THE INFLUENCE OF BASE SEQUENCE ON THE IMMUNOLOGICAL PROPERTIES OF DEFINED OLIGONUCLEOTIDES

To assess the influence of base sequence on the immunostimulatory acti vities of DNA, cell binding and mitogenicity of a series of 30-mer pho sphodiester oligonucleotides were tested using murine spleen cells. Th ese compounds consisted of either; a single base or a six base CpG mot if in the context of 5' and 3' flanking sequences of each base. Among fluoresceinated oligonucleotides, (dG)30 had the highest binding of si ngle base compounds tested while the presence of dG flanks increased b inding of compounds with six base motifs, whether active on inactive. In assays of mitogenesis including incorporation of thymidine and urid ine as well as expression of cell surface CD69, (dG)30 induced the hig hest responses among single base compounds. Among compounds with an ac tive six base motif, the extent of proliferation varied with flanking sequence, with dG flanks producing the greatest stimulation in all ass ays tested. Together, these findings indicate that a variety of base s equences may affect the immunomodulatory properties of DNA, with the a ctivity of dG sequences perhaps resulting from the formation of varian t DNA structures. (C) 1998 Elsevier Science B.V. All rights reserved.