CpG-containing immunostimulatory DNA sequences elicit TNF-α–dependent toxicity in rodents but not in humans

Abstract

CpG-containing immunostimulatory DNA sequences (ISS), which signal through TLR9, are being developed as a therapy for allergic indications and have proven to be safe and well tolerated in humans when administrated via the pulmonary route. In contrast, ISS inhalation has unexplained toxicity in rodents, which express TLR9 in monocyte/macrophage lineage cells as well as in plasmacytoid DCs (pDCs) and B cells, the principal TLR9-expressing cells in humans. We therefore investigated the mechanisms underlying this rodent-specific toxicity and its implications for humans. Mice responded to intranasally administered 1018 ISS, a representative B class ISS, with strictly TLR9-dependent toxicity, including lung inflammation and weight loss, that was fully reversible and pDC and B cell independent. Knockout mouse experiments demonstrated that ISSinduced toxicity was critically dependent on TNF-α, with IFN-α required for TNF-α induction. In contrast, human PBMCs, human alveolar macrophages, and airway-derived cells from Ascaris suum-allergic cynomolgus monkeys did not produce appreciable TNF-α in vitro in response to ISS stimulation. Moreover, sputum of allergic humans exposed to inhaled ISS demonstrated induction of IFN-inducible genes but minimal TNF-α induction. These data demonstrate that ISS induce rodent-specific TNF-α-dependent toxicity that is absent in humans and reflective of differential TLR9 expression patterns in rodents versus humans.

Oxidative modification enhances the immunostimulatory effects of extracellular mitochondrial DNA on plasmacytoid dendritic cells

“…It is important to note that while flow cytometric analysis provides unambiguous data about the pDCs' phenotypic changes, the detected cytokines and chemokine could be released by diverse cell types responding to mtDNA treatment. In humans, TLR9 expression in mononuclear blood cells and lymphoid tissues is restricted to B cells and pDCs, whereas in mice, TLR9 expression has also been demonstrated in macrophages, myeloid DCs, and activated T cells in addition to pDCs and B cells [52]. Despite this fact, the results of our in vivo experiments correlate very well with those of cell culture assays.…”

Anti‐tumor activity of CpG‐ODN aerosol in mouse lung metastases

“…or i.t. [27][28][29] The anti-tumor activity of aerosol-delivered CpG-ODN was evaluated in two murine tumor models with different characteristics and behavior: the mammary carcinoma N202.1A is highly immunogenic due to overexpression of the heterologous rat neu oncogene, 25 while the B16 melanoma is poorly immunogenic and reportedly expresses very low levels of MHC I molecules. 42 These two tumors also differ in their sensitivity to immune effectors, with the neu-expressing mouse mammary tumor sensitive to cytotoxic activity of T but not NK cells, 43 while NK cells are required to counteract the growth of B16 melanomas.…”

“…Unlike i.n.-administered CpG-ODN, which induces lung tissue inflammation associated with weight loss in rodents, [27][28][29] prolonged repeated treatments at intervals of 72-96 hr with 1.5 mg CpG-ODN aerosol for 3 weeks were well tolerated. No effects on body weight and no histological changes in the structure of lungs, as indicated by histopathological examination of hematoxylin and eosin-stained sections of lung tissue, were observed in mice exposed to CpG-ODN aerosolization (data not shown).…”

Targeting ST2L Potentiates CpG-Mediated Therapeutic Effects in a Chronic Fungal Asthma Model

“…8 CpG given in this manner has caused tumor necrosis factor-␣-dependent toxicity in rodents. 53 In the present study, CpG therapy was optimized (ie, systemic administration of a nontoxic dose of 5 g) with the addition of subtherapeutic amounts of anti-ST2L mAb. All features of allergic asthma were markedly attenuated by this combination therapeutic approach, and prominent induction of IL-12p70 and MIG/CXCL9 was observed in whole lung and isolated asthmatic DCs.…”