Electrochemical sensing of aptamer-facilitated virus immunoshielding

Oncolytic viruses (OVs) are promising therapeutics that selectively replicate in and kill tumor cells. However, repetitive administration of OVs provokes the generation of neutralizing antibodies (nAbs) that can diminish their anticancer effects. In this work, we selected DNA aptamers against an oncolytic virus, vesicular stomatitis virus (VSV), to protect it from nAbs. A label-free electrochemical aptasensor was used to evaluate the degree of protection (DoP). The aptasensor was fabricated by self-assembling a hybrid of a thiolated ssDNA primer and a VSV-specific aptamer. Electrochemical impedance spectroscopy was employed to quantitate VSV in the range of 800-2200 PFU and a detection limit of 600 PFU. The aptasensor was also utilized for evaluating binding affinities between VSV and aptamer pools/clones. An electrochemical displacement assay was performed in the presence of nAbs and DoP values were calculated for several VSV-aptamer pools/clones. A parallel flow cytometric analysis confirmed the electrochemical results. Finally, four VSV-specific aptamer clones, ZMYK-20, ZMYK-22, ZMYK-23, and ZMYK-28, showed the highest protective properties with dissociation constants of 17, 8, 20, and 13 nM, respectively. Another four sequences, ZMYK-1, -21, -25, and -29, exhibited high affinities to VSV without protecting it from nAbs and can be further utilized in sandwich assays. Thus, ZMYK-22, -23, and -28 have the potential to allow efficient delivery of VSV through the bloodstream without compromising the patient's immune system.