Manipulating the in vivo immune response by targeted gene knockdown

•Short structured nucleic acids called aptamers can be used like antibodies.•Aptamers can be synthesized and are nonimmunogenic.•Aptamers linked to siRNAs, proteins, other aptamers or toxins can be multifunctional.•Aptamers can cause cell or location-specific receptor activation or inhibition.•Aptamer-siRNAs can be used for targeted gene knockdown.

Aptamers, nucleic acids selected for high affinity binding to proteins, can be used to activate or antagonize immune mediators or receptors in a location and cell-type specific manner and to enhance antigen presentation. They can also be linked to other molecules (other aptamers, siRNAs or miRNAs, proteins, toxins) to produce multifunctional compounds for targeted immune modulation in vivo. Aptamer-siRNA chimeras (AsiCs) that induce efficient cell-specific knockdown in immune cells in vitro and in vivo can be used as an immunological research tool or potentially as an immunomodulating therapeutic.