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ABSTRACT: Mannose-binding lectin (MBL) is a humoral pattern-recognition molecule important for host defense. Although recent genetic studies suggest an involvement of MBL/MASP2-associated pathways in Chagas' disease, it is currently unknown whether MBL plays a role in host resistance to the intracellular protozoan Trypanosoma cruzi, the causative agent of Chagas' disease. In this study we employed MBL(-/-) mice to assess the role of MBL in resistance to experimental infection with T. cruzi. T. cruzi infection enhanced tissue expression of MBL both at the mRNA and protein level. Similarly, symptomatic acute Chagas' disease patients displayed increased serum concentrations of MBL compared to patients with indeterminate, asymptomatic forms of the disease. Furthermore, increased parasite loads in the blood and/or tissue were observed in MBL(-/-) mice compared to WT controls. This was associated with reduced systemic levels of IL-12/23p40 in MBL(-/-) mice. Importantly, MBL(-/-) mice infected with a cardiotropic strain of T. cruzi displayed increased myocarditis and cardiac fibrosis compared to WT controls. The latter was accompanied by elevated hydroxyproline content and mRNA levels of collagen-1 and -6 in the heart. These observations point to a previously unappreciated role for MBL in regulating host resistance and cardiac inflammation during infection with a major human pathogen.
PLoS ONE 01/2012; 7(11):e47835. · 4.09 Impact Factor
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ABSTRACT: Chagas' disease is a zoonosis prevalent in Latin America that is caused by the protozoan Trypanosoma cruzi. The immunopathogenesis of cardiomyopathy, the main clinical problem in Chagas' disease, has been extensively studied but is still poorly understood. In this study, we systematically compared clinical, microbiologic, pathologic, immunologic, and molecular parameters in two mouse models with opposite susceptibility to acute myocarditis caused by the myotropic Colombiana strain of T. cruzi: C3H/HeSnJ (100% mortality, uncontrolled parasitism) and C57BL/6J (<10% mortality, controlled parasitism). T. cruzi induced differential polarization of immunoregulatory cytokine mRNA expression in the hearts of C57BL/6J versus C3H/HeSnJ mice; however, most differences were small. The difference in IL-10 expression was exceptional (C57BL/6J 8.7-fold greater than C3H/HeSnJ). Consistent with this, hearts from infected C57BL/6J mice, but not C3H/HeSnJ mice, had a high frequency of total IL-10-producing CD8(+) T cells and both CD4(+) and CD8(+) subsets of IFN-γ(+)IL-10(+) double-producing T cells. Furthermore, T. cruzi infection of IL-10(-/-) C57BL/6J mice phenocopied fatal infection in wild-type C3H/HeSnJ mice with complete loss of parasite control. Adoptive transfer experiments indicated that T cells were a source of protective IL-10. Thus, in this system, IL-10 production by T cells promotes T. cruzi control and protection from fatal acute myocarditis.
The Journal of Immunology 12/2011; 188(2):649-60. · 5.79 Impact Factor
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ABSTRACT: Cell-mediated adaptive immunity is critical for host defense, but little is known about T cell behavior during delivery of effector function. Here we investigate relationships among antigen presentation, T cell motility, and local production of effector cytokines by CD4+ T cells within hepatic granulomas triggered by Bacille Calmette-Guérin or Mycobacterium tuberculosis. At steady-state, only small fractions of mycobacteria-specific T cells showed antigen-induced migration arrest within granulomas, resulting in low-level, polarized secretion of cytokines. However, exogenous antigen elicited rapid arrest and robust cytokine production by the vast majority of effector T cells. These findings suggest that limited antigen presentation and/or recognition within granulomas evoke a muted T cell response drawing on only a fraction of the host's potential effector capacity. Our results provide new insights into the regulation of host-protective functions, especially how antigen availability influences T cell dynamics and, in turn, effector T cell function during chronic infection.
Immunity 05/2011; 34(5):807-19. · 21.64 Impact Factor
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ABSTRACT: There is interest in identifying the pattern recognition receptors involved in initiating protective or non-protective host responses to Mycobacterium tuberculosis (Mtb). Here we explored the role of the Syk/CARD9-coupled receptor, Dectin-1, using an aerosol model of Mtb infection in wild-type and Dectin-1 deficient mice. We observed a reduction in pulmonary bacilli burdens in the Dectin-1 deficient animals, but this did not correlate with significant changes in pulmonary pathology, cytokine levels or ability of these animals to survive the infection. Thus Dectin-1 makes a minor contribution to susceptibility to Mtb infections in mice.
Microbes and Infection 10/2010; 13(2):198-201. · 3.10 Impact Factor
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ABSTRACT: Type I IFN has been demonstrated to have major regulatory effects on the outcome of bacterial infections. To assess the effects of exogenously induced type I IFN on the outcome of Mycobacterium tuberculosis infection, we treated pathogen-exposed mice intranasally with polyinosinic-polycytidylic acid condensed with poly-l-lysine and carboxymethylcellulose (Poly-ICLC), an agent designed to stimulate prolonged, high-level production of type I IFN. Drug-treated, M. tuberculosis-infected WT mice, but not mice lacking IFN-alphabeta receptor 1 (IFNalphabetaR; also known as IFNAR1), displayed marked elevations in lung bacillary loads, accompanied by widespread pulmonary necrosis without detectable impairment of Th1 effector function. Importantly, lungs from Poly-ICLC-treated M. tuberculosis-infected mice exhibited a striking increase in CD11b+F4/80+Gr1int cells that displayed decreased MHC II expression and enhanced bacterial levels relative to the same subset of cells purified from infected, untreated controls. Moreover, both the Poly-ICLC-triggered pulmonary recruitment of the CD11b+F4/80+Gr1int population and the accompanying exacerbation of infection correlated with type I IFN-induced upregulation of the chemokine-encoding gene Ccl2 and were dependent on host expression of the chemokine receptor CCR2. The above findings suggest that Poly-ICLC treatment can detrimentally affect the outcome of M. tuberculosis infection, by promoting the accumulation of a permissive myeloid population in the lung. In addition, these data suggest that agents that stimulate type I IFN should be used with caution in patients exposed to this pathogen.
The Journal of clinical investigation 04/2010; 120(5):1674-82. · 15.39 Impact Factor
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Gundula Min-Oo,
Kodjo Ayi,
Silayuv E Bongfen,
Mifong Tam,
Irena Radovanovic,
Susan Gauthier,
Helton Santiago, Antonio Gigliotti Rothfuchs,
Ester Roffê,
Alan Sher,
Alaka Mullick,
Anny Fortin,
Mary M Stevenson,
Kevin C Kain,
Philippe Gros
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ABSTRACT: In mice, loss of pantetheinase activity causes susceptibility to infection with Plasmodium chabaudi AS. Treatment of mice with the pantetheinase metabolite cysteamine reduces blood-stage replication of P. chabaudi and significantly increases survival. Similarly, a short exposure of Plasmodium to cysteamine ex vivo is sufficient to suppress parasite infectivity in vivo. This effect of cysteamine is specific and not observed with a related thiol (dimercaptosuccinic acid) or with the pantethine precursor of cysteamine. Also, cysteamine does not protect against infection with the parasite Trypanosoma cruzi or the fungal pathogen Candida albicans, suggesting cysteamine acts directly against the parasite and does not modulate host inflammatory response. Cysteamine exposure also blocks replication of P. falciparum in vitro; moreover, these treated parasites show higher levels of intact hemoglobin. This study highlights the in vivo action of cysteamine against Plasmodium and provides further evidence for the involvement of pantetheinase in host response to this infection.
Experimental Parasitology 02/2010; 125(4):315-24. · 2.12 Impact Factor
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ABSTRACT: Although IL-12/23p40 is known to play a major role in host resistance to Mycobacterium spp, the cellular source, tissue localization, and regulation of p40 production during mycobacterial infection in vivo has been unclear. In this study, we used IL-12/23p40eYFP (yet40) reporter mice to track expression of the cytokine following Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection. We found that in spleens of these mice, p40 production is initiated by a transient burst from CD11b(low)CD11c(+) dendritic cells (DC) which are later replaced at the onset of granuloma formation by CD11b(high)CD11c(+) DC as the major source of the cytokine. The latter subset was also found to be the key producer of DC-derived p40 in nonlymphoid tissue and in both spleen and liver optimal production of the cytokine was regulated by endogenous TNF-alpha. Although BCG and p40-expressing DC were both observed in splenic white pulp, p40(+) DC rarely colocalized with bacilli. Indeed, in vitro flow cytometry and confocal microscopy indicated that the presence of intracellular bacteria is not required for p40 production by DC and Transwell experiments confirmed that soluble mycobacterial components are sufficient for inducing cytokine expression by these cells. Moreover, when stimulated with LPS, DC directly infected with BCG showed impaired IL-12p40 production in vitro. Together, our findings establish CD11b(high) DC as a major source of IL-12/23p40 during mycobacterial infection in situ and implicate both soluble mycobacterial products and TNF-alpha in stimulating sustained production of p40 by these cells.
The Journal of Immunology 07/2009; 182(11):6915-25. · 5.79 Impact Factor
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ABSTRACT: The leukocyte response in inflammation is characterized by an initial recruitment of polymorphonuclear leukocytes (PMN) preceding a second wave of monocytes to the site of injury or infection. In the mouse, 2 populations of monocytes have been identified, Gr1(-)CCR2(-)CX3CR1(hi) resident monocytes and Gr1(+)CCR2(+)CX3CR1(lo) inflammatory monocytes. Here, intravital microscopy of the musculus cremaster and a subcutaneous air pouch model were used to investigate a possible link between PMN extravasation and the subsequent emigration of inflammatory monocytes in response to local stimulation with PAF. In mice that were made neutropenic by injection of a PMN-depleting antibody, the extravasation of inflammatory monocytes, but not resident monocytes, was markedly reduced compared with mice with intact white blood cell count but was restored by local treatment with secretion of activated PMN. Components of the PMN secretion were found to directly activate inflammatory monocytes and further examination revealed PMN-derived LL-37 and heparin-binding protein (HBP/CAP37/azurocidin) as primary mediators of the recruitment of inflammatory monocytes via activation of formyl-peptide receptors. These data show that LL-37 and HBP specifically stimulate mobilization of inflammatory monocytes. This cellular cross-talk functionally results in enhanced cytokine levels and increased bacterial clearance, thus boosting the early immune response.
Blood 06/2008; 112(4):1461-71. · 9.90 Impact Factor
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ABSTRACT: Granulomas play a key role in host protection against mycobacterial pathogens, with their breakdown contributing to exacerbated disease. To better understand the initiation and maintenance of these structures, we employed both high-resolution multiplex static imaging and intravital multiphoton microscopy of Mycobacterium bovis BCG-induced liver granulomas. We found that Kupffer cells directly capture blood-borne bacteria and subsequently nucleate formation of a nascent granuloma by recruiting both uninfected liver-resident macrophages and blood-derived monocytes. Within the mature granuloma, these myeloid cell populations formed a relatively immobile cellular matrix that interacted with a highly dynamic effector T cell population. The efficient recruitment of these T cells was highly dependent on TNF-alpha-derived signals, which also maintained the granuloma structure through preferential effects on uninfected macrophage populations. By characterizing the migration of both innate and adaptive immune cells throughout the process of granuloma development, these studies provide a new perspective on the cellular events involved in mycobacterial containment and escape.
Immunity 03/2008; 28(2):271-84. · 21.64 Impact Factor
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ABSTRACT: Dectin-1 is a fungal pattern recognition receptor that binds to beta-glucans and triggers cytokine production by facilitating interaction with TLR2 or by directly activating spleen tyrosine kinase (Syk). To assess the possible role of Dectin-1 in the innate response to mycobacteria, we used an in vitro system in which IL-12p40 production is measured in splenic dendritic cells (SpDC) following exposure to live Mycobacterium tuberculosis bacilli. Treatment of SpDC with laminarin or glucan phosphate, two molecules known to block Dectin-1-dependent activity, led to a reduction in M. tuberculosis-induced IL-12p40 as well as IL-12p70 production. Moreover, SpDC from Dectin-1-/- chimeric mice displayed reduced IL-12p40 production in response to mycobacteria when compared with Dectin-sufficient DC. Laminarin treatment also inhibited mycobacterial-induced IL-12p40 production in DC from TLR2-/- mice, arguing that Dectin-1 functions independently of TLR2 signaling in this system. Importantly, a Dectin-1 fusion protein was found to directly bind to live mycobacteria in a laminarin-inhibitable manner indicating the presence of ligands for the receptor in the bacterium and laminarin pretreatment resulted in reduced association of mycobacteria to SpDC. In additional experiments, mycobacterial stimulation was shown to be associated with increased phosphorylation of Syk and this response was inhibited by laminarin. Furthermore, pharmacologic inhibition of Syk reduced the M. tuberculosis-induced IL-12p40 response. Together, these findings support a role for Dectin-1 in promoting M. tuberculosis-induced IL-12p40 production by DC in which the receptor augments bacterial-host cell interaction and enhances the subsequent cytokine response through an unknown mechanism involving Syk signaling.
The Journal of Immunology 10/2007; 179(6):3463-71. · 5.79 Impact Factor
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ABSTRACT: Although it is known that IFN-gamma-secreting T cells are critical for control of Mycobacterium tuberculosis infection, the contribution of IFN-gamma produced by NK cells to host resistance to the pathogen is less well understood. By using T cell-deficient RAG(-/-) mice, we showed that M. tuberculosis stimulates NK cell-dependent IFN-gamma production in naive splenic cultures and in lungs of infected animals. More importantly, common cytokine receptor gamma-chain(-/-)RAG(-/-) animals deficient in NK cells, p40(-/-)RAG(-/-), or anti-IFN-gamma mAb-treated RAG(-/-) mice displayed significantly increased susceptibility to M. tuberculosis infection compared with untreated NK-sufficient RAG(-/-) controls. Studies comparing IL-12 p40- and p35-deficient RAG(-/-) mice indicated that IL-12 plays a more critical role in the induction of IFN-gamma-mediated antimycobacterial effector functions than IL-23 or other p40-containing IL-12 family members. The increased susceptibility of IL-12-deficient or anti-IFN-gamma mAb-treated RAG(-/-) mice was associated not only with elevated bacterial loads, but also with the development of granulocyte-enriched foci in lungs. This tissue response correlated with increased expression of the granulocyte chemotactic chemokines KC and MIP-2 in NK as well as other leukocyte populations. Interestingly, depletion of granulocytes further increased bacterial burdens and exacerbated pulmonary pathology in these animals, revealing a compensatory function for neutrophils in the absence of IFN-gamma. The above observations indicate that NK cell-derived IFN-gamma differentially regulates T-independent resistance and granulocyte function in M. tuberculosis infection and suggest that this response could serve as an important barrier in AIDS patients or other individuals with compromised CD4+ T cell function.
The Journal of Immunology 12/2006; 177(10):7086-93. · 5.79 Impact Factor
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ABSTRACT: STAT1 mediates signaling in response to IFN-alpha, -beta, and -gamma, cytokines required for protective immunity against several viral, bacterial, and eukaryotic pathogens. The protective role of STAT1 in the control of intranasal infection with the obligate intracellular bacterium Chlamydia pneumoniae was analyzed. IFN-gamma-/- or IFN-gamma receptor (R)-/- mice were highly susceptible to infection with C. pneumoniae. We found that STAT1-/- mice were even more susceptible to C. pneumoniae than IFN-gamma-/- or IFN-gammaR-/- mice. Phosphorylation of STAT1 was detected in the lungs of C. pneumoniae-infected wild-type, IFN-gammaR-/-, and IFN-alphabetaR-/- mice, but not in mice lacking both IFN-alphabetaR and IFN-gammaR. In line with this, IFN-alphabetaR-/-/IFN-gammaR-/- mice showed increased susceptibility to infection compared with IFN-gammaR-/- mice. However, C. pneumoniae-infected IFN-alphabetaR-/- or IFN regulatory factor 3-/- mice showed no increased susceptibility and similar IFN-gamma expression compared with wild-type mice. CD4+ or CD8+ cells released IFN-gamma in vivo and conferred protection against C. pneumoniae in a STAT1-independent manner. In contrast, STAT1 mediated a nonredundant protective role of nonhemopoietic cells but not of hemopoietic cells. Nonhemopoietic cells accounted for the expression of STAT1-mediated indoleamine 2, 3-dioxygenase and the p47 GTPase LRG-47, but not inducible NO synthase mRNA. In summary, we demonstrate that STAT1 mediates a cooperative effect of IFN-alphabeta and IFN-gamma on nonhemopoietic cells, resulting in protection against C. pneumoniae.
The Journal of Immunology 07/2006; 176(11):6982-90. · 5.79 Impact Factor
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ABSTRACT: Infection of murine bone marrow-derived macrophages (BMMphi) with Chlamydia pneumoniae induces IFN-alphabeta-dependent IFN-gamma secretion that leads to control of the intracellular bacterial growth. Enhanced growth of C. pneumoniae in Toll-like receptor (TLR) 4(-/-) and myeloid differentiation factor (MyD) 88(-/-) (but not TLR2(-/-), TLR6(-/-), or TLR9(-/-)) BMMphi is shown in this study. Reduced accumulation of IFN-alpha and IFN-gamma mRNA was also observed in TLR4(-/-)- and MyD88(-/-)-infected cells. IL-1R and IL-18R signaling did not account for differences between MyD88(-/-) and wild-type BMMphi. Surprisingly, infection-induced NF-kappaB activation as well as TNF-alpha, IL-1, or IL-6 mRNA expression were all normal in TLR4(-/-) and MyD88(-/-) cells. Phosphorylation of the transcription factor STAT1 during bacterial infection is IFN-alphabeta dependent, and necessary for increased IFN-gamma mRNA accumulation and chlamydial growth control. Signaling through common cytokine receptor gamma-chain and RNA-dependent protein kinase both mediated IFN-alphabeta-dependent enhancement of IFN-gamma mRNA levels. Accumulation of IFN-gamma mRNA and control of C. pneumoniae growth required NF-kappaB activation. Such NF-kappaB activation was independent of IFN-alphabeta, STAT1, and RNA-dependent protein kinase. In summary, C. pneumoniae-induced IFN-gamma expression in BMMphi is controlled by a TLR4-MyD88-IFN-alphabeta-STAT1-dependent pathway, as well as by a TLR4-independent pathway leading to NF-kappaB activation.
The Journal of Immunology 06/2004; 172(10):6345-53. · 5.79 Impact Factor
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ABSTRACT: By using a T, B, or NK cell-deficient mouse strain (recombinase-activating gene (RAG)-1(-/-)/common cytokine receptor gamma-chain (gamma(C)R)), and T and B cell and IFN-gamma-deficient (RAG-1(-/-)/IFN-gamma(-/-)) mice, we have studied the generation of immunity against infection by Chlamydia pneumoniae. We found that IFN-gamma secreted by innate-cell populations protect against C. pneumoniae infection. However, NK cells were not needed for such IFN-gamma-dependent innate immune protection. Inoculation of wild type, but not IFN-gamma(-/-) bone marrow-derived macrophages protected RAG-1(-/-)/IFN-gamma(-/-) mice against C. pneumoniae infection. In line, pulmonary macrophages from RAG-1(-/-) C. pneumoniae-infected mice expressed IFN-gamma mRNA. Reconstitution of RAG-1(-/-)/gamma(c)R(-/-) or RAG-1(-/-)/IFN-gamma(-/-) mice with CD4(+) or CD8(+) cells by i.v. transfer of FACS sorted wild type spleen cells (SC) increased resistance to C. pneumoniae infection. On the contrary, no protection was observed upon transfer of IFN-gamma(-/-) CD4(+) or IFN-gamma(-/-) CD8(+) SC. T cell-dependent protection against C. pneumoniae was weaker when IFN-gammaR(-/-) CD4(+) or IFN-gammaR(-/-) CD8(+) SC were inoculated into RAG-1(-/-)/IFN-gamma(-/-) mice. Thus both nonlymphoid and T cell-derived IFN-gamma can play a central and complementary role in protection against C. pneumoniae. IFN-gamma secreted by nonlymphoid cells was not required for T cell-mediated protection against C. pneumoniae; however, IFN-gamma regulated T cell protective functions.
The Journal of Immunology 03/2004; 172(4):2407-15. · 5.79 Impact Factor
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ABSTRACT: CD44 has been implicated in immune and inflammatory processes. We have analyzed the role of CD44 in the outcome of Listeria monocytogenes infection in murine bone marrow-derived macrophages (BMM). Surprisingly, a dramatically decreased intracellular survival of L. monocytogenes was observed in CD44(-/-) BMM. CD44(-/-) heart or lung fibroblast cultures also showed reduced bacterial levels. Moreover, livers from CD44(-/-)-infected mice showed diminished levels of L. monocytogenes. In contrast, intracellular growth of Salmonella enterica serovar Typhimurium was the same in CD44(-/-) and control BMM. The CD44-mediated increased bacterial proliferation was not linked to altered BMM differentiation or to secretion of soluble factors. CD44 did not mediate listerial uptake, and it played no role in bacterial escape from the primary phagosome or formation of actin tails. Furthermore, CD44-enhanced listerial proliferation occurred in the absence of intracellular bacterial spreading. Interestingly, coincubation of BMM with hyaluronidase or anti-CD44 antibodies that selectively inhibit hyaluronan binding increased intracellular listerial proliferation. Treatment of cells with hyaluronan, in contrast, diminished listerial growth and induced proinflammatory transcript levels. We suggest that L. monocytogenes takes advantage of the CD44-mediated signaling to proliferate intracellularly, although binding of CD44 to certain ligands will inhibit such response.
Infection and Immunity 08/2003; 71(7):4102-11. · 4.16 Impact Factor
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ABSTRACT: Chlamydia are intracellular bacteria which infect many vertebrates, including humans. They cause a myriad of severe diseases, ranging from asymptomatic infection to pneumonia, blindness or infertility. IFN-gamma plays an important role in defense against acute infection and in the establishment of persistence. Chlamydia have evolved mechanisms to escape IFN-gamma functions. IFN-gamma-mediated effector mechanisms may involve effects on the metabolism of tryptophan or iron, on the inducible NO synthase (iNOS), on the secretion of chemokines and adhesion molecules or on the regulation of T-cell activities. IFN-gamma is secreted by the innate and the adaptive arms of the immune system. Within the former, Chlamydia-infected macrophages express IFN-gamma that in turn mediates resistance to infection. IFN-alpha/beta are pivotal for both IFN-gamma- and iNOS-mediated resistance to chlamydial infection in macrophages.
Current Opinion in Immunology 09/2002; 14(4):444-51. · 9.52 Impact Factor
