A Sense Phosphorothioate Oligonucleotide Directed to the Initiation Codon of Transcription Factor NF-κ-B Causes Sequence-Specific Immune Stimulation

Antisense oligonucleotides have proved effective in achieving targeted inhibition of gene expression. In such experiments, sense oligonucleotides have frequently been used as a control for nonspecific effects, but the results have been variable, raising questions about the reliability of sense oligomers as a control. It is possible that some of the effects of sense oligonucleotides may be specific. We have shown that phosphorothioate antisense oligonucleotides to the p65 subunit of NF-κB, a transcription factor, cause a block in cell adhesion. In our efforts to test the efficacy of NF-κB p65 oligonucleotides in vivo, we unexpectedly observed that the control p65-sense, but not the p65-antisense, oligonucleotides caused massive splenomegaly in mice. In the current study we demonstrate a sequence-specific stimulation of splenic cell proliferation, both in vivo and in vitro, by treatment with p65-sense oligonucleotides. Cells expanded by this treatment are primarily B-220⁺, sIg⁺ B cells. The secretion of immunoglobulins by the p65-sense oligonucleotide-treated splenocytes is also enhanced. In addition, the p65-sense-treated splenocytes, but not several other cell lines, showed an upregulation of NF-κB-like activity in the nuclear extracts, an effect not dependent on new protein or RNA synthesis. These results demonstrate that phosphorothioate oligonucleotides can exert sequence-specific effects in vivo, irrespective of sense or antisense orientation.