Activation of toll-like receptor 9 by DNA from different bacterial species.
Toll-like receptor 9 (TLR-9) recognizes unmethylated CpG dinucleotides which are abundant in prokaryotic DNA and yet are rare in eukaryotic DNA. Little is known about the significance of TLR-9 in terms of recognition of different bacterial DNA species. In this study HEK293 cells stably transfected with human TLR-9 were used to analyze the immunostimulatory properties of 15 bacterial DNA preparations. In addition, bacterial genome data were analyzed for the frequency of unmethylated cytosine-guanosine ([CG]) dinucleotides. We observed that DNA samples of different bacteria showed considerable differences in their potential to stimulate TLR-9. This correlated with the frequency of [CG] dinucleotides. Based upon data from our experiments the estimate of immunostimulatory bacterial DNA concentrations translated to as high as 10(9) bacteria/ml. Application of the transfection reagent DOTAP resulted in a more efficient delivery of DNA into the cell, and this went along with increased TLR-9 activation. The data indicate that bacterial DNA preparations from different species differ in their capacity to activate TLR-9, which is dependent on the individual [CG] content. Moreover, increased intracellular delivery results in a marked enhancement of immunostimulation.
Dalpke
Alexander
A
Department of Hygiene and Medical Microbiology, Hygiene Institute, University Hospital Heidelberg, Im Neuenheimer Feld 324, D-69120 Heidelberg, Germany. alexander.dalpke@med.uni-heidelberg.de
Frank
Jutta
J
Peter
Mirjam
M
Heeg
Klaus
K
D000818:Animals; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D018899:CpG Islands / Q000276:immunology*; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008264:Macrophages; D051379:Mice; D009838:Oligodeoxyribonucleotides / Q000276:immunology*; D013045:Species Specificity; D051217:Toll-Like Receptor 9 / Q000378:metabolism*
C408982:CPG-oligonucleotide; D004269:DNA, Bacterial; D009838:Oligodeoxyribonucleotides; D051217:Toll-Like Receptor 9