Gene therapy using SV40-derived vectors: What does the future hold?

Abstract

Effective genetic therapy requires both a fragment of genetic material to be used therapeutically and a means to deliver it. We began to study simian virus-40 (SV40) as a vector for gene transfer because available gene delivery vehicles did not provide for the full range of therapeutic uses. Other vectors are variably limited by immunogenicity, difficulties in production, restricted specificity, low titers, poor transduction efficiency, etc. In theory recombinant viral vectors based on SV40 (rSV40) should not, on the other hand, be similarly constrained. rSV40 vectors are easily manipulated and produced at very high titer, stable, lacking in immunogenicity, and capable of providing sustained high levels of transgene expression in both resting and dividing cells. The principle limitation of SV40-derived vectors is the size of the packageable insert (</=5 kb). The rationale for developing SV40 as a gene therapy vector is reviewed. Our studies with rSV40 gene transfer have focused mostly on hematopoietic progenitor cells (CD34+) and their derivatives, and on gene delivery to the liver. In both settings, in vitro and in vivo, SV40 has proven to be very effective. It is thus a promising gene delivery vehicle that can complement others currently in use or under development.

SV40-derived vectors provide effective transgene expression and inhibition of HIV-1 using constitutive, conditional,and pol III promoters

“…2 We and others have observed high efficiency rSV40 transduction of unstimulated PBMC ex vivo, 1,24 and of hepatocytes, neurons and other non-cycling cells in vivo. 1,2,18,[26][27][28] In the current studies, Ͼ95% of SupT1 cells were transduced.…”

“…28 This plasmid consists of the SV40 genome, carrying a cytomegalovirus intermediate-early promoter (CMV-IEP) plus a polylinker immediately downstream of the SV40 early promoter (SV40-EP), in place of the Tag gene. The viral genome had been cloned as a PmeI fragment into an engineered PmeI site in a modified pT7blue (Novagen) plasmid.…”

Exploiting hepatitis C virus activation of NFκB to deliver HCV-responsive expression of interferons α and γ

“…rSV40 vectors were made by cloning the transgene of interest (7specific promoter) into a plasmid-carried modified SV40 genome. 52,53 The production of SV[wtHIVLTR](IFNa) has been reported in the context of inhibition of HIV replication in lymphocytes. 9 The other SV[HIVLTR](IFN) constructs were made similarly.…”

HIV-1 proprotein processing as a target for gene therapy

“…[24][25][26] Furthermore, rSV40s do not elicit cellular or humoral immune responses in animals. 27 The fact that a 1 AT occurs naturally in human blood makes immune responses against a 1 AT highly unlikely. The ultimate test for this inhibitor will be its transfer in CD34+ hematopoietic, to allow continuous repopulation of a patient's immune system with such genetically altered cells.…”

“…[24][25][26] rSV40 vectors can be concentrated to high titer (410 12 infectious units (IU)/ml), stably integrate into the host genome, do not require helper viruses, and do not elicit cellular or humoral responses in animals. 27 We delivered native human a 1 AT, a protease inhibitor, to human lymphocyte cell lines and primary human lymphocyte cultures using an rSV40-based vector (SV(AT)). We demonstrate that SV(AT) strongly inhibits replication and spread of HIV-1 by blocking two necessary steps in HIV-1 proprotein processing: it blocks cellular serine proteases that are involved in processing of gp160 to gp120 and gp41, and, surprisingly, it also decreases the activity of HIV-1 PR, an aspartyl protease that cleaves p55 Gag within the budding viral particles.…”