Control Of Mycobacteria Research Articles

PD-1 blockade exacerbates Mycobacterium tuberculosis infection in rhesus macaques.

Boosting immune cell function by targeting the coinhibitory receptor PD-1 may have applications in the treatment of chronic infections. Here, we examine the role of PD-1 during Mycobacterium tuberculosis (Mtb) infection of rhesus macaques. Animals treated with anti-PD-1 monoclonal antibody developed worse disease and higher granuloma bacterial loads compared with isotype control-treated monkeys. PD-1 blockade increased the number and functionality of granuloma Mtb-specific CD8 T cells. In contrast, Mtb-specific CD4 T cells in anti-PD-1-treated macaques were not increased in number or function in granulomas, expressed increased levels of CTLA-4, and exhibited reduced intralesional trafficking in live imaging studies. In granulomas of anti-PD-1-treated animals, multiple proinflammatory cytokines were elevated, and more cytokines correlated with bacterial loads, leading to the identification of a role for caspase 1 in the exacerbation of tuberculosis after PD-1 blockade. Last, increased Mtb bacterial loads after PD-1 blockade were found to associate with the composition of the intestinal microbiota before infection in individual macaques. Therefore, PD-1-mediated coinhibition is required for control of Mtb infection in macaques, perhaps because of its role in dampening detrimental inflammation and allowing for normal CD4 T cell responses.

Association of immune responses of Zebu and Holstein-Friesian cattle and resistance to mycobacteria in a BCG challenge model.

Mycobacterium bovis is the main cause of bovine tuberculosis (BTB) in cattle and can also infect humans. Zebu cattle are considered more resistant to some infectious diseases compared with Holstein‐Friesian (HF) cattle, including BTB. However, epidemiological studies may not take into account usage differences of the two types of cattle. HF cattle may suffer greater metabolic stress due to their more or less exclusive dairy use, whereas Zebu cattle are mainly used for beef production. In experiments conducted so far, the number of animals has been too small to draw statistically robust conclusions on the resistance differences between these cattle breeds. Here, we used a BCG challenge model to compare the ability of naïve and vaccinated Zebu and HF cattle to control/kill mycobacteria. Young cattle of both breeds with similar ages were housed in the same accommodation for the duration of the experiment. After correcting for multiple comparisons, we found no difference between naïve HF and Zebu (ρ = 0.862) cattle. However, there was a trend for vaccinated HF cattle to have lower cfu numbers than non‐vaccinated HF cattle (ρ = 0.057); no such trend was observed between vaccinated and non‐vaccinated Zebu cattle (ρ = 0.560). Evaluation of antigen‐specific IFNγ secretion by PBMC indicated that Zebu and HF cattle differed in their response to mycobacteria. Thus, whilst there may be difference in immune responses, our data indicate that with the number of animals included in the study and under the conditions used in this work, we were unable to measure any differences between Zebu and HF cattle in the overall control of mycobacteria. Whilst determination of different susceptibilities between Zebu and HF cattle using the BCG challenge model will require larger numbers of animals than the number of animals used in this experiment, these data should inform future experiments.

Interferon-Gamma Improves Macrophages Function against M. tuberculosis in Multidrug-Resistant Tuberculosis Patients.

Background. Mycobacterium tuberculosis (M. tuberculosis) that causes tuberculosis (TB) kills millions of infected people annually especially multidrug-resistant tuberculosis (MDR-TB). On infection, macrophages recognize the mycobacteria by toll-like receptor (TLR) followed by phagocytosis and control of mycobacteria. In addition, macrophages also secrete IL-12 to induce IFN-γ production by T, which, in turn, increases the phagocytosis and oxidative burst. Individuals with defects in innate or adaptive immunity exhibit increased susceptibility to M. tuberculosis. Understanding these immunologic mechanisms will help in TB control. We aimed to investigate the immunopathologic mechanisms in MDR-TB and role of recombinant human interferon-gamma (rhIFN-γ). Study Design and Methods. Monocyte-derived macrophages (MDMs) were generated from peripheral blood mononuclear cells of MDR-TB patients and healthy subjects and were investigated for immunologic response by ELISA and flow cytometry. Results. Different functional and molecular anomalies were observed in macrophages. In addition, a defective immune response to M. tuberculosis from the patient's MDMs was characterized, which in turn improved by pretreatment with rhIFN-γ. Conclusion. This work highlights the fact that rhIFN-γ improves macrophages function against M. tuberculosis and treatment of patients with poor responsiveness to TB therapy may be needed in future to include IFN-γ as adjuvant therapy after the full characterization of pathological and molecular mechanisms in these and in other more multidrug-resistant TB patients.

Environmental mycobacteria – Future directions

Understanding environmental mycobacteria and the diseases they cause is woefully lacking. The number of species, their ubiquity in nature and the heterogeneity of their effects on their human hosts have made this a formidable task.Diagnosis is difficult. Standard laboratory testing is controversial, and treatment lacks trial-based evidence. Uncertainty in epidemiology, pathogenesis, diagnosis, and treatment results in inconsistent clinical care for these diseases. The lack of tools to understand the organisms and diseases has stunted research in this field. Knowledge of nontuberculous mycobacteria pales compared to that of tuberculosis. Tuberculosis research and understanding have surged in recent years leading to better understanding, containment, and control of this disease. At the same time, diseases caused by nontuberculous mycobacteria have increased.The field of nontuberculous mycobacteria must learn from developing countries that have used technology to “leap-frog” over other technology that took decades to attain. “Omics” technology could be the key to raising the knowledge of nontuberculous mycobacteria to that of tuberculosis. Genome-based technology could replace the microbiology lab for diagnosis and drug sensitivity identification. It could vastly strengthen epidemiology, better define pathogenesis, effectively guide treatment, and accurately prognosticate outcomes.Genomics are already being used to track mycobacterial infections. Bacterial gene sequencing in patients with cystic fibrosis infected with Mycobacterium abscessus has shown the first human-to-human spread. Sequencing studies have separated out M. avium and M. intracellulare and have shown differences in pathogenicity. Studies on environmental isolation could yield clues to controlling these diseases by system modifications.Genomic approaches to pathogenesis have largely involved M. smegmatis, which has been used as a surrogate for M. tuberculosis in learning about the gene and protein changes that occur when bacteria go into a dormant state. Studies on M. ulcerans have identified factors related to its virulence.The mycobacterial diagnostic lab has used gene-based tests for several years, and there is a growing array of products available. Sequencing of the genes encoding the highly variable regions of bacterial DNA is rapid and accurate. Genotyping already can identify pathogenicity and response to antibiotics in a few instances; the future goal should be to identify sensitivity to a wide variety of organisms and antibiotics. This information will require clinical trials and time to validate it.An interferon gamma release assay for infection with nontuberculous mycobacteria is desperately needed. Success with tuberculosis was attained by finding bacterial antigens associated with virulence and invasive disease. This may be difficult because the damage caused by environmental mycobacteria tends to be epithelial and subepithelial. The cavities may be bronchiectatic in origin and deeper invasion may result from host reactions. Serologic testing has not yielded important clinical help for diseases caused by either M. tuberculosis or the nontuberculous mycobacteria, possibly because good bacterial or host response proteins have not been identified. This could change with a metabolomics approach. Genomic studies that give incremental gains may set the stage for major breakthroughs, but require coordination with good phenotyping. Tools are in place to open an exciting new era for understanding and control of mycobacteria.

Phagocyte NADPH oxidase, chronic granulomatous disease and mycobacterial infections.

Infection of humans with Mycobacterium tuberculosis remains frequent and may still lead to death. After primary infection, the immune system is often able to control M. tuberculosis infection over a prolonged latency period, but a decrease in immune function (from HIV to immunosenescence) leads to active disease. Available vaccines against tuberculosis are restricted to BCG, a live vaccine with an attenuated strain of M. bovis. Immunodeficiency may not only be associated with an increased risk of tuberculosis, but also with local or disseminated BCG infection. Genetic deficiency in the reactive oxygen species (ROS)-producing phagocyte NADPH oxidase NOX2 is called chronic granulomatous disease (CGD). CGD is among the most common primary immune deficiencies. Here we review our knowledge on the importance of NOX2-derived ROS in mycobacterial infection. A literature review suggests that human CGD patient frequently have an increased susceptibility to BCG and to M. tuberculosis. In vitro studies and experiments with CGD mice are incomplete and yielded - at least in part - contradictory results. Thus, although observations in human CGD patients leave little doubt about the role of NOX2 in the control of mycobacteria, further studies will be necessary to unequivocally define and understand the role of ROS.

Levels of anti-cytokine antibodies may be elevated in patients with pulmonary disease associated with non-tuberculous mycobacteria

Pulmonary disease due to non-tuberculous mycobacteria (NTM) is caused by several species (particularly Mycobacterium avium, Mycobacterium intracellulare) that are abundant in the environment. Th1 cytokines such as interferon (IFN)-γ are important in the control of mycobacteria, but in vitro production of IFN-γ is not deficient in adult patients with pulmonary NTM disease. Antibodies reactive with IFN-γ have been described in patients with disseminated NTM disease, but it is not clear whether they are common in pulmonary disease. Here we show that patients with pulmonary NTM have a higher level of anti-IFN-γ and anti-GM-CSF antibodies than healthy controls, although some controls also have high levels. Levels of anti-IFN-γ antibodies did not correlate with levels of total immunoglobulin. Longitudinal studies are required to determine whether anti-cytokine autoantibodies are consequence rather than a cause of pulmonary NTM disease.

Immunology and pathogenesis of childhood TB

! To discuss the range of immune mechanisms involved in the control of mycobacteria ! To provide review of studies conducted in the human host and in children in particular ! To illustrate the influence of age on immune function relevant to tuberculosis ! To present the immune mechanisms involved as a continuum of responses rather than as strictly compartmentalised ! To address the interplay of both host and mycobacterial factors in eliciting immune responses

In a Murine Tuberculosis Model, the Absence of Homeostatic Chemokines Delays Granuloma Formation and Protective Immunity

Mycobacterium tuberculosis infection (Mtb) results in the generation of protective cellular immunity and formation of granulomatous structures in the lung. CXCL13, CCL21, and CCL19 are constitutively expressed in the secondary lymphoid organs and play a dominant role in the homing of lymphocytes and dendritic cells. Although it is known that dendritic cell transport of Mtb from the lung to the draining lymph node is dependent on CCL19/CCL21, we show in this study that CCL19/CCL21 is also important for the accumulation of Ag-specific IFN-gamma-producing T cells in the lung, development of the granuloma, and control of mycobacteria. Importantly, we also show that CXCL13 is not required for generation of IFN-gamma responses, but is essential for the spatial arrangement of lymphocytes within granulomas, optimal activation of phagocytes, and subsequent control of mycobacterial growth. Furthermore, we show that these chemokines are also induced in the lung during the early immune responses following pulmonary Mtb infection. These results demonstrate that homeostatic chemokines perform distinct functions that cooperate to mediate effective expression of immunity against Mtb infection.

First Detection of Mycobacteria in African Rodents and Insectivores, Using Stratified Pool Screening

With the rising number of patients with human immunodeficiency virus (HIV)/AIDS in developing countries, the control of mycobacteria is of growing importance. Previous studies have shown that rodents and insectivores are carriers of mycobacteria. However, it is not clear how widespread mycobacteria are in these animals and what their role is in spreading them. Therefore, the prevalence of mycobacteria in rodents and insectivores was studied in and around Morogoro, Tanzania. Live rodents were trapped, with three types of live traps, in three habitats. Pieces of organs were pooled per habitat, species, and organ type (stratified pooling); these sample pools were examined for the presence of mycobacteria by PCR, microscopy, and culture methods. The mycobacterial isolates were identified using phenotypic techniques and sequencing. In total, 708 small mammals were collected, 31 of which were shrews. By pool prevalence estimation, 2.65% of the animals were carriers of mycobacteria, with a higher prevalence in the urban areas and in Cricetomys gambianus and the insectivore Crocidura hirta. Nontuberculous mycobacteria (Mycobacterium chimaera, M. intracellulare, M. arupense, M. parascrofulaceum, and Mycobacterium spp.) were isolated from C. gambianus, Mastomys natalensis, and C. hirta. This study is the first to report findings of mycobacteria in African rodents and insectivores and the first in mycobacterial ecology to estimate the prevalence of mycobacteria after stratified pool screening. The fact that small mammals in urban areas carry more mycobacteria than those in the fields and that potentially pathogenic mycobacteria were isolated identifies a risk for other animals and humans, especially HIV/AIDS patients, that have a weakened immune system.

Control of mycobacterial replication in human macrophages: roles of extracellular signal-regulated kinases 1 and 2 and p38 mitogen-activated protein kinase pathways.

Intracellular persistence of mycobacteria may result from an intricate balance between bacterial replication and signaling events leading to antimicrobial macrophage activities. Using human monocyte-derived macrophages, we investigated the relevance of mitogen-activated protein kinase activation for the growth control of Mycobacterium avium isolates differing in their abilities to multiply intracellularly. The highly replicative smooth transparent morphotype of M. avium strain 2151 induced significantly less p38 and extracellular signal-regulated kinases 1 and 2 (ERK1/2) phosphorylation than the smooth opaque morphotype of the same strain, which was gradually eliminated from macrophage cultures. Inhibition of the p38 pathway by highly specific inhibitors did not significantly affect mycobacterial replication within macrophages, regardless of the in vitro virulence of the M. avium strain. However, repression of the ERK1/2 pathway further enhanced intracellular growth of highly replicative M. avium strains, although it did not increase survival of the poorly replicating M. avium isolate. Inhibition of the ERK1/2 pathway resulted in decreased tumor necrosis alpha (TNF-alpha) secretion irrespective of the virulence of the M. avium isolate used for infection, revealing that TNF-alpha could have been only partially responsible for the control of intracellular M. avium growth. In conclusion, ERK1/2- and TNF-alpha-independent pathways are sufficient to limit intramacrophage growth of less-virulent M. avium strains, but early ERK1/2 activation in infected macrophages is critically involved in controlling the growth of highly replicative M. avium strains.

Mendelian susceptibility to mycobacterial infection in man.

Selective susceptibility to weakly pathogenic mycobacteria, such as bacillus Calmette-Guérin (BCG) vaccine and environmental non-tuberculous mycobacteria (NTM), has long been suspected to be a Mendelian disorder but its molecular basis remained elusive. Recently, mutations in the interferon-gamma receptor ligand-binding chain (IFN gamma R1), interferon-gamma receptor signaling chain (IFN gamma R2), Signal Transducer and Activator of Transcription-1 (STAT-1), interleukin-12 p40 subunit (IL-12 p40), and interleukin-12 receptor beta 1 chain (IL-12R beta 1) genes have been identified in a number of patients with severe BCG or NTM infection. Dominant or recessive alleles causing complete or partial cellular defects have been found to define nine different inheritable disorders. Although genetically distinct, these conditions are immunologically related and highlight the essential role of interferon gamma-mediated immunity in the control of mycobacteria in man. The genetic and immunologic heterogeneity of this syndrome makes accurate diagnosis challenging but vital as decisions about the most appropriate treatment are best taken based on an accurate molecular diagnosis.

Mendelian susceptibility to mycobacterial infection in man.

Selective susceptibility to weakly pathogenic mycobacteria, such as bacillus Calmette-Guérin (BCG) vaccine and environmental non-tuberculous mycobacteria (NTM), has long been suspected to be a Mendelian disorder but its molecular basis remained elusive. Recently, mutations in the interferon-gamma receptor ligand-binding chain (IFN gamma R1), interferon-gamma receptor signaling chain (IFN gamma R2), Signal Transducer and Activator of Transcription-1 (STAT-1), interleukin-12 p40 subunit (IL-12 p40), and interleukin-12 receptor beta 1 chain (IL-12R beta 1) genes have been identified in a number of patients with severe BCG or NTM infection. Dominant or recessive alleles causing complete or partial cellular defects have been found to define nine different inheritable disorders. Although genetically distinct, these conditions are immunologically related and highlight the essential role of interferon gamma-mediated immunity in the control of mycobacteria in man. The genetic and immunologic heterogeneity of this syndrome makes accurate diagnosis challenging but vital as decisions about the most appropriate treatment are best taken based on an accurate molecular diagnosis.

Immune deficiency presenting as mycobacterial infection.

All the discrete genetic defects identified to date that seem to specifically predispose to infection with NTM or BCG have occurred in the pathways involving the generation of or response to IFN-gamma (Fig. 3). This natural genetic survey therefore suggests that one of the most critical cytokines in the control of NTM and BCG is IFN-gamma. Unfortunately, this recognition does not give us a clear sense of the critical mechanism(s) involved and still leaves us at a phenomenological level of understanding. Therefore, even though IFN-gamma appears to be the most critical cytokine in the control of mycobacteria by the "experiments of nature" cited earlier, it is likely that other cytokines are involved in the more proximal events of killing of intracellular parasites and viral control. These cytokines or chemokines may perform better therapeutically than [figure: see text] does IFN-gamma if they are better able to evoke the critical antimycobacterial mechanism(s). Dissection of these pathways, identification of the most proximal factors, and exploitation of these findings for the treatment of mycobacterial and other intracellular infections is the critical charge for the future.

Prédisposition mendélienne aux infections mycobactériennes chez l’Homme

Selective susceptibility to poorly pathogenic mycobacteria, such as bacille Calmette-Guérin (BCG) vaccine and environmental non-tuberculous mycobacteria (NTM), bas long been suspected to be a mendelian disorder but its molecular basis has remained elusive. Recently, recessive mutations in the interferon gamma receptor ligand-binding chain (IFN gamma R1), interferon gamma receptor signalling chain (IFN gamma R2), interleukin 12 p40 subunit (IL-12 p40), and interleukin 12 receptor beta 1 chain (IL-12R beta 1) genes have been identified in a number of patients with disseminated BCG or NTM infection. Although genetically distinct, these conditions are immunologically related and highlight the essential role of interferon gamma-mediated immunity in the control of mycobacteria in man.

Mendelian susceptibility to mycobacterial infection in man

Selective susceptibility to poorly pathogenic mycobacteria, such as bacille Calmette—Guérin vaccine and environmental non-tuberculous mycobacteria, has long been suspected to be a mendelian disorder but its molecular basis has remained elusive. Recently, recessive mutations in the interferon-γ-receptor ligand-binding chain, interferon-γ-receptor signalling chain, IL-12 p40 subunit and IL-12-receptor β1 chain genes have been identified in a number of patients with disseminated mycobacterial infection. Although genetically distinct, these conditions are immunologically related and highlight the essential role of interferon-γ-mediated immunity in the control of mycobacteria in man.