CpG oligodeoxynucleotides induce murine macrophages to up-regulate chemokine mRNA expression

CpG DNA: recognition by and activation of monocytes

Unmethylated CpG motifs present in bacterial DNA rapidly trigger an innate immune response characterized by the activation of Ig- and cytokine-secreting cells. Synthetic oligonucleotides (ODNs) containing CpG motifs mimic this activity, triggering monocytes to proliferate, secrete and/or differentiate. Analysis of hundreds of novel ODNs led to the identification of two structurally distinct classes of CpG motif that differentially activate human monocytes. ODNs of the "K"-type interact with Toll-like receptor 9 and induce monocytes to proliferate and secrete IL-6. In contrast, "D"-type ODNs trigger monocytes to differentiate into mature dendritic cells.

Treatment of established asthma in a murine model using CpG oligodeoxynucleotides

Allergen immunotherapy is an effective but underutilized treatment for atopic asthma. We have previously demonstrated that CpG oligodeoxynucleotides (CpG ODN) can prevent the development of a murine model of asthma. In the current study, we evaluated the role of CpG ODN in the treatment of established eosinophilic airway inflammation and bronchial hyperreactivity in a murine model of asthma. In this model, mice with established ovalbumin (OVA)-induced airway disease were given a course of immunotherapy (using low doses of OVA) in the presence or absence of CpG ODN. All mice then were rechallenged with experimental allergen. Untreated mice developed marked airway eosinophilia and bronchial hyperresponsiveness, which were significantly reduced by treatment with OVA and CpG. CpG ODN leads to induction of antigen-induced Th1 cytokine responses; successful therapy was associated with induction of the chemokines interferon-gamma-inducible protein-10 and RANTES and suppression of eotaxin. Unlike previous studies, these data demonstrate that the combination of CpG ODN and allergen can effectively reverse established atopic eosinophilic airway disease, at least partially through redirecting a Th2 to a Th1 response.

Poly(ADP-ribose) polymerase is a regulator of chemokine production: relevance for the pathogenesis of shock and inflammation

BACKGROUND

Chemokines are key regulators of leukocyte traffic in various forms of inflammation and reperfusion injury. There is emerging evidence that the activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) importantly contributes to the up-regulation of a variety of proinflammatory signal transduction pathways and associated genes.

MATERIALS AND METHODS

We tested whether the expression of the chemokines macrophage inflammatory protein (MIP)-1alpha and MIP-2 are under the control of PARP during inflammation.

RESULTS

Pharmacologic inhibition of PARP and genetic deletion of PARP suppressed the expression of MIP-1a and MIP-2 protein and mRNA in immunostimulated cultured murine macrophages and fibroblasts. PARP inhibition also suppressed the activation of NF-kappaB, a key transcription factor known to be involved in the generation of chemokines in immunostimulated cells. In vivo, in various models of local and systemic inflammation, including dextran sodium sulfate-induced colitis and endotoxic shock, pharmacologic inhibition of PARP suppressed the expression of MIP-1alpha and MIP-2. These effects were associated with a marked suppression of the inflammatory response, including an attenuation of neutrophil infiltration into inflamed organs.

CONCLUSIONS

A combination approach of pharmacologic inhibition and genetic deletion revealed that the major isoform of PARP (PARP-1) plays a predominant, but not exclusive, role in the regulation of chemokine production in vivo. Suppression of chemokine expression may be a novel mode of anti-inflammatory action of PARP inhibition.

Plasmid DNA induces increased lymphocyte trafficking: a specific role for CpG motifs

Bacterial DNA, primarily through immunostimulatory cytosine-guanine (CpG) motifs, induces the secretion of cytokines and activates a variety of effector cells. We investigated the possibility that CpG motifs might also modulate immunosurveillance by altering cell trafficking through a regional lymph node. Intradermal injection of plasmid DNA induced rapid and prolonged increases in the number of lymphocytes collected in efferent lymph. This effect on cell trafficking was not dependent on the expression of an encoded reporter gene but varied with plasmid construct and required a circular form. Injection of synthetic oligodeoxyribonucleotides containing CpG motifs did not alter lymphocyte trafficking but CpG-enhanced plasmid induced a dose-dependent increase in cell trafficking. Phenotypic analyses revealed that the increase in cell trafficking involved all lymphocyte subpopulations and represented a mass movement of cells. These observations reveal that bacterial DNA, through immunostimulatory CpG motifs, alters immunosurveillance by increasing cell recruitment to a regional lymph node.

Activation of microglia and astrocytes by CpG oligodeoxynucleotides

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs stimulate cells of the immune system to secrete a variety of cytokines and chemokines. This function can be carried out by microglia and astrocytes in the CNS. To evaluate the effect of CpG ODN on microglia and astrocytes, purified cells were isolated and cultured in vitro. CpG ODN rapidly up-regulated their production of IL-1beta, IL-6, IL-12, TNFalpha, MIP-1alpha and/or MIP-1beta. In vivo, systemically administered CpG ODN up-regulated the expression of mRNA encoding cytokines and chemokines in normal mouse brain. These findings suggest that CpG ODN can directly activate immune cells of the CNS.

Sterically stabilized cationic liposomes improve the uptake and immunostimulatory activity of CpG oligonucleotides

Immunostimulatory CpG oligonucleotides (ODN) show promise as immune adjuvants, anti-allergens, and immunoprotective agents. Increasing the bioavailability and duration of action of CpG ODN should improve their therapeutic utility. Encapsulating ODN in sterically stabilized cationic liposomes provides protection from serum nucleases while facilitating uptake by B cells, dendritic cells, and macrophages. In a pathogen challenge model, sterically stabilized cationic liposomes encapsulation doubled the duration of CpG ODN-induced immune protection. In an immunization model, coencapsulation of CpG ODN with protein Ag (OVA) magnified the resultant Ag-specific IFN-gamma and IgG responses by 15- to 40-fold compared with Ag plus CpG ODN alone. These findings support the use of sterically stabilized cationic liposomes to significantly enhance the therapeutic efficacy of CpG ODN.