title: Overexpression of indoleamine dioxygenase in rat liver allografts using a high-efficiency adeno-associated virus vector does not prevent acute rejection.
abstract: The aim of this study was to evaluate the ability of local overexpression of indoleamine dioxygenase (IDO) to abrogate rat liver transplant rejection by the use of an adeno-associated virus vector [recombinant adeno-associated virus 2/8 (rAAV2/8)] to deliver the transgene to the allograft prior to transplantation. A green fluorescent protein (GFP)-expressing vector [recombinant adeno-associated virus 2/8-liver-specific promoter 1-enhanced green fluorescent protein (rAAV2/8-LSP1-eGFP)] was used to examine the kinetics of expression and optimal dosing for transduction of Piebald Virol Glaxo (PVG) rat livers. A vector encoding the rat IDO gene (rAAV2/8-LSP1-rIDO) was constructed and tested by its ability to induce tryptophan catabolism and kynurenine production in vitro and in vivo. PVG donor rats were injected, via the portal vein, with rAAV2/8-LSP1-rIDO 2 weeks before transplantation into PVG strain isograft or Lewis (LEW) strain allograft recipients. With the enhanced GFP vector, 29.5% and 47.4% of hepatocytes were found to express GFP at 3 and 6 weeks after injection, respectively. In untransplanted PVG animals, the rAAV2/8-LSP1-rIDO vector induced, 3 weeks after administration, a 1.8-fold increase (P = 0.0161) in liver IDO activity, which was associated with a fall in serum tryptophan to 0.5 times the baseline level (P < 0.001). PVG recipients of PVG liver isografts pretreated with the IDO-expressing vector had a 45% lower level of serum tryptophan than recipients of isografts pretreated with the GFP-expressing vector (P = 0.03). LEW recipients of PVG liver allografts pretreated with the rat IDO vector had a median survival time of 12 days, whereas recipients of allografts pretreated with rAAV2/8-LSP1-eGFP had a median survival time of 13 days (P = 0.38). Both groups displayed similar histological features of acute cellular rejection. In conclusion, rAAV2/8 vectors produce highly efficient, though delayed, hepatocyte transduction in vivo and provide a useful gene delivery tool for transplantation models. However, gene delivery using IDO was unsuccessful in prolonging rat liver allograft survival.
authors.affiliation: Collaborative Transplantation Research Group, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia.
authors.forename: Jerome M
authors.initials: JM
authors.lastname: Laurence
authors.forename: Chuanmin
authors.initials: C
authors.lastname: Wang
authors.forename: Maolin
authors.initials: M
authors.lastname: Zheng
authors.forename: Sharon
authors.initials: S
authors.lastname: Cunningham
authors.forename: John
authors.initials: J
authors.lastname: Earl
authors.forename: Szun Szun
authors.initials: SS
authors.lastname: Tay
authors.forename: Richard D M
authors.initials: RD
authors.lastname: Allen
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: McCaughan
authors.forename: Ian E
authors.initials: IE
authors.lastname: Alexander
authors.forename: G Alex
authors.initials: GA
authors.lastname: Bishop
authors.forename: Alexandra F
authors.initials: AF
authors.lastname: Sharland
mesh_terms: D000818:Animals; D000229:Dependovirus / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors / Q000235:genetics; D006084:Graft Rejection / Q000201:enzymology / Q000235:genetics / Q000517:prevention & control*; D006085:Graft Survival / Q000235:genetics; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000096:biosynthesis* / Q000235:genetics*; D016031:Liver Transplantation / Q000009:adverse effects*; D051381:Rats; D014184:Transplantation, Homologous; D015854:Up-Regulation
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase