Short- and long-term changes in gene expression mediated by the activation of TLR9

Abstract

CpG DNA binds to Toll-like receptor 9 to stimulate a strong innate immune response. The magnitude, duration and scope of CpG-induced changes in gene expression is incompletely understood despite extensive studies of TLR9 mediated signal transduction pathways. In particular, the prolonged effects of CpG DNA on gene activation have not been investigated despite evidence that a single dose of CpG DNA alters immune reactivity for several weeks. This study used gene expression analysis to monitor changes in mRNA levels for 14 days, and identified the genes, pathways and functional groups triggered in vivo following CpG DNA administration. Two discrete peaks of gene activation (at 3 hr and 5 days) were observed after CpG injection. Both the behavior and function of genes activated during the second peak differed from those triggered shortly after CpG administration. Initial gene up-regulation corresponded to a period when TLR9 ligation stimulated genes functionally associated with the generation of innate and adaptive immune responses (e.g. the NF-kB and B-cell receptor pathways). The second peak reflected processes associated with cell division (e.g., cell cycle and DNA replication & repair). The complex bimodal pattern of gene expression elicited by CpG DNA administration provides novel insights into the long term effects of TLR9 engagement on genes associated with immunity and cell proliferation.

TLR7 and TLR9 ligands regulate antigen presentation by macrophages

“…This distinctive profile and increase in long-term survival is consistent with a bimodal pattern of gene regulation observed after in vitro treatment and in vivo administration of CpG (31,32). The initial peak (2-4 h post-CpG) is characterized by a rapid up-regulation of genes associated with the activation of the immune system, such as NF-κB and TNF, followed by induction of the regulatory gene, Myc at 8 h (31,32). Subsequently, 5 days post-CpG administration, an upregulation of genes associated with cell-cycle regulation and DNA damage responses are detected (32).…”

“…However, at 24 h post-CpG or R848 stimulation, we detected a preferential skewing toward an M2-like state, defined by a lower ratio of Il-12/Il-10 compared with LPS. This distinctive profile and increase in long-term survival is consistent with a bimodal pattern of gene regulation observed after in vitro treatment and in vivo administration of CpG (31,32). The initial peak (2-4 h post-CpG) is characterized by a rapid up-regulation of genes associated with the activation of the immune system, such as NF-κB and TNF, followed by induction of the regulatory gene, Myc at 8 h (31,32).…”

“…The initial peak (2-4 h post-CpG) is characterized by a rapid up-regulation of genes associated with the activation of the immune system, such as NF-κB and TNF, followed by induction of the regulatory gene, Myc at 8 h (31,32). Subsequently, 5 days post-CpG administration, an upregulation of genes associated with cell-cycle regulation and DNA damage responses are detected (32).…”

Environmental and T Cell–Intrinsic Factors Limit the Expansion of Neonatal Follicular T Helper Cells but May Be Circumvented by Specific Adjuvants

“…In adults, there was a small but not significant increase in the number of PCs (Fig. 7B), the immunostimulatory influence of CpG-ODNs in line with previous data showing that adjuvants induce changes in cell activation and function rather than in frequency (28). In neonates, the increase in Ab titers was associated with a modest increase in the number of PCs (Fig.…”

Regulation of the maturation of human monocytes into immunosuppressive macrophages

“…Gene expression was evaluated after 4 hours, a time point previously found to be optimal for detecting the pathways activated by TLR stimulation using IPA software. 21,34,35 IPA predicted that regulatory networks involving the NF-kB complex, MAPK, ERK, Akt, and PTGS2 (COX-2) were central to both PAM3-and M-CSF-driven monocyte maturation. Stimulation of these networks was associated with the upregulation of messenger RNA (mRNA) encoding prostaglandins and cytokines (including IL-6 and IL-10 but not IL-12 or TNFa; Figure 5).…”