpE Listeria strain, expanded Vγ2Vδ2 T cells, elicited Th1-like Vγ2Vδ2 T cell responses, and reduced TB infection/pathology after moderate-dose TB challenge. Such protection correlated with rapid memory-like, Th1-like Vγ2Vδ2 T cell responses, the presence of tissue-resident Vγ2Vδ2 T effectors coproducing IFN-γ/perforin and inhibiting intracellular Mycobacterium tuberculosis growth, and enhanced CD4⁺/CD8⁺ T cell responses. These findings establish a concept incorporating immunization of human Vγ2Vδ2 T cells for TB vaccine development.

Tuberculosis (TB) remains a leading killer among infectious diseases, and a better TB vaccine is urgently needed. The critical components and mechanisms of vaccine-induced protection against Mycobacterium tuberculosis (Mtb) remain incompletely defined. Our previous studies demonstrate that Vγ2Vδ2 T cells specific for (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) phosphoantigen are unique in primates as multifunctional effectors of immune protection against TB infection. Here, we selectively immunized Vγ2Vδ2 T cells and assessed the effect on infection in a rhesus TB model. A single respiratory vaccination of macaques with an HMBPP-producing attenuated Listeria monocytogenes (Lm ΔactA prfA*) caused prolonged expansion of HMBPP-specific Vγ2Vδ2 T cells in circulating and pulmonary compartments. This did not occur in animals similarly immunized with an Lm ΔgcpE strain, which did not produce HMBPP. Lm ΔactA prfA* vaccination elicited increases in Th1-like Vγ2Vδ2 T cells in the airway, and induced containment of TB infection after pulmonary challenge. The selective immunization of Vγ2Vδ2 T cells reduced lung pathology and mycobacterial dissemination to extrapulmonary organs. Vaccine effects coincided with the fast-acting memory-like response of Th1-like Vγ2Vδ2 T cells and tissue-resident Vγ2Vδ2 effector T cells that produced both IFN-γ and perforin and inhibited intracellular Mtb growth. Furthermore, selective immunization of Vγ2Vδ2 T cells enabled CD4⁺ and CD8⁺ T cells to mount earlier pulmonary Th1 responses to TB challenge. Our findings show that selective immunization of Vγ2Vδ2 T cells can elicit fast-acting and durable memory-like responses that amplify responses of other T cell subsets, and provide an approach to creating more effective TB vaccines.

Immunological characteristics of Mycobacterium tuberculosis subunit vaccines immunized through different routes

Tuberculosis is chronic infectious disease caused by Mycobacterium tuberculosis (M.tb) that is prevalent worldwide. Several specific antigens, such as Antigen 85B (Ag85B) and 6 kDa early secretory antigenic target (ESAT-6) protein of M.tb, are listed as some of the candidate subunit vaccines against M.tb. ESAT-6, as a virulent factor and differential gene in M.tb, shows insufficient immunogenicity in animal model. In order to investigate the ways to improve the immunogenicity of ESAT-6, we immunized ESAT-6 by subcutaneous and intramuscular routes with different adjuvants. We found that ESAT-6 immunized alone did not induce significant humoral immunity in both immunization routes. However, subcutaneous immunization of ESAT-6 plus incomplete Freund's adjuvant can induce a significant humoral immune response, enhanced proliferation and elevated secretion of IFN-γ from splenocytes. Intramuscular immunization of ESAT-6 plus adjuvant aluminum salt or poly(I:C) did not enhance humoral and cellular immune responses. Therefore, it is concluded that immunization of ESAT-6 subcutaneously plus incomplete Freund's adjuvant induces stronger humoral and cellular immune responses, which can be considered of ESAT-6 as a subunit vaccine in further research against tuberculosis.

Mycobacterium tuberculosis PPE60 antigen drives Th1/Th17 responses via Toll-like receptor 2-dependent maturation of dendritic cells

Targeting of Mycobacterium tuberculosis (MTB) PE/PPE antigens that induce type 1 helper T cell (Th1) and Th17 responses represents a crucial strategy for the development of tuberculosis (TB) vaccines. However, only a few PE/PPE antigens induce these responses. Here, we sought to determine how the cell wall-associated antigen PPE60 (Rv3478) activates dendritic cell (DC) maturation and T-cell differentiation. We observed that PPE60 induces DC maturation by augmenting the protein expression of cluster of differentiation 80 (CD80) and CD86 and major histocompatibility complex (MHC) class I and MHC class II on the cell surface. PPE60 also stimulated the production of tumor necrosis factor-α (TNFα), interleukin (IL)-1β, IL-6, IL-12p70, and IL-23p19 but not IL-10. This induction was mediated by Toll-like receptor 2 (TLR2) and followed by activation of p38, c-Jun N-terminal kinase (JNK), and NF-κB signaling. PPE60 enhanced MHC-II expression and promoted antigen processing by DCs in a TLR2-dependent manner. Moreover, PPE60-stimulated DCs directed naïve CD4⁺ T cells to produce IFN-γ, IL-2, and IL-17A, expanding the Th1 and Th17 responses, along with activation of T-bet and RAR-related orphan receptor C (RORγt) but not GATA-3. Moreover, PPE60 activated the NLRP3 inflammasome followed by caspase-1-dependent IL-1β and IL-18 synthesis in DCs. Of note, pharmacological inhibition of NLRP3 activation specifically attenuated IFN-γ and IL-17A secretion into the supernatant from CD4⁺ T cells cocultured with PPE60-activated DCs. These findings indicate that PPE60 induces Th1 and Th17 immune responses by activating DCs in a TLR2-dependent manner, suggesting PPE60's potential for use in MTB vaccine development.

Next generation sequencing reveals changes of the γδ T cell receptor repertoires in patients with pulmonary tuberculosis

Tuberculosis (TB) is a severe global threat to human health. The immune protection initiated by γδ T cells play an important role in mycobacterial infection. Vaccines for Mycobacterium tuberculosis (Mtb) based on γδ T cells provide a novel approach for TB control. In our previous studies, we found a preponderant complementarity-determining region 3 (CDR3) sequence of the γδ T cell receptor (TCR) in TB patients, and successfully identified a tuberculosis antigen that can effectively activate γδ T cells with a reverse genetic strategy. However, due to the throughput limitation of the method we used, the information we obtained about the γδ TCR repertoire and preponderant CDR3 sequences was limited. In this study, we introduced next generation sequencing (NGS) to study the γδ TCR CDR3 repertoires in TB patients. We found that the CDR3δ tended to be more polyclonal and CDR3γ tended to be longer in TB patients; the γδ T cells expressing CDR3 sequences using a Vγ9-JγP rearrangement expanded significantly during Mtb infection. We also identified new preponderant CDR3 sequences during Mtb infection. This study comprehensively characterized the γδ T cell receptor repertoire changes, and provides useful information for the development of new vaccines and adjuvants against TB.

Mycobacterium tuberculosis Rv3628 drives Th1-type T cell immunity via TLR2-mediated activation of dendritic cells and displays vaccine potential against the hyper-virulent Beijing K strain

Identification of vaccine target antigens (Ags) that induce Ag-specific Th1 immunity is the first step toward the development of a tuberculosis vaccine. Here, we evaluated the Mycobacterium tuberculosis (Mtb) protein Rv3628, a soluble inorganic pyrophosphatase, as a vaccine target and characterized the molecular details of its interaction with dendritic cells (DCs). Rv3628 activated DCs, increasing their expression of cell surface molecules and augmenting their production of TNF-α, IL-1β, IL-6, and IL-12p70. Rv3628 mediated these effects by binding to TLR2 and activating downstream MyD88-, MAPK- and NF-κB-dependent signaling pathways. Rv3628-stimulated DCs induced the expansion of OVA-specific CD4⁺ and CD8⁺ T cells, which secreted IFN-γ and IL-2. Rv3628-specific effector/memory T cells expanded to a similar extent as those stimulated with ESAT-6 Ag in samples of lung and spleen cells collected from Mtb-infected mice. Finally, an Rv3628 subunit vaccine adjuvanted with dimethyldioctadecylammonium liposomes containing monophosphoryl lipid-A caused significant reductions in bacterial counts and lung inflammation after challenge with the hyper-virulent Mtb K strain. Importantly, protective efficacy was correlated with the generation of Rv3628-specific CD4⁺ T cells co-producing IFN-γ, TNF-α and IL-2 and exhibiting an elevated IFN-γ recall response. Thus, Rv3628 polarizes DCs toward a Th1 phenotype and promotes protective immunity against Mtb infection.

Rv2299c, a novel dendritic cell-activating antigen of Mycobacterium tuberculosis, fused-ESAT-6 subunit vaccine confers improved and durable protection against the hypervirulent strain HN878 in mice

Understanding functional interactions between DCs and antigens is necessary for achieving an optimal and desired immune response during vaccine development. Here, we identified and characterized protein Rv2299c (heat-shock protein 90 family), which effectively induced DC maturation. The Rv2299c-maturated DCs showed increased expression of surface molecules and production of proinflammatory cytokines. Rv2299c induced these effects by binding to TLR4 and stimulating the downstream MyD88-, MAPK- and NF-κB-dependent signaling pathways. The Rv2299c-maturated DCs also showed an induced Th1 cell response with bactericidal activity and expansion of effector/memory T cells. The Rv2299c-ESAT-6 fused protein had greater immunoreactivity than ESAT-6. Furthermore, boosting BCG with the fused protein significantly reduced hypervirulent Mycobacterium tuberculosis HN878 burdens post-challenge. The pathological study of the lung from the challenged mice assured the efficacy of the fused protein. The fused protein boosting also induced Rv2299c-ESAT-6-specific multifunctional CD4⁺ T-cell response in the lungs of the challenged mice. Our findings suggest that Rv2299c is an excellent candidate for the rational design of an effective multiantigenic TB vaccine.

Antigen 85 complex as a powerful Mycobacterium tuberculosis immunogene: Biology, immune-pathogenicity, applications in diagnosis, and vaccine design

Mycobacterium tuberculosis (Mtb) is one of the most life-threatening mycobacterial species which is increasing the death rate due to emerging multi-drug resistant (MDR) strains. Concerned health authorities worldwide are interested in developing an effective vaccine to prevent the spread of Mtb. After years of research, including successful identification of many Mtb immunogenic molecules, effective therapeutic agents or a vaccine have yet to be found. However, among the identified Mtb immunogenes, antigen 85 (Ag85) complex (Ag85A, Ag85B, and Ag85C) is receiving attention from scientists as it allows bacteria to evade the host immune response by preventing formation of phagolysosomes for eradication of infection. Due to their importance, A85 molecules are being utilized as tools in diagnostic methods and in the construction of new vaccines, such as recombinant attenuated vaccines, DNA vaccines, and subunit vaccines. This paper represents a comprehensive review of studies on Mtb molecules examining pathogenicity, biochemistry, immunology, and the role of Mtb in therapeutic or vaccine research.

Striking the right immunological balance prevents progression of tuberculosis

INTRODUCTION

Tuberculosis (TB) caused by infection with Mycobacterium tuberculosis (Mtb) is a major burden for human health worldwide. Current standard treatments for TB require prolonged administration of antimycobacterial drugs leading to exaggerated inflammation and tissue damage. This can result in the reactivation of latent TB culminating in TB progression. Thus, there is an unmet need to develop therapies that would shorten the duration of anti-TB treatment and to induce optimal protective immune responses to control the spread of mycobacterial infection with minimal lung pathology.

FINDINGS

Granulomata is the hallmark structure formed by the organized accumulation of immune cells including macrophages, natural killer cells, dendritic cells, neutrophils, T cells, and B cells to the site of Mtb infection. It safeguards the host by containing Mtb in latent form. However, granulomata can undergo caseation and contribute to the reactivation of latent TB, if the immune responses developed to fight mycobacterial infection are not properly controlled. Thus, an optimal balance between innate and adaptive immune cells might play a vital role in containing mycobacteria in latent form for prolonged periods and prevent the spread of Mtb infection from one individual to another.

CONCLUSION

Optimal and well-regulated immune responses against Mycobacterium tuberculosis may help to prevent the reactivation of latent TB. Moreover, therapies targeting balanced immune responses could help to improve treatment outcomes among latently infected TB patients and thereby limit the dissemination of mycobacterial infection.

Adoptive Transfer of Phosphoantigen-Specific γδ T Cell Subset Attenuates Mycobacterium tuberculosis Infection in Nonhuman Primates

The dominant Vγ2Vδ2 T cell subset recognizes phosphoantigen and exists only in humans and nonhuman primates. Despite the discovery of γδ T cells >30 y ago, a proof-of-concept study has not been done to prove the principle that the Vγ2Vδ2 T cell subset is protective against Mycobacterium tuberculosis and other infections. In this study, we used an adoptive cell-transfer strategy to define the protective role of Vγ2Vδ2 T cells in a primate tuberculosis (TB) model. Vγ2Vδ2 T cells for adoptive transfer displayed central/effector memory and mounted effector functions, including the production of anti-M. tuberculosis cytokines and inhibition of intracellular mycobacteria. They also expressed CXCR3/CCR5/LFA-1 trafficking/tissue-resident phenotypes and consistently trafficked to the airway, where they remained detectable from 6 h through 7 d after adoptive transfer. Interestingly, the test group of macaques receiving transfer of Vγ2Vδ2 T cells at weeks 1 and 3 after high-dose (500 CFU) M. tuberculosis infection exhibited significantly lower levels of M. tuberculosis infection burdens in lung lobes and extrapulmonary organs than did the control groups receiving PBLs or saline. Consistently, adoptive transfer of Vγ2Vδ2 T cells attenuated TB pathology and contained lesions primarily in the infection site of the right caudal lung lobe, with no or reduced TB dissemination to other lobes, spleen, or liver/kidney; in contrast, the controls showed widespread TB dissemination. The proof-of-concept finding supports the view that the dominant Vγ2Vδ2 T cell subset may be included in the rational design of a TB vaccine or host-directed therapy.

Novel vaccine potential of Rv3131, a DosR regulon-encoded putative nitroreductase, against hyper-virulent Mycobacterium tuberculosis strain K

Accumulating evidence indicates that latency-associated Mycobacterium tuberculosis (Mtb)-specific antigens from the dormancy survival regulator regulon (DosR) may be promising novel vaccine target antigens for the development of an improved tuberculosis vaccine. After transcriptional profiling of DosR-related genes in the hyper-virulent Beijing Mtb strain K and the reference Mtb strain H37Rv, we selected Rv3131, a hypothetical nitroreductase, as a vaccine antigen and evaluated its vaccine efficacy against Mtb K. Mtb K exhibited stable and constitutive up-regulation of rv3131 relative to Mtb H37Rv under three different growth conditions (at least 2-fold induction) including exponential growth in normal culture conditions, hypoxia, and inside macrophages. Mice immunised with Rv3131 formulated in GLA-SE, a well-defined TLR4 adjuvant, displayed enhanced Rv3131-specific IFN-γ and serum IgG2c responses along with effector/memory T cell expansion and remarkable generation of Rv3131-specific multifunctional CD4⁺ T cells co-producing TNF-α, IFN-γ and IL-2 in both spleen and lung. Following challenge with Mtb K, the Rv3131/GLA-SE-immunised group exhibited a significant reduction in bacterial number and less extensive lung inflammation accompanied by the obvious persistence of Rv3131-specific multifunctional CD4⁺ T cells. These results suggest that Rv3131 could be an excellent candidate for potential use in a multi-antigenic Mtb subunit vaccine, especially against Mtb Beijing strains.

Mycobacterium tuberculosis proteins involved in cell wall lipid biosynthesis improve BCG vaccine efficacy in a murine TB model

OBJECTIVES

Advances in tuberculosis (TB) vaccine development are urgently required to enhance global disease management. We evaluated the potential of Mycobacterium tuberculosis (M. tb)-derived protein antigens Rv0447c, Rv2957 and Rv2958c to boost BCG vaccine efficacy in the presence or absence of glucopyranosyl lipid adjuvant formulated in a stable emulsion (GLA-SE) adjuvant.

METHODS

Mice received the BCG vaccine, followed by Rv0447c, Rv2957 and Rv2958c protein boosting with or without GLA-SE adjuvant 3 and 6 weeks later. Immune responses were examined at given time points. 9 weeks post vaccination, mice were aerosol-challenged with M. tb, and sacrificed at 6 and 12 weeks to assess bacterial burden.

RESULTS

Vaccination of mice with BCG and M. tb proteins in the presence of GLA-SE adjuvant triggered strong IFN-γ and IL-2 production by splenocytes; more TNF-α was produced without GLA-SE addition. Antibody responses to all three antigens did not differ, with or without GLA-SE adjuvant. Protein boosting without GLA-SE adjuvant resulted in vaccinated animals having better control of pulmonary M. tb load at 6 and 12 weeks post aerosol infection, while animals receiving the protein boost with GLA-SE adjuvant exhibited more bacteria in the lungs.

CONCLUSIONS

Our data provides evidence for developing Rv2958c, Rv2957 and Rv0447c in a heterologous prime-boost vaccination strategy with BCG.

Adjunct Strategies for Tuberculosis Vaccines: Modulating Key Immune Cell Regulatory Mechanisms to Potentiate Vaccination

Tuberculosis (TB) remains a global health threat of alarming proportions, resulting in 1.5 million deaths worldwide. The only available licensed vaccine, Bacillus Calmette–Guérin, does not confer lifelong protection against active TB. To date, development of an effective vaccine against TB has proven to be elusive, and devising newer approaches for improved vaccination outcomes is an essential goal. Insights gained over the last several years have revealed multiple mechanisms of immune manipulation by Mycobacterium tuberculosis (Mtb) in infected macrophages and dendritic cells that support disease progression and block development of protective immunity. This review provides an assessment of the known immunoregulatory mechanisms altered by Mtb, and how new interventions may reverse these effects. Examples include blocking of inhibitory immune cell coreceptor checkpoints (e.g., programed death-1). Conversely, immune mechanisms that strengthen immune cell effector functions may be enhanced by interventions, including stimulatory immune cell coreceptors (e.g., OX40). Modification of the activity of key cell “immunometabolism” signaling pathway molecules, including mechanistic target of rapamycin, glycogen synthase kinase-3β, wnt/β-catenin, adenosine monophosophate-activated protein kinase, and sirtuins, related epigenetic changes, and preventing induction of immune regulatory cells (e.g., regulatory T cells, myeloid-derived suppressor cells) are powerful new approaches to improve vaccine responses. Interventions to favorably modulate these components have been studied primarily in oncology to induce efficient antitumor immune responses, often by potentiation of cancer vaccines. These agents include antibodies and a rapidly increasing number of small molecule drug classes that have contributed to the dramatic immune-based advances in treatment of cancer and other diseases. Because immune responses to malignancies and to Mtb share many similar mechanisms, studies to improve TB vaccine responses using interventions based on “immuno-oncology” are needed to guide possible repurposing. Understanding the regulation of immune cell functions appropriated by Mtb to promote the imbalance between protective and pathogenic immune responses may guide the development of innovative drug-based adjunct approaches to substantially enhance the clinical efficacy of TB vaccines.

Heterologous boosting with recombinant VSV-846 in BCG-primed mice confers improved protection against Mycobacterium infection

Tuberculosis (TB) remains a major health problem worldwide, and the development of effective vaccines is urgently needed. Vaccination strategies based on heterologous prime-boost protocols using Mycobacterium bovis bacillus Calmette-Guérin (BCG) as primer and modified vaccinia virus Ankara strain expressing the mycobacterial antigen Ag85A (MVA85A) as booster may increase the protective efficacy of BCG. In addition, vaccination with the recombinant viral vaccine vesicular stomatitis virus (VSV)-846 (Rv3615c, Mtb10.4, and Rv2660c) can elicit a remarkable T-cell-mediated immune response and provide an effective long-term protection after the BCG challenge. In this study, we used VSV-846 to boost BCG and evaluated its immunogenicity in BALB/c mice. In this prime-boost approach, boosting with VSV-846 significantly enhanced IFN-γ CD4 T cell responses, which are crucial for anti-TB immune responses. Moreover, VSV-846 boosting significantly reduced pathology compared with mock vaccination, and decreased the bacterial loads in lung tissues compared with BCG or VSV-846 vaccination alone. The analysis of vaccine-induced immunity identified that polyfunctional T cells might contribute to the enhanced protection by VSV-846 boosting. This study proved that viral booster VSV-846 in mice improved the protection against mycobacteria infection, which could be helpful in designing an efficient vaccination strategy against TB in humans.

Boosting BCG-primed mice with chimeric DNA vaccine HG856A induces potent multifunctional T cell responses and enhanced protection against Mycobacterium tuberculosis

The tuberculosis pandemic continues to rampage despite widespread use of the current Bacillus Calmette-Guerin (BCG) vaccine. Because DNA vaccines can elicit effective antigen-specific immune responses, including potent T cell-mediated immunity, they are promising vehicles for antigen delivery. In a prime-boost approach, they can supplement the inadequate anti-TB immunological memory induced by BCG. Based on this, a chimeric DNA vaccine HG856A encoding Mycobacterium tuberculosis (M. tuberculosis) immunodominant antigen Ag85A plus two copies of ESAT-6 was constructed. Potent humoral immune responses, as well as therapeutic effects induced by this DNA vaccine, were observed previously in M. tuberculosis-infected mice. In this study, we further evaluated the antigen-specific T cell immune responses and showed that repeated immunization with HG856A gave modest protection against M. tuberculosis challenge infection and significantly boosted the immune protection primed by BCG vaccination. Enhanced protection was accompanied by increased multifunctional Th1 CD4(+) T cell responses, most notably by an elevated frequency of M. tuberculosis antigen-specific IL-2-producing CD4(+) T cells post-vaccination. These data confirm the potential of chimeric DNA vaccine HG856A as an anti-TB vaccine candidate.

Ag85A DNA Vaccine Delivery by Nanoparticles: Influence of the Formulation Characteristics on Immune Responses

The influence of DNA vaccine formulations on immune responses in combination with adjuvants was investigated with the aim to increase cell-mediated immunity against plasmid DNA (pDNA) encoding Mycobacterium tuberculosis antigen 85A. Different ratios of pDNA with cationic trimethyl chitosan (TMC) nanoparticles were characterized for their morphology and physicochemical characteristics (size, zeta potential, loading efficiency and pDNA release profile) applied in vitro for cellular uptake studies and in vivo, to determine the dose-dependent effects of pDNA on immune responses. A selected pDNA/TMC nanoparticle formulation was optimized by the incorporation of muramyl dipeptide (MDP) as an immunostimulatory agent. Cellular uptake investigations in vitro showed saturation to a maximum level upon the increase in the pDNA/TMC nanoparticle ratio, correlating with increasing Th1-related antibody responses up to a definite pDNA dose applied. Moreover, TMC nanoparticles induced clear polarization towards a Th1 response, indicated by IgG2c/IgG1 ratios above unity and enhanced numbers of antigen-specific IFN-γ producing T-cells in the spleen. Remarkably, the incorporation of MDP in TMC nanoparticles provoked a significant additional increase in T-cell-mediated responses induced by pDNA. In conclusion, pDNA-loaded TMC nanoparticles are capable of provoking strong Th1-type cellular and humoral immune responses, with the potential to be further optimized by the incorporation of MDP.

The Ag85B protein of the BCG vaccine facilitates macrophage uptake but is dispensable for protection against aerosol Mycobacterium tuberculosis infection

Defining the function and protective capacity of mycobacterial antigens is crucial for progression of tuberculosis (TB) vaccine candidates to clinical trials. The Ag85B protein is expressed by all pathogenic mycobacteria and is a component of multiple TB vaccines under evaluation in humans. In this report we examined the role of the BCG Ag85B protein in host cell interaction and vaccine-induced protection against virulent Mycobacterium tuberculosis infection. Ag85B was required for macrophage infection in vitro, as BCG deficient in Ag85B expression (BCG:(Δ85B)) was less able to infect RAW 264.7 macrophages compared to parental BCG, while an Ag85B-overexpressing BCG strain (BCG:(oex85B)) demonstrated improved uptake. A similar pattern was observed in vivo after intradermal delivery to mice, with significantly less BCG:(Δ85B) present in CD64(hi)CD11b(hi) macrophages compared to BCG or BCG:(oex85B). After vaccination of mice with BCG:(Δ85B) or parental BCG and subsequent aerosol M. tuberculosis challenge, similar numbers of activated CD4(+) and CD8(+) T cells were detected in the lungs of infected mice for both groups, suggesting the reduced macrophage uptake observed by BCG:(Δ85B) did not alter host immunity. Further, vaccination with both BCG:(Δ85B) and parental BCG resulted in a comparable reduction in pulmonary M. tuberculosis load. These data reveal an unappreciated role for Ag85B in the interaction of mycobacteria with host cells and indicates that single protective antigens are dispensable for protective immunity induced by BCG.

Mycobacterium tuberculosis PE27 activates dendritic cells and contributes to Th1-polarized memory immune responses during in vivo infection

A gradual understanding of the proline-glutamate (PE) and proline-proline-glutamate (PPE) families, which compromise 10% of the coding regions in the Mycobacterium tuberculosis (Mtb) genome, has uncovered unique roles in host-pathogen interactions. However, the immunological function of PE27 (Rv2769c), the largest PE member, remains unclear. Here, we explored the functional roles and related signaling mechanisms of PE27 in the interaction with dendritic cells (DCs) to shape the T cell response. PE27 phenotypically and functionally induces DC maturation by up-regulating CD80, CD86, MHC class I and MHC class II expression on the DC surface to promote the production of TNF-α, IL-1β, IL-6, and IL-12p70 but not IL-10. Additionally, we found that PE27-mediated DC activation requires the participation of mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) signaling pathways. Interestingly, PE27-treated DCs directed naïve CD4(+) T cells to secrete IFN-γ and activate T-bet but not GATA-3. PE27 also induced IFN-γ-producing memory T cell responses in Mtb-infected mice, indicating that PE27 contributes to Th1-polarization. Taken together, these findings suggest that PE27 possesses Th1-polarizing potential through DC maturation and could be useful in the design of TB vaccines.

Immunoevasion and immunosuppression of the macrophage by Mycobacterium tuberculosis

By virtue of their position at the crossroads between the innate and adaptive immune response, macrophages play an essential role in the control of bacterial infections. Paradoxically, macrophages serve as the natural habitat to Mycobacterium tuberculosis (Mtb). Mtb subverts the macrophage's mechanisms of intracellular killing and antigen presentation, leading ultimately to the development of tuberculosis (TB) disease. Here, we describe mechanisms of Mtb uptake by the macrophage and address key macrophage functions that are targeted by Mtb-specific effector molecules enabling this pathogen to circumvent host immune response. The macrophage functions described in this review include fusion between phagosomes and lysosomes, production of reactive oxygen and nitrogen species, antigen presentation and major histocompatibility complex class II expression and trafficking, as well as autophagy and apoptosis. All these are Mtb-targeted key cellular pathways, normally working in concert in the macrophage to recognize, respond, and activate 'proper' immune responses. We further analyze and discuss major molecular interactions between Mtb virulence factors and key macrophage proteins and provide implications for vaccine and drug development.

Expression and Purification of the Recombinant Cytochrome P450 CYP141 Protein of Mycobacterium Tuberculosis as a Diagnostic Tool and Vaccine Production

Background:

Tuberculosis (TB) is regarded as a health problem worldwide, particularly in developing countries. Mycobacterium tuberculosis (M. tuberculosis) is the cause of this disease. Approximately two billion people worldwide are infected by M. tuberculosis and annually about two million individuals die in consequence. Forty million people are estimated to die because of M. tuberculosis over the next 25 years if the measures for controlling this infection are not extensively developed. In the vaccination field, BacillusCalmette–Guérin (BCG) is still the most effective vaccine but it shows no efficacy in adult pulmonary patients. One of the other problems regarding TB is its appropriate diagnosis.

Objectives:

In this experimental study, the recombinant cytochrome P450 CYP141 protein of M. tuberculosis was expressed and purified to be used as a vaccine candidate and diagnostic purpose in subsequent investigations.

Materials and Methods:

The optimization of the cytochrome P450 CYP141 protein expression was evaluated in different conditions. Then, this protein was purified with a resin column of nickel–nitrilotriacetic acid and investigated via Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Western Blotting.

Results:

The highest expression of the cytochrome P450 CYP141 protein was obtained by the addition of 1 mM of isopropyl β-D-1-thiogalactopyranoside (IPTG) to the bacterial culture grown to an optical density at 600 nm (OD600) of 0.6, 16 hours after induction. This protein was subsequently purified with a purification of higher than 80%. The results of Western Blotting indicated that the purified protein was specifically detected.

Conclusions:

In this experimental study, for the first time in Iran the expression and purification of this recombinant protein was done successfully. This recombinant protein could be used as a vaccine candidate and diagnostic purpose in subsequent investigations.

The TB-specific CD4(+) T cell immune repertoire in both cynomolgus and rhesus macaques largely overlap with humans

Non-human primate (NHP) models of tuberculosis (TB) immunity and pathogenesis, especially rhesus and cynomolgus macaques, are particularly attractive because of the high similarity of the human and macaque immune systems. However, little is known about the MHC class II epitopes recognized in macaques, thus hindering the establishment of immune correlates of immunopathology and protective vaccination. We characterized immune responses in rhesus macaques vaccinated against and/or infected with Mycobacterium tuberculosis (Mtb), to a panel of antigens currently in human vaccine trials. We defined 54 new immunodominant CD4(+) T cell epitopes, and noted that antigens immunodominant in humans are also immunodominant in rhesus macaques, including Rv3875 (ESAT-6) and Rv3874 (CFP10). Pedigree and inferred restriction analysis demonstrated that this phenomenon was not due to common ancestry or inbreeding, but rather presentation by common alleles, as well as, promiscuous binding. Experiments using a second cohort of rhesus macaques demonstrated that a pool of epitopes defined in the previous experiments can be used to detect T cell responses in over 75% of individual monkeys. Additionally, 100% of cynomolgus macaques, irrespective of their latent or active TB status, responded to rhesus and human defined epitope pools. Thus, these findings reveal an unexpected general repertoire overlap between MHC class II epitopes recognized in both species of macaques and in humans, showing that epitope pools defined in humans can also be used to characterize macaque responses, despite differences in species and antigen exposure. The results have general implications for the evaluation of new vaccines and diagnostics in NHPs, and immediate applicability in the setting of macaque models of TB.

The microbiome at the pulmonary alveolar niche and its role in Mycobacterium tuberculosis infection

Advances in next generation sequencing (NGS) technology have provided the tools to comprehensively and accurately characterize the microbial community in the respiratory tract in health and disease. The presence of commensal and pathogenic bacteria has been found to have important effects on the lung immune system. Until relatively recently, the lung has received less attention compared to other body sites in terms of microbiome characterization, and its study carries special technological difficulties related to obtaining reliable samples as compared to other body niches. Additionally, the complexity of the alveolar immune system, and its interactions with the lung microbiome, are only just beginning to be understood. Amidst this complexity sits Mycobacterium tuberculosis (Mtb), one of humanity's oldest nemeses and a significant public health concern, with millions of individuals infected with Mtb worldwide. The intricate interactions between Mtb, the lung microbiome, and the alveolar immune system are beginning to be understood, and it is increasingly apparent that improved treatment of Mtb will only come through deep understanding of the interplay between these three forces. In this review, we summarize our current understanding of the lung microbiome, alveolar immunity, and the interaction of each with Mtb.

Mycobacterium tuberculosis TlyA Protein Negatively Regulates T Helper (Th) 1 and Th17 Differentiation and Promotes Tuberculosis Pathogenesis

Mycobacterium tuberculosis, the causative agent of tuberculosis, is an ancient pathogen and a major cause of death worldwide. Although various virulence factors of M. tuberculosis have been identified, its pathogenesis remains incompletely understood. TlyA is a virulence factor in several bacterial infections and is evolutionarily conserved in many Gram-positive bacteria, but its function in M. tuberculosis pathogenesis has not been elucidated. Here, we report that TlyA significantly contributes to the pathogenesis of M. tuberculosis. We show that a TlyA mutant M. tuberculosis strain induces increased IL-12 and reduced IL-1β and IL-10 cytokine responses, which sharply contrasts with the immune responses induced by wild type M. tuberculosis. Furthermore, compared with wild type M. tuberculosis, TlyA-deficient M. tuberculosis bacteria are more susceptible to autophagy in macrophages. Consequently, animals infected with the TlyA mutant M. tuberculosis organisms exhibited increased host-protective immune responses, reduced bacillary load, and increased survival compared with animals infected with wild type M. tuberculosis. Thus, M. tuberculosis employs TlyA as a host evasion factor, thereby contributing to its virulence.

Biology of IL-27 and its role in the host immunity against Mycobacterium tuberculosis

IL-27, a heterodimeric cytokine of IL-12 family, regulates both innate and adaptive immunity largely via Jak-Stat signaling. IL-27 can induce IFN-γ and inflammatory mediators from T lymphocytes and innate immune cells. IL-27 has unique anti-inflammatory properties via both Tr1 cells dependent and independent mechanisms. Here the role and biology of IL-27 in innate and adaptive immunity are summarized, with special interest with immunity against Mycobacterium tuberculosis.

A new recombinant BCG vaccine induces specific Th17 and Th1 effector cells with higher protective efficacy against tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) that is a major public health problem. The vaccine used for TB prevention is Mycobacterium bovis bacillus Calmette-Guérin (BCG), which provides variable efficacy in protecting against pulmonary TB among adults. Consequently, several groups have pursued the development of a new vaccine with a superior protective capacity to that of BCG. Here we constructed a new recombinant BCG (rBCG) vaccine expressing a fusion protein (CMX) composed of immune dominant epitopes from Ag85C, MPT51, and HspX and evaluated its immunogenicity and protection in a murine model of infection. The stability of the vaccine in vivo was maintained for up to 20 days post-vaccination. rBCG-CMX was efficiently phagocytized by peritoneal macrophages and induced nitric oxide (NO) production. Following mouse immunization, this vaccine induced a specific immune response in cells from lungs and spleen to the fusion protein and to each of the component recombinant proteins by themselves. Vaccinated mice presented higher amounts of Th1, Th17, and polyfunctional specific T cells. rBCG-CMX vaccination reduced the extension of lung lesions caused by challenge with Mtb as well as the lung bacterial load. In addition, when this vaccine was used in a prime-boost strategy together with rCMX, the lung bacterial load was lower than the result observed by BCG vaccination. This study describes the creation of a new promising vaccine for TB that we hope will be used in further studies to address its safety before proceeding to clinical trials.