CD43 Is Required for Optimal Growth Inhibition of Mycobacterium tuberculosis in Macrophages and in Mice

Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
The Journal of Immunology (Impact Factor: 4.92). 09/2005; 175(3):1805-12. DOI: 10.4049/jimmunol.175.3.1805
Source: PubMed


We explored the role of macrophage (Mphi) CD43, a transmembrane glycoprotein, in the pathogenesis of Mycobacterium tuberculosis. Using gene-deleted mice (CD43-/-), we assessed the association of the bacterium with distinct populations of Mphi and found that CD43-/- Mphi bound less M. tuberculosis than CD43+/+ Mphi. Increased infective doses did not abrogate this difference. However, reduced association due to the absence of CD43 could be overcome by serum components. Mphi from heterozygote mice, which express 50% of wild-type CD43, bound more bacteria than CD43-/- but less than CD43+/+, proving that the gene dose of CD43 correlates with binding of M. tuberculosis. Furthermore, the reduced ability of CD43-/- Mphi to bind bacteria was restricted to mycobacterial species. We also found that the survival and replication of M. tuberculosis within Mphi was enhanced significantly in the absence of CD43, making this the first demonstration that the mechanism of mycobacterial entry influences its subsequent growth. Most importantly, we show here that the absence of CD43 in mice aerogenically infected with M. tuberculosis results in an increased bacterial load during both the acute and chronic stages of infection and more rapid development of granulomas, with greater lung involvement and distinctive cellularity.

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Available from: April Kaur Randhawa, Oct 04, 2015
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    • "This procedure has previously been shown by our lab to be an effective means of dispersing mycobacterial bacilli without causing detectable cell lysis (Stokes et al., 2004). Previous work by Randhawa et al. (2005) showed that CD43 -/-MF have a reduced capacity to bind M. tuberculosis, but increasing the cfu inoculum overcame this limitation. As preliminary work showed that an moi of 60:1 for CD43 +/+ cells and 100:1 for CD43 -/-cells resulted in a similar level of bacterial binding in binding medium alone, these two moi were used for infections of the BMMF. "
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    ABSTRACT: CD43 is a large sialylated glycoprotein found on the surface of haematopoietic cells and has been previously shown to be necessary for efficient macrophage binding and immunological responsiveness to Mycobacterium tuberculosis. Using capsular material from M. tuberculosis and recombinant CD43-Fc, we have employed affinity chromatography to show that Cpn60.2 (Hsp65, GroEL), and to a lesser extent DnaK (Hsp70), bind to CD43. Competitive inhibition using recombinant protein and polyclonal F(ab')(2) antibody-mediated epitope masking studies were used to evaluate M. tuberculosis binding to CD43(+/+) versus CD43(-/-) macrophages. Results showed that Cpn60.2, but not DnaK, acts as a CD43-dependent mycobacterial adhesin for macrophage binding. Assessment of the specific binding between Cpn60.2 and CD43 showed it to be saturable, with a comparatively weak affinity in the low micromolar range. We have also shown that the ability of Cpn60.2 to competitively inhibit M. tuberculosis binding to macrophages is shared by the Escherichia coli homologue, GroEL, but not by the mouse and human Hsp60 homologues. These findings add to a growing field of research that implicates molecular chaperones as having extracellular functions, including bacterial adherence to host cells. Thus, CD43 may act as a Pattern Recognition Receptor (PRR) for bacterial homologues of the 60 kDa molecular chaperone.
    Cellular Microbiology 11/2010; 12(11):1634-47. DOI:10.1111/j.1462-5822.2010.01496.x · 4.92 Impact Factor
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    • "Studies on primary macrophages revealed no difference in binding of mycobacteria and subsequent TNF production in the presence or absence of SR-B1 (Fig. 3B and C). However, binding of mycobacteria to both wild type and SR-B1−/− BMDmØ was much stronger than to alveolar macrophages (Fig. 3B), and this is likely to be due to the expression of other recognition receptors on these cells, as has been shown previously [11], [31]. We also found that serum blocked binding of mycobacteria to both wild type and SR-B1−/− alveolar macrophages and BMDmØ (data not shown) as opposed to an earlier observation where serum components increased binding to BMDmØ [31]. "
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    ABSTRACT: The interaction between Mycobacterium tuberculosis (Mtb) and host cells is complex and far from being understood. The role of the different receptor(s) implicated in the recognition of Mtb in particular remains poorly defined, and those that have been found to have activity in vitro were subsequently shown to be redundant in vivo. To identify novel receptors involved in the recognition of Mtb, we screened a macrophage cDNA library and identified scavenger receptor B class 1 (SR-B1) as a receptor for mycobacteria. SR-B1 has been well-described as a lipoprotein receptor which mediates both the selective uptake of cholesteryl esters and the efflux of cholesterol, and has also recently been implicated in the recognition of other pathogens. We show here that mycobacteria can bind directly to SR-B1 on transfected cells, and that this interaction could be inhibited in the presence of a specific antibody to SR-B1, serum or LDL. We define a variety of macrophage populations, including alveolar macrophages, that express this receptor, however, no differences in the recognition and response to mycobacteria were observed in macrophages isolated from SR-B1(-/-) or wild type mice in vitro. Moreover, when wild type and SR-B1(-/-) animals were infected with a low dose of Mtb (100 CFU/mouse) there were no alterations in survival, bacterial burdens, granuloma formation or cytokine production in the lung. However, significant reduction in the production of TNF, IFNgamma, and IL10 were observed in SR-B1(-/-) mice following infection with a high dose of Mtb (1000 CFU/mouse), which marginally affected the size of inflammatory foci but did not influence bacterial burdens. Deficiency of SR-B1 also had no effect on resistance to disease under conditions of varying dietary cholesterol. We did observe, however, that the presence of high levels of cholesterol in the diet significantly enhanced the bacterial burdens in the lung, but this was independent of SR-B1. SR-B1 is involved in mycobacterial recognition, but this receptor plays only a minor role in anti-mycobacterial immunity in vivo. Like many other receptors for these pathogens, the loss of SR-B1 can be functionally compensated for under normal conditions.
    PLoS ONE 12/2009; 4(12):e8448. DOI:10.1371/journal.pone.0008448 · 3.23 Impact Factor
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    • "The growth of M. tuberculosis within Mf monolayers was evaluated by infecting BMMf and determining bacterial cfu counts over a 7 day period, as previously described (Stokes and Doxsee, 1999; Randhawa et al., 2005). Briefly, 2.5 ¥ 10 5 BMMf were cultured on 13 mm acid-washed sterile glass coverslips in 24-well plates for 7 days, at which point media were replaced with 0.5 ml of supplemented RPMI Ϯ 100 U ml -1 recombinant IFN-g, and left overnight. "
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    ABSTRACT: Establishment of Tuberculosis infection begins with the successful entry and survival of the pathogen within macrophages. We previously showed that macrophage CD43 is required for optimal uptake and growth inhibition of Mycobacterium tuberculosis both in vitro and in vivo. Here, we explore the mechanisms by which CD43 restricts mycobacterial growth in murine macrophages. We found that although M. tuberculosis grows more readily in resting CD43-/- macrophages, priming of cells with IFN-gamma returns the bacterial growth rate to that seen in CD43+/+ cells. To discern the mechanisms by which M. tuberculosis exhibits enhanced growth within resting CD43-/- macrophages, we assessed the induction of inflammatory mediators in response to infection. We found that absence of CD43 resulted in reduced production of TNF-alpha, IL-12 and IL-6 by M. tuberculosis-infected macrophages. We also found that infected resting, but not activated CD43-/- macrophages, showed decreased apoptosis and increased necrosis. Exogenous addition of the pro-inflammatory cytokine TNF-alpha restored control of M. tuberculosis growth and induction of apoptosis to CD43+/+ levels. We propose that CD43 is involved in the inflammatory response to M. tuberculosis and, through the induction of pro-inflammatory mediators, can regulate apoptosis to control intracellular growth of the bacterium.
    Cellular Microbiology 10/2008; 10(10):2105-17. DOI:10.1111/j.1462-5822.2008.01194.x · 4.92 Impact Factor
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