Engineered lentiviral vectors pseudotyped with a CD4 receptor and a fusogenic protein can target cells expressing HIV-1 envelope proteins

Abstract

Lentiviral vectors (LVs) derived from human immunodeficiency virus type 1 (HIV-1) are promising vehicles for gene delivery because they not only efficiently transduce both dividing and non-dividing cells, but also maintain long-term transgene expression. Development of an LV system capable of transducing cells in a cell type-specific manner can be beneficial for certain applications that rely on targeted gene delivery. Previously it was shown that an inverse fusion strategy that incorporated an HIV-1 receptor (CD4) and its co-receptor (CXCR4 or CCR5) onto vector surfaces could confer to LVs the ability to selectively deliver genes to HIV-1 envelope-expressing cells. To build upon this work, we aim to improve its relatively low transduction efficiency and circumvent its inability to target multiple tropisms of HIV-1 by a single vector. We investigated a method to create LVs co-enveloped with the HIV-1 cellular receptor CD4 and a fusogenic protein derived from the Sindbis virus glycoprotein and tested its efficiency to selectively deliver genes into cells expressing HIV-1 envelope proteins. The engineered LV system yields a higher level of transduction efficiency and a broader tropism towards cells displaying the HIV-1 envelope protein (Env) than the previously developed system. Furthermore, we demonstrated in vitro that this engineered LV can preferentially deliver suicide gene therapy to HIV-1 envelope-expressing cells. We conclude that it is potentially feasible to target LVs towards HIV-1-infected cells by functional co-incorporation of the CD4 and fusogenic proteins, and provide preliminary evidence for further investigation on a potential alternative treatment for eradicating HIV-1-infected cells that produce drug-resistant viruses after highly active antiretroviral therapy (HAART).

Conditional Cytotoxic Anti-HIV Gene Therapy for Selectable Cell Modification

“…Several HIV LTR-based Tat-and Rev-dependent lentiviral vectors have been developed by numerous groups. 8,10,24,36,42 Another important aspect of using conditional vectors is that the anti-HIV gene needs to target late stages of the virus, as Tatmediated activation in infected cells would not prevent early steps in the HIV life cycle. In this regard, we have previously described the use of viral dominant-negative proteins that target the late stages of HIV life cycle.…”

“…Several suicidal gene therapy approaches have been tried in the past for eliminating HIV-infected cells. [19][20][21][22][23][24] However, the approach has not been widely accepted because of the major limitation of lack of specificity required to target only HIV-infected cells and the modest efficacy of the suicide gene. In this regard, a point mutant of the herpes simplex virus (HSV)-1 thymidine kinase gene, TK-SR39, 25 has been shown to have severalfold higher activity than its wild-type counterpart (TK-WT) and has been tested in cancer gene therapy settings.…”

HIV-1 CCR5 gene therapy will fail unless it is combined with a suicide gene

“…Different suicide genes (e.g., HSV1-TK and iCasp9) are known to cause cell death when expressed at high concentration 18 . HIV-1 infected cells can be killed in a specific manner if a suicide gene (HSV1-TK or iCasp9) is successfully incorporated with the HIV-1 promoter and transactivation response element sequences 18 19 20 . Our models show that the therapeutic effect of targeting viral entry is markedly increased when the infected modified T cells undergo rapid cell death when they are infected.…”

A Lentiviral Gene Therapy Strategy for the In Vitro Production of Feline Erythropoietin

“…Selection of certain viral envelope glycoproteins or other proteins facilitates cell targeting to enhance directed gene transfer [21] . For example, cell-specific targeting has been achieved through the use of lentiviral vectors pseudotyped with the Rabies virus glycoprotein [38] or the CD4 receptor [39] . A variety of envelope-like genes are currently available to provide vector-target cell specificity [21] .…”