Differential activation of immune cells by commensal versus pathogen-derived bacterial DNA

Günalp, Sinem
Immunological mechanisms making contribution to discriminating signals obtained from commensal versus pathogenic bacteria is an active area of research and recent evidence proposes that commensals and pathogens might express discrete variants of pathogen associated molecular patterns (PAMP). We hypothesized that as a major member of PAMP, bacterial DNA (bacDNA) originating from commensals versus pathogens might possess distinct immunostimulatory activities, enabling their dis- crimination by the immune system. To test this hypothesis, DNAs derived from two bona fide commensal bacteria, Lactobacillus fermentum, Lactobacillus salivarus, one commensal strain of Enterococcus faecium, one virulent clinical isolate of Enterococcus faecium and 2 strict pathogens; Listeria monocytogenes, Streptococcus pyogenes were used for human peripheral blood mononuclear cells, human neutrophils, murine splenocytes, murine fibroblasts, THP-1 monocytes, human (h)TLR9 expressing HEK cells, STING expressing and STING knockout interferon reporter cell lines were stimulated with various doses of human commensal or pathogen-derived purified DNAs as such or following their complexation with the transfection reagent Lipofectamine 2000. Results showed that commensal but not pathogen derived bacDNA induced IP-10 and IFN secretion from hPBMC. However, there was no significant difference in STING expressing B16 IFN-reporter cell line and murine fibroblast L929 cells. Almost 30-60% of the observed response was STING dependent. In contrast, DNAs derived from pathogens triggered significantly higher levels of TNF-α, IL-6 and/or IL-1 production from hPBMCs, human neutrophils and murine splenocytes. Consistent with this, NF-κB activation by hTLR9 expressing HEK cells was significantly higher upon stimulation with DNAs derived from pathogens. In conclusion, our findings suggest that pathogen and commensal bacterial DNAs are recognized by distinct sets of receptors and induce differential activation of immune cells. Collectively, commensal versus pathogen derived DNA’s route of entry into cells, their recognition by selective receptors /sensors and also their resistance to plasma nucleases might be important factors that contribute to such distinct responses.


Differential activation of immune cells by commensal versus pathogen-derived bacterial RNA
Özcan, Mine; Gürsel, Mayda; Department of Biology (2014)
Immunological mechanisms contributing to distinguishing signals derived from commensal versus pathogenic bacteria is an active area of research and recent evidence suggests that commensal and pathogens may express different variants of pathogen associated molecular patterns (PAMP). In this thesis, we propose that as a major member of PAMP, bacterial RNAs derived from commensal and pathogens may have distinct immunostimulatory activities due to differentially recognition by the host immune system. In order t...
Cutting edge: Role of toll-like receptor 9 in CpG DNA-induced activation of human cells
Takeshita, F; Leifer, CA; Gursel, I; Ishii, KJ; Takeshita, S; Gürsel, Mayda; Klinman, DM (The American Association of Immunologists, 2001-10-01)
Unmethylated CpG motifs present in bacterial DNA stimulate a rapid and robust innate immune response. Human cell lines and PBMC that recognize CpG DNA express membrane-bound human Toll-like receptor 9 (hTLR9). Cells that are not responsive to CpG DNA become responsive when transfected with hTLR9. Expression of hTLR9 dramatically increases uptake of CpG (but not control) DNA into endocytic vesicles. Upon cell stimulation, hTLR9 and CpG DNA are found in the same endocytic vesicles. Cells expressing hTLR9 are ...
CpG oligodeoxynucleotides protect normal and SIV-infected macaques from Leishmania infection.
Verthelyi, D; Gürsel, Mayda; Kenney, RT; Lifson, JD; Liu, S; Mican, J; Klinman, DM (The American Association of Immunologists, 2003-05-01)
Oligodeoxynucleotides containing CpG motifs (CpG ODNs) mimic microbial DNA and activate effectors of the innate immune response, which limits the spread of pathogens and promotes an adaptive immune response. CpG ODNs have been shown to protect mice from infection with intracellular pathogens. Unfortunately, CpG motifs that optimally stimulate humans are only weakly active in mice, mandating the use of nonhuman primates to monitor the activity and safety of "human" CpG ODNs in vivo. This study demonstrates t...
Live-cell imaging of Pol II promoter activity to monitor gene expression with RNA IMAGEtag reporters
SHIN, Ilchung; RAY, Judhajeet; Gupta, Vinayak; İlgü, Müslüm; Beasley, Jonathan; BENDICKSON, Lee; MEHANOVIC, Samir; Kraus, George A.; Nilsen-Hamilton, Marit (Oxford University Press (OUP), 2014-01-01)
We describe a ribonucleic acid (RNA) reporter system for live-cell imaging of gene expression to detect changes in polymerase II activity on individual promoters in individual cells. The reporters use strings of RNA aptamers that constitute IMAGEtags (Intracellular MultiAptamer GEnetic tags) that can be expressed from a promoter of choice. For imaging, the cells are incubated with their ligands that are separately conjugated with one of the FRET pair, Cy3 and Cy5. The IMAGEtags were expressed in yeast from ...
Immunomodulatory activities of RNA species derived from commensal and pathogenic bacteria
Kayaoğlu, Başak; Gürsel, Mayda; Department of Biology (2017)
Bacterial RNAs are recognized by various types of immune sensors. Here, we aimed to investigate the differential immune activation mediated by RNAs purified from commensal or pathogenic bacteria. For this, total RNAs and/or individual ribosomal RNAs (5S, 16S and 23S) were isolated from two commensal bacteria, Lactobacillus salivarious and Lactobacillus fermentum and two pathogens, Listeria monocytogenes, and Streptococcus pyogenes. Bacterial RNA species isolated from pathogens induced stronger pro-inflammat...
Citation Formats
S. Günalp, “Differential activation of immune cells by commensal versus pathogen-derived bacterial DNA,” M.S. - Master of Science, Middle East Technical University, 2015.