I am a cellular immunologist specialising in infectious diseases. I trained at the University of Melbourne, before post-doctoral studies at Colorado State University, USA and the Centenary Institute where I established my own research group before taking up position at UTS in 2015. My current research projects are focused on identifying new biomarkers to aid the diagnosis of active TB disease and in dissecting the mechanisms by which macrophages control infection and regulate inflammation.
TB is still a major human pathogen despite the availability of antibiotics TB still kills around 1.5 million people a year, and growing drug resistance in TB strains is an increasing problem. New diagnostic tests to help identify TB patients and to monitor their progress during treatment to rapidly identify treatment non-responders are urgently required.
I have projects examining the response of macrophages, the natural host for TB. This work is focused on determining how TB infection modulates microRNA and microparticle expression and the biomarker potential of these molecules. I have active collaborations with colleagues in India, China and Australia collecting samples from TB patients and matched controls for analysis. I also have ongoing project looking at human macrophages and in vivo models of TB infection to dissect the mechanisms that regulate inflammation and granuloma formation.
Contribution to discipline:
I have been an active member of the Australasian Society for Immunology for over 20 years and in 2014 co-convened the ASI National meeting with 550 attendees. I am currently a member of the NSW ASI organizing committee having served as state councillor previously. I am an associate Editor for Immunology and Cell Biology and Frontiers in Microbiology and Immunology. I have served on NHMRC grant panels and regularly present my reserach at both National and International conferences .
Supervision of Students, Research Training and mentoring:
I have a strong commitment to student training and mentoring. I teach both undergraduate and postgraduates at The University of Technology Sydney, having taught at Sydney University and in the Australasian Society of Immunology teaching programs previously. I was the Post Graduate coordinator at the Centenary Institute from 2010-2014 and have mentored early career researchers at Sydney University and participates in the Science in Schools program.I have supervised numerous honours, PhD and Masters students.
Can supervise: YES
Development of new biomarkers to aid diagnosis of TB
Examination of the role of microRNA in regulation of immunity to TB infection
Inflammation and Granuloma Formation during TB infection
Role of TNF family members in regulating immunity to TB infection
I am the subject coordinator for Epidemiology and Public Health Microbiolgy. This is a great subject that explores numberous microbes of public health interest from the latest outbreaks of food poisoning to emerging pathogens and pandemics.
I am also the Program Director for the Masters of Science (Medical Biotechnology).
I teach into the Immunology subjects at both the second and third year and enjoying training new honours, PhD and Masters students.
Interested students are most welcome to contact me to discuss projects and positions within my group.
Saunders, B.M., Rudnicka, C., Filipovska, A., Davies, S., Ward, N., Hricova, J., Schlaich, M.P. & Matthews, V.B. 2018, 'Shining LIGHT on the metabolic role of the cytokine TNFSF14 and the implications on hepatic IL-6 production.', Immunology and cell biology, vol. 96, no. 1, pp. 41-53.View/Download from: Publisher's site
The cytokine Tumor Necrosis Factor Superfamily member 14, TNFSF14 (or LIGHT), is a controversial player in numerous diseases. We investigated the role of endogenously expressed TNFSF14 in diet-induced obesity in vivo. Firstly, we studied the effects of Tnfsf14 ablation on the development of obesity, glucose intolerance, insulin resistance, steatosis, tissue inflammation, and mitochondrial respiration in the liver. Secondly, we examined the role of TNFSF14 expression in hematopoietic cells on obesity and insulin sensitivity. Male Tnfsf14 knockout (KO) and wild type mice were fed chow or high fat diet (HFD) for 12 weeks and were assessed for weight gain, glucose intolerance, insulin resistance, hepatosteatosis, mitochondrial dysfunction, and cytokine expression. Wild-type mice were also reconstituted with bone marrow cells from Tnfsf14 knockout mice and were fed chow or HFD for 12 weeks. These mice were examined for weight gain and insulin resistance. HFD fed mice had elevated circulating levels of serum TNFSF14. Liver and white adipose tissue are potential sources of this elevated TNFSF14. Tnfsf14 deficient mice displayed increased obesity, glucose intolerance, insulin resistance, hepatosteatosis, and mitochondrial dysfunction compared to control mice on a HFD. Hepatic cytokine profiling pointed to a potential novel role of decreased IL-6 in the metabolic disturbances in obesogenic Tnfsf14 knockout mice. Bone marrow cells from Tnfsf14 deficient mice appeared to promote diet-induced obesity, insulin resistance and reduced FGF21 levels in white adipose tissue and liver. Our novel data suggest that Tnfsf14 ablation exacerbates parameters of the metabolic syndrome under high fat feeding conditions and provides evidence to support the development of TNFSF14 agonists as potential therapeutics in diet-induced obesity.
Hare, N.J., Lee, L.Y., Loke, I., Britton, W.J., Saunders, B.M. & Thaysen-Andersen, M. 2017, 'Mycobacterium tuberculosis Infection Manipulates the Glycosylation Machinery and the N-Glycoproteome of Human Macrophages and Their Microparticles.', Journal of Proteome Research, vol. 16, no. 1, pp. 247-263.View/Download from: UTS OPUS or Publisher's site
Tuberculosis (TB) remains a prevalent and lethal infectious disease. The glycobiology associated with Mycobacterium tuberculosis infection of frontline alveolar macrophages is still unresolved. Herein, we investigated the regulation of protein N-glycosylation in human macrophages and their secreted microparticles (MPs) used for intercellular communication upon M. tb infection. LC-MS/MS-based proteomics and glycomics were performed to monitor the regulation of glycosylation enzymes and receptors and the N-glycome in in vitro-differentiated macrophages and in isolated MPs upon M. tb infection. Infection promoted a dramatic regulation of the macrophage proteome. Most notably, significant infection-dependent down-regulation (4-26 fold) of 11 lysosomal exoglycosidases, e.g., -galactosidase, -hexosaminidases and -/-mannosidases, was observed. Relative weak infection-driven transcriptional regulation of these exoglycosidases and a stronger augmentation of the extracellular hexosaminidase activity demonstrated that the lysosome-centric changes may originate predominantly from infection-induced secretion of the lysosomal content. The macrophages showed heterogeneous N-glycan profiles and displayed significant up-regulation of complex-type glycosylation and concomitant down-regulation of paucimannosylation upon infection. Complementary intact N-glycopeptide analysis supported a subcellular-specific manipulation of the glycosylation machinery and altered glycosylation patterns of lysosomal N-glycoproteins within infected macrophages. Interestingly, the corresponding macrophage-derived MPs displayed unique N-glycome and proteome signatures supporting a preferential packaging from plasma membranes. The MPs were devoid of infection-dependent N-glycosylation signatures, but interestingly displayed increased levels of the glyco-initiating oligosaccharyltransferase complex and associated -glucosidases that correlated with increased formation, N-glycan precursor levels and N-...
Nagalingam, G., Vinuesa, C.G., Britton, W.J. & Saunders, B.M. 2017, 'Modulation of Roquin Function in Myeloid Cells Reduces Mycobacterium tuberculosis-Induced Inflammation.', Journal of immunology (Baltimore, Md. : 1950), vol. 199, no. 5, pp. 1796-1804.View/Download from: UTS OPUS or Publisher's site
Damaging inflammation is a hallmark of Mycobacterium tuberculosis infection, and understanding how this is regulated is important for the development of new therapies to limit excessive inflammation. The E3 ubiquitin ligase, Roquin, is involved in immune regulation; however, its role in immunity to M. tuberculosis is unknown. To address this, we infected mice with a point mutation in Roquin1/Rc3h1 (sanroque). Aerosol-infected sanroque mice showed enhanced control of M. tuberculosis infection associated with delayed bacterial dissemination and upregulated TNF production in the lungs after 2 wk. However, this early control of infection was not maintained, and by 8 wk postinfection sanroque mice demonstrated an increased bacterial burden and dysregulated inflammation in the lungs. As the inflammation in the lungs of the sanroque mice could have been influenced by emerging autoimmune conditions that are characteristic of the mice aging, the function of Roquin was examined in immune cell subsets in the absence of autoimmune complications. M. bovis bacillus Calmette-Guérin-primed sanroque T cells transferred into Rag1-/- mice provided equivalent protection in the spleen and liver. Interestingly, the transfer of mycobacteria-specific (P25 CD4+ TCR transgenic) wild-type spleen cells into sanroqueRag1-/- mice actually led to enhanced protection with reduced bacterial load, decreased chemokine expression, and reduced inflammation in the lungs compared with transfers into Rag1-/- mice expressing intact Roquin. These studies suggest that modulation of Roquin in myeloid cells may reduce both inflammation and bacterial growth during the chronic phase of M. tuberculosis infection.
Sierro, F, Evrard, M, Rizzetto, S, Melino, M, Mitchell, AJ, Florido, M, Beattie, L, Walters, SB, Tay, SS, Lu, B, Holz, LE, Roediger, B, Wong, YC, Warren, A, Ritchie, W, McGuffog, C, Weninger, W, Le Couteur, DG, Ginhoux, F, Britton, WJ, Heath, WR, Saunders, BM, McCaughan, GW, Luciani, F, MacDonald, KPA, Ng, LG, Bowen, DG & Bertolino, P 2017, 'A Liver Capsular Network of Monocyte-Derived Macrophages Restricts Hepatic Dissemination of Intraperitoneal Bacteria by Neutrophil Recruitment.', Immunity, vol. 47, no. 2, pp. 374-388.e6.View/Download from: UTS OPUS or Publisher's site
The liver is positioned at the interface between two routes traversed by pathogens in disseminating infection. Whereas blood-borne pathogens are efficiently cleared in hepatic sinusoids by Kupffer cells (KCs), it is unknown how the liver prevents dissemination of peritoneal pathogens accessing its outer membrane. We report here that the hepatic capsule harbors a contiguous cellular network of liver-resident macrophages phenotypically distinct from KCs. These liver capsular macrophages (LCMs) were replenished in the steady state from blood monocytes, unlike KCs that are embryonically derived and self-renewing. LCM numbers increased after weaning in a microbiota-dependent process. LCMs sensed peritoneal bacteria and promoted neutrophil recruitment to the capsule, and their specific ablation resulted in decreased neutrophil recruitment and increased intrahepatic bacterial burden. Thus, the liver contains two separate and non-overlapping niches occupied by distinct resident macrophage populations mediating immunosurveillance at these two pathogen entry points to the liver.
Donnelly, S., Huston, W.M., Johnson, M., Tiberti, N., Saunders, B., O'Brien, B., Burke, C., Labbate, M. & Combes, V. 2017, 'Targeting the master regulator mTOR: a new approach to prevent the neurological of consequences of parasitic infections?', Parasites & Vectors, vol. 10, no. 1, pp. 1-6.View/Download from: UTS OPUS or Publisher's site
A systematic analysis of 240 causes of death in 2013 revealed that parasitic diseases were responsible for more than one million deaths. The vast majority of these fatalities resulted from protozoan infections presenting with neurological sequelae. In the absence of a vaccine, development of effective therapies is essential to improving global public health. In 2015, an intriguing strategy to prevent cerebral malaria was proposed by Gordon et al. 2015 mBio, 6:e00625. Their study suggested that inhibition of the mammalian target of rapamycin prevented experimental cerebral malaria by blocking the damage to the blood brain barrier and stopping the accumulation of parasitized red blood cells and T cells in the brain. Here, we hypothesize that the same therapeutic strategy could be adopted for other protozoan infections with a brain tropism, to prevent cerebral parasitosis by limiting pathogen replication and preventing immune mediated destruction of brain tissue.
Kapetanovic, R, Bokil, NJ, Achard, ME, Ong, CL, Peters, KM, Stocks, CJ, Phan, MD, Monteleone, M, Schroder, K, Irvine, KM, Saunders, BM, Walker, MJ, Stacey, KJ, McEwan, AG, Schembri, MA & Sweet, MJ 2016, 'Salmonella employs multiple mechanisms to subvert the TLR-inducible zinc-mediated antimicrobial response of human macrophages.', FASEB journal : official publication of the Federation of American Societies for Experimental Biology, vol. 30, no. 5, pp. 1901-1912.View/Download from: UTS OPUS or Publisher's site
We aimed to characterize antimicrobial zinc trafficking within macrophages and to determine whether the professional intramacrophage pathogen Salmonella enterica serovar Typhimurium (S Typhimurium) subverts this pathway. Using both Escherichia coli and S Typhimurium, we show that TLR signaling promotes the accumulation of vesicular zinc within primary human macrophages. Vesicular zinc is delivered to E. coli to promote microbial clearance, whereas S. Typhimurium evades this response via Salmonella pathogenicity island (SPI)-1. Even in the absence of SPI-1 and the zinc exporter ZntA, S Typhimurium resists the innate immune zinc stress response, implying the existence of additional host subversion mechanisms. We also demonstrate the combinatorial antimicrobial effects of zinc and copper, a pathway that S. Typhimurium again evades. Our use of complementary tools and approaches, including confocal microscopy, direct assessment of intramacrophage bacterial zinc stress responses, specific E. coli and S Typhimurium mutants, and inductively coupled plasma mass spectroscopy, has enabled carefully controlled characterization of this novel innate immune antimicrobial pathway. In summary, our study provides new insights at the cellular level into the well-documented effects of zinc in promoting host defense against infectious disease, as well as the complex host subversion strategies employed by S Typhimurium to combat this pathway.-Kapetanovic, R., Bokil, N. J., Achard, M. E. S., Ong, C.-L. Y., Peters, K. M., Stocks, C. J., Phan, M.-D., Monteleone, M., Schroder, K., Irvine, K. M., Saunders, B. M., Walker, M. J., Stacey, K. J., McEwan, A. G., Schembri, M. A., Sweet, M. J. Salmonella employs multiple mechanisms to subvert the TLR-inducible zinc-mediated antimicrobial response of human macrophages.
Barry, S.E., Chan, B., Ellis, M., Yang, Y., Plit, M.L., Guan, G., Wang, X., Britton, W.J. & Saunders, B.M. 2015, 'Identification of miR-93 as a suitable miR for normalizing miRNA in plasma of tuberculosis patients', JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, vol. 19, no. 7, pp. 1606-1613.View/Download from: Publisher's site
Hare, N.J., Chan, B., Chan, E., Kaufman, K.L., Britton, W.J. & Saunders, B.M. 2015, 'Microparticles released from Mycobacterium tuberculosis-infected human macrophages contain increased levels of the type I interferon inducible proteins including ISG15.', Proteomics, vol. 15, no. 17, pp. 3020-3029.View/Download from: Publisher's site
Microparticles (MPs) are small membranous particles (100-1000 nm) released under normal steady-state conditions and are thought to provide a communication network between host cells. Previous studies demonstrated that Mycobacterium tuberculosis (M. tb) infection of macrophages increased the release of MPs, and these MPs induced a proinflammatory response from uninfected macrophages in vitro and in vivo following their transfer into uninfected mice. To determine how M. tb infection modulates the protein composition of the MPs, and if this contributes to their proinflammatory properties, we compared the proteomes of MPs derived from M. tb-infected (TBinf-MP) and uninfected human THP-1 monocytic cells. MP proteins were analyzed by GeLC-MS/MS with spectral counting revealing 68 proteins with statistically significant differential abundances. The 42 proteins increased in abundance in TBinf-MPs included proteins associated with immune function (7), lysosomal/endosomal maturation (4), vesicular formation (12), nucleosome proteins (4), and antigen processing (9). Prominent among these were the type I interferon inducible proteins, ISG15, IFIT1, IFIT2, and IFIT3. Exposure of uninfected THP-1 cells to TBinf-MPs induced increased gene expression of isg15, ifit1, ifit2, and ifit3 and the release of proinflammatory cytokines. These proteins may regulate the proinflammatory potential of the MPs and provide candidate biomarkers for M. tb infection.
Fox, G.J., Sy, D.N., Nhung, N.V., Yu, B., Ellis, M.K., Van Hung, N., Cuong, N.K., Thi Lien, L., Marks, G.B., Saunders, B.M. & Britton, W.J. 2014, 'Polymorphisms of SP110 are associated with both pulmonary and extra-pulmonary tuberculosis among the Vietnamese.', PLoS ONE, vol. 9, no. 7, pp. 1-9.View/Download from: UTS OPUS or Publisher's site
Tuberculosis (TB) is an infectious disease that remains a major cause of morbidity and mortality worldwide, yet the reasons why only 10% of people infected with Mycobacterium tuberculosis go on to develop clinical disease are poorly understood. Genetically determined variation in the host immune response is one factor influencing the response to M. tuberculosis. SP110 is an interferon-responsive nuclear body protein with critical roles in cell cycling, apoptosis and immunity to infection. However association studies of the gene with clinical TB in different populations have produced conflicting results.To examine the importance of the SP110 gene in immunity to TB in the Vietnamese we conducted a case-control genetic association study of 24 SP110 variants, in 663 patients with microbiologically proven TB and 566 unaffected control subjects from three tertiary hospitals in northern Vietnam.Five SNPs within SP110 were associated with all forms of TB, including four SNPs at the C terminus (rs10208770, rs10498244, rs16826860, rs11678451) under a dominant model and one SNP under a recessive model, rs7601176. Two of these SNPs were associated with pulmonary TB (rs10208770 and rs16826860) and one with extra-pulmonary TB (rs10498244).SP110 variants were associated with increased susceptibility to both pulmonary and extra-pulmonary TB in the Vietnamese. Genetic variants in SP110 may influence macrophage signaling responses and apoptosis during M. tuberculosis infection, however further research is required to establish the mechanism by which SP110 influences immunity to tuberculosis infection.
Walters, SB, Kieckbusch, J, Nagalingam, G, Swain, A, Latham, SL, Grau, GER, Britton, WJ, Combes, V & Saunders, BM 2013, 'Microparticles from mycobacteria-infected macrophages promote inflammation and cellular migration.', Journal of immunology (Baltimore, Md. : 1950), vol. 190, no. 2, pp. 669-677.View/Download from: UTS OPUS or Publisher's site
Mycobacterium tuberculosis infection is characterized by a strong inflammatory response whereby a few infected macrophages within the granuloma induce sustained cellular accumulation. The mechanisms coordinating this response are poorly characterized. We hypothesized that microparticles (MPs), which are submicron, plasma membrane-derived vesicles released by cells under both physiological and pathological conditions, are involved in this process. Aerosol infection of mice with M. tuberculosis increased CD45(+) MPs in the blood after 4 wk of infection, and in vitro infection of human and murine macrophages with mycobacteria enhanced MP release. MPs derived from mycobacteria-infected macrophages were proinflammatory, and when injected into uninfected mice they induced significant neutrophil, macrophage, and dendritic cell recruitment to the injection site. When incubated with naive macrophages, these MPs enhanced proinflammatory cytokine and chemokine release, and they aided in the disruption of the integrity of a respiratory epithelial cell monolayer, providing a mechanism for the egress of cells to the site of M. tuberculosis infection in the lung. In addition, MPs colocalized with the endocytic recycling marker Rab11a within macrophages, and this association increased when the MPs were isolated from mycobacteria-infected cells. M. tuberculosis-derived MPs also carried mycobacterial Ag and were able to activate M. tuberculosis-specific CD4(+) T cells in vivo and in vitro in a dendritic cell-dependent manner. Collectively, these data identify an unrecognized role for MPs in host response against M. tuberculosis by promoting inflammation, intercellular communication, and cell migration.
Blumenthal, A., Nagalingam, G., Huch, J.H., Walker, L., Guillemin, G.J., Smythe, G.A., Ehrt, S., Britton, W.J. & Saunders, B.M. 2012, 'M. tuberculosis induces potent activation of IDO-1, but this is not essential for the immunological control of infection.', PloS one, vol. 7, no. 5, p. e37314.View/Download from: UTS OPUS or Publisher's site
Indoleamine 2,3-dioxygenesae-1 (IDO-1) catalyses the initial, rate-limiting step in tryptophan metabolism, thereby regulating tryptophan availability and the formation of downstream metabolites, including picolinic and quinolinic acid. We found that Mycobacterium tuberculosis infection induced marked upregulation of IDO-1 expression in both human and murine macrophages in vitro and in the lungs of mice following aerosol challenge with M. tuberculosis. The absence of IDO-1 in dendritic cells enhanced the activation of mycobacteria-specific T cells in vitro. Interestingly, IDO-1-deficiency during M. tuberculosis infection in mice was not associated with altered mycobacteria-specific T cell responses in vivo. The bacterial burden of infected organs, pulmonary inflammatory responses, and survival were also comparable in M. tuberculosis-infected IDO-1 deficient and wild type animals. Tryptophan is metabolised into either picolinic acid or quinolinic acid, but only picolinic acid inhibited the growth of M. tuberculosis in vitro. By contrast macrophages infected with pathogenic mycobacteria, produced quinolinic, rather than picolinic acid, which did not reduce M. tuberculosis growth in vitro. Therefore, although M. tuberculosis induces robust expression of IDO-1 and activation of tryptophan metabolism, IDO-1-deficiency fails to impact on the immune control and the outcome of the infection in the mouse model of tuberculosis.
Beham, AW, Puellmann, K, Laird, R, Fuchs, T, Streich, R, Breysach, C, Raddatz, D, Oniga, S, Peccerella, T, Findeisen, P, Kzhyshkowska, J, Gratchev, A, Schweyer, S, Saunders, B, Wessels, JT, Möbius, W, Keane, J, Becker, H, Ganser, A, Neumaier, M & Kaminski, WE 2011, 'A TNF-regulated recombinatorial macrophage immune receptor implicated in granuloma formation in tuberculosis.', PLoS pathogens, vol. 7, no. 11, p. e1002375.View/Download from: UTS OPUS or Publisher's site
Macrophages play a central role in host defense against mycobacterial infection and anti- TNF therapy is associated with granuloma disorganization and reactivation of tuberculosis in humans. Here, we provide evidence for the presence of a T cell receptor (TCR) based recombinatorial immune receptor in subpopulations of human and mouse monocytes and macrophages. In vitro, we find that the macrophage-TCR induces the release of CCL2 and modulates phagocytosis. TNF blockade suppresses macrophage-TCR expression. Infection of macrophages from healthy individuals with mycobacteria triggers formation of clusters that express restricted TCR V repertoires. In vivo, TCR bearing macrophages abundantly accumulate at the inner host-pathogen contact zone of caseous granulomas from patients with lung tuberculosis. In chimeric mouse models, deletion of the variable macrophage-TCR or TNF is associated with structurally compromised granulomas of pulmonary tuberculosis even in the presence of intact T cells. These results uncover a TNF-regulated recombinatorial immune receptor in monocytes/macrophages and demonstrate its implication in granuloma formation in tuberculosis.
Bokil, NJ, Totsika, M, Carey, AJ, Stacey, KJ, Hancock, V, Saunders, BM, Ravasi, T, Ulett, GC, Schembri, MA & Sweet, MJ 2011, 'Intramacrophage survival of uropathogenic Escherichia coli: differences between diverse clinical isolates and between mouse and human macrophages.', Immunobiology, vol. 216, no. 11, pp. 1164-1171.View/Download from: UTS OPUS or Publisher's site
Uropathogenic E. coli (UPEC) are the primary cause of urinary tract infections. Recent studies have demonstrated that UPEC can invade and replicate within epithelial cells, suggesting that this bacterial pathogen may occupy an intracellular niche within the host. Given that many intracellular pathogens target macrophages, we assessed the interactions between UPEC and macrophages. Colonization of the mouse bladder by UPEC strain CFT073 resulted in increased expression of myeloid-restricted genes, consistent with the recruitment of inflammatory macrophages to the site of infection. In in vitro assays, CFT073 was able to survive within primary mouse bone marrow-derived macrophages (BMM) up to 24h post-infection. Three additional well-characterized clinical UPEC isolates associated with distinct UTI symptomatologies displayed variable long-term survival within BMM. UPEC strains UTI89 and VR50, originally isolated from patients with cystitis and asymptomatic bacteriuria respectively, showed elevated bacterial loads in BMM at 24h post-infection as compared to CFT073 and the asymptomatic bacteriuria strain 83972. These differences did not correlate with differential effects on macrophage survival or initial uptake of bacteria. E. coli UTI89 localized to a Lamp1(+) vesicular compartment within BMM. In contrast to survival within mouse BMM, intracellular bacterial loads of VR50 were low in both human monocyte-derived macrophages (HMDM) and in human T24 bladder epithelial cells. Collectively, these data suggest that some UPEC isolates may subvert macrophage anti-microbial pathways, and that host species differences may impact on intracellular UPEC survival.
Gu, BJ, Saunders, BM, Petrou, S & Wiley, JS 2011, 'P2X(7) is a scavenger receptor for apoptotic cells in the absence of its ligand, extracellular ATP.', Journal of immunology (Baltimore, Md. : 1950), vol. 187, no. 5, pp. 2365-2375.View/Download from: UTS OPUS or Publisher's site
Phagocytosis of apoptotic cells is essential during development and tissue remodeling. Our previous study has shown that the P2X(7) receptor regulates phagocytosis of nonopsonized particles and bacteria. In this study, we demonstrate that P2X(7) also mediates phagocytosis of apoptotic lymphocytes and neuronal cells by human monocyte-derived macrophages under serum-free conditions. ATP inhibited this process to a similar extent as observed with cytochalasin D. P2X(7)-transfected HEK-293 cells acquired the ability to phagocytose apoptotic lymphocytes. Injection of apoptotic thymocytes into the peritoneal cavity of wild-type mice resulted in their phagocytosis by macrophages, but injection of ATP prior to thymocytes markedly decreased this uptake. In contrast, ATP failed to inhibit phagocytosis of apoptotic thymocytes in vivo by P2X(7)-deficient peritoneal macrophages. The surface expression of P2X(7) on phagocytes increased significantly during phagocytosis of either beads or apoptotic cells. A peptide screen library containing 24 biotin-conjugated peptides mimicking the extracellular domain of P2X(7) was used to evaluate the binding profile to beads, bacteria, and apoptotic cells. One peptide showed binding to all particles and cell membrane lipids. Three other cysteine-containing peptides uniquely bound the surface of apoptotic cells but not viable cells, whereas substitution of alanine for cysteine abolished peptide binding. Several thiol-reactive compounds including N-acetyl-L-cysteine abolished phagocytosis of apoptotic SH-SY5Y cells by macrophages. These data suggest that the P2X(7) receptor in its unactivated state acts like a scavenger receptor, and its extracellular disulphide bonds play an important role in direct recognition and engulfment of apoptotic cells.
Miller, C.M., Boulter, N.R., Fuller, S.J., Zakrzewski, A.M., Lees, M.P., Saunders, B.M., Wiley, J.S. & Smith, N.C. 2011, 'The role of the P2X receptor in infectious diseases.', PLoS pathogens, vol. 7, no. 11, p. e1002212.View/Download from: UTS OPUS or Publisher's site
ATP is an extracellular signal for the immune system, particularly during an inflammatory response. It is sensed by the P2X receptor, the expression of which is upregulated by pro-inflammatory cytokines. Activation of the P2X receptor opens a cation-specific channel that alters the ionic environment of the cell, activating several pathways, including (i) the inflammasome, leading to production of IL-1 and IL-18; (ii) the stress-activated protein kinase pathway, resulting in apoptosis; (iii) the mitogen-activated protein kinase pathway, leading to generation of reactive oxygen and nitrogen intermediates; and (iv) phospholipase D, stimulating phagosome-lysosome fusion. The P2X receptor can initiate host mechanisms to remove pathogens, most particularly those that parasitise macrophages. At the same time, the P2X receptor may be subverted by pathogens to modulate host responses. Moreover, recent genetic studies have demonstrated significant associations between susceptibility or resistance to parasites and bacteria, and loss-of-function or gain-of-function polymorphisms in the P2X receptor, underscoring its importance in infectious disease.
Stanley, AC, de Labastida Rivera, F, Haque, A, Sheel, M, Zhou, Y, Amante, FH, Bunn, PT, Randall, LM, Pfeffer, K, Scheu, S, Hickey, MJ, Saunders, BM, Ware, C, Hill, GR, Tamada, K, Kaye, PM & Engwerda, CR 2011, 'Critical roles for LIGHT and its receptors in generating T cell-mediated immunity during Leishmania donovani infection.', PLoS pathogens, vol. 7, no. 10, p. e1002279.View/Download from: UTS OPUS or Publisher's site
LIGHT (TNFSF14) is a member of the TNF superfamily involved in inflammation and defence against infection. LIGHT signals via two cell-bound receptors; herpes virus entry mediator (HVEM) and lymphotoxin-beta receptor (LTR). We found that LIGHT is critical for control of hepatic parasite growth in mice with visceral leishmaniasis (VL) caused by infection with the protozoan parasite Leishmania donovani. LIGHT-HVEM signalling is essential for early dendritic cell IL-12/IL-23p40 production, and the generation of IFN- and TNF-producing T cells that control hepatic infection. However, we also discovered that LIGHT-LTR interactions suppress anti-parasitic immunity in the liver in the first 7 days of infection by mechanisms that restrict both CD4(+) T cell function and TNF-dependent microbicidal mechanisms. Thus, we have identified distinct roles for LIGHT in infection, and show that manipulation of interactions between LIGHT and its receptors may be used for therapeutic advantage.
Gu, BJ, Saunders, BM, Jursik, C & Wiley, JS 2010, 'The P2X7-nonmuscle myosin membrane complex regulates phagocytosis of nonopsonized particles and bacteria by a pathway attenuated by extracellular ATP.', Blood, vol. 115, no. 8, pp. 1621-1631.View/Download from: Publisher's site
Phagocytosis of nonopsonized bacteria is central to innate immunity, but its regulation is less defined. We show that overexpression of the P2X(7) receptor greatly augments the phagocytosis of nonopsonized beads and heat-killed bacteria by transfected HEK-293 cells, whereas blocking P2X(7) expression by siRNA significantly reduces the phagocytic ability of human monocytic cells. An intact P2X(7)-nonmuscle myosin complex is required for phagocytosis of nonopsonized beads because activation of P2X(7) receptors by adenosine triphosphate (ATP), which dissociates myosin IIA from the P2X(7) complex, inhibits this phagocytic pathway. Fresh human monocytes rapidly phagocytosed live and heat-killed Staphylococcus aureus and Escherichia coli in the absence of serum, but the uptake was reduced by prior incubation with ATP, or P2X(7) monoclonal antibody, or recombinant P2X(7) extracellular domain. Injection of beads or bacteria into the peritoneal cavity of mice resulted in their brisk phagocytosis by macrophages, but injection of ATP before particles markedly decreased this uptake. These data demonstrate a novel pathway of phagocytosis of nonopsonized particles and bacteria, which operate in vivo and require an intact P2X(7)-nonmuscle myosin IIA membrane complex. The inhibitory effect of ATP on particle uptake by the macrophage is regulated by the P2X(7) receptor and defines this phagocytic pathway.
Kuang, Z., Lewis, R.S., Curtis, J.M., Zhan, Y., Saunders, B.M., Babon, J.J., Kolesnik, T.B., Low, A., Masters, S.L., Willson, T.A., Kedzierski, L., Yao, S., Handman, E., Norton, R.S. & Nicholson, S.E. 2010, 'The SPRY domain-containing SOCS box protein SPSB2 targets iNOS for proteasomal degradation.', The Journal of Cell Biology, vol. 190, no. 1, pp. 129-141.View/Download from: Publisher's site
Inducible nitric oxide (NO) synthase (iNOS; NOS2) produces NO and related reactive nitrogen species, which are critical effectors of the innate host response and are required for the intracellular killing of pathogens such as Mycobacterium tuberculosis and Leishmania major. We have identified SPRY domain-containing SOCS (suppressor of cytokine signaling) box protein 2 (SPSB2) as a novel negative regulator that recruits an E3 ubiquitin ligase complex to polyubiquitinate iNOS, resulting in its proteasomal degradation. SPSB2 interacts with the N-terminal region of iNOS via a binding interface on SPSB2 that has been mapped by nuclear magnetic resonance spectroscopy and mutational analyses. SPSB2-deficient macrophages showed prolonged iNOS expression, resulting in a corresponding increase in NO production and enhanced killing of L. major parasites. These results lay the foundation for the development of small molecule inhibitors that could disrupt the SPSB-iNOS interaction and thus prolong the intracellular lifetime of iNOS, which may be beneficial in chronic and persistent infections.
Musicki, K, Briscoe, H, Britton, WJ & Saunders, BM 2010, 'LIGHT contributes to early but not late control of Mycobacterium tuberculosis infection.', International immunology, vol. 22, no. 5, pp. 353-358.View/Download from: Publisher's site
The TNF superfamily member, LIGHT, contributes to optimal T-cell activation in vitro through co-stimulation of dendritic cell cytokine production; however, its role in T-cell-mediated control of intracellular bacterial infections is unknown. Protective immunity against Listeria monocytogenes and Mycobacterium tuberculosis infection requires both antigen-specific CD4(+) and CD8(+) T cells. Using LIGHT-deficient mice we determined that LIGHT was necessary for optimal re-stimulation of anti-listerial CD8(+) T cells in vitro. By contrast, LIGHT(-/-) mice infected with L. monocytogenes generated equivalent T-cell responses and controlled the infection as effectively as normal C57BL/6 mice. Following M. tuberculosis infection, LIGHT(-/-) mice showed a significant increase in bacterial replication in the lungs at 4 weeks, but by 6 weeks had controlled the infection. Analysis of T-cell responses in vivo revealed that LIGHT was dispensable for the activation of primary T-cell responses and the production of IL-12 and IFN-gamma. In addition, LIGHT was not required for the induction of memory T-cell responses to anti-mycobacterial DNA or BCG vaccines and for subsequent protection against tuberculosis challenge. Therefore, LIGHT contributes to the optimal co-stimulation of anti-listerial CD8(+) T-cell responses in vitro and to the early control of M. tuberculosis infection; however, other mechanisms compensate for LIGHT deficiency in the control of these pathogens in vivo.
Wozniak, TM, Saunders, BM, Ryan, AA & Britton, WJ 2010, 'Mycobacterium bovis BCG-specific Th17 cells confer partial protection against Mycobacterium tuberculosis infection in the absence of gamma interferon.', Infection and immunity, vol. 78, no. 10, pp. 4187-4194.View/Download from: Publisher's site
Protective immunity against tuberculosis (TB) requires the integrated response of a network of lymphocytes. Both gamma interferon (IFN-)- and interleukin 17 (IL-17)-secreting CD4(+) T cells have been identified in subjects with latent TB infection and during experimental Mycobacterium tuberculosis infection, but the contribution of Th17 cells to protective immunity is unclear. To examine their protective effects in vivo, we transferred mycobacterium-specific IL-17- and IFN--secreting CD4(+) T cells isolated from M. tuberculosis BCG-immunized IL-12p40(-/-) and IFN-(-/-) or wild-type mice, respectively, into M. tuberculosis-infected IL-12p40(-/-) or RAG(-/-) mice. In the absence of IL-12 and IL-23, neither IL-17-secreting (Th17) nor IFN--secreting (Th1) BCG-specific T cells expanded or provided protection against M. tuberculosis. In RAG(-/-) recipients with an intact IL-12/IL-23 axis, both Th17 and Th1 cells were activated and induced significant protection against M. tuberculosis. The reduction in the bacterial load following transfer of IFN-(-/-) Th17 cells was associated with significant prolongation of survival compared to recipients of nave IFN-(-/-) T cells. This effect was at the cost of an increased inflammatory infiltrate characterized by an excess of neutrophils. Therefore, Th17 cells can provide IFN--independent protection against M. tuberculosis, and this effect may contribute to the early control of M. tuberculosis infection.
Hagge, D.A., Saunders, B.M., Ebenezer, G.J., Ray, N.A., Marks, V.T., Britton, W.J., Krahenbuhl, J.L. & Adams, L.B. 2009, 'Lymphotoxin-alpha and TNF have essential but independent roles in the evolution of the granulomatous response in experimental leprosy.', The American journal of pathology, vol. 174, no. 4, pp. 1379-1389.View/Download from: Publisher's site
Recent studies identified an association between genetic variants in the lymphotoxin-alpha (LTalpha) gene and leprosy. To study the influence of LTalpha on the control of experimental leprosy, both low- and high-dose Mycobacterium leprae foot pad (FP) infections were evaluated in LTalpha-deficient chimeric (cLTalpha(-/-)) and control chimeric (cB6) mice. Cellular responses to low-dose infection in cLTalpha(-/-) mice were dramatically different, with reduced accumulation of CD4(+) and CD8(+) lymphocytes and macrophages and failure to form granulomas. Growth of M. leprae was contained for 6 months, but augmented late in infection. In contrast, tumor necrosis factor knockout and tumor necrosis factor receptor 1 knockout FPs exhibited extensive inflammatory infiltration with an increase in M. leprae growth throughout infection. Following high-dose infection, cB6 FP induration peaked at 4 weeks and was maintained for 12 weeks. Induration was not sustained in cLTalpha(-/-) FPs that contained few lymphocytes and no granulomas. There was a reduction in the expression levels of inflammatory cytokines, chemokines, and chemokine receptors, including nitric oxide synthase 2, vascular cell adhesion molecule, and intercellular cell adhesion molecule. Furthermore, cLTalpha(-/-) popliteal lymph nodes contained a higher proportion of nave CD44(lo)CD62L(hi) T cells than cB6 mice, suggestive of reduced T cell activation. Therefore, both LTalpha and tumor necrosis factor are essential for the regulation of the granuloma, but they have distinctive roles in the recruitment of lymphocytes and maintenance of the granulomatous response during chronic M. leprae infection.
Miu, J, Mitchell, AJ, Müller, M, Carter, SL, Manders, PM, McQuillan, JA, Saunders, BM, Ball, HJ, Lu, B, Campbell, IL & Hunt, NH 2008, 'Chemokine gene expression during fatal murine cerebral malaria and protection due to CXCR3 deficiency.', Journal of immunology (Baltimore, Md. : 1950), vol. 180, no. 2, pp. 1217-1230.View/Download from: Publisher's site
Cerebral malaria (CM) can be a fatal manifestation of Plasmodium falciparum infection. Using murine models of malaria, we found much greater up-regulation of a number of chemokine mRNAs, including those for CXCR3 and its ligands, in the brain during fatal murine CM (FMCM) than in a model of non-CM. Expression of CXCL9 and CXCL10 RNA was localized predominantly to the cerebral microvessels and in adjacent glial cells, while expression of CCL5 was restricted mainly to infiltrating lymphocytes. The majority of mice deficient in CXCR3 were found to be protected from FMCM, and this protection was associated with a reduction in the number of CD8+ T cells in brain vessels as well as reduced expression of perforin and FasL mRNA. Adoptive transfer of CD8+ cells from C57BL/6 mice with FMCM abrogated this protection in CXCR3-/- mice. Moreover, there were decreased mRNA levels for the proinflammatory cytokines IFN-gamma and lymphotoxin-alpha in the brains of mice protected from FMCM. These data suggest a role for CXCR3 in the pathogenesis of FMCM through the recruitment and activation of pathogenic CD8+ T cells.
Britton, W.J., Fernando, S.L., Saunders, B.M., Sluyter, R. & Wiley, J.S. 2007, 'The genetic control of susceptibility to Mycobacterium tuberculosis.', Novartis Foundation symposium, vol. 281, pp. 79-209.
Mycobacterium tuberculosis is one of the most successful human pathogens, surviv ing in latent foci of infection in one third of humanity, yet causing lung necrosis in sufficient individuals to ensure its transmission. Each stage of the host response to M. tuberculosis is under genetic control, including the initial encounter with mycobacteria by macrophages, epithelial cells and dendritic cells in the lung, induction of the inductive T cell response, and killing by activated macrophages within granulomas. Although environmental factors are important determinants of progression to disease, there is a genetic component underlying susceptibility to tuberculosis (TB), the basis of which may vary in different populations. Recent studies using a variety of methods have defined a number of susceptibility alleles for the development of active TB. Many of these influence macrophage responses to mycobacteria. We have studied the influence of loss of function polymorphisms in the human P2X7 gene on the capacity of macrophages to kill M. tuberculosis. Activation of the P2X7 receptor, an ATP-gated Ca2+ channel, leads to the formation of pores, the activation of phospholipase D, and the induction of apoptosis with death of the infecting mycobacteria. Macrophages from subjects who are heterozygote, homozygote or compound heterozygote for these polymorphisms fail to undergo apoptosis and show partial or complete inhibition of mycobacterial killing. One of these non-functioning polymorphisms was significantly associated with increased susceptibility to TB disease, particularly extrapulmonary disease, in two unrelated cohorts of TB patients. Insights into the genetic regulation of susceptibility to human TB may identify novel methods for controlling latent M. tuberculosis and reducing the burden of tuberculosis.
Fernando, S.L., Saunders, B.M., Sluyter, R., Skarratt, K.K., Goldberg, H., Marks, G.B., Wiley, J.S. & Britton, W.J. 2007, 'A polymorphism in the P2X7 gene increases susceptibility to extrapulmonary tuberculosis.', American journal of respiratory and critical care medicine, vol. 175, no. 4, pp. 360-366.View/Download from: Publisher's site
RATIONALE: Genetic variation influences susceptibility to clinical tuberculosis (TB). Activation of the P2X(7) receptor on human macrophages induces killing of mycobacteria. We have identified polymorphisms in the P2X(7) gene that markedly reduce this killing. OBJECTIVE: To determine if polymorphisms in P2X7 are associated with increased risk of TB, the prevalence of four polymorphisms was assessed in individuals from Southeast Asia, where the majority of patients with TB in our study originate. The association of these polymorphisms with clinical TB was subsequently investigated in two separate case-control cohorts and the function of P2X(7) was assessed in subjects from one cohort. METHODS: Genotyping of P2X7 polymorphisms was performed from subjects in a nested case-control study of a longitudinal refugee cohort and a separate case-control study. The functional capacity of P2X(7) was investigated by measuring ATP-mediated mycobacterial killing and apoptosis. RESULTS: Only the 1513A-C polymorphism was present in Southeast Asians and the allele was associated with reduced killing of Mycobacterium tuberculosis. The 1513C allele was strongly associated with extrapulmonary, but not pulmonary, TB in the first (odds ratio, 3.8; 95% confidence interval, 1.6-9.0) and second cohorts (odds ratio, 3.7; 95% confidence interval, 1.7-8.0). ATP-mediated killing of mycobacteria was ablated in macrophages from subjects homozygous for the 1513C allele and significantly impaired in macrophages from heterozygous subjects. There was strong correlation between the degree of mycobacterial killing and ATP-induced apoptosis. CONCLUSIONS: The 1513C allele increases susceptibility to extrapulmonary TB, and this defect is associated with the reduction in the capacity of macrophages to kill M. tuberculosis.
During tuberculosis (TB) infection, the granuloma provides the microenvironment in which antigen-specific T cells colocate with and activate infected macrophages to inhibit the growth of Mycobacterium tuberculosis. Although the granuloma is the site for mycobacterial killing, virulent mycobacteria have developed a variety of mechanisms to resist this macrophage-mediated killing. These surviving mycobacteria become dormant, however, if host cellular immunity or the signals maintaining granuloma structure wane, or if mycobacteria resume replication, leading to reactivation of TB. This balance of life and death applies not only to the mycobacterium but also to the host macrophages that may undergo apoptosis or necrosis, leading to the characteristic caseous necrosis within the granuloma, and the potential spread of TB infection. The immunological factors controlling the development and maintenance of the granuloma will be reviewed.
Musicki, K., Briscoe, H., Tran, S., Britton, W.J. & Saunders, B.M. 2006, 'Differential requirements for soluble and transmembrane tumor necrosis factor in the immunological control of primary and secondary Listeria monocytogenes infection.', Infection and immunity, vol. 74, no. 6, pp. 3180-3189.View/Download from: Publisher's site
The relative contributions of transmembrane tumor necrosis factor (memTNF) and soluble tumor necrosis factor (solTNF) in innate and adaptive immunity are poorly defined. We examined the capacities of wild-type (WT) mice, TNF-/- mice, and memTNF mice, which express only transmembrane TNF, to control primary and secondary Listeria monocytogenes infections. Soluble TNF was not required for induction or maintenance of protective immunity against a low-dose (200-CFU) Listeria infection. In contrast to TNF-/- mice, both WT and memTNF mice cleared the bacilli within 10 days and were fully protected against rechallenge with a lethal infective dose. Furthermore, T cells transferred from immune mice, but not from nave, WT, and memTNF mice, protected TNF-/- recipients against an otherwise lethal infection. By contrast, infection with a higher dose of Listeria (2,000 CFU) clearly demonstrated that solTNF is required to coordinate an optimal protective inflammatory response. memTNF mice were more susceptible to a high-dose infection, and they exhibited delayed bacterial clearance, increased inflammation, and necrosis in the liver that resulted in 55% mortality. The dysregulated inflammation was accompanied by prolonged elevated expression of mRNAs for several chemokines as well as the macrophage effector molecules inducible nitric oxide synthase and LRG-47 in the livers of memTNF mice but not in the livers of WT mice. These data demonstrated that memTNF is sufficient for establishing protective immunity against a primary low-dose Listeria infection but that solTNF is required for optimal control of cellular inflammation and resistance to a primary high-dose infection. By contrast, memTNF alone is sufficient for resolution of a secondary, high-dose infection and for the transfer of protective immunity with memory T cells.
Shemon, A.N., Sluyter, R., Fernando, S.L., Clarke, A.L., Dao-Ung, L.-.P., Skarratt, K.K., Saunders, B.M., Tan, K.S., Gu, B.J., Fuller, S.J., Britton, W.J., Petrou, S. & Wiley, J.S. 2006, 'A Thr357 to Ser polymorphism in homozygous and compound heterozygous subjects causes absent or reduced P2X7 function and impairs ATP-induced mycobacterial killing by macrophages.', The Journal of biological chemistry, vol. 281, no. 4, pp. 2079-2086.View/Download from: Publisher's site
The P2X(7) receptor is a ligand-gated cation channel that is highly expressed on mononuclear leukocytes and that mediates ATP-induced apoptosis and killing of intracellular pathogens. There is a wide variation in P2X(7) receptor function between subjects, explained in part by four loss-of-function polymorphisms (R307Q, E496A, I568N, and a 5'-intronic splice site polymorphism), as well as rare mutations. In this study, we report the allele frequencies of 11 non-synonymous P2X(7) polymorphisms and describe a fifth loss-of-function polymorphism in the gene (1096C --> G), which changes Thr(357) to Ser (T357S) with an allele frequency of 0.08 in the Caucasian population. P2X(7) function was measured by ATP-induced ethidium(+) influx into peripheral blood lymphocytes and monocytes and, when compared with wild-type subjects, was reduced to 10-65% in heterozygotes, 1-18% in homozygotes, and 0-10% in compound heterozygotes carrying T357S and a second loss-of-function polymorphism. Overexpression of the T357S mutant P2X(7) in either HEK-293 cells or Xenopus oocytes gave P2X(7) function of approximately 50% that of wild-type constructs. Differentiation of monocytes to macrophages, which also up-regulates P2X(7), restored P2X(7) function to near normal in cells heterozygous for T357S and to a value 50-65% of wild-type in cells homozygous for T357S or compound heterozygous for T357S/E496A. However, macrophages from subjects that are compound heterozygous for either T357S/R307Q or T357S/stop codon had near-to-absent P2X(7) function. These functional deficits induced by T357S were paralleled by impaired ATP-induced apoptosis and mycobacteria killing in macrophages from these subjects. Lymphocytes, monocytes, and macrophages from subjects homozygous for T357S or compound heterozygous for T357S and a second loss-of-function allele have reduced or absent P2X(7) receptor function.
Fernando, S.L., Saunders, B.M., Sluyter, R., Skarratt, K.K., Wiley, J.S. & Britton, W.J. 2005, 'Gene dosage determines the negative effects of polymorphic alleles of the P2X7 receptor on adenosine triphosphate-mediated killing of mycobacteria by human macrophages.', The Journal of infectious diseases, vol. 192, no. 1, pp. 149-155.View/Download from: Publisher's site
BACKGROUND: Stimulation of the P2X7 purinergic receptor (P2X7) in bacille Calmette-Guerin (BCG)-infected human macrophages with extracellular adenosine triphosphate (ATP) leads to pore formation and killing of mycobacteria. We examined the effect of polymorphisms in the P2X7 gene (P2X7) on the capacity of macrophages to kill mycobacteria. METHODS: Polymorphisms and mutations in P2X7 were identified by both DNA sequence analysis and determination of uptake of ethidium by time-resolved flow cytometry. Macrophages from affected subjects were infected with Mycobacterium bovis BCG. Apoptosis was determined by use of Annexin V staining, and BCG growth was determined by use of quantitative mycobacterial cultures. RESULTS: Three new mutations were identified. Macrophages from subjects heterozygous for a polymorphism in P2X7 had a 50% reduction in uptake of ethidium and a 75% reduction in the number of apoptotic cells, compared with macrophages from wild-type (wt) subjects, after stimulation with interferon (IFN)- gamma and ATP. Furthermore, after stimulation with IFN- gamma and ATP, there was a reduction in BCG growth of up to approximately 0.5 log10 in macrophages from single-heterozygous subjects, compared with a reduction of 1.0 log10 in macrophages from wt subjects. Interestingly, BCG-infected macrophages from compound-heterozygous subjects, for different combinations of polymorphisms in P2X7, had no uptake of ethidium, failed to undergo apoptosis, and were unable to kill mycobacteria after stimulation with IFN- gamma and ATP. CONCLUSIONS: Various polymorphisms in P2X7 abrogate IFN- gamma /ATP-induced killing of mycobacteria by human macrophages and, thus, may contribute to variability in susceptibility to mycobacterial infections.
Roach, D.R., Briscoe, H., Saunders, B.M. & Britton, W.J. 2005, 'Independent protective effects for tumor necrosis factor and lymphotoxin alpha in the host response to Listeria monocytogenes infection.', Infection and immunity, vol. 73, no. 8, pp. 4787-4792.View/Download from: Publisher's site
Although the essential role of tumor necrosis factor (TNF) in resistance to Listeria monocytogenes infection is well established, the roles of the related cytokines lymphotoxin alpha (LTalpha) and lymphotoxin beta (LTbeta) are unknown. Using C57BL/6 mice in which the genes for these cytokines were disrupted, we examined the contributions of TNF, LTalpha, and LTbeta in the host response to Listeria. To overcome the lack of peripheral lymph nodes in LTalpha(-/-) and LTbeta(-/-) mice, bone marrow chimeras were constructed. TNF(-/-) and LTalpha(-/-) chimeras that lacked both secreted LTalpha(3) and membrane-bound LTalpha(1)beta(2) and LTalpha(2)beta(1) were highly susceptible and succumbed 4.5 and 6 days, respectively, after a low-dose infection (200 CFU). LTbeta(-/-) chimeras, which lacked only membrane-bound LT, controlled the infection in a manner comparable to wild-type (WT) chimeras. The Listeria-specific proliferative and gamma interferon T-cell responses were equivalent in all five groups of infected mice (LTalpha(-/-) and LTbeta(-/-) chimeras, WT chimeras, and TNF(-/-) and WT mice). TNF(-/-) mice and LTalpha(-/-) chimeras, however, failed to generate the discrete foci of lymphocytes and macrophages that are essential for bacterial elimination. Rather, aberrant necrotic lesions comprised predominantly of neutrophils with relatively few lymphocytes and macrophages were observed in the livers and spleens of TNF(-/-) and LTalpha(-/-) chimeras. Therefore, in addition to TNF, soluble LTalpha(3) plays a separate essential role in control of listerial infection through control of leukocyte accumulation and organization in infected organs.
Saunders, BM, Tran, S, Ruuls, S, Sedgwick, JD, Briscoe, H & Britton, WJ 2005, 'Transmembrane TNF is sufficient to initiate cell migration and granuloma formation and provide acute, but not long-term, control of Mycobacterium tuberculosis infection.', Journal of immunology (Baltimore, Md. : 1950), vol. 174, no. 8, pp. 4852-4859.View/Download from: Publisher's site
TNF is critical for immunity against Mycobacterium tuberculosis infection; however, the relative contributions of the soluble and transmembrane forms of TNF in this immunity are unknown. Using memTNF mice, which express only the transmembrane form of TNF, we have addressed this question. Wild-type (WT), TNF-/-, and transmembrane TNF (memTNF) mice were infected with M. tuberculosis by aerosol. TNF-/- mice developed overwhelming infection with extensive pulmonary necrosis and died after only 33 days. memTNF mice, like WT mice, contained bacterial growth for over 16 wk, developed an Ag-specific T cell response, and initially displayed compact granulomas, comprised of both lymphocytes and macrophages. Expression of mRNA for the chemokines CXCL10, CCL3, CCL5, and CCL7 was comparable in both WT and memTNF mice. As the infection progressed, however, the pulmonary lesions in memTNF mice became larger and more diffuse, with increased neutrophil accumulation and necrosis. This was accompanied by increased influx of activated memory T cells into the lungs of memTNF mice. Eventually, these mice succumbed to infection with a mean time to death of 170 days. The expression of memTNF on T cells is functionally important because the transfer of T cells from memTNF, but not TNF-/- mice, into either RAG-/- or TNF-/- mice conferred the same survival advantage on the M. tuberculosis-infected recipient mice, as the transfer of WT T cells. Therefore, memTNF, in the absence of soluble TNF, is sufficient to control acute, but not chronic, M. tuberculosis infection, in part through its expression on T cells.
Pinto, R., Saunders, B.M., Camacho, L.R., Britton, W.J., Gicquel, B. & Triccas, J.A. 2004, 'Mycobacterium tuberculosis defective in phthiocerol dimycocerosate translocation provides greater protective immunity against tuberculosis than the existing bacille Calmette-Guérin vaccine.', The Journal of infectious diseases, vol. 189, no. 1, pp. 105-112.View/Download from: Publisher's site
We demonstrate that Mycobacterium tuberculosis that is unable to export the complex lipid phthiocerol dimycocerosate has a decreased capacity to replicate in mice and affords sustained protective immunity against M. tuberculosis infection Protection was significantly better than that provided by the existing vaccine, Mycobacterium bovis bacille Calmette-Guérin (BCG), and this improved protective efficacy was maintained for at least 24 weeks after vaccination. Protection afforded by this attenuated strain coincided with a number of factors that were not associated with BCG vaccination: long-term persistence of the strain within the host, sustained and potent induction of antimycobacterial interferon-gamma-secreting cells equal to that induced by virulent M. tuberculosis, and elicitation of T cells recognizing dominant M. tuberculosis antigens absent from BCG. These results suggest that the BCG vaccine may be too attenuated to afford effective protective immunity against tuberculosis, and vaccine strains that can provide sustained delivery of mycobacterial antigens are promising antituberculosis vaccine candidates.
Saunders, B.M., Briscoe, H. & Britton, W.J. 2004, 'T cell-derived tumour necrosis factor is essential, but not sufficient, for protection against Mycobacterium tuberculosis infection.', Clinical and experimental immunology, vol. 137, no. 2, pp. 279-287.View/Download from: Publisher's site
Tumour necrosis factor (TNF) is critical for sustained protective immunity against Mycobacterium tuberculosis infection. To investigate the relative contributions of macrophage- and T cell-derived TNF towards this immunity T cells from wild-type (WT) or TNF-/- mice were transferred into RAG-/- or TNF-/- mice which were then infected with M. tuberculosis. Infected RAG-/- mice and RAG-/- recipients of TNF deficient T cells developed overwhelming infection, with extensive pulmonary and hepatic necrosis and succumbed with a median of only 16 days infection. By contrast, RAG-/- recipients of WT T cells showed a significant increase in survival with a median of 32 days. Although initial bacterial growth was similar in all groups of RAG-/- mice, the transfer of WT, but not TNF-/-, T cells led to the formation of discrete foci of leucocytes and macrophages and delayed the development of necrotizing pathology. To determine requirements for macrophage-derived TNF, WT or TNF-/- T cells were transferred into TNF-/- mice at the time of M. tuberculosis infection. Transfer of WT T cells significantly prolonged survival and reduced the early tissue necrosis evident in the TNF-/- mice, however, these mice eventually succumbed indicating that T cell-derived TNF alone is insufficient to control the infection. Therefore, both T cell- and macrophage-derived TNF play distinct roles in orchestrating the protective inflammatory response and enhancing survival during M. tuberculosis infection.
Saunders, B.M., Fernando, S.L., Sluyter, R., Britton, W.J. & Wiley, J.S. 2003, 'A loss-of-function polymorphism in the human P2X7 receptor abolishes ATP-mediated killing of mycobacteria.', Journal of immunology (Baltimore, Md. : 1950), vol. 171, no. 10, pp. 5442-5446.View/Download from: Publisher's site
Protective immunity to mycobacterial infections requires activation of the antibacterial mechanisms of infected macrophages. It has previously been reported that ATP treatment of mycobacteria-infected macrophages induces apoptosis mediated via the P2X(7) pathway and that this leads to the death of both the host cell and the internalized bacilli. We have recently identified a single nucleotide polymorphism in the P2X7 gene (1513A-->C), with 1-2% prevalence in the homozygous state, which codes for a nonfunctional receptor. IFN-gamma-primed, mycobacteria-infected macrophages from wild-type individuals were incubated with ATP and this induced apoptosis and reduced mycobacterial viability by 90%. Similar treatment of macrophages from individuals homozygous for the 1513C polymorphism failed to induce apoptosis and did not lead to mycobacterial killing via the P2X(7)-mediated pathway. These data demonstrate that a single nucleotide polymorphism in the P2X7 gene can allow survival of mycobacteria within infected host cells.
Saunders, BM, Dane, A, Briscoe, H & Britton, WJ 2002, 'Characterization of immune responses during infection with Mycobacterium avium strains 100, 101 and the recently sequenced 104.', Immunology and cell biology, vol. 80, no. 6, pp. 544-549.View/Download from: Publisher's site
Mycobacterium avium strain 104 was chosen as the M. avium isolate to sequence, as it is virulent to humans, stable and readily transfectable. As this strain has not been widely studied we sought to investigate the pattern of 104 infection in mice. Bacterial growth and the immune response generated were compared with infection with the low virulence M. avium strain 100, and the high virulence common laboratory strain, 101. Mycobacterium avium strains 104 and 101 grew progressively within mice, while strain 100 was gradually cleared. Strains 104 and 101 induced strong T cell activation and spleen cell cultures produced similar levels of IFN-gamma. In mice infected with strain 100 no significant T cell activation or IFN-gamma production was measured. Further, mice infected with strain 104 or 101 also displayed comparable inflammatory responses and similar granuloma formation, while only minimal inflammation was seen in mice infected with strain 100. Strains 101 and 104 also grew in a similar fashion in bone-marrow-derived macrophages and induced significant levels of TNF and nitric oxide. Thus infection with M. avium strain 104 induced an immunological response comparable to M. avium strain 101 and, with the availability of its sequence, should be a useful tool for designing new vaccines or drugs therapies to treat the increasing incidence of M. avium infection in humans.
Saunders, BM, Frank, AA, Orme, IM & Cooper, AM 2002, 'CD4 is required for the development of a protective granulomatous response to pulmonary tuberculosis.', Cellular immunology, vol. 216, no. 1-2, pp. 65-72.View/Download from: Publisher's site
To confirm the primary role of CD4 T cells in pulmonary tuberculosis, mice with a disruption of their CD4 gene (CD4 KO) were exposed to an aerosol of Mycobacterium tuberculosis and survival, cellular responses in the lung and granuloma development followed. CD8 and NK cells from the lungs of infected CD4 KO mice expressed IFN-gamma and were recruited in numbers similar to those seen in the C57BL/6 mice; recruitment correlated with initial control of bacteria. The major defect in mice lacking CD4 was the significant reduction in total cellular recruitment into the lungs. CD4 KO mice did not generate the typical mononuclear granulomatous lesions, instead the cellular influx was macrophage in character and was localized as perivascular cuffing. Early control of M. tuberculosis growth is therefore independent of CD4+ cells but such cells are required to ensure recruitment of mononuclear cells to the lung and thus ensure long-term survival.
Pearl, J.E., Saunders, B., Ehlers, S., Orme, I.M. & Cooper, A.M. 2001, 'Inflammation and lymphocyte activation during mycobacterial infection in the interferon-gamma-deficient mouse.', Cellular immunology, vol. 211, no. 1, pp. 43-50.View/Download from: Publisher's site
Interferon-gamma is a pivotal cytokine in the protective response to tuberculosis. In its absence rampant bacterial growth results in tissue destruction and death. While macrophage activation is key, this pleiotropic cytokine has other secondary but significant roles. To investigate these roles, both intravenous and aerosol infection of the IFN-gamma gene disrupted (GKO) mouse was performed. For the first time we describe the very similar growth of bacteria, during the initial phase of infection, between control and GKO mice. During this initial phase, however, very different histopathologic consequences between control and GKO mice were observed. Key observations included an early increased accumulation of granulocytes and a much more rapid and pronounced interstitial pneumonia in the GKO mice. As infection developed, GKO mice mounted an antigen-specific response; however, lymphocyte activation was much more rapid in these mice. Of interest is the fact that this increased rapidity occurred prior to significant differences in bacterial number. Taken together these data support a role for IFN-gamma in limiting both initial cellular recruitment and acquired lymphocytic responses to mycobacterial infection. This role may be key in surviving the kind of chronic stimulatory disease caused by Mycobacterium tuberculosis.
Roach, DR, Briscoe, H, Saunders, B, France, MP, Riminton, S & Britton, WJ 2001, 'Secreted lymphotoxin-alpha is essential for the control of an intracellular bacterial infection.', The Journal of experimental medicine, vol. 193, no. 2, pp. 239-246.View/Download from: UTS OPUS or Publisher's site
Although the essential role of tumor necrosis factor (TNF) in the control of intracellular bacterial infection is well established, it is uncertain whether the related cytokines lymphotoxin-alpha (LTalpha3) and lymphotoxin-beta (LTbeta) have independent roles in this process. Using C57Bl/6 mice in which the genes for these cytokines have been disrupted, we have examined the relative contribution of secreted LTalpha3 and membrane-bound LTbeta in the host response to aerosol Mycobacterium tuberculosis infection. To overcome the lack of peripheral lymph nodes in LTalpha-/- and LTbeta-/- mice, bone marrow chimeric mice were constructed. LT-/- chimeras, which lack both secreted LTalpha3 and membrane-bound LTbeta (LT1beta2 and LT2beta1), were highly susceptible and succumbed 5 wk after infection. LTbeta-/- chimeras, which lack only the membrane-bound LTbeta, controlled the infection in a comparable manner to wild-type (WT) chimeric mice. T cell responses to mycobacterial antigens and macrophage responses in LTalpha-/- chimeras were equivalent to those of WT chimeras, but in LTalpha-/- chimeras, granuloma formation was abnormal. LTalpha-/- chimeras recruited normal numbers of T cells into their lungs, but the lymphocytes were restricted to perivascular and peribronchial areas and were not colocated with macrophages in granulomas. Therefore, LTalpha3is essential for the control of pulmonary tuberculosis, and its critical role lies not in the activation of T cells and macrophages per se but in the local organization of the granulomatous response.
Turner, J., Gonzalez-Juarrero, M., Saunders, B.M., Brooks, J.V., Marietta, P., Ellis, D.L., Frank, A.A., Cooper, A.M. & Orme, I.M. 2001, 'Immunological basis for reactivation of tuberculosis in mice.', Infection and immunity, vol. 69, no. 5, pp. 3264-3270.View/Download from: Publisher's site
In this study different inbred strains of mice appeared to control and contain a low dose aerosol infection with Mycobacterium tuberculosis in a similar manner, giving rise to a chronic state of disease. Thereafter, however, certain strains gradually began to show evidence of regrowth of the infection, whereas others consistently did not. Using C57BL/6 mice as an example of a resistant strain and CBA/J mice as an example of a strain susceptible to bacterial growth, we found that these animals revealed distinct differences in the cellular makeup of lung granulomas. The CBA/J mice exhibited a generally poor lymphocyte response within the lungs and vastly increased degenerative pathology at a time associated with regrowth of the infection. As a possible explanation for these events, it was then observed that the CBA/J mouse strain was also less able to upregulate adhesion molecules, including CD11a and CD54, on circulating lymphocytes. These results therefore suggest that a failure to control a chronic infection with M. tuberculosis may reflect an inability to localize antigen-specific lymphocytes within the lung.
Pedrosa, J., Saunders, B.M., Appelberg, R., Orme, I.M., Silva, M.T. & Cooper, A.M. 2000, 'Neutrophils play a protective nonphagocytic role in systemic Mycobacterium tuberculosis infection of mice.', Infection and immunity, vol. 68, no. 2, pp. 577-583.View/Download from: Publisher's site
Evidence showing that neutrophils play a protective role in the host response to infection by different intracellular parasites has been published in the past few years. We assessed this issue with regard to the infection of mice with Mycobacterium tuberculosis. We found a chronic recruitment of neutrophils to the infection foci, namely, to the peritoneal cavity after intraperitoneal infection and to the spleen and liver after intravenous inoculation of the mycobacteria. However, bacilli were never found associated with the recruited neutrophils but rather were found inside macrophages. The intravenous administration of the antineutrophil monoclonal antibody RB6-8C5 during the first week of infection led to selective and severe neutropenia associated with an enhancement of bacillary growth in the target organs of the mice infected by the intravenous route. The neutropenia-associated exacerbation of infection was most important in the liver, where a bacterial load 10-fold higher than that in nonneutropenic mice was found; the exacerbation in the liver occurred both during and after the neutropenic period. Early in infection by M. tuberculosis, neutropenic mice expressed lower levels of mRNAs for gamma interferon and inducible nitric oxide synthase in the liver compared to nondepleted mice. These results point to a protective role of neutrophils in the host defense mechanisms against M. tuberculosis, which occurs early in the infection and is not associated with the phagocytic activity of neutrophils but may be of an immunomodulatory nature.
Saunders, B.M., Frank, A.A., Orme, I.M. & Cooper, A.M. 2000, 'Interleukin-6 induces early gamma interferon production in the infected lung but is not required for generation of specific immunity to Mycobacterium tuberculosis infection.', Infection and immunity, vol. 68, no. 6, pp. 3322-3326.View/Download from: Publisher's site
Immunity to Mycobacterium tuberculosis is dependent upon the generation of a protective gamma interferon (IFN-gamma)-producing T-cell response. Recent studies have suggested that interleukin-6 (IL-6) is required for the induction of a protective T-cell response and that IL-4 may suppress the induction of IFN-gamma. To evaluate the role of the cytokines IL-6 and IL-4 in the generation of pulmonary immunity to M. tuberculosis, IL-6 and IL-4 knockout mice were infected with M. tuberculosis via aerosol. The absence of IL-6 led to an early increase in bacterial load with a concurrent delay in the induction of IFN-gamma. However, mice were able to contain and control bacterial growth and developed a protective memory response to secondary infection. This demonstrates that while IL-6 is involved in stimulating early IFN-gamma production, it is not essential for the development of protective immunity against M. tuberculosis. In contrast, while the absence of IL-4 resulted in increased IFN-gamma production, this had no significant effect upon bacterial growth.
Saunders, BM & Cooper, AM 2000, 'Restraining mycobacteria: role of granulomas in mycobacterial infections.', Immunology and cell biology, vol. 78, no. 4, pp. 334-341.View/Download from: Publisher's site
The generation of prolonged immunity to Mycobacterium tuberculosis requires not only an antigen-specific IFN-gamma-producing T cell response, including both CD4 and CD8 T cells, but also the generation of protective granulomatous lesions, whereby the close apposition of activated T cells and macrophages acts to contain bacterial growth. The importance of the granulomatous lesion in controlling this immune response and in limiting both tissue damage and bacterial dissemination has been considered a secondary event but, as the present review illustrates, is no less important in surviving mycobacterial infection than an antigen-specific T-cell response. The formation of a protective granuloma involves the orchestrated production of a host of chemokines and cytokines, the upregulation of their receptors along with upregulation of addressins, selectins and integrins to coordinate the recruitment, migration and retention of cells to and within the granuloma. In the present review, the principal components of the protective response are outlined and the role of granuloma formation and maintenance in mediating prolonged containment of mycobacteria within the lung is addressed.
Saunders, BM, Frank, AA & Orme, IM 1999, 'Granuloma formation is required to contain bacillus growth and delay mortality in mice chronically infected with Mycobacterium tuberculosis.', Immunology, vol. 98, no. 3, pp. 324-328.View/Download from: Publisher's site
Previous studies in this laboratory have shown that mice with a gene disruption to the intracellular adhesion molecule-1 (ICAM-K/O) express normal cell-mediated immunity but cannot mount delayed-type hypersensitivity reactions following Mycobacterium tuberculosis infection. However, even in the absence of any appreciable granuloma formation, these mice control bacterial growth for at least 90 days. While not required to control the infection initially, we hypothesized that granuloma formation was required to control chronic infection, acting by surrounding infected cells to prevent bacterial dissemination. To test this, ICAM-1 knockout mice were infected with a low dose aerosol of M. tuberculosis Erdman and were found to succumb to infection 136+/-30 days later, displaying highly elevated bacterial loads compared to wild-type mice. Lung tissue from ICAM-K/O mice displayed extensive cellular infiltration and widespread tissue necrosis, but no organized granulomatous lesions were evident, whereas the control mice displayed organized compact granulomas. These data demonstrate that while a granulomatous response is not required initially to control M. tuberculosis infection, absence of granulomas during chronic infection leads to increased bacterial growth and host death. Thus these data support the hypothesis that granuloma formation is required to control chronic infection, acting by surrounding and walling off sites of infection to prevent bacterial dissemination and maintain a state of chronic infection.
Saunders, BM, Frank, AA, Cooper, AM & Orme, IM 1998, 'Role of gamma delta T cells in immunopathology of pulmonary Mycobacterium avium infection in mice.', Infection and immunity, vol. 66, no. 11, pp. 5508-5514.
Several studies have shown that gamma delta T cells influence granuloma development after infection with intracellular pathogens. The role of gamma delta T cells in controlling the influx of inflammatory cells into the lung after Mycobacterium avium infection was therefore examined with gene-disrupted mice (K/O). The mice were infected with either M. avium 724, a progressively replicating highly virulent strain of M. avium, or with M. avium 2-151 SmT, a virulent strain that induces a chronic infection. gamma delta-K/O mice infected with M. avium 2-151 SmT showed early enhanced bacterial growth within the lung compared to the wild-type mice, although granuloma formation was similar in both strains. gamma delta-K/O mice infected with M. avium 724 showed identical bacterial growth within the lung compared to the wild-type mice, but they developed more-compact lymphocytic granulomas and did not show the extensive neutrophil influx and widespread tissue necrosis seen in wild-type mice. These data support the hypothesis that isolates of M. avium that induce protective T-cell-specific immunity are largely unaffected by the absence of gammadelta T cells. Whereas with bacterial strains that induce poor protective immunity, the absence of gamma delta T cells led to significant reductions in both the influx of neutrophils and tissue damage within the lungs of infected mice.
Cooper, A.M., Saunders, B.M., D'Souza, C.D., Frank, A.A. & Orme, I.M. 1997, 'Mycobacterium tuberculosis-driven processes in gene-disrupted mice', Bulletin de l'Institut Pasteur, vol. 95, no. 2, pp. 85-96.View/Download from: Publisher's site
Mice which have disrupted genes for important components of the immune system have been used to study the role of these components in the immune response to infection with Mycobacterium tuberculosis. This has resulted in the identification of interleukin-12 (IL12), interferon- (IFN), tumour necrosis factor- (TNF) and inducible nitric oxide synthase (iNOS) as being essential to the protective response. Less crucial but perhaps more intriguing roles for other molecules such as intercellular adhesion molecule (ICAM) and IL6 have also been suggested by this kind of analysis.
Saunders, B.M. & Cheers, C. 1996, 'Increased lung cell cytotoxic but not bactericidal or phagocytic activity in Mycobacterium avium complex-infected mice.', Cellular immunology, vol. 171, no. 1, pp. 48-54.View/Download from: Publisher's site
Following intranasal infection of mice with Mycobacterium avium complex (MAC) organisms, bacterial growth plateaued at the fourth week postinfection and then remained relatively constant thereafter. Inflammatory cell numbers in the lungs increased 10-fold by 4 weeks postinfection, and lung cell cytotoxicity and the production of NO, H202, and 02- by lung cell cultures had all increased significantly by this time and remained elevated throughout the 15-week experimental study. Although these parameters are generally associated with increased bactericidal activity, there appeared to be a defect in phagocytosis by lung cells, so that bactericidal activity could not be demonstrated in either in vitro or in vivo experiments. This study suggests that following intranasal infection with MAC, inflammatory cells are activated, sufficient to prevent further bacterial growth in vivo but not sufficient to clear the infection. We suggest that the deficiency may lie in the phagocytic activity of the cells.
Saunders, B.M. & Cheers, C. 1996, 'Intranasal infection of beige mice with Mycobacterium avium complex: role of neutrophils and natural killer cells.', Infection and immunity, vol. 64, no. 10, pp. 4236-4241.
Beige mice show increased susceptibility to intranasal infection with organisms of the Mycobacterium avium complex (MAC) compared with their immunocompetent congenics, C57BL/6 mice. This increased susceptibility was clear 2 weeks postinfection, before the activation of the specific immune response. T lymphocytes from 4-week infected beige mice, cultured in vitro, produced amounts of gamma interferon similar to those found in cells from C57BL/6 mice. Macrophage activation, as judged by NO production and lysis of the macrophage target P815, occurred in the lungs of beige mice. Despite the inability of bone marrow-derived NK cells from beige mice to lyse NK-susceptible YAC-1 cells, their gamma interferon production was normal. Monoclonal antibody to NK1.1 was used to deplete C57BL/10 mice of lytic activity against YAC-1 cells without exacerbating infection between 2 and 6 weeks of observation, making it unlikely that any deficiency in NK cells was the cause of susceptibility in beige mice. There was a striking influx of neutrophils in the lungs of beige mice compared with C57BL/6. More than half of the MAC organisms appeared associated with the neutrophils of beige mice, while in C57BL/6 mice, most MAC organisms were associated with cells of macrophage/monocyte morphology. Injection of monoclonal antibody specific for neutrophils failed to eliminate those cells from the lungs of beige mice. However, in C57BL/6 mice, neutrophil numbers were reduced by 95% without exacerbating the infection. We conclude that, although neutrophils are not essential to the relative resistance of C57BL/6 mice, the known deficiencies in both neutrophils and macrophages account for the susceptibility of beige mice.
Saunders, B.M., Zhan, Y. & Cheers, C. 1995, 'Endogenous interleukin-12 is involved in resistance of mice to Mycobacterium avium complex infection.', Infection and immunity, vol. 63, no. 10, pp. 4011-4015.
Acquired cellular resistance against Mycobacterium avium complex (MAC) infections involves the induction of Th1 type gamma interferon (IFN-gamma)-producing T cells. Interleukin-12 (IL-12) is a cytokine involved in the control of IFN-gamma production by T cells and NK cells. The role of IL-12 in the response to MAC infection was investigated. Depletion of endogenous IL-12 by injection of monoclonal antibody prior to and during intranasal infection with MAC resulted in an 150- to 550-fold increase in bacterial load in lung, spleen, and liver homogenates by 10 weeks postinfection. Depletion of IL-12 abrogated the ability of spleen cell cultures to produce IFN-gamma in response to stimulus with live MAC. IL-12-depleted mice showed a 75% decrease in the number of inflammatory cells entering the lungs following intranasal infection with MAC, with significant reductions in cytotoxic activity and nitric oxide production by lung cells. This work suggests that IL-12 plays a major role in the activation of IFN-gamma-producing cells during MAC infection.
Saunders, BM & Cheers, C 1995, 'Inflammatory response following intranasal infection with Mycobacterium avium complex: role of T-cell subsets and gamma interferon.', Infection and immunity, vol. 63, no. 6, pp. 2282-2287.
The role of CD4+ and CD8+ T cells in the response to intranasal infection with a Mycobacterium avium complex isolate (MAC) was investigated. Depletion of CD4+ T cells by injected antibody exacerbated infection in the lung, spleen, and liver. There were decreased numbers of inflammatory cells in the lungs of CD4-depleted mice and a significant decrease in lung cytotoxic activity. The neutrophil response was unaffected, and in CD4-depleted mice, unlike intact infected mice, these cells were found with large numbers of associated MAC. Purified CD4+ splenic T cells produced gamma interferon (IFN-gamma) in vitro in response to MAC antigen. IFN-gamma production by cultured spleen, lung, or mediastinal lymph node cells was markedly reduced in CD4-depleted mice. In contrast, CD8+ T cells did not produce IFN-gamma in vitro, and depletion of CD8+ T cells from infected mice had no effect on bacterial growth or lung cell activation. Depletion of IFN-gamma by injected monoclonal antibody had effects similar to those of CD4 depletion, namely, exacerbation of infection and decreased lung cell cytotoxicity. We conclude that CD4+ T cells are the main T cells involved in the lung response to MAC infection and that this response is at least partially dependent on the production of IFN-gamma.
Saunders, BM, Liu, Z, Zhan, Y & Cheers, C 1993, 'Interleukin-6 production during chronic experimental infection.', Immunology and cell biology, vol. 71 ( Pt 4), pp. 275-280.View/Download from: Publisher's site
The appearance of interleukin-6 (IL-6) in serum of mice was monitored during the course of chronic infection with either Brucella abortus vaccine strain 19 or a virulent Mycobacterium avium Complex (MAC) isolate. Serum IL-6 during brucella infection was higher than during infection with MAC, despite similar numbers of bacteria. Furthermore, IL-6 titres decreased after the peak of infection, falling to baseline levels before these chronic infections were eradicated. The ability of peritoneal cells or spleen cell suspensions to produce IL-6 under either specific or non-specific stimulus was greatly enhanced by infection. While production of IL-6 by these cultures was apparently mostly independent of T cells, T cells from infected mice could produce an IL-6 response. Thus CD4+ T lymphocytes prepared from mice which had recovered from B. abortus infection, cultured with antigen and antigen presenting cells, resulted in IL-6 production, which was not observed in similarly cultured CD8+ T cells, indicating a role for T cells.
Barry, SE, Ellis, M, Yang, Y, Guan, G, Wang, X, Britton, WJ & Saunders, BM 2018, 'Identification of a plasma microRNA profile in untreated pulmonary tuberculosis patients that is modulated by anti-mycobacterial therapy.', The Journal of infection.View/Download from: Publisher's site
microRNA expression profiles are of interest as a biomarker of tuberculosis (TB). How anti-TB therapy effects miRNA profiles is unknown and was examined.We identified 87 plasma miRNAs that were significantly modified in an exploratory group of 19 Chinese pulmonary TB (PTB) patients compared to 14 healthy controls. We selected 10 of these miRNAs for analysis in a cohort of 100 PTB patients prior to, and at one, two and six months during treatment.Five miRNAs were differentially expressed in PTB patients compared to controls at diagnosis; miRs -29a and -99b were up-regulated, whilst miRs -21, -146a and -652 were down-regulated. A combination of 5 miRNA distinguished TB from healthy controls with a sensitivity of 94%, a specificity of 88%, and an AUC of 0.976. Within one month of treatment, significant changes in miRs -29a, -99b, -26a and 146a levels occurred in successfully treated patients, although not all miRNAs returned to baseline by treatment completion.A 5-miRNA signature shows potential for development as a novel biomarker for TB disease with potential to predict response to treatment. The failure of all miRNA to return to baseline levels may reflect ongoing remodelling in the lung parenchyma that continues after completion of anti-TB therapy.
Center for Research Excellence- TB
Prof Warwick Britton - Centenary Institute Sydney
Dr Patrick Bertolini- Centenary Insittute, Sydney
Prof Gobardhan Das, Jawaharlal Nehru University