Human Mycobacterial Infection Research Articles

Nanoparticle delivery through the BBB in central nervous system tuberculosis.

Recent advances in Nanotechnology have revolutionized the production of materials for biomedical applications. Nowadays, there is a plethora of nanomaterials with potential for use towards improvement of human health. On the other hand, very little is known about how these materials interact with biological systems, especially at the nanoscale level, mainly because of the lack of specific methods to probe these interactions. In this review, we will analytically describe the journey of nanoparticles (NPs) through the brain, starting from the very first moment upon injection. We will preliminarily provide a brief overlook of the physicochemical properties of NPs. Then, we will discuss how these NPs interact with the body compartments and biological barriers, before reaching the blood-brain barrier (BBB), the last gate guarding the brain. Particular attention will be paid to the interaction with the biomolecular, the bio-mesoscopic, the (blood) cellular, and the tissue barriers, with a focus on the BBB. This will be framed in the context of brain infections, especially considering central nervous system tuberculosis (CNS-TB), which is one of the most devastating forms of human mycobacterial infections. The final aim of this review is not a collection, nor a list, of current literature data, as it provides the readers with the analytical tools and guidelines for the design of effective and rational NPs for delivery in the infected brain.

Mycobacterial infection induces eosinophilia and production of α-defensin by eosinophils in mice

It has been well known in humans that eosinophil infiltration into the site of inflammation and eosinophilia occur in mycobacterial infections. However, the role of eosinophils against the mycobacterium is unclear. We showed in previous study that in situ mouse eosinophils infiltrated into tissues produce α-defensin, an anti-bacterial peptide. We investigated in this study whether eosinophils reacting to mycobacteria produce α-defensin in mice and whether it can be used as a model. We showed that mycobacterial infection induced blood eosinophilia and infiltration of α-defensin producing eosinophils that to surround mycobacteria at the site of infection. These findings were usually seen during human mycobacterial infection. We established a good model to study host defense mechanism against mycobacteria through α-defensin via eosinophils.

Validation of a CD1b tetramer assay for studies of human mycobacterial infection or vaccination

CD1 tetramers loaded with lipid antigens facilitate the identification of rare lipid-antigen specific T cells present in human blood and tissue. Because CD1 proteins are structurally non-polymorphic, these tetramers can be applied to genetically diverse human populations, unlike MHC-I and MHC-II tetramers. However, there are no standardized assays to quantify and characterize lipid antigen-specific T cells present within clinical samples. We incorporated CD1b tetramers loaded with the mycobacterial lipid glucose monomycolate (GMM) into a multi-parameter flow cytometry assay. Using a GMM-specific T-cell line, we demonstrate that the assay is linear, reproducible, repeatable, precise, accurate, and has a limit of detection of approximately 0.007%. Having formally validated this assay, we performed a cross-sectional study of healthy U.S. controls and South African adolescents with and without latent tuberculosis infection (LTBI). We show that GMM-specific T cells are specifically detected in South African subjects with LTBI and not in U.S. healthy controls. This assay can be expanded to include additional tetramers or phenotypic markers to characterize GMM-specific T cells in studies of mycobacterial infection, disease, or vaccination.

Fishing for Answers in Human Mycobacterial Infections

Two recent studies (Cambier etal., 2017; Madigan etal., 2017) reveal invivo functions for specific phenolic glycolipids (PGLs) in the mycobacteria that cause tuberculosis or leprosy. M.tuberculosis (and M.marinum) PGL promotes bacterial spread to growth-permissive macrophages, while M.leprae PGL-1 induces macrophages to cause nerve demyelination characteristic of human leprosy.

Drug testing in mouse models of tuberculosis and nontuberculous mycobacterial infections

Mice as a species are susceptible to tuberculosis infection while mouse inbred strains present wide spectrum of susceptibility/resistance to this infection. However, non-tuberculosis Mycobacterial infections usually cannot be modeled in mice of common inbred strains. Introduction of specific properties, such as gene mutations, recombinants, targeted gene knockouts significantly extended the use of mice to mimic human Mycobacterial infections, including non-tuberculosis ones. This review describes the available mouse models of tuberculosis and non-tuberculosis infections and drug therapy in these models. Mouse models of non-tuberculosis infections are significantly less developed than tuberculosis models, hampering the development of therapies.

Depletion of IL-22 during culture enhanced antigen-driven IFN-γ production by CD4+T cells from patients with active TB

In this study, we mainly investigated the expression of IFN-γ and IL-22-producing CD4+T cells, the relationship between the two cytokines in human tuberculosis. We showed that IFN-γ and IL-22 were induced by human mycobacterial infection. Besides, CD4+T cells expressing IFN-γ and IL-22 were significantly elevated following PPD stimulation. In addition, IFN-γ and IL-22 -expressing CD4+T cells were distinct from each other. We also found that there was a reciprocal relationship between IFN-γ and IL-22 production. The production of IL-22 was markedly enhanced in the absence of IFN-γ, also, the expression of IFN-γ was increased when the IL-22 signaling was inhibited by monoclonal anti-IL-22 mAb. Furthermore, data revealed that the detectable IL-22 affected the phynotype of IFN-γ+CD4+T cells. IL-22 induced up-regulation of CD27 expression in IFN-γ+CD4+T cells, which might further confirm that IL-22 had an effect on the response of IFN-γ. Thus, this work provides a previous unknown relationship between IFN-γ and IL-22 in human TB disease.

NOD2 triggers an interleukin-32–dependent human dendritic cell program in leprosy

It is unclear whether the ability of the innate immune system to recognize distinct ligands from a single microbial pathogen via multiple pattern recognition receptors (PRRs) triggers common pathways or differentially triggers specific host responses. In the human mycobacterial infection leprosy, we found that activation of monocytes via nucleotide-binding oligomerization domain-containing protein 2 (NOD2) by its ligand muramyl dipeptide, as compared to activation via heterodimeric Toll-like receptor 2 and Toll-like receptor 1 (TLR2/1) by triacylated lipopeptide, preferentially induced differentiation into dendritic cells (DCs), which was dependent on a previously unknown interleukin-32 (IL-32)-dependent mechanism. Notably, IL-32 was sufficient to induce monocytes to rapidly differentiate into DCs, which were more efficient than granulocyte-macrophage colony-stimulating factor (GM-CSF)-derived DCs in presenting antigen to major histocompatibility complex (MHC) class I-restricted CD8(+) T cells. Expression of NOD2 and IL-32 and the frequency of CD1b(+) DCs at the site of leprosy infection correlated with the clinical presentation; they were greater in patients with limited as compared to progressive disease. The addition of recombinant IL-32 restored NOD2-induced DC differentiation in patients with the progressive form of leprosy. In conclusion, the NOD2 ligand-induced, IL-32-dependent DC differentiation pathway contributes a key and specific mechanism for host defense against microbial infection in humans.

New Insights into Lipidic Secondary Metabolites in Mycobacteria

Tuberculosis and some other mycobacterial infections remain a tremendous threat to mankind. Pathogenic mycobacteria are able to survive within the hosts even for years, and a chemical and biological basis for their adaptation mechanisms is now beginning to be unraveled. The lipid-rich cell wall of mycobacteria contains structurally diverse glycolipids that comprise the outermost layer and interact directly with the environments. Recent studies have revealed that production of these surface-exposed glycolipids is mediated by enzymes utilized typically for biosynthesis of secondary metabolites. As for defined secondary metabolites in plants, bacteria and fungi that are often produced in response to environmental stresses and play a critical role in protection from their enemies, production of these cell wall glycolipids is influenced significantly by external factors to which mycobacteria are exposed. Identification of lipidic secondary metabolites in mycobacteria and elucidation of their biosynthetic pathways and biological functions now provide a clue to how mycobacteria have evolved to survive and grow both in host tissues as well as in natural environments. Further, what is learned from these studies is of important medical implications, including the development of a novel type of vaccines and therapeutic agents against human mycobacterial infections. Keywords: Mycobacteria, lipids, secondary metabolite, mycolic acid, polyketide synthase, non-ribosomal peptide synthetase, Secondary Metabolites, Gram-positive, aerobic bacilli, Mycobacterium, taxonomic genus, Mycobacteriaceae, hydrophobic cell, Mycobacterium tuberculosis, pathogensis, mycobacterial infection, galactose/arabinose polysaccharide, peptidoglycan, framework, mycolic acids, alkyl--hydroxy fatty acids, arabinose termini, sugar, Nocardia, Rhodococcus, Corynebacterium, carbon chains, primary metabolites, pH, density, fungi, Mycolate Derivatives, arabinogalactan-linked, ester-linked, alcohol group, Phthiocerol Derivatives, conjugated, Mannose Phosphomycoketide, anomer, isomers, Glycopeptidolipids, serotype-nonspecific, immune system, non-ribosomal peptide, acyl carrier protein, catalyzes, FAS system, enzymes, biological energy, eukaryotic type, mitochondria, chloroplasts, condensation processes, atypical, hydrophobic, Microbes, granuloma, Rhodococcus, chemotherapy, silica gel, peripheral blood, vaccines, biosurfactants, antibiotic agents

A novel identification scheme for genus Mycobacterium, M. tuberculosis complex, and seven mycobacteria species of human clinical impact

Recently, the incidence of human mycobacterial infections due to species other than M. tuberculosis has increased worldwide. Since disease control depends on appropriate antimicrobial therapy, the precise identification of these species of clinical importance has become a major public health concern. Identification of mycobacteria has been hampered because of the lack of specific, rapid, and inexpensive methods. Therefore, we aimed at designing and validating a bacterial lysate-based polymerase chain reaction identification scheme. This scheme can classify clinical isolates into: (1) the genus Mycobacterium, (2) the M. tuberculosis complex, (3) the nontuberculous mycobacteria, and (4) the species M. avium, M. intracellulare, M. abscessus, M. chelonae, M. fortuitum and M. bovis of clinical importance, and M. gordonae, the most commonly encountered nonpathogenic species in clinical laboratories. By using M. fortuitum and M. avium lysates as models, the method sensitivity was determined to be 372 pg of DNA. In a blind parallel comparison between our approach and conventional biochemical tests, both assays correctly categorized 75 patient's mycobacterial isolates. However, our approach only required 4-9 h for categorization compared with at least 15 days by conventional tests. Furthermore, our methodology could also detect M. fortuitum and M. avium from liquid cultures, after only 2 and 6 days, respectively, of incubation. Our new identification scheme is therefore sensitive, specific, rapid, and economic. Additionally, it can help to provide proper treatment to patients, to control these diseases, and to improve our knowledge of the epidemiology of mycobacteriosis, all urgently needed, particularly in developing countries.

Distinct, Specific IL-17- and IL-22-Producing CD4+ T Cell Subsets Contribute to the Human Anti-Mycobacterial Immune Response

We investigated whether the proinflammatory T cell cytokines IL-17 and IL-22 are induced by human mycobacterial infection. Remarkably, >20% of specific cytokine-producing CD4(+) T cells in peripheral blood of healthy, mycobacteria-exposed adults expressed IL-17 or IL-22. Specific IL-17- and IL-22-producing CD4(+) T cells were distinct from each other and from Th1 cytokine-producing cells. These cells had phenotypic characteristics of long-lived central memory cells. In patients with tuberculosis disease, peripheral blood frequencies of these cells were reduced, whereas bronchoalveolar lavage fluid contained higher levels of IL-22 protein compared with healthy controls. IL-17 was not detected in this fluid, which may be due to suppression by Th1 cytokines, as PBMC IL-17 production was inhibited by IFN-gamma in vitro. However, Th1 cytokines had no effect on IL-22 production in vitro. Our results imply that the magnitude and complexity of the anti-mycobacterial immune response have historically been underestimated. IL-17- and IL-22-producing CD4(+) T cells may play important roles in the human immune response to mycobacteria.

The evolving story of Mycobacterium tuberculosis clade members detected in fish

Advances in molecular analyses have permitted documentation of an increasing spectrum of mycobacteria infecting fish. Although some of these mycobacteria are not closely related, several species belong to the Mycobacterium tuberculosis clade. One member of the clade, M. marinum, is well known as an agent of piscine mycobacteriosis. Three other clade species, M. shottsii, M. pseudoshottsii and M. 'chesapeaki', have recently been identified as predominant disease agents in a widespread, continuing epizootic in wild striped bass of the Chesapeake Bay. A fifth clade member, M. ulcerans, has recently been indirectly detected in wild, African cichlid fish. As M. ulcerans is the third most common human mycobacterial infection worldwide, even such indirect evidence of M. ulcerans in fish must be more thoroughly investigated. Complicating the differentiation of these clade members is the growing recognition of intraspecies and interspecies variation in phenotypes, genes and virulence. Thus, researchers must be aware of the variety of piscine isolates within the M. tuberculosis clade. This review summarizes the methods of detection and differentiation for this important group of mycobacteria.

Down-modulation of mycobacterial-induced IL-1 beta production in human mononuclear cells by IL-4.

Tuberculosis is characterized by a cellular immune response mediated by various cytokines, including IL-1 beta released by stimulated mononuclear cells. It is now well established that IL-I beta plays an important role in local and systemic inflammatory response in tuberculosis. Here we have demonstrated, for the first time, that addition to IL-4 to human mononuclear cells obtained from 11 healthy bacille Calmette-Guérin (BCG)-vaccinated donors reduced BCG-induced production of IL-1 beta by 91.46 +/- 2.2%. This inhibitory effect was found highly significant (P less than 0.001) and was dose-dependent. The effect of IL-4 on the secretion of IL-1 beta was specific, since a complete reversion was obtained with a neutralizing MoAb to human IL-4. In addition, this inhibitory effect was not attributed to a cytotoxic effect, since trypan blue exclusion studies indicated no loss of cell viability in response to IL-4. Interestingly, the induction of IL-1 beta was regulated by IL-4, at least in part, by direct mechanism mediated through the extracellular domain of the 130-kD IL-4 receptor, as demonstrated by incubation of the mononuclear cells with the neutralizing anti-IL-4 receptor MoAb. Finally, a significant down-regulation of IL-1 beta secretion was observed in hsp70-stimulated mononuclear cells cultured with IL-4. Further experimental work is needed to establish the relevance of IL-4 in human mycobacterial infection in vivo. However, an understanding of the mechanisms that control IL-1 beta secretion in human mycobacterial infections is essential to understand the pathogenesis of tuberculosis.

Use of Roche Amplicor and multiplex PCR for diagnosis of human mycobacterial infections

The ability to determine various mycobacterial species rapidly and precisely is important for the control and prevention of mycobacterial infections in the human population. In the present study, we evaluated the Roche Amplicor Mycobacterium tuberculosis test and the Amplicor M. avium/M. intracellulare test, as well as a multiplex PCR, for diagnosis of mycobacterial infections using 86 clinical (sputum and bronchial washing) and culture specimens from 50 human patients. The Roche Amplicor M. tuberculosis test and the Amplicor M. avium/M. intracellulare test appeared to be highly sensitive and specific for direct detection of M. tuberculosis and M. avium/M. intracellulare, respectively, from clinical specimens. The use of culture derivatives was not necessary. Nonetheless, the Roche Amplicor tests had limited value in identifying other mycobacterial species as these mycobacteria invariably displayed negative reactions in the assays. The multiplex PCR, on the other hand, was capable of differentiating M. tuberculosis, M. avium and M. intracellulare from other mycobacterial species using culture specimens at relatively low cost. However, the multiplex PCR generated inconsistent results when clinical samples were used. Only 42 (48.8%) of the 86 sputum and bronchial washing specimens showed clear, specific electrophoretic bands in the multiplex PCR. Future optimisation of a hybridisation-based detection system is essential for enhanced identification of mycobacteria directly from clinical specimens by the multiplex PCR.

Augmentation of selective monocyte functions in tuberculosis.

Four monocyte functions were studied in patients with pulmonary tuberculosis and in healthy subjects. Circulating monocytes from four of six patients with tuberculosis functioned as suppressor cells; depletion of adherent cells from mononuclear cells obtained from the peripheral blood of these patients resulted in a 37-fold enhancement in tuberculin purified protein derivative-induced incorporation of [3H]thymidine. Monocytes from patients with tuberculosis exhibited increased adherence to plastic. Plasma from patients with tuberculosis also increased the adherence of monocytes from healthy subjects. However, basal and lipopolysaccharide-stimulated production of prostaglandin E2 by monocytes and tumoricidal activity were not altered in patients with tuberculosis. Thus, tuberculosis in humans is associated with the enhancement of selective monocyte functions. The dissociation in monocyte effector functions in human mycobacterial infection has potential implications not only for the course of tuberculosis but also for immunoadjuvant therapy.