Selective induction of tumor-associated antigens in murine pulmonary vasculature using double-targeted adenoviral vectors

Abstract

Targeted therapies directed to tumor-associated antigens are being investigated for the treatment of cancer. However, there are few suitable animal models for testing the ability to target these tumor markers. Therefore, we have exploited mice transgenic for the human coxsackie and adenovirus receptor (hCAR) to establish a new model for transient expression of human tumor-associated antigens in the pulmonary vasculature. Systemic administration of Ad in hCAR mice resulted in an increase in transgene expression in the lungs compared to wild-type mice, as determined using a luciferase reporter gene. To reduce transgene expression in the liver, the predominant organ of ectopic Ad localization and transgene expression following systemic administration, we utilized the endothelial-specific flt-1 promoter, which resulted in a further increased lung-to-liver ratio of luciferase expression. Administration of an adenoviral vector encoding the tumor-associated antigen carcinoembryonic antigen (CEA) under transcriptional control of the flt-1 promoter resulted in selective expression of this antigen in the pulmonary vasculature of hCAR mice. Feasibility of targeting to expressed CEA was subsequently demonstrated using adenoviral vectors preincubated with a bifunctional adapter molecule recognizing this tumor-associated antigen, thus demonstrating utility of this transient transgenic animal model.

Directing adenovirus across the blood–brain barrier via melanotransferrin (P97) transcytosis pathway in an in vitro model

“…[14][15][16] Based on this information, investigators have utilized bispecific adaptor proteins that bind to both Ad5 vectors and alternative receptors expressed on the surface of the target cells to re-direct Ad5 tropism. [17][18][19] In our study, we attempted to re-direct Ad5 across the BBB using the bi-specific adaptor protein strategy. We constructed a bi-specific adaptor protein containing the extracellular domain of CAR (sCAR) and the full-length MTf, namely sCAR-MTf, and demonstrated its ability to re-direct Ad5 vectors across the BBB using an in vitro BBB model.…”

Targeting EGFR with metabolically biotinylated fiber-mosaic adenovirus

“…2 As systemically introduced vectors retargeted to tumors are to overcome multiple physiological barriers before reaching their targets, it has been proposed that the display of targeting molecules at accessible sites would facilitate testing of targeting gains of systemically administered adenoviral vectors. An hCAR-transgenic mouse model that is sensitized to Ad infection and is used to transiently express tumor antigens in the lung vasculature was recently reported to be efficient for evaluating vectors targeted to CD40 and carcinoembryonic antigen (CEA).…”

“…An hCAR-transgenic mouse model that is sensitized to Ad infection and is used to transiently express tumor antigens in the lung vasculature was recently reported to be efficient for evaluating vectors targeted to CD40 and carcinoembryonic antigen (CEA). 2,35 Thus, the hCAR mice were used to confirm whether our targeting strategy using the combination of two targeting modes in a single vector could efficiently target hEGFR expressed in the lungs. Expression of hEGFR was transiently induced in the mice pulmonary endothelium by systemic injection of recombinant adenovirus AdfltEGFR.…”

“…For that mice were injected via tail vein with 1 Â 10 11 vp of AdfltEGFR per animal. Transient expression of Ad transgene in lung endothelium under these conditions has been first demonstrated by Everts et al 2 Forty-eight hours after the first injection, each mouse was injected iv with 5 Â 10 10 vp of mBfMAd preincubated either with EGF-Streptavidin (100 ng) or PBS. All animals were killed 48 h after the last viral injection.…”

“…In adapter-mediated approaches, the tropism of the virus is modified by a targeting moiety utilizing a ligand, which associates with the Ad virion. Adapter molecules successfully used for Ad targeting include bispecific antibody (Ab) conjugates, 1 genetic fusions of single-chain Ab (scFv) with soluble CAR, 2 or scFv-scFv diabodies. 3 The combined use of two or more targeting components in single vector has also been reported to significantly enhance the utility of individual targeting approaches.…”