Polyinosinic acid enhances delivery of adenovirus vectors in vivo by preventing sequestration in liver macrophages

Abstract

Adenovirus is among the preferred vectors for gene therapy because of its superior in vivo gene-transfer efficiency. However, upon systemic administration, adenovirus is preferentially sequestered by the liver, resulting in reduced adenovirus-mediated transgene expression in targeted tissues. In the liver, Kupffer cells are responsible for adenovirus degradation and contribute to the inflammatory response. As scavenger receptors present on Kupffer cells are responsible for the elimination of blood-borne pathogens, we investigated the possible implication of these receptors in the clearance of the adenovirus vector. Polyinosinic acid [poly(I)], a scavenger receptor A ligand, was analysed for its capability to inhibit adenovirus uptake specifically in macrophages. In in vitro studies, the addition of poly(I) before virus infection resulted in a specific inhibition of adenovirus-induced gene expression in a J774 macrophage cell line and in primary Kupffer cells. In in vivo experiments, pre-administration of poly(I) caused a 10-fold transient increase in the number of adenovirus particles circulating in the blood. As a consequence, transgene expression levels measured in different tissues were enhanced (by 5- to 15-fold) compared with those in animals that did not receive poly(I). Finally, necrosis of Kupffer cells, which normally occurs as a consequence of systemic adenovirus administration, was prevented by the use of poly(I). No toxicity, as measured by liver-enzyme levels, was observed after poly(I) treatment. From our data, we conclude that poly(I) can prevent adenovirus sequestration by liver macrophages. These results imply that, by inhibiting adenovirus uptake by Kupffer cells, it is possible to reduce the dose of the viral vector to diminish the liver-toxicity effect and to improve the level of transgene expression in target tissues. In systemic gene-therapy applications, this will have great impact on the development of targeted adenoviral vectors.

Clearance of Adenovirus by Kupffer Cells Is Mediated by Scavenger Receptors, Natural Antibodies, and Complement

“…SRs have been shown to be responsible for the clearance of various ligands in vivo, including DNA, damaged erythrocytes, and endotoxin (18,25,27,57,62). Recently, the SR inhibitor poly(I) was shown by us and others to reduce the clearance of Ad in vivo (17,47). In the current study, we systematically surveyed how KC clearance of Ad is affected by various additional polyanionic SR ligands.…”

“…They deleted a 13-residue stretch of acidic residues from the Ad5 hexon to reduce the negative charge of the capsid, but this had no effect on the rate of Ad clearance from the circulation, possibly because the overall charge of the capsid was still negative (2). Recently we found that a polyribonucleotide, poly(I), decreases the KC uptake of Ad in vivo (47), and Haisma et al showed that poly(I) reduces the transduction of macrophages by Ad in vitro, slows the clearance of Ad from the circulation, and enhances the ability of Ad to transduce hepatocytes in vivo (17). In addition, Haisma et al recently reported that the expression of a class A SR enhances the susceptibility of CHO cells to transduction by Ad vector (16).…”

“…We and others recently showed that preinjecting mice with poly(I) can greatly reduce KC uptake and increase the circulating half-life of Ad in vivo (17,47). Because poly(I) is a ligand for scavenger receptors (SRs), we wanted to further explore the involvement of SRs in vivo.…”

Macrophage receptor SR-AI is crucial to maintain normal plasma levels of coagulation factor X

“…First, acetylated low-density lipoprotein (Ac-LDL; a natural ligand) failed to compete with FX (1 mg/mL) at concentrations up to 50 mg/mL, suggesting that both proteins bind to distinct regions within SR-AI. However, efficient dose-dependent inhibition was observed for polyinosinic acid (a polyanionic compound known to interact with SR-AI 19 ) or polyclonal SR-AI-inhibiting antibodies (50% inhibitory concentration 5 2.4 6 0.1 mg/mL and 2.9 6 0.2 mg/mL, respectively; Figure 3B). Polyinosinic acid also inhibited this interaction dosedependently when tested at higher FX concentrations (5 mg/mL; supplemental Figure 2A).…”

The Role of Liver Sinusoidal Cells in Hepatocyte-Directed Gene Transfer

“…Besides clodronate liposomes, preadministration of polyinosinic acid, a scavenger receptor A ligand, before gene transfer has been shown to prevent sequestration of adenoviral vectors in Kupffer cells and to enhance parenchymal liver cell transduction. 42 Transient saturation of the reticuloendothelial system with phosphatidylcholine liposomes or with Intralipid also reduces uptake of vectors in the nonparenchymal liver cells and augments hepatocyte transduction. 34 Taken together, various interventions that result in reduced uptake of adenoviral vectors in liver reticulo-endothelial cells consistently enhance hepatocyte transduction.…”