Higher order G-quadruplex-based aptamers from tetra-end-linkedoligonucleotides with in vitro anti-HIV activity

Many synthetic oligodeoxynucleotides (ODNs) have been found to be potent antiviral agents (1) and several modified ODNs have been selected as promising drug candidates. Among the most studied viral targets is the glycoprotein 120 (gp120) exposed on the surface of HIV spikes. The interaction of gp120 with the CD4 glycoprotein and with a chemokine receptor on the surface of host cells represents the first event of HIV infection. This makes gp120 a suitable target for pharmacological intervention. Starting from the so-called Hotoda’s aptamer, having the ODN sequence TGGGAG, by exploiting the Tetra-End-Linker (TEL) strategy first proposed by us in 2004 (2,3) and by replacing some of the nucleobases in the aptamer DNA sequence (3,4), we produced a small library of TELODNs capable of protecting human CD4 CEM cell cultures from HIV infection at sub micromolar concentrations (EC50 values in the range 0.039–0.29 μM). The combined analysis of the docking results and biological assays indicated that the self-assembly of TEL-aptamers into the corresponding G-quadruplex structures was a requisite for their anti-HIV activity. Since there is a consensus that structuration into a higher-ordered quadruplex structure is required for the selective binding of many aptamers to their target, we have speculated that the application of the TEL strategy, which improves the thermodynamics parameters of quadruplex formation, to G-rich ODNs capable of forming higherordered G-quadruplex structures could provide more efficient and specific anti-HIV agents. The preliminary structural and biological results on the resulting study will be here discussed.