Hematopoietic remodeling triggered by CpG DNA

Changes in immune responses to antigen applied to tape-stripped skin with CpG-oligodeoxynucleotide in NC/Nga mice

PURPOSE

CpG-oligodeoxynucleotide (CpG-ODN) plays a critical role in immunity via the augmentation of Th1 and the suppression of Th2 responses. We examined here the effect of CpG-ODN on the immune response to an antigen applied to a tape-stripped skin of NC/Nga mouse, a human atopic dermatitis (AD) model, by evaluating the production of cytokines and immunoglobulin isotypes.

METHODS

Model antigen, ovalbumin (OVA), and CpG-ODN were applied on to the shaved skin. The penetration of OVA and CpG-ODN was evaluated using confocal laser scanning microscopy (CLSM). Secretion of cytokine from splenocytes and changes in immunoglobulin isotype levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Through CLSM it was revealed that the model antigen, OVA, and CpG-ODN easily penetrated the tape-stripped skin. Coadministration of CpG-ODN and OVA to the skin elicited an antigen-specific, Th1-predominant immune response and enhanced the production of IFN-gamma. On the other hand, the production of a Th2-type cytokine, IL-4, was drastically suppressed. In terms of antigen-specific antibody production, the level of IgG2a regulated by IFN-gamma was increased by CpG-ODN, but IgE production regulated by IL-4 was suppressed.

CONCLUSIONS

Administration of CpG-ODN with antigen through the skin may shift the immune response from a Th2- to Th1-like response. These results suggested that administration of CpG-ODN via skin is a simple strategy for patients with diseases such as AD, which is characterized by Th2-dominated inflammation.

Phosphodiester CpG oligonucleotides as adjuvants: polyguanosine runs enhance cellular uptake and improve immunostimulative activity of phosphodiester CpG oligonucleotides in vitro and in vivo

Bacterial DNA and oligonucleotides (ODN) containing CpG-motifs strongly activate cells of the immune system. Accordingly CpG-DNA is a powerful adjuvant in vaccination protocols for B-cell as well as for cytotoxic T-cell responses. A decisive propensity of CpG-DNA is its capacity to induce preferentially T helper type 1 (Th1)-dominated immune responses. To exert its function CpG-DNA has to be taken up by responsive cells, e.g. antigen-presenting cells (APC). The rate of uptake is influenced by the DNA's backbone modification and critically determines activity of CpG-DNA. CpG ODN with a phosphothioate backbone (PTO) are currently used for most in vivo and in vitro studies, since PTO modification protects ODN from the attack of nucleases. However, after administration of PTO-modified CpG-ODN long-lasting effects including lymphadenopathy as well as sustained local interferon-gamma (IFN-gamma) and interleukin-12 (IL-12) production have been reported. To circumvent these restrictions we investigated the effects of DNA sequence as well as DNA backbone modification on cellular uptake and resulting immunostimulation. We show here that uptake of phosphodiester (PO)-CpG-ODN can be strongly enhanced by poly guanosine runs added at the 3' end of the ODN. In addition these ODN showed an improved immunostimulatory activity in vivo and in vitro. This included protection of mice against lethal Th2-dependent leishmaniasis as well as priming of antigen specific Th1 responses. More importantly, guanosine-rich PO-CpG-ODN neither induced lymphadenopathy nor prolonged cytokine production after local administration. Since these improved PO ODN are efficient in vitro and in vivo and lack long lasting undesired effects they could be used preferably as adjuvants in vaccination protocols.