RESUMO
The obligate intracellular pathogen Chlamydophila pneumoniae (Chlamydia pneumoniae) initiates infections in humans via the mucosal epithelia of the respiratory tract. Here, we report that epithelial cells infected with C. pneumoniae are resistant to apoptosis induced by treatment with drugs or by death receptor ligation. The induction of protection from apoptosis depended on the infection conditions since only cells containing large inclusions were protected. The underlying mechanism of infection-induced apoptosis resistance probably involves mitochondria, the major integrators of apoptotic signaling. In the infected cells, mitochondria did not respond to apoptotic stimuli by the release of apoptogenic factors required for the activation of caspases. Consequently, active caspase-3 was absent in infected cells. Our data suggest a direct modulation of apoptotic pathways in epithelial cells by C. pneumoniae.
Assuntos
Apoptose , Chlamydophila pneumoniae/crescimento & desenvolvimento , Células Epiteliais/microbiologia , Apoptose/efeitos dos fármacos , Caspase 3 , Caspases/metabolismo , Grupo dos Citocromos c/metabolismo , Ativação Enzimática , Humanos , Mitocôndrias/efeitos dos fármacos , Estaurosporina/farmacologia , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
Chlamydiae are obligate intracellular bacteria residing exclusively in host cell vesicles termed inclusions. We have investigated the effects of deferoxamine mesylate (DAM)-induced iron deficiency on the growth of Chlamydia pneumoniae and Chlamydia trachomatis serovar L2. In epithelial cells subjected to iron starvation and infected with either C. pneumoniae or C. trachomatis L2, small inclusions were formed, and the infectivity of chlamydial progeny was impaired. Moreover, for C. trachomatis L2, we observed a delay in homotypic fusion of inclusions. The inhibitory effects of DAM were reversed by adding exogenous iron-saturated transferrin, which restored the production of infectious chlamydiae. Electron microscopy examination of iron-deprived specimens revealed that the small inclusions contained reduced numbers of C. pneumoniae that were mostly reticulate bodies. We have previously reported specific accumulation of transferrin receptors (TfRs) around C. pneumoniae inclusions within cells grown under normal conditions. Using confocal and electron microscopy, we show here a remarkable increase in the amount of TfRs surrounding the inclusions in iron-starved cultures. It has been shown that iron is an essential factor in the growth and survival of C. trachomatis. Here, we postulate that, for C. pneumoniae also, iron is an indispensable element and that Chlamydia may use iron transport pathways of the host by attracting TfR to the phagosome.
Assuntos
Chlamydophila pneumoniae/crescimento & desenvolvimento , Células Epiteliais/microbiologia , Deficiências de Ferro , Chlamydia trachomatis/efeitos dos fármacos , Chlamydia trachomatis/crescimento & desenvolvimento , Chlamydia trachomatis/patogenicidade , Infecções por Chlamydophila/etiologia , Chlamydophila pneumoniae/patogenicidade , Endocitose , Células Epiteliais/patologia , Humanos , Quelantes de Ferro/farmacologia , Especificidade da Espécie , Células Tumorais CultivadasRESUMO
The humoral responses of laboratory-reared jirds (Meriones libycus) to inoculation with various doses of Leishmania major were determined. The animals were inoculated intradermally with 10(2), 10(3), 10(5) or 10(7) promastigotes of a strain of L. major originally isolated from a Jordanian patient. The jirds were then bled at various intervals throughout the 26 weeks of the study, and the sera checked, by IFAT, for antibodies to homologous parasites. There were no detectable humoral responses in the animals inoculated with 10(2) promastigotes each or in parasite-free controls but a positive response was apparent in each of the other jirds. The animals given 10(3) promastigotes each required 3 months to become IFAT-positive whereas those given 10(5) and 10(7) parasites only needed 4 and 2 weeks, respectively. More than 50% of the animals inoculated with 10(3) parasites each developed strongly positive sera 2 months post-infection, whereas > 50% of the animals inoculated with 10(5) or 10(7) parasites each had strongly or very strongly positive sera 4 and 2 weeks post-inoculation, respectively. The data indicate that, in M. libycus inoculated with L. major, the time required for the humoral response to develop and its intensity are both dose-related.
Assuntos
Anticorpos Antiprotozoários/sangue , Gerbillinae/imunologia , Leishmania major/imunologia , Leishmaniose Cutânea/imunologia , Animais , Técnica Indireta de Fluorescência para Anticorpo , Gerbillinae/parasitologia , Fatores de TempoRESUMO
Chlamydiae are obligate intracellular pathogens that reside within a membrane-bound vacuole throughout their developmental cycle. In this study, the intraphagosomal pH of Chlamydia pneumoniae (Cpn) was qualitatively assessed, and the intracellular fate of the pathogen-containing vacuole and its interaction with endocytic organelles in human epithelial cells were analysed using conventional immunofluorescence and confocal microscopy. The pH-sensitive probes acridine orange (AO), LysoTracker (LyT) and DAMP did not accumulate in the bacterial inclusion. In addition, exposure of cells to bafilomycin A1(BafA1), a potent acidification inhibitor, did not inhibit or delay chlamydial growth. The chlamydial compartment was not accessible to the fluid-phase tracer Texas Red (TR)-dextran and did not exhibit any level of staining for the late endosomal marker cation-independent mannose-6-phosphate receptor (Ci-M6PR) or for the lysosomal-associated membrane proteins (LAMP-1 and -2) and CD63. In addition, transferrin receptor (TfR)-enriched vesicles were observed close to Cpn vacuoles, potentially indicating a specific translocation of these organelles through the cytoplasm to the vicinity of the vacuole. We conclude that Cpn, like other chlamydial spp., circumvents the host endocytic pathway and inhabits a non-acidic vacuole, which is dissociated from late endosomes and lysosomes, but selectively accumulates early endosomes.
Assuntos
Chlamydophila pneumoniae/patogenicidade , Endocitose , Células Epiteliais/microbiologia , Macrolídeos , Vacúolos/microbiologia , Antibacterianos/farmacologia , Linhagem Celular , Chlamydophila pneumoniae/crescimento & desenvolvimento , Cloranfenicol/farmacologia , Dextranos/metabolismo , Endossomos/metabolismo , Endossomos/microbiologia , Inibidores Enzimáticos/farmacologia , Células Epiteliais/metabolismo , Células HeLa , Humanos , Concentração de Íons de Hidrogênio/efeitos dos fármacos , Corpos de Inclusão/efeitos dos fármacos , Corpos de Inclusão/microbiologia , Lisossomos/metabolismo , Fusão de Membrana/efeitos dos fármacos , Microscopia Confocal , Fagossomos/metabolismo , Fagossomos/microbiologia , Inibidores da Síntese de Proteínas/farmacologia , Receptores da Transferrina/metabolismo , Vacúolos/metabolismoRESUMO
Rodents were collected from endemic foci of cutaneous leishmaniasis in Jordan, either by flooding their burrows with water or using Sherman traps. Of the 170 jirds (Psammomys obesus) collected, 39 (23%) had Leishmania amastigotes in one or both ears. Although cultures of ear biopsies from the infected animals were all positive, cultures made using biopsies from their noses, livers or spleens were all negative. The infected jirds were encountered in seven of the nine areas studied. Biochemical characterization of six isolates from P. obesus, using cellulose acetate electrophoresis of six enzymes (glucose-6-phosphate dehydrogenase, 6-phosphogluconic dehydrogenase, malic enzyme, phosphoglucomutase, phosphoglucoisomerase and fructokinase) showed that the jird isolates were isoenzymatically identical with two Jordanian human Leishmania isolates and reference isolates of L. major but differed from reference strains of L. tropica. None of the other rodents caught (Meriones libycus, M. crassus, M. tristrami, Allactaga euphratica and Gerbillus spp.) yielded Leishmania parasites, confirming that P. obesus is the major reservoir host of cutaneous leishmaniasis in Jordan.