Article

MyD88 is pivotal for the early inflammatory response and subsequent bacterial clearance and survival in a mouse model of Chlamydia pneumoniae pneumonia

Division of Pediatrics Infectious Diseases and Immunology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90048, USA.
Journal of Biological Chemistry (Impact Factor: 4.6). 09/2005; 280(32):29242-9. DOI: 10.1074/jbc.M503225200
Source: PubMed

ABSTRACT Chlamydia pneumoniae is the causative agent of respiratory tract infections and a number of chronic diseases. Here we investigated the involvement of the common TLR adaptor molecule MyD88 in host responses to C. pneumoniae-induced pneumonia in mice. MyD88-deficient mice were severely impaired in their ability to mount an acute early inflammatory response toward C. pneumoniae. Although the bacterial burden in the lungs was comparable 5 days after infection, MyD88-deficient mice exhibited only minor signs of pneumonia and reduced expression of inflammatory mediators. MyD88-deficient mice were unable to up-regulate proinflammatory cytokines and chemokines, demonstrated delayed recruitment of CD8+ and CD4+ T cells to the lungs, and were unable to clear the pathogen from their lungs at day 14. At day 14 the MyD88-deficent mice developed a severe, chronic lung inflammation with elevated IL-1beta and IFN-gamma leading to increased mortality, whereas wild-type mice as well as TLR2- or TLR4-deficient mice recovered from acute pneumonia and did not show delayed bacterial clearance. Thus, MyD88 is essential to recognize C. pneumoniae infection and initiate a prompt and effective immune host response against this organism leading to clearance of bacteria from infected lungs.

0 Followers
 · 
115 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aetiology of OAL is undefined, although much attention has been recently focused on determining whether OAL is caused by an autoimmune disorder, chronic antigenic stimulation or both. It is becoming evident that infectious agents underlying chronic eye infection, as Chlamydia, may play a role in ocular lymphomagenesis. The high prevalence of Chlamydophila psittaci in patients with OAL has suggested a potential oncogenic role for its tendency to cause chronic and persistent infections, although it has been documented an evident geographical variability and response to antibiotic treatment. For C. pneumoniae, the findings so far obtained are very limited not only for identification in OAL but also for the specific treatment with antibiotics. The recent molecular and cultural evidence of C. trachomatis in patients with OAL, seems to suggest that also this pathogen may contribute to pathogenesis of such lymphoma. The potential appli- cation of bacteria-eradicating therapy at local and systemic level may ultimately result in safer and more efficient therapeutic option for patients affected by these malignancies. Moreover, a close collaboration between experts in oph- thalmology, infectious diseases and hematology will help, in the future, to effectively manage this disease. This review attempts to weigh the currently available evidence regarding the role that Chlamydia play in development of OAL and focuses on patients with OAL observed at our Institution.
    Journal of Cancer Therapy 03/2013; 4(02):662-677. DOI:10.4236/jct.2013.42082
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chlamydophila pneumoniae is an obligate intracellular pathogen which leads to mostly asymptomatic infections of the respiratory tract. After acute infection, C. pneumoniae can establish persistent infections in the host. To be able to prevent persistence, it is necessary to understand how C. pneumoniae are recognized by the innate immune cells and which evasion strategies are used to hide from the immune system. The association of atherosclerosis with persistent C. pneumoniae infections is discussed for decades now. Especially seroepidemiological studies lead to controversial results. In this respect, the validity of assays for serodiagnosis was identified as crucial key factor. Most convincing evidence comes from studies which report the presence of viable C. pneumoniae in the diseased vessel wall, while they were never detected in healthy tissue. However, the route of dissemination from the lung to the vasculature is still unclear. Currently, PMN are discussed as vectors for C. pneumoniae. • To investigate the role of TLR2 and TLR4 in vivo, a murine model was established. Mice were infected intranasally with a low dose of 106 C. pneumoniae and the infection was monitored by serology and determination of the bacterial burden in the lung and BAL by quantitative real-time PCR. No differences in clearance of bacteria and serological response were observed between TLR2-/- and TLR4 deficient mice and their respective wild types, but cytokine release was diminished in TLR2-/- and in part inTLR4-deficient mice in vivo and in vitro. • DNA samples of 160 healthy subjects were genotyped for the NOD2 3020insC frame shift mutation and 7.5% heterozygous polymorphism carriers were identified. Their C. pneumoniae-induced cytokine release from blood leukocytes was significantly higher compared to wild-types. • The cytokine-inducing capacity of C. pneumoniae was shown to be weak in comparison to E. coli and enterococcal LPS and was characterized by a more pronounced release of anti-inflammatory mediators. • The presence of an anti-CD14 antibody and the LPS-specific inhibitor LALF completely abrogated the release of pro-inflammatory cytokines by C. pneumoniae, while the anti-inflammatory IL-10 was not affected. Furthermore, prototypic LPS-induced pro-inflammatory cytokine release was impaired by co-incubation with C. pneumoniae, while again IL-10 remained unaffected. • Isolation of immune active compounds of C. pneumoniae was carried out by butanol extraction. After separation by HIC a pool of immune active fractions with comparable cytokine inducing properties as whole C. pneumoniae was obtained. Chemical analysis revealed that the pooled fractions are still structurally inhomogeneous but contain a lipopeptide. Analysis by LAL confirmed that a low amount of LPS was present. • The ELISAs, SeroCP and SeroCP Quant and the sELISA were evaluated for C. pneumoniae IgG serodiagnosis in comparison to the gold standard MIF. The concordance with MIF was ≥90% for all ELISAs for a collective of 80 patients and the PPVs were all ≥93%, while the NPVs ranged from 68-83%. False-negative results were obtained only from samples with low titers in MIF. • Co-incubation of C. pneumoniae-infected PMN with endothelial cells (HUVEC) resulted in transmission of about 10% of the PMN-ingested C. pneumoniae to HUVEC and inclusions were formed. C. pneumoniae harvested from HUVEC retained infectivity since they were still able to multiply in HEp-2 cells. Exposure to laminar shear stress exhibits a protective effect on HUVEC and impedes formation of inclusions after C. pneumoniae infection by PMN. In summary, this thesis emphasizes the high complexity of the interactions of C. pneumoniae with the innate immune system. We have shown that at least three PRR, i.e. TLR2, TLR4 and NOD are engaged in immune recognition and subsequent induction of inflammatory responses induced by C. pneumoniae. Modulations of immune reactions are most probably triggered by the characteristic anti-inflammatory properties of C. pneumoniae which may lead to the asymptomatic course of infection and render them capable to escape host defence and to establish intracellular persistent infections. Moreover, instead of being eradicated after uptake by phagocytosis, C. pneumoniae stay viable and thus can use the phagocytes as shuttle vectors spreading the infection to the vasculature. Thereby, the prevention of vascular infection by laminar shear stress can explain the focal distribution of C. pneumoniae into areas prone to develop atherosclerotic lesions. This thesis elucidates risk factors, pathogenesis, immune activation and evasion as well as diagnostics of the most prominent infectious agent suspected to contribute to atherosclerosis. These aspects are crucial to finally settle the argument, whether myocardial infarction has in part to be considered an infectious disease. Chlamydophila pneumoniae ist ein obligat intrazelluläres Pathogen, das zu meist asymptomatischen Atemwegsinfektionen führt. Nach akuter Infektion kann C. pneumoniae im Organismus persistieren. Um deren Persistenz vorzubeugen, ist es wichtig, zu verstehen, wie C. pneumoniae von Zellen des angeborenen Immunsystems erkannt wird und welche Strategien angewendet werden, sich vor dem Immunsystem zu verstecken. Eine Assoziation peristenter C. pneumoniae-Infektionen mit Atherosklerose wird bereits seit Jahrzehnten diskutiert. Besonders seroepidemiologische Studien führen zu kontroversen Ergebnissen. In dieser Hinsicht wurde die Stichhaltigkeit von Serodiagnoseverfahren als kritischer Schlüsselfaktor identifiziert. Den überzeugendsten Nachweis erhält man von Studien, die das Vorhandensein von lebenden C. pneumoniae im atherosklerotischen aber nicht im gesunden Gewebe beschreiben. Jedoch ist deren Ausbreitung von der Lunge zu den Gefäßen nach wie vor unklar. Gegenwärtig werden Phagozyten als Transportsystem für C. pneumoniae diskutiert. • Um die Rolle von TLR2 und TLR4 in vivo zu untersuchen, wurde ein Mausmodell etabliert. Hierbei wurden Mäuse intranasal mit einer geringen Dosis von 106 C. pneumoniae infiziert und die Infektion mittels Serologie und Nachweis der Erregerlast in Lunge und BAL über quantitative real-time-PCR verfolgt. Dabei wurden keine Unterschiede in der Beseitigung der Erreger und der serologischen Antwort zwischen TLR2-/- und C3H/HeJ Mäusen und ihren zugehörigen Wildtypen festgestellt, jedoch war die Cytokinantwort in TLR2-/- und teilweise in C3H/HeJ Mäusen in vivo und in vitro vermindert. • DNA-Proben von 160 gesunden Spendern wurden für den NOD2-3020insC-Polymorphismus genotypisiert und es wurden 7,5% heterozygote Polymorphismusträger identifiziert. Deren durch C. pneumoniae induzierte Cytokininduktion war im Vergleich zu den Wildtypen signifikant erhöht. • Die Fähigkeit, Cytokine zu induzieren, war für C. pneumoniae verglichen mit E. coli oder Enterokokken-LPS eher schwach, zeichnete sich aber durch eine verstärkte Freisetzung anti-inflammatorischer Mediatoren aus. • Bei Zugabe eines anti-CD14 Antikörpers und des LPS-spezifischen Inhibitors LALF wurde die Freisetzung pro-inflammatorischer Cytokine durch C. pneumoniae vollständig gehemmt, während anti-inflammatorisches IL-10 nicht beeinträchtigt wurde. • Immunaktive Komponenten von C. pneumoniae wurden mittels Butanolextraktion isoliert. Nach HIC-Auftrennung erhielten wir einen Pool immunaktiver Fraktionen mit vergleichbaren cytokininduzierenden Eigenschaften wie ganzen C. pneumoniae. Die chemische Analyse ergab, dass die gepoolten Fraktionen zwar strukturell inhomogen sind, jedoch ein Lipopeptid enthalten ist. Die LAL-Auswertung bestätigte einen geringen Anteil LPS. • Die ELISAs SeroCP und SeroCP Quant und der sELISA wurden für die C. pneumoniae-Serodiagnose im Vergleich zum Goldstandard MIF evaluiert. Die Übereinstimmung zum MIF war ≥90% für alle ELISAs in einem Kollektiv von 80 Patienten und die PPVs lagen alle über ≥93% während die NPVs zwischen 68-83% schwankten. Falsch-negative Ergebnisse wurden nur für Proben erhalten, die einen niedrigen Titer im MIF hatten. • Bei Ko-Inkubation von C. pneumoniae-infizierten Phagozyten mit Endothelzellen (HUVEC) wurden zirka 10% der phagozytierten C. pneumoniae übertragen und Einschlüsse ausgebildet. Aus einer solchen Infektion geerntete C. pneumoniae waren noch infektiös, da sie sich nach wie vor in HEp2-Zellen vermehren konnten. Laminare Schubspannung übte einen protektiven Effekt auf HUVEC aus, da die Bildung von Einschlüssen gehemmt war. Zusammengefasst betont diese Arbeit die hohe Komplexität der Interaktionen von C. pneumoniae mit dem angeborenen Immunsystem. Wir haben gezeigt, dass mindestens TLR2, TLR4 und NOD bei der Erkennung und anschließender Induktion entzündlicher Prozesse durch C. pneumoniae beteiligt sind. Immunreaktionen werden wahrscheinlich durch die charakteristischen anti-inflammatorischen Eigenschaften von C. pneumoniae moduliert, die zum asymptomatischen Infektionsverlauf und dadurch zur Persistenz führen könnten. Anstatt nach der Phagozytose eradiziert zu werden, überleben C. pneumoniae in Phagozyten und können diese als Vektoren für den Transport zu den Gefäßen nutzen. Dass dabei die Infektion durch laminare Schubspannung verhindert wird, könnte die fokale Verteilung von C. pneumoniae in Bereiche erklären, die besonders anfällig für die Entwicklung atherosklerotischer Läsionen sind. In dieser Arbeit werden Risikofaktoren, Pathogenese, Immunaktivierung und –evasion, sowie Diagnostika des wohl bekanntesten mit Atherosklerose assoziierten infektiösen Erregers erläutert. Diese Aspekte könnten ausschlaggebend sein, den Herzinfarkt letztendlich zum Teil als Infektionskrankheit zu betrachten.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Host response to chlamydial urethral infection in male guinea pigs