Modulation of riboflavin biosynthesis and utilization in mycobacteria.

Unlabelled: Riboflavin (vitamin B) is the precursor of the flavin coenzymes, FAD and FMN, which play a central role in cellular redox metabolism. While humans must obtain riboflavin from dietary sources, certain microbes, including (Mtb), can biosynthesize riboflavin . Riboflavin precursors have also been implicated in the activation of mucosal-associated invariant T (MAIT) cells which recognize metabolites derived from the riboflavin biosynthesis pathway complexed to the MHC-I-like molecule, MR1.

Delivery of loaded MR1 monomer results in efficient ligand exchange to host MR1 and subsequent MR1T cell activation.

MR1-restricted T cells have been implicated in microbial infections, sterile inflammation, wound healing and cancer. Similar to other antigen presentation molecules, evidence supports multiple, complementary MR1 antigen presentation pathways. To investigate ligand exchange pathways for MR1, we used MR1 monomers and tetramers loaded with 5-(2-oxopropylideneamino)-6-d-ribitylaminouracil (5-OP-RU) to deliver the antigen.

Production of Proinflammatory Cytokines by CD4+ and CD8+ T Cells in Response to Mycobacterial Antigens among Children and Adults with Tuberculosis.

Tuberculosis (TB), caused by (Mtb), remains a leading cause of pediatric morbidity and mortality. Young children are at high risk of TB following Mtb exposure, and this vulnerability is secondary to insufficient host immunity during early life. Our primary objective was to compare CD4+ and CD8+ T-cell production of proinflammatory cytokines IFN-gamma, IL-2, and TNF-alpha in response to six mycobacterial antigens and superantigen staphylococcal enterotoxin B (SEB) between Ugandan adults with confirmed TB (n = 41) and young Ugandan children with confirmed (n = 12) and unconfirmed TB (n = 41), as well as non-TB lower respiratory tract infection (n = 39).

Modulation of riboflavin biosynthesis and utilization in mycobacteria.

Riboflavin (vitamin B) is the precursor of the flavin coenzymes, FAD and FMN, which play a central role in cellular redox metabolism. While humans must obtain riboflavin from dietary sources, certain microbes, including (Mtb), can biosynthesize riboflavin . Riboflavin precursors have also been implicated in the activation of mucosal-associated invariant T (MAIT) cells which recognize metabolites derived from the riboflavin biosynthesis pathway complexed to the MHC-I-like molecule, MR1.

Mycobacterial-specific secretion of cytokines and chemokines in healthcare workers with apparent resistance to infection with .

Background: Currently, diagnosis of latent TB infection (LTBI) is based on the secretion of IFN-γ in response to (Mtb) antigens, the absence of which is regarded as no infection. Some individuals appear to resist Mtb infection despite sustained exposure (resisters). In this study, we aimed to assess cytokines, chemokines and antibodies that may be associated with resistance to Mtb infection.

Deaza-modification of MR1 ligands modulates recognition by MR1-restricted T cells.

MR1-restricted T (MR1T) cells recognize microbial small molecule metabolites presented on the MHC Class I-like molecule MR1 and have been implicated in early effector responses to microbial infection. As a result, there is considerable interest in identifying chemical properties of metabolite ligands that permit recognition by MR1T cells, for consideration in therapeutic or vaccine applications. Here, we made chemical modifications to known MR1 ligands to evaluate the effect on MR1T cell activation.

The Missing Link in Correlates of Protective Tuberculosis Immunity: Recognizing the Infected Cell.

For most vaccination studies, the assessment of vaccine-induced CD4 and CD8 T cells has relied upon the measurement of antigen-specific polyfunctional cells, typically using recombinant antigen or peptide pools. However, this approach leaves open the question as to whether or not these cells are responsive to the Mtb-infected cell within the context of Mtb infection and hence leaves open the possibility that a key parameter of vaccine immunogenicity may be overlooked. In this review, we discuss the case that these measurements almost certainly over-estimate the capacity of both CD4 and CD8 T cells to recognize the Mtb-infected cell.

Donor Unrestricted T Cells: Linking innate and adaptive immunity.

Donor Unrestricted T Cells (DURTs) are characterized by their use of antigen presentation molecules that are often invariant. As these cells recognize diverse mycobacterial antigens, often found in BCG, these cells have the potential to either serve as targets for vaccination, or as a means to enable the induction of traditional T and B cell immunity. Here, we will review specific DURT family members, and their relationship to BCG.

Functional and Activation Profiles of Mucosal-Associated Invariant T Cells in Patients With Tuberculosis and HIV in a High Endemic Setting.

MAIT cells are non-classically restricted T lymphocytes that recognize and rapidly respond to microbial metabolites or cytokines and have the capacity to kill bacteria-infected cells. Circulating MAIT cell numbers generally decrease in patients with active TB and HIV infection, but findings regarding functional changes differ. We conducted a cross-sectional study on the effect of HIV, TB, and HIV-associated TB (HIV-TB) on MAIT cell frequencies, activation and functional profile in a high TB endemic setting in South Africa.

T cell receptor diversity, specificity and promiscuity of functionally heterogeneous human MR1-restricted T cells.

The monomorphic MHC-class I-like molecule, MR1, presents small metabolites to T cells. MR1 is the restriction element for microbe-reactive mucosal-associated invariant T (MAIT) cells. MAIT cells have limited TCR usage, including a semi-invariant TCR alpha chain and express high levels of CD161 and CD26.

Postnatal Expansion, Maturation, and Functionality of MR1T Cells in Humans.

MR1-restricted T (MR1T) cells are defined by their recognition of metabolite antigens presented by the monomorphic MHC class 1-related molecule, MR1, the most highly conserved MHC class I related molecule in mammalian species. Mucosal-associated invariant T (MAIT) cells are the predominant subset of MR1T cells expressing an invariant TCR α-chain, TRAV1-2. These cells comprise a T cell subset that recognizes and mediates host immune responses to a broad array of microbial pathogens, including .

Clonal enrichments of Vδ2- γδ T cells in Mycobacterium tuberculosis-infected human lungs.

Unconventional T cell subsets, including donor-unrestricted T cells (DURTs) and γδ T cells, are promising new players in the treatment and prevention of infectious diseases. In this issue of the JCI, Ogongo et al. used T cell receptor (TCR) sequencing to characterize unconventional T cell subsets in surgical lung resections and blood from Mycobacterium tuberculosis-infected (Mtb-infected) individuals with and without HIV coinfection.

New Concepts in Tuberculosis Host Defense.

Tuberculosis (TB) host defense depends on cellular immunity, including macrophages and adaptively acquired CD4 and CD8 T cells. More recently, roles for new immune components, including neutrophils, innate T cells, and B cells, have been defined, and the understanding of the function of macrophages and adaptively acquired T cells has been advanced. Moreover, the understanding of TB immunology elucidates TB infection and disease as a spectrum.

MR1 displays the microbial metabolome driving selective MR1-restricted T cell receptor usage.

MR1-restricted T cells (MR1Ts) are a T cell subset that recognize and mediate host defense to a broad array of microbial pathogens, including respiratory pathogens (e.g., , , ) and enteric pathogens (e.

Identification and Evaluation of Novel Protective Antigens for the Development of a Candidate Tuberculosis Subunit Vaccine.

The development of a vaccine against tuberculosis (TB), a disease caused by , is urgently needed. The only currently available vaccine, BCG, has variable efficacy. One approach in the global vaccine development effort is focused on boosting BCG using subunit vaccines.

T cell recognition of Mycobacterium tuberculosis peptides presented by HLA-E derived from infected human cells.

HLA-E is a non-conventional MHC Class I molecule that has been recently demonstrated to present pathogen-derived ligands, resulting in the TCR-dependent activation of αβ CD8+ T cells. The goal of this study was to characterize the ligandome displayed by HLA-E following infection with Mycobacterium tuberculosis (Mtb) using an in-depth mass spectrometry approach. Here we identified 28 Mtb ligands derived from 13 different source proteins, including the Esx family of proteins.

Polyfunctional CD4 T Cells As Targets for Tuberculosis Vaccination.

Tuberculosis (TB), caused by (Mtb), remains a leading cause of morbidity and mortality worldwide, despite the widespread use of the only licensed vaccine, Bacille Calmette Guerin (BCG). Eradication of TB will require a more effective vaccine, yet evaluation of new vaccine candidates is hampered by lack of defined correlates of protection. Animal and human studies of intracellular pathogens have extensively evaluated polyfunctional CD4 T cells producing multiple pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-2) as a possible correlate of protection from infection and disease.

Comprehensive definition of human immunodominant CD8 antigens in tuberculosis.

Despite widespread use of the Bacillus Calmette-Guerin vaccine, tuberculosis, caused by infection with , remains a leading cause of morbidity and mortality worldwide. As CD8 T cells are critical to tuberculosis host defense and a phase 2b vaccine trial of modified vaccinia Ankara expressing Ag85a that failed to demonstrate efficacy, also failed to induce a CD8 T cell response, an effective tuberculosis vaccine may need to induce CD8 T cells. However, little is known about CD8, as compared to CD4, antigens in tuberculosis.

HLA-E Presents Glycopeptides from the Mycobacterium tuberculosis Protein MPT32 to Human CD8 T cells.

Infection with Mycobacterium tuberculosis (Mtb), the bacterium that causes tuberculosis, remains a global health concern. Both classically and non-classically restricted cytotoxic CD8 T cells are important to the control of Mtb infection. We and others have demonstrated that the non-classical MHC I molecule HLA-E can present pathogen-derived peptides to CD8 T cells.

Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children.

Background: Individuals infected with Mycobacterium tuberculosis (Mtb) may develop symptoms and signs of disease (tuberculosis disease) or may have no clinical evidence of disease (latent tuberculosis infection [LTBI]). Tuberculosis disease is a leading cause of infectious disease morbidity and mortality worldwide, yet many questions related to its diagnosis remain.

Methods: A task force supported by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America searched, selected, and synthesized relevant evidence.

Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children.

Background: Individuals infected with Mycobacterium tuberculosis (Mtb) may develop symptoms and signs of disease (tuberculosis disease) or may have no clinical evidence of disease (latent tuberculosis infection [LTBI]). Tuberculosis disease is a leading cause of infectious disease morbidity and mortality worldwide, yet many questions related to its diagnosis remain.

Methods: A task force supported by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America searched, selected, and synthesized relevant evidence.

Adenovirally-Induced Polyfunctional T Cells Do Not Necessarily Recognize the Infected Target: Lessons from a Phase I Trial of the AERAS-402 Vaccine.

The development of a vaccine for Mycobacterium tuberculosis (Mtb) has been impeded by the absence of correlates of protective immunity. One correlate would be the ability of cells induced by vaccination to recognize the Mtb-infected cell. AERAS-402 is a replication-deficient serotype 35 adenovirus containing DNA expressing a fusion protein of Mtb antigens 85A, 85B and TB10.