Key result
Fusion of a single-domain antibody to Adenovirus capsid protein IX resulted in efficient incorporation into the capsid and enhanced infection of cells expressing the targeted receptor, whereas single-chain antibodies failed to retarget the virus.
Capsid protein IX is an effective platform for presenting single-domain antibodies on the adenovirus surface to enhance targeted cell infection for potential gene therapy applications.
Supports protein IX for single-domain antibody display on adenovirus; leaves open in vivo validation for gene therapy.
Adenovirus (Ad) vectors are the most commonly used system for gene therapy applications, due in part to their ability to infect a wide array of cell types and tissues. However, many therapies would benefit from the ability to target the Ad vector only to specific cells, such as tumor cells for cancer gene therapy. In this study, we investigated the utility of capsid protein IX (pIX) as a platform for the presentation of single-chain variable-fragment antibodies (scFv) and single-domain antibodies (sdAb) for virus retargeting. We show that scFv can be displayed on the capsid through genetic fusion to native pIX but that these molecules fail to retarget the virus, due to improper folding of the scFv. Redirecting expression of the fusion protein to the endoplasmic reticulum (ER) results in correct folding of the scFv and allows it to recognize its epitope; however, ER-targeted pIX-scFv was incorporated into the Ad capsid at a very low level which was not sufficient to retarget virus infection. In contrast, a pIX-sdAb construct was efficiently incorporated into the Ad capsid and enhanced virus infection of cells expressing the targeted receptor. Taken together, our data indicate that pIX is an effective platform for presentation of large targeting polypeptides on the surface of the virus capsid, but the nature of the ligand can significantly affect its association with virions.
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Poulin et al. (2010) studied Gene therapy vector retargeting. Genetic fusion of scFv or sdAb to Adenovirus capsid protein IX vs. Unmodified Adenovirus vectors was evaluated on Virus retargeting and infection of cells expressing targeted receptor. Fusion of a single-domain antibody to Adenovirus capsid protein IX resulted in efficient incorporation into the capsid and enhanced infection of cells expressing the targeted receptor, whereas single-chain antibodies failed to retarget the virus.
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