2'-Fluoro-Pyrimidine-Modified RNA Aptamers Specific for Lipopolysaccharide Binding Protein (LBP)

Lipopolysaccaride binding protein (LBP), a glycosylated acute phase protein, plays an important role in the pathophysiology of sepsis. LBP binds with high affinity to the lipid part of bacterial lipopolysaccaride (LPS). Inhibition of the LPS-LBP interaction or blockage of LBP-mediated transfer of LPS monomers to CD14 may be therapeutical strategies to prevent septic shock. LBP is also of interest as a biomarker to identify septic patients at high risk for death, as LBP levels are elevated during early stages of severe sepsis. As a first step toward such potential applications, we isolated aptamers specific for murine LBP (mLBP) by in vitro selection from a library containing a 60-nucleotide randomized region. Modified RNA pools were transcribed in the presence of 2'-fluoro-modified pyrimidine nucleotides to stabilize transcripts against nuclease degradation. As verified for one aptamer experimentally, the selected aptamers adopt a "three-helix junction" architecture, presenting single-stranded 7-nt (5'-YGCTTCY) or 6-nt (5'-RTTTCY) consensus sequences in their core. The best binder (aptamer A011; Kd of 270 nM for binding to mLBP), characterized in more detail by structure probing and boundary analysis, was demonstrated to bind with high specificity to murine LBP.