Targeted gene delivery by tropism-modified adenoviral vectors

Abstract

The utility of adenoviral vectors for gene therapy is currently limited due, in part, to the widespread distribution of the cellular receptor for the adenovirus fiber that precludes the targeting of specific cell types. In order to develop a targeted adenovirus, it is therefore necessary both to ablate endogenous viral tropism and to introduce novel tropism. We hypothesized that these two goals could be achieved by employing a neutralizing anti-fiber antibody, or antibody fragment, chemically conjugated to a cell-specific ligand. To test this concept, we chose to target the folate receptor, which is overexpressed on the surface of a variety of malignant cells. Therefore, we conjugated folate to the neutralizing Fab fragment of an anti-fiber monoclonal antibody. This Fab-folate conjugate was complexed with an adenoviral vector carrying the luciferase reporter gene and was shown to redirect adenoviral infection of target cells via the folate receptor at a high efficiency. Furthermore, when complexed with an adenoviral vector carrying the gene for herpes simplex virus thymidine kinase, the Fab-folate conjugate mediated the specific killing of cells that overexpress the folate receptor. This work thus represents the first demonstration of the retargeting of a recombinant adenoviral vector via a non-adenoviral cellular receptor.

Imaging and tissue biodistribution of 99mTc-labeled adenovirus knob (serotype 5)

“…27 Anti-Ad5K monoclonal antibody (1D6.14, IgG2a) was also modified with HYNIC. 5 The modified proteins were radiolabeled with 99m Tc using tricine as the transfer ligand and purified from nonbound 99m Tc by G-25 size exclusion chromatography. 28 Protein concentrations of the collected fractions were determined by the method of Lowry.…”

“…Therefore, a number of investigators are attempting to alter the tropism of the Ad vector to permit gene delivery to certain target cell types. [5][6][7][8][9][10] An understanding of the biological basis of the sequestration of Ad by the liver should yield strategies to avoid this occurrence. While this mechanism has not been investigated, a number of studies have elucidated the pathway of Ad cellular infection.…”

Transductional targeting of adenovirus vectors for gene therapy

“…50 This was accomplished using a bispecific conjugate consisting of an antiknob neutralizing Fab chemically linked to folate. A similar targeting adapter comprised of the same anti-knob Fab as above fused to a basic fibroblast growth factor (FGF2) was utilized to target Ad vectors to FGF receptor-positive Kaposi's sarcoma (KS) cells in vitro.…”

Evolving gene therapy approaches for osteosarcoma using viral vectors: Review

“…Upon division of the tumor cell, GCV-3P or ACV-3P is incorporated into the cellular DNA, thereby inhibiting DNA replication and RNA polymerase activity, eventually leading to cell death. The HSV-TK/GCV strategy has demonstrated strong anti-tumor activity in numerous tumor models including ovarian carcinoma, malignant glioma, hepatocellular carcinoma and prostate cancer (17,30,118,121,126,136). This system was first tested in OS by Grossin et al (15).…”

“…As noted above, studies on various types of tumors have shown that application of adenoviral vectors for cancer gene therapy is hampered by the lack of CAR expression on primary tumor cells (30,46,85,150). The recognition that CAR deficiency is a nearly universal feature of primary tumors has predicated the need for adenoviral vectors capable of CAR independent gene delivery.…”