- Universität Zürich > Medizinische Fakultät > Neuropathologie, Institut für > Prof. Dr. Adriano Aguzzi
- Heikenwälder
Completed Research Project
- Title / Titel
- Cellular recognition of host and pathogenic DNA: investigating TLR signalling pathways and receptors
- Summary / Zusammenfassung
- DNA containing unmethylated cytidyl guanosyl (CpG) sequences, which are underrepresented in mammalian genomes but prevalent in prokaryotes, is endocytosed by macrophages, monocytes and dendritic cells 1, and activates a pathway involving Toll-like receptor 9 (TLR9). CpG-containing oligodeoxynucleotides (CpG-ODN) are potent stimulators of innate immunity. Moreover methylated ODNs are currently being tested as adjuvants of antimicrobial, antiallergic, and anticancer immunotherapy and have been recently proposed as a potential antiprion therapeutic 2. However this important pathway of the innate immunity has only recently been discovered and many control switches and control mechanisms are still unknown.
Our research proposal consists of three main projects.
(1) We seek to elucidate a new TLR9 adaptor molecule. Mice lacking MyD88, the only TLR9 adaptor molecule known, show splenic destruction similar to wild-type mice following CpG-ODN treatment (Heikenwalder M., Polymenidou M., Sigurdson C. and Aguzzi A., unpublished data), whereas Tlr9-/- mice have normal splenic microarchitecture. These results strongly suggest a second adaptor molecule signals in response to TLR9 activation. We will define the molecular mechanisms of this second adaptor in collaboration with Prof. Bruce Beutler from the Scripps Research Institute (TSRI), who in parallel has found by positional cloning a new putative TLR9-signalling molecule, named 3D (Prof. Bruce Beutler, unpublished results). Since repeated CpG-ODN treatment has not only beneficial but also detrimental effects 3, knowledge about new TLR9 dependent pathways that reduce immunoclastic effects of CpG-ODN administration may have an important implication for all therapeutic regimens using CpG-ODN.
(2) We will characterize receptors that sense host encoded genomic DNA from necrotic cells. Abundant literature describes the adjuvant effects of “normal” eukaryotic DNA. So far, the mechanism by which eukaryotic DNA gains is immunostimulatory is unknown. We hypothesize that lymphoid cells or perhaps even stromal cells recognize necrotic cell death via released genomic DNA. Indeed, Tlr9-/- mice treated with synthesized DNA (CpG motifs lacking/10nmol daily for 7 days) show signs which include hyperventilation and ataxia within minutes of treatment, whereas C57BL/6 mice treated with AT-ODN and C57BL/6 or Tlr9-/- mice treated CpG-ODN show no clinical signs. These results suggest that there is an additional receptor for cellular DNA which is masked in a TLR9+/+ genomic background. As a matter of fact it was recently shown that vaccination with DNA functions in Tlr9-/- and myd88-/- mice indicating that DNA can trigger an immune response in a TLR9 and MyD88 independent fashion. However the mechanism and cell type for this activation remains unknown 4.
(3) We will investigate whether ablation of specific Toll-like receptors (TLR9, TLR3 or TLR7), which are normally stimulated by methylated ODN, ssRNA or dsRNA, respectively, can alter susceptibility to prions. So far, the receptors utilized for prion entry and conversion are unknown. It is possible that Toll-like receptors facilitate prion uptake and conversion, and that the published antiprion effects of CpG-ODN 2 resemble a competition in which CpG-ODN blocks TLR9 and thereby prevents prion uptake and entry.
- Keywords / Suchbegriffe
- DNA, toll-like receptors, prions
- Project Leadership and Contacts /
Projektleitung und Kontakte Dr. Mathias Heikenwälder (Project Leader) mathais.heikenwaelder@usz.ch
- Funding Source(s) /
Unterstützt durch - Forschungskredit der Universität Zürich
- Duration of Project / Projektdauer
- Nov 2004 to Oct 2006