RESUMEN
Circulating inflammatory monocytes are attracted to infected mucosa and differentiate into macrophage or dendritic cells endowed with enhanced bactericidal and antigen presenting capacities. In this brief Perspective we discuss the newly emerging insight into how the cAMP signaling capacity of Bordetella pertussis adenylate cyclase toxin manipulates the differentiation of monocytes and trigger dedifferentiation of the alveolar macrophages to facilitate bacterial colonization of human airways.
Asunto(s)
Toxina de Adenilato Ciclasa/fisiología , Bordetella pertussis/fisiología , Macrófagos Alveolares/efectos de los fármacos , Monocitos/efectos de los fármacos , Toxina de Adenilato Ciclasa/farmacología , Animales , Presentación de Antígeno/efectos de los fármacos , Desdiferenciación Celular/efectos de los fármacos , Diferenciación Celular , AMP Cíclico/fisiología , Interacciones Huésped-Patógeno/inmunología , Humanos , Inmunidad Innata/efectos de los fármacos , Inmunidad Mucosa/efectos de los fármacos , Macrófagos Alveolares/citología , Ratones , Modelos Biológicos , Monocitos/citología , Fagocitosis , Sistema Respiratorio/efectos de los fármacos , Sistema Respiratorio/inmunología , Sistema Respiratorio/microbiología , Sistemas de Mensajero Secundario/efectos de los fármacos , Sistemas de Mensajero Secundario/fisiologíaRESUMEN
Once translocated into the cytosol of target cells, the catalytic domain (AC) of the adenylate cyclase toxin (CyaA), a major virulence factor of Bordetella pertussis, is potently activated by binding calmodulin (CaM) to produce supraphysiological levels of cAMP, inducing cell death. Using a combination of small-angle X-ray scattering (SAXS), hydrogen/deuterium exchange mass spectrometry (HDX-MS), and synchrotron radiation circular dichroism (SR-CD), we show that, in the absence of CaM, AC exhibits significant structural disorder, and a 75-residue-long stretch within AC undergoes a disorder-to-order transition upon CaM binding. Beyond this local folding, CaM binding induces long-range allosteric effects that stabilize the distant catalytic site, whilst preserving catalytic loop flexibility. We propose that the high enzymatic activity of AC is due to a tight balance between the CaM-induced decrease of structural flexibility around the catalytic site and the preservation of catalytic loop flexibility, allowing for fast substrate binding and product release. The CaM-induced dampening of AC conformational disorder is likely relevant to other CaM-activated enzymes.
Asunto(s)
Toxina de Adenilato Ciclasa/química , Bordetella pertussis/química , Calmodulina/química , Toxina de Adenilato Ciclasa/metabolismo , Toxina de Adenilato Ciclasa/fisiología , Bordetella pertussis/patogenicidad , Señalización del Calcio , Calmodulina/metabolismo , Calmodulina/fisiología , Catálisis , Dominio Catalítico , Dicroismo Circular , AMP Cíclico/metabolismo , Medición de Intercambio de Deuterio , Espectrometría de Masas , Modelos Moleculares , Unión Proteica , Conformación Proteica , Dispersión del Ángulo Pequeño , SincrotronesRESUMEN
The adenylate cyclase toxin-hemolysin (CyaA) plays a key role in immune evasion and virulence of the whooping cough agent Bordetella pertussis. CyaA penetrates the complement receptor 3-expressing phagocytes and ablates their bactericidal capacities by catalyzing unregulated conversion of cytosolic ATP to the key second messenger molecule cAMP. We show that signaling of CyaA-generated cAMP blocks the oxidative burst capacity of neutrophils by two converging mechanisms. One involves cAMP/protein kinase A-mediated activation of the Src homology region 2 domain-containing phosphatase-1 (SHP-1) and limits the activation of MAPK ERK and p38 that are required for assembly of the NADPH oxidase complex. In parallel, activation of the exchange protein directly activated by cAMP (Epac) provokes inhibition of the phospholipase C by an as yet unknown mechanism. Indeed, selective activation of Epac by the cell-permeable analog 8-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate counteracted the direct activation of phospholipase C by 2,4,6-trimethyl-N-[3-(trifluoromethyl)phenyl]benzenesulfonamide. Hence, by inhibiting production of the protein kinase C-activating lipid, diacylglycerol, cAMP/Epac signaling blocks the bottleneck step of the converging pathways of oxidative burst triggering. Manipulation of neutrophil membrane composition by CyaA-produced signaling of cAMP thus enables B. pertussis to evade the key innate host defense mechanism of reactive oxygen species-mediated killing of bacteria by neutrophils.
Asunto(s)
Toxina de Adenilato Ciclasa/fisiología , AMP Cíclico/fisiología , Factores de Intercambio de Guanina Nucleótido/fisiología , Neutrófilos/fisiología , Estallido Respiratorio , Transducción de Señal/fisiología , Fosfolipasas de Tipo C/antagonistas & inhibidores , Bordetella pertussis/inmunología , Quinasas MAP Reguladas por Señal Extracelular/fisiología , Humanos , Fosfatidilinositol 3-Quinasas/fisiología , Proteína Quinasa C/fisiología , Especies Reactivas de Oxígeno/metabolismo , Fosfolipasas de Tipo C/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/fisiologíaRESUMEN
Inflammasome-mediated IL-1beta production is central to the innate immune defects that give rise to certain autoinflammatory diseases and may also be associated with the generation of IL-17-producing CD4(+) T (Th17) cells that mediate autoimmunity. However, the role of the inflammasome in driving adaptive immunity to infection has not been addressed. In this article, we demonstrate that inflammasome-mediated IL-1beta plays a critical role in promoting Ag-specific Th17 cells and in generating protective immunity against Bordetella pertussis infection. Using a murine respiratory challenge model, we demonstrated that the course of B. pertussis infection was significantly exacerbated in IL-1R type I-defective (IL-1RI(-/-)) mice. We found that adenylate cyclase toxin (CyaA), a key virulence factor secreted by B. pertussis, induced robust IL-1beta production by dendritic cells through activation of caspase-1 and the NALP3-containing inflammasome complex. Using mutant toxins, we demonstrate that CyaA-mediated activation of caspase-1 was not dependent on adenylate cyclase enzyme activity but was dependent on the pore-forming capacity of CyaA. In addition, CyaA promoted the induction of Ag-specific Th17 cells in wild-type but not IL-1RI(-/-) mice. Furthermore, the bacterial load was enhanced in IL-17-defective mice. Our findings demonstrate that CyaA, a virulence factor from B. pertussis, promotes innate IL-1beta production via activation of the NALP3 inflammasome and, thereby, polarizes T cell responses toward the Th17 subtype. In addition to its known role in subverting host immunity, our findings suggest that CyaA can promote IL-1beta-mediated Th17 cells, which promote clearance of the bacteria from the respiratory tract.
Asunto(s)
Toxina de Adenilato Ciclasa/fisiología , Bordetella pertussis/inmunología , Linfocitos T CD4-Positivos/inmunología , Mediadores de Inflamación/metabolismo , Interleucina-17/biosíntesis , Infecciones del Sistema Respiratorio/prevención & control , Toxina de Adenilato Ciclasa/toxicidad , Animales , Linfocitos T CD4-Positivos/enzimología , Linfocitos T CD4-Positivos/microbiología , Proteínas Portadoras/metabolismo , Caspasa 1/metabolismo , Polaridad Celular/inmunología , Células Cultivadas , Epítopos de Linfocito T/inmunología , Inflamación/enzimología , Inflamación/microbiología , Inflamación/prevención & control , Mediadores de Inflamación/fisiología , Interleucina-17/deficiencia , Interleucina-17/fisiología , Interleucina-1beta/biosíntesis , Interleucina-1beta/fisiología , Intubación Intratraqueal , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína con Dominio Pirina 3 de la Familia NLR , Infecciones del Sistema Respiratorio/enzimología , Infecciones del Sistema Respiratorio/microbiología , Infecciones del Sistema Respiratorio/patologíaRESUMEN
The complex pathology of B. pertussis infection is due to multiple virulence factors having disparate effects on different cell types. We focused our investigation on the ability of B. pertussis to modulate host immunity, in particular on the role played by adenylate cyclase toxin (CyaA), an important virulence factor of B. pertussis. As a tool, we used human monocyte derived dendritic cells (MDDC), an ex vivo model useful for the evaluation of the regulatory potential of DC on T cell immune responses. The work compared MDDC functions after encounter with wild-type B. pertussis (BpWT) or a mutant lacking CyaA (BpCyaA-), or the BpCyaA- strain supplemented with either the fully functional CyaA or a derivative, CyaA*, lacking adenylate cyclase activity. As a first step, MDDC maturation, cytokine production, and modulation of T helper cell polarization were evaluated. As a second step, engagement of Toll-like receptors (TLR) 2 and TLR4 by B. pertussis and the signaling events connected to this were analyzed. These approaches allowed us to demonstrate that CyaA expressed by B. pertussis strongly interferes with DC functions, by reducing the expression of phenotypic markers and immunomodulatory cytokines, and blocking IL-12p70 production. B. pertussis-treated MDDC promoted a mixed Th1/Th17 polarization, and the activity of CyaA altered the Th1/Th17 balance, enhancing Th17 and limiting Th1 expansion. We also demonstrated that Th1 effectors are induced by B. pertussis-MDDC in the absence of IL-12p70 through an ERK1/2 dependent mechanism, and that p38 MAPK is essential for MDDC-driven Th17 expansion. The data suggest that CyaA mediates an escape strategy for the bacterium, since it reduces Th1 immunity and increases Th17 responses thought to be responsible, when the response is exacerbated, for enhanced lung inflammation and injury.
Asunto(s)
Toxina de Adenilato Ciclasa/metabolismo , Bordetella pertussis/fisiología , Células Dendríticas/inmunología , Sistema de Señalización de MAP Quinasas , Linfocitos T Colaboradores-Inductores/inmunología , Toxina de Adenilato Ciclasa/fisiología , Citocinas/biosíntesis , Humanos , Fosfatidilinositol 3-Quinasas/metabolismoRESUMEN
The adenylate cyclase toxin (CyaA) released by Bordetella pertussis is an essential virulence factor for colonization of the host. This toxin inhibits migration and activation of phagocytes, thereby preventing bacterial killing. In addition, CyaA interferes with the initiation of adaptive immunity by misdirecting dendritic cell differentiation to a suppressive rather than stimulatory phenotype. Here we show that CyaA directly affects adaptive responses by catalyzing cyclic AMP (cAMP) production in peripheral blood lymphocytes. Treatment with CyaA resulted in profound impairment of T-lymphocyte activation and chemotaxis. These effects resulted from inhibition of T-cell antigen receptor and chemokine receptor signaling via a cAMP/protein kinase A (PKA)-dependent pathway. A comparison of the activities of CyaA on T-cell and macrophage activation and migration revealed that the biological effects of the toxin were paralleled by inhibition of the activation of mitogen-activated protein (MAP) kinases, highlighting the conclusion that the ubiquitous and evolutionarily conserved MAP kinase modules are common targets of the PKA-mediated immunosuppressant activities of CyaA and underlining the potential of cAMP-elevating toxins as a means of evasion of immunity by bacterial pathogens.
Asunto(s)
Toxina de Adenilato Ciclasa/toxicidad , Bordetella pertussis/patogenicidad , Quimiotaxis de Leucocito , Activación de Linfocitos , Linfocitos T/inmunología , Factores de Virulencia de Bordetella/toxicidad , Toxina de Adenilato Ciclasa/genética , Toxina de Adenilato Ciclasa/fisiología , Bordetella pertussis/metabolismo , Inhibición de Migración Celular , AMP Cíclico/biosíntesis , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Activación Enzimática , HumanosRESUMEN
Strains of Enterobacter cloacae show promise as biological control agents for Pythium ultimum-induced damping-off on cucumber and other crops. Enterobacter cloacae M59 is a mini-Tn5 Km transposon mutant of strain 501R3. Populations of M59 were significantly lower on cucumber roots and decreased much more rapidly than those of strain 501R3 with increasing distance from the soil line. Strain M59 was decreased or deficient in growth and chemotaxis on most individual compounds detected in cucumber root exudate and on a synthetic cucumber root exudate medium. Strain M59 was also slightly less acid resistant than strain 501R3. Molecular characterization of strain M59 demonstrated that mini-Tn5 Km was inserted in cyaA, which encodes adenylate cyclase. Adenylate cyclase catalyzes the formation of cAMP and cAMP levels in cell lysates from strain M59 were approximately 2% those of strain 501R3. Addition of exogenous, nonphysiological concentrations of cAMP to strain M59 restored growth (1 mM) and chemotaxis (5 mM) on synthetic cucumber root exudate and increased cucumber seedling colonization (5 mM) by this strain without serving as a source of reduced carbon, nitrogen, or phosphorous. These results demonstrate a role for cyaA in colonization of cucumber roots by Enterobacter cloacae.
Asunto(s)
Toxina de Adenilato Ciclasa/fisiología , Cucumis sativus/microbiología , Enterobacter cloacae/patogenicidad , Control Biológico de Vectores , Raíces de Plantas/microbiología , Toxina de Adenilato Ciclasa/genética , Toxina de Adenilato Ciclasa/metabolismo , Cucumis sativus/genética , Enterobacter cloacae/genética , Genes Bacterianos , Mutación , Enfermedades de las PlantasRESUMEN
Recombinant, genetically-detoxified adenylate cyclase toxin (CyaA) constructs from Bordetella pertussis have been developed as potential antigen delivery systems and as promising antigen candidates for inclusion in acellular pertussis vaccines. The major toxic effects of native CyaA are attributed to its enzymatic activity following delivery to cells of the innate immune system via the CD11b/CD18 (CR3) cell receptor. In view of the potential use of detoxified CyaA in vaccinology, a complement dependent in vitro model was used to investigate the potential effects of the interaction of detoxified CyaA with CD11b/CD18 (CR3) on phagocytic function. Interaction of CyaA with CD11b/CD18 (CR3) on human pro-myelocytic NB-4 cells differentiated to a neutrophil-like phenotype was measured as inhibition of binding of a monoclonal antibody to the receptor. This interaction was dose-dependent and required acylation of CyaA. Treatment of the cells with either acylated or non-acylated detoxified CyaA constructs inhibited their phagocytic function. Washing the cells allowed recovery of phagocytic function after treatment with non-acylated toxin but not for cells treated with acylated CyaA constructs. However, availability of CD11b/CD18 receptors on acylated CyaA-treated cells was restored after washing and further incubation. The results suggest that the interaction of detoxified CyaA constructs to the CD11b/CD18 (CR3) receptor may temporarily influence the complement-dependent phagocytic function in neutrophil leukocytes.
Asunto(s)
Toxina de Adenilato Ciclasa/inmunología , Proteínas del Sistema Complemento/fisiología , Vacuna contra la Tos Ferina/inmunología , Fagocitosis , Toxina de Adenilato Ciclasa/genética , Toxina de Adenilato Ciclasa/fisiología , Línea Celular , Supervivencia Celular , Humanos , Antígeno de Macrófago-1/fisiología , Neutrófilos/inmunología , Streptococcus pneumoniae/inmunologíaRESUMEN
Bordetella pertussis, the causative agent of whooping cough, possesses an array of virulence factors, including adenylate cyclase toxin (ACT), relevant in the establishment of infection. Here we better define the impact of cyclic AMP (cAMP) intoxication due to the action of ACT on dendritic cell (DC)-driven immune response, by infecting monocyte-derived DC (MDDC) with an ACT-deficient B. pertussis mutant (ACT- 18HS19) or its parental strain (WT18323). Both strains induced MDDC maturation and antigen-presenting cell functions; however, only ACT- 18HS19 infected MDDC-induced production of interleukin-12 (IL-12) p70. Gene expression analysis of the IL-12 cytokine family subunits revealed that both strains induced high levels of p40 (protein chain communal to IL-12 p70 and IL-23) as well as p19, a subunit of IL-23. Conversely only ACT- 18HS19 infection induced consistent transcription of IL-12 p35, a subunit of IL-12 p70. Addition of the cAMP analogous D-butyril-cAMP (D-cAMP) abolished IL-12 p70 production and IL-12 p35 expression in ACT- 18HS19-infected MDDC. ACT- 18HS19 infection induced the expression of the transcription factors interferon regulatory factor 1 (IRF-1) and IRF-8 and of beta interferon, involved in IL-12 p35 regulation, and the expression of these genes was inhibited by D-cAMP addition and in WT18323-infected MDDC. The concomitant expression of IL-12 p70 and IL-23 allowed ACT- 18HS19 to trigger a more pronounced T helper 1 polarization compared to WT18323. The present study suggests that ACT-dependent cAMP induction leads to the inhibition of pathways ultimately leading to IL-12 p35 production, thus representing a mechanism for B. pertussis to escape the host immune response.
Asunto(s)
Toxina de Adenilato Ciclasa/fisiología , Bordetella pertussis/patogenicidad , AMP Cíclico/biosíntesis , Células Dendríticas/metabolismo , Interleucina-12/antagonistas & inhibidores , Monocitos/citología , Subunidades de Proteína/antagonistas & inhibidores , Polaridad Celular , Células Cultivadas , Humanos , Factor 1 Regulador del Interferón/genética , Factores Reguladores del Interferón/genética , Interferón beta/genética , Subunidad p35 de la Interleucina-12 , Células TH1/fisiologíaRESUMEN
The adenylate cyclase toxin (CyaA) is one of the major virulence factors of Bordetella pertussis, the causative agent of whooping cough. CyaA is able to invade eukaryotic cells by a unique mechanism that consists in a calcium-dependent, direct translocation of the CyaA catalytic domain across the plasma membrane of the target cells. CyaA possesses a series of a glycine- and aspartate-rich nonapeptide repeats (residues 1006-1613) of the prototype GGXG(N/D)DX(L/I/F)X (where X represents any amino acid) that are characteristic of the RTX (repeat in toxin) family of bacterial cytolysins. These repeats are arranged in a tandem fashion and may fold into a characteristic parallel beta-helix or beta-roll motif that constitutes a novel type of calcium binding structure, as revealed by the three-dimensional structure of the Pseudomonas aeruginosa alkaline protease. Here we have characterized the structure-function relationships of various fragments from the CyaA RTX subdomain. Our results indicate that the RTX functional unit includes both the tandem repeated nonapeptide motifs and the adjacent polypeptide segments, which are essential for the folding and calcium responsiveness of the RTX module. Upon calcium binding to the RTX repeats, a conformational rearrangement of the adjacent non-RTX sequences may act as a critical molecular switch to trigger the CyaA entry into target cells.
Asunto(s)
Toxina de Adenilato Ciclasa/química , Bordetella pertussis/metabolismo , Toxina de Adenilato Ciclasa/fisiología , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Ácido Aspártico/química , Proteínas Bacterianas/química , Membrana Celular/metabolismo , Endopeptidasas/química , Escherichia coli/metabolismo , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Pseudomonas aeruginosa/enzimología , Homología de Secuencia de Aminoácido , Relación Estructura-ActividadRESUMEN
Adenylate cyclase toxin (CyaA) of Bordetella pertussis belongs to the repeat in toxin family of pore-forming toxins, which require posttranslational acylation to lyse eukaryotic cells. CyaA modulates dendritic cell (DC) and macrophage function upon stimulation with LPS. In this study, we examined the roles of acylation and enzymatic activity in the immunomodulatory and lytic effects of CyaA. The adenylate cyclase activity of CyaA was necessary for its modulatory effects on murine innate immune cells. In contrast, acylation was not essential for the immunomodulatory function of CyaA, but was required for maximal caspase-3 activation and cytotoxic activity. The wild-type acylated toxin (A-CyaA) and nonacylated CyaA (NA-CyaA), but not CyaA with an inactive adenylate cyclase domain (iAC-CyaA), enhanced TLR-ligand-induced IL-10 and inhibited IL-12, TNF-alpha, and CCL3 production by macrophages and DC. In addition, both A-CyaA and NA-CyaA, but not iAC-CyaA, enhanced surface expression of CD80 and decreased CpG-stimulated CD40 and ICAM-1 expression on immature DC. Furthermore, both A-CyaA and NA-CyaA promoted the induction of murine IgG1 Abs, Th2, and regulatory T cells against coadministered Ags in vivo, whereas iAC-CyaA had more limited adjuvant activity. In contrast, A-CyaA and iAC-CyaA induced caspase-3 activation and cell death in macrophages, but these effects were considerably reduced or absent with NA-CyaA. Our findings demonstrate that the enzymatic activity plays a critical role in the immunomodulatory effects of CyaA, whereas acylation facilitates the induction of apoptosis and cell lysis, and as such, NA-CyaA has considerable potential as a nontoxic therapeutic molecule with potent anti-inflammatory properties.
Asunto(s)
Toxina de Adenilato Ciclasa/química , Toxina de Adenilato Ciclasa/fisiología , Adyuvantes Inmunológicos/química , Adyuvantes Inmunológicos/fisiología , Bordetella pertussis/enzimología , Bordetella pertussis/inmunología , Inmunidad Activa , Inmunidad Innata , Acilación , Toxina de Adenilato Ciclasa/antagonistas & inhibidores , Toxina de Adenilato Ciclasa/aislamiento & purificación , Adyuvantes Inmunológicos/antagonistas & inhibidores , Adyuvantes Inmunológicos/aislamiento & purificación , Animales , Antígeno CD11b/fisiología , Caspasa 3 , Caspasas/metabolismo , Muerte Celular/inmunología , Diferenciación Celular/inmunología , Línea Celular , Células Cultivadas , AMP Cíclico/química , Citocinas/metabolismo , Pruebas Inmunológicas de Citotoxicidad , Proteínas de Unión al ADN/fisiología , Células Dendríticas/citología , Células Dendríticas/inmunología , Activación Enzimática/inmunología , Femenino , Macrófagos/citología , Macrófagos/inmunología , Macrófagos/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C3H , Oligodesoxirribonucleótidos/química , Receptores de Superficie Celular/fisiología , Transducción de Señal/inmunología , Receptor Toll-Like 9RESUMEN
Bordetella bronchiseptica utilizes a type III secretion system (TTSS) to establish a persistent infection of the murine respiratory tract. Previous studies have shown that the Bordetella TTSS mediated cytotoxicity in different cell types, inhibition of NF-kappaB in epithelial cells, and differentiation of dendritic cells into a semimature state. Here we demonstrate modulation of mitogen-activated protein kinase (MAPK) signaling pathways and altered cytokine production in macrophages and dendritic cells by the Bordetella TTSS. In macrophages, the MAPKs ERK and p38 were downregulated. This resulted in attenuated production of interleukin- (IL-)6 and IL-10. In contrast, the Th-1-polarizing cytokine IL-12 was produced at very low levels and remained unmodulated by the Bordetella TTSS. In dendritic cells, ERK was transiently activated, but this failed to alter cytokine profiles. These results suggest that the Bordetella TTSS modulates antigen-presenting cells in a cell type-specific manner and the secretion of high levels of IL-6 and IL-10 by macrophages might be important for pathogen clearance.
Asunto(s)
Bordetella bronchiseptica/metabolismo , Activación de Macrófagos , Proteínas Quinasas Activadas por Mitógenos/fisiología , Toxina de Adenilato Ciclasa/fisiología , Animales , Bordetella bronchiseptica/inmunología , Células Cultivadas , Regulación hacia Abajo , Interleucina-10/biosíntesis , Interleucina-6/biosíntesis , Sistema de Señalización de MAP Quinasas , Ratones , FosforilaciónRESUMEN
Bordetella bronchiseptica establishes persistent infection of the murine respiratory tract. We hypothesize that long-term colonization is mediated in part by bacteria-driven modulation of dendritic cells (DCs) leading to altered adaptive immune responses. Bone marrow-derived DCs (BMDCs) from C57BL/6 mice infected with live B. bronchiseptica exhibited high surface expression of MHCII, CD86, and CD80. However, B. bronchiseptica-infected BMDCs did not exhibit significant increases in CD40 surface expression and IL-12 secretion compared with BMDCs treated with heat-killed B. bronchiseptica. The B. bronchiseptica type III secretion system (TTSS) mediated the increase in MHCII, CD86, and CD80 surface expression, while the inhibition of CD40 and IL-12 expression was mediated by adenylate cyclase toxin (ACT). IL-6 secretion was independent of the TTSS and ACT. These phenotypic changes may result from differential regulation of MAPK signaling in DCs. Wild-type B. bronchiseptica activated the ERK 1/2 signaling pathway in a TTSS-dependent manner. Additionally, ACT was found to inhibit p38 signaling. These data suggest that B. bronchiseptica drive DC into a semimature phenotype by altering MAPK signaling. These semimature DCs may induce tolerogenic immune responses that allow the persistent colonization of B. bronchiseptica in the host respiratory tract.
Asunto(s)
Toxina de Adenilato Ciclasa/fisiología , Infecciones por Bordetella/inmunología , Bordetella bronchiseptica/inmunología , Células Dendríticas/inmunología , Animales , Antígenos CD/biosíntesis , Antígeno B7-1/biosíntesis , Antígeno B7-2 , Infecciones por Bordetella/microbiología , Bordetella bronchiseptica/fisiología , Antígenos CD40/biosíntesis , Diferenciación Celular/efectos de los fármacos , Células Dendríticas/metabolismo , Células Dendríticas/patología , Antígenos de Histocompatibilidad Clase II/biosíntesis , Tolerancia Inmunológica , Interleucina-12/biosíntesis , Interleucina-12/genética , Interleucina-12/metabolismo , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Glicoproteínas de Membrana/biosíntesis , Ratones , Ratones Endogámicos C57BL , FagocitosisRESUMEN
Surfactant protein A (SP-A) plays an important role in the innate immune defense of the respiratory tract. SP-A binds to lipid A of bacterial LPS, induces aggregation, destabilizes bacterial membranes, and promotes phagocytosis by neutrophils and macrophages. In this study, SP-A interaction with wild-type and mutant LPS of Bordetella pertussis, the causative agent of whooping cough, was examined. B. pertussis LPS has a branched core structure with a nonrepeating trisaccharide, rather than a long-chain repeating O-Ag. SP-A did not bind, aggregate, nor permeabilize wild-type B. pertussis. LPS mutants lacking even one of the sugars in the terminal trisaccharide were bound and aggregated by SP-A. SP-A enhanced phagocytosis by human monocytes of LPS mutants that were able to bind SP-A, but not wild-type bacteria. SP-A enhanced phagocytosis by human neutrophils of LPS-mutant strains, but only in the absence of functional adenylate cyclase toxin, a B. pertussis toxin that has been shown to depress neutrophil activity. We conclude that the LPS of wild-type B. pertussis shields the bacteria from SP-A-mediated clearance, possibly by sterically limiting access to the lipid A region.