Selective Evolution of Ligands by Exponential Enrichment to Identify RNA Aptamers against Shiga Toxins

Figure 4

Neutralization of Stx2 activity by aptamers (1550 pmoles) in HeLa cell cytotoxicity Assay. Stx2-specific HuMAb 5H8 (6.66 pmole) strongly neutralized Stx2 activity at both toxin concentrations (0.007 pmole and 0.056 pmole). A limited neutralization of Stx2 activity was observed with aptamers mA_Apt1 (~40% cell survival), mB_Apt23 (~20% cell survival), and pC_Apt22 (≤60% cell survival). Aptamer mC_Apt41 neutralized 0.007 pmole of Stx2 (≤60% cell survival) but not 0.056 pmole of Stx2. None of the other aptamers neutralized the cytotoxic effects of Stx2. This experiment was repeated twice with similar results.