CHARACTERIZATION AND MODULATION OF IMMUNE STIMULATION BY MODIFIED OLIGONUCLEOTIDES

Single-stranded oligodeoxynucleotides (ODNs) were tested for their abi lity to stimulate NK cells isolated from murine spleens to lyse target cells, Various sequences were evaluated, some of which have been show n previously to exhibit pharmacologic activity in murine model systems , It was confirmed that the CpG motif was stimulatory only in specific sequence contexts, and we found that phosphorothioate backbones were, in general, less stimulatory than phosphodiester backbones, In additi on, this stimulation could be reduced by methylating the cytosine of t he CpG and eliminated by modifying all of the cytosines contained in a n ODN with methyl, bromo, or iodo modifications to the 5 position of t he cytosine ring, These results were compared with the ability of a su bset of these ODN sequences to stimulate B cell proliferation in vitro , In this comparison, phosphorothioate backbones were found to be requ ired, and the context of the CpG motif was found to be less critical f or activation, Finally, one of the most potent ODNs was shown to activ ate NK and B lymphocytes when administered in vivo.