RESUMEN
BACKGROUND: Yersinia pestis, the causative agent of plague, showed a temperature-dependent change in lipid A composition, with a reduced degree of acylation when bacteria were grown at 37 degrees C (tetraacylated) versus ambient temperature (hexaacylated). METHODS: Human monocytes and monocyte-derived dendritic cells (DCs) were exposed to Y. pestis grown at 26 degrees C or 37 degrees C, to their corresponding lipopolysaccharides (LPS-26 degrees C or LPS-37 degrees C), and to ligands of different Toll-like receptors (TLRs), such as LPS from Escherichia coli (TLR4), lipoprotein (TLR2), polyinosinic-polycytidylic acid (poly-IC) (TLR9), and their combinations. Production of cytokines was measured, along with expression of surface markers of DC maturation. RESULTS: Y. pestis grown at 37 degrees C or LPS-37 degrees C induced much lower production of cytokines (such as tumor necrosis factor alpha and interleukins 1beta, 10, and 12) by DCs than did Y. pestis grown at 26 degrees C or LPS-26 degrees C. Expression of the surface markers HLA-DR, CD86, and CD40 by DCs was also reduced in response to treatment with LPS-37 degrees C compared with LPS-26 degrees C. Pretreatment of DCs with LPS-37 degrees C inhibited subsequent stimulation with LPS-26 degrees C, control LPS from E. coli, lipoprotein, or poly-IC. CONCLUSIONS: LPS-37 degrees C can inhibit stimulation of DCs not only via TLR4 signaling but also via TLR2 and TLR3. [corrected]
Asunto(s)
Células Dendríticas/inmunología , Lipopolisacáridos/farmacología , Receptores Toll-Like/antagonistas & inhibidores , Yersinia pestis/inmunología , Acilación , Antígeno B7-2/metabolismo , Antígenos CD40/metabolismo , Células Cultivadas , Citocinas/biosíntesis , Citocinas/metabolismo , Células Dendríticas/efectos de los fármacos , Células Dendríticas/metabolismo , Células Dendríticas/microbiología , Escherichia coli/química , Antígenos HLA-DR/metabolismo , Humanos , Monocitos/efectos de los fármacos , Monocitos/inmunología , Monocitos/metabolismo , Poli I-C/farmacología , Transducción de Señal , Temperatura , Receptores Toll-Like/inmunología , Receptores Toll-Like/metabolismo , Yersinia pestis/metabolismoRESUMEN
The ability to protect mice against respiratory infections with virulent Francisella tularensis has been problematic and the role of antibody-versus-cell-mediated immunity controversial. In this study, we tested the hypothesis that protective immunity can develop in mice that were given antibiotic therapy following infection via the respiratory tract with F. tularensis SCHU S4. We show that mice infected with a lethal dose of SCHU S4, via an intra-nasal challenge, could be protected with levofloxacin treatment. This protection was evident even when levofloxacin treatment was delayed 72h post-infection. At early time points after levofloxacin treatment, significant numbers of bacteria could be recovered from the lungs and spleens of mice, which was followed by a dramatic disappearance of bacteria from these tissues. Mice successfully treated with levofloxacin were later shown to be almost completely resistant to re-challenge with SCHU S4 by the intra-nasal route. Serum antibody appeared to play an important role in this immunity. Normal mice, when given sera from animals protected by levofloxacin treatment, were solidly protected from a lethal intra-nasal challenge with SCHU S4. The protective antiserum contained high titers of SCHU S4-specific IgG2a, indicating that a strong Th1 response was induced following levofloxacin treatment. Thus, this study describes a potentially valuable animal model for furthering our understanding of respiratory tularemia and provides suggestive evidence that antibody can protect against respiratory infections with virulent F. tularensis.
Asunto(s)
Antibacterianos/uso terapéutico , Anticuerpos Antibacterianos/biosíntesis , Francisella tularensis , Levofloxacino , Ofloxacino/uso terapéutico , Tularemia/inmunología , Tularemia/prevención & control , Administración Intranasal , Animales , Antibacterianos/farmacocinética , Anticuerpos Antibacterianos/análisis , Formación de Anticuerpos/inmunología , Recuento de Colonia Microbiana , Ensayo de Inmunoadsorción Enzimática , Femenino , Francisella tularensis/patogenicidad , Ratones , Ratones Endogámicos BALB C , Ofloxacino/farmacocinética , Análisis de Supervivencia , Tularemia/microbiología , Virulencia , Zoonosis/microbiologíaRESUMEN
Francisella tularensis is one of the most infectious human pathogens known. Although much has been learned about the immune response of mice using an attenuated live vaccine strain (LVS) derived from F. tularensis subspecies holarctica (Type B), little is known about the responses of human monocyte-derived immature dendritic cells (DC). Here, we show that optimal phagocytosis of LVS by DC is dependent on serum opsonization. We demonstrate that complement factor C3-derived opsonins and the major complement receptors expressed by DC, the integrins CR3 (CD11b/CD18) and CR4 (CD11c/CD18), play a critical role in this adhesion-mediated phagocytosis. LVS induced proinflammatory cytokine production and up-regulation of costimulatory surface proteins (CD40, CD86, and MHC Class II) on DC but resisted killing. Once taken up, LVS grew intracellularly, resulting in DC death. DC maturation and cytokine production were induced by direct contact/phagocytosis of LVS or interaction with soluble products of the bacteria, and enhanced activation was seen when LVS was pretreated with serum. Sonicated LVS and supernatants from LVS cultures were potent activators of DC, but LVS LPS failed to activate DC maturation or cytokine production. Serum-treated LVS rapidly induced (within 6 h) a number of cytokines including IL-10, a potent suppressor of macrophage functions and down-regulator of Th1-like responses and the Th1 response inducer IL-12. These results suggest that the simultaneous production of an activating (IL-12, IL-1beta, and TNF-alpha) and a suppressing (IL-10) cytokine profile could contribute to the immunopathogenesis of tularemia.