Modulation of immunostimulatory activity of CpG oligonucleotides by site-specific deletion of nucleobases

The effect of nucleobase deletion in the 3 '- or the 5 ' -flanking sequence to a CpG-motif on immunostimulatory activity of CpG-containing oligonucleo tides was examined by cell proliferation, secretion of IL-12 and IL-6 in mo use spleen cell cultures, and by spleen enlargement in mice. Deletion of on e or two nucleobases in the 3 ' -flanking sequence to a CpG-motif at certai n positions did not affect immunostimulatory activity, while similar deleti ons in the 5 ' -flanking sequence increased immunostimulatory activity comp ared with the parent oligo. (C) 2001 Elsevier Science Ltd. All rights reser ved.