Amy Myers

University of Pittsburgh, Pittsburgh, PA, United States

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Publications (13)87.82 Total impact

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    ABSTRACT: Over 30% of the world's population is infected with Mycobacterium tuberculosis (Mtb), yet only ∼5-10% will develop clinical disease. Despite considerable effort, researchers understand little about what distinguishes individuals whose infection progresses to active tuberculosis (TB) from those whose infection remains latent for decades. The variable course of disease is recapitulated in cynomolgus macaques infected with Mtb. Active disease occurs in ∼45% of infected macaques and is defined by clinical, microbiologic and immunologic signs, whereas the remaining infected animals are clinically asymptomatic. Here, we use individually marked Mtb isolates and quantitative measures of culturable and cumulative bacterial burden to show that most lung lesions are probably founded by a single bacterium and reach similar maximum burdens. Despite this observation, the fate of individual lesions varies substantially within the same host. Notably, in active disease, the host sterilizes some lesions even while others progress. Our data suggest that lesional heterogeneity arises, in part, through differential killing of bacteria after the onset of adaptive immunity. Thus, individual lesions follow diverse and overlapping trajectories, suggesting that critical responses occur at a lesional level to ultimately determine the clinical outcome of infection. Defining the local factors that dictate outcome will be useful in developing effective interventions to prevent active TB.
    Nature medicine 12/2013; · 27.14 Impact Factor
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    ABSTRACT: The effect of Mycobacterium tuberculosis inocula size on T cell priming in the lymph node and effector T cells in the lung remains controversial. In this study, we used a naive mouse model, without the transfer of transgenic T cells, in conjunction with mathematical model to test whether infection with higher aerosolized inocula would lead to increased priming of M. tuberculosis-specific T cells in the lung-draining lymph node. Our data do not support that inoculum size has a measurable influence on T cell priming in the lymph nodes but is associated with more cells overall in the lung, including T cells. To account for increased T cells in the lungs, we tested several possible mechanisms, and recruitment of T cells to the lungs was most influenced by inoculum dose. We also identified IL-10 as a possible mechanism to explain the lack of influence of inoculum dose on priming of T cells in the lymph node.
    The Journal of Immunology 04/2013; · 5.52 Impact Factor
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    ABSTRACT: Viral and bacterial infections of the lower respiratory tract are major causes of morbidity and mortality worldwide. Alveolar macrophages line the alveolar spaces and are the first cells of the immune system to respond to invading pathogens. To determine the similarities and differences between the responses of mice and macaques to invading pathogens we profiled alveolar macrophages from these species following infection with two viral (PR8 and Fuj/02 influenza A) and two bacterial (Mycobacterium tuberculosis and Francisella tularensis Schu S4) pathogens. Cells were collected at 6 time points following each infection and expression profiles were compared across and between species. Our analyses identified a core set of genes, activated in both species and across all pathogens that were predominantly part of the interferon response pathway. In addition, we identified similarities across species in the way innate immune cells respond to lethal versus non-lethal pathogens. On the other hand we also found several species and pathogen specific response patterns. These results provide new insights into mechanisms by which the innate immune system responds to, and interacts with, invading pathogens.
    PLoS ONE 01/2011; 6(7):e22401. · 3.53 Impact Factor
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    ABSTRACT: Tuberculosis (TB) is one of the earliest recorded human diseases and still one of the deadliest worldwide. Its causative agent is the bacteria Mycobacterium tuberculosis (Mtb). Cytokine-mediated macrophage activation is a necessary step in control of bacterial growth, and early immunologic events in lymph node and lung are crucial to the outcome of infection, although the factors that influence these environments and the immune response are poorly understood. Our goal is to build the next-generation two-compartmental model of the immune response to provide a gateway to more spatial and mechanistic investigations of M. tuberculosis infection in the LN and lung. Crucial immune factors emerge that affect macrophage populations and inflammation, namely TNF-dependent recruitment and apoptosis, and IL-10 levels. Surprisingly, bacterial load plays a less important role than TNF in increasing the population of infected macrophages and inflammation. Using a mathematical model, it is possible to distinguish the effects of pro-inflammatory (TNF) and anti-inflammatory (IL-10) cytokines on the spectrum of phagocyte populations (macrophages and dendritic cells) in the lung and lymph node. Our results suggest that TNF is a major mediator of recruitment of phagocytes to the lungs. In contrast, IL-10 plays a role in balancing the dominant macrophage phenotype in LN and lung.
    Journal of Theoretical Biology 08/2010; 265(4):586-98. · 2.35 Impact Factor
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    ABSTRACT: Objective. An increased risk of tuberculosis has been documented in humans treated with tumor necro-sis factor (TNF)–neutralizing agents. In murine models, impaired signaling by TNF causes exacerbation of both acute and chronic infection associated with aberrant granuloma formation and maintenance. This study was undertaken to investigate immune modula-tion in the setting of TNF neutralization in primary and latent tuberculosis in a non-human primate model. Methods. Cynomolgus macaques 4 years of age or older were infected with Mycobacterium tuberculosis and subjected to clinical, microbiologic, immunologic, and radiographic examinations. Monkeys were classified as having active or latent disease 6–8 months after infec-tion, based on clinical criteria. Monkeys used in acute infection studies were randomized to receive either adalimumab (prior to and during infection) or no treatment. Monkeys with latent infection that were randomized to receive TNF-neutralizing agent were given either an inhibitor of soluble TNF, recombinant methionyl human soluble TNF receptor I (p55-TNFRI), or adalimumab. Control monkeys with latent infection were given no treatment or saline. Data from previously studied monkeys with active or latent disease were also used for comparison. Results. Administration of TNF-neutralizing agents prior to M tuberculosis infection resulted in fulminant and disseminated disease by 8 weeks after infection. Neutralization of TNF in latently infected cynomolgus macaques caused reactivation in a majority of animals as determined by gross pathologic examina-tion and bacterial burden. A spectrum of dissemination was noted, including extrapulmonary disease. Surpris-ingly, monkeys that developed primary and reactivation tuberculosis after TNF neutralization had similar gran-uloma structure and composition to that of control monkeys with active disease. TNF neutralization was associated with increased levels of interleukin-12, de-creased levels of CCL4, increased chemokine receptor expression, and reduced mycobacteria-induced interferon-production in blood but not in the affected mediastinal lymph nodes. Finally, the first signs of reactivation often occurred in thoracic lymph nodes.: Fund for Molecular Hematology and Immunology, Moscow, Russia. Dr. Flynn has received consulting fees, speaking fees, and/or honoraria from Amgen, Sanofi Pasteur, and Celgene (less than $10,000 each).
    03/2010; 62:340-350.
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    ABSTRACT: An increased risk of tuberculosis has been documented in humans treated with tumor necrosis factor alpha (TNFalpha)-neutralizing agents. In murine models, impaired signaling by TNF causes exacerbation of both acute and chronic infection associated with aberrant granuloma formation and maintenance. This study was undertaken to investigate immune modulation in the setting of TNF neutralization in primary and latent tuberculosis in a non-human primate model. Cynomolgus macaques 4 years of age or older were infected with Mycobacterium tuberculosis and subjected to clinical, microbiologic, immunologic, and radiographic examinations. Monkeys were classified as having active or latent disease 6-8 months after infection, based on clinical criteria. Monkeys used in acute infection studies were randomized to receive either adalimumab (prior to and during infection) or no treatment. Monkeys with latent infection that were randomized to receive TNF-neutralizing agent were given either an inhibitor of soluble TNF, recombinant methionyl human soluble TNF receptor I (p55-TNFRI), or adalimumab. Control monkeys with latent infection were given no treatment or saline. Data from previously studied monkeys with active or latent disease were also used for comparison. Administration of TNF-neutralizing agents prior to M tuberculosis infection resulted in fulminant and disseminated disease by 8 weeks after infection. Neutralization of TNF in latently infected cynomolgus macaques caused reactivation in a majority of animals as determined by gross pathologic examination and bacterial burden. A spectrum of dissemination was noted, including extrapulmonary disease. Surprisingly, monkeys that developed primary and reactivation tuberculosis after TNF neutralization had similar granuloma structure and composition to that of control monkeys with active disease. TNF neutralization was associated with increased levels of interleukin-12, decreased levels of CCL4, increased chemokine receptor expression, and reduced mycobacteria-induced interferon-gamma production in blood but not in the affected mediastinal lymph nodes. Finally, the first signs of reactivation often occurred in thoracic lymph nodes. These findings have important clinical implications for determining the mechanism of TNF neutralization-related tuberculosis.
    Arthritis & Rheumatology 02/2010; 62(2):340-50. · 7.48 Impact Factor
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    ABSTRACT: We previously described that low-dose Mycobacterium tuberculosis infection in cynomolgus macaques results in a spectrum of disease similar to that of human infection: primary disease, latent infection, and reactivation tuberculosis (S. V. Capuano III, D. A. Croix, S. Pawar, A. Zinovik, A. Myers, P. L. Lin, S. Bissel, C. Fuhrman, E. Klein, and J. L. Flynn, Infect. Immun. 71:5831-5844, 2003). This is the only established model of latent infection, and it provides a unique opportunity to understand host and pathogen differences across of range of disease states. Here, we provide a more extensive and detailed characterization of the gross pathology, microscopic histopathology, and immunologic characteristics of monkeys in each clinical disease category. The data underscore the similarities between human and nonhuman primate M. tuberculosis infection. Furthermore, we describe novel methods of quantifying gross pathology and bacterial burden that distinguish between active disease and latent infection, and we extend the usefulness of this model for comparative studies. Early in infection, an abnormal chest X ray, M. tuberculosis growth by gastric aspirate, and increased mycobacterium-specific gamma interferon (IFN-gamma) in peripheral blood mononuclear cells (PBMCs) and bronchoalveolar lavage (BAL) cells were associated with the development of active disease. At necropsy, disease was quantified with respect to pathology and bacterial numbers. Microscopically, a spectrum of granuloma types are seen and differ with disease type. At necropsy, monkeys with active disease had more lung T cells and more IFN-gamma from PBMC, BAL, and mediastinal lymph nodes than monkeys with latent infection. Finally, we have observed a spectrum of disease not only in monkeys with active disease but also in those with latent infection that provides insight into human latent tuberculosis.
    Infection and immunity 08/2009; 77(10):4631-42. · 4.21 Impact Factor
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    ABSTRACT: Generating adaptive immunity after infection or immunization requires physical interactions within a lymph node (LN) T-zone between antigen-bearing dendritic cells (DCs) that arrive from peripheral tissues and rare cognate T cells entering via high endothelial venules (HEVs). This interaction results in activation of cognate T cells, expansion of that T cell lineage and their exit from the LN T-zone via efferent lymphatics (ELs). How antigen-specific T cells locate DCs within this complex environment is controversial, and both random T cell migration and chemotaxis have been proposed. We developed an agent-based computational model of a LN that captures many features of T cell and DC dynamics observed by two-photon microscopy. Our simulations matched in vivo two-photon microscopy data regarding T cell speed, short-term directional persistence of motion and cell motility. We also obtained in vivo data regarding density of T cells and DCs within a LN and matched our model environment to measurements of the distance from HEVs to ELs. We used our model to compare chemotaxis with random motion and showed that chemotaxis increased total number of T cell DC contacts, but decreased unique contacts, producing fewer activated T cells. Our results suggest that, within a LN T-zone, a random search strategy is optimal for a rare cognate T cell to find its DC match and maximize production of activated T cells.
    Journal of Theoretical Biology 03/2008; 250(4):732-51. · 2.35 Impact Factor
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    ABSTRACT: Little is known regarding the early events of infection of humans with Mycobacterium tuberculosis. The cynomolgus macaque is a useful model of tuberculosis, with strong similarities to human tuberculosis. In this study, eight cynomolgus macaques were infected bronchoscopically with low-dose M. tuberculosis; clinical, immunologic, microbiologic, and pathologic events were assessed 3 to 6 weeks postinfection. Gross pathological abnormalities were observed as early as 3 weeks, including Ghon complex formation by 5 weeks postinfection. Caseous granulomas were observed in the lung as early as 4 weeks postinfection. Only caseous granulomas were observed in the lungs at these early time points, reflecting a rigorous initial response. T-cell activation (CD29 and CD69) and chemokine receptor (CXCR3 and CCR5) expression appeared localized to different anatomic sites. Activation markers were increased on cells from airways and only at modest levels on cells in peripheral blood. The priming of mycobacterium-specific T cells, characterized by the production of gamma interferon occurred slowly, with responses seen only after 4 weeks of infection. These responses were observed from T lymphocytes in blood, airways, and hilar lymph node, with responses predominantly localized to the site of infection. From these studies, we conclude that immune responses to M. tuberculosis are relatively slow in the local and peripheral compartments and that necrosis occurs surprisingly quickly during granuloma formation.
    Infection and Immunity 08/2006; 74(7):3790-803. · 4.07 Impact Factor
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    ABSTRACT: The importance in vivo of P2X7 receptors in control of virulent Mycobacterium tuberculosis was examined in a low-dose aerosol infection mouse model. P2X7(-/-) mice controlled infection in lungs as well as wild-type mice, suggesting that the P2X7 receptor is not required for control of pulmonary M. tuberculosis infection.
    Infection and Immunity 06/2005; 73(5):3192-5. · 4.07 Impact Factor
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    ABSTRACT: CD40(-/-) mice succumbed to low-dose aerosol infection with M. tuberculosis due to deficient IL-12 production leading to impaired priming of IFN-gamma T cell responses. In contrast, CD40L(-/-) mice were resistant to M. tuberculosis. This asymmetry in outcome of infection between the two knockout strains is likely due to the existence of an alternative ligand for CD40. Both in vitro M. tuberculosis infection and recombinant M. tuberculosis Hsp70 elicited IL-12 production from WT dendritic cells. This response was absent in both CD40(-/-) dendritic cells and CD40(-/-) mice, suggesting that M. tuberculosis Hsp70 serves as an alternative ligand for CD40 in vivo.
    Immunity 01/2004; 19(6):823-35. · 19.80 Impact Factor
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    ABSTRACT: Nonhuman primates were used to develop an animal model that closely mimics human Mycobacterium tuberculosis infection. Cynomolgus macaques were infected with low doses of virulent M. tuberculosis via bronchoscopic instillation into the lung. All monkeys were successfully infected, based on tuberculin skin test conversion and peripheral immune responses to M. tuberculosis antigens. Progression of infection in the 17 monkeys studied was variable. Active-chronic infection, observed in 50 to 60% of monkeys, was characterized by clear signs of infection or disease on serial thoracic radiographs and in other tests and was typified by eventual progression to advanced disease. Approximately 40% of monkeys did not progress to disease in the 15 to 20 months of study, although they were clearly infected initially. These monkeys had clinical characteristics of latent tuberculosis in humans. Low-dose infection of cynomolgus macaques appears to represent the full spectrum of human M. tuberculosis infection and will be an excellent model for the study of pathogenesis and immunology of this infection. In addition, this model will provide an opportunity to study the latent M. tuberculosis infection observed in approximately 90% of all infected humans.
    Infection and Immunity 11/2003; 71(10):5831-44. · 4.07 Impact Factor
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    ABSTRACT: A variety of animals have been used for tuberculosis research, and each animal model has its strengths and weaknesses. We sought to develop a non-human primate model of tuberculosis to model aspects of human tuberculosis that are difficult to model in other animals, including the pathology in the lungs, various progression to disease, and immunologic correlates of infection or disease that are likely to be similar in humans. To date, we have infected 17 cynomolgus macaques (Macaca fasicularis) with a low dose (15-25CFU) of Mycobacterium tuberculosis strain Erdman. The monkeys were grouped into three categories on the basis of disease progression: rapid progression (advanced disease by 3 months post-infection), active/chronic infection (signs of disease but a slower progression), and latent infection (no signs of clinical disease). Animals were followed clinically post-infection, including blood work, physical examinations, serial bronchoalveolar lavage (BAL) and gastric aspirates for M. tuberculosis culture, chest radiographs, and tuberculin reactivity. Immunologic assays on cells from blood, BAL fluid, and tissue, have been performed, including proliferation, flow cytometry, ELIspot assays, cytotoxic T lymphocyte (CTL) assays, and ELISAs. The spectrum of disease observed in these monkeys is similar to humans, and this model may be very useful for studying pathogenesis and immunology of tuberculosis, as well as testing vaccines, diagnostic reagents, and drugs prior to use in human populations.
    Tuberculosis 02/2003; 83(1-3):116-8. · 3.03 Impact Factor

Publication Stats

584 Citations
87.82 Total Impact Points

Institutions

  • 2003–2013
    • University of Pittsburgh
      • • Department of Microbiology and Molecular Genetics
      • • Division of Pediatric Pathology at Children's Hospital of Pittsburgh of UPMC
      Pittsburgh, PA, United States
    • Riley Hospital for Children
      Indianapolis, Indiana, United States
  • 2005
    • Case Western Reserve University
      • Department of Medicine (University Hospitals Case Medical Center)
      Cleveland, OH, United States