[Fatal tuberculosis despite adaptive immune response in the absence of MyD88].
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Adaptor Proteins, Signal Transducing↗
Biomedical subjects
Bernhard Ryffel
Publications and source records attributed to Bernhard Ryffel.
Reduced local growth and spread but preserved pathogenicity of a DeltapurC Mycobacterium tuberculosis auxotrophic mutant in gamma interferon receptor-deficient mice after aerosol infection.
We compared the growth levels and pathogenicities of the Mycobacterium tuberculosis MT103 clinical strain with those of the DeltapurC mutant strain MYC1551, which is auxotrophic for purine in wild-type and gamma interferon receptor (IFN-gammaR)-deficient mice. The DeltapurC strain MYC1551 grew initially in both wild-type and IFN-gammaR-deficient mice upon aerosol infection, but it grew much less than strain MT103 did. Despite the comparable bacterial burdens of the mice, IFN-gammaR-deficient mice succumbed to infection with DeltapurC strain MYC1551 from necrotic pneumonia within 6 weeks of those infected with MT103. In conclusion, the DeltapurC mutant MYC1551 displays reduced growth but retains pathogenicity. Therefore, the use of mutant strains of M. tuberculosis as live vaccines may not be recommended.
Acute Disease↗
Arthropod-derived protein EV131 inhibits histamine action and allergic asthma.
Histamine is an important mediator of allergic responses. Arthropods express several biologically active proteins in their saliva, which may allow a prolonged blood meal on the host. Proteins identified and expressed include histamine, serotonin, tryptase, and complement binding proteins. We review here data that scavenging of endogenous histamine by the histamine-binding protein EV131 has a profound inhibitory effect on allergic asthma. Aerosol administration of EV131 prevented airway hyperreactivity and abrogated peribronchial inflammation, eosinophil recruitment, mucus hypersecretion, and IL-4 and IL-5 secretion. Saturation with histamine abrogated the inhibitory effect of EV131 on bronchial hyperreactivity. The data suggest that histamine plays a role in allergies and that scavenging of histamine by EV131 may represent a novel therapeutic strategy in the treatment of allergic diseases.
Animals↗
Novel bacterial delivery system with attenuated Salmonella typhimurium carrying plasmid encoding Mtb antigen 85A for mucosal immunization: establishment of proof of principle in TB mouse model.
Tuberculosis (TB), the leading killer of young adults worldwide, newly affects one person every second and kills one in every 15 seconds. The recent increase of TB in developing countries has been exacerbated by many causes including pandemic HIV, war and political instability, drug resistance, and increasing poverty. Genetic immunization has emerged with tremendous potential in vaccination against TB with success in animal models with naked DNA encoding different genes such as Ag85A, Pst3, and hsp65. However, there are shortcomings in translating this success into reality in human clinical trials due to limitations at the level of delivery, quality, and quantity of DNA to be administered, which can be circumvented by using an attenuated bacteria delivery system for transgene vaccination for mucosal immunization targeting the inductive sites of the immune system. We compare this novel delivery system using an attenuated Salmonella delta aroA strain through a mucosal route with classic intramuscular DNA delivery using a potential protective antigen, Ag85A, of Mycobacterium tuberculosis in a mouse infection virulent challenge model. We show an immune response and superior protection in the mice at the level of the lungs as well as the spleen against a virulent challenge after intranasal immunization by recombinant Salmonella typhimurium carrying a eukaryotic expression plasmid encoding Ag85A rather than the classic DNA immunization and at par with the protection conferred by BCG. This study establishes the proof of principle of this system for further exploitation of this platform for vaccine development, which is being pursued for postexposure vaccine development for TB.
Acyltransferases↗
Histamine scavenging attenuates endotoxin-induced acute lung injury.
Histamine is an important mediator of early and late inflammatory responses. Here we asked whether scavenging of endogenous histamine by the arthropod-derived histamine binding protein EV131 diminishes acute respiratory distress syndrome (ARDS) induced by inhaled endotoxin. We demonstrate that EV131 (360 microg given intranasally) reduced endotoxin-induced bronchoconstriction and recruitment of neutrophils. Furthermore, EV131 administration diminished TNF-alpha and protein leak in the bronchoalveolar lavage fluid. The data suggest that histamine attenuates endotoxin-induced bronchoconstriction and neutrophil recruitment. Therefore, scavenging of histamine by EV131 may represent a novel therapeutic strategy in ARDS.
Airway Resistance↗
Arthropod-derived histamine-binding protein prevents murine allergic asthma.
Because histamine receptor type I blockade attenuates allergic asthma, we asked whether complete neutralization of histamine by an arthropod-derived, high affinity histamine-binding protein (EV131) would prevent allergic asthma. Intranasal administration of EV131 given before Ag challenge in immunized mice prevented airway hyperreactivity by 70%, and abrogated peribronchial inflammation, pulmonary eosinophilia, mucus hypersecretion, and IL-4 and IL-5 secretion. Saturation with histamine abrogated the inhibitory effect of EV131 on bronchial hyperreactivity. The inhibitory effect of EV131 on bronchial hyperreactivity was comparable to that of glucocorticosteroids. These results demonstrate that histamine is a critical mediator of allergic asthma. Therefore, complete neutralization of histamine, rather than specific histamine receptor blockade, may have a profound effect on allergic asthma.
Animals↗
NK cell activation by dendritic cells (DCs) requires the formation of a synapse leading to IL-12 polarization in DCs.
Mature dendritic cells (mDCs) can trigger the effector functions of natural killer (NK) cells. Knock-out, small-interfering RNA or neutralizing antibodies targeting interleukin 12 (IL-12) subunits revealed a critical role for IL-12 in NK cell interferon gamma (IFN-gamma) secretion promoted by mDCs. However, NK cell activation by DCs also required direct cell-to-cell contacts. DC-mediated NK cell activation involved the formation of stimulatory synapses between DCs and NK cells. The formation of DC/NK cell conjugates depended on cytoskeleton remodeling and lipid raft mobilization in DCs. Moreover, the disruption of the DC cytoskeleton using pharmacologic agents or the loss-of-function mutation of the Wiskott-Aldrich syndrome protein abolished the DC-mediated NK cell activation. Synapse formation promoted the polarized secretion of preassembled stores of IL-12 by DCs toward the NK cell. The synaptic delivery of IL-12 by DCs was required for IFN-gamma secretion by NK cells, as assessed using inhibitors of cytoskeleton rearrangements and transwell experiments. Therefore, the cross-talk between DCs and NK cells is dictated by functional synapses.
Animals↗
Toll-like receptor 2 (TLR2)-dependent-positive and TLR2-independent-negative regulation of proinflammatory cytokines by mycobacterial lipomannans.
Lipoarabinomannans (LAM) and lipomannans (LM) are integral parts of the mycobacterial cell wall recognized by cells involved in the innate immune response and have been found to modulate the cytokine response. Typically, mannosylated LAM from pathogenic mycobacteria have been reported to be anti-inflammatory, whereas phosphoinositol-substituted LAM from nonpathogenic species are proinflammatory molecules. In this study, we show that LM from several mycobacterial species, including Mycobacterium chelonae, Mycobacterium kansasii, and Mycobacterium bovis bacillus Calmette-Guérin, display a dual function by stimulating or inhibiting proinflammatory cytokine synthesis through different pathways in murine primary macrophages. LM, but none of the corresponding LAM, induce macrophage activation characterized by cell surface expression of CD40 and CD86 and by TNF and NO secretion. This activation is dependent on the presence of Toll-like receptor (TLR) 2 and mediated through the adaptor protein myeloid differentiation factor 88 (MyD88), but independent of either TLR4 or TLR6 recognition. Surprisingly, LM exerted also a potent inhibitory effect on TNF, IL-12p40, and NO production by LPS-activated macrophages. This TLR2-, TLR6-, and MyD88-independent inhibitory effect is also mediated by LAM from M. bovis bacillus Calmette-Guérin but not by LAM derived from M. chelonae and M. kansasii. This study provides evidence that mycobacterial LM bear structural motifs susceptible to interact with different pattern recognition receptors with pro- or anti-inflammatory effects. Thus, the ultimate response of the host may therefore depend on the prevailing LM or LAM in the mycobacterial envelope and the local host cell receptor availability.
Adaptor Proteins, Signal Transducing↗
Toll-like receptor pathways in the immune responses to mycobacteria.
The control of Mycobacterium tuberculosis infection depends on recognition of the pathogen and the activation of both the innate and adaptive immune responses. Toll-like receptors (TLR) were shown to play a critical role in the recognition of several pathogens. Mycobacterial antigens recognise distinct TLR resulting in rapid activation of cells of the innate immune system. Recent evidence from in vitro and in vivo investigations, summarised in this review demonstrates TLR-dependent activation of innate immune response, while the induction of adaptive immunity to mycobacteria may be TLR independent.
Animals↗
Toll-like receptor 2-deficient mice succumb to Mycobacterium tuberculosis infection.
Recognition of Mycobacterium tuberculosis by the innate immune system is essential in the development of an adaptive immune response. Mycobacterial cell wall components activate macrophages through Toll-like receptor (TLR) 2, suggesting that this innate immune receptor plays a role in the host response to M. tuberculosis infection. After aerosol infection with either 100 or 500 live mycobacteria, TLR2-deficient mice display reduced bacterial clearance, a defective granulomatous response, and develop chronic pneumonia. Analysis of pulmonary immune responses in TLR2-deficient mice after 500 mycobacterial aerosol challenge showed increased levels of interferon-gamma, tumor necrosis factor-alpha, and interleukin-12p40 as well as increased numbers of CD4(+) and CD8(+) cells. Furthermore, TLR2-deficient mice mounted elevated Ag-specific type 1 T-cell responses that were not protective because all deficient mice succumb to infection within 5 months. Taken together, the data suggests that TLR2 may function as a regulator of inflammation, and in its absence an exaggerated immune inflammatory response develops.
Animals↗
Chronic pneumonia despite adaptive immune response to Mycobacterium bovis BCG in MyD88-deficient mice.
To assess the role of Toll-like receptor (TLR) signalling in host response to mycobacterial infection, mice deficient in the TLR adaptor molecule myeloid differentiation factor 88 (MyD88) were infected with the vaccine strain Mycobacterium bovis (BCG), and the immune response and bacterial burden were investigated. Macrophages and dendritic cells from MyD88-deficient mice stimulated in vitro with BCG mycobacterial antigens produced very low levels of proinflammatory cytokines, while the expression of costimulatory molecules such as CD40 and CD86 was preserved. Upon systemic infection with BCG (2 x 10(6) CFU i.v.) MyD88-deficient mice developed confluent chronic pneumonia with two log higher CFU than wild-type mice. Interestingly, the infection was controlled in liver and spleen and there was efficient systemic T-cell priming with high IFNgamma production by CD4+ splenic T cells in MyD88-deficient mice. Lung infiltrating cells showed IFNgamma production by pulmonary CD4+ T cells upon specific restimulation, and a reduced capacity to produce nitric oxide and IL-10. In summary, despite the dramatic reduction of the innate immune response, MyD88-deficient mice were able to mount an efficient T-cell response to mycobacterial antigens, which was however insufficient to control infection in the lung, resulting in chronic pneumonia in MyD88-deficient mice.
Adaptor Proteins, Signal Transducing↗
Long-term control of Mycobacterium bovis BCG infection in the absence of Toll-like receptors (TLRs): investigation of TLR2-, TLR6-, or TLR2-TLR4-deficient mice.
Live mycobacteria have been reported to signal through both Toll-like receptor 2 (TLR2) and TLR4 in vitro. Here, we investigated the role of TLR2 in the long-term control of the infection by the attenuated Mycobacterium, Mycobacterium bovis BCG, in vivo. We sought to determine whether the reported initial defect of bacterial control (K. A. Heldwein et al., J. Leukoc. Biol. 74:277-286, 2003) resolved in the chronic phase of BCG infection. Here we show that TLR2-deficient mice survived a 6-month infection period with M. bovis BCG and were able to control bacterial growth. Granuloma formation, T-cell and macrophage recruitment, and activation were normal. Furthermore, the TLR2 coreceptor, TLR6, is also not required since TLR6-deficient mice were able to control chronic BCG infection. Finally, TLR2-TLR4-deficient mice infected with BCG survived the 8-month observation period. Interestingly, the adaptive response of TLR2- and/or TLR4-deficient mice seemed essentially normal on day 14 or 56 after infection, since T cells responded normally to soluble BCG antigens. In conclusion, our data demonstrate that TLR2, TLR4, or TLR6 are redundant for the control of M. bovis BCG mycobacterial infection.
Animals↗
Toll-like receptor 2 is required for optimal control of Listeria monocytogenes infection.
The control of Listeria monocytogenes infection depends on the rapid activation of the innate immune system, likely through Toll-like receptors (TLR), since mice deficient for the common adapter protein of TLR signaling, myeloid differentiation factor 88 (MyD88), succumb to Listeria infection. In order to test whether TLR2 is involved in the control of infections, we compared the host response in TLR2-deficient mice with that in wild-type mice. Here we show that TLR2-deficient mice are more susceptible to systemic infection by Listeria than are wild-type mice, with a reduced survival rate, increased bacterial burden in the liver, and abundant and larger hepatic microabscesses containing increased numbers of neutrophils. The production of tumor necrosis factor, interleukin-12, and nitric oxide and the expression of the costimulatory molecules CD40 and CD86, which are necessary for the control of infection, were reduced in TLR2-deficient macrophages and dendritic cells stimulated by Listeria and were almost abolished in the absence of MyD88, coincident with the high susceptibility of MyD88-deficient mice to in vivo infection. Therefore, the present data demonstrate a role for TLR2 in the control of Listeria infection, but other MyD88-dependent signals may contribute to host resistance.
Adaptor Proteins, Signal Transducing↗
Fatal Mycobacterium tuberculosis infection despite adaptive immune response in the absence of MyD88.
Toll-like receptors (TLRs) such as TLR2 and TLR4 have been implicated in host response to mycobacterial infection. Here, mice deficient in the TLR adaptor molecule myeloid differentiation factor 88 (MyD88) were infected with Mycobacterium tuberculosis (MTB). While primary MyD88(-/-) macrophages and DCs are defective in TNF, IL-12, and NO production in response to mycobacterial stimulation, the upregulation of costimulatory molecules CD40 and CD86 is unaffected. Aerogenic infection of MyD88(-/-) mice with MTB is lethal within 4 weeks with 2 log(10) higher CFU in the lung; high pulmonary levels of cytokines and chemokines; and acute, necrotic pneumonia, despite a normal T cell response with IFN-gamma production to mycobacterial antigens upon ex vivo restimulation. Vaccination with Mycobacterium bovis bacillus Calmette-Guerin conferred a substantial protection in MyD88(-/-) mice from acute MTB infection. These data demonstrate that MyD88 signaling is dispensable to raise an acquired immune response to MTB. Nonetheless, this acquired immune response is not sufficient to compensate for the profound innate immune defect and the inability of MyD88(-/-) mice to control MTB infection.
Adaptor Proteins, Signal Transducing↗
Reactivation of latent tuberculosis infection in TNF-deficient mice.
TNF-deficient mice are highly susceptible to Mycobacterium tuberculosis H37Rv infection. Here we asked whether TNF is required for postinfectious immunity in aerosol-infected mice. Chemotherapy for 4 wk commencing 2 wk postinfection reduced CFU to undetectable levels. While wild-type mice had a slight rise in CFU, but controlled infection upon cessation of chemotherapy, TNF-deficient mice developed reactivation of infection with high bacterial loads in lungs, spleen, and liver, which was fatal within 13-18 wk. The increased susceptibility of TNF-deficient mice was accompanied by diminished recruitment and activation of T cells and macrophages into the lung, with defective granuloma formation and reduced inducible NO synthase expression. Reduced chemokine production in the lung might explain suboptimal recruitment and activation of T cells and uncontrolled infection. Therefore, despite a massive reduction of the mycobacterial load by chemotherapy, TNF-deficient mice were unable to compensate and mount a protective immune response. In conclusion, endogenous TNF is critical to maintain latent tuberculosis infection, and in its absence no specific immunity is generated.
Animals↗
Overexpression of Toll-like receptor 4 amplifies the host response to lipopolysaccharide and provides a survival advantage in transgenic mice.
Toll-like receptors are transmembrane proteins that are involved in the innate immune recognition of microbial constituents. Among them, Toll-like receptor 4 (Tlr4) is a crucial signal transducer for LPS, the major component of Gram-negative bacteria outer cell membrane. The contribution of Tlr4 to the host response to LPS and to infection with virulent Salmonella typhimurium was studied in four transgenic (Tg) strains including three overexpressing Tlr4. There was a good correlation between the level of Tlr4 mRNA expression and the sensitivity to LPS both in vitro and in vivo: Tg mice possessing the highest number of Tlr4 copies respond the most to LPS. Overexpression of Tlr4 by itself appears to have a survival advantage in Tg mice early during infection: animals possessing more than two copies of the gene survived longer and in a greater percentage to Salmonella infection. The beneficial effect of Tlr4 overexpression is greatly enhanced when the mice present a wild-type allele at natural resistance-associated macrophage protein 1, another critical innate immune gene involved in resistance to infection with Salmonella. Tlr4 and natural resistance-associated macrophage protein 1 exhibit functional epistatic interaction to improve the capacity of the host to control bacterial replication. However, this early improvement in disease resistance is not conducted later during infection, because mice overexpressing Tlr4 developed an excessive inflammatory response detrimental to the host.
Adjuvants, Immunologic↗
Oral artesunate prevents Plasmodium berghei Anka infection in mice.
Artesunate, a semi-synthetic derivative of a naturally occurring anti-malarial artemisinin was compared with chloroquine in C57BL/6 mice infected with Plasmodium berghei Anka (PbA). A 7-day oral administration of artesunate prevented parasitaemia at 10 mg/kg/day. However, recrudescence of parasitaemia and cerebral malaria occurred upon cessation of treatment followed by death within 28 days. However, a 14-day course of artesunate (100 mg/kg/day) prevented completely the development of parasitaemia and cerebral malaria with a survival of more than 60-days as did 10 mg/kg/day chloroquine. These data demonstrate that oral artesunate inhibits PbA and prevents cerebral malaria, but needs to be administered at high dose and for prolonged time to eradicate PbA infection in mice.
Administration, Oral↗
Toll-like receptor 4 expression is required to control chronic Mycobacterium tuberculosis infection in mice.
Endotoxin from Gram-negative bacteria bound to CD14 signals through Toll-like receptor (TLR) 4, while components of Gram-positive bacteria, fungi, and Mycobacterium tuberculosis (M.tb.) preferentially use TLR2 signaling. We asked whether TLR4 plays any role in host resistance to M.tb. infection in vivo. Therefore, we infected the TLR4 mutant C3H/HeJ mice and their controls, C3H/HeN mice, with M.tb. by aerosol. TLR4 mutant mice had a reduced capacity to eliminate mycobacteria from the lungs, spread the infection to spleen and liver, with 10-100 times higher CFU organ levels than the wild-type mice and succumbed within 5-7 mo, whereas most of the wild-type mice controlled infection and survived the duration of the experiment. The lungs of TLR4 mutant mice showed chronic pneumonia with increased neutrophil infiltration, reduced macrophages recruitment, and abundant acid-fast bacilli. Furthermore, the pulmonary expression of TNF-alpha, IL-12p40, and monocyte chemoattractant protein 1 was significantly lower in C3H/HeJ mice when compared with the wild-type controls. C3H/HeJ-derived macrophages infected in vitro with M.tb. produced lower levels of TNF-alpha. Finally, the purified mycobacterial glycolipid, phosphatidylinositol mannosides, induced signaling in both a TLR2- and TLR4-dependent manner, thus suggesting that recognition of phosphatidylinositol mannosides in vivo may influence the development of protective immunity. In summary, macrophage recruitment and the proinflammatory response to M.tb. are impaired in TLR4 mutant mice, resulting in chronic infection with impaired elimination of mycobacteria. Therefore, TLR4 signaling is required to mount a protective response during chronic M.tb. infection.
Animals↗