Mycobacterium tuberculosis Latent Antigen Rv2029c from the Multistage DNA Vaccine A39 Drives TH1 Responses via TLR-mediated Macrophage Activation

TB/FLU-06E Influenza Vector-Based Vaccine in the Complex Therapy of Drug-Susceptible and Drug-Resistant Experimental Tuberculosis

The steady rise of drug-resistant tuberculosis (TB), which renders standard therapy regimens ineffective, necessitates the development of innovative treatment approaches. Immunotherapeutic vaccines have the potential to effectively regulate the anti-TB immune response and enhance the efficacy of anti-TB treatment. In the present study, we aimed to evaluate the potency of the mucosal vector vaccine TB/FLU-06E as part of a complex treatment regimen for drug-susceptible (DS) or drug-resistant (DR) tuberculosis in C57BL/6 mice. Incorporating TB/FLU-06E into the treatment protocol significantly increased the effectiveness of therapy for both forms of tuberculosis. It was evidenced by higher survival rates and reduced pulmonary bacterial load (1.83 lg CFU for DS tuberculosis and 0.93 lg CFU for DR tuberculosis). Furthermore, the treatment reduced pathomorphological lesions in the lungs and stimulated the local and systemic T-helper 1 (Th1) and cytotoxic T-lymphocyte (CTL) anti-TB immune responses. Thus, therapeutic immunization with the TB/FLU-06E vaccine significantly enhances the efficacy of tuberculosis treatment, which is particularly important in DR tuberculosis.

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

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

Changes in the Immune Phenotype and Gene Expression Profile Driven by a Novel Tuberculosis Nanovaccine: Short and Long-Term Post-immunization

Deciphering protection mechanisms against Mycobacterium tuberculosis (Mtb) remains a critical challenge for the development of new vaccines and therapies. We analyze the phenotypic and transcriptomic profile in lung of a novel tuberculosis (TB) nanoparticle-based boosting mucosal vaccine Nano-FP1, which combined to BCG priming conferred enhanced protection in mice challenged with low-dose Mtb. We analyzed the vaccine profile and efficacy at short (2 weeks), medium (7 weeks) and long term (11 weeks) post-vaccination, and compared it to ineffective Nano-FP2 vaccine. We observed several changes in the mouse lung environment by both nanovaccines, which are lost shortly after boosting. Additional boosting at long-term (14 weeks) recovered partially cell populations and transcriptomic profile, but not enough to enhance protection to infection. An increase in both total and resident memory CD4 and CD8 T cells, but no pro-inflammatory cytokine levels, were correlated with better protection. A unique gene expression pattern with differentially expressed genes revealed potential pathways associated to the immune defense against Mtb. Our findings provide an insight into the critical immune responses that need to be considered when assessing the effectiveness of a novel TB vaccine.

Application of antigenic biomarkers for Mycobacterium tuberculosis

The study and characterization of biomolecules involved in the interaction between mycobacteria and their hosts are crucial to determine their roles in the invasion process and provide basic knowledge about the biology and pathogenesis of disease. Promising new biomarkers for diagnosis and immunotherapy have emerged recently. Mycobacterium is an ancient pathogen that has developed complex strategies for its persistence in the host and environment, likely based on the complexity of the network of interactions between the molecules involved in infection. Several biomarkers have received recent attention in the process of developing rapid and reliable detection techniques for tuberculosis. Among the most widely investigated antigens are CFP-10 (10-kDa culture filtrate protein), ESAT-6 (6-kDa early secretory antigenic target), Ag85A, Ag85B, CFP-7, and PPE18. Some of these antigens have been proposed as biomarkers to assess the key elements of the response to infection of both the pathogen and host. The design of novel and accurate diagnostic methods is essential for the control of tuberculosis worldwide. Presently, the diagnostic methods are based on the identification of molecules in the humoral response in infected individuals. Therefore, these tests depend on the capacity of the host to develop an immune response, which usually is heterogeneous. In the last 20 years, special attention has been given to the design of multiantigenic diagnostic methods to improve the levels of sensitivity and specificity. In this review, we summarize the state of the art in the study and use of mycobacterium biomolecules with the potential to support novel tuberculosis control strategies.

Can immunization with Bacillus Calmette-Guérin be improved for prevention or therapy and elimination of chronic Mycobacterium tuberculosis infection?

Introduction: Tuberculosis (TB) is one of the most prevalent infectious diseases in the world. Current vaccination with BCG can prevent meningeal and disseminated TB in children. However, success against latent pulmonary TB infection (LTBI) or its reactivation is limited. Evidence suggests that there may be means to improve the efficacy of BCG raising the possibility of developing new vaccine candidates against LTBI.Areas covered: BCG improvements include the use of purified mycobacterial immunogenic proteins, either from an active or dormant state, as well as expressing those proteins from recombinant BCG strains that harvor those specific genes. It also includes boost protein mixtures with synthetic adjuvants or within liposomes, as a way to increase a protective immune response during chronic TB produced in laboratory animal models. References cited were chosen from PubMed searches.Expertopinion: Strategies aiming to improve or boost BCG have been receiving increased attention. With the advent of -omics, it has been possible to dissect several specific stages during mycobacterial infection. Recent experimental models of disease, diagnostic and immunological data obtained from individual M. tuberculosis antigens could introduce promising developments for more effective TB vaccines that may contribute to eliminating the hidden (latent) form of this infectious disease.

Secreted Rv1768 From RD14 of Mycobacterium tuberculosis Activates Macrophages and Induces a Strong IFN-γ-Releasing of CD4+ T Cells

As the first line defensive mediators against Mycobacterium tuberculosis (M.tb) infection, macrophages can be modulated by M.tb to influence innate and adaptive immunity. Recently, we have identified several potential immunodominant T-cell antigens from the region of deletion (RD) of M.tb H37Rv, including Rv1768 from RD14. In this study, we further determined that Rv1768 was highly conserved among virulent M.tb strains and mainly distributed as a secreted protein. Exposure to recombinant purified Rv1768 (rRv1768) induced apoptosis of bone marrow derived macrophages (BMDMs) but showed no dose-dependent manner. Regarding macrophage activation, significant higher levels of iNOS and pro-inflammatory cytokines (like IL-6 and TNF-α) were detected in rRv1768-challenged BMDMs, whereas arginase 1 (Arg1) expression was markedly decreased. Meanwhile, MHC-II expression and antigen presentation activity of BMDMs were also enhanced by rRv1768 stimulation, leading to significantly increased IFN-γ expression of CD4⁺ T cells isolated from H37Rv-infected mice. It is worthy to note that Rv1768-induced IFN-γ production of peripheral blood mononuclear cells (PBMCs) and Rv1768-specific immunoglobulins was specifically observed in H37Rv-infected mice, but not BCG-infected or normal mice. Analysis of clinical blood samples further revealed that Rv1768 had a higher sensitivity and specificity (91.38 and 96.83%) for tuberculosis diagnosis than the results obtained from clinical CFP10 and ESAT6 peptides (CE)-based enzyme-linked immunospot (ELISPOT) assay. The area under ROC curve of Rv1768 was 0.9618 (95% CI: 0.919–1.000) when cutoff value set as 7 spots. In addition, Rv1768-specific IgG and IgM also exhibited moderate diagnostic performance for tuberculosis compared with CE specific antibodies. Our data suggest that Rv1768 is an antigen that strongly activates macrophages and has potential to serve as a novel ELISPOT-based TB diagnostic agent.

DosR antigen Rv1737c induces activation of macrophages dependent on the TLR2 pathway

Latent Mycobacterium tuberculosis (Mtb) infection (LTBI) is the main clinical manifestation after Mtb exposure. During the latent phase, Mtb retards the attempts of eradication by the host immune system. The dormancy survival regulator (DosR) is held as essential for Mtb persistence. Rv1737c is predominantly expressed by the Mtb in latent infection. However, the role of Rv1737c in the immune evasion is still largely unknown. In this study, we have characterized the Rv1737c functions in the recruitment and activation of macrophages, which play a cardinal role in the innate and adaptive immunity. For the first time, we have revealed that Rv1737c induced the tolerogenic phenotype of macrophages by upregulating the expression of indoleamine 2,3-dioxygenase 1 (IDO1). Rv1737c-activated macrophages upregulated interleukin (IL)-4, IL-10, and Foxp3 T cells proliferation in vitro. Furthermore, the interaction of Rv1737c with macrophages was found to depend on the Toll-like receptor 2 (TLR2) pathway. It augmented nuclear factor κB (NF-κB) phosphorylation and co-stimulatory molecule expression. Thus, this study provides a crucial insight into a strategy adopted by Mtb to survive in the host by inducing tolerogenic macrophage expansion.

A Systematic Review on Novel Mycobacterium tuberculosis Antigens and Their Discriminatory Potential for the Diagnosis of Latent and Active Tuberculosis

Background: Current immunodiagnostic tests for tuberculosis (TB) are based on the detection of an immune response toward mycobacterial antigens injected into the skin or following an in-vitro simulation in interferon gamma-release assays. Both tests have limited sensitivity and are unable to differentiate between tuberculosis infection (LTBI) and active tuberculosis disease (aTB). To overcome this, the use of novel Mycobacterium tuberculosis (M. tuberculosis) stage-specific antigens for the diagnosis of LTBI and aTB has gained interest in recent years. This review summarizes current evidence on novel antigens used for the immunodiagnosis of tuberculosis and discrimination of LTBI and aTB. In addition, results on measured biomarkers after stimulation with novel M. tuberculosis antigens were also reviewed.

Methods: A systematic literature review was performed in Pubmed, EMBASE and web of science searching articles from 2000 up until December 2017. Only articles reporting studies in humans using novel antigens were included.

Results: Of 1,533 articles screened 34 were included in the final analysis. A wide range of novel antigens expressed during different stages and types of LTBI and aTB have been assessed. M. tuberculosis antigens Rv0081, Rv1733c, Rv1737c, Rv2029c, Rv2031 and Rv2628, all encoded by the dormancy of survival regulon, were among the most widely studied antigens and showed the most promising results. These antigens have been shown to have best potential for differentiating LTBI from aTB. In addition, several studies have shown that the inclusion of cytokines other than IFN-γ can improve sensitivity.

Conclusion: There is limited evidence that the inclusion of novel antigens as well as the measurement of other biomarkers than IFN-γ may improve sensitivity and may lead to a discrimination of LTBI from aTB.